Effective clamping force control for electromechanical brake system

The electromechanical brake (EMB) is a type of brake-by-wire (BBW) system that generates the clamping force between brake pad and disk through an electric motor and mechanical transmission. In this paper, an EMB clamping force control system is developed that addresses several major challenges in practical implementation. Firstly, a nonlinear EMB model including the DC motor, planetary gear set, ball screw, and clamping force model is built. Particularly, a novel clamping force model is introduced based on a linear transform of two polynomial functions. Then, a clamping force estimation algorithm is proposed, which only requires the existing measurements of motor torque, angular speed, and position. The contact point of the brake pad and the disk is also estimated using angular acceleration as an indicator. The tracking controller is based on the disturbance observer structure, with a PI feedback controller and a zero phase error tracking feedforward controller. Finally, the performance of the entire control system under various conditions is evaluated based on simulation.