Nonlinear Sliding Mode Control Scheme Research Articles

Disturbance Observer-Based Nonsingular Terminal Sliding Mode Control for Spacecraft Electromagnetic Docking

This paper presents a novel nonlinear sliding mode control scheme that combines on-line model modification, a nonlinear sliding mode controller, and a disturbance observer to solve the essential problems in spacecraft electromagnetic docking control, such as model uncertainties, unknown external disturbances, and inherent strong nonlinearity and coupling. An improved far-field model of electromagnetic force which is much more accurate than the widely used far-field model is proposed to enable the model parameters to be on-line self-adjusting. Then, the relationship between magnetic moment allocation and energy consumption is derived, and the optimal direction of the magnetic moment vector is obtained. Based on the proposed improved far-field model and the research results of magnetic moment allocation law, a fast-nonsingular terminal mode controller driven by a disturbance observer is designed in the presence of model uncertainties and external disturbances. The proposed control method is guaranteed to be chattering-free and to possess superior properties such as finite-time convergence, high-precision tracking, and strong robustness. Two simulation scenarios are conducted to illustrate the necessity of modifying the far-field model and the effectiveness of the proposed control scheme. The simulation results indicate the realization of electromagnetic soft docking and validate the merits of the proposed control scheme. In the end of this paper, some conclusions are drawn.

A novel active disturbance rejection control with hyperbolic tangent function for path following of underactuated marine surface ships

This paper presents a TADRC method via active disturbance rejection control (ADRC) with hyperbolic tangent function for path following of underactuated surface ships with input constraint, heading rate constraint, parameters uncertainties, as well as environment disturbances. The line of sight (LOS) guidance scheme that computes the desired heading angle on basis of cross tracking error and a look ahead distance, converts path following into heading control, and also renders good helmsman behavior. Moreover, hyperbolic tangent function is introduced to modify the linear extended state observer (LESO) to design a nonlinear observer (TESO) for promoting the estimation performance of the heading, heading rate and total disturbances including parameters uncertainties and environmental disturbances. Then, the linear error feedback control is modified by a nonlinear sliding mode control scheme with hyperbolic tangent function to handle the heading rate constraint and to obtain the better control action. Furthermore, the feedback control law is embedded in a standard Quadratic Programming (QP) cost function to handle the input constraints including rudder saturation and rudder rate limit. Finally, the comparison simulation demonstrates the effectiveness of the proposed method for the underactuated ship’s path following.

Sliding-Mode Observer for IPMSM Sensorless Control by MTPA Control Strategy

Abstract: This paper presents a nonlinear sliding mode control (SMC) scheme for interior permanent magnet synchronous motors (IPMSMs).The proposed SMC is able to reduce the settling time without an overshoot by giving a low damping ratio at the initial time and a high damping ratio as the output reaches the desired setpoint. At the same time, it enables a fast convergence in finite time. To improve the efficiency of a system in the constant torque region, the control system incorporates the maximum torque per ampere (MTPA) algorithm. The stability of the nonlinear sliding surface is guaranteed by Lyapunov stability theory. The effectiveness of the proposed nonlinear SMC scheme is verified experimentally. From these experimental results, the proposed nonlinear SMC method reveals a faster transient response, smaller steady-state speed error, and low sensitivity to system uncertainties.

Fast sliding mode control on air-breathing hypersonic vehicles with transient response analysis

This article studies the tracking control of air-breathing hypersonic vehicles to the reference velocity and the reference altitude with a fast non-linear sliding mode control scheme. By the feedback linearization technology, the longitudinal model of air-breathing hypersonic vehicles is divided into the velocity subsystem and the altitude subsystem. Two lumped tracking error variables are developed based on velocity and altitude subsystems, and non-singular terminal sliding mode control is used so that the two lumped error variables converge to the origin in finite time. During the tracking process, transient properties of non-singular terminal sliding mode control are investigated from the mathematical and theoretical standpoint. The simulation results have shown that the fast non-linear sliding mode control is effective for the tracking control of air-breathing hypersonic vehicles and have demonstrated that the relevant transient response analysis is correct.