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Concept of Moving Centre of Gravity for Improved Directional Stability for Automobiles

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Concept of Moving Centre of Gravity for Improved Directional Stability for Automobiles IJIRST –International Journal for Innovative Research in Science & Technology| Volume 2 | Issue 11 | April 2016 ISSN (online): 2349-6010 Concept Of Moving Centre of Gravity for Improved Directional Stability for Automobiles - Simulation Joseph Sebastian Siyad S UG Student UG Student Department of Mechanical Engineering Department of Mechanical Engineering Saintgits College of Engineering Saintgits College of Engineering Subin Antony Jose Ton Devasia UG Student UG Student Department of Mechanical Engineering Department of Mechanical Engineering Saintgits College of Engineering Saintgits College of Engineering Prof. Sajan Thomas Professor Department of Mechanical Engineering Saintgits College of Engineering Abstract This paper is a study based on the implementation of a new concept in AUTOMOBILE which will help in improving the directional stability and handling characteristics of vehicle. The purpose of this study is to analyze the influence of position of CENTRE OF GRAVITY of a vehicle in its stability in accordance with YAW MOTION, ROLL MOTION, UNDER STEER and OVER STEER. The concept is to implement a mechanism which can bring SHIFTING OF C.G in automobile, as per the conditions. The influence of position of C.G is much bigger for the balancing of forces in dynamic stability of the vehicle. The concept of moving C.G will help to acquire this added stability to the vehicle even in the worst conditions.The directional stability of a vehicle is influenced by the steering angle and slip angle of the tire to an extent. It is possible to have a variation in these values by the shifting of CG. The designing of a convenient mechanism which helps in achieving the movement of the mass (either by pumping a high density fluid or my movement of a solid block by mechanical linkage) is to be done and have to be tested in a real time vehicle. Before proceeding to the practical level of the concept, validation of the idea based on theoretical aspect has to be done. For this, a dynamic simulation is to be done with the software MATLAB. Keywords: Shifting of CG, directional stability, handling characteristics _______________________________________________________________________________________________________ I. INTRODUCTION Background The development achieved so far in the field of automobile industry is remarkable. Among the various factors such as performance, fuel efficiency, stability etc, the vehicle stability is having the highest importance in the current scenario. There are a lot of factors that affect the stability of a vehicle, like aerodynamics, geometry, mass specific, moment specific, tire specific, roadway specific, driving techniques and so on. In the present situation, the Centre of mass, which have a significant effect in the stability of the vehicle, is considered to be fixed. Slight variation in the position of CG may arise due to the change in load because of the weight of passengers. A shift in the position of CG could in effect control the handling characteristics of a vehicle. Properties such as understeer, oversteer, and neutral steer are explaining the stability of a vehicle during its dynamics. These mentioned properties are found to have direct relationship with the position of CG, tyre properties and slip angle. Hence a variation in the position of CG could in effect bring a controlled vehicle movement in any maneuver and at any speed. Idea Generation and Screening Centre of gravity can be assumed as a point where whole of the mass of the body may be assumed to be concentrated. By the implementation of the Concept of Moving Centre of Gravity in vehicle, we are trying to improve the directional stability and the handling characteristics of the vehicle. There are a lot of forces acting on a vehicle during its motion. The force balancing is the phenomenon which brings adequate stability during driving. Handling characteristics of a road vehicle are concerned with its response to steering commands and to environmental inputs affecting the direction of motion of the vehicle such as wind and road disturbances. There are two basic problems in vehicle handling: one is the control of the vehicle to a desired path, the other is the All rights reserved by www.ijirst.org 556 Concept Of Moving Centre of Gravity for Improved Directional Stability for Automobiles -Simulation (IJIRST/ Volume 2 / Issue 11/ 097) stabilization of the direction of motion against external disturbances. In most of the extreme cases, the balancing of forces is done by control of the brake force. If a moving centre of gravity is possible to be implemented in a vehicle, the braking constraints can be held apart and better stability can be achieved. It is made possible by altering the slip angle and stiffness coefficient of tyre which directly involves the directional stability and are parameters that determines whether the vehicle is in oversteer, understeer or neutral steer condition. Concept Testing In this project, the effect of the C.G location in a vehicle during its dynamics is analyzed by dynamic simulation. The required hand calculations that define the effect of position of CG will be done by the available standard equations regarding vehicle handling and dynamic stability. The simulation will be carried out by using the dynamic analyzing software MATLAB, which is a powerful tool that can be effectively used for this purpose. The shift of an additional weight and its effect in bringing a change to the position of CG is analyzed. A mechanism which can impart a change in the position of C.G by the movement of a mass is to be designed which can be an effective way to improve the stability of vehicle by the concept of moving Centre of gravity. II. OBJECTIVE Automobile is one of the fast developing and highly advanced field in the world and automobile manufacturing giants are in an urge to capitalize the field with hi tech inventions that aids the performance and safety of the vehicle. Having a distinguish with the performance and safety of the vehicle, it is always the safety that leads in front. The main objective of this project is to introduce a new concept in automobiles which may have a great influence in the vehicle handling characteristics and directional stability. The various phenomenon such as yaw motion, roll, pitch, understeer, oversteer that defines the stability of a vehicle are in direct relation regarding the position of CG of the vehicle. As far as concerned, no recognizable studies have been conducted with a concept of a moving centre of gravity in a vehicle. This project aims in analyzing the effect of CG and the various advantages that can be accomplished by implementing a moving centre of gravity which can be controlled as the required conditions and terrain. By incorporating a real time monitoring and controlling system, the proposed method, if successful, can be implemented in the future super vehicles. III. EXISTING TECHNIQUES Traction Control System (TCS) A traction control system (TCS), is typically (but not necessarily) a secondary function of the electronic stability control (ESC) on production motor vehicles, designed to prevent loss of traction of driven road wheels. TCS is activated when throttle input and engine torque are mismatched to road surface conditions. Intervention consists of one or more of the following: Brake force applied to one or more wheels Reduction or suppression of spark sequence to one or more cylinders Reduction of fuel supply to one or more cylinders Closing the throttle, if the vehicle is fitted with drive by wire throttle In turbocharged vehicles, a boost control solenoid is actuated to reduce boost and therefore engine power. Typically, traction control systems share the electro hydraulic brake actuator (which does not use the conventional master cylinder and servo) and wheel speed sensors with ABS. Pneumatic Suspension System If we look at the different suspension systems used in motor vehicles today, the most apparent difference between them is that they are either mechanical or air suspension systems. Both types are, of course, incapable of meeting all technical requirements. If they are, however, directly compared, it soon becomes apparent that air suspension offers major benefits compared with mechanical suspension systems. As a result air suspension systems are used to an increasing extent in commercial vehicles. Benefits of Air Suspension Systems 1) By changing the bellows pressure, depending on the load carried on the vehicle, the distance between the road surface and the vehicle’s superstructure addresses the same level. This means that the boarding or loading height, and the headlight settings, remains constant. 2) Spring comfort remains almost unchanged across the whole of the loading range; again this is achieved by changing the bellows pressure. The passenger on a motor coach will always perceive the same pleasant type of oscillations. Sensitive loads can thus be carried without being severely damaged. The well-known “jumping” of an unlade or partially laden trailer no longer occurs if an air suspension system is used. 3) The stability of the steering system and the transfer of the braking forces are improved since all wheels always have good adhesion to the road surface. 4) The pressure in the air bellows, depending on the load the vehicle carries, is ideal for use in controlling automatic load-sensitive braking. All rights reserved by www.ijirst.org 557 Concept Of Moving Centre of Gravity for Improved Directional Stability for Automobiles -Simulation (IJIRST/ Volume 2 / Issue 11/ 097) 5) In the area of control for interchangeable platforms, air suspension systems are an excellent basis for cost-effective loading and unloading of containers. Tyre Pressure Monitoring System (TPMS) A tire-pressure monitoring system (TPMS) is an electronic system designed to monitor the air pressure inside the pneumatic tires on various types of vehicles. TPMS report real-time tire-pressure information to the driver of the vehicle, either via a gauge, a pictogram display, or a simple low-pressure warning light.
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