High-gain Disturbance Observer Research Articles

Speed Control for PMSM with Fast Variable-Speed Sliding Mode Control via High-Gain Disturbance Observer

Since robustness only exists on the sliding mode/surface, sliding mode control is non-globally stable. Therefore, shortening the time to reach the sliding mode is an important method of improving sliding mode robustness. However, there is an inherent contradiction between rapidity and overshoot. Therefore, ensuring rapid convergence without overshoot is a worthwhile research problem. Consequently, this paper proposes a design for a fast variable speed reaching law (FVSRL) to improve the quality of sliding mode control. The constructed approach rate is based on a variable speed term, an exponential term, and a fast term, ensuring rapid convergence without overshoot. At the same time, a high-gain disturbance observer is employed for feedforward compensation. Finally, the designed reaching law is validated by comparing it with conventional exponential approach rates and a new sliding mode reaching law, demonstrating its superior performance. Detailed comparative and quantitative analyses of the simulation results using the conventional exponential reaching law, the new sliding mode reaching law, and the FVSRL are performed, utilizing metrics such as integrated square error, integral time square error, integrated absolute error, and integral time absolute error.

Finite-Time Robust Path-Following Control of Perturbed Autonomous Ground Vehicles Using a Novel Self-Tuning Nonsingular Fast Terminal Sliding Manifold

This work presents a finite-time robust path-following control scheme for perturbed autonomous ground vehicles. Specifically, a novel self-tuning nonsingular fast-terminal sliding manifold that further enhances the convergence rate and tracking accuracy is proposed. Then, uncertain dynamics and external disturbances are estimated by a high-gain disturbance observer to compensate for the designed control input. Successively, a super-twisting algorithm is incorporated into the final control law, significantly mitigating the chattering phenomenon of both the input control signal and the output trajectory. Furthermore, the global finite-time convergence and stability of the whole proposed control algorithm are proven by the Lyapunov theory. Finally, the efficacy of the proposed method is validated with comparisons in a numerical example. It obtains high control performance, reduced chattering, fast convergence rate, singularity avoidance, and robustness against uncertainties.

Filter-Based Disturbance Observer and Adaptive Control for Euler–Lagrange Systems With Application to a Quadrotor UAV

In this paper, a filter-based control scheme is developed for Euler-Lagrange systems with unknown parameter and external disturbance. Two controllers are proposed under the filtering framework, namely the adaptive controller and the disturbance observer-based controller, respectively. A set of low-pass filters are employed in the control design to derive useful filter outputs, which can provide the design freedom for the parameter estimator or the disturbance observer. For the adaptive controller, a certainty equivalent adaptive law is designed in such way that dominates the cross term between the estimation error and the filtered regression matrix to achieve better performance compared with classical estimators. For the disturbance observer-based controller, a high-gain disturbance observer is constructed for the lumped uncertainty with an arbitrary order for users to determine. Experimental results are presented to verify the effectiveness of the proposed schemes on a quadrotor UAV in several cases.

An Improved Model−Free Current Predictive Control of Permanent Magnet Synchronous Motor Based on High−Gain Disturbance Observer

Predictive current control (PCC) is an advanced control strategy for permanent magnet synchronous motors (PMSM). When the motor drive system is undisturbed, predictive current control exhibits a good dynamic response speed and steady−state performance, but the conventional PCC control performance of PMSM that depends on the motor body model is vulnerable to parameter perturbation. Aiming at this problem, an improved model−free predictive current control (IMFPCC) strategy based on a high−gain disturbance observer (HGDO) is proposed in this paper. The proposed strategy is introduced with the idea of model−free control, relying only on the system input and output to build an ultra−local current prediction model, which gets rid of the constraints of the motor body parameters. In the paper, the ultra−local structure is optimized by comparing and analyzing the equation of the state of the classical ultra−local structure and PMSM system. The system’s current state variables are incorporated into the ultra−local system modeling, as a result, the current estimation errors existing in the classical ultra−local structure are eliminated. For the unmodeled and parametric perturbation part of the ultra−local system, a high−gain disturbance observer is designed to estimate it in real time. Finally, the proposed IMFPCC strategy is compared with the conventional model−based predictive current control (MPCC) and the conventional model−free predictive current control (CMFPCC) in simulation and experiment. The results show that the current steady−state error of the IMFPCC strategy in the case of parameter variation is only 50% of the MPCC method, which proves the effectiveness and correctness of the proposed strategy.

Fast integral terminal sliding mode control with a novel disturbance observer based on iterative learning for speed control of PMSM

This study revolves about the speed control of a permanent magnet synchronous motor (PMSM) with torque ripple and external disturbance. To enhance the performance of the PMSM speed control in response, robustness and torque ripple suppression, a hybrid control technique is presented by combining a novel disturbance observer based on iterative learning strategy (ILC-DOB) and a fast integral terminal sliding mode control (FITSMC) method. Firstly, an iterative learning law is used to enhance the conventional high-gain disturbance observer (DOB) to improve the estimation performance for periodic disturbance. Then, a new fast integral terminal sliding mode surface is proposed to increase the tracking error convergent speed of the traditional integral terminal sliding mode control (ITSMC) when the speed error is distant from the equilibrium point. Finally, the estimated total disturbance is incorporated as a feed-forward compensation to the enhanced FITSMC. According to experimental results, the presented method can ensure better speed-tracking performance and significant disturbance rejection capability of the PMSM drive system.

Synchronous control of multiple electrohydraulic actuators under distributed switching topologies with lumped uncertainty

A leader-following synchronous control is proposed in multiple electrohydraulic actuators (MEHAs) under distributed switching topologies to guarantee the follower electrohydraulic actuators (EHAs) tracking the leader motion. Each EHA has a 3-orders nonlinear dynamics with lumped uncertainties involving uncertain hydraulic parameters and unknown external load. Then a quasi-synchronization controller together with a high-gain disturbance observer is designed by Lyapunov techniques to guarantee the synchronous errors asymptotically convergence to a zero neighborhood. Finally, the effectiveness of the proposed quasi-synchronous controller is verified by both simulation and experimental bench such that the finite EHA nodes achieve leader-following synchronous motion under distributed switching topologies.

Adaptive Control for Multi-Shaft with Web Materials Linkage Systems

In this paper, a fuzzy disturbance observer and a high-gain disturbance observer based on a variable structure controller are applied to deal with imprecise multi-shaft with web materials linkage systems taking into account the variation of the moment of inertia. Specifically, a high-gain disturbance observer and an adaptive fuzzy algorithm are separately applied to estimate system uncertainties and external disturbances. The high-gain disturbance observer is designed with auxiliary variables to avoid the amplification of the measurement disturbance, and the fuzzy disturbance observer has the advantage that it does not depend on model information. The convergence properties of the tracking error are analytically proven using Lyapunov’s theory. The obtained numerical results demonstrate the validity and the adaptive performance of the proposed control law in case the system is exposed to uncertainties and disturbances. Important remarks on the design process and performance benchmarks of the two observers are also demonstrated.

Output feedback control of electro-hydraulic asymmetric cylinder system with disturbances rejection

To achieve accurate position control of electro-hydraulic asymmetric cylinder system with only available displacement signal, an output feedback controller is proposed in this paper. The dynamic model of the system is expressed as a Brunovsky form, which helps to estimate the system states and simplify the controller structure. Then Levant differentiator is introduced to estimate the position, velocity and acceleration of the asymmetric cylinder system based on the output signal, which can reduce the impact of measurement noise compared to the means of calculating the time derivative of the displacement signal directly. Besides, a high gain disturbance observer is designed to reject the lumped disturbance rejection of the system including parameter uncertainty, modelling error and external disturbance. Moreover, a sliding mode surface is introduced to the controller design and a robust item with continuous function is applied to compensate for estimation errors. According to Lyapunov theory, the developed output controller is pledged to be stable that can realize disturbance rejection control as well as backstepping-free control. Furthermore, a large-size asymmetric cylinder experimental rig is set up to simulate practical applications environment. Comparative experimental results reveal the validity and potential practical meaning of the developed control approach.

Dynamic surface control based on high-gain disturbance observer for electro-hydraulic systems with position/velocity constraints

The electro-hydraulic system is widely used in industrial production due to its high power-to-weight ratio, but the heavy-duty characteristics make the electro-hydraulic system subject to large disturbance force even if the actuator moves slightly, especially in mobile machines and multi-actuators system. Therefore, a position and velocity constraints method based on barrier Lyapunov function is proposed to guarantee the tracking error limited in a strict range to avoid the large disturbance force. Besides, the external disturbance, parameters uncertainty and modeling errors in the asymmetric cylinder electro-hydraulic systems affect the accuracy of position tracking seriously. So a high-gain disturbance observer is designed to estimate the lumped disturbance of the system, which can avoid amplification of the noise during the states measurement. In addition, dynamic surface control based on backstepping method is adopted to avoid the derivative explosion phenomenon when calculating the derivatives of virtual control inputs, which reduces the computational complexity of the system significantly. To verify the effectiveness of the proposed controller, proportional-integral controller and adaptive controller are designed to be compared with the high-gain disturbance observer–based dynamic surface controller with the backstepping method, and the comparison results show that the proposed controller has a more precise trajectory tracking performance.

측정 잡음을 고려한 1기 무한모선 시스템의 고장 판별을 위한 DQN 기반 외란 관측기 설계

Increasing demand on electric power supply results in a need of an intelligent method for fast detection of various failures in the power system. This paper presents a reinforcement learning-based disturbance observer (DOB) design for the determination and protection against a line fault occurred in the single-machine infinite bus (SMIB) power system. Whilst a high gain disturbance observer could estimate the system states and the external disturbance successfully, the high gain of the observer can cause problems in the presence of the measurement noise. When measurement noise exists in the output, fault detection methods based on the estimated states may often result in false alarms. To solve the problem, this paper designs an adaptive DOB using Deep Q-Network (DQN) which is one of reinforcement learning algorithms. For the proposed observer design, this paper explains the definitions of the state, the action, and the reward for the reinforcement learning. Matlab simulations have been conducted based on the observer gains trained using the power angle data from the swing equation. The results show that the estimation performance of the proposed DQN-based observer can be satisfactory against both an external disturbance and the measurement noise.

Overcurrent Protection Control Design for DC-DC Buck Converter With Disturbances

This paper deals with the output voltage regulation problem for dc-dc buck converters. Overcurrent protection and disturbances are both taken into consideration. The main challenge of control design is how to ensure that the current constraints are not violated at any time in the presence of disturbances. At first, a high-gain disturbance observer is utilized to estimate the disturbances. Then, a novel punishment mechanism for the inductor current is designed in the control scheme. Finally, based on the novel current-constrained technique and the high-gain disturbance observer, a composite control approach is proposed. The new control method not only guarantees the current within the required range but also has a nice ability on the disturbance rejection. In the meantime, rigorous stability proof is also presented. The theoretical analysis also explains how disturbances affect the satisfaction of the current constraints. The experimental results on a buck converter system are illustrated to verify the feasibility and effectiveness of the proposed control scheme.

Open-loop-based Island-mode Voltage Control Method for Single-phase Grid-tied Inverter with Minimized LC Filter

This paper proposes an island-mode voltage control method by using an open-loop control applying a high-gain disturbance observer (DOB) for a single-phase inverter with a low capacitance output filter. The output voltage is distorted with the low capacitance by the conventional method which consists of a PID regulator for an automatic voltage regulator (AVR) and a PI regulator for an automatic current regulator (ACR). In order to compensate the output voltage distortion, the high-gain DOB for the output voltage is applied in the open-loop-based voltage control. DOB is implemented into a field-programmable gate array (FPGA) with high-speed sampling. In the LC filter of a 1-kW prototype, the impedance of the inductor is minimized to 1.0% of the normalized inverter impedance, whereas the admittance of the capacitor is reduced to 0.25% of the normalized inverter admittance. By the proposed method, the inverter output voltage total harmonic distortion (THD) is reduced by 82.4% even with the diode rectifier load compared to the conventional voltage control, whereas the constant output voltage is achieved regardless of any conditions of load.

Nonlinear Steering Wheel Angle Control Using Self-Aligning Torque with Torque and Angle Sensors for Electrical Power Steering of Lateral Control System in Autonomous Vehicles.

The development of sensor technology enabled the use of composite sensors to measure the torque and angle of steering wheels at gradually decreasing costs while maintaining the required safety. The electric power steering (EPS) is vital to the safety of the car, therefore it is not worth sacrificing safety to save cost and the SWA control with angle sensor gradually becomes the mainstream. Existing methods to control steering wheel angle (SWA) for EPS consider the self-aligning torque as a disturbance that should be rejected. However, this torque is useful to return the SWA from an outward to the center position. Hence, we propose a nonlinear control of SWA using the self-aligning torque for EPS in the lateral control system of autonomous vehicles. The proposed method consists of a high-gain disturbance observer and a backstepping controller, where the former aims to estimate the self-aligning torque, and an auxiliary state variable prevents using the derivative of the measured signal. The nonlinear controller is designed via backstepping to bound the SWA tracking error. The self-aligning torque provides damping that can improve the controller tracking when following the same direction of the input torque on the steering wheel control. In this case, the control input can be reduced by the damping effect of the self-aligning torque. The performance of the proposed method is validated through EPS hardware-in-the-loop simulation.

High-Gain Disturbance Observer-Based Robust Load Frequency Control of Power Systems with Multiple Areas

This paper proposes a high-gain disturbance observer (HDOB)-based controller for load frequency control (LFC) of power systems with multiple areas. The main goal of LFC problem is to maintain the frequency to its nominal value. The objective of this paper is to reject frequency variations due to abrupt load changes and diverse uncertainties (e.g., inertia and damping parameters, and interconnection topology, etc.) by employing the HDOB for the LFC. The simulation results demonstrate the effectiveness of the proposed HDOB-based LFC by showing that it successfully rejects frequency variations owing to load changes and frequency variations occurring in various locations in interconnected power systems. Besides, it is shown that the proposed LFC can eliminate frequency deviations although there are delays in transmission among the power systems with multiple areas.

고이득 외란 관측기에 기반한 입력 제약 조건이 있는 불확실한 선형 시스템의 강인 추종 제어

고이득 외란 관측기에 기반한 입력 제약 조건이 있는 불확실한 선형 시스템의 강인 추종 제어

Robust tracking performance of linear induction motor‐based automatic picking system using a high‐gain disturbance observer

To operate the movable ejectors of an automatic picking system (APS) with high dynamics and high precision, a robust speed tracking controller design for a single-sided linear induction motor (LIM) is presented using a high-gain disturbance observer method. The thrust disturbance as well as the mechanical parameter variation due to the mass change influences directly the tracking control performance of APS. To guarantee robustness in the presence of such uncertainty, a high-gain disturbance observer-based linear quadratic regulator (LQR) is designed from the mechanical dynamics. Since the estimated disturbance effectively cancels out real uncertainties in the system, the resulting system behaves like the closed-loop system consisting of the disturbance-free nominal model and the LQR. Since MATLAB–Simulink does not support a library for a LIM, a Simulink library model has been developed using the LIM dynamics. To verify that the proposed scheme has a robust control nature, the comparative simulations are carried out based on the library. The whole control system is implemented using DSP TMS320F28335 for a LIM driven by a three-phase voltage-fed pulse-width modulation inverter. Through comparative experimental results in the presence of disturbances, the effectiveness and robustness of the proposed scheme are verified.

High-Gain Disturbance Observer-Based Backstepping Control With Output Tracking Error Constraint for Electro-Hydraulic Systems

We propose a high-gain disturbance observer (HGDOB)-based backstepping control with position tracking error constraint for electro-hydraulic systems to improve the position tracking performance in the presence of disturbances. The HGDOB is designed to estimate the disturbances that include the friction, the load force, and the parameter uncertainties. Auxiliary state variables are proposed to avoid amplification of the measurement noise in the HGDOB. To compensate for the disturbances while guaranteeing tolerance of the position tracking error, the backstepping controller is proposed by using the barrier Lyapunov function. As a result, the proposed method satisfies the output constraint and improves the position tracking performance in the presence of disturbances. Its performance is validated via simulations and experiments.

고성능 자동피킹 시스템을 위한 선형 유도 모터의 고이득 관측기 기반의 강인 추종 제어

To implement an automatic picking system (APS) in distribution center with high precision and high dynamics, this paper presents a high gain observer-based robust speed controller design for a linear induction motor (LIM) drive. The force disturbance as well as the mechanical parameter variations such as the mass and friction coefficient gives a direct influence on the speed control performance of APS. To guarantee a robust control performance, the system uncertainty caused by the force disturbance and mechanical parameter variations is estimated through a high gain disturbance observer and compensated by a feedforward manner. While a time-varying disturbance due to the mass variation can not be effectively compensated by using the conventional disturbance observer, the proposed scheme shows a robust performance in the presence of such uncertainty. A Simulink library has been developed for the LIM model from the state equation. Through comparative simulations based on Matlab - Simulink, it is proved that the proposed scheme has a robust control nature and is most suitable for APS.

High Gain Disturbance Observer-Based Control for Nonlinear Affine Systems

This paper proposes a high gain disturbance observer based control approach for nonlinear systems. Compared with previous works, it can admit a much larger class of disturbances produced by nonlinear exo-systems. Our approach will follow the framework of the two-stage design procedure, which separates the disturbance observer design from the controller design. Under certain conditions, the observer error for the disturbances generated by nonlinear exo-systems globally and asymptotically converges on zero and the stability of the closed-loop system is guaranteed. An illustrative example of a two-link robot manipulator with limit cycles disturbance is presented to show the effectiveness of the proposed method.

Flatness-based linear output feedback control for disturbance rejection and tracking tasks on a Chua's circuit

A linear output feedback controller is developed for trajectory tracking problems defined on a modified version of Chua's circuit. The circuit modification considers the introduction of a flat input, i.e. a suitable external control input channel guided by (a) the induction of the flatness property on a measurable output signal of the circuit and (b) the physical viability of the control input. A linear active disturbance rejection control based on a high-gain linear disturbance observer, is implemented on a laboratory prototype. We show that the state-dependent disturbance can be approximately, but arbitrarily closely, estimated through a linear high-gain observer, called a generalised proportional integral (GPI) observer, which contains a linear combination of a sufficient number of extra iterated integrals of the output estimation error. Experimental results are presented in the output reference trajectory tracking of a signal generated by an unrelated chaotic system of the Lorenz type. Laboratory experiments illustrate the proposed linear methodology for effectively controlling chaos.