Disturbance Rejection Ability Research Articles

FO improved fast terminal sliding mode control method for permanent‐magnet synchronous motor with FO disturbance observer

This study proposes a fractional-order (FO) improved fast terminal sliding mode controller for permanent-magnet synchronous motor speed regulation system. By designing an FO proportional-integral controller for current loops, an FO model between reference q -axis current and speed output is proposed. By introducing an FO terminal sliding mode surface, a novel FO terminal sliding mode controller is designed for speed loop to improve the speed tracking performance. The proposed FO controller can make speed reach reference value in finite time. Moreover, it is proved that the control time of the FO sliding mode controller is shorter than integer-order (IO) sliding mode controller. To further enhance the convergence speed, the fast terminal sliding mode control method is used. Meanwhile, FO disturbance observer is utilised to enhance the disturbance-rejection ability. The control law of the proposed controller is designed according to Lyapunov stability theorem. Finally, Simulation and experimental results demonstrate the effectiveness, high control performance and high disturbance-rejection ability of the proposed composite FO controller in comparison with IO controller.

Robust Speed Control of PMSM Using Sliding Mode Control (SMC)—A Review

Permanent magnet synchronous motors (PMSMs) are known as highly efficient motors and are slowly replacing induction motors in diverse industries. PMSM systems are nonlinear and consist of time-varying parameters with high-order complex dynamics. High performance applications of PMSMs require their speed controllers to provide a fast response, precise tracking, small overshoot and strong disturbance rejection ability. Sliding mode control (SMC) is well known as a robust control method for systems with parameter variations and external disturbances. This paper investigates the current status of implementation of sliding mode control speed control of PMSMs. Our aim is to highlight various designs of sliding surface and composite controller designs with SMC implementation, which purpose is to improve controller’s robustness and/or to reduce SMC chattering. SMC enhancement using fractional order sliding surface design is elaborated and verified by simulation results presented. Remarkable features as well as disadvantages of previous works are summarized. Ideas on possible future works are also discussed, which emphasize on current gaps in this area of research.

Improved predictive functional control for ethylene cracking furnace

The objective of this paper is to show the design and application of pass temperature balance control system using an improved predictive functional control method in eight 800 tone/year USC ethylene cracking furnaces. The advanced pass temperature balance controller is developed using the proposed method and implemented in proprietary APC-ISYS software, which is connected to Yokogawa distributed control system via an OPC server. The advantage of it lies in the fact that the dynamics of pass temperature with nonlinearity and time delay are described by Takagi–Sugeno model and transformed into time-varying extended state space model, and thus, the proposed controller can regulate pass temperature based on the extended state space formulation. In addition, the control law with a linear iterative form, easily applied to industrial process, is derived. The robust analysis for the set point, input disturbance and output disturbance to the output verifies the ability of tracking and disturbance rejection of the proposed method. Application results from an industrial furnace are shown to be markedly better in terms of lower variability in the outlet temperature of both the passes compared to the current proportional–integral–derivative control scheme.

Advanced Single-Phase DSC-Based PLLs

In three-phase systems, using the delayed signal cancelation (DSC) operators is one of the most popular approaches for designing advanced phase-locked loops (PLLs), particularly for applications where a high disturbance rejection ability is demanded. In single-phase systems, however, they have not received a considerable attention. The aim of this paper is to develop advanced DSC-based PLLs for single-phase applications. To this end, three PLLs are designed and presented. The first is based on adaptive DSC operators, and the other two are based on nonadaptive operators. The design aspects of these PLLs are discussed in detail, and their performances are evaluated using experimental results.

Integrated Modified Repetitive Control With Disturbance Observer of Piezoelectric Nanopositioning Stages for High-Speed and Precision Motion

The tracking performance of piezoelectric nanopositioning stages is vital in many applications, such as scanning probe microscopes (SPMs). Although modified repetitive control (MRC) can improve tracking performance for commonly used periodic reference input, it is sensitive to unexpected disturbances that deteriorate tracking precision, especially for high-speed motion. In order to achieve high-speed and precision motion, in this paper, a new composite control scheme by integrating MRC with disturbance observer (DOB) is developed. To simplify controller implementation, the hysteresis nonlinearity is treated as external disturbance and the proposed method is designed in frequency domain. The stability and robust stability are analyzed, and an optimization procedure to calculate the controller parameters is employed to enhance the performance to the maximum extent. To validate the effectiveness of the proposed method, comparative experiments are performed on a piezoelectric nanopositioning stage. Experimental results indicate that the hysteresis is suppressed effectively and the proposed method achieves high-speed and precision tracking with triangular waves references up to 25 Hz and improves the disturbance rejection ability with disturbances under different frequencies and robustness to model uncertainty through comparing with feedback controllers and MRC, respectively.

Disturbance frequency adaptive control for photo-electric stabilized platform based on improving extended state observation

Aiming at the problem of disturbance in the working process of a photoelectric stabilized platform, an improved algorithm based on improving extended state observer (ESO) technology is proposed. An extended state observer based on disturbance frequency adaptation was designed to reduce phase delay when the extended state observer observes second-order and above systems. The simulation experiment tested the disturbance rejection ability of the improved algorithm and compared it with the existing classical control method. The results show that the ESO can effectively suppress the influence of various frequency disturbances, and its anti-interference ability is clearly improved. Finally, an experiment was performed to test the disturbance rejection performance of the ESO when the speed disturbance rejection performance was between 0.1 Hz and 2.5 Hz. The results show that the improved algorithm has high practical value for improving the anti-disturbance performance of the system.

GPI observer‐based composite current‐constrained control approach for DC–DC buck converters

In this study, overcurrent protection technique is investigated for the voltage regulation problem of the DC–DC buck converter system with time-varying disturbances and uncertainties. Normally, fast dynamics during the start-up phase generates large transient current. The overlarge transient current may lead to risks of hardware damage. By selecting conservative control parameters, the current constrained performance can be realised. However, the transient performance and disturbance rejection ability are sacrificed. It is of significant importance to design a controller which keeps a good balance between dynamic performance and overcurrent protection. Moreover, the control accuracy is inevitable affected by the time-varying disturbances effects, including load variations, input voltage fluctuations and circuit parameter perturbations. In this paper, the control design is divided into two parts. Firstly, by inserting a dynamic penalty term into the state feedback controller, a baseline current-constrained scheme is developed. Rigorous stability analysis and current constraint performance are given under the presented baseline controller. Secondly, taking the time-varying disturbances into account, a novel GPI observer-based composite current-constrained controller can be developed by combining disturbance estimations and the baseline controller. Experimental results are provide to demonstrate the effectiveness of the presented control strategy.

A practical attitude control scheme for hypersonic vehicle based on disturbance observer

This paper proposes a practical three-channel attitude control scheme for hypersonic vehicle based on the linear active disturbance rejection control. The control scheme considers the weak and strong coupling scenarios separately due to the dynamic characteristics. For the weak coupling case, three linear active disturbance rejection controllers are designed for the Euler angles of the three channels, respectively, to deal with the strong uncertainties. The expected stability margin and dynamic performance can be guaranteed through the stability margin tester tuning method. Moreover, the control scheme for the pitch, yaw, and roll angles can be applied to the control of the angle of attack, the sideslip angle and the bank angle directly according to the flight dynamics of the hypersonic vehicle, thus realizing a unified control framework for all the attitude angles. For the strong coupling scenario like the fast reversal maneuver, the inner-loop angular rate feedback is performed first in this paper to enhance the damping characteristics, and then linear active disturbance rejection control is designed for the augmented plant to eliminate the strong coupling effects. Simulation results demonstrate the satisfactory tracking and disturbance rejection ability of the proposed methods.

Research on Power Transmission Capability of VSC-HVDC Based on Second Order LADRC

Voltage source converter based high voltage direct current (VSC-HVDC) technology is considered one of the most desirable technique for massive renewable power integration, for which converter controller design and power transmission capacity research are two essential topic. A novel VSC-HVDC converter station controller is proposed based on second order linear active disturbance rejection control (LADRC), which realizes rapid and independent adjustment of active and reactive power. The controller take full advantage of ADRC to improve dynamic response and to strengthen robustness as well as disturbance rejection ability of the system. A small signal model of overall system including AC system dynamics is established. Based on eigenvalue analysis, power transmission limit of VSC-VHDC is investigated on the perspective of global stability of the whole system. The influence of control strategy and reactive control mode on VSC power transmission capacity are then analyzed respectively. Examples are given to verify the results obtained by small signal stability analysis. The research in the paper provides theoretical support for the application of LADRC in VSC-HVDC domain.

Distributed Anti-Disturbance Control Strategy for Multi-Aircraft Systems With Time-Varying Topology

This paper is concerned with the distributed consensus problems for second-order multi-aircraft systems in the presence of sensor data loss and time-varying communication topology. A novel model-based game strategy is proposed to handle the distributed problem regardless of the time-varying topology. An anti-disturbance sliding-mode controller is designed to realize the ability of disturbance rejection and state estimation. The extended state observer combines two methods together and finally produces an independent decision-making architecture for each individual such that better convergence is achievable. Theoretical analyses are given to guarantee both individual stability and distributed stability. The simulation and experimental results are presented to show the effectiveness of the proposed control scheme.

Disturbance Observer-Based Adaptive Current Control With Self-Learning Ability to Improve the Grid-Injected Current for $LCL$ -Filtered Grid-Connected Inverter

During the design of the conventional current controller for a grid-connected inverter with LCL filter, the parameter mismatches and disturbances are generally neglected, which may seriously affect the control performance, even result in instability. In order to improve the ability of disturbance rejection and ensure a desired control performance, this paper proposes an Adaptive PID (APID) controller with the self-learning ability based on the Disturbance Observer (DOB). First, the full state-feedback and state observer are utilized to achieve active damping and eliminate the effect of computational delay. Then, aiming to estimate and compensate the lumped disturbance, a DOB is designed. Beneficial from DOB, the steady-state performance is almost not affected by model uncertainties and unmodeled dynamics, however, the transient performance is still deteriorated inevitably due to the limitation of DOB. Thus, an online adaptive method using APID is finally proposed to further improve grid-injected current dynamics. The control parameters can be automatically adjusted in real time by adaptive learning rule, which significantly improves the system robustness and the control performance. Simulation and experiments are provided to demonstrate the effectiveness of the proposed strategy.

Intelligent fractional-order backstepping control for an ironless linear synchronous motor with uncertain nonlinear dynamics

This study aims to develop an intelligent fractional-order backstepping controller to control the mover position of an ironless permanent magnet linear synchronous motor. First, we investigated the operating principle and dynamic modeling of the linear synchronous motor based on the field-oriented control method. Next, to improve the convergence speed and control accuracy of the conventional backstepping controller, we designed a fractional-order backstepping controller that has more degrees of freedom in the control parameters. However, designing the switching control gain is difficult owing to the unknown degree of uncertainty. To address this problem, we proposed an intelligent fractional-order backstepping controller to further enhance the adaptiveness and robustness of the fractional-order backstepping controller. In this intelligent controller, we proposed a Hermite-polynomial-based functional-link fuzzy neural network as an uncertainty estimator that can directly estimate system uncertainty, thereby improving the disturbance rejection ability and requiring no uncertainty bound information. Additionally, to compensate for the estimation error introduced by the estimator, we designed an exponential compensator that employs a smooth exponential self-regulation mechanism. We utilized the Lyapunov theorem to derive estimation laws for the online tuning of the control parameters. Experimental results demonstrate the effectiveness and high positioning performance of the proposed intelligent fractional-order backstepping controller in comparison with the backstepping controller and fractional-order backstepping controller in the linear synchronous motor control system.

A Sustainable Power Plant Control Strategy Based on Fuzzy Extended State Observer and Predictive Control

The control of an ultra-supercritical (USC) boiler–turbine power plant is critical in maintaining the safety of the sustainable power grid. However, it is challenging due to the internal nonlinearity, hard manipulation constraints, and widespread uncertainties. To this end, a fuzzy extended state observer (FESO)-based stable fuzzy predictive control (SFPC) approach is developed in this paper. First, the control difficulties of the USC boiler–turbine unit are analyzed. Then, based on a Takagi–Sugeno (T–S) fuzzy model, a new FESO is developed for nonlinear systems to achieve a more precise observation performance. The gain of FESO is determined by solving a series of linear matrix inequalities, while guaranteeing the stability of FESO. Then, by combining the proposed FESO with the SFPC, an integrated FESO–SFPC algorithm is devised. The disturbance rejection ability of the FESO–SFPC algorithm is analyzed theoretically. Simulation results on a 1000 MW USC boiler–turbine power plant model further validate the effectiveness of the proposed method.

Robust neuro-fuzzy sliding mode control with extended state observer for an electric drive system

The choice of the control techniques has a positive impact on the traction chain particularly disturbance rejection ability and the energy management in the electric vehicle (electric motor, inverter, transmission, ect.). In this paper, a robust neuro-fuzzy-sliding mode control (RNFSMC) with extended state observer (ESO) technique is applied on the traction chain of the electric vehicle (Permanent magnet synchronous motor PMSM, Inverter, Transmission). However, most of the existing strategies of control that are applied on the traction chain lead to chattering phenomena, reducing the electric motor performance and disturbance rejection ability without forgetting the bad energy management on board the electric vehicle. To further enhance the performance of the traction chain, a hybrid control scheme is used to severally decrease the chattering phenomena in the PMSM electric motor and evolve the disturbance rejection ability which employs two types of controllers: Neuro-fuzzy sliding mode control on the direct current loop and ESO controller on both speed, and quadrature current loops taking into account the dynamic of the vehicle. Simulations by Matlab/Simulink are used to indicate the validity of the planed scheme on the closed-loop system. The simulation results show the effectiveness of the proposed control strategy with desired tracking accuracy.

A PLL-free robust control scheme with application to grid-connected fuel cell DGs under balanced and unbalanced conditions

A robust control scheme for the power electronic converter interface of grid-connected fuel cell distributed generators is presented. The scheme enables them to operate under various limiting factors that can severely affect performance such as voltage sags, parametric uncertainties, unknown disturbances and noise. The control strategy adds low voltage ride-through ability to the grid-connected system without requiring a specialized phase locked loop that is often an integral part of the control systems used under unbalanced grid conditions, and therefore, simplifying its design and lowering its computational complexity. The dc-dc and dc-ac converters are controlled using two different controllers: the uncertainty and disturbance estimation controller for the dc-side voltage, and the repetitive controller for the grid-side currents. The control system is designed with the objectives of robustness, fast transient response, disturbance rejection and low voltage ride-through ability. A number of simulation case studies are presented using the SimPowerSystems™ toolbox of MATLAB/Simulink computing environment to highlight the performance of the proposed control scheme under both symmetrical and asymmetrical voltage sags,parametric uncertainties, and abrupt operating condition changes. The control system is also tested through digital implementation on a low-cost microcontroller to validate its performance.

A Novel Fuzzy Model Predictive Control of a Gas Turbine in the Combined Cycle Unit

The complex characteristics of the gas turbine in a combined cycle unit have brought great difficulties in its control process. Meanwhile, the increasing emphasis on the efficiency, safety, and cleanliness of the power generation process also makes it significantly important to put forward advanced control strategies to satisfy the desired control demands of the gas turbine system. Therefore, aiming at higher control performance of the gas turbine in the gas-steam combined cycle process, a novel fuzzy model predictive control (FMPC) strategy based on the fuzzy selection mechanism and simultaneous heat transfer search (SHTS) algorithm is presented in this paper. The objective function of rolling optimization in this novel FMPC consists of two parts which represent the state optimization and output optimization. In the weight coefficient selection of those two parts, the fuzzy selection mechanism is introduced to overcome the uncertainties existing in the system. Furthermore, on account of the rapidity of the control process, the SHTS algorithm is used to solve the optimization problem rather than the traditional quadratic programming method. The validity of the proposed method is confirmed through simulation experiments of the gas turbine in a combined power plant. The simulation results demonstrate the remarkable superiorities of the adopted algorithm with higher control precision and stronger disturbance rejection ability as well as less optimization time.

Performance enhancement using durational model predictive control combined with backstepping control and disturbance observer for electrical drives

Model predictive control (MPC) is widely used in a cascaded structure for electrical drives, in which, the MPC is applied as inner-loop for current regulating while another controller such as proportional–integral (PI) is applied as outer-loop for speed regulating. However, the benefits of MPC for multiple targets optimizing simultaneously are not sufficiently utilized. Moreover, characteristics of these drives rely on the outer-loop controller due to the cascaded strategy, and they are parameter-sensitive. A durational MPC is proposed in this paper to optimize the speed and currents of permanent-magnet synchronous machine (PMSM) simultaneously, and it is combined with backstepping control (BSC) and disturbance observer to improve the disturbance rejection ability and parameter robustness. The nonlinear characteristics of drives are considered, and the voltage reference is constructed by combining the optimal voltage vector and virtual voltage target produced by MPC and BSC, respectively. The proposed method takes advantages of both MPC and BSC and thus provides significant performance enhancement compared with the conventional PI-base cascaded MPC. Simulation and experiment for the PMSM drives with the proposed method are conducted to prove its stability, feasibility, and efficiency.

Dual-axis control of flexure-based motion system for optical fibre transceiver assembly using fixed-order controller

High-frequency resonant modes appearing in the flexure-based motion systems are the key factors that limit the motion/positioning performance. This paper presents an approach to design the fixed-order (low-order) controller for the flexure-based motion system, which is used for industrial optical fibre transceiver alignment and assembly. The uniqueness of the proposed algorithm is that one single controller can simultaneously stabilize the uncertain high-frequency resonant modes for both x and y-axis motion. Especially, the resulted controller can significantly enhance the tracking and disturbance rejection ability in low frequency. The novelty of the proposed method is mainly twofold. First, the finite-frequency specifications are introduced to robust control of the polytopic systems. As the entire-frequency specifications have the trend to place the dominant poles towards the central polynomial, the finite-frequency specifications largely relax the conservatism for the performance optimization. Second, a new and practical method is proposed to choose the central polynomial by designing a nominal controller, where two different central polynomials are utilized for x and y-axis separately for the practical applications, so that the stability and performance are guaranteed but the conservatism is reduced. Experiments are evaluated on the 2DOF flexure-based motion system, and the results show that the tracking error using designed fixed-order controller has a more than 50% reduction compared with the same-order notch filter based nominal controller, with respect to both the sinusoidal and triangular references.

Design and implementation of continuous finite-time sliding mode control for 2-DOF inertially stabilized platform subject to multiple disturbances

Control performances of inertially stabilized platforms (ISPs) are always affected by various disturbed phenomena such as cross-couplings, mass unbalance, parameter variations, and external disturbances in real applications. To improve the dynamic response and the disturbance rejection ability of the ISP, a continuous finite-time sliding mode control (SMC) approach with cascaded control structure is proposed. By constructing a finite-time disturbance observer, the multiple disturbances are precisely estimated in real time without the complex modeling and calibration work. Under the field oriented control framework, for the stabilized loop subsystem, an improved super-twisting controller incorporating the disturbance estimates is developed whereas for the current loop subsystem, the super-twisting control method is directly employed. Finite-time convergence of the inertial angular rates is guaranteed with the continuous control action such that chattering is alleviated remarkably. Moreover, by utilizing the manner of disturbance compensation, the feedback control gains can be tuning down without sacrificing the disturbance rejection ability. Comparative experiments are performed to verify the effectiveness of the proposed control approach.

Research on Active Disturbance Rejection Control Technology of Electromechanical Actuators

It has been proven that the properties of non-linearity, multi-disturbance, and time-variation are the main factors affecting the performance of the electromechanical actuator (EMA) for guided artillery rockets. In particular, its controller should have good dynamic characteristics and strong anti-disturbance features when the projectile is maneuvered at the end of its guidance. For these reasons, an active disturbance rejection controller (ADRC) was designed for a guided artillery rocket’s EMA with a ball screw drive. Compared to other control methods, it has been shown that the ADRC had a stronger disturbance rejection ability than PID, Fuzzy-PID, and BP-PID under the condition of 20% maximum control torque disturbance, and it also had a large stability margin and bandwidth.