CORNER ADAPTING MOTORCYCLE HEADLIGHT

MIM 1501-1502

Technical Design Report

Corner Adapting Motorcycle Headlight

Final Report

Design Advisor: Professor S. Muftu

Design Team

Anthony Fry, Joseph Hager

James Kershaw, Michael Olasin

Matthew Reeves

May 29, 2002

Department of Mechanical, Industrial and Manufacturing Engineering College of Engineering, Northeastern University Boston, MA 02115

CORNER ADAPTING MOTORCYCLE HEADLIGHT

Design Team Anthony Fry, Joseph Hager James Kershaw, Michael Olasin Matthew Reeves

Design Advisor Sinan Muftu

Abstract

The purpose of this project is to improve motorcycle lighting in corners. Given that motorcycles need to lean or bank to turn, the headlight aim becomes obscured and inadequate around curves. This lighting phenomenon can present a safety hazard to riders at night. Although this problem has been present since headlights were first put on motorcycles, it is now prudent to accept the challenge of correcting this problem thanks to the recent advances in sensor and microprocessor design. The solution was to design a headlight control system that sensed the motorcycle’s dynamic behavior, predicted the current situation on a roadway, and manipulated the aim of the headlight to best illuminate the roadway. The system senses the bank angle and speed of a motorcycle, and then uses that data to manipulate a small projector beam headlight. The result of the project is a light that reacts to the banking of a motorcycle and corrects the beam aim quickly and accurately along two axes. In this project a working prototype was constructed. This prototype will be used to demonstrate and prove the concept with the intention of marketing the technology to motorcycle manufacturers.

TABLE OF CONTENTS

Acknowledgements 1

Copyright 2

1.0 Introduction 3

2.0 Project Goals 3

3.0 Need for Technology 4

4.0 Background Information 4 4.1 Dynamics 4 4.2 Light Geometry 7 4.3 Corner Geometry 9 4.4 Correction 11

5.0 Prior State of the Art 12

6.0 Prototype Design 18 6.1 System Overview 18 6.2 Electrical Design 20 6.2.1 Speed Detection 21 6.2.2 Angular Detection 21 6.2.3 Electronic Components 22 6.2.4 Operation 23 6.2.5 Algorithm 23

7.0 Mechanical Component Description 27 7.1 Carriage 30 7.2 Shafts 32 7.3 Bearings 35 7.4 Servos 36 7.5 Pulleys & Drive Belt 38 7.6 Gears 39 7.7 Headlight 40 7.8 Demo-Stand 42

8.0 Cost 42

9.0 Conclusion 43

10.0 Evaluation of Working Experiences 44 10.1 Electrical Computer Engineering Group 44 10.2 Business Group 45

11.0 References 47

Appendices 49

LIST OF FIGURES

Figure 4-1 Free Body Diagram of a motorcycle in a steady state turn 5 Figure 4-2 3-Dimensional Projection of Low Beam 7 Figure 4-3 Cornering Beam Scenarios 8 Figure 4-4 Cornering Geometry 9 Figure 4-5 Motorcycle Speed vs. Bank Angle vs. Illumination Angle 10 Figure 4-6 Proposed Correction Scenario 11 Figure 4-7 Two Axes of Rotation 12 Figure 5-1a Mercury Sensor (Static) 13 Figure 5-1b Mercury Sensor (Dynamic) 14 Figure 5-2 Inertial Mass Switch 15 Figure 5-3 Counter-Steer Diagram 15 Figure 5-4 Reflector Sensors 16 Figure 5-5 Supplementary Lights 17 Figure 6-1 Control Systems and Block Diagram 19 Figure 6-2 Rotation Axes 20 Figure 6-3 Process Block Diagram 26 Figure 7-1 Headlight Assembly 28 Figure 7-2 Exploded Headlight Assembly 28 Figure 7-3 Headlight Size Relationship 29 Figure 7-4 Model Analysis of Assembly 30 Figure 7-5a Carriage Model 30 Figure 7-5b Carriage Prototype (minus trusses) 30 Figure 7-6 Cradle Superposition Model 31 Figure 7-7a FEA Analysis of Carriage 32 Figure 7-7b FEA Analysis of Carriage without trusses 32 Figure 7-8 Shafts 33 Figure 7-9 Bank Shaft Superposition Model 34 Figure 7-10 FEA Analysis of Shaft 35 Figure 7-11a Bearing 36 Figure 7-11b Bearing Block 36 Figure 7-12 Servo 37 Figure 7-13 Pulleys and Drive Belt 39 Figure 7-14 Gears 39 Figure 7-15a Xenon Headlight 40 Figure 7-15b Halogen Headlight 40 Figure 7-16a Reflector Headlight 42 Figure 7-16b Projector Beam Headlight 42 Figure 8-1 Prototype Cost 43

Acknowledgements

We would like to acknowledge the electrical and computer engineering capstone design team members for their hard work and contribution to the project. Matthew Caparso, Anthony Pino, Melissa Patterson, John Fernandez

We would like to give a special thanks to our faculty project advisor Professor Sinan Muftu for his guidance and direction throughout the term.

Copyright

“We the team members, Anthony Fry Joseph Hager James Kershaw Michael Olasin Matthew Reeves

Prof. Sinan Muftu

Hereby assign our copyright of this report and of the corresponding Executive Summary to the Mechanical, Industrial and Manufacturing Engineering (MIME) Department of Northeastern University. We also hereby agree that the video of our Oral Presentations is the full property of the MIME Department.”

Publication of this report does not constitute approval by Northeastern University, the MIME Department or its faculty members of the findings or conclusions contained herein. It is published for the exchange and stimulation of ideas.

1.0 INTRODUCTION Motorcycle headlights are designed to conform to safety standards when the motorcycle is traveling straight and upright. When the motorcycle is cornering at speed and leaned over, the light is no longer pointing where it is needed at the end of the turn. The headlight shines at the same angle the motorcycle is leaned over at – sometimes approaching 50° from horizon. Because of the geometry of the headlight beam-pattern, the light actually appears to move away from the intended path. This is a serious problem and can obscure the rider’s view at night causing a hazardous situation. The solution to this problem is clear. Design and construct a corner adapting motorcycle headlight that will correct for lean angle of the motorcycle while aiming the headlight to the optimum location on the road. The project will reflect the efforts of both a Mechanical, Industrial and Manufacturing Engineering (MIME) capstone team and an Electrical and Computer Engineering (ECE) capstone team. The MIME team will concentrate on the dynamic modeling of the motorcycle and the mechanics of manipulating a headlight. The ECE team will focus on design and fabrication of the control system. Both groups will work to develop an algorithm for the control circuit. There are several design challenges and goals that must be satisfied. The components required to develop this technology are cutting-edge and will yield a highly accurate and feasible headlight control system. It is a goal of this project to create an innovative but practical technology available for implementation into the design of new motorcycles.

2.0 PROJECT GOALS The goal of the project was to increase a rider’s safety while cornering a motorcycle at night. To meet this goal the objective was to design and construct a corner adapting motorcycle headlight that corrects for the lean angle of the motorcycle and aims the headlight to the optimal location on the road. The final design is used as proof of concept to demonstrate the technology feasibility. The headlight and control system were incorporated into a demo-stand that allows for bench testing and presentation. The prototype shall be a realistic, practical and reliable improvement to current lighting designs. Also, the design should ultimately meet federal vehicle safety specs for vibration resistance, sealing, temperature, corrosion, abrasion and photometry. The prototype shall be able to withstand the relatively harsh environment of a motorcycle fairing.

3.0 NEED FOR TECHNOLOGY The need for a corner adapting motorcycle headlight can be established most easily by considering some recent motorcycle crash statistics. The statistics are generated and published by the National Highway Traffic Safety Administration (NHTSA). The specific statistics discussed were obtained from the NHTSA website, report # DOT HS 809 360, [22] dated October 2001. They were compiled from fatalities due to single vehicle motorcycle accident reports in the United States during the last ten years. Single vehicle motorcycle accidents are those accidents involving the victim’s motorcycle only, i.e. no other motor vehicles of any kind. In 1999, motorcycles accounted for only 2% of all registered vehicles in the United States, yet motorcycle accidents accounted for 5.5% of all motor vehicle fatalities. It is evident that more safety provisions be implemented to reduce motorcycle fatalities. First and foremost, in 1999, 58% of all motorcycle accidents resulting in a fatality occurred during nighttime hours. Nighttime refers to the period between the hours of 6:00 pm and 5:59 am. This is important because it is the time in which the rider relies most on their headlight. If a headlight is inadequate it can inadvertently cause an accident by not allowing the rider enough time to react to an obstacle or threat in their path. It was also found that in 1999, 57% of all fatalities occurred on rural roadways. Due to the lack of streetlights, rural roads are much darker than urban areas and can also decrease a rider’s vision causing an unsafe situation. Lastly, negotiating a curve is a seemingly simple and common maneuver, however it proved to be the most dangerous vehicle maneuver by a large margin. In 1999, 50% of all accidents resulting in a fatality transpired while the rider was negotiating a curve. These statistics illustrate a few select issues that can cause unsafe conditions while riding. It is important to study these statistics to understand the possible causes of these fatalities because they account for 46% of the total number of fatalities from all motorcycle accidents. The analyses conducted by the NHTSA are done for the purpose of developing crash prevention programs and providing information to motorcycle manufacturers. Manufacturers use the information to focus their efforts on areas that may need safety improvements.

4.0 BACKGROUND INFORMATION 4.1 Dynamics There are several factors that determine how the headlight should be manipulated while negotiating a curve. The geometry of the motorcycle, the geometry of the headlight, the geometry of the motorcycle on the road, and the dynamics of a motorcycle all help to define the best way to correct headlight aim. Dynamics of single-track vehicles can quickly become very complicated as the subject is explored. The research necessary to understand this subject in detail can be the basis for an entire project in itself. One of the challenges is to determine how detailed the model of dynamics must be in order to accurately calculate headlight aim. Rather than making the model more complicated than it needed to be, we identified the two most crucial degrees of freedom needed to best manipulate the headlight. Any single-track vehicle must bank, or lean in order to overcome the effects of centripetal acceleration while in a curve. Considering a motorcycle in a steady-state turn, we can analyze the forces acting on it in a free body diagram as shown in Figure 4-1. There is one main force acting the motorcycle’s center of gravity (CG). This is the weight of the rider and the motorcycle, mg, acting downward, and is balanced by a normal force acting vertically upward on the contact point. Although there is actually no force acting outwardly at the CG, a “centrifugal” force is a result of the mass of the bike and rider multiplied by the acceleration due to changing momentum in a curve. This force is actually a conceptual force needed to balance the centripetal force acting at the motorcycle’s tires.

Figure 4-1 Free Body Diagram of Motorcycle in a steady-state turn

In examining the free body diagram above, a moment balance performed about the motorcycle’s contact patch yields an expression for the banking angle, β. ν 2 M = 0 = −mgH sin β + m H cos β Equation 1 ∑ cp R ν 2 β = tan −1 Equation 2 gR

If the motorcycle’s banking angle can be measured, the expression will also give the radius of the turn, (R)

ν 2 R = Equation 3 g tan β

Given the two variables for banking angle and velocity, it is possible to predict the radius the motorcycle is negotiating at steady state. There are a few physical factors that will add a certain amount of error to this calculation. This proof assumes that the contact point of the tire is always directly in line with the CG and the centerline of the bike. In reality, the contact patch moves in relation to the centerline, and the CG can move in relation to the centerline as well. Because the motorcycle banks back and forth on its rounded tires, the overall roll axis of the motorcycle becomes the center of the tire’s radius, not the contact point of the tire. Therefore, the height of the roll axis is the radius of the tire’s cross- section. After doing some preliminary calculations, we found that this source of error will be negligible. This calculation introduced an “effective” bank angle, which differed from actual bank angle by only about a degree for most situations. This translates into an even smaller error when used in the turn Radius equation. Another possible source of error can be the CG moving away from the motorcycle’s centerline. The center of gravity for the motorcycle itself is always extremely close to its centerline. The rider can adjust the position of the CG with his or her weight a small amount. In this situation, the motorcycle is the dominant mass, so significantly adjusting the CG requires the rider to actually lean off the motorcycle. Although this is a commonly used technique in the world of motorcycle racing, it is rarely used by most riders; especially while riding on the street at night.

4.2 Light Geometry Low beam headlights are designed to illuminate as much area in front of the vehicle as possible without blinding oncoming drivers. The beam pattern itself is regulated through Federal Motor Vehicle Safety Standards and Regulations (FMVSS) for all legal road vehicles in North America. This committee writes specifications vehicles must adhere to. FMVSS No. 108 [11] is the specification that defines all headlight standards, such as vibration resistance, sealing, temperature, corrosion, abrasion and photometry. The photometry specification for headlights defines the brightness requirements at different points. Usually a photometry specification is a table of light intensity such as candela, lumens or lux. SAE J584 (Appendix A) gives the photometry specification for motorcycle low beams. This spec gives a table of either minimum or maximum intensity values (candela) measured at degrees from horizontal and vertical. The photometry given defines a basic beam pattern that the headlights must have. All of the values given above the horizon are maximum values and values given below the horizon are minimum values. The spec tries to limit the amount of light projected at a distance above the horizon to prevent blinding oncoming traffic, and the minimum values ensure the road below the horizon is illuminated to at least a certain intensity. The photometry suggests that there should be a horizontal cutoff of light 1.5° below the horizon to prevent blinding oncoming drivers. The light must be between 22 and 54 inches above the road surface. Most motorcycle headlights are around 35 inches high. This corresponds to an illuminated cutoff at approximately 115 ft. in front of the motorcycle. Figure 4-2 is a three-dimensional model of a motorcycle low beam. The model represents the main part of the beam required.

Figure 4-2 3-Dimensional Projection of Low Beam

The beam pattern is designed to work in most situations while the motorcycle is traveling straight and is level. However, when the motorcycle banks to negotiate a turn, the beam pattern becomes obscure as it is rotated. Because the beam pattern is pointed down at approximately 1.5°, it rotates away from motorcycle’s centerline and away from the path of travel. The outside of the beam is rotated up and points high into the oncoming lane, potentially blinding other drivers. The inside is rotated down toward the ground illuminates the road with greater intensity which is focused a shorter distance in front of the rider. The following figure illustrates the problem.

Figure 4-3 Cornering Beam Scenarios

In Figure 4-3, the three dimensional shape of the beam can be seen imposed over the roadway. The lighter shaded section of the road represents the intersection of the beam and the road and shows the portion of roadway that would actually be illuminated by the low beam. The area of the illuminated road decreases as the speed and bank angle increase. Also, the illuminated distance in the roadway in front of the motorcycle decreases with the increased speed and bank angle. 4.3 Corner Geometry To correct the aim of the headlight, the geometry of the roadway’s corner must also be understood. The most important feature of a roadway curve is its radius. One of the goals of our project is to understand how to correct the aim of a light for various radius curves. From equation (3), the radius of the turn the rider is negotiating can be solved given the banking angle of the motorcycle and the velocity. Figure 4-4 helps to explain the geometry of a constant radius turn.

Figure 4-4 Cornering Geometry

In this figure, the line tangent to the curve represents the motorcycle’s centerline and instantaneous direction while negotiating the curve. The chord, L, represents the distance in front of the motorcycle where illumination is cut off. The angle, α, is the illumination angle the light needs to be corrected for a certain radius turn, R. The following equation shows the relationship between the turn radius (R), the illumination distance (L) and the illumination angle (α).

L α = sin −1 Equation 4 2R

The illumination distance, L, is given and not variable and the radius of the turn, R, can be computed from the two inputs of velocity and banking angle (Eq 4).

One source of error that enters with the calculation of illumination angle deals with the constant illumination distance. With the illumination distance set at a fixed value of 111 feet in front of the motorcycle determining the illumination angle with small radius turns becomes problematic. As the arc length of the radius approaches the illumination distance or become less than the illumination distance the illumination angle calculated will become undesirable. These small radius turns are typical only at slow speeds where the motorcyclist tends to concentrate on a shorter distance than 111 feet. An approximation was made that a rider would focus on the road 2.5 seconds ahead of him with a maximum of 111 feet. For instance a rider traveling at 20 mph will be focused on the road 73 feet in front of the motorcycle. This decreases the illumination distance during slow speed travel and provides a more accurate illumination angle. The following equation shows the relationship between radius (R), the reaction illumination distance

(LRD), and illumination angle (α).

L α = sin −1 RD where L = 2.5sec*velocity if L ≤ 111 feet Equation 5 2R RD RD

The following chart shows the motorcycle’s speed vs. bank angle vs. illumination angle from 5 to 110 mph and bank angles of 0 to 22 degrees.

Motorcycle Speed vs. Bank Angle vs. Illumination Angle (using reaction time)

20 18-20 18 16 16-18 14 14-16 12 12-14 Illumination Angle 10 10-12 8 8-10 6 4 6-8 2 4-6 0 26 2-4 5 0-2 20 14 35 Bank 50

65 2 80 Angle Speed (mph) 95 110

Figure 4-5 Motorcycle Speed vs. Bank Angle vs. Illumination Angle

4.4 Correction The headlight will be corrected on two axes. The first axis will correct for the bank angle of the motorcycle. The headlight correction will simply be to rotate the light the same angle, but in the opposite direction. This axis is defined by the geometry of the motorcycle. Because motorcycles use round tires, the radius of the tire’s cross-section defines the roll axis. Usually, the rear tire has a larger radius than the front. Since the roll axis is defined by both the radii of the front and rear tire, the smaller front radius causes the roll axis to be declined to the front of the bike. This axis should be parallel to the light’s roll correction axis in order to maintain correct aiming. The second correction is the illumination angle. The illumination angle was calculated given the corner radius (Eq 4), which was in turn found to be related to both the velocity and the banking angle. The figure 4-6 compares a corrected beam aim to the uncorrected aim. Figure 4-7 shows the two correction axes.

Figure 4-6 Proposed Correction Scenario

Figure 4-7 Two Axes of Rotation

5.0 PRIOR STATE OF THE ART Various means have been proposed to correct the motorcycle lighting problem, although there are no products in use today. Most of the patents include two components that make up a system. The first component is a mechanical or supplementary device to move or turn on the headlight and the second is the means for detecting the state of the motorcycle to determine the correct movement of the headlight. There are some patents that come close to our design with one component, but none of the patents are similar to our design in both aspects of the system. One of the first people to file a patent for a corner adapting motorcycle headlight was Rodger E. Skoff in 1975 [23]. His patent was titled “Cornering Light System for Two-Wheeled Vehicles” patent number 4,024,388, and was approved in 1977. Skoff cites the patents for the automobile cornering lights, and sees the need for a two-wheeled application. His design consists of supplemental left and right beams that turn on depending on the lean angle of the motorcycle. His means for detecting the lean angle of the motorcycle consisted of a conductive fluid (mercury) in a “U” shaped tube. The tube had sensors that would detect the level of the fluid on either side (Figure 5-1a).

Figure 5-1a Mercury Sensor (static)

Major emphasis was put on the fact that his left and right headlight assembly would not need to move due to its position on the motorcycle and the shape of the beam. For a range of lean angles (10° to 45° from vertical) the light pattern would be optimized just by the nature and shape of the beam. In other words, Skoff would use the leaning of the motorcycle itself to do the aiming of the light. Therefore the only output from his U-tube would be direction of lean (not magnitude), indicating which light to turn on. One flaw with this design is that unless the rider is hanging off of his motorcycle (therefore changing the center of gravity) the conductive fluid would always be centered in the u- tube giving no indication of direction of lean at all. The reason for this is that if the rider remains centered on the motorcycle then center of gravity is going straight through the centerline of the motorcycle. If the rider leans off the bike the center of gravity is no longer going through the center of the bike (Figure 5-1b). Skoff’s design is based on the assumption that all riders lean off their motorcycles. Other flaws in using the U-tube detection device is that it may provide false readings due to vibrations, road conditions and splashing. Such false readings would activate the cornering lights at incorrect times, possibly glaring other motorists.

Figure 5-1b Mercury Sensor (dynamic)

Around the same time that Skoff was filing for his patent Jacques Marius Alphen was also trying to receive approval on his. His first patent, 3,939,339 [2] “Lighting System for a Motorcycle”, was approved in 1976. Alphen’s system for correcting the orientation of a motorcycle headlamp includes a sprung weight that moves proportionally to the centrifugal force caused by the turning of a motorcycle. In one embodiment, transmission chains to control the correcting movement of the headlamp mechanically link the weight. In another instance, the corrective movement is carried out electrically under the control of a transducer that senses the extent of movement of the weight. Alphen’s headlight assembly physically rotates around the beam axis, therefore correcting for the lean of the motorcycle. His method for lean angle detection uses a sprung mass that slides along the vertical axis of the motorcycle (i.e. moving from the seat to the contact point). The greater the centrifugal force, the more the mass will be pulled down toward the contact point. The movement of the mass is translated to the headlight assembly, which then rotates around the beam axis (Figure 5-2). To detect the direction of lean Alphen uses a steering sensor comprised of a mechanical cam system.

Figure 5-2 Inertial Mass Switch

There are three disadvantages to Alphen’s system. The first disadvantage is in the lean angle detection system. Specifically, the sprung mass is susceptible to bumps and vertical changes in road conditions. The second disadvantage is in Alphen’s lean direction detection system, which uses a cam system connected to the handle bar. At higher speeds counter steering at the beginning of a turn must be taken into consideration and after the turn is initiated the movement of the handlebars is very minimal (Figure 5-3). The third disadvantage is that the light beam is only corrected for the lean angle of the motorcycle, and no correction is done to pivot the light into the turn.

Figure 5-3 Counter-steer Diagram

Alphen submitted two more patents after his initial patent in 1976. His second patent, 4,075,469, [4] approved in 1978 is titled “Lighting Systems for Motor Cycles” abandons the use of a sprung mass and steering sensor. Alphen’s new method still corrects only on the beam axis but, uses a “gyroscope system” to detect both the magnitude and the direction of lean of the motorcycle. The “gyroscope system” that Alphen proposed included a mechanical freewheel type gyroscope with mechanical displacements converted to electrical signals by means of potentiometers, strain gauges, or capacitors. The electrical signals would be fed into a control unit that in turn would control the headlight rotation. Two years later in 1980 Alphen has approval on his third patent, 4,223,375, [3] titled “Headlight Systems for Motor Cycles”. In this final patent Alphen realizes the problems with his old patent stating: “it has been found that there are difficulties in providing a sufficiently accurate gyroscope system; also the gyroscope system may suffer from drift, resulting in orientation errors.” With no accurate gyroscopes available at the time Alphen went back to his original design of a sprung mass system for detecting magnitude of lean, and a gyroscope system to detect only direction of lean, replacing the steering angle sensor. There were still some disadvantages to his design, in that it still used the same sprung mass system and only corrected the headlight for lean angle. In 1989 Shizuya Miyauchi [20] patented his “Road Surface-Sensitive Beam Pattern Leveling System for a Vehicle Headlamp” patent number 4,868,720. Miyauchi’s invention included a headlamp unit that would rotate around the beam axis, correcting for the lean of the Motorcycle. The means for detecting this lean angle of the motorcycle comprises of at least one road sensor that transmits some radiation, such as an ultrasonic wave or infrared rays, toward the road surface. The radiation is then reflected back to one or more sensors giving an accurate measurement of lean angle (Figure 5-4).

Figure 5-4 Reflector Sensors

Miyauchi discredits the use of gyroscopes to detect lean angle on a motorcycle due to the fact that they use true horizon and not real world horizon. For example: Suppose that the motorcycle with the gyroscope controlled beam pattern leveling system is negotiating a banked curve, with the vehicle laterally slanting out of the perpendicular and into right angular relationship with the roadbed. Since the vehicle is then at an angle to the perpendicular, the gyroscopic system will detect this angle and correspondingly adjusting the beam pattern into an angled position with respect to the bank. This would be true due to the nature of the gyroscope, but the effect would be very minimal considering the small grades of transversely banked roads. (Usually no more than 6% grade). Disadvantages to Miyauchi’s reflected radiation sensors are that when the radiation is projected from the low side of the motorcycle can produce a weak return signal because of the acute angle of refection. When the radiation is projected from the high side of the motorcycle there is a chance that the radiation could reflect off curbs, potholes, and be susceptible to different road conditions. There is also an issue with the speed of the motorcycle affecting the reflections ability to reach the sensor. Miyauchi’s design also only compensates for the lean of the motorcycle, and adjusting the light on that basis. No correction is made to turn the light into the corner. In 1995 Jerry Jones’ patent, (5,426,571), [16] for a “Motorcycle Headlight Aiming Device” is approved. Jones’ patent uses combination of Miyauchi’s refection sensors and speed sensors to detect bank angle of the motorcycle and to compensate the light for the lean angle of the motorcycle and pivot the light (around the axis normal to the ground) into the turn. Jones describes three different types of solutions to the light aiming part of his system His main mechanical device includes a rolling motor and a fixed pin track motor. A second design uses a parallel linkage to control pivot and a second rolling device to roll the whole assembly around the beam axis. A third embodiment is an array of supplementary lights that turn on at different intervals depending on lean angle of the motorcycle (Figure 5-5).

Figure 5-5 Supplementary Lights

He also makes some claims for secondary uses for his device such as throttle limiting at extreme angles, other uses include camera mounting, and front wheel lift off prevention. Jones’ idea of aiming the light in more than one axis has an advantage over the other designs that only correct along the beam axis. The disadvantage to his design is in the unreliability of the radiation refection lean angle sensors. Jones’ releases a second patent, (5,811,656) [17], three years later in 1998, in which he replaces the radiation refection sensors with a “Simplified Inertial Bank Angle Sensor”. This device consists of a flywheel or spinning mass mounted parallel to the longitude axis of the motorcycle. The flywheel is housed in a casing that moves with the motorcycle, and the flywheel moves independent of its casing. A scanning device is used to measure the distance between the casing and the flywheel. This provides the required information to calculate lean angle and compensate the headlight. The major problem with this device is that it needs to be manually corrected for drift due to friction, by stopping the flywheel while the motorcycle is in an upright position. Similar designs have also been tried in the automotive industry but were not successful in the past. Only recently has adaptive frontal lighting become a feasible idea. Hella KG Hueck & Co. [13] have done research on the driver’s response to different lighting conditions, during different driving conditions, and is currently working on a “Variable Intelligent Lighting System” (VARILIS) for automobiles. This new technology will adapt the frontal illumination to match changing road conditions, speed, weather, and time of day. Valeo, the leader in automotive lighting, is also working on an intelligent lighting system to significantly improve the illumination of road curves by directional control of vehicle headlight beams. The system will be called “bending light” and should be available on certain automobiles in two to three years time.

6.0 PROTOTYPE DESIGN 6.1 System Overview To achieve the proposed motorcycle headlight correction, a full system of interacting components is needed. The system can be broken down into three different categories: inputs (sensors), microprocessor control unit, and outputs (headlight aiming device). Information about the motorcycle’s speed, angle of inclination, and angular velocity about the roll axis is detected by sensors. This information is transmitted from the sensors to the microprocessor control unit, where it is interpreted and processed. The microprocessor control unit will then output control signals to the headlight aiming device. (Figure 6-1)

Figure 6-1 Control System Block Diagram

Three major inputs are required to determine the optimal position of the beam in each axis. The first input is the static bank angle sensor, more commonly know as an inclinometer. The purpose of the inclinometer is to set a reference angle in order to correctly calculate the dynamic lean angle. This bank angle must be recorded when the motorcycle is stationary and used as a starting point when calculating the banking angle. The second major input is the dynamic angular rate sensor or gyro. The gyro detects the rate at which the motorcycle is rotating about its roll axis. This rate can be integrated over time to return an angular position. When combined with the reference angle from the inclinometer the actual bank angle of the motorcycle can be determined. The third major sensor is the speed sensor or Hall Effect sensor. The speed and bank angle are needed to calculate the illumination angle (amount the headlight pivots into the turn on an axis normal to the road). The second part of the corner adapting motorcycle headlight system is the microprocessor control unit. The design of this part of the system is primarily the responsibility of the Electrical and Computer Engineering (ECE) group. The microprocessor control unit will collect the reference angle, angular rate, and vehicle speed signals. The collected sensor information is then processed and used to calculate bank angle and illumination angle. The outputs of the microprocessor control unit are sent to the third part of our system. This part of the system contains two servomotors, which actuate the headlight aiming device. One servo controls the bank angle correction and the other controls the illumination angle correction. The aiming device must be able to move in two degrees of freedom, i.e. about two different axes. The first degree of freedom provides for rotation about the beam axis (bank angle axis), this axis must be connected to the motorcycle, because its rotation is dependent on the bank angle of the motorcycle. The second degree of freedom allows for rotation on an axis normal to the road surface (illumination angle axis). In order to keep this axis normal to the road it must be dependent on the first axis and not connected directly to the motorcycle. (Figure 6-2)

Figure 6-2 Rotation Axes

6.2 Electrical Design The goal of the electrical portion of this project is to design an accurate and robust control system. Because of the safety risks involved with a control system failure, it is important to choose components that work well together, are accurate, and are reliable. The main job of the electrical control system is to monitor a series of inputs from sensors and quickly decide how to control the servos. The sensors and the microprocessor must work together in order to determine the instantaneous lean angle of the bike and the bike’s speed. Measuring the bike’s speed is straightforward. This can be accomplished with a hall affect sensor measuring the rotation rate of the front wheel. Measuring the bank angle is more challenging and requires the use of an angular rate sensor (gyro sensor).

6.2.1 Speed Detection All bikes are equipped with speedometers. Unfortunately most are driven by a set of gears, which is turned by a cable connected to the front wheel hub. Some newer bikes are equipped with electronic speed sensors that measure the speed of the bike by using an array of information from the engine control computer such as engine revs and gearbox selection. The later of the devices can be configured to output a signal to the logic circuit. But since not all bikes have this, the best option is to use a speed sensor that mounts to the front wheel and is independent from the speedometer of the bike. The simplest speed sensing devise uses a magnet attached to the front wheel. The magnet passes by a Hall effect detector that is mounted on the front fork. As the magnet passes the detector, it effectively closes the switch, counting each revolution. To determine velocity the microprocessor measures the time between each state change of the sensor. The circumference of the tire can be input into the software, and system can calculate the speed.

6.2.2 Angular Detection Measuring the motorcycle’s lean angle accurately is a more challenging problem. There are sensors available that can quickly and accurately measure an angle of tilt with respect to gravity. However, measuring the angle with respect to gravity will not work because of the accelerations due to cornering. A gyroscopic angular rate sensor is needed to measure rotation independently from accelerations. The main problem with gyroscopic sensors is that they measure rotational rate. The control system needs a banking angle in order to properly correct the light’s aim. In order to determine the banking angle, the microprocessor must continually integrate the angular rate signal from the gyroscopic sensor. In practice, the microprocessor will operate on software running in a loop. The processor must accept an angular rate signal from the sensor at some point during the loop. The program will need to know the time between each gyroscope reading, and use this to effectively integrate the signal and keep track of the banking angle. The software uses this bank angle directly to control the bank angle correction servo. The software uses the bank angle along with the speed input to calculate the turn radius and the illumination angle correction. Another problem with the gyroscopic sensor is it’s inherent error. Any sensor has error, but relying on a gyroscope alone to continually track the angle leaves the microprocessor continually adding error with each integration step. This effect causes the calculated angle to drift linearly with time. There is also error added from the random noise generated in the sensor. These effects will cause all but the most expensive of gyros to produce a drift in angle that will become noticeable after a few minutes. One way to address this problem is to compare dynamic signals from both a tilt sensor (inclinometer) and the gyro sensor during operation. The inclinometer will be stable over long time periods, so comparing inputs from both sensors over time will alert the software to increasing drift angles from the gyro’s error. Because the gyroscope cannot measure gravitational forces, the control system will not know what angle the motorcycle is at relative to the actual horizon without the use off an additional sensor. This problem can be addressed by using the inclinometer. An inclinometer senses the acceleration of gravity as a reference direction. This sensor is useful to establish an angle of bank when the motorcycle is not moving, such as when the motorcycle first starts up. In practice, the control system software will first take an input from the inclinometer when the motorcycle is started and not moving. This way, the control system will know the initial banking angle, at which point the system can enter a loop control to measure input from the gyroscope and integrate the angular rate to find the changes in bank angle. The software can also monitor the motorcycle speed, and revert back to inclinometer input only when the motorcycle is stopped, i.e. Speed = 0. Occasionally calibrating the angle when the motorcycle is stopped also partially addresses the issue of accumulating angular rate error. For the purposes of the demo stand, the control system uses just the inclinometer for all of the bank angle detection. For still demonstration purposes, there are no centripetal acceleration components, so using acceleration due to gravity as the reference to horizon is the most accurate method of detecting bank angle. Initially, we planned to use the gyroscopic sensor to determine bank angle. Due to time constraints and electrical hardware availability, it was decided to simply use the static inclinometer for the demo model. The use of the gyro sensor demanded more hardware with longer lead times to obtain and more research to properly integrate the sensor with the BASIC Stamp. Further testing to be carried out on a motorcycle would require the use of the gyro sensor.

6.2.3 Electronic Components In order for a simple control system to be effective, it is important to choose components that will work well together. The main component of the control system is a microprocessor. For our particular project to work well, the microprocessor must be somewhat fast and have the ability to easily interface with a series of sensors. This control system also requires accurate measurements from the sensors. A Basic Stamp was chosen as the microprocessor for this control system. A Basic Stamp is a simple microprocessor computer with the ability to perform logic, store information in memory and interact with an array of 16 pins, all of which can be set to either input or output. The Stamp uses a simplified version of the Basic programming language with many pre-set functions such as trig functions. Basic Stamps are available in several different forms with varying speed and memory. The Stamp is relatively fast, capable of 4,000 operations per second. The development of the control system algorithm will tell approximately how much memory the system will require, although the memory demands should be small. The Basic Stamp has the ability to communicate though standard serial communications (RS232). Doing this lowers the demand on the amount of outputs and allows the use of “intelligent” components. For example, our system uses a Liquid Crystal Display (LCD) screen that requires only one output from the Basic Stamp. The display screen has the ability to recognize serial signals and process commands with onboard intelligence. The display screen will be used during system testing to monitor the Stamp’s calculations. One disadvantage to the Basic Stamp is its inability to perform floating-point math operations. In our case, exacting calculations are critical; therefore, we need to use an additional math coprocessor with the ability to perform fast floating-point operations. The math coprocessor is called Pak II and is designed to be used with serial communications. Therefore, it easily integrates with the Basic Stamp.

6.2.4 Operation The entire system will power on in parallel with the motorcycle startup process. All of the electrical components are active and require a certain voltage. All of the components are powered by a power distribution circuit. This is a series of voltage regulators that control voltage for each device. The power distribution circuit receives power when the motorcycle’s key is switched to ignition. Therefore, the entire system will turn on with the ignition key. Consequently, the system must be ready to work with a motorcycle and its sensors as soon as the bike is started

6.2.5 Algorithm The control algorithm is the basis for the system’s software. The algorithm determines the order in which processes take place. The microprocessor starts from its first line of code whenever it is powered on. As soon as the key is switched to ignition, the basic stamp will begin running its software. Working under the assumption that the motorcycle will be stopped when the ignition is switched on, the first task of the control system is to acquire a static banking angle. One of the first lines of code will be to read the inclinometer and store an angle measure. The software can also monitor the speed and verify that it is zero as it takes the inclinometer reading. After the system determines the starting angle, the system will quickly enter the angle into a software loop designed to calculate the instantaneous banking angle and speed of the motorcycle. This instantaneous banking angle loop will be the main control loop on the algorithm. The loop will accept inputs from the angular rate sensor and the Hall effect speed sensor. The order in which the loop performs these two operations is arbitrary. The loop first reads input from the two sensors. The speed sensor signal is a measured time between the state changes of the sensor. The number of revolutions per second can be multiplied by a factor incorporating the tire’s circumference, determining the speed. The gyro sensor signal is proportional to an angular rate i.e. degrees per second. The system must either know an accurate measure of time between each loop or measure the time in conjunction with each angular rate reading. Knowing the time between each rate measurement, the rate can be multiplied by the time interval giving an incremental change in bank angle. This angle is added to the previous bank angle, effectively integrating the angular rate signal. After the signals are read and the bank angle and speed are determined, the loop can move on to calculating the turn radius and illumination angle correction. The bank angle correction is equal but opposite of the bank angle measurement. Both of these correction signals are multiplied by the gear ratios between each of the servos and control shafts to get the correct angle. The next step in the loop is the output. The Basic Stamp outputs both correction signals to a serial controlled servo controller. This servo controller uses one output from the Basic Stamp and can control up to eight servos. The main advantage to this controller is its ability to continually send the signal once received from the Basic Stamp. This requires very little attention from the stamp to perform the task of servo control. After the signals are sent to the servos, the loop repeats, continually updating correction signals. The algorithm used for the demonstration stand is different from the original design algorithm because the demo stand does not use the gyroscopic sensor for its bank angle detection. The demo stand software acts as the original software would when the motorcycle is at rest; it reads the signal from the inclinometer to determine banking The BASIC Stamp uses a simple programming language called PBASIC, which is a variant of the BASIC programming language. The language uses basic Boolean operators and IF loops. Without the use of a math co-processor, the Stamp is limited to the mathematical operations it can perform. The Stamp can perform simple addition, subtraction, multiplication, division and power operations with integers. The stamp cannot do floating-point operations or inverse trigonometric functions. Because the stamp cannot perform floating-point operations required for most trigonometric functions, it uses its own method of angular delineation. The Stamp uses “brads” instead of degrees or radians. One brad represents one unit between 0 – 255 in one full circular rotation. Transforming the algorithm into usable, accurate code required mathematical approximations to compensate for the Stamp’s limitations. Most of the original governing equations derived from the motorcycle physics model used either inverse trigonometric functions or floating point operations. There were a few techniques employed in order to code these functions. One of the techniques used was multiplying numbers by factors of 10 or 100 before division operations to prevent dropping significant digits, then dividing by 10 or 100 to normalize the answer. Another technique used with more complicated, non-linear functions was to graph the significant portions of the function using Excel, then adding a best-fit line using a polynomial or power function. Best-fit functions could be used with the BASIC Stamp minimizing the error. The functions were then modified to avoid dropping significant digits during division operations.

Figure 6-3 Process Block Diagram

7.0 MECHANICAL COMPONENT DESCRIPTION The headlight-manipulating device was designed to allow the headlight to adjust to the corrected position. The entire headlight manipulating assembly had to be small, light, and durable. Components were selected based on several factors including durability, robustness, size and weight, necessity for regular maintenance, and ease of manufacture. The design for the headlight manipulating mechanism is shown in Figure 7-1. Individual components can be seen in the exploded view shown in Figure 7-2. The various components and their interactions with one another are first outlined, and then followed by detailed descriptions of each. Engineering drawings of all components are shown in Appendix C. The main mechanical component is the carriage, which acts as a platform for most of the other components and also dictates both the bank angle (β) and the illumination axis’s (α) position in relation to the light. The entire carriage rotates on the beam axis, counteracting the lean angle of the bike. Connecting the carriage to the motorcycle (or backplate in our demo stand) is one of two similar flanged shafts. The first shaft, bank shaft, is attached to the backplate and corrects the headlight about the beam axis. The second shaft, illumination shaft, rotates normal to the ground correcting the illumination angle. The illumination shaft is attached to the light bracket, which holds the headlight. Sealed ball bearings are used through out the design to support the two shafts. Two servomotors, one for each shaft are used to move the headlight assembly and point the beam in the corrected position. The bank servo corrects the bank angle and uses two gears to rotate the headlight assembly around the beam axis β while the illumination servo uses a pulley and drive belt system to correct the headlight about the illumination angle α. .

Figure 7-1 Headlight Assembly

Figure 7-2 Exploded Headlight Assembly

The headlight aiming device must also be able to fit into the same amount of space that is currently provided for normal headlights. Figure 7-3 shows the headlight aiming device positioned in the same amount of space left after removing the left-hand reflector type headlight. This particular headlight casing is from a 1999 Suzuki™ GSX-R 600 motorcycle, and uses a dual reflector type setup.

Figure 7-3 Headlight Size Relationship

Modal analysis was performed on the full assembly to determine the natural frequency of our device. This analysis was important due the vibrations occurring on a motorcycle and the physical shape of our device. The entire load of the projector beam and other components supported by the bank angle shaft act as a cantilever beam with mass at the non-constrained end. The headlight manipulating device model was simplified by reducing all of the components to a single mass in the shape of a block. The first three natural frequencies were determined to be 1.43Hz (85.5 rpm), 5.79Hz (347.31 rpm) and 27.26Hz (1635.78 rpm). The third mode shape is the only one of concern because it is close to the idle speed of a motorcycle engine. Fortunately, due to engine dynamics the actual vibrations felt on a motorcycle rarely match the engine rpm.

Figure 7-4 Modal Analysis of Assembly

7.1 Carriage The carriage’s main purpose is to allow the bank angle axis to connect to the motorcycle without affecting illumination angle movement. In other words, rotation about two axes is needed but only one axis can be directly connected to the motorcycle. For our purposes the bank angle axis must be attached to the motorcycle in order to keep the illumination angle axis normal to the ground. The L-shape of the cradle allows it to support the illumination angle correction mechanism and enables it to position the two axes with respect to the headlight. The bank axis runs through the beam axis of the headlight and the illumination axis is located at the front of the headlight. It is important that the bank angle coincides with the beam axis. Therefore, any correction made will not effect the aiming of the headlight, just the orientation. It is also important that the illumination angle axis is located at the front of the headlight the swing of the projector beam is minimized and the clearance can be small.

Figure 7-5a Carriage Model Figure 7-5b Carriage Prototype (minus trusses) The carriage must resist the bending and vibration effects that are caused by bumps in the road while the motorcycle is moving. Another consideration is the placement of the illumination angle correction components on the carriage so that the light can rotate without interference. To better understand the effects of bending the cradle can be modeled as a simple cantilever beam. The side flanges and support arms are not considered in the model, however, the cutout in the back of the cradle for the servo is included. Because of the cutout the modeled cantilever beam is comprised of two different sections with two different area moments of inertia. To model the beam the superposition approach was taken. The force was moved to the edge of the reduced area section and an appropriate moment was applied. This is possible because the assumption was made that the section of the beam with the larger moment of inertia can be considered rigid compared to the other section. Figure 7-6 below shows a diagram of the model.

Figure 7-6 Cradle Superposition Model

In figure 7-6 picture (a) represents the cradle modeled with real loadings, where pictures (b) and (c) represent the separate loadings that combine to make the original model. The equations to solve for the slope in (b) and (c) are listed below.

PL2 θ = Equation 6 B 2EI

ML2 θ = Equation 7 C EI

θ A = θ B +θ C Equation 8

The two results are superimposed to give the slope at the end of the cradle. The equivalent force on the cradle was found to be 33 lbs and causes a slope of 8.14° (6.64° difference) at the end of the cradle. This results in an illumination distance of 20.4 feet, well below the necessary illumination distance. The maximum bending stress was also calculated and found to be 55130 lb/in2. The safety factor was calculated and was found to only be 1.09. This clearly illustrates the need for the side flanges and support arms. A more detailed analysis of cradle will have to be modeled with a finite element package to provide more realistic results. For detailed calculations refer to Appendix B. Stress analysis was performed on the carriage using finite element analysis software. The carriage, along with the bank angle shaft supports most of the weight of our device. Different designs were tested and analyzed for this critical part. Our first design included small flanges along the sides of the carriage. Through stress analysis the flanges were determined to be superfluous. Two trusses were riveted to either side of the carriage on small flanged tabs. The trusses provided sufficient strength with a 30lb force the maximum stress on the carriage reached ~7000psi.

Figure 7-7a FEA of carriage Figure 7-7b FEA of carriage with out trusses

7.2 Shafts There are two shafts in the headlight aiming device. One shaft (bank shaft) connects the main cradle to the motorcycle. The second (illumination shaft) connects the headlight mounting bracket to the main cradle. The bank shaft is named such because it creates the axis that the headlight aiming device will rotate around to correct for the bank angle of the motorcycle. The illumination shaft is a named such because it creates the axis for the headlight and bracket to rotate around to correct for the illumination angle.

Figure 7-8 Shaft

The bank shaft and the illumination shaft are very similar in their design. Both shafts are solid 0.25-inch aluminum shafts that are supported by bearings. Both shafts have flanges on the ends. These flanges have four holes tapped in them so they can be connected to the carriage (bank shaft) and the light bracket (illumination shaft). To keep the shafts in the correct axial position collars are used. The bank angle shaft will be supporting the weight of the carriage and illumination angle correcting mechanism. Under static conditions the shaft will easily support those components that weigh 1.1lbs (0.5 kg). It is the dynamic load produced when the motorcycle moving that is the concern. During extreme cases, such as hitting a pothole, a motorcycle could experience vertical acceleration in the range of 50 G’s. This drastically increases the required stress for the shaft to withstand. The bending criteria of the shafts are important because the vertical illumination angle will change if the shaft deforms. The average height above the ground of a motorcycle headlight is 35” and the SAE specifications states the headlight shall be pointed at an angle of 1.5 below the horizon. This downward angle yields and illumination of 111ft. Now if the bending of the shaft (and/or the cradle) allows a slope of 5° at the end of the shaft the headlight will point down 6.5° and the illumination distance will be decrease to 25 feet.

Calculations were made for the bank shaft to find the slope at the end of the shaft, and the maximum stress that the shaft would experience. The calculations are made modeling the shaft, the two supporting bearings, and an equivalent force applied at the end of the shaft. The equivalent force is found using the center of gravity of the headlight aiming device and its distance form the end of the shaft. The bearings were modeled so that they only exert vertical forces. To solve for the slope the shaft, the method of superposition was used. Below is a diagram of the model.

Figure 7-9 Bank Shaft Superposition Model

In figure 7-9 picture (a) represents the entire shaft modeled with true loadings, where pictures (b) and (c) represent the separate loadings that combine to make the original model. The equations to solve for the slope in (b) and (c) are listed below.

ML θ = Equation 9 B 3EI

PL2 θ = Equation 10 C 2EI

θ A = θ B +θ C Equation 11

The two results are superimposed to find the resultant slope at the end of the shaft. Using a 0.25-inch aluminum shaft, the slope is 1.75° (0.25° difference) and the illumination distance is 96 feet. For detailed calculations refer to Appendix B. The maximum stress due to bending was also calculated and found to be 5580 lb/in2 . The yield strength of aluminum is 37000 lb/in2. This corresponds to a safety factor of 6.6 respectively. For detailed calculations refer to Appendix B. Stress analysis was performed on the shafts using finite element analysis software. A perpendicular force of was applied to the flanged end of the shafts and the non-flanged end was constrained in all directions. Results showed that during a 30lb force at worst case conditions (large moment arm and with an estimated max impact force of 30 lbs) the yield strength of the aluminum (37000 lb/in2) was reached. The amount of weight that needs to be carried by the bank angle shaft is approximately 2 lbs; this allows for a factor of safety of 15 under normal conditions.

Figure 7-10 FEA of Shaft

7.3 Bearings The ball bearings chosen are stainless steel and are shielded against the elements. They have a 5/8 inch outer diameter and a ¼ inch bore to accept the ¼ inch shaft. They also have a small flange to ease alignment when pressing into the bearing block. To support the bank shaft the bearings are press fit into an aluminum block that is attached to the backplate. Two precision bearings are used to support the weight of the carriage as opposed to one bearing. This design minimizes angular deflection while distributing the load. A single bearing is used to support the illumination shaft because the forces are much less than those associated with the banking shaft.

Figure 7-11a Bearing Figure 7-11b Bearing Block

7.4 Servos A servo is a small device capable of applying a torque through an output shaft. A typical servo assembly consists of an electronic motor, a set of gears, control circuitry, and the housing. It receives a Pulse Width Modulated (PWM) signal (typically at 50 Hz) from a servo controller, which dictates a specific angular position. The servo controller adjusts the PWM signal according to the desired angular output of the servo. A servo functions as a closed-loop control system, meaning that it is continuously comparing its angular position to its input signal. If the input signal changes, the servo immediately responds with a change in angular position. The servo will remain at the specified angle and resist movement for as long as the input signal remains unchanged. If the input signal is shut-off or the servo is powered down, it will not actively move to any specific “home” position, but it will no longer resist motion due to external forces. Servos were selected as the power actuating devices in the headlight assembly for several reasons. The majority of servos on the market today have a range of motion of approximately 180°, which is more than sufficient for both axes of rotation (α & β). Servos use high-speed electric motors and reduction gears to produce a substantial amount of torque considering their size. Servos are also able to make high-speed precise angular changes. Servos only draw as much current as needed, which is advantageous considering the entire headlight control system is an additional load on a motorcycle’s electronic system. For these reasons, servos are excellent for use in high precision, high speed, and low to moderate torque applications. Two separate servos are utilized to move the headlight throughout its range of motion between both the bank angle (β) axis and illumination angle (α) axis. The servo’s used are Futaba model S3302, which have a range of motion slightly greater than 180°. The servo housing measures 1.57 x 1.42 x 0.76 inches, and is shown in Figure X.X. Bank servo is mounted to the backplate and compensates for the banking angle β by rotating the entire cradle assembly. Illumination servo is mounted on the cradle, and rotates the headlight left and right, compensating for the illumination angle α.

Figure 7-12 Servo

The torque that the servo will need to rotate the cradle can be calculated by analyzing the light assembly under dynamic conditions. To analyze the maximum torque, two different aspects have to be considered. The first is the force needed to overcome centripetal accelerations during steady state corning. Working under the assumption that our maximum lean angle will be approximately 45°, this corresponds to 1g of lateral acceleration. The bank angle correction servo will have to counteract the torque induced by this lateral acceleration. This force acts at the light assembly’s center of gravity, which hangs 0.65 inches below the axis of rotation. The torque required to counter this force is shown by the following expression.

τ = Fd Equation 12

Where F = mg at one g, and d = the distance from the axis of rotation to the center of gravity. The torque required to counteract this lateral acceleration is on 0.71 in-lbs. The torque acts through a reduction gear set to the servo at a ratio of 1.75:1. 0.71in-lbs/1.75 = .4 in-lbs. The second aspect to be considered is the torque required to overcome the rotational inertia at the motorcycle’s maximum angular acceleration. The maximum acceleration is a value estimated by observing and timing fast transitions under extreme riding conditions. This maximum value is estimated to be approximately 100°/s2. After sensors are installed on a motorcycle, this number can be determined with much greater accuracy. The following equation relates torque required to overcome rotational acceleration.

τ = Iα Equation 13

I is the mass moment of inertial about the rotation axis, and α is the maximum angular acceleration value. The mass moment of inertia was calculated with CAD software. Using the maximum angular acceleration, the maximum torque required on the shaft was calculated to be approximately 5 in-lbs. The reduction gear set reduces the torque required by the servo to 2.85 in-lbs. In order to find a maximum torque value under any circumstance, these two torque values are simply added to 3.2 in-lbs. Therefore, the servo must be able to apply a torque of 3.2 in-lbs. The S9402’s are rated at a maximum torque output of 111.1 oz-in, which is equal to 6.94 in-lbs, providing for a factor of safety of 2.16.

7.5 Pulleys & Drive Belt Due to the configuration of the design and the size of the servo and light it was decided to go with a set of pulleys connected with a drive belt to correct for the illumination angle. This will allow for good resolution in a lightweight, compact, and durable design. The pulleys and belt have teeth to prevent the belt from slipping, which could create a large margin of error. The maximum illumination angle is approximately 20 degrees each direction. A ratio of 3.33:1 provides 27° of motion to allow for adjustments in the prototype. This ratio provides the illumination shaft with the required torque and resolution. The pulleys selected are 0.458 and 1.528 inches in diameter. Once again aluminum was selected for its light weight and strength characteristics. The larger pulley will be attached to the headlight through a shaft and a bearing. The necessary belt length to connect the two pulleys is 8.08 inches. To reduce the risk of slippage or misalignment of the teeth, the proper tension must be placed on this belt. Therefore, the servo will be mounted in slotted holes so its position can be adjusted. The belt is made of neoprene rubber with nylon on the exterior and fiberglass reinforced interior. The reinforcements reduce the ability of the belt to stretch and provide it with a breaking strength of 240lbs.

Figure 7-13 Pulleys and Drive Belt

7.6 Gears The rotational range of the servos is 180 degrees. The maximum bank angle of a bike during average driving conditions is about 45 degrees in each direction (90 degrees total). A 1.75:1 gear ratio yields a range of 103 degrees or 51.5 degrees in each direction. This was chosen to allow some extra range for fine-tuning the system. This ratio also gives a higher resolution when correcting the beam orientation and also provides a high torque to the bank shaft. The gears chosen are relatively small at 1 ¾ and 1-inch pitch diameters. Precision gears are chosen to reduce backlash between the teeth of the gears, which would produce an error in the corrected bank angle of the light beam. These gears also include a setscrew to attach them snuggly to the shafts and the servos. Aluminum was chosen over plastic as the gear material due to the fact that the plastic gears may deform with temperature changes. Stainless steel was also ruled out because of weight and unnecessary cost. The lightweight components help in lowering the moment of inertia for the moving assembly as well as keeping the overall weight down.

Figure 7-14 Gears

7.7 Headlight The main goal of the project is to provide better illumination while cornering at night. Keeping that in mind, it is important to utilize the best available type of frontal illumination. If the headlight was not sufficient, the goal would not be achieved no matter how advanced the aiming system. In the today’s motorcycle and automotive industries the majority of the headlights use halogen bulbs (H4 and H7). Halogen bulbs have been used for years and were the best option available. Recently, with the introduction of xenon bulbs, far better lighting options are available. Xenon lights offer two major advantages over halogens. First, a xenon bulb produces twice the light of a modern H7 (halogen) bulb while using only 2/3 the power. Secondly the xenon bulb produces a brighter and “whiter” light, which closely resembles daylight. The main disadvantage to xenon lights is the cost. Xenon lights are substantially more expensive than typical halogen bulbs, which is the reason why the prototype uses a halogen. The differences between the two lights are transparent to the aiming and control system, as they will be insignificant for the demonstration.

Figure 7-15a: Xenon Headlight Figure 7-15b: Halogen Headlight

The daylight-quality light that is produced by the xenon bulbs accommodate natural human visual habits. In other words, the light helps a driver relax and tire less quickly because they don’t have to concentrate on looking as much. The xenon light also increases colored vision and contrast, which is helpful during fog or other visually impairing weather. Until recently, the xenon technology was only used for dipped beam (low beam) applications, but modern advancements have made it possible to use it for the main beam (high beam) as well. A bi-xenon bulb combines both the dipped and main beam into one compact unit. A 1997 survey carried out by Emnid on xenon lighting returned these results: -94% had a positive opinion of xenon light, above all brightness (42 %) and general quality of illumination (35 %) were quoted. -85% of all xenon users state that they are able to see better at night, in the case of the over-50 years old, this figure is even 90 %. -83% of all xenon users would order xenon headlamps for their next car. -75% of all xenon users said that thanks to xenon light they are able to recognize obstructions on the road sooner. -69% of all xenon users would certainly recommend xenon light to other drivers for their next vehicle. -66% of all xenon users deliberately chose to equip their vehicles with this option in order to improve vision at night and in poor weather conditions. -64% of all xenon users believe xenon light to be so good that it should be standard on all vehicles. -61% of all xenon users feel safer with xenon light.

There are three different methods that are currently used to focus the emitted light to a desired beam pattern, stepped reflectors, variable-focus (stepless) reflectors, and poly-ellipsoid system (PES). Stepped reflectors and variable-focus reflectors are known in the industry as reflector headlights and a PES is known as a projection-beam headlight. The quality of a stepped and variable-focus reflector headlight is proportional to the size of the reflector. Therefore, to get a reflector headlight with a high efficiency (measure of how much light emitted from the bulb is reflected outward) you must have a large reflector, which corresponds to a large headlight. The projection headlights use a similar reflector as the variable-focus reflector headlights, but in addition use a lens to focus the beam. This results in a headlight that is much smaller in size. The effective projection surface can be as small as 28cm2 and provide a better beam than much larger reflector headlights having an area of 200cm². Our design utilizes a projection beam headlight because of the limited space available in a motorcycle fairing. There is not enough space to maneuver a reflector headlight in the headlight compartment. Utilizing the smaller projection beam leaves enough room for the light itself and the maneuvering mechanism. Another advantage of a projector beam is that it uses an imaging screen to create the dark/light cutoffs that correspond to the beam’s geometry. These can be precisely engineered to create different beam geometries. The imaging screen also allows the edge of the beam to either have a sharp cutoff or fade from light to dark. Another reason for using a projection beam headlight is that it coincides with current motorcycle styling.

Figure 7-16a: Reflector Headlight (Honda RC51) Figure 7-16b: Projector Beam Headlight (Honda CBR900)

Figure 7-16a is an picture of a motorcycle with two reflector headlights and figure 7-16b is a picture of a similar motorcycle with four projection beam headlights. The four projection beam headlights take up less space than the two reflector headlights.

7.8 Demo-Stand A demo-stand was created to showcase our finished prototype. It consists of a box that holds some of the electronics as well as the 12-volt battery and a pivoting arm that acts as the motorcycle. The arm acts as the motorcycle for demonstration purposes. The box contains the speed sensor and motor as well. The speed sensor motor velocity is varied by supplying different voltages by way of a variable DC power supply, which is external from the box. The headlight assembly, inclinometer, and micro-controllers attach to the end of the pivoting arm. As the arm pivots the inclinometer senses the movement and the headlight assembly reacts to the lean. Switches control the power to the headlight and distribution block. An inline fuse is added to each switch to ensure that incase of a short, neither the headlight nor the electronics will be damaged. Small lights are also attached to the switches to inform that power is being supplied.

8.0 COST The prototype cost of the combined mechanical and electrical projects, is about $585.00. This cost reflects the cost of parts only; no labor costs were acquired. In a mass production scenario this cost is expected to be lower.

Part Quantity Unit Cost Cost Mechanical Components Headlight 1$ 15.00 $ 15.00 Servo 2$ 99.99 $ 199.98 Bearings 3$ 6.33 $ 18.99 1.00" Gear 1$ 10.90 $ 10.90 1.75" Gear 1$ 14.44 $ 14.44 Drive Belt 1$ 1.92 $ 1.92 Drive Pulleys 2$ 3.00 $ 6.00 Aluminum Bar Stock 1$ 30.48 $ 30.48 Aluminum Sheet Stock 1$ 16.50 $ 16.50 SUB TOTAL $ 314.21 Electrical Components Basic Stamp 1$ 59.00 $ 59.00 Servo Controller 1$ 45.00 $ 45.00 Voltage Regulation Electronics 1$ 25.00 $ 25.00 Control System Enclosure 1$ 10.00 $ 10.00 Misc. Wire & Connectors 1$ 5.00 $ 5.00 Speed Sensor 1$ 5.00 $ 5.00 Tilt Sensor 1$ 20.00 $ 20.00 Gyro 1$ 100.00 $ 100.00 Timing Chip 1$ 1.50 $ 1.50 SUB TOTAL $ 270.50 TOTAL$ 584.71

Figure 8-1 Prototype Cost

9.0 CONCLUSION To increase a rider’s safety during nighttime riding, we found it necessary to increase the rider’s view while cornering. In order to do this, a system to control headlight aim should be implemented. We determined that accurately predicting the motorcycle’s dynamic situation on a roadway only requires the input of a few sensors to determine the bank angle and the velocity. Once these two inputs are known, it is simple to obtain some detail about the current turning scenario. A micro controller and algorithm can accomplish the implementation of this knowledge and manipulate a two axis headlight aiming device to properly aim the beam of a headlight The proposed design will solve the two major issues that cause decreased frontal illumination while cornering a motorcycle at night. The motorcycle’s banking causes the first problem, and the second is the improper aim due to the corner geometry. The design will correct for the bank angle of the motorcycle by correctly orientating the beam so that its shape maximizes the illumination area on the road and also shift the beam to the left or right so that it illuminates where the rider should be looking to corner safely.

10.0 EVALUATION OF WORKING EXPERIENCES 10.1 Electrical Computer Engineering Group Our capstone experience was unique this year in that we were the only Mechanical Industrial Manufacturing Engineering (MIME) capstone team to work in conjunction with a capstone team from the Electrical Computer Engineering (ECE) department. Working with the ECE team presented many challenges yet also provided opportunities not available to other MIME capstone groups. As our project had a clear division between the electrical and mechanical design aspects, it was easy to assign responsibilities and tasks to each group. There were several advantages to working with the ECE capstone team. One major advantage was the eligibility to work on larger more extensive projects. It would not have been practical for a single MIME or ECE group to attempt to complete this project exclusively. Working with the ECE group allowed us to pursue our idea of the adapting motorcycle headlight, which appealed to us because without their partnership it would not have been possible. This collaboration between departments is beneficial because it forms opportunities for capstone teams to engage in multi-faceted projects where they are forced to rely on another team to complete elements of the project where they do not possess the skills or knowledge to do themselves. This is a more “real-world” scenario than the existing capstone philosophy of a single group completing a project in one discipline. Another advantage was the exposure to a different discipline of engineering. Although we were not directly involved with the design and fabrication of the circuits and other components for the control system, we had a first-hand look into what it entailed and consequently have a better understanding of electrical design. Another area that mechanical engineers don’t often get involved in is programming and algorithm development. The development of the control system algorithm was a joint task between both groups in which the interaction between both was advantageous when resolving problems. The ECE group members were more fluent in programming and common software syntax, but many abstract ideas from the MIME group members brought about more efficient ways of solving problems in the code. There were also a few disadvantages of working with the ECE group. First and foremost was the difference in schedules between the MIME and ECE departments. During the first quarter of the capstone course the MIME department had a more aggressive schedule, consequently we felt the ECE group was lagging behind. Although the ECE group seemed to catch up early in the second quarter of the course, it would have been better to work at the same pace, and towards similar goals through the duration of the course. If this collaboration between departments were to continue, a main improvement would be to better coordinate between course advisors and develop a common set of objectives for both teams to work towards during the course. This would aid in the timely cooperation of the groups to accomplish common milestones. All in all, the advantages and experience gained from working with the ECE group far outweighed any disadvantages or setbacks that we came across. We as a team hope that the college of engineering will encourage this type of inter-departmental cooperation in the future of the capstone design program.

10.2 Business Group Our group also collaborated with a business group consisting of three students in the college of business. Initially a good camaraderie was felt between all the groups and the introduction to our project was well received. Expectations were high and much enthusiasm was felt all around as ideas were spread. From the beginning it was not our intent to apply for a patent outside of the university and receive funding from venture capitalists to start a company. But it seemed as if this was the primary intent of the business group. Even after we specifically stated that we did not want to proceed in this route the business group disregarded our recommendation and decided to research this in some depth. Following discussions with our engineering advisors and the Northeastern University Technology Transfer Office, it was made clear that obtaining a patent outside of the university was not only frowned-upon, but against university policy and possibly even illegal due to financial reasons. After knowing this, the business group continued to favor the idea of receiving outside funding to start a company and receive a patent separate from the school. We continually rejected the idea and wished to apply for a patent through the school since all expenses would be covered. Because of these discrepancies between the groups, actual goals were set out much too late in the quarter and most were never realized. The majority of this stress would have been relieved had the business advisor been aware of Northeastern University policy in such situations and stayed in better contact with all three groups instead of focusing mainly on the business group. However, not all problems originated with the business group. It was difficult for us to spend much time with the business group as well as the electrical group on a weekly basis due to everyone’s busy schedules. Overall the collaboration would have been smoother from the beginning if we had clearly stated our goals and help set forth a business plan outline to follow. Had we been introduced to the business group during the first capstone quarter, more goals would have been set forth and achieved. The idea of merging the groups has merit. As time goes on and more organization is implemented, it will be an excellent real world opportunity for students sometimes possibly lucrative.

12.0 REFERENCES 1. Accident Reconstruction News, “Valeo Secures First Customers for Intelligent Headlight Technology That Turns Light into Road Bends”, www.accidentreconstruction.com/news/sep-01/092001a.asp, September 2001 2. Alphen, “Headlight System for a Motorcycle”, US Patent Number, 3939339, February 1976 3. Alphen, “Headlight Systems for Motorcycles”, US Patent Number, 4223375, September 1980 4. Alphen, “Lighting Systems for Motorcycles”, US Patent Number, 4075469, February 1978 5. Analog Devices, “Using the ADXL105 in Headlamp Leveling Systems”, www.analog.com/l-ibrary/applicationNotes/mems/HEADlevel.pdf, December 1999 6. Birch, Stuart, “Adaptive Front Lighting”, Automotive Engineering International, December 2001, pp. 39-42 7. Bortoluzzi, D., Doria, A., Lot, R., “Experimental investigation and simulation of Motorcycle Turning Performance”, www.mecc.unipd.it/~cos/dinamoto/torquewww/steeringtorque.htm Department of Mechanical Engineering, University of Padova 8. Bosch, Robert, “Lighting”, Bosch Automotive Handbook, Bentley Publishers, October 2000, Paperback, 5th ed., pp. 700-705 9. CFX Technologies, “A Guide to Accelerometer Selection”, www.cfxtech.com/how.htm 10. Cossalter, Vittore, “The Gyroscopic Effects on a Motorcycle”, www.dinamoto.mecc.unipd.it, November 2001 11. Federal Motor Vehicle Safety Standards No. 108. Code of Federal Regulations, Title 49, Volume 5, Parts 400-499. Revised October 1, 1999. 12. Hatanaka et al., “Headlight Control Apparatus for Motorcycles”, US Patent Number, 4870545 September 1989 13. Hella KG Huech & Co., Xenon Headlamps, www.hella.com, February 2002 14. Hibbeler, R.C., “Mechanics of Materials” Prentice Hall, 1997, Third Edition. 15. HVW Technologies, All About Servos, www.hvwtech.com/servos_allabout.htm, 2000 16. Jones, “Motorcycle Headlight Aiming Device”, US Patent Number, 5426571, June 1995 17. Jones, “Simplified Inertial Bank Angle Sensor”, US Patent Number, 5811656, September 1998 18. KVH Industries, E•Core Technology, www.kvh.com/pdf/ECoreTech.pdf 19. Marshall Brain’s How Stuff Works, “How Gyroscopes Work”, www.howstuffworks.com/gy-roscope.htm, 2000 20. Miyauchi et al., “Road Surface-Sensitive Beam Pattern Leveling System for a Vehicle Headlamp”, US Patent Number, 4868720, September 1989 21. Piezo Product Engineering, “Application Guide For Gyrostar (Piezoelectric Vibrating Gyroscope)”, www.murata.com/murata/murata.nsf/appguides/$file/gyrostarappmanual.pdf, August 2001 22. Research Note DOT HS 809 360, U.S. Department Of Transportation , National Highway Traffic Safety Administration, October 2001. 23. Skoff, “Cornering Light System for Two-Wheeled Vehicles”, US Patent Number, 4024388, May 1977

APPENDIX A

APPENDIX B

APPENDIX C

APPENDIX D