High-precision Trajectory Tracking Control Research Articles

USV Trajectory Tracking Control Based on Receding Horizon Reinforcement Learning.

We present a novel approach for achieving high-precision trajectory tracking control in an unmanned surface vehicle (USV) through utilization of receding horizon reinforcement learning (RHRL). The control architecture for the USV involves a composite of feedforward and feedback components. The feedforward control component is derived directly from the curvature of the reference path and the dynamic model. Feedback control is acquired through application of the RHRL algorithm, effectively addressing the problem of achieving optimal tracking control. The methodology introduced in this paper synergizes with the rolling time domain optimization mechanism, converting the perpetual time domain optimal control predicament into a succession of finite time domain control problems amenable to resolution. In contrast to Lyapunov model predictive control (LMPC) and sliding mode control (SMC), our proposed method employs the RHRL controller, which yields an explicit state feedback control law. This characteristic endows the controller with the dual capabilities of direct offline and online learning deployment. Within each prediction time domain, we employ a time-independent executive-evaluator network structure to glean insights into the optimal value function and control strategy. Furthermore, we substantiate the convergence of the RHRL algorithm in each prediction time domain through rigorous theoretical proof, with concurrent analysis to verify the stability of the closed-loop system. To conclude, USV trajectory control tests are carried out within a simulated environment.

High-Precision Trajectory Tracking Control for Free-Flying Space Manipulators With Multiple Constraints and System Uncertainties

High-Precision Trajectory Tracking Control for Free-Flying Space Manipulators With Multiple Constraints and System Uncertainties

Active Disturbance Rejection Control Algorithm for the Driven Branch Chain of a Polishing Robot

To overcome poor error suppression performance and low control accuracy in the polishing robot-driven branch chain control system, this paper proposes an improved active disturbance rejection control (ADRC) from the design of the derived nonlinear function. Subsequently, the tracking differentiator (TD), extended state observer (ESO) and nonlinear state error feedback (SEF) are designed in the ADRC, and the driven branch’s ADRC servo-control system is established based on the permanent magnet synchronous motor (PMSM) with each driven branch. Meantime, by establishing first-order and second-order ADRC, current-loop control, and speed-and-position-loop control are realized, respectively. Finally, this study analysed differences in the speed and motor rotor error performance between the proportional-integral-derivative (PID)control and ADRC control strategy by using Simulink. Furthermore, an experiment platform, including hardware and software, is built to validate some inclusions. The results show that the ADRC not only realises high-precision trajectory tracking control but also ensures the rapid response performance of the system.

Identification and high-precision trajectory tracking control for space robotic manipulator

In this paper, an effective control and parameters identification scheme was proposed for high-precision trajectory tracking of space robotic manipulators. Our proposed control method employed a linear-extended-state-observer (LESO) based model predictive control (MPC) scheme. The feedback linearization approach was utilized to develop a model predictive controller. The optimization objective function was simplified to a standard quadratic programming (QP) problem for solution. To minimize the impact of the inaccuracy in the dynamics model, a LESO was designed to estimate the disturbance, and its convergence was demonstrated. In order to improve the accuracy of dynamic model, the physical consistency of inertial parameters was constrained using linear matrix inequality (LMI) techniques. Moreover, the dynamics parameters were estimated through semidefinite programming (SDP) techniques. To validate the effectiveness of the proposed control method, it was compared with existing controllers through simulations and experiments. The results demonstrated the superior performance of the proposed scheme, highlighting its potential for achieving high-precision trajectory tracking control in space robotic manipulators.

Trajectory tracking control for a cable-driven space manipulator using time-delay estimation and nonsingular terminal sliding mode

Trajectory tracking control is critical for cable-driven manipulators to achieve long-distance operation. However, the uncertainties and deformations caused by long-distance transmission cables make the existing trajectory tracking control methods for cable-driven space manipulators unable to meet the demand for high accuracy and strong robustness in practical engineering. In this paper, the trajectory tracking control for a new type of cable-driven large space manipulator is investigated. First, the kinematics and dynamics models of the cable-driven space manipulator are established by using the principle of virtual work. Then, a trajectory tracking control scheme is designed for the cable-driven space manipulator based on the time-delay estimation and the nonsingular terminal sliding mode control approach. The main advantage of the proposed control scheme is to improve the performance of the time-delay estimator by rationally introducing a tuning parameter, which improves the performance of the whole control system. The asymptotic stability of the resulting closed-loop system is proven by the Lyapunov stability theory. The simulation and experiment results show that the proposed control scheme can effectively overcome the influence of disturbance and achieve high-precision trajectory tracking control of the cable-driven space manipulator.

Finite-Time Sliding Mode Control Based on Unknown System Dynamics Estimator for Nonlinear Robotic Systems

This article proposes an unknown system dynamics estimator (USDE) based finite-time sliding mode control for nonlinear robotic systems with unknown dynamics. First, an USDE with only one tuned parameter is designed by using filter operations and invariant manifold to estimate the unknown system dynamics. Second, a novel sliding mode surface with faster response time is designed. By incorporating the USDE into the sliding mode surface, a composite sliding mode control (CSMC) is proposed to achieve better dynamic performance. With simple parameter turning, the CSMC can realize the high precision trajectory tracking control of robotic systems. Finally, simulation results illustrate the superiority of the proposed control strategy.

Model‐free prescribed performance fast nonsingular terminal sliding mode control with practical finite‐time stability of uncertain robot manipulators

AbstractThis paper addresses the problem of robust and high precision trajectory tracking control of uncertain robot manipulators with prescribed performance. Time delay estimation (TDE) technique is employed to estimate system model, then a new self‐adjusting strategy (SAS) is designed to adjust TDE gain online. Prescribed performance control (PPC) method is used to guarantee transient response speed and steady‐state accuracy. Moreover, the transform function of PPC employed in this paper has unlimited domain, which greatly improves the robustness and stability of system. An improved fixed‐time dynamical system is firstly deduced and analyzed, then a new fast nonsingular terminal sliding mode surface is designed to accelerate convergence rate of tracking errors. Finally, the whole system is strictly proven to be practical finite‐time stable, which means that tracking errors can converge to a small neighborhood of zero within a uniformly bounded convergence time. Main advantages of the proposed approach include model‐free, robust, singularity‐free, faster transient response and higher steady‐state tracking precision. Experimental results carried out on the Rethink Sawyer Robot also verified the effectiveness of the proposed scheme.

TDE-Based Adaptive Super-Twisting Multivariable Fast Terminal Slide Mode Control for Cable-Driven Manipulators With Safety Constraint of Error

An adaptive super-twisting multivariable fast terminal sliding mode control scheme based on time delay estimation (TDE) and asymmetric error constraints are proposed to guarantee high-precision trajectory tracking control of cable-driven manipulators under complicated unknown uncertainties. The control system is constrained by joint position errors, which are asymmetric and time-varying. First, the error range of the joints is designed to ensure that the deviation of the joint position from the desired profile is not too large while ensuring the safety performance of the manipulator, and the remaining set-total system dynamics are estimated and compensated using time-delay estimation. Secondly, the design analysis of the angular false expectation using safety constraint functions allows the constraints of different cross sections to be handled in a unified system architecture; the problem of robotic arm motion trajectories with output constraints and uncertainties is addressed through rigorous analysis. The super-twisting adaptive control effectively ensures fast, accurate and robust convergence of the algorithm in satisfying all constraints in operation, and the stability of the closed-loop control system is analyzed using the Lyapunov method. Finally, the effectiveness and superiority of the proposed adaptive hyper-torsional non-singular terminal sliding mode control scheme are verified by simulations and experiments in 2-DOF.

Discrete open-closed-loop PID-type iterative learning control for trajectory tracking of tracked mobile robots

In this article, a robust discrete-time open-closed-loop proportion integral differential (PID) -type iteration learning control (ILC) algorithm is developed for the high-precision trajectory tracking control of tracked mobile robots (TMRs) with external disturbances and noises. The proposed ILC algorithm adopts the past, current, and predictive learning error items of the former and current iterations to correct the current control input variables, which finally converges to the desired trajectory through continuous iterative learning. The convergence characterization of the algorithm for TMRs under both external disturbances and noises is carried on rigorous mathematical proof. Numerical simulations and physical experiments are provided to verify the feasibility and effectiveness of the algorithm. The comparative results of two ILC algorithms indicate that the tracking performance of the proposed ILC algorithm is superior to the traditional PID-type ILC algorithm in terms of tracking accuracy and convergence rate.

High-Precision Trajectory Tracking Control of a Multifrequency Whirling Orbit Using Adaptive Feedforward Cancellation for the Efficient Experimental Estimation of Fluid Force

Abstract In recent years, there has been a demand for turbomachinery with increasing speed, pressure, and compactness owing to the increasing demand for high output and efficiency. Consequently, various shaft vibration problems have become apparent. The rotor dynamic (RD) forces are one of the causes of these axial vibrations, which can lead to instability of the rotor system. To ensure the reliability of turbomachinery, the effect of RD fluid force should be analyzed at the design stage. In this study, high-precision tracking control of a complex orbit was analyzed using an experimental approach, and a highly efficient and low-dispersion estimation of the RD fluid force was achieved. The target was a parallel annular seal, and an experimental system was developed to control the rotor position using a piezo-electric actuator. Using the adaptive feedforward cancellation (AFC), we suppressed the periodic disturbance caused by rotation, whirling, and disturbances, such as noise that existed uniformly at all frequencies. Thus, a high-precision tracking control with an orbit tracking error of approximately 1 μm was achieved. The RD fluid force was estimated from the output signal of the AFC during high-precision tracking control, and the RD coefficient was calculated using spectral analysis. Consequently, a highly accurate RD fluid force estimation with reduced dispersion was achieved. In addition, a multifrequency orbit control and RD fluid force estimation method were developed to improve the efficiency of the RD force estimation, which agreed well with the results of a single-frequency orbit.

Trajectory Tracking Control Method Based on Adaptive Higher Order Sliding Mode

To resolve the problem of high-precision trajectory tracking control under interference conditions in a missile’s mid-guidance phase, according to the constructed nominal trajectory, an improved adaptive high-order sliding mode trajectory tracking controller (AHSTC) is proposed. In this method, the open-loop nominal trajectories are established according to the nonlinear programming and Gaussian pseudospectra method. A high-precision trajectory tracking controller is developed by designing a nonlinear sliding mode surface and an adaptive high-order sliding mode approaching law combined with the trajectory tracking nonlinear error model. To verify the effectiveness and superiority of the proposed method, analysis and simulation are carried out through the example of a missile mid-guidance phase tracking control. Compared to the linear quadratic regulator (LQR) and active disturbance rejection controller (ADRC) method, the simulation results show that the proposed AHSTC method shows faster convergence and improved tracking effect. Therefore, the proposed AHSTC method has a good results and engineering application value.

Novel fast fixed-time sliding mode trajectory tracking control for manipulator

This paper studies the issue of high-precision trajectory tracking control for manipulator systems with uncertainty disturbances and develops a fast fixed-time control scheme. First, a new type of (FTSM) surface is constructed by combining inverse trigonometric functions, regardless of the size of the system state, which can obtain a faster convergence velocity and high accuracy. The stabilization time of this sliding mode (SM) surface is independent of the initial state. Subsequently, on this basis, an adaptive fixed-time control method is constructed by combining adaptive techniques through the new fixed-time stability lemma proposed in this paper, under which the system's SM variables and tracking errors are guaranteed to reach the region near the equilibrium point at a fixed time while the adaptive law estimates the upper bound of the disturbance and effectively weakens the chattering phenomenon. Finally, the simulation comparison is carried out under different conditions, and the simulation results show the superiority of the control scheme with high precision, fast velocity, and good robustness.

Research on vibration suppression and trajectory tracking control strategy of a flexible link manipulator

Residual vibrations caused by point-to-point motions reduce the positioning accuracy and dynamic performance of flexible link manipulators, and the trajectory planning method, a well-known open-loop control strategy, has been proven to effectively suppress the residual vibration in point-to-point motion. However, this open-loop control method has limitations in dealing with model uncertainty and disturbance problems. In this paper, a control strategy based on dynamics-based trajectory planning and fuzzy self-tuning PD (FST PD) controller is proposed, and applied to achieve residual vibration suppression and trajectory tracking of a flexible link manipulator. To improve the trajectory tracking performance under external disturbances, this control strategy is combined with a linear extended state observer (LESO). Firstly, the dynamic model of the system is deduced using the floating reference frame and Lagrange equation. On this basis, the objective function to minimize the lateral deformation of the tip is constructed, and then the optimal trajectory is obtained by using the Crossbreeding PSO (CBPSO) algorithm. Secondly, the optimal trajectory is used as the desired trajectory to suppress residual vibration, and the FST PD controller combined with the LESO is used to achieve high-precision trajectory tracking control of the flexible link manipulator. Finally, the effectiveness and feasibility of the composite control strategy is verified through multiple simulations. The proposed method can provide support for vibration suppression of flexible link manipulators; meanwhile, the controller structure of this method is simple and easy to implement, and the use of sensors/actuators and other equipment in the system is reduced, which effectively reduces the economic cost.

Dynamic trajectory tracking method of UAV using L1 Adaptive Control

Abstract An attitude control method based on the L1 adaptive structure was proposed for the quadrotor aircraft with nonlinear, strong coupling, and underactuated characteristics during flight. Then introducing a dynamic point trajectory algorithm to solve the problem that traditional linear controller lacks robustness in the quadrotor aircraft. The adaptive controller can quickly estimate the state of the system then track and compensate for interference items. The dynamic point trajectory algorithm was able to calculate the expected trajectory and trajectory deviation of the disturbed aircraft, which improved the anti-interference ability and fault tolerance ability of the system. The simulation results indicate that the flight control system designed based on the L1 adaptive dynamic point method is qualified for achieving high-precision trajectory tracking control and the system has strong anti-interference capability and robustness in the nonlinear state.

Fuzzy-Torque Approximation-Enhanced Sliding Mode Control for Lateral Stability of Mobile Robot

Accurate path tracking and stability are the main challenges of lateral motion control in mobile robots, especially under the situation with complex road conditions. The interaction force between robots and the external environment may cause interference, which should be considered to guarantee its path tracking performance in dynamic and uncertain environments. In this article, a flexible lateral control scheme is considered for the developed wheel-legged robot, which consists of a cubature Kalman algorithm to evaluate the centroid slip angle and the yaw rate. Furthermore, a fuzzy compensation and preview angle-enhanced sliding model controller to improve the tracking accuracy and robustness. Finally, some simulations and experimental demonstrations using the four-wheel-legged robot (BIT-NAZA) are carried out to illustrate the effectiveness and robustness, and the proposed method has achieved satisfactory results in high-precision trajectory tracking and stability control of the mobile robot.

Compound Impedance Control of a Hydraulic Driven Parallel 3UPS/S Manipulator

The hydraulic parallel manipulator combines the high-power density of the hydraulic system and high rigidity of the parallel mechanism with excellent load-carrying capacity. However, the high-precision trajectory tracking control of the hydraulic parallel manipulator is challenged by the coupling dynamics of the parallel mechanism and the high nonlinearities of the hydraulic system. In this study, the trajectory control of a 3-DOF symmetric spherical parallel 3UPS/S manipulator is evaluated. Focusing on the highly coupling and nonlinear system dynamics, a compound impedance control method for a hydraulic driven parallel manipulator is proposed, which combines impedance control with the spatial motion characteristics of a parallel manipulator. The control strategy is divided into the inner and outer loops. The inner loop controls the impedance of the actuator in the joint space, and the outer loop controls the impedance of the entire platform in the task space to compensate the coupling of the actuators and improve the tracking accuracy of the moving platform. Compound impedance control does not require force or pressure sensors and is less dependent on modeling precision. The experimental results show that the compound impedance control effectively improves the tracking accuracy of the moving platform. This research proposes a compound impedance control strategy for a 3-DOF hydraulic parallel manipulator, which has high tracking precision with a simple and cheap system configuration.

High-Precision Trajectory Tracking Control of Cable-Driven Parallel Robots Using Robust Synchronization

Cable-driven parallel robots (CDPRs) are a new type of parallel robots that use cables to control a mobile platform. They possess several advantages, including large workspace, low inertia, and high payload capacity. However, there are several problems in the high-precision trajectory tracking control of CDPRs. On the one hand, all the cables must remain in tension during the entire motion process. On the other hand, the controller design is subjected to model uncertainties and external disturbances. Accordingly, this article proposes a robust synchronization control (RSC) scheme in the cable length space to achieve high-precision trajectory tracking. The synchronization control ensures motion coordination among all the cables and prevents cable relaxation, whereas the robust control eliminates modeling errors and restrains external disturbances. The uniformly ultimate boundedness of the tracking and synchronization errors in the closed-loop system equation was proved using the Lyapunov theory. Simulations and experiments of the trajectory tracking control were both implemented on a three-degree-of-freedom CDPR. Compared with the adaptive robust control scheme and the augmented proportional derivative scheme on the premise of the approximate energy consumption, the proposed RSC scheme could reduce not only the tracking errors of the cables but also the synchronization errors between adjacent cables. Moreover, the RSC scheme could significantly improve the trajectory tracking accuracy of the mobile platform. The robustness of this scheme was verified using load experiments and torque-disturbance experiments.

High-Precision Trajectory Tracking Control for Space Manipulator With Neutral Uncertainty and Deadzone Nonlinearity

This brief investigates the high-precision trajectory tracking control of space manipulator after capturing an unknown target. The neutral uncertainty induced by parameter variation poses great challenges to the controller design. Moreover, the existence of actuator deadzone nonlinearity makes the situation more complicated. In order to address the aforementioned difficulties, a novel control scheme is proposed in this brief. First, to reduce the conservativeness in the descriptions of uncertainties, the dynamic of space manipulator is described by an uncertain system with neutral uncertainty, state-dependent uncertainty, and norm-bounded uncertainty for the first time. Then, by incorporating a novel deadzone compensation control effort, a composite controller is proposed to attenuate these uncertainties and compensate the deadzone nonlinearity. Finally, stability and robustness analyses are carried out, and simulation results are given to demonstrate the effectiveness of the proposed methods.

Modeling and Discrete-Time Terminal Sliding Mode Control of a DEAP Actuator with Rate-Dependent Hysteresis Nonlinearity

Dielectric electro-active polymer (DEAP) materials, also called artificial muscle, are a kind of EAP smart materials with extraordinary strains up to 30% at a high driving voltage. However, the asymmetric rate-dependent hysteresis is a barrier for trajectory tracking control of DEAP actuators. To overcome the barrier, in this paper, a Hammerstein model is established for the asymmetric rate-dependent hysteresis of a DEAP actuator first, in which a modified Prandtl-Ishlinskii (MPI) model is used to represent the static hysteresis nonlinear part, and an autoregressive with exogenous inputs (ARX) model is used to represent the linear dynamic part. Applying Levenberg-Marquardt (LM) algorithm identifies the parameters of the Hammerstein model. Then, based on the MPI model, an inverse hysteresis compensator is obtained to compensate the hysteresis behavior. Finally, a compound controller consisting of the hysteresis compensator and a novel discrete-time terminal sliding mode controller (DTSMC) without state observer is proposed to achieve the high-precision trajectory tracking control. Stability analysis of the closed-loop system is verified by using Lyapunov stability theorem. Experimental results based on a DEAP actuator show that the proposed controller has better tracking control performance compared with a conventional discrete-time sliding mode controller (DSMC).

An improved adaptive fuzzy backstepping control for nonlinear mechanical systems with mismatched uncertainties

ABSTRACTWhen the nonlinear mechanical system has mismatched uncertainties, it is difficult to design control algorithm to achieve high precision trajectory tracking control. Traditional backstepping control is an effective control method for uncertain, mismatched nonlinear systems, but there is inherent problem of “complexity due to the explosion of terms”. In this paper, based on the backstepping method, only one fuzzy system is used to approximate the unknown nonlinear functions, the unknown control gain and the differential of virtual control law of each subsystem. In order to reduce the influence of fuzzy approximation error and external interference, the above control scheme is further improved by designing special adjustable control parameters and first order low pass filter. The improved control scheme not only improves the control precision of the system obviously, but also solves the problem of “explosion of terms”, and greatly reduces the initial control input, and provides the conditions for the practical application. The simulation results show the effectiveness of the proposed methods.