Integral sliding-mode control of a magnetically suspended balancebeam: analysis, simulation, and experiment

This paper presents a sliding-mode controller with integral compensation for a magnetic suspension balance beam system. The control scheme comprises an integral controller which is designed for achieving zero steady-state error under step disturbances, and a sliding-mode controller which is designed for enhancing robustness under plant uncertainties. A procedure is developed for determining the coefficients of the switching plane such that the overall closed-loop system has stable eigenvalues. A proper continuous design signal is introduced to overcome the chattering problem. The performance of the balance beam control system is illustrated by simulation and experimental results showing that the proposed integral sliding-mode controller method is effective under external step disturbances and input channel parameter variations     

Robust and fault-tolerant linear parameter-varying control of wind turbines

High performance and reliability are required for wind turbines to be competitive within the energy market. To capture their nonlinear behavior, wind turbines are often modeled using parameter-varying models. In this paper we design and compare multiple linear parameter-varying (LPV) controllers, designed using a proposed method that allows the inclusion of both faults and uncertainties in the LPV controller design. We specifically consider a 4.8 MW, variable-speed, variable-pitch wind turbine model with a fault in the pitch system.We propose the design of a nominal controller (NC), handling the parameter variations along the nominal operating trajectory caused by nonlinear aerodynamics. To accommodate the fault in the pitch system, an active fault-tolerant controller (AFTC) and a passive fault-tolerant controller (PFTC) are designed. In addition to the nominal LPV controller, we also propose a robust controller (RC). This controller is able to take into account model uncertainties in the aerodynamic model.The controllers are based on output feedback and are scheduled on an estimated wind speed to manage the parameter-varying nature of the model. Furthermore, the AFTC relies on information from a fault diagnosis system.The optimization problems involved in designing the PFTC and RC are based on solving bilinear matrix inequalities (BMIs) instead of linear matrix inequalities (LMIs) due to unmeasured parameter variations. Consequently, they are more difficult to solve. The paper presents a procedure, where the BMIs are rewritten into two necessary LMI conditions, which are solved using a two-step procedure.Simulation results show the performance of the LPV controllers to be superior to that of a reference controller designed based on classical principles.     

A Globally Stable High-Performance Adaptive Robust Control Algorithm With Input Saturation for Precision Motion Control of Linear Motor Drive Systems

This paper focuses on the synthesis of nonlinear adaptive robust controller with saturated actuator authority for a linear motor drive system, which is subject to parametric uncertainties and uncertain nonlinearities such as input disturbances as well. Global stability with limited control efforts is achieved by breaking down the overall uncertainties to state-linearly-dependent uncertainties (such as viscous friction) and bounded nonlinearities (such as Coulomb friction, cogging force, etc.), and dealing with them via different strategies. Furthermore, a guaranteed transient performance and final tracking accuracy can be obtained by incorporating the well-developed adaptive robust control strategy and effective parameter identifier. Asymptotic output tracking is also achieved in the presence of parametric uncertainties only. Meanwhile, in contrast to the existing saturated control structures that are designed based on a set of transformed coordinates, the proposed saturated controller is carried out in the actual system states, which have clear physical meanings. This makes it much easier and less conservative to select the design parameters to meet the dual objective of achieving global stability with limited control efforts for rare emergency cases and the local high-bandwidth control for high performance under normal running conditions. Real-time experimental results are obtained to illustrate the effectiveness of the proposed saturated adaptive robust control strategy     

基于直驱型PMSG风力发电系统的变桨自抗扰控制

为了实现大功率风力发电系统的恒功率控制,首先建立了基于直驱型PMSG风力发电系统的数学模型;其次,以功率偏差为控制器的输入信号,设计了一种基于自抗扰算法的风力发电系统变桨距控制器。最后,在阵风叠加随机风的作用下进行仿真研究。仿真结果表明,该控制器能够有效地控制桨距角,可以实现额定风速以上时系统输出功率的恒定。     

机电系统自适应控制仿真

针对机电伺服系统中存在的不确定因素和多余力扰动问题,提出一种自适应比例－积分－微分(PID)控制策略。该自适应控制器由最优PID控制器和小脑模型关节控制器(CMAC)组成,最优PID控制器用来整定系统的标称模型,CMAC控制器用来克服系统中含有的不确定项和多余力扰动,自适应PID控制器能确保系统跟踪误差和CMAC权值误差收敛到零。仿真结果表明,本文提出的控制器具有令人满意的跟踪性能,对系统中的不确定因素和多余力扰动具有一定的鲁棒性。     

Nonlinear adaptive control of direct-drive brushless DC motors andapplications to robotic manipulators

Robust adaptive nonlinear control of brushless DC (BLDC) motors is considered. A controller is designed for the plant that is robust to parametric and dynamic uncertainties in the entire electromechanical system. These uncertainties are shown to be bounded by polynomials in the states. In addition, the controller can reject any bounded unmeasurable disturbances entering the system. A model for the motor incorporating magnetic saturation is used to design voltage-level control inputs for the motor. The design methodology is based on our earlier work on adaptive control of nonlinear systems. The overall stability of the system is shown using Lyapunov techniques. The tracking error is shown to be globally uniformly bounded. The design procedure is shown to be also applicable to multilink manipulators actuated by BLDC motors. The performance of the controller is verified through simulations and comparisons with a proportional-integral-derivative-type controller are made     

Robust controller design for PTP motion of vertical XY positioning systems with a flexible beam

This paper presents a point-to-point (PTP) motion control method for accurate positioning and vibration suppression of a vertical XY positioning system with a flexible beam. The proposed method is composed of a feedforward and feedback controller. The input preshaping based on the analytic modeling and frequency equation of the system is proposed as a feedforward controller to produce the desired responses. The feedback controller based on a robust internal-loop compensator is designed to meet the specified performance and to stabilize the whole system in the presence of uncertainties and disturbances. By integrating the input preshaping controller and feedback controller, it is shown that the system is stable and the vibration of the flexible beam is suppressed. The proposed algorithm is demonstrated experimentally on an XY positioning system which consists of a base cart, elastic beam and moving mass.     

New hybrid controller for systems with deterministic uncertainties

In this paper, a new hybrid controller for systems with deterministic uncertainties is developed. The proposed controller identifies and compensates deterministic uncertainties simultaneously. It is the combination of a time-domain feedback controller and a frequency-domain iterative learning controller. The feedback controller decreases system variability and reduces the effect of random disturbances. The iterative learning controller shapes the system input to suppress the error caused by deterministic uncertainties such as friction and backlash. The control scheme use only local input and output information, no system model is required. The uncertainties can be structured or unstructured. The effectiveness of the proposed controller is experimentally verified on a servo system with gearbox     

Adaptive robust pressure control of variable displacement axial piston pumps with a modified reduced-order dynamic model

Variable displacement axial piston pumps (VDAPPs) are wildly used in mobile working machines and they play a key role in machine’s energy-saving load sensing (LS) systems. Typically, electric load sensing (ELS) systems utilize traditional linear control methods, which only can realize limited control flexibility and performance. This study proposes and experimentally verifies an adaptive robust pressure control strategy for a VDAPP system. To facilitate the model-based controller design, a modified reduced-order dynamic modeling of VDAPPs is proposed. Furthermore, an adaptive robust backstepping control strategy is designed to deal with the dynamic nonlinearities and parametric uncertainties of the VDAPP system for achieving accurate pressure tracking. The controller design consists of two steps, processing the pump pressure tracking and the axial angle control, respectively. Comparative experiments and simulations with different working conditions were performed to validate the advantages of the proposed control strategy. The proposed controller achieved higher pressure tracking accuracy and it showed great capability in dealing with dynamic nonlinearities, uncertainties, and time-varying disturbances.     

Adaptive integral robust control of hydraulic systems with asymptotic tracking

In this paper, an adaptive integral robust controller is developed for high accuracy motion tracking control of a double-rod hydraulic actuator. We take unknown constant parameters including the load and hydraulic parameters, and lumped unmodeled disturbances in inertia load dynamics and pressure dynamics into consideration. A discontinuous projection-based adaptive control law is constructed to handle parametric uncertainties, and an integral of the sign of the extended error based robust feedback term to attenuate unmodeled disturbances. Moreover, the present controller does not require a priori knowledge on the bounds of the lumped disturbances and the gain of the designed robust control law can be tuned itself. The major feature of the proposed full state controller is that it can theoretically guarantee global asymptotic tracking performance with a continuous control input, in the presence of various parametric uncertainties and unmodeled disturbances such as unmodeled dynamics as well as external disturbances via Lyapunov analysis. Comparative experimental results are obtained for motion control of a double-rod hydraulic actuator and verify the high-performance nature of the proposed control strategy.     

Model reference adaptive control of a soft bending actuator with input constraints and parametric uncertainties

In this article, model reference adaptive control of a pneumatically actuated soft robot has been studied in detail. To deal with the effects of system uncertainties, in the proposed control scheme, parametric uncertainties and input constraints are taken into account. To design such a controller, based on experimental analysis, the robot has been modeled as a second-order Linear Parameter Varying (LPV) system. Then, the dominant dynamics are presented as a Linear Time-Invariant (LTI) system, while uni-directional input constraint has been considered as a critical issue in the control scheme design. Furthermore, to compensate parametric uncertainties as well as unmodeled dynamics, adaptive laws are modified. Finally, the effectiveness is studied in different scenarios on an experimental platform to validate our claims. Moreover, to show the proposed approach capabilities and performance, the proposed controller has been compared with a PID and a recent sophisticated robust-adaptive controller, which presented a new formulation to achieve a better tracking performance with guaranteed stability in the presence of different constraints and unmodeled dynamics.     

Adaptive gain scheduling with feedforward control system based on system model for PMSM

A feedforward controller for permanent magnet synchronous motor (PMSM) has been proposed in this study, and proportional and integral gain could be self-adaptive under different operating conditions. The control structure used in the feedforward system is the same as in the feedback control system. This control structure could guarantee independence of the speed command input to output with the disturbance input to output, which makes the system have better reference trajectory tracking and disturbances rejection. In order to obtain optimal control performance when the parameters are uncertain, a gain scheduling adaptive controller is used in the feedforward system. The proposed controller has been verified by the experimental and simulation results with less steady-state error and better dynamic response than the controllers without it under the condition of external load torque disturbance and PMSM parameter uncertainties.     

Adaptive Fuzzy Control of Nonlinear in Parameters Uncertain Chaotic Systems Using Improved Speed Gradient Method

This paper presents an adaptive fuzzy controller for Nonlinear in Parameters (NLP) chaotic systems with parametric uncertainties. In the proposed controller, the unknown parameters are estimated by the novel Improved Speed Gradient (ISG) method, which is a modification of Speed Gradient (SG) algorithm. ISG employs the Lagrangian of two suitable objective functionals for on-line estimation of system parameters. The most significant advantage of ISG is that it is applicable to NLP systems and it results in a faster rate of convergence for the estimated parameters than the SG method. Estimated parameters are used to design the fuzzy controller and to calculate the Lyapunov exponents of the chaotic system adaptively. Furthermore, established on the well-known Takagi–Sugeno (T-S) fuzzy model, a LMI (Linear Matrix Inequality)-based fuzzy controller is designed and is tuned using estimated parameters and Lyapunov exponents. Throughout the controller design procedure, several important issues in fuzzy control theory including relaxed stability analysis, control input performance specifications, and optimality are taken into account. Combination of ISG parameter estimation method and T-S-based fuzzy controller yields an adaptive fuzzy controller capable to suppress uncertainties in parameters and initial states of NLP chaotic systems. Finally, simulation results are provided to show the effectiveness of the ISG and adaptive fuzzy controller on chaotic Lorenz system and Duffing oscillator.     

Robust control of the DC–DC boost converter based on the uncertainty and disturbance estimator

In this paper, a robust non-linear controller based on the uncertainty and disturbance estimator (UDE) scheme is successfully developed and implemented for the output voltage regulation of the DC–DC boost converter. System uncertainties, external disturbances and unknown non-linear dynamics are lumped as a signal that is accurately estimated using a low-pass filter and their effects are cancelled by the controller. This methodology forms the basis of the UDE-based controller. A simple procedure is also developed that systematically determines the parameters of the controller to meet certain specifications. Using simulation, the effectiveness of the proposed controller is compared against the sliding-mode control (SMC). Experimental tests also show that the proposed controller is robust to system uncertainties, large input and load perturbations.     

位置和艏向角约束的非对角欠驱动USV轨迹跟踪

仅配备有纵向推进力和转船力矩装置的无人水面艇是典型的欠驱动系统,不能通过定常光滑反馈控制律镇定到平衡状态。本文针对一类惯性矩阵和阻尼矩阵非对角的欠驱动无人水面艇,设计了基于附加控制器和反步法的光滑时变跟踪控制律,在保证跟踪误差暂态性能的前提下,实现了曲线和直线情形下的轨迹跟踪。首先,通过状态变换将非对角模型转化为对角形式,并运用反馈线性化理论简化控制输入。其次,通过设计虚拟控制函数来镇定误差运动学方程,并通过引入障碍Lyapunov函数(BLF)来保证跟踪误差满足规定的性能。然后,通过在误差镇定函数中引入虚拟控制量解决了系统的欠驱动问题,稳定性分析表明本文控制策略能够保证闭环系统中的所有状态是一致最终有界的。最后,Matlab/Simulink仿真结果表明了该控制器的有效性。     

Vehicle Yaw Control via Second-Order Sliding-Mode Technique

The problem of vehicle yaw control is addressed in this paper using an active differential and yaw rate feedback. A reference generator, designed to improve vehicle handling, provides the desired yaw rate value to be achieved by the closed loop controller. The latter is designed using the second-order sliding mode (SOSM) methodology to guarantee robust stability in front of disturbances and model uncertainties, which are typical of the automotive context. A feedforward control contribution is also employed to enhance the transient system response. The control derivative is constructed as a discontinuous signal, attaining an SOSM on a suitably selected sliding manifold. Thus, the actual control input results in being continuous, as it is needed in the considered context. Simulations performed using a realistic nonlinear model of the considered vehicle show the effectiveness of the proposed approach.      

Automatic disturbances rejection controller for precise motion control of permanent-magnet synchronous motors

A highly robust automatic disturbances rejection controller (ADRC) is developed to implement high-precision motion control of permanent-magnet synchronous motors. The proposed ADRC consists of a tracking differentiator (TD) in the feedforward path, an extended state observer (ESO), and a nonlinear proportional derivative control in the feedback path. The TD solves the difficulties posed by low-order reference trajectories which are quantized at the sensor resolution, and the ESO provides the estimate of the unmeasured system's state and the real action of the unknown disturbances only based on a measurement output of the system. Simulations and experimental results show that the proposed ADRC achieves a better position response and is robust to parameter variation and load disturbance. Furthermore, the ADRC is designed directly in discrete time with a simple structure and fast computation, which make it widely applicable to all other types of derives.     

柔性交流输电系统技术在现代配电网的应用展望

本文以统一潮流控制器为例,说明了柔性交流输电技术在含有风力发电的现代配电系统中的应用前景。针对风力发电对电力系统影响的特点,指出了传统统一潮流控制器的不足,提出了将与风电配合的储能装置与统一潮流控制器相结合的拓扑原理结构,指出了基于切换系统原理的混杂PCH控制理论将有望解决底层为离散开关控制的柔性交流输电装置、上层为连...     

Innovative adaptive pitch control for small wind turbine fatigue load reduction

As a renewable source of energy, wind is widely used to produce electrical power. The progress of wind turbine technology can greatly benefit from the improvement of control algorithms. The pitch angle control of a horizontal axis wind turbine above the rated wind speed is a challenging issue related to the nonlinear aerodynamic behavior of blades. The linearization of aerodynamic model around nominal operating condition, as well as manufacturing deficiencies, result in unknown parameter uncertainties in a wind turbine model. Therefore, the performance of controller, which is designed based on the mathematical model, defects in practice. In the current paper, an adaptive self-tuning regulator (STR) configuration is proposed for the pitch control, so that the parameters of wind turbine model are constantly estimated and the controller gains are updated based on the assessed parameters. The STR structure consists of a recursive least square estimator and a proportional-integral-derivative (PID) controller with adjustable gains, which are determined by the pole placement method in a real-time routine. The robustness of the closed loop system is investigated by implementation of the control structure on an aero-servo-elastic wind turbine simulator. For the sake of comparison, a baseline gain scheduling PID controller, which is well-accepted for wind turbine pitch control, is designed. A comparison between the simulations of two controllers confirms a significant improvement in the closed-loop performance including less fluctuation of rotor speed and power besides minor fatigue loads on the blades and main-shaft.     

A Hybrid-Type Variable-Structure Instantaneous Torque Control With a Robust Adaptive Torque Observer for a High-Performance Direct-Drive PMSM

This paper describes a novel instantaneous torque control scheme for a high-performance direct-drive permanent-magnet synchronous motor. The scheme consists of a robust adaptive instantaneous torque observer and a hybrid-type variable-structure instantaneous torque controller. First, to robustly obtain the instantaneous electromagnetic torque information, a robust adaptive torque observer is designed by considering all possible current model uncertainties. The observation gains and uncertainties prediction rules are derived in the sense of Lyapunov theory so that the stability of the proposed estimation scheme is fulfilled. Second, to ensure perfect tracking of the output torque and providing means in eliminating torque ripples, the frequency modes of the disturbances to be eliminated should be included in the stable closed-loop system. To achieve this objective, a hybrid-type variable-structure controller with internal model, for the flux harmonics and system uncertainties, is adopted. The hybrid controller shows better disturbance rejection without control chattering. Comparative evaluation results are presented to demonstrate the validity and effectiveness of the proposed instantaneous torque control scheme.