Disturbance Estimation Scheme Research Articles

Event-triggered adaptive disturbance rejection for marine surface vehicles with unknown dynamics and disturbances

This article presents an event-triggered adaptive disturbance rejection scheme for marine surface vehicles with unknown model dynamics and external disturbances. The ocean environmental disturbances are expressed as a series of sinusoidal superpositions with unknown frequencies, amplitudes and phases. By incorporating the adaptive internal model principle, the disturbance rejection is transformed into the adaptive control problem. The adaptive laws and disturbance filter achieve online disturbance estimations. The adaptive neural backstepping is employed to derive the trajectory tracking control law. The event-triggering mechanism is utilized to reduce the wear and tear of thrusters. The event-triggered adaptive disturbance rejection control does not require a priori knowledge of model dynamics and can be treated as a model-free disturbance estimation and rejection scheme. It is theoretically demonstrated that the closed-loop tracking control system is semi-globally stable and the tracking error can be adjusted to be small. Illustrative results on a 1:70 scaled model CyberShip II validate the control scheme.

Disturbance observer-based robust adaptive control for uncertain actuated nonlinear systemwith disturbances

PurposeThe aim of this research paper is to design a disturbance observer (DO)-based robust adaptive tracking control of uncertain nonlinear system subject to unknown nonlinear disturbance.Design/methodology/approachTo achieve desired control objectives, i.e. nonlinear trajectory tracking and disturbance attenuation, firstly, a control scheme is designed based on the adaptive criteria integrated in sliding mode control (SMC). In the second step, the disturbance estimation criterion is designed followed by patching with the controller obtained in the first step. Following the control development, using the Lyapunov candidate function, the stability criterion is ensured by designing appropriate adaptive gains.FindingsIn this paper, a robust adaptive nonlinear tracking method is presented. The findings includes the design of adaptive gains for the control parameters involved in the robust SMC technique, i.e. adaptive criterion is designed for the switching gain as well as for the gain used in sliding mode surface. Furthermore, a disturbance estimation criterion is developed to attenuate nonlinear disturbances with variable frequency and magnitude. Finally, the disturbance estimation scheme is combined with the control technique to obtain DO-based control (DOBC) algorithm.Practical implicationsSliding mode control is a powerful robust control method. And, combining it with the DO achieves the control objectives of plants subject to disturbances and uncertainties. However, usually the uncertainties and disturbances are unknown and time varying. Thus, during practical implementation, designing the standard SMC is a challenging task due to the constant gains involved in the control design. Hence, it is important to have a criterion which adapts to the varying dynamics of plants due to the uncertainties and disturbances for achieving practical implementation of the control system.Originality/valueSliding mode control has been widely used for achieving the desired control objectives and robustness in the close-loop nonlinear systems. Besides, the SMC technique has been combined with the DOs as well. However, mostly the ideal conditions were considered during these developments, which required the control gains to be designed simply by manual tuning appropriately. However, by considering the real-time dynamics, uncertainties and disturbances, the constant control gain criteria can fail. Furthermore, due to external and internal disturbances, the model plant can vary with time. Thus, it is important to design the adaptive criteria for the control gains in DOBC schemes.

Hybrid Estimation Strategy-Based Anti-disturbance Control for Nonlinear Systems

In this article, an anti-disturbance control design is presented for nonlinear systems based on a hybrid disturbance estimation scheme. This scheme features the capability of making full use of the incomplete knowledge on disturbance dynamics. By embedding the known information, the disturbance interval observer is developed to generate boundaries to cover individually each element of external disturbances. Through synthesizing a tangent barrier Lyapunov function-based estimation switching mechanism, the modified disturbance observer is proposed to take appropriate values between the boundaries as the estimation. By using this estimation, the anti-disturbance control compensates for external disturbances. It is proved that the system states stay within a specified region and converge to a small neighborhood of the origin. Finally, the numerical simulation is presented to illustrate the effectiveness and benefits of the estimation scheme and the control design.

Disturbance Observer Based Control Design via Active Disturbance Rejection Control: A PMSM Example

A new Disturbance Observer Based (DOB) controller design procedure is here obtained via a reinterpretation of the disturbance estimation scheme, present in the Extended State Observer (ESO) based Active Disturbance Rejection (ADR) control scheme. If the reinterpreted disturbance estimation process is explicitly used, now, in combination with an ADR controller, the overall total disturbance effects are substantially diminished in the feedback loop, beyond that achievable by ESO-based ADR control alone. The context is that of nonlinear differentially flat systems, simplified to Kronecker chains of integrations. A Permanent Magnet Synchronous Motor (PMSM) example is examined and its performance is assessed from an experimental setting.

Sliding mode observer design for fault and disturbance estimation using Takagi–Sugeno model

This paper presents an actuator fault and disturbance estimation scheme using sliding mode observer (SMO) based on Takagi–Sugeno (TS) fuzzy system model. The TS model is first transformed in order to decouple disturbance and faults. Then a TS fuzzy SMO is developed for the transformed system. Finally, the disturbance and the fault are estimated using equivalent output error. The stability of the proposed observer is analyzed and its performances are tested for a doubly fed induction generator with actuator fault and disturbance.

Sliding mode observer design for fault and disturbance estimation using Takagi-Sugeno model

Abstract This paper presents an actuator fault and disturbance estimation scheme using sliding mode observer (SMO) based on Takagi–Sugeno (TS) fuzzy system model. The TS model is first transformed in order to decouple disturbance and faults. Then a TS fuzzy SMO is developed for the transformed system. Finally, the disturbance and the fault are estimated using equivalent output error. The stability of the proposed observer is analyzed and its performances are tested for a doubly fed induction generator with actuator fault and disturbance.

Discrete Time Sliding Mode Controller Using a Disturbance Compensator for Nonlinear Uncertain Systems

In this paper, we propose a new sliding mode control for discrete time nonlinear uncertain systems. The uncertainties include both parametric uncertainties in the state model and external disturbances. To recover the lost invariance and robustness properties of discrete sliding mode control, we develop a disturbance estimation scheme to compensate the system uncertainties without affecting the control law. This control approach ensures the stability of the closed loop system as well as chattering reduction. The performance of the proposed controller is applied to control the motion of a cart-inverted pendulum used as a typical benchmark of nonlinear systems. The stabilization problem of the inverted pendulum system is to design a controller to keep the pendulum in its unstable equilibrium point in the presence of disturbances and parameters variation. The simulation result shows the effectiveness of the control design.

Robust observer-based optimal linear quadratic tracker for five-degree-of-freedom sampled-data active magnetic bearing system

ABSTRACTThis paper presents three observer/Kalman filter identification (OKID) approaches and develops a robust observer-based optimal linear quadratic digital tracker (LQDT) for the five-degree-of-freedom (five-DOF) sampled-data active magnetic bearing (AMB) system with various disturbances. The more detailed objectives are: (i) to construct both an equivalent linear time-invariant discrete-time model and its state estimator via the proposed OKID approaches for the AMB system, which might be an unknown nonlinear time-varying unstable system with both a specified rotation speed and a sampling rate; (ii) to provide an adaptive disturbance estimation scheme, which establishes an equivalent input disturbance (EID) estimator for the AMB system with unexpected disturbances; and (iii) to develop a robust observer-based optimal LQDT for the sampled-data AMB system with both a pre-specified time-varying speed and unexpected disturbances. The developed LQDT is able to recover the displacement of the rotor to the pre-specified trajectory position whenever it deviates from such trajectory.

A Novel Disturbance Estimation Scheme for Formation Control of Ocean Surface Vessels

To achieve high-accuracy formation control of multiple ocean surface vessels, the external disturbance acting on each vessel should be accommodated. In this paper, a novel disturbance estimation scheme is presented to solve this problem, and to provide the future formation controller design with precise estimation information. This approach is developed in the theoretical framework of a terminal sliding mode observer. The proposed observer is able to precisely estimate external disturbance after finite time. It is shown by Lyapunov stability analysis that the estimation error for external disturbance will converge to zero after finite time. A fast and precise estimation for external disturbance is achieved. Numerical example is further presented to validate the effectiveness of the developed disturbance estimation approach.

Disturbance Estimation, Compensation, and Dynamic Shaping: New Approach and an Application to Output Stabilization of Multiple Cooperative Control

This paper introduces a new disturbance estimation scheme, and a possible application to relative output stabilization of multiple systems. Using the proposed disturbance estimation scheme, total unknown external disturbance applied to a plant is estimated and compensated. Moreover, the model difference between an actual system and a desired system is also estimated and compensated. For the purpose of general use of the disturbance estimation scheme as an unknown input observer (UIO), a parameterized design method is given, even for the unstable and nonminimum phase systems. For the relative output stabilization of multiple systems, second-order consensus algorithm is additionally used. A case study, simulations, and experimental tests sequentially validate the proposed estimation and control methods.

Sliding-Mode Tracking Control With DNLRX Model-Based Friction Compensation for the Precision Stage

This paper concerns the development of a sliding-mode tracking controller with friction compensation for a precision positioning stage with cross-roller guides. Experiments including prerolling and rolling friction regimes are conducted, and then a two-stage parameter estimation algorithm is used to identify the parameters of a friction dynamic model (Dynamic NonLinear Regression with direct application of eXcitation, DNLRX, model). This model allows the estimation of the friction force in combination with the system dynamics against displacement, and can be used as a feed-forward controller to compensate for the friction effect. To compensate for model error and uncertain disturbances, an integral sliding-mode controller with a disturbance estimation scheme is designed and combined with the DNLRX feed-forward controller to control the motion of a precision stage. Experimental results show that with the proposed controller, tracking performance can be improved.

Decentralized discrete-time quasi-sliding mode control of uncertain linear interconnected systems

In this paper, a new global decentralized discrete-time quasi-sliding mode control of linear interconnected systems is presented. The proposed controller is free of chattering problem and can be applied to a broader class of large-scale systems. Additionally, it is capable to deal with both known and unknown interconnections among the subsystems. Stability of the reduced-order interconnected systems is analyzed using Lyapunov approach. The proposed decentralized controller guarantees the reachability of the connective sliding manifold. The resultant dynamics are proved to be globally asymptotically stable. Furthermore, the controller is made robust to external disturbances by employing a disturbance estimation scheme. The simulations are performed on model of a two-area power generation system and the results show the efficacy of the proposed scheme.

Active vibration control in Duffing mechanical systems using dynamic vibration absorbers

Abstract This paper deals with the multi-frequency harmonic vibration suppression problem in forced Duffing mechanical systems using passive and active linear mass–spring–damper dynamic vibration absorbers. An active vibration absorption scheme is proposed to extend the vibrating energy dissipation capability of a passive dynamic vibration absorber for multiple excitation frequencies and, simultaneously, to perform reference position trajectory tracking tasks planned for the nonlinear primary system. A differential flatness-based disturbance estimation scheme is also described to estimate the unknown multiple time-varying frequency disturbance signal affecting the differentially flat nonlinear vibrating mechanical system dynamics. Some numerical simulation results are provided to show the efficient performance of the proposed active vibration absorption scheme and the fast estimation of the vibration disturbance signal.

Tracking control of a precision stage with integral sliding-mode friction estimator

This work concerns the development of a integral sliding-mode tracking controller with friction estimator for a precision positioning stage. This stage is supported by cross roller guides, therefore, one of the main disturbances during dynamic motion is the friction force. In order to overcome the uncertainties and the effect of friction, an integral sliding-mode controller with uncertainty and disturbance estimation scheme is designed to control the motion of the stage. Comparing with conventional PID controllers, the experimental results show that with this controller the tracking errors can be reduced significantly.

Sliding-Mode Tracking Control of a Precision Stage

This work concerns the development of a sliding-mode tracking controller for a precision positioning stage. This stage is supported by cross roller guides, therefore, one of the main disturbances during dynamic motion is the friction force. In order to overcome the effect of friction, an integral sliding-mode controller with friction disturbance estimation scheme is designed to control the motion of the stage. Comparing with conventional PID controllers, the experimental results show that with this controller the tracking errors can be reduced significantly.

Development of a novel multi-axis nano-positioning and the spiral tracking control

This paper presents the design of a sliding-mode controller for a piezoelectric-driven nanometer resolution stage. The nanometer resolution stage is developed using the features of a flexible structure, and is driven by piezoelectric actuators and also uses capacitance sensors for position feedback. The hysteresis characteristic of the piezoelectric actuators is one of the major deficiencies in a wide variety of precise tracking positioning controls. In order to design the control system, the open-loop characteristics of this nanometer resolution stage are investigated. According to the open-loop characteristics, each pair of piezoelectric actuator and capacitance sensor is treated as an independent system and modeled as a first order linear model coupled with hysteresis. When the model is identified, the hysteresis nonlinearity is linearized then the linear system model with uncertainty is used to design the controller. When designing the controller, the sliding-mode disturbance estimation and compensation scheme is used. The structure of the proposed controller is similar to the PID controller. Thus, it can be easily implemented.

Model reference adaptive control-based adaptive current control scheme of a PM synchronous motor with an improved servo performance

A model reference adaptive control (MRAC)-based current control scheme of a PM synchronous motor with an improved servo performance is presented. Although the predictive current control is known to give ideal transient and steady-state responses among various PWM inverter-fed current control schemes for a PM synchronous motor, its steady-state response may be degraded under the motor parameter variations. To overcome such a limitation, the disturbances caused by the parameter variations will be estimated using an MRAC technique and compensated by a feedforward manner. Thus, the steady-state control performance can be effectively improved, while retaining its good dynamic performance. The proposed control scheme does not require the measurement of the phase voltage unlike the conventional disturbance estimation scheme using observer. This can be an effective way considering the phase voltage contains much harmonics as well as noise. The asymptotic stability of the overall system is proved and the adaptation laws are derived by the Lyapunov stability theory. The proposed scheme is implemented using DSP TMS320C31 and the effectiveness is verified through the comparative simulations and experiments.

Sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner

AbstractThis paper presents the sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner (Z, θx, θy). This nanopositioner is actuated by piezoelectric actuators. Capacitive gap sensors are used for position feedback. In order to design the feedback controller, the open‐loop characteristics of this nanopositioner are investigated. Based on the results of the investigation, each pair of piezoelectric actuators and corresponding gap sensors is treated as an independent system and modeled as a first‐order linear model coupled with hysteresis. When the model is identified and the hysteresis nonlinearity is linearized, a linear system model with uncertainty is used to design the controller. When designing the controller, the sliding‐mode disturbance (uncertainty) estimation and compensation scheme is used. The structure of the proposed controller is similar to that of a proportional integral derivative controller. Thus, it can be easily implemented. Experimental results show that 3‐nm tracking resolution can be obtained. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Control of a Five-Degrees-of-Freedom Nanopositioner

This paper presents the tracking control of a five-degrees-of-freedom nanopositioner. This nanopositioner is actuated by piezoelectric actuators. Capacitive gap sensors are used for position feedback. Firstly, the modified Prandtl-Ishlinskii (MPI) model is used to model the hysteresis nonlinearity of piezoelectric actuator, and then its inverse is used to cancel out the hysteresis nonlinearity. In order to design the feedback controller, the linearized open-loop characteristics of this nanopositioner are investigated. Based on the results of investigation, each pair of piezoelectric actuator and corresponding gap sensor are treated as independent systems and modeled as a uncertain first order linear model. When the model is identified, the linear system model with uncertainty is used to design the controller. The sliding-mode disturbance (uncertainty) estimation and compensation scheme is used in this study. Experimental results are given to show the effectiveness of the proposed method.

서보 드라이브 성능 향상을 위한 AC 서보 전동기의 적응형 전류 제어

서보 드라이브의 성능 향상을 위해 AC 서보 전동기의 MRAC (Model Reference Adaptive Control) 기반 적응 전류 제어 기법이 제시된다. 인버터 구동 전류 제어 기법 중 예측형 전류 제어 기법은 이상적인 과도 응답 및 정상 상태 응답을 주지만, 전동기 파라미터 변화 시 정상상태 응답 성능이 저하된다. 이러한 제한 점을 극복하기 위해 파라미터 변화에 의한 외란이 MRAC 기법에 의해 추정되어 전향 제어에 의해 보상된다. 제안된 방식은 기존의 외란 추정 방식과 달리 관측기 구성을 위한 인버터의 상전압 측정을 필요로 하지 않는다. 제안된 적응 제어 방식의 점근 안정성과 효과적으로 서보 드라이브에 적용될 수 있음이 입증된다. 제안된 방식이 DSP TMS320C31을 이용하여 구현되고 유용성이 시뮬레이션과 실험을 통해 입증된다.