View of Chassis Without Top Body…..………………………………………………………………………….20

UNIVERSITY OF CINCINNATI

Date: 8-Nov-2010

I, Kovid Mathur , hereby submit this original work as part of the requirements for the degree of: Master of Science in Mechanical Engineering It is entitled: Conversion of a Hybrid Electric Vehicle to Drive by Wire Status

Student Signature: Kovid Mathur

This work and its defense approved by: Committee Chair: Manish Kumar, PhD Manish Kumar, PhD

Ernest Hall, PhD Ernest Hall, PhD

Janet Dong, PhD Janet Dong, PhD

11/11/2010 1,200 Conversion of a Hybrid Electric Vehicle to Drive by Wire Status

A thesis submitted to the Division of Research and Advanced Studies of the University of Cincinnati

In partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE In the Department of Mechanical Engineering of the College of Engineering 2010

By Kovid Mathur Bachelor of Engineering (Mechanical Engineering) Visvesvaraya Technological University, 2005 Committee Chair: Dr Manish Kumar Abstract

With advancements in the automotive driving and safety technology the new age is looking to redefine transportation as we know it. The thrust area of study at the Center for Robotics

Research at University of Cincinnati is building technology for autonomous vehicles and it has made considerable advancements over the years to building the future car.

In summer 2006, Defense Advanced Research Projects Agency announced the third Grand

Challenge which would feature ground vehicles executing “simulating military supply missions safely and effectively in a mock urban area”. The center entered the competition with a team of students and researchers to achieve this goal with generous contributions from Tank

Automotive Research Development and Engineering Center (TARDEC), Applied Research

Associates Inc (ARA) and the University of Cincinnati amongst others.

An all terrain hybrid electric vehicle built by Cal Motors as an economical non tactical base transport vehicle was used as the competition entry, which was donated as per a Co-operative

Research and Development Agreement (CRADA). This thesis presents the drive by wire solution along with the custom changes which were made on the vehicle in order to put the till now theories into practice.

The design solution introduced control of linear actuators by more responsive and energy efficient servo motors which were driven by a Galil™ motion controller. Each axis of the controller was responsible for the control of electronic braking, steering and speed control systems respectively. The process involved some metal fabrication to incorporate the positioning of components for improved space usage and definite mounting, after which the

iii systems were calibrated for optimum functioning. A series-hybrid approach was introduced for the ATV to provide longer hours of operation. Before the vehicle was allowed to ply on city streets it was brought to Ohio state law standards and in addition underwent a thousand mile durability test.

The result of the research and development was a robust and effective system which could control by wire the all terrain vehicle (ATV) and met all primary goals of the project.

Acknowledgement

My thesis work at the University of Cincinnati is the amalgamation of many people’s effort all through my life. I consider myself very fortunate to have really good advisors and teachers to whom I owe this work. They have at every step helped me build a broader perspective and have provided me with many opportunities to enhance my talent for engineering and design. I would like to acknowledge the following people for their effort towards this work:

Dr Ernest Hall for his remarkable direction and constant encouragement which got me through even in the toughest of times.

Dr Manish Kumar and Dr Janet Dong for their unprecedented encouragement and support.

Saurabh Sarkar , Scott Reynold and Ray Scott who as friends and colleagues helped me in my undertakings and decision making.

Gaurav, Hem and Shuchi Mathur my immediate family, who believed in my abilities and supported me all through my education.

Vishal Mathur, my cousin without whose love and support, I would have never achieved my goals.

Finally I would like to express my profound appreciation for my fiancé Marietta for her encouragement, understanding, and patience even during hard times of this study.

Table of Content

Abstract…………………………………………………………………………………………………………………………………….iii Acknowledgements …………………………………………………………………………………………………………………vi 1. Introduction…………………………………………………………………………………………………………………………1 2. Literature survey………………………………………………………………………………………………………………….6 2.1. By wire system……………………………………………………………………………………………….……….…….6 2.2. Braking system……………………………………………………………………………………………….…………….9 2.3. Steering system…………………………………………………………………………..………………………………12 2.4. Future developments…………………………………………………….……………………………………………16 3. Reverse Engineering…………………………………………………..………………………………………………………17 3.1. The Hyrider…………………………………………………………………………………………………………………18 3.2. The Structure………………………………………………………………………………………………………………21 3.3. Batteries…………………………………………………..…………………………………………………………………23 3.4. Battery charger……………………………………………………………………………………………………………25 3.5. Suspension system………………………………………………………………………………………………………25 3.6. Traction motors..…………………………………………………………………………………………………………26 3.7. The Brakes……………………………………………………………..……………………………………………………26 3.8. Hybrid conversion……………………………………………………………………….………………………………28 3.9. Street legal..………………………………………………………………………………………………..………………31 3.10. Lighting…………………………………………………………………………………..………………………………35 4. The thousand mile test………………………………………………..…………………….………………………………39 5. Steer by wire solution………………………………………………………………………………………………………..43 5.1. The design…………………………………………………………………………………………………………………..43 5.2. Computer control of steering………………………………………………………………………………………50 6. Brake by wire solution……………………………………………………………………………………………………….53 6.1. The design…………………………………………………………………………………………………………………..55 6.2. Computer control of brakes………………..………………………………………………………………………57 7. Conclusion………………………………………………………….………………………………………………………………61

vii

8. References……………………………………………………………..………………………………………………………….63 9. Appendix A…………………………………………………………………………………………………………………………67 9.1. Jeep electrical wiring documentation……………….…………………………………………………………67

viii

List of Figures

Figure 1: Figure 1: Multiple redundancy schematic..………………………………………………………………….8

Figure 2: View of chassis without top body…..………………………………………………………………………….20

Figure 3: Modular construction of the chassis. ………………………………………………………………………..20

Figure 4: Heavy duty Batteries…………………………………………………………………………………………………21

Figure 5: The suspension system and traction motor……………………………………………………………….26

Figure 6: A schematic diagram showing routing of brake lining. ………………………………………………27

Figure 7: The two master cylinders coupled into one single unit. …………………………………………….27

Figure 8: Parallel configuration for hybrid vehicles. …………………………………………………………………29

Figure 9: Schematic diagram showing charging of battery pack with a generator…………………….31

Figure 10: General Street legal requirements as per Ohio DMV……………………………………………….34

Figure 11: Installation of a battery stand and an electrical box. ………………………………………………36

Figure 12: Installation of a cooling fan for electrical box. …………………………………………………………36

Figure 13: Wiring schematic of lighting systems. …………………………………………………………………….37

Figure 14: Part 1- The thousand mile test on the city roads……………………………………………………..39

Figure 15: Part 2- The thousand mile test on the city roads……………………………………………………..40

Figure 16: Odometer reading before and after the thousand mile test…………………………………….41

Figure 17: Schematic diagram for steer by wire (design A) ………………………………………………………44

Figure 18: Engineering drawings for steer by wire (design A) ………………………………………………….45

Figure 19: Schematic diagram for steer by wire (design B) ………………………………………………………46

Figure 20: CAD drawing for Steering bracket (0.5” thick steel) ………………………………………………..47

Figure 21: Images to show the mounting of steering bracket…………………………………………………..48

Figure 22: Schematic diagram showing the electrical connections for the steer by wire………….51

Figure 23: Two master cylinders with two outputs for respective wheel set…………………………….54

Figure 34: 3/16” dia brake adapters…………………………………………………………………………………………55

Figure 35: Tools used for creating new brake lining………………………………………………………………….56

Figure 36: Using blow torch to assist flaring of brake tube……………………………………………………….56

Figure 37: Components introduced for brake by wire solution…………………………………………………57

Figure 38: Schematic diagram of electrical connections for electronic control of brakes………….58

Figure 39: Schematic diagram for computer control of braking by wire……………………………………60

List of Tables

Table 1: Technical specifications of the batteries……………………………………………………………………..22

Table 2: Battery charging specifications……………………………………………………………………………………22

Table 3: Charging time specifications……………………………………………………………………………………….23

Table 4: Battery charger technical specifications……………………………………………………………………..24

Table 5: Log sheet for the thousand mile test ………………………………………………………………………….41

Table 6: Values defining numerical position on each control unit…………………………………………….52

Table 7: Values on system corresponding to braking force requirement………………………………….59

Table 8: Dashboard to J1 - female Duel Row Header………………………………………………………………..65

Table 9: Fuze to J2 - female 2 P Single Inline Row…………………………………………………………………….65

Table 10: J1 to "Jeep" - male Duel Row Header………………………………………………………………………..66

Table 11: J2 to Jeep, Single Inline Row……………………………………………………………………………………..66

Table 12: Start relay to jeep, relay connector…………………………………………………………………………..67

Table 13: Brake to Jeep, Screwed Fork Terminals…………………………………………………………………….67

Table 14: J1 to "Jeep" - male Duel Row Header………………………………………………………………………..67

Table 15: Traction to Jeep - female 3 row special…………………………………………………………………….68

Table 16: Key relay to jeep, relay connector…………………………………………………………………………….68

Table 17: Traction to Jeep - female 3 row special…………………………………………………………………….69

Table 18: Throttle to Jeep - 6 Pin Duel Row Header………………………………………………………………….69

Table 19: Terminal Strip……………………………………………………………………………………………………………70

1. Introduction

In 2009, the National Highway Safety Administration1 estimated nearly 33,936 lives lost in auto accidents as compared to the 42,708 killed in the year 2006. This 8.9% reduction in number was due to improved safety features automobile companies all over the world have been introducing into the new age vehicles. These features are mainly systems which take away control from the driver and automate those processes reducing the number of variables a driver needs to control.

The arguments which support automation of vehicles are three fold. The first being that, in today’s traffic driving is a very stressful activity. More and more vehicles are being used to cater to the needs of the ever growing population, which inevitably increases traffic congestion leading to road rage. The BBC channel suggested 95% of all accidents on road are caused due to human error which is why it makes good sense to remove the human equation from the vehicle’s control system which will lead to reduced numbers in accidental statistics. Lastly, automation is a compelling feature which can increase the desirability of a product which will lead to improved sales and is good for the industry from an economic point of view.

Already major manufacturers have announced radical ideas in this area and their R&D teams have done some ground breaking work in developing systems which are being slowly inoculated into the newer vehicle models. Some technologies have already been perfected to a level which makes them almost a basic feature in most new cars which roll down the assembly

line. Route planning and navigation, cruise control, automatic braking system, automatic parallel parking etc are just a few examples of these advancements.

Automation has come a long way now, when humans can choose to send robots to places which are hazardous or life threatening and have them make intricate moves without any danger to human lives. The National Defense Authorization Act for Fiscal Year 2001 stated that

“It shall be a goal of the Armed Forces to achieve the fielding of unmanned, remotely controlled technology such that… by 2015, one-third of the operational ground combat vehicles are unmanned.” With such a resolution to provide safety to human lives on the battle field, the

Defense Advanced Research Project Agency (DARPA) conducted 2 Grand Challenges (2004,

2005) with the goal of bringing researchers from all over the world to building technology for unmanned ground vehicles (UGV). These robots would require a very complex mesh of sensors and algorithms in order to make split second decisions based on the environment and situations. In a controlled environment, researchers over the years have developed a good amount of technology to achieve certain level of repeatability. DARPA planned to add real world factors such as inclement weather, poor visibility due to nightfall, complex terrain and routes etc in order to simulate actual war conditions in order to test the robustness and practicality of the design at realistic speeds (15-20mph).

Following were the goals of the Grand Challenge as specified by DARPA in a report sent to the

Congress:

• Accelerate autonomous ground vehicle technology development in the areas of sensors, navigation, control algorithms, hardware systems, and systems integration. These areas are important to autonomous ground vehicle operations.

• Demonstrate an autonomous vehicle able to travel over rugged terrain at militarily relevant speeds and distances. A successful technology demonstration could shift perceptions within the technical and operational communities.

• Attract and energize a wide community of participants not previously associated with DoD programs or projects to bring fresh insights to the autonomous vehicle problem.

The two competitions as predicted created waves and were a huge success. This led to DARPA announcing the Urban Challenge to be held in 2007 which would require autonomous vehicles to maneuver in a “mock city environment, executing simulated military supply missions while merging into moving traffic, navigating traffic circles, negotiating busy intersections, and avoiding obstacles.”

Setting our goal to making innovative designs, algorithms and technology for an Unmanned

Ground Vehicle (UGV), the University of Cincinnati entered the competition as “Cincinnati

Bearcats” with an all terrain hybrid electric vehicle. The vehicle, a product from Cal Motors was presented to the Center for Robotics Research as part of a CRADA by TARDEC-NAC and was perfect to achieve the team’s objectives for the following reasons:

1. Being an electric vehicle, it had an advantage of being programmable as most of the

systems already ran on electric signals.

2. The prototype vehicle was built taking into account future manipulations in the design

and hence had incorporated enough space under the hood and elsewhere for new

installations.

3. Since the vehicle’s body could be dismantled completely and separated from the

chassis, it was a good educational tool to understand the functioning of the ATV.

A multi disciplinary team of graduate and undergraduate student came together to work on the various modules of the ATV. This thesis will be outlining the various works done on the vehicle before the algorithms for sensor control could be tested for real world compliancy.

The document has been divided into subdivisions which explain the various stages during the development stage. Chapter 2 consists of a literature review. It will briefly explain the main technologies which have been worked upon in this research work and also give an outlook to the latest developments in the respective field. Chapter 3 consists of the details of the reverse engineering done on the Hyrider in order to understand its functionality and working. It will also outline the installations made and various works done on the vehicle to bring it to safety standards. Chapter 4 will dive into the steer by-wire solution which was custom built for this vehicle and give a brief on how computer control was achieved over this module. Chapter 5 will deal with the brake by wire solution and will also discuss its computer control briefly.

This work is just a small step towards building completely autonomous vehicle. It won’t be long before humans would only be required to only monitor the operations while the high-tech vehicle’s automation unit performs complex moves and plans routes on its own.

2. Literature Survey

2.1 By wire system

In recent times, the by-wire technology is featured in many machines such as industrial vehicles, farm machinery and factories. However, the modern aircraft epitomizes its application. Flying has always been a labor-intensive task before the introduction of the fly-by- wire technology. The pilots were responsible for taking split second decisions and thereafter implementing them by manipulating mechanical linkages, which can be a very physically draining activity. With much at stake there was a dire need to provide a technology, which would alleviate the pilot’s responsibility of physically actuating the controls.

The term by-wire means each mechanism in the system is electronically controlled. Electrical signals are used to communicate, eradicating the use of mechanical linkages and hydraulic pipelines, which statistically speaking were the main reasons for aircraft failures in the past.

Movement like pitch, roll, and yaw were no longer required to be controlled through mechanical linkages. In the 1960s, the Boeing Company brought this idea into the market with the F15 Strike Eagle. Later in 1974 the F16 fighter jets introduced the first fly-by-wire system without any fall back mechanical system. After years of research, Airbus A320 implemented the first commercial fly by wire system in 1988. These systems brought to the table, high performance controls which were capitalized by aircrafts like the Lockheed Martin F-117

Nighthawk, which are inherently unstable.

In the new age of digital electronics fly by wire has revolutionized even further. Digital fly by wire has taken over which is similar to its analog counterpart in functionality, except that here computers handle the signal processing. The added advantages are the increased electronic stability and flexibility as programmable computers can receive inputs from the aircraft sensors and process them as per the developed algorithm to send out the final command. The lightening speed response assists in solving and formulating appropriate command signals that alters flight control according to the pilot’s intention. The programming of the digital computer is what essentially protects the “flight envelop”. Flight envelope is a term used to define the limitations of an aircraft given its aerodynamics and structure, taking into consideration the factors of safety. For example, when the system is active, it will prevent the pilot from exceeding preset limits with reference to limiting G force, stall, spin etc. It can also be used to filter pilot induced oscillations etc.

In spite of the fly-by-wire technology having multifold advantages, in the beginning there were some real challenges that opposed the design. Possibly the most important breakthrough was the “development of the failure survival technologies to enable high-integrity system to be implemented economically with the required safety levels, reliability and availability” 2.

Vehicles with critical modules being controlled by wire require the driver to remain in control even if one or more parts of the control system fail. During the initial development stages introducing a fall back control system would mean mechanical controls to be employed, which

pretty much defeated the purpose of having electronic controls. To maximize the by wire advantage, systems with multiple redundancies was introduced for safety2.

Function Function FunctionC

Joystick

Motion Computer Sensors Controls Actuators

Figure 1: Multiple redundancy schematic

Figure 1 shows three level of system redundancy. It depicts how 3 independent actuators signals are used to drive the controls. Output from each actuator is compared with the others and if there is significant difference in the values, the faulty actuator is bypassed3. This comparison method acts like a feedback loop that keeps track of system functioning.

For safety in a drive by wire system, multiple levels of redundancy is a requirement. This would ensure that the operator retains control of the vehicle even under partial system failure.

Following is a review on the drive by wire technology, which is the basis for this research work.

2.2 Braking system

Automotive braking essentially converts the kinetic energy of a vehicle into heat and thereby decelerating and eventually bringing the vehicle to a stop. Until recent times, the most commonly employed technique to achieve this was by using hydraulic braking.

The system consists of five major components namely the brake pedal, the master cylinder, hydraulic fluid, the brake lines and in the end the module which actually provides the braking effect on the wheels. The mechanism is actuated when the brake pedal is pressed which in turn transfers the mechanical force to the master cylinder with the help of linkages. The piston in the master cylinder moves due to this force, pushing the hydraulic oil/fluid that is stored in the oil reservoir into the brake lines thereby transferring the energy from the brake pedals to the braking modules (calipers). The calipers use this transferred energy to bring the brake pads in contact with the brake discs. The frictional force caused between the pads and the disc transforms the kinetic energy into heat energy and in turn reduces the speed or stops the vehicle depending on the amount of energy transferred. The handbrake also works on the same principle except that it uses cables and not hydraulics to activate the rear wheel brakes. This also acts as a backup system in case the hydraulics fails4.

This type of braking system is very commonly found in vehicles today. There have been many improvements and innovations made to the system one of which is the brake booster which helps to reduce the force required to actuate the pedal for braking.

Although pure electronic braking has not been implemented onto production vehicles yet, a lot many hybrid solutions have already found their way into the market. One such example is the

“Sensotronics Brake Control” 5 introduced by Mercedes Benz in collaboration with Bosch in

2001. This system uses a conventional hydraulic braking system but has a unique subsidiary microcomputer that works in collaboration to calculate the driver’s brake input. Various sensor data are collected and computed, which bring in the actual driving condition parameters to get an optimum brake pressure value for “each” wheel. This customization of braking effort for each wheel provides most favorable braking requirements leading to a stable braking operation. Essentially this technology is still a hydraulic system but with an ancillary electronic system which does not make it an entirely electronic.

Automotive industry giants like Bosch, Siemens and Continental have been working to develop electro mechanical brakes that use electric motors to transfer energy6 to the brake pads. Such systems are essentially independent modules installed at each wheel. Although being separate, their operation is tied eventually to the driver’s input at the brake pedal. Electrical signals are used for communication of commands and a compact electric motor and gears unit at each wheel replaces hydraulic actuation14.

This system eliminates the use of sealed master cylinders, hydraulic brake lines and the brake fluid reservoir. This not only makes the braking unit more compact, it also makes it more reliable unlike the hydraulic pressure routing system, which is always susceptible to leaks and failures. The system can easily implement active braking (actuation of each brake individually)

with a much lesser complex arrangement unlike a purely mechanical system. Anti-lock Braking

Systems (ABS), Active Braking (AB), collision avoidance, etc. can all be implemented through this system easily because electrical systems can now be directly sent to the brakes for operation.

Less hardware use in electromechanical braking is one of the biggest advantages of the system.

This brings down the weight as well as the cost of production of each unit, not to forget the reduced cost of maintenance due to less mechanical linkages. Moreover, it also reduces the environmental impact by eliminating the use of hydraulic fluids.

Here is a summary of all the advantages of electromechanical braking systems:

 Ability to tailor the system’s characteristics at each point in the vehicle’s envelope.

 Increased capability of fault monitoring and diagnostics.

 Use of purely electromechanical systems allows for the elimination of environmentally

hazardous hydraulic fluids.

 Reduced maintenance costs resulting from the reduction in mechanical complexity.

 Reduced operational costs, through improved maintainability and higher dispatch

reliability.

2.3 Steering system

The steering mechanism on vehicles has developed immensely over the years. From being just a simple combination of linkages, these days many innovative technologies have been developed and introduced to enhance the steering experience.

The main objective of the steering mechanism is to control the heading of the vehicle. To achieve this, the steer by wire concept was introduced which works on very similar principles as the brake by wire technology as discussed earlier. In addition to providing ease in steering, it also removes the mechanical interface between the driver and the mechanism that actuates turning of the wheel13. The main advantage this leads to is the increased level of safety of the driver in case of a frontal impact, which under severe circumstances can force the steering column towards the driver’s body, causing extensive damage and perhaps fatal injuries.

The steering assembly does a lot more than just provide a heading for the vehicle. Apart from precision control over the direction of the front wheels it also plays a crucial role in the absorption of intrusive shocks and bumps7.

Most of the steering systems currently existing in the market are made up of a few basic components- the steering wheel, steering mechanism, a track rod, the tie rods and finally the steering arms. The final aim of any type of steering system is to move the track rod from left to right. The tie rods are essentially provided to allow the movement of the suspension and also for adjustments in the steering geometry.

One of the most common steering mechanisms found in vehicles is the rack-and-pinion type system. As the steering wheel is rotated the movement is transferred into the upper column, which further transfers the motion to the pinion gears with the help of a couple of universal joints. The rotational movement of the gears is converted into linear movement of the rack, which thereby moves the track end to the left or right. Thus, the movement of the steering wheel is transferred to the wheels in case of a steering system without power assistance.

There are different electronic controls available for the steering operation as well. The latest technological advances have been made in developing a completely electronic mechanism in which motors are installed at the wheels that actuate the direction in which the vehicle needs to head8. This removes from the equation a lot of mechanical components that reduces the weight of the vehicle and along with it the maintenance cost for the mechanics involved. Making the vehicle lighter increases its speed and also it responsiveness to the steering commands. The motors get their commands through the ECU (Engine Control Unit) that can be programmed for different kind of operations. Since the commands are electronic in nature it makes it easier to integrate the system to an algorithm for autonomous operation that can direct the vehicle’s heading as per the sensor inputs.

Power steering is a very common feature in modern vehicles. These mainly consist of a hydraulic system, which takes its power from the engine and assists in reducing the driver’s effort in turning the steering wheel. Electro-hydraulic power steering is an advanced modification of such systems that utilizes an electric powered pump, which works in tandem

with the hydraulic system to provide different levels of assistance as per the requirement. In order to remove the hydraulics from power steering mechanism completely, some manufacturers have come up with the electric power assisted steering system.

This system is essentially what will probably be a part of a pure drive by wire steering mechanism. Since they can be controlled electronically, they can be easily programmed for computer control in autonomous operation.

Giving control of one of the main operations of the vehicle to electronics does require a very high factor of safety and also a system that must have multiple levels of redundancy to ensure that even if a part of the system fails, a backup system takes over to maintain control. This concept is again similar to the brake by wire criteria and an introduction of a separate electrical system dedicated to this operation is necessary for a reliable and cost effective implementation of electronic steering actuators 10.

For many years manufacturers have been working on developing by-wire technology that can be put into production for modern vehicles. Pursuing this objective, many concept cars have been built which displays the drive by wire concept in its fully functional form. The Bertone SKF

FILO is one such heralding accomplishment in which all major functions namely the brake, steering and speed control are controlled electronically. The vehicle has a control system akin to a joystick, which apart from controlling the steering, braking and speed control also has the gear shifting, and clutch actuation controls in built. As mentioned earlier, apart from providing

basic turning capabilities to a vehicle the steering mechanism also has a few other functions to perform. An important one is to send a feedback to the operator in response to the driving conditions. In the FILO, this is achieved by a high torque motor actuated with the help of commands, which are a function of the load that acts on the steering rack.

There are independent smart electromechanical brake actuators on each wheel of the FILO. The caliper system is electric and is similar to a conventional hydraulic counterpart in terms of functionality, but is more effective in terms of responsiveness and reliability. The activation of the brakes is a little different than conventional concepts, in which the driver has to squeeze the handgrips on the yokes. Since a smart electromechanical actuator individually controls each brake, the braking force may vary according to the driving conditions to provide optimum response. To keep the driver aware of the functioning of the brakes, the system deploys progressive resistance when activated and also provides a considerable free play to remove unintentional braking.

By wire technology is not only a replacement of mechanical linkages and hydraulic lines with an electric motor. An algorithm has to be in place which firstly collects inputs coming from various integrated sensors and measuring units and then computes an optimum command signal for operation. The technology behind these sensors is beyond the scope of this thesis work but is an important and integral part of any drive by wire system.

2.4 Future developments

With the advancements in the field of digital signal transmission such as optical fibers, it is but natural to assume that the next step in by wire technology will be introduction of something which is termed as fly by optics. The biggest advantages of such systems will be the extremely high speeds of communication and the fact that such systems will be immune to electromagnetic interferences. The system will be lighter in comparison and would work with a much faster response time to the data generated by the controller. This theory is also sometimes referred to as “fly by light” due to the use of fiber optics.

Chapter 3: Reverse Engineering

The US Army comprises of vehicles which include land combat as well as transportation vehicles, which are used heavily during war and peace operations. Use of tactical vehicles such as the Hummers for transportation of people or parcels is not the best use of resources and therefore the US Army’s National Automotive Center commissioned a light duty vehicle for this purpose. CalMotors™ and Quantum Technologies™ combined efforts to build such a vehicle which they called the “Hyrider”.

According to the Co-operative Research and Development Agreement (CRADA) with the Tank

Automotive Research Development & Engineering Center (TARDEC) and Applied Research

Associates Inc (ARA), the University of Cincinnati received a Hyrider as a test bed to work on future autonomous vehicle technology. “The purpose of the CRADA was to perform system design and integration of a new autonomous vehicle that would integrate advanced hybrid electric technologies with advanced autonomous robotic systems…The main benefits of this effort would be a demonstration of a full sized future concept vehicle equipped with sensors for

GPS navigation and obstacle avoidance. This will establish a baseline capability of autonomous operations.”

The team now had access to an electric vehicle on which all future developments would be applied and tested. In order to build on this base vehicle, it was important to reverse engineer the machine and understand its functioning. This section comprises of a brief explanation of the vehicle’s documentation, main components and general modifications which were made during the initial stages of the research process.

3.1 The Hyrider

The external structure of the first few prototypes of this vehicle were built with fiberglass with the intention that depending on the specific application and volume the exterior body could be replaced by structures stamped out of steel, aluminum or even molded plastic. This idea takes advantage of the vehicle’s design of having a modular space frame chassis which houses all the main components for basic functioning. This allows for the rest of the vehicle’s body to be replaced by any design suiting the desired purpose of the vehicle. This design also allows for easy removal of panels for servicing or hauling long cargo. The three initial purposes as intended by the manufacturers were:

1. Civilian,

2. Armored military &

3. Military.

3.2 The Structure

In order for the team to understand and document the vehicle’s working it was necessary to take the top structural frame off the vehicle’s chassis. As per the manufacturers intention, this gave access to all its components such as the batteries, the charging unit, the traction motors etc in order to understand their specifications as well as method of integration into a single functioning unit. In order to achieve this, the fiber glass body was detached from the chassis which was secured with heavy duty nuts and bolts. An overhead crane was used in order to lift the frame off the base.

After the body was removed the team worked towards documenting the components which gave an insight of the functioning of the vehicle. It also made our understanding better of how to integrate the autonomous technology into the system. The electric throttle, brake system, battery charging unit and the steering mechanism were the key features which were studied intensively.

Figure 2: View of chassis without top body.

Figure 3: Modular construction of the chassis.

The chassis, built modularly has a central spine which carried the six 12 V batteries. The spine is designed to provide ample protection to the batteries in case of severe impact situations.

Although the batteries are well positioned in terms of their safety, accessing these batteries even for general inspection is very difficult. The only way is to pull the body off the chassis. For future reference, this activity will have to be repeatedly performed after every 3-4 years when the battery life is over as per manufacturers rating.

3.3 Batteries

The batteries are secured with the help of metal brackets which can be removed by removal of their securing nuts and bolts. The specification of each of these heavy duty batteries is listed in the following page.

Figure 4: Heavy duty Batteries

SPECIFICATION DESCRIPTION

Battery Model: D31T Nominal Voltage 12 volts High purity lead-tin alloy. Wound cell configuration utilizing proprietary SPIRALCELL® Plate Design technology. Electrolyte Sulfuric acid, H2SO4 Open Circuit Voltage (fully charged) 13.1 volts Internal Resistance (fully charged) 0.0025 ohms Capacity 75 Ah BCI: 155 minutes; (25 amp discharge, 80°F Reserve Capacity (26.7°C), to 10.5 volts cut-off) Length 12.813” Width 6.500” Height 9.375” Weight 59.8 lb

Table 1: Battery specifications

These batteries are specifically designed for heavy electric vehicles and can be used for starting and deep cycle applications. The manufacturer’s charging specifications as listed below.

Battery Charger 13.8 to 15.0 volts; 10 amps maximum; 6-12 hours (Constant Voltage) approximate 13.2 to 13.8 volts; 1 amp maximum (indefinite Float Charge time at lower voltages) Maximum voltage 15.6 volts. No current limit as long as battery temperature remains below Rapid Recharge 125°F (51.7°C). Charge until current drops below (Constant voltage charger) 1 amp.

Table 2: Battery charging specifications

The recharging time of these batteries depends on the charger’s characteristics and also the temperature. It is recommended to use only voltage regulated charger to ensure longevity of the battery life. An estimation of the charging times depending on the current values is listed as below:

Current Approx. time to 90% charge 100 amps 52 minutes 50 amps 112 minutes 25 amps 210 minutes Assuming 100% discharge – 10.5 volts

Table 3: Charging time specifications

The easiest method of determining if the batteries are fully charged is when the amperage drops below 1 amp during trickle charging.

3.4 Battery Charger

The vehicle comes with a smart battery charger inbuilt. This Delta-Q creation is a high reliability and performance unit which is specifically designed for charging battery packs in electric vehicles. It has a wide input voltage range from 85V-265V AC which allows it to be used for worldwide applications.

SPECIFICATION DESCRIPTION Charger Model: 913-72xx DC Output DC Output Voltage - nominal 72 volts DC Output Voltage - maximum 100 volts DC Output Current - maximum 12A Battery Type Specific to selected algorithm Reverse Polarity Electronic protection – auto-reset Short Circuit Electronic current limit AC Input AC Input Voltage 85 - 265 VAC AC Input Frequency 45 - 65 Hz Mechanical Dimensions 28.0 x 24.6 x 11.0 cm (11 x 9.7 x 4.3”) < 5 kg (< 11 lbs) w/standard output Weight cord Environmental Enclosure Enclosure: IP46 (NEMA4) Operating Temperature Range - 30°C to +50°C (-22°F to 122°F) Special Features Temperature Sensor on negative ring Battery Temperature Monitoring terminal PC-based configuration software for External Communications field programmability

Table 4: Battery charger technical specifications

The main manufacturing feature of the QuiQ chargers is the intelligent microprocessor controller, which with the help of its inbuilt memory can store up to 10 optimized charging algorithms. These algorithms built by the manufacturers are categorized according to the type of batteries, their sizes and chemistry. Field personnel can also develop, download and run new algorithms as per the requirements. These chargers are built for on board operations for harsh

environments. Its rugged make which comprises of a sealed enclosure and light weight characteristics is designed to provide continuous operation in any application. Due to these specific features this charger is mounted on the chassis itself where it performs under the dirtiest and wettest environment.

The charger comes with troubleshooting instructions which were required by the team to understand its functioning better. Working with these indications from the system, the condition of the batteries can be determined with specific details. This was very helpful during the testing of the vehicle.

3.5 Suspension System

The vehicle was intended to function in an all terrain environment and therefore it has long travel independent suspension system. It comprises of upper and lower A-arms and coil over shockers to give it proper support for rough terrains.

3.6 Traction Motors

The vehicle runs on two electric motors each rated for 5.7 HP and run on a 72V power supply.

These motors are mounted onto the chassis at special positions specifically fabricated for their

installation. The motor for the front wheel traction is mounted under the hood and the one for the rear is placed under the fiber glass body at the rear end.

7.5HP Electric Tractio n Motor Coil over shocker s

Figure 5: The suspension system and traction motor 3.7 The Brakes

The brakes system on the vehicle is a standard conventional hydraulic system with disc brakes on each wheel. The system has two master cylinder packed into one single unit and interlinked to the pedal through linkages. The cylinders individually are responsible for activating the brakes on either the front wheels or the rear wheels respectively. Each cylinder therefore has a separate brake line running from the piston end till the brake calipers on each end of the vehicle. A rough schematic of the arrangement is shown in the figure.

M1 M2

Master Cylinder Unit

Figure 6: A schematic diagram showing routing of brake lining.

Figure 7: The two master cylinders coupled into one single unit. 27

This feature of the brake design adds to the ease with which a by wire braking system can be integrated into the vehicle because of separate functioning of the master cylinders. Both cylinders, although separate have a single common brake oil reservoir. The brake line runs to the wheels along the chassis with the support of cleats. At the wheel end as mentioned earlier, there are conventional disc brakes installed.

3.8 Hybrid Conversion

The hyrider’s power train has many versions as built by Calmotors and the one given to the team is all electric. Keeping in mind the long hours of testing and the suggested duration of the final competition the team decided to work towards making the vehicle hybrid. This would add to the number of hours we could run the machine without recharging issues. Hybrid power trains are generally divided into two categories

1. Parallel hybrid &

2. Series hybrid configuration.

The parallel configuration requires a combination of the battery pack along with a combustion engine, which is connected to the mechanical transmission and works in tandem with the electric motors to drive the wheels. The advantages of this system are many folds. To begin with, the electric motor eradicates the requirement of a starter motor or an alternator.

Figure 8: Parallel configuration for hybrid vehicles.

Since there is a considerable source of electric supply integrated into the system with the help of the batteries, most of the accessories on the vehicle are powered with electric motors. This reduces the power requirement from burning of fossil fuel in the combustion engine which adds to the overall efficiency of the vehicle.

Parallel hybrids can be further categorized based on the manner in which the power from the two sources namely the electric motor and the combustion engine is physically coupled. A parallel hybrid in comparison to its counterpart requires a smaller battery pack due to the load sharing with the engine. The engine in such systems not only acts as a source of power to the wheels, but also helps in regenerative braking. This concept provides a very efficient use of the resources; provides higher mileage and is much suited for longer travel distances.

The Series hybrid runs only on traction provided by an electric motor. The advantage of using an all-electric propulsion system is its very high power to weight ratio. A well-suited motor can provide the wheels of a vehicle with a varying torques without a complex gear system in place.

This not only reduces the mechanical complexity, but also reduces weight of the machine for more power efficiency. The system uses a generator, which essentially just charges the batteries for the vehicle to run on all electric motors. This type of a system is also called as an

“electric transmission”.

After much deliberation the team opted to convert the hyrider into a series hybrid vehicle for the following reasons:

1. A generator to charge the battery pack would be a much cheaper investment as compared

to introduction of a combustion engine on board.

2. The integration of the combustion engine to work in tandem with the electric powered

wheels would require a much larger investment of time and resources which would lie

outside the scope of this project.

With these factors in mind the team started working on a series hybrid solution in spite of the fact that they are not as efficient as its parallel counterpart. In order to do this a 10KW power generator was installed at the rear end of the vehicle. This generator would supply power to a battery charging system, which would charge the 6, 12V batteries that supply power to the traction motors. Two lead wires were pulled out from the battery pack for this purpose and appropriate sections cut in the body of the vehicle to incorporate this design. The generator was secured by using L-shaped brackets and bolted onto the metallic chassis. This required drilling holes into the fiberglass body, which did not compromise the structural integrity of the vehicle itself.

+ -

+ - - + + - GENERATOR + - Battery Charger 10KW + - 72V

+ -

12 V

Battery Pack (12V Each)

Figure 9: Schematic diagram showing charging of battery pack with a generator

3.9 Street legal

Being a one of a kind prototype vehicle requires some legal and safety inspections before it is allowed by law to be driven on city roads. This required the non-titled, experimental, self- assembled vehicle to be inspected, titled, licensed and insured. The inspection has certain

requirements to be fulfilled and specific items checked which would give the vehicle a street legal status.

These items are listed below with a brief description of their minimum requirements:

1. Steering: The requirement for the steering assembly was to be safely secured (installed)

and operate normally without excessive play in the steering wheel.

2. Tires: The tires are required to have a minimum tread depth of 1/16th inch and they

should be free of major bumps and defects.

3. Brakes: The vehicle has to have primary brakes for slowing and stopping of the vehicle

along with an emergency braking system for stopping the vehicle when parked. These

systems were already installed on the ATV by the manufacturers.

4. Headlights: Two headlights installed on each side of the front of the vehicle is a

requirement for any motor vehicle. Although the headlights on the ATV were already

installed, they were yet to be wired and connected to a battery source for power. The

wiring of the vehicle will be explained in the subsequent topics.

5. Taillights: The rule requires every vehicle to have at least one taillight at the rear end

and two or more stop signals emitting red light. Again these lights, although were

already installed on the vehicle, needed to be wired into the electrical system. It was

also a requirement to install a white light to illuminate the rear registration plate.

6. Red reflectors: Reflectors are a requirement to be had at the rear end of the vehicle.

7. Turn signals: All vehicles must have turn signals, which are visible from both ends of the

vehicle. These again although installed, had to be wired to the electrical system.

8. Safety glass: Possible one of the most important requirement in terms of safety, the

windshield must be safety glass which is shatter proof, free of discoloration and cracks.

The team had to install a new windshield to conform to this pre requisite.

9. Rear view mirror: These were to be installed in a position, which would give the

operator an unobstructed view of the road to the rear.

10. Windshield wiper: To be installed to clean rainwater, snow etc from the windshield.

11. Horn and warning devices: To be installed which can emit an audible sound from a

distance of at least 200ft.

12. Flashers: A flasher was installed which would denote a disabled vehicle on the road. This

device was also intended to denote functioning of the vehicle under autonomous

operation to warn bystanders and team members.

13. Safety belts: All vehicles must be equipped with at least two safety belts for the front

seats.

Figure 10: General Street legal requirements as per Ohio DMV

The vehicle was built to serve as a transport vehicle and also for civilian use where the speed limit is not more than 35mph. We tested the vehicle to give us a maximum speed of 45 mph on full charge.

3.10 Lighting

The Hyrider was built as a prototype; therefore there were many functions which the vehicle did not perform. The lighting system was one such functionality which was not completely in place when the vehicle was given to the university. The vehicle although had all the lighting fixtures in place, they were still not wired into a single electrical circuit. This was not only a necessity for the safe operation of the vehicle but also a requirement for the street legal status.

In order to have the lighting fixtures functioning as intended, a wire harness was to be drawn and run along the whole vehicle to cover the front and the rear lighting systems into one single unit. The disadvantage of the vehicle being made out of fiber glass was that there was no common ground which incase of general production vehicles is the body of the vehicle. This added to the harness an extra wire running along from the rear till the front of the vehicle where the battery was installed.

An electrical box was installed under the hood of the vehicle in order to place all electrical wirings along with the fuse box at one place. This was also a requirement to protect the electrical systems from the inclement weather. Two cooling fan was also installed to protect the system from overheating. A battery bracket was installed which would house a battery for the lighting system only. L-shaped clamps were used to secure it to the chassis.

Figure 11: Installation of a battery stand and an electrical box.

Figure 12: Installation of a cooling fan for electrical box.

The wiring schematic can be seen in figure 22 below.

Figure 13: Wiring schematic of lighting systems.

A new metallic dash board was built to install various switches for control of the electrical gadgets. Special care was taken to make sure the ergonomics were right during the installation.

4. The Thousand Mile Test

The “thousand-mile test” was one of the requirements of the DARPA competition. This requisite was essential to determine the robustness of the vehicle itself in order to be able to perform at the competition. The objective was for the entry vehicle to prove its durability by running on its wheels for a thousand miles.

After the vehicle was licensed and insured its robustness was put to test by driving it around the university campus and nearby streets under changing weather and road elevation conditions. The vehicle on full charge would easily reach speeds of 45mph. There were certain limitations with the ATV which are common to any other electric vehicle. Longevity of battery charge being one of the biggest obstacles in trying to drive continuously for testing. It took longer for the battery pack to charge than to get completely drained out under constant operation, which would give very less actual testing time during the day.

Figure 14: Part 1- The thousand mile test on the city roads.

To resolve this issue another set of batteries (12V heavy duty lead acid batteries) was procured which could be charged simultaneously as the testing was in progress. In spite of this arrangement there were only a limited number of miles that could be put on the vehicle each day.

Figure 15: Part 2- The thousand mile test on the city roads

In the interest of saving time and overcoming the limitation of power supply, the test was conducted thereafter on jack stands back in the laboratory. The battery chargers provided an appropriate solution in converting the vehicle to hybrid operation. Motor generators are readily available and are low cost whereas power supplies which can provide a 72V DC output at 50-75 amps are very expensive. Therefore a generator was used in order to run three 12V charging units and one 36V charger in series to provide 72V of charging voltage at around 10amps of

current. This was also our solution to make the ATV a series hybrid which was explained in previous chapters.

Figure 16: Odometer reading before and after the thousand mile test.

Table 5: Log sheet for the thousand mile test.

The vehicle had no trouble in achieving the 1000 mile landmark while working in the series hybrid configuration. The lab testing was done under supervision of the members of the team and was completed in 4 days time.

The vehicle did run into issues during the street testing in which at high speeds the electrical systems would trip and shut down immediately. The issue was diagnosed to be rooted in the traction motor’s settings. Essentially the front and the rear traction motors were tuned so as to cut off, if it crosses certain speed value. This is done to keep the vehicle to its design intent of low speeds and also to prevent the motors to burn out. This cut off speed was incorrectly set to different values between the front and rear motors, so whenever the vehicle tried to cross the lower of the two set values the electrical system would as programmed trip and requires rebooting. This was a dangerous issue as the vehicle would stop responding unpredictably.

An SX motor controller was used in order to gather the settings of the motor and to restore them to its correct values.

5. Steer by Wire solution

The Hyrider was built for manual operation of the steering wheel. In order to achieve computer control over the heading of the vehicle the steering had to be computer controlled. Since this is an electronic function the first step in order to achieve this was to be able to make the vehicle steer by wire. The vehicles built did have certain advantages especially in its open space construction which gave us space to improvise on its rack and pinion steering mechanism. This section of the document will describe the process which was involved in developing this module on the vehicle.

5.1 The Design

There were many designs which were brought forth during the brainstorming sessions that would fit the requirements. For the sake of clarity this document will refer to the two main ideas as design A and design B.

Design A was one of the early ideas which were put to test by the team without great success due to the complexity of its mechanical engagement with the system. The design required the following components:

1. Servo Electric Motor

2. Motion Controller

3. Gearbox

4. Magnetic Clutch

The electric motor is essentially required to provide the torque in order to turn the steering column. The gearbox reduces the output speed of rotation from the motor and also increases the torque output. In this design the clutch was integrated in order to have an option of disengaging the motor from the steering column during manual operation of the ATV. This idea was suggested in order to release excess load from the column so that manual turning of the steering wheel is much smoother. A schematic diagram of this design is given in figure 27.

Steering wheel Steering wheel Axle Axle CouplingCouplin g

GearGear Box Box

ClutchClutc h

Motor Motor

Figure 17: Schematic diagram for steer by wire (design A).

Figure 18: Engineering drawings for steer by wire (design A).

Due to the complexity of the mechanical mounting of the clutch plate, this design was not pursued till the end. Also, the team quickly realized that without the clutch in place the steering wheel did not require much human effort for manual operation. Therefore, in order to keep our designs simple but effective, design A was discarded and design B was incorporated.

Design B was effectively a simplification of its predecessor. The only difference being that it did not include the magnetic clutch plate. A schematic for this concept is given in figure 29 for better understanding.

Steering wheel Gear Box Single Input Double Output Axle

Motor

Figure 19: Schematic diagram for steer by wire (design B).

In order to visualize the setup in the laboratory before final execution, the three way gear box was mounted onto the chassis on a Cartesian stand. The steering rod was cut to size in order to accommodate the gearbox which was now fixed in series with the steering rod using universal flexible couplings. The motor was coupled to the third end of the gearbox and secured with bolts. This step was essential in order to prove the design and help us build a support structure for the unit’s mounting.

The concept behind the design was to actuate the turning of the output shaft of the electric motor through commands sent from a computer. This motor output would get transferred to

the gearbox (Single input double output; Gear ratio 10:1) which would in turn rotate the steering column resulting in steering action using the already in place rack and pinion steering mechanism.

For this design’s implementation a support structure had to be installed on the vehicle which could take the load of the gearbox and the motor together and hold it as a single unit which gets engaged with the steering column. This lead to the design of a steering bracket which was fabricated with a 0.5” thick steel plate.

Gearbox End

Chassis End

Figure 20: CAD drawing for Steering bracket (0.5” thick steel).

Four 0.5 inch diameter holes were made on the base of the bracket to bolt it to the chassis. Also four 0.375 inch holes were made on the other end for securing the gearbox along with the motor.

Figure 21: Images to show the mounting of steering bracket

A Finite element analysis was conducted for the cantilever type weight suspension of the gearbox and the motor. The results confirmed the soundness of the design under static load.

For future works, the understanding of dynamic loading must also be studied. This would include loads caused due to sudden bumps on the road in which the servo motor’s weight will apply a larger moment on the gearbox. A recommendation to strengthen the design would be to add a gusset where the bracket bends so the load does not concentrate on the holes.

5.2 Computer control of steering

Once the motor and the gearbox were coupled to the steering column, the only requirement was to control the motion of the motor to achieve desired heading. This essentially would require the motor to provide a suitable torque and a definite amount of turn (direction and number of rotations).

The servo motor we used for this module has an inbuilt encoder which can send back the position of the shaft through its feedback loop. This feature of getting a continuous feedback from the motor was tapped in order to determine the current heading of the wheels. Once the desired position of the wheels as per the encoder feedback is determined a suitable electrical signal needs to be sent in order to turn the wheels with the required torque. The 10:1 Gearbox had double functionality in this system. First, it would transfer the output of the motor to the steering shaft with increased torque value and second, it would reduce the number of rotations being transferred from the motor to the steering shaft. If the motor shaft turns 10 revolutions, the gearbox output shaft would move by just one.

The digital computer can not directly send commands to the motor which runs on analog signals. To resolve this communication gap, a 4 axis motion controller (GALIL™ DMC 1000) was introduced. This controller gave the option of sending voltage signals to the servo motor as directed by the steering algorithm running on the computer. A power amplifier was used to amplify these signals.

Figure 22: Schematic diagram showing the electrical connections for the steer by wire concept

Figure 32 shows a schematic diagram of the electrical connections between the four main units for computer control of the motor:

1. The GALIL Motion Controller (DMC 1000, 4 Axis)

2. Power Amplifier

3. Servo Motor

4. Power supply

The GALIL controller when directed can send out signals to the servo motor which then can provide enough torque in order to turn the steering column with the additional help from the gear box. A C# .NET program was created and designed to provide with this signal according to the input received by a joystick. The joystick had a range of values it could send back according to the input the operator gives by moving the stick. This range was translated into another range which was dependant on the range of values the GALIL could support for the encoder we had on the motors.

Effect on Joystick Motion steering Joystick Axis Position position value controller value wheel Leftmost 0 -40000 Full left turn Between neutral and left 16384 -20000 Half left turn Center (default ) 32767 0 No turn Between neutral and right 49151 20000 Half right turn Rightmost 65535 40000 Full right turn

Table 6: Values defining numerical position on each control unit

The above table shows the relation between the movement of the joystick and its effect on the steering wheel with controls going via the motion controller. We now had a system in place which could decipher the input from a joystick and convert it into required physical steering action.

6. Brake-by-Wire solution

A vehicle’s braking system has to be very robust for safety reasons. The hyrider, a 2100 pounds machine can cause considerable damage to life and property if it is let loose with a maximum speed of 45 mph. The ATV has an existing hydraulic braking system which is similar to any conventional production vehicle’s brake design.

A review of the different kinds of braking systems has already been discussed in the literature survey. This chapter will deal with the computer control of the brakes on the Hyrider, explaining the modifications that were made in order to introduce the brake by wire system.

The unique feature about the design introduced was the availability of manual as well as computer control over the brakes at all times. This concept was critical as the vehicle would eventually undergo numerous tests of new unproven algorithms for its sensors, and safety of the team, the by standers and property was of utmost importance. Moreover the vehicle would house expensive sensors and equipment which were fragile and could easily get damaged on impact.

To give a brief on the existing system on board, the vehicle had hydraulic actuated braking system in place with disc brakes on all four wheels. The brake pedal was connected via linkages to its master cylinder housing. The housing consisted of two cylinders each having a separate brake line running from their end to the front and rear brake calipers respectively. The hyrider has a slightly unconventional routing for the brake lining. Generally, vehicles have what is called

a diagonal routing. Here output from each line coming out of the master cylinder is given to one front and the diagonally opposite rear wheel. This design is advantageous if there is a leak in one of the lines; the other line continues to have control over one front and one rear wheel.

This is helpful in keeping the balance of the vehicle during braking specially in 2 wheel drive machines.

Figure 23: Two master cylinders with two outputs for respective wheel set

6.1 The Design

In order to have manual and computer control at the same time always the brakes were divided into two segments. These two segments would work independently, one giving electronic control to one set of brakes and the other always being under manual control.

The master cylinder housing was modified and the output from both the cylinders was combined and routed to the rear wheel brake system. In order to achieve this a few brake line adapters were used along with laying down a new brake line segment. For this operation, various flaring tools and brake line fittings were used. In order to achieve a factory finish fitting we adopted various different methods to get the perfect flare. We even used a blow torch in order to flare the lining without cracking the bulge. After many trials, the method was perfected.

Figure 24: 3/16” dia brake adapters

Figure25: Tools used for creating new brake lining Left- Flaring tool, Right- Pipe bender

Figure 26: Using blow torch to assist flaring of brake tube

A 3/16” diameter lining was used for all of the brake lining. The output from the two master cylinders was combined using an adapter and supplied to the rear wheel calipers. This line would only take care of the manual braking mechanism and would work independently.

6.2 Computer control

To implement computer control over the front brakes, it was required to have an actuator which can be electronically controlled. The following components had to be added and used to achieve this goal:

1. Brake Actuator: A Dexter DX series brake actuator rated at 16000psi and works on a 12V

DC power supply.

2. Brake Controller: 2 Dexter Predator DX2 electric brake controller. This system works on

a 12V DC circuit.

3. Motion Controller: One axis from the Galil DMC 1000 motion controller.

Figure 27: Components introduced for brake by wire solution Left- Dexter brake actuator, Right- Dexter brake controller

The trailer brake actuator works on a simple principle. When the controller is directed, it sends out a voltage signal to the brake actuator. Receiving this signal triggers the hydraulic pump and the brake fluid gets pumped into the hydraulic lines. A simple schematic diagram of the wiring for the controller is shown in the figure 36.

Figure 28: Schematic diagram of electrical connections for Electronic control of brakes

Now that we had the prerequisites to electronically control the front brakes, it was required to trigger the controller through a computer signal. One axis of the 4 axis Galil motion controller

(DMC1000) was used to achieve this objective. This time instead of manually directing the controller to send the required voltage to the actuator, the Galil’s output was manipulated and amplified in such a way so that it impersonated manual input. Since the Galil’s output does not match the amount of voltage which needs to be sent as trigger for the actuator, this small voltage signal is first sent to the Dexter Predator DX2 brake controller.

The brake controller is typically controlled by an inbuilt lever which basically acts like a rheostat that changes the voltage drop between its two ends when moved. The voltage drop (0-5V) is what determines the voltage signal which needs to be sent to the actuator. This voltage drop is now provided by the Galil Motion controller which can be varied according to the magnitude of braking force required that was translated from the movement of the joystick.

Motion Joystick controller value Joystick Axis Position position value (voltage) Effect on Brakes Leftmost 0 5 Full braking force Between neutral and Half the braking left 16384 2.5 force Center (default ) 32767 0 Zero braking force Between neutral and Half the braking right 49151 2.5 force Rightmost 65535 5 Full braking force

Table 7: Values on system corresponding to braking force requirement

Under extreme circumstances it was observed that apart from the manual rear wheel braking available to the operator, there should also be an alternative to use the electric brakes without computer control. In order to achieve this, a second brake controller was introduced. A single pole double throw (SPDT) switch was mounted onto the dashboard whose purpose was to simply change the source from where the brake actuator would get it operating signal. It could be either the modified controller which gets its trigger from the computer or the independent controller which can be manually operated. A schematic diagram of the circuit is shown in the figure.

Figure 29: Schematic diagram for computer control of braking by wire

As seen from the figure, the X axis output of the Galil was used for the by-wire solution. The ground from the breakout board and the terminal ACMDX are connected to the modified brake controller.

The joystick sends out commands to the Galil, the output of which is in the form of a voltage ranging from 0-5V DC. This voltage triggers the 12V electrical circuit in the brake controller which sends out proportional voltage signal to the actuator. Once the actuator is triggered, it pumps braking fluid into the brake lining providing necessary hydraulic pressure to the brake calipers and brake shoes.

7. Conclusion

The center for robotics research at the University of Cincinnati has been developing smaller autonomous vehicles for many years. It has been showcasing its design each year at the

Intelligent Ground Vehicle Competition (IGVC) with very successful performances. In theory the implementation of these technologies now on the Hyrider would involve scaling up the already defined solutions. During this research work, which was result oriented, it was discovered that changing the scale of the vehicle introduces a plethora of other very practical issues which go along with the size change.

The ATV was successfully brought to a state in which it was legally allowed to drive on the city roads with all the mechanical and electrical requirements met. Functionality was restored on various modules like the electrical system, accessories etc which were not completely built by the original manufacturers of the vehicle. Various theories were discussed and understood in relation to hybrid solutions for electric vehicles and many new proposals were brought up during the process of bringing the vehicle to the DARPA challenge. Development of flash chargers and all-wheel steering etc are just a couple of ideas which were proposed for future works where the vehicle could act as a good test bed for experimentation.

A drive by wire status was achieved which required a lot of designing and fabrication to introduce an optimum solution for the vehicle type. Controls of various electrical components were studied and modified to custom build a solution specific to the Hyrider. Future works could build on the technology developed so far and aim to refining it further so as to be able to produce a turnkey solution for other vehicles requiring such technology.

The vehicle is an excellent test bed to develop concepts and also is a great educational tool to understand functioning of an electric vehicle. Due to its size, it provides an excellent platform for focus groups to work separately on different modules of the drive by wire or electric vehicle technologies in general.

It will be interesting to see now that a drive by wire status has been achieved how smoothly the sensor technologies will get integrated to it, when translated to this full size vehicle.

8. Reference

1. National Highway Safety Administration, URL: http://www.nhtsa.gov/

2. Collinson, R. P. G., “Fly-by-wire flight control”, Computing & Control Engineering Journal,

Vol. 10, pp. 141-152, (1999)

3. Askue, V., “Fly-by-wire”, Air Medical Journal, Vol. 22, pp. 4-5, (2003).

4. Massey, D., “Lotus Service Notes: Brake Systems and Pedal Box”, Lotus Cars Ltd, pp. 2,

(2001).

5. Kuhlgatz, D.,“Bosch: A Product History”, Robert Bosch-GmbH Historical

Communications, URL: http://rb-k.bosch.de/en/startinfomain.html

6. Continental, “Electro-mechanical Brake”, Continental Automotive GmbH, URL:

http://www.conti-online.com

7. Duffy, J., Stockel, M. & Stockel, M., “Automotive Mechanics- Fundamentals”, Haynes

Manuals, (2001).

8. Delphi, “Delphi Electric Power Steering”, Chassis and Steering Systems, Delphi

Corporation, (2005).

9. Wilwert, C., Navet, N., Song and Simonot-Lion, F., “Design of automotive X- by-wire

systems”, The Industrial Communication Technology Handbook, CRC Press, (2004).

10. Calmotors, URL: http://www.calmotors.com/

11. Amar Shah, “Drive-by-wire”, Thesis, University of Western Australia, (2009).

12. Leiann K. Leppin, “The conversion of a General Motors Cadillac SRX to Drive-By-Wire

Status”, MS Thesis, Virginia Polytechnic Institute and State University, (2005).

13. Park, Y. Jung, “Semi-Active Steering for Steering for Steer-By-Wire System”,

Autonomous & Transportation Technology Congress and Exhibition, Vol. 6, pp.372-382.

(2001)

14. Schwartz, Ralph, Isermann, Rolf, Bohm, Jurgen, Nell, Joachim, Reith, Peter, “Modeling

and Control of an Electromechanical Disc Brake”, SAE 980600.

9. Appendix

9.1 Jeep electrical wiring documentation.

1 3 5 7 9 11 13 15 2 4 6 8 10 12 14 16

Dash Wire Pin NULL 1 SW2 Bot 2 NULL 3 Battery 2 4 Com WY2 WHITE 5 Tach 6 Com WY3 7 Tach 8 Com GP3 9 Tach 10 Com GP2 11 Start Bot 12 SW2 Top 13 Start Top 14 SW2 Mid 15 Battery 1 16

Table 8: Dashboard to J1 - female Duel Row Header

Key 1 2

Fuze Wire Pin non-polar 1 non-polar 2

Table 9: Fuze to J2 - female 2 P Single Inline Row

15 13 11 9 7 5 3 1 16 14 12 10 8 6 4 2

Pin Wire Connect Label Note 1 Null 2 GEF4 DSH 8 X2 3 Null 4 DC6 DSH 7 5 WHITE GER 23 DSH 14 6 Motor DSH 6 7 GER 22 DSH 13 8 Motor DSH 5 9 GEF 23 DSH 12 10 Motor DSH 4 11 GEF 22 DSH 11 12 DC9 DSH 3 13 GEF 5 DSH 10 DC3 14 (KEY) DSH 2 15 Terminal DSH 9 16 DC7 DSH 1

Table 10: J1 to "Jeep" - male Duel Row Header

Key 1

Pin Wire Connect 1 Clutch 1 2 Key Relay 87

Table 11: J2 to Jeep, Single Inline Row

Pin Wire Connect 87 Terminal 30 GEF/R 3 X2 86 Black 85 Red

Table 12: Start relay to jeep, relay connector

Pin Wire Connect GEF/R 1 13 X2 2 GER Negative

Table 13: Brake to Jeep, Screwed Fork Terminals

6 5 4 3 2 1 7 8 9 10 11 12

Pin Wire Connect Label Note 1 Traction Neg DC1 2 Null 3 DSH14(Key85) DC3 4 KEY 86 DC4 5 START 86 DC5 6 DSH7 (pin4) DC6 7 DSH16 DC7 8 Throttle 5 DC8 9 DSH 3 (pin12) DC9 10 NULL 11 NULL 12 Clutch 1 DC12

Table 14: J1 to "Jeep" - male Duel Row Header

8 7 6 5 4 3 2 1 15 14 13 12 11 10 9 23 22 21 20 19 18 17 16

Pin Wire Connect Label Note 1 Clutch 1 GEF1 GER1 2 Terminal GEF2 GER2 3 START 30 GEF3 GER3 4 DSH 8 GEF4 GER4 5 DSH 10 GEF5 GER5 6 GEF6 GER6 7 Throttle 4 8 NULL 9 WHITE Throttle 2 10 NULL 11 NULL 12 NULL 13 Brake GEF13 GER13 14 NULL 15 NULL 16 NULL 17 Clutch 6 GEF17 18 NULL 19 NULL 20 NULL 21 NULL 22 DSH 11 GEF22 23 DSH 9 GEF23

Table 15: Traction to Jeep - female 3 row special

Pin Wire Connect 87 Fuze 30 Terminal 86 Black 85 Red

Table 16: Key relay to jeep, relay connector

8 7 6 5 4 3 2 1 15 14 13 12 11 10 9 23 22 21 20 19 18 17 16

Pin Wire Connect Label Note 1 Clutch 1 GER1 GEF1 2 Terminal GER2 GEF2 3 START 30 GER3 GEF3 4 DSH 8 GER4 GEF4 5 DSH 10 GER5 GEF5 6 GER6 GEF6 7 Throttle 4 8 NULL 9 NULL Not the same as GEF 10 NULL 11 NULL 12 NULL 13 Brake GER13 GEF13 14 NULL 15 NULL 16 NULL 17 Clutch 6 GER17 18 NULL 19 NULL 20 NULL 21 NULL 22 DSH 7 23 WHITE DSH 5

Table 17: Traction to Jeep - female 3 row special

1 3 5 2 4 6

Pin Wire Connect Label 1 NULL 2 DC5 APG 3 WHITE GEF/R 9 APK 4 GEF/R 7 APE 5 DC8 APJ 6 NEG APD

Table 18: Throttle to Jeep - 6 Pin Duel Row Header

11 9 7 5 3 1 12 10 8 6 4 2

Pin Wire Connect Label Note 1 P3 Key Relay 2 30 3 P5 DSH9 (pin 4 15)

5 P7 Front Clutch 6 5 7 P9 8 Start Relay 9 P11 10 FKEY Back Clutch 11 5 P1 12 RKEY

Table 19: Terminal Strip