Adaptive finite time control for spacecraft attitude maneuver based on second-order terminal sliding mode

SummaryAn adaptive fast nonsingular integral terminal sliding mode control scheme is proposed for the distributed formation control problem of multiple unmanned aerial vehicles (UAVs) affected by actuator faults and external disturbances. In order to achieve a good cooperative tracking performance of UAVs during mission execution, the adverse effect of the lumped disturbances composed of actuator failures, wind and vortex disturbances is estimated by the cerebellar model articulation neural network, meanwhile the tangent function is introduced to eliminate the chattering of the sliding mode. Then the analysis of superior convergence performance of the fast nonsingular integral terminal sliding manifold is implemented, and the finite time stability of the closed‐loop formation flight control system is proved. Finally, the simulation experiments verify that the proposed approach is superior to the nonsingular integral terminal sliding mode control for the formation control system of faulty multiple UAVs.

SummaryThis paper deals with the robust finite time tracking of desired trajectories for a wide group of robotic manipulators in spite of unknown disturbances, uncertainties, and saturations of actuators while only manipulator's positions are available and its velocities are not measurable physically. A new form of chattering‐free second order fast nonsingular terminal sliding mode control scheme is introduced to design input torques for fulfilling the determined tracking objective in the adjustable total finite settling time. The proposed control algorithm is incorporated with two nonlinear observers to estimate disturbances and velocities of joints within finite settling times. The global finite time stability of the closed‐loop manipulator is analytically proved. Finally, a numerical simulation is carried out to verify the effectiveness of the designed input torques. Copyright © 2017 John Wiley & Sons, Ltd.

In this paper, the attitude control of rigid-liquid-flexible multi-body coupling spacecraft with unknown external disturbances and uncertain inertia parameters is studied, and an attitude maneuver control method based on disturbance observer and fuzzy terminal sliding mode control is proposed. The sloshing of liquid fuel in the spacecraft is equivalent to a spherical pendulum model, and the flexible appendages are assumed to be an Euler-Bernoulli beam. The coupled dynamic equation of the liquid-filled flexible spacecraft is derived by using the Lagrange method. First of all, the interference from space, the parameter uncertainty of the moment of inertia of the spacecraft, the coupling interference caused by the liquid sloshing and the vibration of flexible accessories are summed up as lumped interference. Design disturbance observer to compensate and estimate the lumped disturbance of the system. Then, based on the designed disturbance observer, a fuzzy terminal sliding mode control law is presented, and it is proved that the state of the closed-loop system is finite-time stable under the control law, and converges to the specified terminal sliding mode surface. The fuzzy terminal sliding mode control law uses fuzzy control to improve the switching gain based on the traditional terminal sliding mode control to achieve the purpose of suppressing system jitter. This optimization method can not only reduce the complexity of terminal sliding mode control method, but also reduce the difficulty of debugging parameters because it does not introduce new functions. The numerical simulation results show that the designed fuzzy terminal sliding mode control law can not only achieve the finite-time stability of the closed-loop attitude control system of the liquid-filled flexible spacecraft, but also effectively suppress the liquid sloshing and the vibration of the flexible appendages. At the same time, it has good robustness to disturbances caused by external disturbances and parameter uncertainties, and has better control performance.

Terminal sliding mode control for coordinated motion of a space rigid manipulator with external disturbance

This paper introduces a variable structure to regulate speed of PMSM system by a global fast terminal sliding mode control (GFTSMC) technique optimizing speed tracking performance of permanent magnet synchronous motor (PMSM) servo system. Firstly, a global fast terminal sliding mode control strategy is introduced. Compared with common sliding mode control strategy, this strategy eliminates the chattering phenomenon in that it does not contain switching terms. Also, it can make the output speed reach the reference value in finite time, along with a shorter convergence time and a better tracking precision. Due to the complexity of control equations, S-function in MATLAB is adopted to design the GFTSMC. The effectiveness and robustness of the proposed scheme are verified by MATLAB simulations.

Adaptive finite-time sliding mode control design for finite-time fault-tolerant trajectory tracking of marine vehicles with input saturation

This study proposes a finite-time tracking control system for an unmanned aerial vehicle (UAV) in the presence of dynamic payloads and external disturbances. Changes in payload result in time-varying parametric uncertainties, making traditional control strategies ineffective. A sliding mode control (SMC) scheme is designed to handle uncertainties in both translational and rotational dynamics. A finite-time SMC (FTSMC) approach is developed to handle unknown time-varying mass and external disturbances in the translational dynamics. Furthermore, differences in the payload influence the inertia characteristics of the UAV, introducing further uncertainties in the feedback control design. A finite-time sliding mode controller is also implemented for rotational dynamics to guarantee the attitude stabilization under unknown inertia parameter variations. The proposed method has the objective to attenuate the chattering effect associated with traditional SMC within a finite time frame. Theoretical stability analysis with rigorous mathematical proofs is presented to confirm the effectiveness of the control scheme. Numerical simulations are provided to validate its performance under dynamic operating conditions.

A manipulator often cannot converge rapidly within finite time and has low tracking accuracy owing to factors such as manipulator model errors and external disturbances. To address these problems, this paper proposes a time-varying non-singular fast terminal sliding mode control scheme based on an improved variable power–power reaching law. First, three radial basis function neural networks (RBFNNs) are employed to approximate the dynamic parameters of the manipulator model and thus realize model-free control. Second, to achieve faster finite-time convergence of the system state, a time-varying non-singular fast terminal sliding-mode (NFTSM) surface is designed according to the system state change. In addition, an improved variable power–power reaching law is adopted to avoid chatter and eliminate approximation errors. Finally, comparative simulation experiments are conducted using a 2-DOF manipulator as the research object. The results show that the proposed control scheme facilitates fast convergence, high-precision trajectory tracking, and effective suppression of system chatter under complex uncertainties, thereby confirming its utility and superiority.

ABSTRACTTo enhance the power quality of microgrid inverters and reduce the influence of changes in inductance parameters and external disturbances on the direct power control of the inverter system, a terminal sliding mode control strategy with a variable exponential power reaching law has been proposed. The designed new reaching law comprises a variable exponential term and an enhanced power term. The variable exponential term contains an arctangent function, and the power term coefficient is replaced by a function about the sliding mode. Therefore, the convergence rate can be adaptively adjusted based on different stages of the system, ensuring a faster rate of convergence throughout the process of approaching the sliding mode surface. To weaken the effects of changes in inductance parameters, a power disturbance observer is designed to estimate the internal disturbances induced by the filtered inductance in the system. Subsequently, a sliding mode control law containing disturbance observations is derived. Moreover, a variable exponential terminal sliding surface is designed to adjust the convergence rate of system errors on the sliding surface in stages, thereby enhancing the control performance of the system. The simulation results show that the new reaching law has faster convergence rate and better dynamic performance. The convergence speed of the system error can be accelerated by the designed variable exponential terminal sliding surface. The sliding mode control strategy with the variable exponential power reaching law is applicable to the power control system of three‐phase inverters in microgrids, thereby significantly enhancing the dynamic performance and robustness of the system.

In this paper, the attitude control problem for uncertain spacecraft under angular velocity constraint is addressed. Both parametric uncertainty and external disturbance are considered in the spacecraft's dynamics. The spacecraft's attitude is represented by modified Rodrigues parameter (MRP) for its non-redundancy. A time-varying sliding mode control (TVSMC) algorithm is derived for attitude control system. The proposed control algorithm eliminates the reaching phase of the conventional time-invariant sliding mode control (SMC) and guarantees the sliding mode occurrence all the time. Moreover, the control parameter is adjusted to avoid the angular velocity constraint during the maneuver. Finally, a numerical simulation is employed to verify the proposed control algorithm.

A robust finite time sliding mode control strategy is proposed in this paper for a flexible air-breathing hypersonic vehicle (FAHV) model with aerodynamic parameter uncertainty. The strong coupling among the aerodynamics, the propulsion system and the flexibility effects makes the problem more challenging. Firstly, to reduce the complexity of the controller design, the FAHV model is transformed into three subsystems (velocity subsystem, altitude and flight path angle subsystem, attack of angle and pitch rate subsystem). Secondly, based on super-twisting algorithm, a novel finite time disturbance observer and an improved sliding mode controller are designed to ensure the finite time stability of each subsystem. The proposed disturbance observer can estimate the uncertainty and the derivative of virtual control in finite time. Finally, simulation results are presented to show the precision and rapidness in tracking the reference trajectory and validate the effectiveness of the designed controller.

The paper propose a novel method for designing fault tolerant controller based on adaptive fast terminal sliding mode control to address the tracking control problem of spacecraft with unknown external disturbances and an uncertain inertia matrix. In this approach, a robust controller based on fast terminal sliding mode control scheme is designed in the absence of fault detection and diagnosis through adaptive approach which applied to estimate the fault minimum value of actuator fault. Through this approach, the closed-loop system globally asymptotically stability and fault tolerant control is achieved in the finite time while the disturbance is suppressed when actuaors fault occurred. Numerical simulations have demonstrated that the proposed approach could force the system to the equilibrium points in a fast convergence rate while improve the robustness and reliability with respect to common sliding mode method.

Agile rest-to-rest attitude maneuvering of spacecraft using pyramid-type SGCMG based on iteratively recalculated optimal trajectory

This article tackles the finite‐time global trajectory tracking control problem of the autonomous underwater vehicle (AUV) in presence of input saturation constraints, actuator faults, unknown dynamics, and external disturbances. First, we describe the orientation of the AUV by rotation matrix instead of classical Euler angle or unit quaternion such that the AUV's dynamics could be globally formulated without singularity and unwinding phenomenon. After that, a smooth dead zone‐based model is introduced here to linearize the actuator model, leaving that the adaptive laws could be suitable for the solution of input saturation and actuator faults. Considering that the difficulty of model dynamic acquirement, together with the complicity of rotation‐matrix‐based representation, would trouble deployment of the controller. The minimum learning parameter technology is thereby utilized to approximated the dynamic nonlinearity of the AUV. On the basis of these, a rotation‐matrix‐based sliding mode control scheme is technically proposed. It is proved that the tracking errors can be stabilized to a small neighborhood of origin within a settling time. Finally, several set numerical experiments are conducted to assess the effectiveness and show the advantages of the proposed control scheme.

An integral TSMC-based adaptive fault-tolerant control for quadrotor with external disturbances and parametric uncertainties