Advanced Control Strategies for Hybrid Brake-by-Wire Actuator

Abstract

Friction is a non-linear phenomena virtually present in all mechanisms with relative motion. It is an important aspect of the controlled system since it leads to deteriorated performance. Friction effect is particularly significant in systems with high reduction transmission elements and hydrualic links, like the hybrid braking system considered in the thesis. The principal motive of this thesis is to improve the pressure tracking capability of the hybrid brake by xompensating friction. Two control strategies namely the P-PI pressure-speed-cascaded control and the sliding mode control approach are designed for the system towards this goal. A load dependent static Gaussian model is identified for friction compensation using the non-linear least squares method. A reduced order control oriented model is identified and consequently validated with the testbench. In the cascade controller structure, friction and model-based compensation of the system is included and their assistance in improving the setpoint tracking performance is analyzed. A friction compensated, non-linear control strategy in the form of sliding mode control (SMC) is designed based on the optimized model. A comparison of the proposed controllers with the controller currently implemented on the brake system is presented. With the help of experiments conducted on the testbench, the effect of the compensation strategies in improving the pressure tracking performance is analyzed.