Disturbance Compensation Method Research Articles

Guaranteed Disturbance Compensation and Robust Fault Detection Based on Zonotopic Evaluation

ABSTRACTIn the context of model‐based fault detection, it is crucial to achieve strong robustness against disturbance and noise. However, the existing robust fault detection methods typically address disturbance and noise in a centralized manner to enhance robustness, which may cause some conservatism since the dynamic characteristics of disturbance and noise are considerably different. In addition, most of the existing model‐based fault detection method is implemented with constant thresholds, which may further introduce conservatism. In this context, this paper proposes a guaranteed disturbance compensation and robust fault detection method based on zonotopic evaluation for the discrete‐time systems subject to unknown but bounded disturbance and noise. To this end, a disturbance compensation controller is developed based on technology to obtain guaranteed control performance. Moreover, the control performances with or without disturbance compensation are analyzed based on zonotopes. By considering the disturbance dynamic characteristics, an extended fault detection observer (EFDO) is created to pursue robustness to disturbance, noise, and sensitivity to fault simultaneously. Meanwhile, a multi‐objective EFDO is devised by exploiting the index and index as the criteria within the finite‐frequency domain. Furthermore, the zonotopic residual evaluation is further deployed to generate the residual boundary, which helps to reduce the conservatism of fault detection. The superiority of the proposed method is theoretically analyzed. Simulation results also validate the effectiveness and superiority of the proposed method in disturbance compensation fault detection.

Robust control strategy of VSC-HVDC systems based on feedback linearization and disturbance compensation method

The Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) technology has become the development direction of new energy grid-connected, DC power transmission and island power supply technology in the future due to its superior characteristics. The effective and reliable control method is important to realize the stable operation of VSC-HVDC system during disturbances. However, the common adopted control scheme for VSC-HVDC system lacks of superior dynamic response when system suffers external disturbances. Although some relatively new control methods have been continuously proposed and applied to the VSC-HVDC system, such as no-beat control, fuzzy control, sliding mode control and repetitive control, etc., they usually depend on detailed and exact system model. This paper focuses on the feedback linearization and disturbance compensation methods in VSC-HVDC system. Firstly, the mathematical model of VSC-HVDC system in dq coordinate system with modeling errors and external disturbances is derived. Secondly, in order to improve the dynamic response and robustness of the control, the feedback linearization and disturbance compensation method is used and designed to realize the decoupling control of the VSC-HVDC system. Finally, the VSC-HVDC system with conventional control and the proposed control is compared and analyzed on the PSCAD/EMTDC simulation platform. The results show that the proposed controller based on feedback linearization and disturbance compensation principle has better dynamic performance and higher robustness of regulation performance.

Stability Control of Quadruped Robot Based on Active State Adjustment.

The quadruped robot has a strong motion performance and broad application prospects in practical applications. However, during the movement of the quadruped robot, it is easy to be affected by external disturbance and environmental changes, which makes it unable to achieve the ideal effect movement. Therefore, it is very important for the quadruped robot to adjust actively according to its own state detection. This paper proposes an active state adjustment control method based on its own state, which can realize disturbance recovery and active environment adaptation. Firstly, the controller is designed according to the physical model of the quadruped robot, and the foot forces are optimized using the quadratic program (QP) method. Then, the disturbance compensation method based on dynamic analysis is studied and combined with the controller itself. At the same time, according to the law of biological movement, the movement process of the quadruped robot is actively adjusted according to the different movement environment, so that it can adapt to various complex environments. Finally, it is verified in a simulation environment and quadruped robot prototype. The results show that the quadruped robot has a strong active disturbance recovery ability and active environment adaptability.

Torque Disturbance Compensation Method Based on Adaptive Fourier-Transform for Permanent Magnet Compressor Drives

The large fluctuating torque disturbance of the single-rotor permanent magnet compressor has a significant impact on the drive system. An adaptive Fourier-transform-based torque disturbance compensation method is proposed to improve the control performance in this article. Based on the analysis of compressor load torque characteristics, a self-adjusting strategy is proposed to reduce the compensation error of the traditional open-loop Fourier-transform scheme. The compensation current is adaptively generated by adopting an indirect iterative learning mechanism that can obtain the multifrequency torque disturbances information in real-time. The proposed method does not require the accurate compressor parameters and the discrimination of harmonic disturbances, which has satisfactory suppression ability for the multifrequency torque disturbance. The convergence and parameter sensitivity of the proposed method are analyzed theoretically. The effectiveness of this method is verified by experiments on a 1.5-kW permanent magnet compressor drive platform.

Robust Stabilization of Underactuated Two-Wheeled Balancing Vehicles on Uncertain Terrains with Nonlinear-Model-Based Disturbance Compensation

Two-wheeled inverted pendulum (TWIP) vehicles are prone to lose their mobility and postural stability owing to their inherently unstable and underactuated dynamic characteristics, specifically when they encounter abruptly changed slopes or ground friction. Overcoming such environmental disturbances is essential to realize an agile TWIP-based mobile platform. In this paper, we suggest a disturbance compensation method that is compatible with unmanned TWIP systems in terms of the nonlinear-model-based disturbance observer, where the underactuated dynamic model is transformed to a fully actuated form by regarding the gravitational moment of the inverted pendulum as a supplementary pseudo-actuator to counteract the pitch-directional disturbances. Consequently, it enables us to intuitively determine the disturbance compensation input of the two wheels and the pitch reference input accommodating to uncertain terrains in real time. Through simulation and experimental results, the effectiveness of the proposed method is validated.

An Improved Dual-Loop Feedforward Control Method for the Enhancing Stability of Grid-Connected PV and Energy Storage System Under Weak Grids

Although the stability of the grid-connected photovoltaics (PV) and energy storage systems under weak grids has been widely researched, the classical improvement methods focus more on suppressing the harmonics introduced by the phase-locked loop (PLL). Furthermore, the current distortion caused by the DC voltage loop is difficult to be eliminated. In this study, based on the hybrid energy storage system of battery-supercapacitor, a dual-loop compensation method is proposed. First, the small-signal model and output impedance matrix are built in d-q axis. Second, for different disturbance loops, a DC voltage loop disturbance compensation method based on power feedforward is proposed to suppress the harmonics caused by the DC voltage controller (DVC). In addition, a voltage feedforward PLL disturbance compensation method is proposed, which can reduce the PLL perturbations and revise the output impedance to improve system stability. Finally, the output impedance frequency characteristic analysis and the hardware-in-the-loop (HIL) simulation results show that the proposed control method can effectively improve the stability of the system under weak grids.

A disturbance-compensation-based sliding mode control scheme on mode switching condition for hybrid electric vehicles considering nonlinear backlash and stiffness

In this study, a coordinated control problem of power sources and actuators of a series-parallel hybrid electric vehicle on mode switching condition is addressed. There exist numerous nonlinear factors in the hybrid driveline system which induce system disturbance and will deteriorate the control performance on mode switching condition. However, coupled system nonlinearity is not taken into consideration for controller design on mode switching condition, which can lead to severe driveline oscillation and thus vehicle longitudinal jerk. For this reason, a disturbance observer and compensation method is introduced to resolve the control problem on mode switching condition. First, an analytic model of driveline torsional vibration considering disturbance brought by system nonlinearity is established and simplified for controller design. Based on the simplified model, a disturbance observer-sliding mode control strategy is proposed to suppress mode switching vibration. Numerical simulation is carried out to validate control performance of the DOB-SMC strategy. Simulation results demonstrate that DOB-SMC strategy has better ability to cancel the unwanted effects of disturbance brought by system nonlinearity compared with sliding mode control method, which can be regarded as an effective approach to attenuate vehicle longitudinal jerk and thus improve ride comfort on mode switching condition.

Gain Function-Based Visual Tracking Control for Inertial Stabilized Platform with Output Constraints and Disturbances

In this paper, a composite control strategy is proposed to deal with output constraints and disturbances of the visual tracking system for an inertial stabilized platform, which combines active disturbance compensation and the variable gain function technique. Firstly, the model of system considering multi-source disturbances is established, where the controlled output is the constrained position of the target in the image plane. Secondly, in order to avoid the tracked target being lost in the field of view of the camera, a control method based on the variable gain function technique is designed to ensure that the controlled output remains within the feasible range. Moreover, the active disturbance estimation and compensation method is introduced to improve the anti-disturbance ability of the system under the situation of small output error, obtaining satisfactory tracking performance. The stability analysis and the proof of constrained output are given following the controller design. Finally, results of simulation and experiments are shown to illustrate the promised advantages of the proposed composite control approach.

Feedforward-control-based nonlinear control for overhead cranes with matched and unmatched disturbances

In this paper, a composite control method consisting of a feedforward control method and a sliding mode control method is proposed for control of the overhead crane. For existing methods, only matched disturbances are taken into consideration, unmatched disturbances are usually neglected. To address this drawback, a disturbance compensation method is constructed to attenuate the effects of disturbances and a continuous global sliding mode control method is devised to guarantee the stability. More precisely, we first make some transformations on the original model. Then, a disturbance compensation method is proposed and a continuous global sliding mode control scheme is introduced straightforwardly. The stability of the closed-loop system and the convergence of the states are proven through complete theoretical analysis. Finally, simulation and experimental tests are carried out to illustrate the regulation control property of the designed approach as well as its excellent disturbance rejection characteristic.

Acceleration-based disturbance compensation for elastic rack-and-pinion drives

Rack-and-pinion drives are mainly used for large machine tools and are often operated with indirect position control. Due to the lack of state information on the output side, this results in reduced accuracy regarding the table position. In addition, the system can only react inadequately to disturbances outside the control loop, meaning that often insufficient results can be achieved in typical application scenarios such as milling. To meet the increasing dynamic and accuracy requirements of the modern manufacturing industry, this paper presents a highly dynamic acceleration-based disturbance compensation method. For this purpose, the table acceleration is estimated using a dynamical model of the drive train and compared to the signal from an additional acceleration sensor attached to the machine table. Based on the resulting difference, an additional compensation torque is provided, which suppresses the disturbance in counterphase. The approach is tested experimentally on an open control platform with industrial drive components and the behavior is investigated based on compliance frequency responses and externally applied milling forces. At the same time, a standardized parametrization methodology is developed and the robustness is evaluated by varying table masses. In summary, a considerable improvement of the dynamic disturbance behavior can be achieved compared to the conventional system without compensator.

Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order Plants

This paper analyzes the first-order and first-order time-delayed systems control approaches, focusing mainly on unstable systems. First, it discusses asymmetries between the disturbance observer-based (DOB) control with decoupled tracking and the disturbance rejection responses, stressing applications to stable and unstable plants. The paper analyzes some DOB-based control solutions for unstable systems which do not use internal closed-loop stabilization. The novelty of the paper is thorough study accompanied with a comprehensive explanation of the differences between two distinct approaches: the transfer-function- and the closed-loop-based feedforward control approach from the point of view of control constraints. It is clearly illustrated that the main cause of instability of DOB-based approaches, applied to unstable systems, is given by their effort to impose on the system the unstable dynamics of the chosen nominal process model. It is also shown that the closed-loop stability of the DOB-based control, applied to the unstable systems, can be restored by using the supervising reference model control (RMC). The main novelty of the proposed approach is that its eliminates the mentioned stability problems while maintaining the full functionality of the chosen control structures. RMC has so far only been implemented for generating a setpoint feedforward signal. However, by generalization of this approach for disturbance rejection, the methodology of DOB design, based on nominal models, can be extended to the control of unstable systems. Without the use of disturbance reference models, the interactions of the master stabilizer with disturbance compensation cannot be eliminated. Without the internal stabilization, the stable transients can only be achieved by designing controllers based on stable models, instead of unstable ones. The existing modifications of DOB-based schemes for unstable plants, proposed in some references, are shown to lead to traditional Proportional-Integrative (PI) control, thus losing all the advantages over the PI controllers. In all the considered structures, the role of integrating models is also emphasized.

직동외란의 효율적 억제기능을 갖는 서보계 설계법에 관한 연구

This paper presents an interference disturbance compensation method for the connected system. The disturbance is generated from the system motion such that it directly affects the relative motion. For example, in the robot system, the arm motions influence each other because the arms are connected in series. If we design a servosystem for controlling the robot motions including arm angle, the interference disturbance should be carefully considered. The reason for this is that it influences and works as the disturbance which degrades the tracking performance. Therefore, the authors developed a novel interference disturbance rejecting method by simple feedforward control strategy based on the framework of robust servosystem design. By applying the proposed method to a 2DOF robot system, its effectiveness was evaluated.

Analysis and on-line compensation of gravity disturbance in a high-precision inertial navigation system

Zero velocity update technology (ZUPT) has frequently been used as a tool to reduce divergence when the inertial navigation system (INS) is working in pure inertial mode. In general, the normal gravity model is adopted to calculate the gravity vector, and the effect of gravity disturbance is neglected. We present a new point of view to explain the influence of gravity disturbance on INS and point out that gravity disturbance is one of the most significant error sources of the high-precision INS. Two real-time gravity disturbance compensation methods are proposed. An about 110-km-long vehicle test has been conducted in mountainous terrain with a drastic change of gravity disturbance. The test results proved the correctness of the new explanation and the feasibility of the two on-line compensation algorithms for land vehicles. With gravity disturbance compensation in conjunction with ZUPTs, the total horizontal error at the end of the test was reduced from 8.93 to 3.75 m, and the elevation error was reduced from 1.63 to 0.80 m.

Reference Sliding Variable Based Chattering-Free Quasi-Sliding Mode Control

The aim of this study is to design a new sliding mode controller with disturbance compensation for disturbed sampled data systems. As in such systems, the state measurements and control signal updates take place at the discrete time instants only, discrete time sliding mode analysis must be applied. Considering previous findings in this field, a new quasi-sliding mode controller, based on a reference sliding variable profile is developed. In order to eliminate the chattering problem, the reference is generated with a simple, nonswitching type reaching law. Next, the reference is incorporated into the control law for the real disturbed system. This approach limits the disturbance influence on the plant and results in an ultimate band width of O(T) order. Furthermore, the proposed control strategy is extended with a disturbance compensation method, which allows to achieve the quasi-sliding mode band width of O(T 2 ) order. Hence, the system's robustness improves with each reduction of the discretization period T. The paper clearly shows that the proposed sliding mode controller guarantees stability of the closed-loop system and eliminates the chattering phenomenon.

Experimental Investigation of an Electro-Hydrostatic Actuator Based on the Novel Active Compensation Method

For electro-hydrostatic actuators (EHAs), how to estimate and compensate for the combined effects of the severe nonlinearity caused by inner leakage and friction, the parametric uncertainties of the hydraulic components due to the environment and the external disturbance remain the primary issues. In this paper, a novel four-loop cascade control based on the active disturbance compensation method was proposed to address the abovementioned problem. First, by dividing the model of an EHA, two low-order estimators were obtained rather than a high-order estimator, which are easier to be implemented. Further, pressure information of two chambers of the EHA was applied in the proposed controller to compensate for the mismatching disturbances directly. Finally, the experimental results proved that the proposed method improved the robustness and static state error by approximately 35% and 33%, respectively.

Experimental Verification of Deadbeat Control with 1-MHz Multisampling and Disturbance Compensation Method for Three Phase PWM Inverter

Experimental Verification of Deadbeat Control with 1-MHz Multisampling and Disturbance Compensation Method for Three Phase PWM Inverter

Providing Invariance to Disturbing Effects in Rail Lines

Introduction. The time interval systems for controlling train movement operated under the influence of significant industrial disturbances, interference from the electric current of traction rolling stocks, and significant climate changes that result in fluctuations of parameters of circuit elements. These factors lead to the appearance of internal disturbances. The fluctuations in a wide range of the conductivity of rail lines insulation are the main external disturbances leading to considerable changes of the informative parameter, the voltage at the output end of the rail line. At present, there are many methods for suppressing disturbances, which allow correcting fluctuations in the informative signal without deteriorating the quality of classification. The article deals with the problem of providing insensitivity of the output informative signal to the influence of disturbance by principles of coordinate compensation with a correcting link. Materials and Methods. To solve the problem, various methodologies of compensation for disturbances are considered in the paper; the method of coordinate compensation for disturbances at the input of a quadripole of rail lines is adopted as the main one. The equation of the transfer function of the correcting link is determined, assuming an indirect measurement of the input resistance of the rail line, which is a function of the conductivity of the insulation. Results. The article presents the results of the research of the invariant capabilities of the disturbance compensation principle. It is shown that disturbances compensation with a corrective link included at the input of a quadripole allows one to significantly reduce the dynamic range of the output informative signal change in each of the classes, i.e. classes have become more compact, and the quality of classification has become 5 times higher than in the absence of compensation of disturbances. Discussion and Conclusion. The results confirm the effectiveness of the proposed method for the coordinate compensation of disturbances in rail lines with an open circuit in the absence of the possibility for organizing feedback, a variable circuit in each of the classes of states, and the impossibility of creating a physical additional channel for the transmission of the disturbance. Using the proposed method in the construction of modern classifiers will significantly improve the stability of the functioning of train control systems; eliminate errors of the first kind, leading to unproductive idle train, and errors of the second kind, leading to accidents and crashes.

Sensorless Control for Permanent Magnet Synchronous Motor in Rail Transit Application Using Segmented Synchronous Modulation

This paper proposes a position sensorless control technique for permanent magnet synchronous motor (PMSM) used in rail transit application, where a segmented synchronous modulation (SSM) is usually applied. The arbitrary signal injection-based sensorless control is adopted to estimate rotor position. In a switching period, an oversampling technique is used to obtain the average current slope that contains the rotor position information during the active voltage-vector operation. In SSM, the hysteresis zone is set near the carrier ratio (CR) switching critical point to eliminate the influence of the repeated oscillation on the current measurement accuracy. Furthermore, a load disturbance compensation method is designed so that the failure of hysteresis zone is avoided. Through the analysis of power spectral density (PSD) of phase current, the optimization of harmonic energy distribution with hysteresis zone is also verified. The experimental results show that the proposed method can improve the position estimation precision during the fast CR transition, which can be effectively applied in SSM.

Harmonic Extended State Observer Based Anti-Swing Attitude Control for Quadrotor with Slung Load

During the flight of the quadrotor, the existence of a slung load will exert a swing effect on the system and the motion of which will significantly change the dynamics of the quadrotor. The external torque caused by the slung load can be considered as a kind of disturbance and it is a threat to the attitude control stability of the system. In order to solve this problem, a high precision disturbance compensation method is presented in this paper, based on the harmonic extended state observer (HESO). Firstly, a generic mathematical model for the quadrotor-slung load system is obtained via the Lagrangian mechanics, and according to the analysis of the slung load motion, we obtain the disturbance as a form of periodic equation. Secondly, based on the dynamic model of the disturbance, we propose a HESO to achieve high precision disturbance estimation and its stability is proved by Lyapunov theory. Thirdly, we designed an attitude tracking controller based on backstepping method, and discussed the stability of the entire system. Finally, numerical simulations and real time experiments are carried out to evaluate the performance of the proposed method. Our results show that the robustness of the quadrotor subject to slung load has been improved.

Magnetic heading compensation method based on magnetic interferential signal inversion

This paper presents a method for compensation of disturbances introduced by near-surface interference sources in the estimation of magnetic heading, based on the inversion of the interference signal. Firstly, magnetometer array is designed to measure magnetic vector and gradient signals of the same point. Invariants of magnetic gradient tensor measured by the array are used to determine whether there exists magnetic heading perturbation. Then the magnetic vector signals generated by the near-surface magnetic interference sources are calculated using the measured magnetic gradient signals based on the phase shift theorem of discrete cosine transform (DCT), and the background geomagnetic vector field is obtained by subtracting the inversed magnetic anomaly vector signals from the measured magnetic vector signals. Finally, the magnetic heading angle is obtained based on the compensated background geomagnetic vector field. Numerical examples and real experiments based our prototype array reveal reliability and the applicability of the proposed method.