Zhu Liangkuan

Compound Control Strategy for MDF Continuous Hot Pressing Electrohydraulic Servo System with Uncertainties and Input Saturation

A compound control strategy is investigated for Medium Density Fiberboard (MDF) continuous hot pressing electrohydraulic servo system (EHSS) with uncertainties and input saturation. Firstly, a hyperbolic tangent function is applied to approximate saturation nonlinearity in the system. And thus the mathematical model is continuous and differentiable. Subsequently, the slab thickness tracking controller is constructed by using a dynamic surface control (DSC) method, which introduces first-order low-pass filters to calculate derivatives of virtual control input in each step. Compared with the conventional backstepping controller, complexity of the design procedure is alleviated obviously. Moreover, a composite disturbance of uncertainties and input saturation is estimated by a nonlinear disturbance observer for compensation of the control law. Finally, an appropriate Lyapunov function is chosen to prove that all signals of the closed-loop system are semiglobally uniformly ultimately bounded and the tracking error converges to zero asymptotically. Numerical simulation results are also exhibited to authenticate and validate the benefits of the proposed control scheme.

Adaptive backstepping sliding mode control of MDF hot press hydraulic system based on fuzzy disturbance observer

In order to realize high-precision position tracking control for (Medium Density Fiberboard, MDF) continuous hot press hydraulic position servo system in the presence of interior parameter perturbations and external load disturbance, an adaptive backstepping sliding mode control strategy with fuzzy disturbance observer (FDO) is presented. Firstly, a modified FDO is designed to estimate and compensate the interior parameter perturbations and external load disturbance of the system. Secondly, the backstepping sliding mode controller is designed and adaptive algorithm is used to online estimate the uncertainty of the system. Thirdly, the convergence of tracking error and the asymptotic stability of system are strictly proved according to Lyapunov stability theory. The results of simulation experiments indicate that the controller has strong robustness against the interior parameter perturbations and external load disturbance. Moreover, the controller has good performance including fast response, high tracking accuracy and small steady-state error.