This article’s primary motivation is to propose a nonsingular and continuous terminal sliding-mode (TSM) control with reduced chattering, which is able to rapidly stabilize the second-order plant with high precision. To this end, a novel sliding-mode manifold, coined as practical TSM (PTSM) one, is first constructed. Once the proposed sliding surface is reached, a Lipschitz-continuous but slope-steep generalized velocity will be established at the origin such that the global nonsingularity of the equivalent control is ensured. The fast dynamic response with local high gain characterizes the sliding behavior inside the unit neighborhood of the origin. Importantly, the analytical solution of the proposed sliding-mode reduced-order system is deduced, which indicates that the finite time taken to slide into a preset small neighborhood of the origin can be calculated. The above designability of convergence time is necessary for control practices with accurate time sequence planning. Further, the corresponding globally singular-free PTSM reaching law with reduced chattering is designed based on the super-twisting algorithm. Finally, several groups of linear-motor-based control experiments verify the superiorities of proposed controllers.

This article focuses on the fast position tracking problem for the permanent magnet linear motor (PMLM) system under a chattering-reduced sliding mode control signal. To this end, a class of globally nonsingular sliding mode control (SMC) laws, called logarithmic sliding mode (LnSM) control, is proposed in this article. Using the natural logarithm function, a high gain is established at the equilibrium of the sliding mode reduced-order system, which leads to a higher tracking precision and a faster local convergence rate than those of some classical SMCs. In addition, a super-twisting algorithm-based LnSM (ST-LnSM) control is constructed to reduce the chattering typical for first-order SMC, while stabilizing the position tracking system rapidly. Since only a few parameters need to be adjusted, and the employed natural logarithm function is conventionally integrated into most PMLM drivers, the proposed control law is easy to implement in PMLM systems or other industrial servo systems.

This article presents a 6-DOF attitude-orbit synchronous control problem for the space circumnavigation (SCN) mission with parameter uncertainties, time-varying uncertainties, and input constraints. In particular, from the perspective of engineering application, time-varying measurement uncertainties are taken into account of the 6-DOF attitude–orbit coupling kinematics and dynamics, and the analytical solution of the desired attitude is derived based on the measured relative orbit information with measurement uncertainties. To drive the active spacecraft approach to the faulty target safely, a time-varying exponential prescribed convergence boundary is introduced into the sliding surface. A finite-time disturbance observer is involved in equivalent tracking errors for compensating the mismatched uncertainties. In addition, an auxiliary system is designed to overcome the instability danger caused by input constraints. The stability of the controlled system is discussed in the nonautonomous finite-time stable framework, which is proved via Lyapunov analysis that the attitude-orbit tracking errors converge to the equilibrium within finite time. The simulation experiment with mismatched uncertainties and prescribed constraints shows the superiority of the designed control scheme.

This article focuses on the high-precision position tracking problem for the free-float space manipulator (FFSM) system subject to parametric uncertainties, input saturation, and state constraints. To this end, the screw-based dynamics using the Newton-Euler iterative method, with a global and unique attitude representation, are established; then, a chattering-free fixed-time sliding-mode control (FTSMC) scheme is developed based on the proposed dynamics model. A radial basis function neural network (RBFNN) with proper hidden layers and nodes is integrated into the proposed controller while modeling approximation errors are well-inhibited by adaptive laws. Since the tracking error has been explicitly constrained by an exponential decay function, the Lyapunov analysis indicates that the transient, steady performance and state constraints can be guaranteed simultaneously. Simulation experimentstakinganFFSMwith6-DOFillustratetheeffectiveness of the proposed control scheme from two aspects: joint-space positioning and trajectory tracking.

This article concerns the guaranteed trajectory estimation problem for unmanned surface vehicles (USVs) via set-membership estimation technique. Taking both rigid-body and hydrostatics kinetics into consideration, the nonlinear dynamic model of USV system is derived, where the parameters of system are all unknown. Considering external disturbance and nonlinearities, an offline data-based set-membership estimation algorithm of unknown system parameters is proposed to obtain the set representation of system parameters, which contain the actual parameters of USV. Then, based on the obtained parameter sets, an online guaranteed trajectory estimation algorithm of USV is constructed to provide guaranteed sets enclosing actual trajectory points of USV, which consists of a time-update step and measurement-update step. To tackle the nonlinear transformation of zonotopes, both interval arithmetic and Taylor model are utilized to provide rigorous bounds for nonlinear function. Finally, simulation results on a USV dynamic are provided to demonstrate the effectiveness of the proposed data-based guaranteed trajectory estimation method for USVs.