The design of nonsingular terminal sliding-mode feedback controller based on minimum sliding-mode error

Switching sliding-mode control strategy based on multi-type restrictive condition for voltage control of buck converter in auxiliary energy source

To improve the control precision of nonlinear spacecraft formation flying, the input–output linearization minimum sliding-mode error feedback controller is presented based on the linear-decoupled spacecraft formation model by input–output linearization method incorporating the sliding-mode control. This paper proposes a new strategy to estimate and offset the system-control errors, which include various kinds of uncertainties and disturbances. To facilitate the analysis, the linear-decoupled spacecraft formation model is first given; on which basis, the concept of equivalent control error is introduced to define the entire model error. Based on the minimum sliding-mode covariance constraint, a cost function is formulated to estimate the equivalent control error and fed back to the conventional sliding-mode control. It is shown that the sliding mode after the input–output linearization minimum sliding-mode error feedback controller will approximate to the ideal sliding mode with high-control precision. In addition, the new methodology is applied to spacecraft formation flying. It guarantees global asymptotic convergence of the relative-tracking error in the presence of the large perturbations. More exactly, the two input–output linearization minimum sliding-mode error feedback controller laws (continuous sliding-mode control and nonsingular terminal sliding-mode control) are developed for this spacecraft formation flying system. Several fault-tolerant scenarios are considered to verify that the input–output linearization minimum sliding-mode error feedback controller is still effective in the presence of faults in spacecraft thrusters. Numerical simulations are performed to demonstrate the efficacy of the proposed methodology to maintain and reconfigure the spacecraft formation with existence of initial offsets and large perturbations effects.

Fault tolerant small satellite attitude control using adaptive non-singular terminal sliding mode

This study investigates the control performance of a structural building system during a seismic scenario using an adaptive nonsingular terminal sliding mode control. To realize the structural integrity of a building, it is necessary to equip the building with a structural control device. This research is focused on a hybrid control device that has excellent characteristics of passive and active control devices and implemented in a three degree-of-freedom system. The system, actuator, and controllers are designed by using the mathematical model developed in MATLAB/Simulink. The input excitation to the structure is taken from the El Centro earthquake that occurred in the 1940s with a magnitude of 6.9 Mw and the Southern Sumatra earthquake that occurred in 2007 with a magnitude of 8.4 Mw. Adaptive nonsingular terminal sliding mode control is the new proposed control strategy to be applied in structural control field is investigated in terms of controller performance in suppressing the vibrations, and then, compared with sliding mode control and fuzzy logic controller strategies. Sliding mode control is chosen to be compared with adaptive nonsingular terminal sliding mode control because of its advantages of robust performance, whereas fuzzy logic controller is chosen because of its intelligent control base. The effectiveness of the proposed controllers is evaluated based on the displacement response, performance indices, and the probability of building damage. The results have shown that the new proposed controller, an adaptive nonsingular terminal sliding mode control, reduced vibrations better and has superior performance compared with fuzzy logic controller and sliding mode control.

Finite time positioning control for a stratospheric airship

There are various uncertain factors such as parameter perturbation and external disturbance during the steering process of a permanent magnet slip clutch electronically controlled hydraulic power steering system (P-ECHPS) of medium and heavy duty vehicles, which is an electronically controlled hydraulic power steering system based on a permanent magnetic slip clutch (PMSC). In order to avoid the immutable single assistance characteristic of a hydraulic power steering system, a PMSC speed-controlled model and P-ECHPS of each subsystem model were studied. Combined with non-singular terminal sliding mode and fast terminal sliding mode, an Adaptive Non-singular Fast Terminal Sliding (ANFTS) mode control strategy was proposed to control precisely the rotor speed of the PMSC in P-ECHPS, thus achieving better power control for the entire P-ECHPS system. The simulation results show that adaptive nonsingular fast terminal sliding mode control enables PMSC output speed to track the target speed. Compared with the non-singular terminal sliding mode control and the ordinary sliding mode control, the convergence speed has been improved by 66.7% and 84.2%, respectively. The rapid control prototype test of PMSC based on dSPACE (dSPACE is a development and verification platform based on MATLAB/Simulink software.) was carried out. The validity of the adaptive NFTSM algorithm and the correctness of the offline simulation results are validated. The adaptive NFTSM algorithm have better robustness and can realize variable assist characteristics and save energy.

This paper presents a trajectory control scheme for a non-holonomic differential drive mobile robot using the Non-singular Terminal Sliding Mode (NTSM) control method. The proposed approach, in fact, is a cascade control system scheme with the NTSM based dynamic controller at the internal loop which tracks the robot’s velocity quantities and a kinematic controller at the outer loop to regulate the robot’s position. In this manner, the control performance is robust to both disturbances and model’s uncertainties, as well as guarantees fast, finite-time convergence at better tracking precision. The simulation results demonstrate the merit of the anticipated control scheme.

Nonsingular terminal sliding mode control technique for attitude tracking problem of a small satellite with combined energy and attitude control system (CEACS)

To restrain chaotic oscillation in power system, a nonsingular terminal sliding-mode (NTSM) controller with nonlinear disturbance observer based on a novel reaching law is proposed in this paper. In order to obtain faster convergence of state variables, a novel reaching law is employed in this paper, which can shorten the reaching time and weaken system chattering. Based on this reaching law, a NTSM controller is developed to suppress and eliminate the chaos oscillation in power system. Comparing with the other control algorithms, simulation results verify the effectiveness of the proposed methods.

Background: As a control strategy of industrial robots, sliding mode control has the advantages of fast response and simple physical implementation, but it still has the problems of chattering and low tracking accuracy caused by chattering. This paper proposes a new sliding mode control strategy for the application of industrial robot control, which effectively solves these problems. Methods: In this paper, a deep deterministic policy gradient–nonlinear nonsingular fast terminal sliding mode control (DDPG–NNFTSMC) strategy is proposed for industrial robot control. In order to improve the tracking control accuracy and anti-interference ability, DDPG is used to approach the uncertainties of the system in real time, which ensures the robustness of the system in various uncertain environments. Lyapunov function is used to prove the stability and finite time convergence of the system. Compared with the nonsingular terminal sliding mode control (NTSMC), the time to reach the equilibrium point is shorter. With the help of MATLAB/Simulink, the tracking accuracy and control effects are compared with traditional terminal sliding mode control (TSMC), NTSMC and radial basis function–sliding mode control (RBF–SMC), the results showed that it had the advantages of nonsingularity, finite time convergence, small tracking error. The motion accuracy and anti-interference ability of the uncertain manipulator system was further improved, and the chattering problem of the system in the motion process is effectively eliminated.

Purpose The purpose of this paper is to propose an indirect design for sliding surface as a function of position and velocity of each joint (for mounted manipulator on base) and center of mass of mobile base which includes rotation of wheels. The aim is to control the mobile base and its mounted arms using a unified sliding surface. Design/methodology/approach A new implementation of sliding mode control has been proposed for wheeled mobile manipulators, regulation and tracking cases. In the conventional sliding mode design, the position and velocity of each coordinate are often considered as the states in the sliding surface, and consequently, the input control is found based on them. A mobile robot consisted of non-holonomic constraints, makes the definition of the sliding surface more complex and it cannot simply include the coordinates of the system. Findings Formulism of both sliding mode control and non-singular terminal sliding mode control were presented and implemented on Scout robot. The simulations were validated with experimental studies, which led to satisfactory analysis. The non-singular terminal sliding mode control actually had a better performance, as it was illustrated that at time 10 s, the error for that was only 8.4 mm, where the error for conventional sliding mode control was 11.2 mm. Originality/value This work proposes sliding mode and non-singular terminal sliding mode control structure for wheeled mobile robot with a sliding surface including state variables: center of mass of base, wheels’ rotation and arm coordinates.

This paper is focused on the development of a general approach to design Nonsingular Terminal Sliding Mode Controllers (NTSMC) for DC-DC Power Converters by considering some concepts of the Linear Sliding Mode Control with constant switching frequency in order to present two types of NTSM controllers. Thus, the main purpose of these controllers is to guarantee a finite time convergence avoiding singularities of the Terminal Sliding Mode Control as well as the asymptotical convergence of the Linear Sliding Mode Control and the infinite switching frequency which can damage the electronic components. Moreover, due to the lack of a method to select the coefficients of the NTSMC, a Particle Swarm Optimization (PSO) based on different Cost Functions is proposed to handle the proper selection of them. Finally, simulation results are presented to validate the performance of the proposed controllers with their coefficients optimized. In the case of the first NTSM controller, called Duty Cycle Controller, the best settling time obtained was about 3.56 milliseconds while with the second one, called Reaching Law Controller, the best settling time obtained was 3.34 milliseconds. On the other hand, both controllers maintain their stability in the presence of parameter variations such as load resistance or input voltage; however, the Reaching Law Controller exhibits the fastest response.

Controller design for nonlinear systems in its general form is complicated and an open problem. Finding a solution to this problem becomes more complicated when unwanted terms, such as disturbance, are taken into account. To provide a robust design for a subclass of nonlinear systems, sliding mode controllers (SMCs) are used. These controllers have a systematic design procedure and can reject bounded disturbances and at the same time guarantee stability. The guaranteed stability is achieved by separating system states into two parts and assuming that the input to state stability (ISS) condition holds for internal dynamics. This condition restricts the applicability of the SMC and limits the system performance when the controller is designed based on that. In order to remove this restriction and improve the performance, the ISS condition has been relaxed in this study. The relaxation is performed by redesigning SMCs based on suggested Lyapunov functions. The proposed idea insures global asymptotic stability of the closed loop system and is used to revise different well-known SMCs such as conventional SMC, terminal SMC, non-singular terminal SMC, integral SMC, super-twisting SMC, and super-twisting integral SMC. Comparisons between conventional and revised versions are made using simulation to demonstrate excellence of the revisited controllers.

A nonsingular terminal sliding mode controller (NTSMC) based on a direct torque control is presented for a switched reluctance motor (SRM) in this article. To guarantee dynamic stability, the nonsingular terminal sliding mode based on an improved reaching law (RL) is employed to design the speed controller. The torque ripple of the system can be suppressed, and the disturbance caused by uncertainties, such as load disturbance and parameter perturbation, can be suppressed by the proposed NTSMC. Moreover, the gray wolf optimization algorithm is applied to automatically adjust the parameters of the controllers and the value of given flux, thereby acquiring a satisfactory result. The NTSMC is validated by both simulation and experimental results with a six-phase 12/10 SRM. Compared with PI and conventional sliding mode control, NTSMC improves the convergence rate of state and exhibits better performance in torque ripple reduction and antidisturbance ability. The robustness and dynamic performance of the system can be ensured.

To achieve high performance tracing control of the three-links spatial robot, a nonsingular terminal fuzzy sliding mode control method is proposed in this paper. Firstly, the control method can efficiently avoid the singularity of the generally terminal sliding mode controller through designing nonsingular terminal sliding mode surface. Secondly, to diminish the chattering in the control input, a fuzzy controller is designed to adjust the gain of nonsingular terminal sliding mode controller according to the normal of nonsingular terminal sliding mode surface. The stability of the control scheme is verified by using Lyapunov theory. The proposed controller is then applied to the control of a three-links spatial robot. Simulation results show the validity of the proposed control scheme.