Terminal sliding mode control for mechatronic servo systems with backlash nonlinearity compensation

In order to overcome the problem of backlash nonlinearity and parameter time-varying in mechatronic servo systems, a chattering free full order sliding mode control strategy is proposed. The dead zone model of the backlash nonlinearity can be approximated by the proposed differentiable function. The superposition of the approximation error, the unmodeled dynamics, and the external disturbance can be regarded as the disturbance-like term. The continuous state-space model of the servo systems with the backlash nonlinearity is established and divided into three subsystems. The terminal sliding mode control law is constructed based on the backstepping design principle, which can make the tracking error converge to an arbitrarily small residual within finite time and achieve the precise compensation of the backlash. The finite-time convergence condition of the closed-loop system is analyzed using the Lyapunov theory. The experimental test verifies the effectiveness of the proposed control approach. © 2016, The editorial office of Transaction of China Electrotechnical Society. All right reserved.