Wheel Speed Distribution Control and its Effect on Vehicle

Abstract

The current work aims at bridging the gap between the current vehicle handling characteristics and the future demands of higher vehicle handling performance, required to guarantee higher safety and facilitate the application of autonomous driving, platooning and automated highways systems. For this task a state 'of the art vehicle chassis control system known as "Wheel Speed Distribution Control" (WSDC) has been proposed. WSDC in principle relies on controlling the vehicle driven wheel speeds to enforce better vehicle handling performance. The WSDC system capacity has been investigated using numerical simulation. Tberefore, an innovative vehicle handling simulation model has been developed from first principles. It employs the Magic Formula (MF) tyre model for combined slip, has 23 degrees of freedom and includes more than 60 vehicle handling parameters. The vehicle handling model has been developed using the novel Cartesian Geometric Translation (CGf) technique which employs geometry, trigonometry, Cartesian coordinates and finite difference approximation in the time domain to facilitate development of high speed models. The model has been built using the BASIC'O programming code in the DOS'O environment and optimised to meet the novel Model Predictive Control (MPC) based feedforward WSDC yaw rate controller requirements, such as small code size (less than 35 kb) and processing speed faster than real time. The simulation results validated the WSDC principles as it showed the capacity of WSDC to enforce the desired yaw rates, with acceptable driven wheel longitudinal forces. To put WSDC into practice,an original hardware" Wheel Speed Distribution Differential" (WSDD) design has been developed and optimised for lower speed, torque, power,production and maintenance requirements.It has the capacity to precisely differentiate the driven wheels speed under the influence of a DC motor with relatively small power requirements. It has linear speed and torque characteristics which facilitate its control. It also has been developed to allow many beneficial differential modes. The simulation results of the whole WSDC system have clearly demonstrated that it can in fact achieve its development target of feasibly enhancing vehicle handling performance