Clamping Force Control Based on Dynamic Model Estimation for Electromechanical Brakes

The electromechanical brake (EMB) is expected to be utilized for future brake systems due to its many advantages. In this paper, keeping commercialization of EMB in mind, a new EMB clamping force controller is proposed to overcome the limitations of an existing controller, namely, extra cost for sensor installation and response delay. To design the controller, both mechanical parts and electrical parts in EMB have to be mathematically analyzed. Also, dynamic models, clamping force, and friction torque are estimated to generate some feed-forward terms of the controller. With an estimation of the contact point where brake pads start to come into contact with a disk wheel, the clamping force is expressed as a polynomial curve versus the motor angle. The estimated clamping force is evaluated in comparison with measured values by a load cell. The proposed controller is based on an adaptive sliding mode control (SMC) method with an adaptive law reducing errors of friction torque model. Lastly, the performance of the entire control system is compared with that of the existing controller on a test bench.