Motion control of a linear brushless DC motor drive system with nonlinear friction compensation

A new robust controller is proposed for motion control of a linear brushless DC motor (LBDCM) drive system with uncertainties. The friction and load variation are the main uncertainties in the LBDCM drive system. To obtain the precise linear model of the system by dynamic signal analyzer (DSA), nonlinear friction compensation is firstly used for the LBDCM drive system identification in the paper. Two radial basis function (RBF) networks are developed. One is applied to nonlinear friction compensation, and the other is applied to payload estimation so as to extend the robustness of μ controller. The proposed controller consists of μ synthesis controller and these two RBF networks and it is capable of the large tolerable load variation. Furthermore, the mode switching control (MSC) is applied to achieve better time response results. Settling time in the step response is reduced to about 0.15s, which is much less than that in previous related work. Both the simulated and experimental results show that the proposed controller can suppress the influence of the nonlinear friction and reduce the effect of the load variations.