Estimation Of An Electrohydrostatic Actuator Using A Combined Cubature Kalman and Smooth Variable Structure Filter

Electrohydrostatic actuators (EHAs) are an emerging type of actuator typically used in the aerospace industry, and are self-contained units comprised of their own pump, hydraulic circuit, and actuating cylinder. Recently, a novel EHA system has been developed. A particularly important parameter of this system is the bulk modulus. This value cannot be measured directly and must be estimated using state and parameter estimation techniques such as the Kalman filter (KF), particle filter (PF), or the smooth variable structure filter (SVSF). The cubature Kalman filter (CKF), recently proposed in 2009, is an estimation method that makes use of the standard derivation of the Kalman filter, as well as defined cubature points which are used to draw the probability distribution of the states with greater accuracy. The SVSF is a relatively new estimation strategy which is very robust and stable to modeling errors and uncertainties. The combination of these two methods (CKFSVSF) yields an accurate and stable estimation method which has been applied on an EHA. The results of this combination are compared against the standard KF in terms of accuracy, robustness to errors and uncertainties, and filter complexity.