Wheel slip reset controller in automotive brake systems

The use of new technologies in brake systems, allows to generate independent brake forces at each wheel by slip controllers. The aim of these controllers is to provide certain degree of slip on each wheel independently, maximizing the friction between the tire and road, avoiding simultaneously its lock. This paper investigates the application of reset control to the slip control in automotive brake systems. A reset controller is a standard linear controller that, at some instants, resets to zero its internal states (or part of the states). The reset instants are triggered by the event of zero crossing of the tracking error. It has been proven in many other applications (process control, teleoperation, motor drives etc.) that reset control is able to overcome linear limitations, that is, achieves time responses with good speed and damping properties, combined in a way that no other linear controller is able to produce. We investigate the addition of a reset integrator (Clegg integrator CI) to a PI used as slip controller. We have found by simulations that the PI+CI has superior performance and gives a better solution to the trade-off between speed and damping. The controller design is based on a simplified vehicle model, taking into account the interaction tireroad, actuator saturation and time-delay in the communications between local and central units. We check through simulations that the application of reset controllers instead of the conventional ones will allow an improvement on the robustness and performance of the system.