An investigation and design of slip control braking systems integrated with four-wheel steering.

摘要

Conventional anti-lock braking systems (ABS) permit automobiles to achieve short stopping distance with good directional control and stability during moderate maneuvers. However, during emergency maneuvers where hard braking is combined with severe steering, normally stable cars, even those equipped with ABS, can spin out.; In this work, three new slip control braking systems (SCBS) have been proposed which result in good stability and performance during combined hard braking and severe steering maneuvers. These controllers are shown to be robust against vehicle and environmental changes. They integrate robust tracking control algorithms with a four wheel steering control algorithm. Included in the control systems are a simple tire/road surface identification process and a methodology which calculates the desired longitudinal slip values for front and rear wheels based on the results of the identification process. The design of these control strategies is based on the modelling and analysis of vehicle and tire dynamics, use of proportional and derivative control (PD), sliding mode control, and Lyapunov direct method control methodologies, followed by validation by simulation. The performance of the three candidate SCBS systems are quite similar. The differences in the aforementioned controllers are due to the number of sensors required for implementation.; Each of the SCBS control systems is integrated with a four wheel steering control strategy and evaluated using a nonlinear five degree-of-freedom vehicle "bicycle" model, a nonlinear tire model and a driver model. The simulation results indicate that the combined action of the controllers result in a vehicle that can maintain directional control and stability in situations where the vehicle equipped with only four wheel steering and a conventional ABS system loses control and spins out.