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M.Ing. / Adaptive traction control can greatly enhance the mobility of vehicles on varying road surfaces. Traction control includes Antilock Braking Systems (ABS) and Antislip Regulation Systems (ASR). During braking, wheel slip is controlled with ABS, while wheel slip during acceleration is controlled by an ASR. Since the friction between a vehicle's tyre and the road surface is a function of wheel slip, there is an optimum wheel slip value at which the best road holding performance can be achieved. This optimum wheel slip value will however change with differing road surfaces and vehicle speeds. Optimising the wheel slip values has several advantages: both vehicle stopping and acceleration distances can be optimised, vehicle handling during in-turn braking and acceleration are optimised and tyre wear is reduced. Currently there are various ABS and ASR systems available, with the common goal of optimising wheel slip. These systems are however mechanically complex, while the operation of both these systems is usually triggered when some wheel slip value is exceeded. Differing road surfaces can greatly influence the effectiveness of these systems. The central theme of this research is the development of a fuzzy logic control algorithm for vehicle traction control. The control algorithm is tested with an experimental setup. The operating conditions experienced by an ABS are closely simulated in order to study the feasibility of fuzzy logic for traction control. The results obtained indicates the viability of fuzzy logic for wheel slip control. Confirmation of these results, obtained with the experimental ABS, have to be validated during vehicle testing. The main goal is to improve the performances of existing traction control systems and the feasibility of fuzzy controllers in automobile applications.

Bibliography : leaves 238-262. / xxiii, 262 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 1995

Active safety systems for road vehicles have been improved considerably in recent years along with technological advances and the increasing demand for road safety. In the development route of active safety systems which started with introduction of digital controlled ABS in the late seventies, vehicle stability control systems have been developed which today, with an integration approach, incorporate ABS and other previously developed active safety technologies. ABS, as a main part of this new structure, still maintains its importance. In this thesis, a design methodology of an antilock braking system controller for four wheeled road vehicles is presented with a detailed simulation work. In the study, it is intended to follow a flexible approach for integration with unified control structure of an integrated active safety system. The objective of the ABS controller, as in the previous designs in literature, is basically to provide retention of vehicle directional control capability and if possible shorter braking distances by controlling the wheel slip during braking. iv A hierarchical structure was adopted for the ABS controller design. A high-level controller, through vehicle longitudinal acceleration based estimation, determines reference slip values and a low-level controller attempts to track these reference slip signals by modulating braking torques. Two control alternatives were offered for the design of the low-level controller: Fuzzy Logic Control and PID Control. Performance of the ABS controller was analyzed through extensive simulations conducted in MATLAB/Simulink for different road conditions and steering maneuvers. For simulations, an 8 DOF vehicle model was constructed with nonlinear tires.

In today’s fast moving world, automobiles are facing challenges in terms of having to survive road accidents, increasing traffic, bad road-conditions and high/express ways. Brake systems play a vital role in controlling the vehicle speed while avoiding road accidents. The conventional brake systems consist of basically an actuator, transmission and frictional parts. This system is difficult for manipulated control by the driver during emergency and panic braking situations. In particular road and environmental conditions, it requires certain skill to have safe and effective brake control, which is always not possible from all drivers. Wheel locking is a predominant phenomenon during panic braking and this will cause vehicle skidding resulting in injuries and road accidents. In the case of a two-wheeler, being a single-track vehicle, skidding is one of the major causes for fatal road accidents due to loss in lateral balance. As the road safety regulations are becoming more stringent, the anti-lock brake systems (ABS) will replace the conventional brake systems in all road vehicles to avoid accidents and to improve vehicle safety. Early ABS systems, developed in the last 100-years, use intermittent and cyclic brake pressure control by sensing the wheel speed or wheel-slip as one of the major control inputs. Regulating the brake pressure with a preset threshold value is another method. These ABS systems have used electronics, or hydraulics or pure mechanical control. However, such ABS are not widely used in two-wheelers and other low cost vehicles till now, because of several limitations identified as follows: High cost, power supply needed for its operation in the case of intermittent and cyclic brake control, susceptibility to failure in the electronics system, interference from RF signals (from cell-phones for example), uneasiness to drivers from pedal pulsations with pedal noise, heavier weight, increased vehicle vibrations and failure modes of wheels due to torsional vibrations. The present research work is carried out to develop a new mechanical ABS concept, which will address most of the above problems. During braking, the change in rider-input force will change wheel reactions. This change is made proportional to the change in rider input force only upto wheel locking. Such a principle is used to develop the new mechanical ABS. The new concept regulates the output force from the ABS, by sensing the dynamic wheel reactions with increase in rider-response. The ABS output force is regulated by one of the following ways: (a) Slipping-down the lever-ratio or (b) preventing the excessive brake input force. Based on the parameters like less number of parts, least weight, simplicity, reliability, efficiency, durability, time-response, etc., the second method (of preventing the excessive brake input force) has been chosen. Further a new concept of ABS interconnecting system is proposed for usage between the front and rear wheels of the vehicle. This interconnecting system will ensure that the two mechanical ABS systems function at any kind of braking-balance between the front and rear applications. An analytical vehicle model has been developed with several input parameters like mass, geometry, inertia, aerodynamic properties, frictions of road and bearing-supports, road gradients, etc. From this analytical model, the dynamic wheel reactions and limiting adhesion of each tyre for various braking conditions are determined and the results are used to design the mechanical ABS. The same analytical model is used to predict the brake performance like stopping distance, vehicle deceleration and the vehicle speed variation for ideal braking conditions. The new ABS is modelled in Pro-E using the inputs from the analytical model. To evaluate the concept, a functional proto-type is built and fitted on a motorcycle. The ABS is evaluated for its functionality and performance at different road (level surface, up-gradients and down gradients) and environmental conditions (dry and wet road conditions). Using the VBOX II, proximate sensors and load-cells fitted on the vehicle, the vehicle stopping distance, wheel slip and pedal force are measured. The results show that wheel locking does not occur under panic driving conditions, which is the primary objective. In addition, the results show a good agreement with the predicted stopping distance and vehicle deceleration from the analytical model. As there is good scope for this new mechanical ABS for use in two-wheelers and other low cost vehicles, further research is needed to make this system work in curvilinear motion & banked surfaces.