Attitude Tracking Control Problem Research Articles

Adaptive Iterative Learning Tracking Control for Nonlinear Teleoperators with Input Saturation

Addressing input saturation, external disturbances, and uncertain system parameters, this paper investigates the position tracking control problem for bilateral teleoperation systems with a time delay communication channel. Based on a composite energy function, we propose an adaptive iterative learning control (AILC) method to achieve the objective of position tracking under the alignment condition. This extends the existing research on the control of nonlinear teleoperation systems with time delay. The saturation constraint property of the Softsign function ensures that no state of the system exceeds its constraints. The controller learns to simultaneously deal with the uncertainty of system parameters online, reject external disturbances, and eliminate positional errors along the time and iteration axes. All signals in the system for any constant time delay are proved to be bounded. Ultimately, the performance of the proposed controller is further verified through numerical simulations.

Active underactuation fault‐tolerant backstepping attitude tracking control of a satellite with interval error constraints

AbstractUnderactuation poses a significant challenge to space mission control and performance. This article investigates the non‐linear attitude tracking control problem for a remote sensing satellite underactuated by a reaction wheel (RW) actuator fault. First, a timeline close to the in‐orbit reality of an underactuation fault is presented. Then, the fault detection and diagnosis strategy is performed in a finite‐time decision window. The failed actuator is excluded from the control loop by forming the proposed reconfiguration window to transition from a 3 RWs configuration to 2 RWs. The underactuation fault‐tolerant control is designed according to the active method, where the adaptive robust control law employed for fault‐free conditions is switched to the underactuated attitude tracking control (UATC). The structure of UATC is based on kinematic and adaptive backstepping dynamic controllers. The effect of unknown bounded external disturbances is considered with an adaptive estimation term. The asymptotic stability of the closed‐loop control system is proved via Lyapunov theory in the presence of parametric uncertainty. Due to the underactuation, a new approach proposed in the prescribed performance function is interval error constraints, which include the pointing accuracy and stability requirements in imaging time intervals. Finally, the results of the multidisciplinary simulation and experimental test confirm the applicability of the underactuation fault‐tolerant control.

Robust fixed-time flight controller for a dual-system convertible UAV in the cruise mode

This paper investigates the attitude tracking control problem for the cruise mode of a dual-system convertible unmanned aerial vehicle (UAV) in the presence of parameter uncertainties, unmodeled uncertainties and wind disturbances. First, a fixed-time disturbance observer (FXDO) based on the bi-limit homogeneity theory is designed to estimate the lumped disturbance of the convertible UAV model. Then, a fixed-time integral sliding mode control (FXISMC) is combined with the FXDO to achieve strong robustness and chattering reduction. Bi-limit homogeneity theory and Lyapunov theory are applied to provide detailed proof of the fixed-time stability. Finally, numerical simulation experimental results verify the robustness of the proposed algorithm to model parameter uncertainties and wind disturbances. In addition, the proposed algorithm is deployed in a open-source UAV autopilot and its effectiveness is further demonstrated by hardware-in-the-loop experimental results.

Flexible performance‐based adaptive fault‐tolerant attitude tracking control for input‐constrained satellite

SummaryUnder the actuator saturation and fault, the satellite attitude often violates the prescribed performance function, leading to the satellite attitude's instability. Therefore, the adaptive attitude tracking control problem for the satellite simultaneously considering the finite time‐based prescribed performance, the actuator saturation and the actuator fault is studied in this article. A modification performance function‐based control scheme is designed, which can avoid violating the designed modified performance functions when the actuator saturation occurs due to the actuator fault. A novel fault tolerant auxiliary system is developed, which is used to generate modification signals for adjusting the prescribed performance function. Consequently, the boundedness of all the closed‐loop signal under the designed control scheme is proved via Lyapunov function method. Finally, the feasibility of the designed satellite attitude control scheme is verified by a simulation example.

Output feedback attitude control of flexible spacecraft under actuator misalignment and input nonlinearities

The attitude tracking control problem of flexible spacecraft subjected to parameter uncertainties, time-dependent external disturbances, actuator input nonlinearity, and input actuator misalignment is investigated in this paper. Explicitly, the proposed strategy addresses the input actuator misalignment and dead-zone issues that increase the controller design difficulties. Initially, a new second-order sliding mode observer (SoSMO) using an extended state approach is developed by adding a correction function to improve observer performance to estimate unwanted system perturbations. Then, a distinct SoSMO-based integral-type sliding mode control (ISMC) structure is designed in a unified manner to guarantee the asymptotic stability of the closed-loop system. Comparative numerical simulations under input actuator misalignment, the dead-zone nonlinearity, external disturbance, and inertia uncertainty are performed to illustrate the effectiveness of the proposed controller.

Designing an adaptive robust observer for underactuation fault diagnosis of a remote sensing satellite

SummaryThis paper mainly aims at the underactuated case diagnosis due to an actuator failure for a remote sensing satellite. We consider healthy initial conditions for the actuators to investigate the underactuation fault in an attitude tracking control problem. Reaction wheels are the onboard actuators, and a new fault injection mechanism on the speed characteristic is introduced using the multi‐fault function. The fault detection and diagnosis strategy is based on the sliding mode and adaptive sliding mode observers in a finite‐time decision window. The robust observer and adaptive threshold are designed to detect the fault, and the adaptive robust observer estimates the fault model. The residual signal is evaluated by forming the window with fixed thresholds, and in the decision steps, priority is given to the underactuation fault diagnosis. System performance is presented for two actuator fault scenarios in a snapshot imaging mode to understand this case clearly. Numerical simulations close to in‐orbit conditions confirm the satisfactory performance of the proposed strategy that underactuated case is diagnosed by injecting stuck and idle faults around 2.19 and 3.52 s. The times obtained in this study are guaranteed with a 3‐sigma confidence level statistical characteristic. Furthermore, the results of the present work are validated using an air‐bearing experimental test bed to illustrate a more realistic behavior of an underactuated satellite.

Adaptive Fuzzy Predefined-Time Dynamic Surface Control for Attitude Tracking of Spacecraft With State Constraints

This study focuses on the adaptive fuzzy predefined-time attitude tracking control problem for rigid spacecraft with inertia uncertainties, external disturbances, and state constraints. In control design, fuzzy logic systems (FLSs) are adopted to approximate the unknown nonlinear dynamics, and a quadratic-fraction barrier Lyapunov function (QFBLF) is introduced to ensure that the predefined state constraints are not violated. Compared with the existing dynamic surface control (DSC) approaches, a novel predefined-time filter and an adaptive fuzzy predefined-time controller are presented, such that the filter error and attitude tracking error can converge to a small region in predefined time simultaneously, where the minimum upper bound of settling time can be exactly preset by tuning one control parameter. Comparative simulation results are carried out to verify the superiority and efficacy of the presented strategy.

Attitude Tracking Adaptive Control of a Geocentric Polar Displaced Solar Sail

To deal with the attitude tracking control problem of a struck or pierced geocentric polar displaced solar sail (GPDSS), an attitude adaptive control strategy is proposed in this paper under the complex conditions of unknown inertial parameters, external disturbance and input saturation. First, on the basis of a flexible solar sail spacecraft attitude dynamics model with damping terms and vibration initial values, an integrated disturbance term, including inertial parameter uncertainties and external disturbance, is constructed. Second, a radial basis function neural network is applied to design a disturbance estimator with an adaptive law to estimate the integrated disturbance in real time. Then, a sliding-mode controller with fixed-time convergence in the reach phase and finite-time stability in the sliding phase is designed, and stability analysis is conducted by using the Lyapunov theory. Finally, comparative simulations with a linear sliding-mode controller and numerical simulations under various workings are performed. The results show that the designed adaptive control strategy can effectively achieve the attitude tracking control of the GPDSS.

Barrier function-based prescribed-performance adaptive attitude tracking control for spacecraft with uncertainties

This paper addresses the problem of robust adaptive attitude tracking control for spacecraft with mismatched and matched uncertainties. The idea of disturbance estimation and compensation is introduced into the control design. First, finite-time disturbance observers are developed for different channels of spacecraft based on barrier functions for achieving finite-time asymptotic estimates of unknown bounded uncertainties in the system. Second, a class of prescribed performance functions is considered in the design of the barrier function. The spacecraft attitude adaptive tracking control strategy with finite-time convergence capability and prescribed performance is proposed based on the designed finite-time disturbance observers and barrier function. Finally, the theoretical findings are verified by numerical simulations and compared with the simulation results of existing methods.

OPTIMAL TRACKING CONTROL FOR ROBOT MANIPULATORS WITH INPUT CONSTRAINT BASED REINFORCEMENT LEARNING

This paper introduces an optimal tracking controller for robot manipulators with saturation torques. The robot model is presented as a strict-feedback nonlinear system. Firstly, the position tracking control problem is transformed into the optimal tracking control problem. Subsequently, the saturated optimal control law is designed. The optimal control law is determined through the solution of the Hamilton-Jacobi-Bellman (HJB) equation. We use a reinforcement learning algorithm with only one neural network (NN) to approximate the solution of the equation HJB. The technique of experience replay is used to relax a persistent citation condition. By Lyapunov analysis, the tracking and the approximation errors are uniformly ultimately bounded (UUB). Finally, the simulation on a robot manipulator with saturation torques is performed to verify the efficiency of the proposed controller.

Fault-Tolerant Attitude Control for Hypersonic Flight Vehicle Subject to Actuators Constraint: A Model Predictive Static Programming Approach

In this article, an improved model predictive static programming (MPSP) based fault-tolerant control (FTC) scheme is proposed to solve the attitude tracking control problem of the hypersonic vehicle (HSV). In the field of HSV, the MPSP technique has been applied successfully to solve guidance problems for its high computational efficiency. While we try to address the attitude control problem directly using it. The attitude model of HSV with uncertainty and disturbance, together with the fault model of aircraft body injury, are constructed firstly. The actuator of HSV is suffering from input constraints. Then, a feasible attitude control trajectory is generated by the improved MPSP method. The methodological innovation in this paper extends MPSP technique to the direct control of the attitude of HSV both in fixed and flexible final time. By utilizing the improved MPSP technique, the complexity of processing multiple constraints and the computation are reduced. The effectiveness of the designed FTC scheme is demonstrated through simulation under different cases with actuator constraints.

Attitude tracking backstepping control for small unmanned helicopters based on adaptive neural network under unknown environment disturbances

To solve the attitude tracking control problem of small unmanned helicopters under unknown bounded disturbances, an attitude tracking backstepping controller based on adaptive radial basis function (RBF) neural network disturbance compensation is proposed in this paper. The unknown disturbance is estimated online and in real time through RBF neural network with a novel gradient descent weight update rate. A novel attitude tracking backstepping controller based on virtual control variables is designed, and the system stability is analyzed using the Lyapunov method. The experimental verification of the backstepping controller is carried out on the three-degrees-of-freedom helicopter. The experiments show the effectiveness and advancedness of the proposed adaptive neural network backstepping controller in suppressing unknown external disturbances compared with the robust adaptive integral backstepping.

Minimum eigenvalue based adaptive fault compensation for hypersonic vehicles

The attitude tracking control problem is addressed for hypersonic vehicles under actuator faults that may cause an uncertain time-varying control gain matrix. An adaptive compensation scheme is developed to ensure system stability and asymptotic tracking properties, including a kinematic control signal and a dynamic control signal. To deal with the uncertainties of the control gain matrix, a new positive definite one is constructed. The minimum eigenvalue of such a new control gain matrix is estimated. Simulation results of application to an X-33 vehicle model verify the effectiveness of the proposed minimum eigenvalue based adaptive fault compensation scheme.

Velocity‐free adaptive nonsingular fast terminal sliding mode finite‐time attitude tracking control for spacecraft

AbstractAiming at the attitude tracking control problem of rigid spacecraft under the condition of unmeasurable angular velocity information, a velocity‐free adaptive nonsingular fast terminal sliding mode finite‐time tracking control method is proposed. The finite‐time extended‐state observer is used to estimate the attitude tracking speed errors and the integrated disturbances. Combined with the above control method, a fast nonsingular terminal sliding mode controller with attitude measurement is designed and the adaptive technology is introduced to compensate for the influence of observation errors on the controller. The finite‐time convergence of the observer and the control method was demonstrated based on Lyapunov theory, and the effectiveness of the proposed method is verified by numerical simulations.

Filtering‐based concurrent learning adaptive attitude tracking control of rigid spacecraft with inertia parameter identification

SummaryThis paper investigates the attitude tracking control problem of rigid spacecraft with inertia parameter identification. Based on the relative attitude and angular velocity error dynamics, a basic adaptive backstepping based attitude tracking control scheme is firstly designed such that asymptotic attitude tracking can be achieved. However, the parameter identification error cannot decay to zero if the persistent excitation (PE) condition is not satisfied. To solve this issue, a filtering‐based concurrent learning adaptive backstepping control scheme is then proposed, by incorporating torque filtering technique with concurrent learning technique. A more mild rank condition, which consists of some collectable historical data, is provided to guarantee the convergence of parameter identification error. In addition, a valid data collection algorithm is given. It should be mentioned that a distinctive feature of the proposed filtering‐based concurrent learning adaptive control scheme is that the convergence rate of attitude tracking errors can be improved from asymptotical to exponential. Finally, simulation results are provided to illustrate the effectiveness of the proposed control schemes.

Adaptive fuzzy gain‐varying finite‐time command filtered backstepping control for permanent magnet synchronous motors with mismatched disturbances

SummaryThis article investigates the position tracking control problem of permanent magnet synchronous motors (PMSMs) with mismatched disturbances based on adaptive fuzzy gain‐varying finite‐time command filtered backstepping method. First, the anti‐disturbance ability of the system is improved by constructing gain‐varying functions instead of the traditional static gains. Then, the command filter is adopted to overcome the explosion of complexity in classical backstepping method, and the gain‐varying error compensation mechanisms are introduced to reduce the errors produced by command filters. In addition, the finite‐time control technique makes the tracking error converges to a small neighborhood of origin in finite time. The fuzzy logic systems (FLSs) are used to approximate the nonlinear functions with strong coupling of PMSMs systems, and this article further utilizes the characteristics of FLSs to separate the states and handle the coupling of PMSMs systems. Finally, the simulation results prove the validity of the proposed strategy.

Fast fixed‐time attitude tracking control of spacecraft with prescribed performance

AbstractThe attitude tracking control problem of rigid spacecraft subjected to external disturbance and prescribed performance is studied. A fast fixed‐time stability theorem is firstly developed. A continuous disturbance observer is then designed with its estimation error can be driven into a tiny neighborhood containing zero within fixed time. Moreover, the spacecraft attitude tracking error constrained by prescribed performance function is transformed into an unconstrained dynamics. A disturbance observer‐based prescribed performance tracking controller is designed to stabilize the unconstrained dynamics within fixed time. It also means that the attitude tracking errors meet the prescribed performance as the stabilization of the unconstrained dynamics. Spacecraft simulation examples are finally given to validate the effectiveness of the proposed controller.

Position tracking of an autonomous underwater glider based on adaptive filtered backstepping control

This paper considers the problem of position tracking control of the autonomous underwater gliders, which operates under the environment of model uncertainties and external disturbances. The motion of the glider is controlled by ballast mass and moving mass, which have limited dynamic range. An adaptive control system for position tracking based on filtered backstepping is proposed, and neural networks and sliding mode control are used to improve robustness. Next, using Lyapunov stability theory, it is proved that all the signals are bounded and tracking errors eventually converge to a neighborhood of zero. The presented controller can be easily put into practice without the requirement to know the parameters of the glider and the value of external environmental disturbances. Finally, the effectiveness and good robustness of the proposed control system are verified by simulation results.

Underactuated attitude tracking control of tethered spacecraft for deployment and spin-up

This paper investigates the underactuated attitude tracking control problem of tethered spacecraft during tether deploying and spinning. The attitudes are controlled by the torque inputs along two body axes and perturbed by the tether tension torque. The coupling effect between spacecraft attitudes and flexible tethers can be alleviated by simplifying control inputs. The main contribution is the development of an underactuated tracking controller with an adaptive barrier function that inhibits unknown disturbance. To avoid singularity problems with tether and spacecraft during simulation, the dynamic model of a tethered system is derived using quaternion transformations. The underactuated attitude control strategy is designed by kinematic state coupling relations and dynamic backstepping technique, which is given extensive stability demonstration using Lyapunov’s theory. An adaptive controller gain with barrier function is employed to inhibit the bounded unknown disturbance with no need for the online estimation signal. Finally, numerical simulations demonstrate the effectiveness and robustness of the proposed underactuated strategy in the case of tether deployment and spin-up, respectively.

On adaptive attitude tracking control of spacecraft: A reinforcement learning based gain tuning way with guaranteed performance

This paper investigates the attitude tracking control problem of a rigid spacecraft subject to inertial uncertainties, uncertain space perturbations and actuator saturation. Firstly, a static inertial-matrix free attitude controller is designed to guarantee the appointed-time convergence and tracking accuracy indicators of the spacecraft. Then, two-layer critic-action NNs are used to tune and optimize the control gains adaptively to improve the robustness and tracking performance of the devised static attitude controller via exploring the reinforcement learning (RL) technique. Compared with the existing attitude control methods, the prominent advantage of our work is that the devised controller is inertial-matrix free with a simple RL-based adaptive parameter tuning scheme, which reduces the conservativeness of the traditional attitude controllers with fixed control gains and is also easy to be achieved. Finally, two groups of illustrative examples are organized to validate the effectiveness of the proposed attitude control method.