Measurement of external leakage of hydraulic servo-motor based on robust extended kalman filter

An obvious obstacle as we study the leakage of hydraulic servo-motor is how to measure the leakage dynamically as the motor works under super low speed tracking condition. Since the flow rate of leakage is too low to be measured by flow meter, the paper presents a scheme of external leakage measurement, by which instantaneous flow rate of external leakage can be measured automatically and dynamically. In the scheme two hydraulic measurement cylinders with positioning sensors are employed to exam the inlet and outlet flow rate of hydraulic servo-motor and based on continuity equation instantaneous flow rate of external leakage can be measured indirectly. Because of the nonlinear and uncertainty characteristic of hydraulic system and ineffectiveness of applying extended Kalman filter which strictly assume Gaussian noises on the issue, a robust extended Kalman filter (EKF) is applied for the research. The robust EKF is combined one type of the recursive stochastic approximation (SA), p-point estimator (PPE) with classical EKF. At last, experiment is carried out to verify the effectiveness of the REKF by measuring the external leakage in different position of motor.