Adaptive Super-twisting Sliding Mode Control Research Articles

Adaptive super-twisting non-singular terminal sliding mode control for tracking of quadrotor with bounded disturbances

In this research, a novel adaptive non-singular terminal sliding mode control (ANTSMC) is proposed for finite-time attitude and altitude tracking of aircraft system considering the bounded disturbances. By utilizing this structure, the desired reference is tracked in finite-time. Afterward, a new adaptive super-twisting sliding mode control (ASTSMC) is presented to decrease the control signals' chattering effect. This approach combines with the ANTSMC to compose this study's proposed approach as adaptive super-twisting non-singular terminal sliding mode control (ASTNTSMC). Additionally, an adaptive-regulation strategy is designed for estimating the unknown bounds of the disturbances. Finally, for evaluating the proposed strategies' ability, some simulations are performed based on quadrotor real parameters and confirmed the presented controllers' appropriate performances compared to other techniques.

Output feedback adaptive super-twisting sliding mode control of hydraulic systems with disturbance compensation

This paper presents an output feedback adaptive super-twisting sliding mode controller (SSMC) for hydraulic systems with unmodeled disturbances via utilizing an extended state observer (ESO). Both unmeasured system states and unmodeled disturbances are estimated by ESO based on output position signal, which avoids using noise-polluted signals and eliminates most of the disturbance effects on control performance simultaneously. Moreover, a SSMC is developed to further suppress the residual error of disturbance compensation, in which feedback gains are adapted online to further reduce the high-gain feedback. In addition, this proposed controller is continuous and chattering-free, which is beneficial to practical applications. Theoretical analysis indicates that the proposed controller ensures an asymptotic stability when existing constant disturbances, and ultimately bounded tracking performance for the time-variant disturbance case. Comparative experimental results reveal the validity of the developed approach.

Capture dynamics and control of tethered space net robot for space debris capturing in unideal capture case

Tethered Space Net Robot (TSNR) is proposed as a hopeful solution for space debris capturing. An unideal case of net capture is studied in this paper, in which the net does not contact the target in the center of the net. For this case, the net cannot naturally close to wrap around the target completely after collision due to the asymmetric net configuration. Therefore, an integral adaptive Super-Twisting sliding mode control (IASTSMC) is designed to close the net. The control algorithm consists of a nonlinear integral sliding surface and adaptive Super-Twisting sliding mode control (ASTSMC), which not only has the property of “saturate the large error, magnify the small error”, but also provides a positive chattering alleviation effect. Compared with the nonlinear integral sliding mode control (ISMC) with equivalent control technique and the original Super-Twisting algorithm (STA), the proposed control method shows a better performance to close the net in this unideal case.

Adaptive Backstepping Sliding Mode Control of Air-Breathing Hypersonic Vehicles

In this paper, a controller combining backstepping and adaptive supertwisting sliding mode control method is proposed for altitude and velocity tracking control of air-breathing hypersonic vehicles (AHVs). Firstly, the nonlinear longitudinal model of AHV is introduced and transformed into a strict feedback form, to which the backstepping method can be applied. Considering the longitudinal trajectory tracking control problem (altitude control and velocity control), the altitude tracking control system is decomposed to several one-order subsystems based on the backstepping method, and an adaptive supertwisting sliding mode controller is designed for each subsystem, in order to obtain the virtual control variables and actual control input. Secondly, the overall stability of the closed-loop system is proved by the Lyapunov stability theory. At last, the simulation is carried out on an AHV model. The results show that the proposed controller has good control performances and good robustness in the parameter perturbation case.

Adaptive super-twisting sliding mode control for micro gyroscope based on double loop fuzzy neural network structure

In this paper, a new adaptive super-twisting sliding mode control (STSMC) scheme based on a double loop fuzzy neural network (DLFNN) is proposed to solve the problem of the external disturbances and approximate the unknown model for a micro gyroscopes. The STSMC algorithm can effectively suppress chattering since it can hide the high-frequency switching part in the high-order derivative of the sliding mode variable and transfer the discrete control law to the high-order sliding mode surface. Because it not only combines the advantages of fuzzy systems, but also incorporates the advantages of neural network control, the proposed double loop fuzzy neural network can better approximate the system model with excellent approximation. Moreover, it has the advantage of full adjustment, and the initial values of all parameters in the network can be arbitrarily set, then the parameters can be adjusted to the optimal stable value adaptively according to the adaptive algorithm. Finally, the superiority of the STSMC algorithm is also discussed. Simulation results verify the superiority of the STSMC algorithm, showing it can improve system performance and estimate unknown models more accurately compared with conventional neural network sliding mode control (CNNSMC).

Output Feedback Adaptive Fractional-Order Super-Twisting Sliding Mode Control of Robotic Manipulator

In this study, trajectory tracking of robotic manipulators with uncertainties and external disturbances is obtained by proposing model-free adaptive fractional super-twisting sliding mode control (AOFSTSM). The proposed AOFSTSM method is composed of an adaptive super-twisting sliding mode control integrated with fractional-order (FO) control. An adaptive tuning control is utilized to evaluate the uncertain unknown dynamics of the system without relying on the prior knowledge of the upper bounds. Moreover, FO control and super-twisting sliding mode control are used to achieve the fast finite-time convergence, chatter-free control inputs, better tracking performance and robustness. An output feedback (OF) is proposed and the state estimation is obtained by robust exact differentiator. Furthermore, the stability of the overall system is investigated and derived from the Lyapunov stability criterion. Finally, to validate the effectiveness and robustness of the developed control method, comparative simulations of state-feedback and OF of proposed method with fractional-order nonsingular fast terminal sliding mode control are realized to demonstrate the performance of AOFSTSM.

Nonlinear disturbance observer based adaptive super-twisting sliding mode control for generic hypersonic vehicles with coupled multisource disturbances

In practical, there often exist structural uncertainties, measurement errors, and the aerodynamic perturbations in the flight control systems of the hypersonic vehicles (HSVs). The control performance degradation and loss of stability may be induced if the coupled multisource uncertainties are ignored. To address this problem, this paper develops a novel multivariable robust adaptive sliding mode control structure. Benefiting from the second-order characteristics of the super-twisting controller, the uncertainties from the unknown nonlinearities and the lumped disturbances can be surmounted respectively. Meanwhile, the finite time convergence can be obtained and the continuity of the control signals can be guaranteed. Moreover, to cope with the unknown upper bounds of lumped uncertainties, a novel update law is developed by analyzing the connection between the control gains and the boundaries. Moreover, for the purpose of compensating the mismatched uncertainties in HSVs, a robust disturbance observer is introduced into the sliding surface such that the sliding-mode dynamics are stable with L2−L∞ performance. The closed-loop control system is proved to be globally ultimately stable. Simulation results indicate that the proposed control scheme works well compared with the existing methods.

Terminal sliding mode disturbance observer based adaptive super twisting sliding mode controller design for a class of nonlinear systems

In this paper, an adaptive super twisting sliding mode controller (ASTSMC) is proposed for a class of nonlinear systems to counteract mismatched uncertainties. To estimate the unknown external disturbance efficiently, an adaptive terminal sliding mode disturbance observer (ATSMDO) is proposed. The stability of the over all closed loop system is proved by Lyapunov stability theory. To validate the proposed ATSMDO based ASTSMC, a case study of a nonlinear liquid level regulation problem is considered. Both simulation and real-time results are presented to show the effectiveness of the proposed controller than the traditional adaptive sliding mode controller (ASMC) and reported controllers in literature. From the analysis, it is observed that the proposed controller alleviates the chattering problem effectively.

Fuzzy-Based Adaptive Super-Twisting Sliding-Mode Control for a Maneuverable Tethered Space Net Robot

The use of maneuverable tethered space net robot (TSNR) is a promising solution for active space debris capture and removal due to its large envelop and easy capture method. However, the flexibility and elasticity of the underactuated net present a new challenge to the control scheme. In this article, a fuzzy-based sliding-mode control is proposed and applied to the TSNR. The main contribution is that an adaptive super-twisting sliding-mode control (ASTSMC) is investigated with a novel adaption law based on a fuzzy estimator, eliminating the need for a derivative of uncertainty. The key advantage of the proposed scheme is that the passive adaption law of traditional ASTSMC is improved to an active law, and complex oscillations can be directly estimated and suppressed. The dynamics equations of the TSNR are first derived, and the control problem of the system is specified. For the unmeasurable and boundary-unknown uncertainties, the adaptive fuzzy logic scheme is employed to approximate the complex uncertainties. Stability analysis and approximation convergence of the proposed control scheme are then verified via Lyapunov stability analysis. Finally, numerical simulations on the TSNR are provided to confirm the effectiveness and robustness of the proposed scheme.

HGO-based adaptive super-twisting sliding mode power level control with prescribed performance for modular high-temperature gas-cooled reactors

This paper proposes a high-gain observer-based adaptive super-twisting sliding mode control strategy with prescribed performance (HGO-ASTSMCS-PP) for the power level of a modular high-temperature gas-cooled reactor (MHTGR). The dynamic model of the MHTGR is firstly described. By using this established model, a high-gain observer is constructed to recover the unmeasured states including relative density of delayed neutron precursor and reactor core temperature in real time. On the basis of the recovering values from the HGO, an adaptive super-twisting sliding mode control method with prescribed performance is designed. The super-twisting sliding mode control approach is adopted to improve control performance of power level for a MHTGR and suppress high-frequency chattering effects simultaneously. An adaptive mechanism is introduced to tune the control gains online so as to overcome the overestimation of the unknown disturbance boundary. In addition, by error transformation and introduction of performance function, the prescribed control performance of power level is guaranteed, which implies that the desirable convergence rate, steady power error, and maximum overshoot can be prescribed in advance. It is verified through Lyapunov stability theory that the overall closed-loop control system is globally uniformly ultimately bounded (GUUB). Finally, simulation and comparison results are presented to reveal the effectiveness of the proposed control scheme in terms of the steady and dynamic performance.

High performance super-twisting sliding mode control for a maritime autonomous surface ship (MASS) using ADP-Based adaptive gains and time delay estimation

This research addresses two kinds of problems related to optimal trajectory tracking of a Maritime Autonomous Surface Ship (MASS): those caused by the time-varying external disturbances including winds, waves and ocean currents as well as those resulting from inherent dynamical uncertainties. As the paper shows, an accurate and robust optimal controller can successfully deal with both issues. An improved Optimal Adaptive Super-Twisting Sliding Mode Control (OAST-SMC) algorithm is proposed here as a robust optimal adaptive strategy. In this strategy, in order to improve performance of the standard super-twisting approach, we apply an Approximate Dynamic Programming (ADP)-based optimal tuning of gains and an underlying concept based on Time Delay Estimation (TDE). An ADP algorithm is implemented using an actor-critic neural network to deal with the curse of dimensionality in Hamilton–Jacobi–Bellman (HJB) equation. The critical role of TDE part in this algorithm is estimating the impact of disturbances and uncertainties on the MASS model. The results have shown that OAST-TDE significantly outperforms the ST-TDE and AST-TDE algorithm in terms of the optimal control efforts. Also, compared with a Nonlinear Model Predictive Control (NMPC), proposed controller meets the optimal control efforts and accurate tracking concurrently.

Particle swarm optimization–based adaptive super-twisting sliding mode control design for 2-degree-of-freedom helicopter

This paper presents a novel design of adaptive super-twisting sliding mode controller for two-axis helicopter with model uncertainties. The high-order super-twisting sliding mode control strategy is used to guarantee that the sliding surface can reach the equilibrium point in a shorter time and to avoid the chattering problem. The adaptive control algorithm has been developed based on Lyapunov theory to estimate the unknown parameters of 2-degree-of-freedom helicopter such that the global stability of the controlled system based on adaptive super-twisting sliding mode is guaranteed. A comparison study between conventional and adaptive super-twisting sliding mode controllers is made and the effectiveness of the proposed scheme is verified via computer simulation.

Impulsive Super-Twisting Sliding Mode Control for Space Debris Capturing via Tethered Space Net Robot

Tethered space net robot (TSNR) has been proposed as a promising method for active space debris capturing and removal since space debris have posed a big threat to operational satellites and astronauts. After contacting the debris, the net cannot naturally wrap around the debris, especially when the debris does not contact the net in the center. Thus, it is worth investigating the net closing control of TSNR. Two requirements should be satisfied in the net closing control algorithm. First, the control algorithm should make the net close around the debris in a very short time to avoid the escape of the debris. Second, the control input should be continuous to avoid the oscillations of net tether caused by high-frequency control instructions. In this article, based on the two requirements, an impulsive adaptive super-twisting sliding mode control scheme is proposed to complete the net closing action. The control scheme can drive the state vectors convergence to the origin in a short time and keep it there thereafter. The numerical simulation results illustrate the efficiency of the proposed control algorithm, in which the two requirements are all satisfied.

Adaptive super-twisting sliding mode control for stabilization platform of laser seeker based on extended state observer

In this paper, the stabilization platform of the seeker is analyzed to stabilize the photo-electric device by isolating the disturbances caused by vibration and turbulence from external conditions, as well as mechanical coupled torque, coiling, unbalanced torque and plant parameter uncertainty due to inner conditions. There are two important indexes to describe the performance of disturbance isolation, and these are the coupling coefficient and disturbance rejection rate. In order to improve the disturbance isolation performance of the stabilization platform of the seeker, an adaptive super-twisting sliding mode controller with an extended state observer is proposed. The adaptive super-twisting sliding mode control strategy is designed to achieve stabilized control of the stabilization platform of the seeker. The extended state observer is used to estimate and compensate for disturbances and model uncertainties. The stability analysis of the control strategy is discussed using Lyapunov stability theory. Simulation and experimental results are also presented to illustrate the effectiveness of the proposed control strategy. The proposed controller provides a better level of disturbance rejection compared to the conventional PI-DOB controller.

Adaptive super-twisting sliding mode control of variable sweep morphing aircraft

In this paper, a novel and more explicit longitudinal model of a wing-sweep morphing aircraft is proposed, accounting for the variations in aerodynamics, mass and inertial properties. In addition, open loop dynamic responses with different morphing rates are simulated, and a small morphing rate leads to big magnitudes of velocity and altitude variations. During morphing process, both aerodynamic parameters and mass distribution change dramatically, and it causes a difficulty in modeling the morphing aircraft precisely. Therefore, an adaptive super twisting algorithm sliding mode controller is proposed to track reference trajectory after input/output linearization of the longitudinal model. Simulation results show the designed controller works better with good tracking performance and smaller chattering compared with normal sliding mode controller, and the robustness of the designed controller is verified by simulations at the presence of aerodynamic perturbations.

Adaptive robustSMC of hybrid robot for automobile electro‐coating conveying

For a novel hybrid robot for automobile electro-coating conveying, an adaptive robust sliding-mode controller is proposed to improve the control performances and counteract the influences of uncertainties including modelling error, friction, and external disturbance. One remarkable feature of the controller lies in that it does not require the boundary of the uncertainties in the hybrid robot by designing a novel gain adaptation law. The law is capable of dynamically adjusting control gains to avoid selecting excessively bigger values of the control gains, and further attenuating the chattering phenomenon of the super-twisting sliding-mode control (SMC) simultaneously. Moreover, disturbance observer is used to estimate and compensate various uncertainties to further improve the robustness of the control system. The stability of the designed control algorithm is proved by Lyapunov stability theorem. The simulation and experimental results show that the adaptive robust SMC has superior tracking performance and is able to attenuate the chattering phenomenon effectively in the presence of modelling error, frictions, and external disturbances.

Nested adaptive super-twisting sliding mode control design for a vehicle steer-by-wire system

Abstract This paper presents a nested adaptive super-twisting sliding mode (NASTSM) control scheme for a vehicle Steer-by-Wire (SbW) system. Firstly, the plant model of the SbW system is expressed as a second-order differential equation from the steering motor input voltage to the front wheel steering angle. Specifically, the model of the self-aligning torque is elaborated in detail and compared with a simplified one. Next, an NASTSM controller is designed for the SbW system, which adopts a nested adaptive law to promote tracking accuracy by dealing with complex time-varying external disturbances and a super-twisting sliding mode (STSM) control component to guarantee strong robustness while alleviating chattering phenomenon. The stability of the NASTSM control system is verified in the sense of Lyapunov. Finally, experiments are carried out under various conditions. The experimental results show that the proposed NASTSM controller owns superiority in terms of not only higher tracking precision and stronger robustness, but also less dependence on the information of plant models compared with a conventional adaptive sliding mode (CASM) controller.

Adaptive super-twisting sliding mode control of 6-DOF nonlinear and uncertain air vehicle

In this paper, to control the six degree-of-freedom non-linear unmanned aerial vehicle, two strategies are implemented using adaptive super-twisting sliding mode control approach. The first one is a single-channel controller that is designed on the basis of decoupled equations of motion. The other one is a three-channel controller that is designed based on the coupling equations of motion along with an adaptive super-twisting observer. The stability of the closed loop system of the controller-observer is proven. The comparison between the single-channel controller and the three-channel could lead us to select between a little lower efficiency and less complexity versus efficiency and more complexity. To examine the performance and robustness of these two control loops, their performances are analyzed in the presence of combined uncertainties, including aerodynamics, mass, inertial moment, sensor, and actuator disturbances and parametric uncertainties in the stage separation phase. The explosive bolt separation mechanism is assumed to perform the stage separation, and its forces, moments and disturbances are modeled as needed. Finally, the responses are compared with the classic PID controller.

Stability control of a flexible maneuverable tethered space net robot

As a promising solution for active space debris capture and removal, a maneuverable Tethered Space Net Robot (TSNR) is proposed as an improved Space Tethered Net (TSN). In addition to the advantages inherit to the TSN, the TSNR's maneuverability expands the capture's potential. However, oscillations caused by the TSNR's flexibility and elasticity of make higher requests of the control scheme. Based on the dynamics model, a modified adaptive super-twisting sliding mode control scheme is proposed in this paper for TSNR stability control. The proposed continuous control force can effectively suppress oscillations. Theoretical verification and numerical simulations demonstrate that the desired trajectory can be tracked steadily and efficiently by employing the proposed control scheme.

Design and analysis of adaptive Super-Twisting sliding mode control for a microgyroscope.

This paper proposes a novel adaptive Super-Twisting sliding mode control for a microgyroscope under unknown model uncertainties and external disturbances. In order to improve the convergence rate of reaching the sliding surface and the accuracy of regulating and trajectory tracking, a high order Super-Twisting sliding mode control strategy is employed, which not only can combine the advantages of the traditional sliding mode control with the Super-Twisting sliding mode control, but also guarantee that the designed control system can reach the sliding surface and equilibrium point in a shorter finite time from any initial state and avoid chattering problems. In consideration of unknown parameters of micro gyroscope system, an adaptive algorithm based on Lyapunov stability theory is designed to estimate the unknown parameters and angular velocity of microgyroscope. Finally, the effectiveness of the proposed scheme is demonstrated by simulation results. The comparative study between adaptive Super-Twisting sliding mode control and conventional sliding mode control demonstrate the superiority of the proposed method.