Dynamics Modeling and Control Method for Non-Cooperative Target Capture with a Space Netted Pocket System

Vehicle platoon is one of the innovations in the automated highway systems, which has the potential to reduce fuel consumption, alleviate traffic congestion and lighten the driver’s burden. How to control the vehicle effectively to ensure the stability of the queue is a challenge. Aiming to overcome the shortcomings of the platoon control method based on traditional sliding mode control, a non-singular terminal sliding mode control method optimized by the extreme learning machine is proposed in this paper. Firstly, the vehicle longitudinal dynamics are derived from the analysis of the forces acting on the vehicle in the longitudinal direction. A constant time headway policy is taken as the spacing policy. The modified non-singular terminal sliding mode control method has outstanding performance, simulation results demonstrate that the following vehicles can rapidly track the trajectory of the leading vehicle in the platoon with less spacing error and guarantee string stability. In this study, several experiments are set up to consider the disturbance and other uncertain practical factors. The performance of the proposed method is superior to the traditional sliding mode control method. Experimental results show that the proposed method can significantly reduce chattering and has good robustness under the circumstances of the disturbance.

To eliminate the effect of the uncertain disturbances and improve the control accuracy of spacecraft Attitude Control System, a nonlinear control algorithm named nonsingular terminal sliding-mode feedback controller is proposed in this work, which is mainly made up of nonsingular terminal sliding-mode controller and sliding-mode feedback controller. In the first place, nonsingular terminal sliding-mode controller is designed, which guarantees global asymptotic convergence of the attitude in the presence of the uncertain perturbations from the space. Despite that, it is the influence of the uncertain disturbances that hinder the control accuracy. Then, in order to promote the control accuracy, the sliding-mode feedback controller based on the principle of minimum sliding-mode error is proposed, which is used to compensate the control errors of the nonsingular terminal sliding-mode controller caused by the uncertainties. Hence, the determination principle of the weighting matrix in sliding-mode feedback controller is discussed, and the algorithm structure of the sliding-mode feedback controller is also analyzed, which provides the theoretical basis for the sliding-mode feedback controller. By contrast, an adaptive fuzzy algorithm is designed and introduced into the nonsingular terminal sliding-mode controller to improve the control accuracy, which named the nonsingular terminal fuzzy sliding-mode controller. Last but not the least, several numerical examples are presented to demonstrate the efficacy of the proposed nonsingular terminal sliding-mode feedback controller. Simulation results confirm that the control accuracy of the nonsingular terminal sliding-mode feedback controller is higher than the nonsingular terminal sliding-mode controller and the same as nonsingular terminal fuzzy sliding-mode controller. Not only is the calculation of the nonsingular terminal fuzzy sliding-mode feedback controller smaller than nonsingular terminal fuzzy sliding-mode controller, the adjusted parameters are also fewer than nonsingular terminal fuzzy sliding-mode controller obviously. The numerical results clearly indicate that the proposed nonsingular terminal sliding-mode feedback controller based on the principle of minimum sliding-mode error can compensate control errors accurately and quickly; therefore, it can reduce the effect of the uncertainties from the space indirectly.

For a hybrid mechanism for automobile electro-coating conveying which is self-developed, a dynamic model is established based on screw theory and the principle of virtual work to simplify the process of modeling. Then, to solve the chattering problem and the slow rate of convergence problem of the existing sliding mode control methods for the hybrid mechanism, a super-twisting algorithm based second-order nonsingular fast terminal sliding mode control method is proposed. The stability of the proposed control method is proved by Lyapunov stability theorem. Finally, compared with the reaching law based sliding mode control method and the super-twisting algorithm based second-order sliding mode control method, it is indicated from the simulation and experiment results that the proposed control method not only has high steady-state accuracy, better dynamic performance and strong robustness, but also reduces the chattering and improves the rate of convergence of the system. And it lays foundation for realizing the high performance control of the hybrid mechanism for automobile electro-coating conveying.

This paper proposes a Disturbance-Compensated Non-Singular Fast Terminal Sliding Mode Control (DC-NFTSMC) method to address the issues of slow convergence speed and poor robustness in traditional turntable control methods. By designing an improved non-singular fast terminal sliding mode surface and reaching law, the convergence speed of the turntable system is significantly enhanced. Additionally, an Extended State Observer (ESO) is incorporated to estimate and compensate for complex disturbances and improving the robustness of the turntable system. Simulation results demonstrate that, compared with traditional methods, this control method not only effectively improves the tracking response speed of the turntable system but also ensures superior robustness in the presence of multiple superimposed disturbances.

In order to solve the attitude synchronization control problem of an on-orbit servicing spacecraft autonomously docking to a tumbling satellite with the unknown bounded disturbances and system uncertainties, a fast terminal sliding mode control law is presented in this paper. The most important contribution of this paper is to design an attitude synchronization control law, which will be realized by the terminal sliding mode control method, for a servicing spacecraft autonomously docking to a freely tumbling satellite in space. First of all, the model of relative attitude dynamics is derived from the attitude dynamics of servicing spacecraft and tumbling satellite. Then, the relative attitude dynamic model is converted to the normal formation to apply the control method of fast terminal sliding mode. Furthermore, a fast terminal sliding mode control law for attitude synchronization is designed based on the normal formation of relative attitude dynamic model. During the design process of the control law, the measurement errors and parameter variations are also considered. Finally, several numerical simulations are conducted to verify the designed attitude synchronization control law, and the results verified the effectiveness of the designed control law. Moreover, it's robustness to the unknown bounded disturbances, system uncertainties and measurement errors has also been demonstrated.

In order to cope with the changing industrial operation environment, based on the Flexible Joint Robot systems (FJR), this paper explores a control method of decoupling high-order systems by using singular perturbation theory (SPT). Considering the limitations of SPT in FJR systems, the method of introducing a saturated flexible compensator is used to change the premise that the joints need to be assumed to be weakly flexible, thereby expanding the application scope of SPT in such systems. Moreover, the improved third-order time-varying parameters extended state observer is used to observe the lumped interferences which can effectively suppress the peak problem caused by the initial value, and the adaptive continuous nonsingular fast terminal sliding film control method is combined to control the slow subsystem. Aiming at the fast subsystem, the integral flow is used to reconstruct and fast terminal sliding mode control method is combined to improve the initial oscillation problem.

A Global Fast Terminal Sliding Mode Controller (GFTSMC) is proposed for n-link robotic manipulators by employing the Fast Terminal Sliding Mode (FTSM) control concept in both the reaching phase and the sliding phase. Under the control, the system states will reach FTSM in desired finite time and then converge to the origin along the FTSM in specified finite time, resulting in a reduced steady tracking error in comparison with the conventional sliding mode controller. The proposed controller is continuous and therefore chattering-free. An example is presented to demonstrate its effectiveness.

This paper investigates the trajectory-tracking problem of an uncertain quadrotor in the presence of complex disturbances. A new fractional-order terminal sliding mode control method (FOTSMC) is designed for a quadrotor attitude, which can increase the control robustness against the external disturbances and modeling uncertainty, and decrease the chattering problem. A new fractional non-integer sliding mode control technique for a quadrotor position is designed to stabilize its state variables and attenuate wind disturbance and the effects of variation in the mass. The stability analysis is studied by the Lyapunov theory. Numerical simulation for complex flight trajectory under disturbances is given to illustrate the validity of the proposed methods.

In order to realize the trajectory tracking control of mobile robots, a global fast terminal sliding mode control method is proposed in the kinematic analysis. Based on the combination of the backstepping method and the thought of the fast terminal sliding mode control, the method is more superior than the backstepping design method on convergence time and convergence rate. The system state variables are designed based on based backstepping method, then, the controller is applied to mobile robot system by recursive structure of second order fast terminal sliding mode, the control law is designed by Lyapunov method. Finally, simulation results show the validity of the presented method.

This paper deals with utilizing a recursive singularity-free fast terminal sliding mode control method for finite-time robust tracking control in a class of nonholonomic systems described by an extended chained form. To enhance the performance of the proposed method, the constrained parameters in the controller are exactly tuned using evolutionary algorithms such that the tracking error reaches zero in a short time and without chattering. A comparative study is also presented among the applied evolutionary algorithms namely differential evolution, bat optimization, cuckoo optimization and bacterial foraging optimization. Applying the proposed design method leads to a considerable reduction in convergence time of the states as well as the chattering phenomenon. It is shown that the method is robust against disturbance in the input of the system. Numerical simulations for a well-known nonholonomic system, i.e., wheeled mobile robot demonstrate effective improvement in the results compared with conventional terminal sliding mode control method. DOI: http://dx.doi.org/10.5755/j01.itc.47.1.15031

The paper presents a method of synthesizing the Variable Structure Controller (VSC) based on the Fast Terminal Sliding Mode (FTSM) control for an optoelectronic observatory to eliminate the effects of the vibration and the change of vehicle’s direction. An improved fast terminal sliding surface and a fuzzy saturation function have been proposed to develop the improved fast terminal sliding mode variable structure controller (IFTSM-VSC). Based on the theory of Lyapunov stability, the article has proved that the IFTSM-VSC controller ensures the Line of Sight (LOS) stabilization of the observation devices and ensures the tracking errors converge to zero in finite time. The simulation uses data about the vibration and navigation of the vehicle recorded on some streets and roads. Simulation results in Matlab/Simulink show the effectiveness of the IFTSM-VSC controller.

In this paper, a nonsingular, essentially continuous and finite-time convergent impact angle constrained guidance law for intercepting stationary, constant speed, and maneuvering targets is developed using advanced terminal sliding mode control schemes and extended state observer. In order to achieve the specified intercept angle in finite time without singularity, the nonsingular fast terminal sliding mode control algorithm is employed to construct sliding surface. The fast terminal sliding mode control technique is used to establish the reaching law, so the system trajectory converges quickly from initial state to the switching surface in the whole reaching phase and the proposed guidance law is essentially continuous. Noticing the interception of a maneuvering target, the unknown target acceleration is estimated and compensated using extended state observer. Due to its inherent attribute of singularity-free, continuity, and faster convergence rate, no approximation is necessary in the implementation of the proposed guidance law, so better tracking accuracy of the desired intercept angle in a shorter time with a smoother guidance command can be guaranteed compared with conventional terminal sliding mode guidance law. A large number of numerical simulations are implemented to justify the effectiveness of the proposed guidance law.

A backstepping nonsingular fast terminal sliding mode control with the extended state observer (ESO) is proposed for the uncertain factors of nonlinear spinning missile. Based on Lyapunov stability theory, the virtual control as sliding mode is taken in the backstepping design and then the tracking differentiator (TD) is employed to eliminate the “explosion of terms”. In the last step of the backstepping design, nonsingular fast terminal sliding mode control is utilized to drive the angular velocity tracking error to converge to the origin in a finite period of time. To estimate the chattering phenomenon caused by disturbance influence variable in the system, an ESO is applied to estimate and compensate the impact from uncertainties and disturbances. The stability of the closed-loop system is proved. The simulation results show the effectiveness of the proposed control method and the stability of the controller.

This work proposes a non-singular fast terminal sliding mode control (NFTSMC) strategy based on the Twin Delayed Deep Deterministic Policy Gradient (TD3) algorithm and a nonlinear disturbance observer (NDO) to address the issues of modeling errors, motion disturbances, and transmission friction in robotic manipulators. Firstly, a novel modular serial 5-DOF robotic manipulator configuration is designed, and its kinematic and dynamic models are established. Secondly, a nonlinear disturbance observer is employed to estimate the total disturbance of the system and apply feedforward compensation. Based on boundary layer technology, an improved NFTSMC method is proposed to accelerate the convergence of tracking errors, reduce chattering, and avoid singularity issues inherent in traditional terminal sliding mode control. The stability of the designed control system is proved using Lyapunov stability theory. Subsequently, a deep reinforcement learning (DRL) agent based on the TD3 algorithm is trained to adaptively adjust the control gains of the non-singular fast terminal sliding mode controller. The dynamic information of the robotic manipulator is used as the input to the TD3 agent, which searches for optimal controller parameters within a continuous action space. A composite reward function is designed to ensure the stable and efficient learning of the TD3 agent. Finally, the motion characteristics of three joints for the designed 5-DOF robotic manipulator are analyzed. The results show that compared to the non-singular fast terminal sliding mode control algorithm based on a nonlinear disturbance observer (NDONFT), the non-singular fast terminal sliding mode control algorithm integrating a nonlinear disturbance observer and the Twin Delayed Deep Deterministic Policy Gradient algorithm (TD3NDONFT) reduces the mean absolute error of position tracking for the three joints by 7.14%, 19.94%, and 6.14%, respectively, and reduces the mean absolute error of velocity tracking by 1.78%, 9.10%, and 2.11%, respectively. These results verify the effectiveness of the proposed algorithm in enhancing the trajectory tracking accuracy of the robotic manipulator under unknown time-varying disturbances and demonstrate its strong robustness against sudden disturbances.

This paper investigates trajectory tracking control of a dielectric electro-active polymers (DEAP) actuator with hysteresis nonlinearity by using second-order adaptive discrete-time fast terminal sliding mode control (2-ADFTSMC) scheme. Taking into account that the hysteresis behaviour is asymmetric rate-dependent, a Hammerstein model is established to represent the DEAP actuator. Then, based on a novel 2-ADFTSM function and a terminal-sliding-mode-type switching control law, a 2-ADFTSMC scheme is proposed to improve the trajectory tracking performance. Furthermore, the stability of the closed-loop system is proved. Compared with discrete-time sliding mode control (DSMC) and discrete-time fast terminal sliding mode control (DFTSMC) schemes, the proposed control scheme can provide higher tracking accuracy, faster convergence speed, and stronger robustness in presence of model uncertainties and external disturbances. The effectiveness and practicality of the proposed control scheme are validated through the experiments on the DEAP actuator.