A kalman filtering approach to estimate clamp force in brake-by-wire systems

Removing a clamp force sensor from brake-by-wire (BBW) system designs has been driven by the need to reduce costs and design complexities. In this paper an improved method is presented to estimate clamp force using other sensory information. The proposed estimator is based on the Kalman filter where the actuator resolver is used in a dynamic stiffness model and the actuator current sensors as well as the resolver are used to give measurement updates in a torque balance model. Experimental results show that the estimator can handle highly dynamic braking scenarios making it suitable for possible use in anti-lock braking system (ABS) controls. A comparison is made with a previous attempt to estimate clamp force in BBW systems and it is shown that the proposed estimator improves the root mean square error (RMSE) of estimation. A training strategy is explained to ensure that the estimator can adequately adapt to parameter variations associated with wear. This paper finally discusses reliability issues associated with the developed clamp