Nonlinear Error Feedback Control Research Articles

Space and time joint optimization for vertical takeoff and landing aircraft in dense obstacles and interference environments

ABSTRACT The Vertical Takeoff and Landing Aircraft (VTOL) is capable of both low-speed hovering and high-speed flight. This paper proposes an autonomous motion planning and anti-wind disturbance control algorithm for the VTOL, implemented spatial and temporal joint motion planning for VTOL, under the limitation of maximum flight speed of the aircraft, VTOL can achieve fully autonomous flight in complex environments, which can realize the autonomous flight of a single aircraft in a complex and dense environment, achieve real-time perception and avoidance of static and dynamic obstacles. The information generated by motion planning includes the position, velocity, and acceleration information of the aircraft, and proposes a wind disturbance estimation and active control strategy in a wind disturbance environment, accurate estimation of wind disturbance is achieved through a state observer, and the wind disturbance was suppressed through nonlinear error feedback control law, implemented wind disturbance estimation and suppression for aircraft in wind disturbance environments, and achieved complete autonomous motion planning and trajectory tracking of VTOL in a complex and wind disturbance environment. Our work can provide a basis for the collaborative control of multiple UAVs.

Fault-tolerant control of automatic carrier landing using direct lift control based on nonsingular terminal sliding mode and active disturbance rejection control

This paper presents a fault-tolerant control scheme, combining nonsingular terminal sliding mode and active disturbance rejection control (NTSM-ADRC) to address actuator failure and external disturbances during the automatic carrier landing process of a carrier-based aircraft using direct lift control (DLC). First, the carrier-based aircraft model, the carrier air-wake model, and the actuator fault model were established. Second, the NTSM-ADRC controller is designed, The unmodeled dynamics of the system, the air-wake disturbance, and the fault term are treated as total disturbances and estimated accurately by extended state observer (ESO). To improve the response characteristics of the controller, the nonlinear error feedback control law is designed by combining the NTSMC. The Lyapunov function is constructed to prove the stability of the closed-loop system. The controller is applied to the aircraft DLC channel, attitude auxiliary channel, and approach power compensation system. The DLC improves the performance of fixed-wing aircraft by directly generating high lift through the flaps to change the aircraft trajectory. Finally, the method is tested by introducing various types of actuator failures. Simulation results demonstrate that the designed longitudinal fault-tolerant carrier landing system exhibits strong robustness and fault tolerance, thereby improving the accuracy of aircraft landing trajectory tracking.

Disturbance Rejection Speed Control Based on Linear Extended State Observer for Isokinetic Muscle Strength Training System

Isokinetic muscle strength training is a type of rehabilitation therapy that can effectively improve the motor dysfunction of limbs and enhance joint muscle strength. In active isokinetic training, how to plan the speed reasonably and improve the performance of speed control to fit individualized needs is the core problem of isokinetic muscle strength training equipment control. In this study, a control strategy for isokinetic muscle strength training equipment is proposed, which identifies the user&#x2019;s motion intention and performs speed planning according to the user&#x2019;s motion participation so that the equipment produces a dynamic damping effect. This ensures active interaction between the user and the equipment and meets the force-speed requirements of elbow joint muscle training. To handle the uncertain disturbance in the training process, a linear extended state observer is used to estimate the disturbance term, and a tracking differentiator and nonlinear error feedback control are used to improve the speed tracking performance. The experimental results show that the proposed control scheme realizes effective speed control in isokinetic muscle strength training. <i>Note to Practitioners</i>&#x2014;The bottleneck of isokinetic muscle strength training equipment control system lies in how to plan the speed according to the patient&#x2019;s movement intention reasonably, and how to improve the performance of speed control in the process of rehabilitation training. This paper designs a speed auto disturbance rejection control strategy for isokinetic muscle strength training system with external interference and model uncertainty in practical application. The experimental results show that the performance of the controller is better than the traditional PI controller, and it can realize isokinetic muscle training. This study provides a method for practitioners interested in developing control systems for isokinetic rehabilitation training equipment.

Rotating mirror servo system control based on modified sliding mode-active disturbance rejection controller

In order to improve the tracking accuracy and robustness of the rotating mirror servo system, a modified sliding mode-active disturbance rejection control (MSM-ADRC) strategy is proposed. Firstly, the structure and working principle of the rotating mirror servo system are analysed, and its mathematical model is established to prepare for the design of the controller. Then, a MSM-ADRC is proposed to reduce the influence of unknown disturbance and improve the tracking accuracy. Among them, the modified sliding mode extended state observation (MSM-ESO) is designed by replacing the traditional nonlinear function with the designed optimal control function, which enhances the observation accuracy of the system state quantity and total disturbance. Meanwhile, an improved approach law is proposed, and an improved sliding mode nonlinear error feedback control law (MSM-NLSEF) is designed based on this approach law, which improves the convergence speed and accuracy of the control law. In addition, the stability of the designed MSM-ESO and MSM-NLSEF is proved. Finally, the proposed control method is validated by simulation and experimental comparison with other state-of-the-art controllers. Results reveal that the proposed control method has satisfying tracking performance and strong disturbance rejection ability.

Nonlinear ESO-based tracking control for warehouse mobile robots with detachable loads

It is an essential task to guarantee satisfactory tracking performance for a warehouse mobile robot with a detachable load. To this end, a nonlinear extended state observer (ESO)-based tracking control is investigated via a double closed-loop framework in this paper. A kinematics controller is designed in an outer loop to generate desired velocities for the warehouse mobile robot. A nonlinear ESO with an improved error function is proposed in an inner loop to estimate load variations and internal unmodeled dynamics. Then a nonlinear error feedback controller based on estimation values is given to track the desired velocities from the outer loop. Simulation and experiment results illustrate the effectiveness and superiority of the proposed control strategy.

Application of social spider optimization and improved active disturbance rejection controller in hierarchical control of cooperative multi-lift with four unmanned helicopters

To achieve the three-dimensional free movement of the slung load, a load-leading hierarchical control strategy has been adopted recently which divides the cooperative multi-lift system into a load layer, a cable layer, and an aircraft layer. But there exists a non-convex optimization problem in the cable layer when computing the force of each cable, and more control difficulties of the aircraft due to the additional disturbances resulting from the load movement. To solve these problems, an application of the social spider optimization (SSO) algorithm and the improved active disturbance rejection controller (IADRC) in hierarchical control of cooperative multi-lift with four unmanned helicopters is proposed in this study. First, the unmanned helicopters as well as the load are modeled. Then the three layers mentioned above are designed, respectively. Specifically, an optimization method combining SSO with the MATLAB/fmincon function is proposed to solve the non-convex problem in the cable layer. And within the unmanned helicopter layer, the fuzzy theory is introduced into the nonlinear error feedback control strategy of the traditional active disturbance rejection controller (ADRC) to realize the control of the unmanned helicopter. At last, some simulations are carried out, and the results indicate that the system has higher calculation efficiency, smaller steady-state error, and better adaptability to trajectory change or load release with the designed hierarchical control strategy.

Finite-time tracking control for a variable stiffness pneumatic soft bionic caudal fin

This paper introduces a finite-time tracking control method for a pneumatic soft bionic caudal fin with driving fins and variable stiffness fins. Designs, fabrications and kinematic modelling are shown for the pneumatic soft bionic caudal fin. Based on a kinematic model, a dynamic nonlinear system is established for the driving fins in the pneumatic soft bionic caudal fin. A nonlinear error feedback controller is designed for the pneumatic soft bionic caudal fin via an extended state observer based on a second-order finite-time tracking differentiator. Finite-time convergence of tracking error is proved by Lyapunov approach for the dynamic nonlinear system. Finally, experimental and simulation results are shown to verify the effectiveness for the design of the pneumatic soft bionic caudal fin and the proposed control method of the dynamic nonlinear system, respectively.

Nonlinear Error Feedback Positioning Control for a Pneumatic Soft Bionic Fin via an Extended State Observer

This paper presents a nonlinear error feedback controller for a pneumatic soft bionic fin based on an extended state observer. Manufacturing process is shown for a bionic stingray with the pneumatic soft bionic fin. A test experiment is carried out for a driving part in the pneumatic soft bionic fin by upper chamber inflated and lower chamber inflated with different internal pressures. A dynamic nonlinear system is established for the pneumatic soft bionic fin by test experiment results and kinematic modeling. Total disturbances of the dynamic nonlinear system are estimated and compensated by the extended state observer and the nonlinear error feedback controller, respectively. Moreover, both the convergence of the extended state observer and stability of the dynamic nonlinear system are proved by Lyapunov approach. Finally, simulation results are shown to verify the effectiveness of the proposed control method for the pneumatic soft bionic fin.

Path Following Control of Autonomous Ground Vehicle Based on Nonsingular Terminal Sliding Mode and Active Disturbance Rejection Control

Due to the strong nonlinearity, coupling characteristics, external disturbance, and complex driving conditions, it is difficult to establish an accurate mathematical model for the autonomous ground vehicle (AGV). This requires the AGV path following controller to have strong robustness. In this paper, a robust AGV path following control strategy that is based on nonsingular terminal sliding mode (NTSM) and active disturbance rejection control (ADRC) is presented. First, the complex path following problem is simplified to a simple yaw angle tracking problem by constructing a desired yaw angle function that satisfies that the displacement deviation of AGV converges to zero when the actual yaw angle approaches the desired yaw angle. Second, an NTSM-ADRC controller is designed for the system, which uses the extended state observer to estimate and compensate the unmodeled dynamics and unknown external perturbations of the system in real time. In order to improve response characteristics of the controller, the nonlinear error feedback control law is designed by combining the NTSM and exponential approximation law. In contrast to the existing work, the improved controller can use the simple two-degree-of-freedom linear vehicle dynamic model to provide good performance in a range of driving conditions. Finally, the CarSim-Simulink simulation results of typical conditions show that the proposed control strategy can make the AGV follow the reference path quickly and accurately while ensuring the stability of the vehicle and has strong robustness.

Active Disturbance Rejection Control Strategy for Signal Injection-Based Sensorless IPMSM Drives

In high-frequency injection-based sensorless interior permanent magnet synchronous motor (IPMSM) drives, digital filters and position tracking observers are used for signal processing, but deteriorate the dynamic performance of the drive system. To address this problem, an active disturbance rejection control (ADRC) strategy-based sensorless control scheme for IPMSM drive is proposed in this paper. The influence of digital filters and Luenberger observer on the speed-loop bandwidth and the stability are analyzed. A modified position tracking observer based on the model prediction method is presented to increase the speed-loop bandwidth. To improve the stiffness performance, an ADRC strategy is proposed by adopting an extended state observer and a nonlinear error feedback controller, which can estimate and compensate for the total disturbance of the sensorless drive system. The proposed sensorless control scheme was adopted on a sensorless IPMSM drive, and the experimental results confirmed that the expected dynamic performance could be achieved.

Multicontroller Positioning Strategy for a Pneumatic Servo System Via Pressure Feedback

A backstepping-based controller is designed to improve positioning speed of a pneumatic servo system by pressure feedback. A least-square method is used to identify parameters for obtaining a relatively accurate proportional valve model. In addition, an extended state observer is designed to estimate total nonlinearities caused by friction and unmodeled dynamics. A backstepping-based controller is proposed to increase convergence speed, and another nonlinear error feedback controller is used to keep positioning accuracy. That is, a multicontroller strategy containing the two controllers is introduced to improve performance of the pneumatic servo system. Finally, experimental results with response time $0.5$ s and accuracy $0.05$ mm indicate the capabilities of the proposed method.

Weight‐transducerless control strategy based on active disturbance rejection theory for gearless elevator drives

Direct-drive traction systems applying the permanent magnet synchronous motor have become the trend of modern gearless elevators. To estimate and reject the non-linear and uncertain load disturbance effectively during the elevator startup, a novel active disturbance rejection control (ADRC) strategy adopting extended state observer (ESO) and non-linear error feedback (NLEF) controller is proposed to attenuate the elevator car sliding without using weight-transducer. By using the weight-transducerless control strategy, the sliding distance and speed can be suppressed to the extent that it could ensure the riding comfort. The proposed ADRC scheme will also accelerate the dynamic response and enhance the system robustness. Both the parameter selection and the stability of ESO are analysed according to the application requirements, and the contrastive analysis of the functions selected in NLEF controller is performed via Lyapunov theory. The feasibility of the proposed strategy is verified by the experimental results on an 11.7 kW elevator traction machine.

Active Disturbance Rejection Position Control for a Magnetic Rodless Pneumatic Cylinder

This paper presents an active disturbance rejection position control scheme for a magnetic rodless cylinder in servo systems without pressure states. It is very hard to achieve precise position control of magnetic rodless cylinders due to nonlinearity from large friction force and hysteresis. In this paper, the overshoot, which has a negative influence on position control, is effectively reduced by using a tracking differentiator. Furthermore, the nonlinearity is estimated by a designed extended-state observer. In addition, the self-stable region theory is used to prove the convergence of the extended-state observer. Finally, both control precision and response speed are guaranteed via a nonlinear error feedback controller in the pneumatic system. Experimental results show that the steady-state error within 0.05 mm is achieved for a step signal.

Attitude Active Disturbance Rejection Control of Agile Satellite

Based on the mission requirements of agile satellite, the control method of large angle maneuver was investigated in this paper. The single gimbal control moment gyroscope (sgcmg) of pyramid configuration is taken as the executor of the satellite. In order to avoid the singularity of sgcmgs, robust pseudo-inverse steering logic is used. An attitude active disturbance rejection controller (adrc) was designed. The expected attitude maneuver information that got by gauss pseudo-spectral method (gpm) took the place of that got by tracking differentiator (td). The constraints of satellite and sgcmgs are considered. Dynamics decoupling and disturbance observation of satellite were realized by using nonlinear extended state observer (neso). Then based on neso, nonlinear error feedback controller (nlsef) effectively suppresses the disturbance. The simulation results show that the attitude active disturbance rejection controller has steady control performance and can reject the disturbance better.