Nonlinear Clamping Force Estimation and Robust Control of an Electro-Mechanical Brake System for Electric Vehicles Based on PWA-H _∞

The electro-mechanical brake (EMB) is a type of brake-by-wire system that generates the clamping force through an electric motor and mechanical transmission, and it has the performance of faster response and higher tracking accuracy. This article presents a novel H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> robust controller based on a clamping force estimator to track desired clamping force for “sensorless” electro-mechanical brake system in the presence of both nonlinearities and uncertainties. First, a novel EMB model including the dc motor, planetary gear set, flexibility-considered ball screw, and pressure-displacement relationship-considered clamping force model is built. Particularly, a clamping force estimator based on extended least square algorithm is proposed, which only requires the existing measurements of motor angle. Then, the control-oriented piecewise affine (PWA) model and H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> robust theory are adopted to design the PWA-H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> based clamping force tracking controller strategy. Finally, the simulations and experiments show that the proposed PWA-H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> strategy provides satisfactory tracking performance and robustness in the presence of uncertainties, nonlinearities, and disturbances in the diverse working region of EMB system.