舵机加载系统的最优控制

分析了舵机加载系统的结构原理,建立其简化模型,并研究了最优控制在舵机加载系统中的应用.舵机加载系统中加载设备和舵机系统间存在强烈的耦合,针对舵机运动对加载系统跟踪性能的影响,应用前馈控制对舵机运动扰动进行补偿.为进一步提高系统性能,引入最优控制.根据舵机加载系统的特点,比较研究了3种不同的最优控制方法.常用的是工程近似最优控制方法,为进一步消除稳态误差,可以引入积分控制.与上述方法不同,对加载系统进行最优控制时,采用积分策略增广系统状态方程,并引入期望衰减度定义性能指标构造系统的最优控制.仿真结果表明,在文中所构造的最优控制和前馈控制的复合控制下,加载系统具有相对最佳的跟踪性能.     

Extended state observer-based time-optimal control for fast and precise point-to-point motions driven by a novel electromagnetic linear actuator

An extended state observer-based time-optimal control is proposed in this paper to achieve fast and precise point-to-point motions driven by a novel electromagnetic linear actuator. Working principle and characteristics of the actuator are analyzed. Total disturbance is estimated by an extended state observer, and the nonlinear system is compensated as a linear one. Time-optimal control is used to realize accurate point-to-point motions with minimal time. Comparative simulations and experimental results demonstrate the effectiveness of the proposed method, especially for non-repetitive point-to-point motions, and good positioning performance has been achieved in the presence of both model uncertainties and external 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.     

A sliding mode torque and position controller for an antagonistic SMA actuator

This paper presents position and torque control of an antagonistic setup for a shape memory alloy (SMA) rotary actuator using a sliding mode controller that takes into account the nonlinear behavior of SMA. The control scheme and model are based on the complete physics model of the system. An accurate model of the actuator is presented and validated by means of an experimental prototype. A nonlinear state observer is also developed in order to estimate temperature and phase state variables that are difficult to measure online due to the small dimensions of the actuator. Experimental results are then presented for different set-point functions. Tracking performance, frequency response and disturbance rejection are evaluated and the advantages of the proposed controller are then discussed.     

陀螺稳定平台速度环的离散自抗扰控制

针对陀螺稳定平台在高精度定位下的控制精度受到速度环电机在低速运动时非线性摩擦力影响的问题,文章设计了一种改进策略的自抗扰控制器,将原系统中的非线性摩擦力与电机不同转向时的模型误差统一视为系统扰动,采用扩张状态观测器对这个扰动进行估计,前馈到控制量中进行校正。理论分析了一阶离散系统上扩张状态观测器的推导过程和稳定性条件,并采用遗传算法工具箱对针对平台所设计的扩张状态观测器的参数进行辨识。在仿真实验中,我们首先分析了所设计的扩张状态观测器的开环性能,然后将所设计的自抗扰控制器与实际系统采用的PI控制器的控制精度进行了对比分析。文章为进一步提高陀螺稳定平台的控制性能,提供了一种新的高精度的控制策略。     

Investigation of Sliding-Surface Design on the Performance of Sliding Mode Controller in Antilock Braking Systems

Sliding mode control (SMC) has widely been employed in the development of a wheel-slip controller because of its effectiveness in applications for nonlinear systems as well as its performance robustness on parametric and modeling uncertainties. The design of a sliding surface strongly influences the overall behavior of the SMC system due to the discontinuous switching of control force in the vicinity of a sliding surface that produces chattering. This paper investigates the effects of sliding-surface design on the performance of an SMC-based antilock braking system (ABS), including a brake-torque limitation, an actuator time delay, and a tire-force buildup. Different sliding-surface designs commonly used in ABS were compared, and an alternative sliding-surface design that improves convergence speed and oscillation damping around the target slip has been proposed. An 8-degree-of-freedom (dof) nonlinear vehicle model was developed for this paper, and the effects of brake-system parameter variations, such as a brake actuator time constant, target slip ratios, an abrupt road friction change, and road friction noises, were also assessed.     

PID-type sliding mode-based adaptive motion control of a 2-DOF piezoelectric ultrasonic motor driven stage

This paper presents a new scheme of adaptive sliding mode control (ASMC) for a piezoelectric ultrasonic motor driven X–Y stage to meet the demand of precision motion tracking while addressing the problems of unknown nonlinear friction and model uncertainties. The system model with Coulomb friction and unilateral coupling effect is first investigated. Then the controller is designed with adaptive laws synthesized to obtain the unknown model parameters for handling parametric uncertainties and offsetting friction force. The robust control term acts as a high gain feedback control to make the output track the desired trajectory fast for guaranteed robust performance. Based on a PID-type sliding mode, the control scheme has a simple structure to be implemented and the control parameters can be easily tuned. Theoretical stability analysis of the proposed novel ASMC is accomplished using a Lyapunov framework. Furthermore, the proposed control scheme is applied to an X–Y stage and the results prove that the proposed control method is effective in achieving excellent tracking performance.     

Vision-based optimization of the generalized predictive active disturbance rejection controller

The batching system of the integrated mixing and spreading equipment for MOH material is a nonlinear system with large uncertainty. It is difficult for conventional control strategies to meet the requirements for system performance. This research combines generalized predictive control and active disturbance rejection technique to propose a new generalized predictive active disturbance rejection controller (GPADRC) used in the batching system of MOH material. For the nonlinearity and uncertainty of the batching system, the extended state observer in the active disturbance rejection technique is used for estimation and compensation. The batching system model is converted into an integrator form, based on which the use of generalized predictive control can greatly reduce the impact of nonlinear models and uncertainties on the controller. Aiming at the problem that the parameters of the proposed new controller are numerous and difficult to tune, the adaptive genetic algorithm is used to realize the automatic tuning of the parameters. The simulation experiment shows that the designed GPADRC can well adapt to the working conditions of the batching system and can meet the requirements for various control indicators. At the same time, the adaptive genetic algorithm can realize the rapid tuning of the controller parameters, which reduce the difficulty and time consumption of the tuning process, and improve the applicability and achievability of the designed controller.     

Piecewise affine modeling and compensation in motion of linear ultrasonic actuators

Ultrasonic actuators used in high-precision mechatronics possess strong frictional effects, which are among the main problems in precision motion control. Traditional methods apply model-based nonlinear feedforward to compensate the friction, thus requiring closed loop stability and safety constraint considerations. In this article, model-based parametric controllers are developed to obtain an optimal positioning control for these motors. A systematic approach which uses piecewise affine models greatly simplifies the friction model compared to the traditional methods. Issues about the nonlinear effects of the friction are addressed by designing a robust control law near zero speed. These developments result in a gain-scheduling optimal input, which is simple to carry out in real-time applications. The controller is expected to improve the safety constraints and the tracking performance for actuator operation.     

Neural Network Based Adaptive Tracking of Nonlinear Multi-Agent System

In this paper, the problems of robust consensus tracking control for the second-order multi-agent system with uncertain model parameters and nonlinear disturbances are considered. An adaptive control strategy is proposed to smooth the agent’s trajectory, and the neural network is constructed to estimate the system’s unknown components. The consensus conditions are demonstrated for tracking a leader with nonlinear dynamics under an adaptive control algorithm in the absence of model uncertainties. Then, the results are extended to the system with unknown time-varying disturbances by applying the neural network estimation to compensating for the uncertain parts of the agents’ models. Update laws are designed based on the Lyapunov function terms to ensure the effectiveness of robust control. Finally, the theoretical results are verified by numerical simulations, and a comparative experiment is conducted, showing that the trajectories generated by the proposed method exhibit less oscillation and converge faster.     

机载激光通信的重复自抗扰视轴稳定控制

机载激光通信的视轴稳定是建立激光通信链路的前提。针对通信终端载体的非线性扰动和扰动模型未知造成视轴稳态误差较大的问题,结合自抗扰控制与重复控制,提出了重复控制补偿自抗扰算法,以完全消除周期性稳态跟踪误差。仿真实验结果表明,与自适应PID控制方法相比,重复控制补偿自抗扰算法可以有效抑制平台的非线性扰动,提高了系统的稳态精度,并且具有较快的响应速度与较强的鲁棒性。     

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     

一类不确定非线性系统变结构自适应鲁棒控制

本文针对一类不确定非线性系统,在假设系统模型参数和不确定性界都未知的情况下,提出了一个变结构自适应鲁棒控制算法,该算法在确保闭环系统稳定的前提下,在线对系统模型参数和不确定性界进行估计.最后以船舶减摇鳍非线性控制系统为例,进行了变结构鲁棒自适应控制器的设计,经仿真研究表明,所提出的算法是有效的.     

Force control for hydraulic load simulator using self-tuning grey predictor – fuzzy PID

Hydraulic systems play an important role in modern industry for the reason that hydraulic actuator systems have many advantages over other technologies with electric motors, as they possess high durability and the ability to produce large forces at high speeds. Therefore, the hydraulic actuator has a wide range of application fields such as hydraulic punching, riveting, pressing machines, and molding technology, where controlled forces or pressures with high accuracy and fast response are the most significant demands. Consequently, many hybrid actuator models have been developed for studying how to control forces or pressures with best results.This paper presents a kind of hydraulic load simulator for conducting performance and stability testing related to the force control problem of hydraulic hybrid systems. In the dynamic loading process, perturbation decreases control performance such as stability, frequency response, and loading sensitivity decreasing or bad. In order to improve the control quality of the loading system while eliminating or reducing the disturbance, a grey prediction model combined with a fuzzy PID controller is suggested. Furthermore, fuzzy controllers and a tuning algorithm are used to change the grey step size in order to improve the control quality. The grey prediction compensator can improve the system settle time and overshoot problems. Simulations and experiments on the hydraulic load simulator are carried out to evaluate the effectiveness of the proposed control method when applied to hydraulic systems with various external disturbances encountered in real working conditions.     

压电柔性结构形状复合控制方法研究

以宏纤维复合材料(MFC)驱动柔性悬臂结构为研究对象,着重开展其动态形状控制理论研究。基于有限单元法、均匀化理论和载荷比拟方法,建立了压电驱动层合结构力 电耦合动力学方程,并结合模态降阶法得到其状态空间形式控制模型。同时,针对压电材料作动器迟滞蠕变非线性特征对控制精度影响严重的问题,开展了依据实验数据的迟滞蠕变建模及其前馈逆补偿控制方法的研究,并构建了面向压电驱动柔性结构动态形状控制的迟滞 蠕变前馈补偿与自抗扰反馈控制相结合的复合控制系统。结果表明,该复合控制法能够在保证系统稳定性的前提下有效提高系统动态形状控制精度。     

Gearshift control system development for direct-drive automated manual transmission based on a novel electromagnetic actuator

A novel gearshift system which comprises a 2 degree-of-freedom electromagnetic actuator is introduced to simplify the structure of gearshift system of automated manual transmission (AMT), increase transmission efficiency and improve shift quality. The working principle and characteristics of the actuator are analyzed. The gearshift process is divided into the non-synchronization and the synchronization phase. Extended state observer (ESO) based inverse system method (ISM) and active disturbance rejection controller (ADRC) are designed for the two processes respectively. ISM can eliminate the nonlinearity of the actuator and ESO can estimate and compensate the uncertainties, parameter variations and external disturbances. ADRC is adopted to improve the tracking accuracy of the synchronization process. Comparative simulations and experimental results demonstrate the effectiveness of the proposed control method, and good gearshift performance has been achieved. Combined with the new designed control strategy, the novel gearshift system provides a new solution for AMT applications.     

Adaptive robust motion control of linear motors for precision manufacturing

Linear motors offer several advantages over their rotary counterparts in many precision manufacturing applications requiring linear motion; linear motors can achieve a much higher speed and have the potential of gaining a higher load positioning accuracy due to the elimination of mechanical transmission mechanisms. However, these advantages are obtained at the expense of added difficulties in controlling such a system. Specifically, linear motors are more sensitive to disturbances and parameter variations. Furthermore, certain types of linear motors such as the iron core are subject to significant nonlinear effects due to periodic cogging force and force ripple. To address all these issues, the recently proposed adaptive robust control (ARC) strategy is applied and a discontinuous projection-based ARC controller is constructed. In particular, based on the special structures of various periodic nonlinear forces, design models consisting of known basis functions with unknown weights are used to approximate those unknown nonlinear forces. On-line parameter adaptation is then utilized to reduce the effect of various parametric uncertainties such as unknown weights, inertia, and motor parameters while certain robust control laws are used to handle the uncompensated uncertain nonlinearities effectively for high performance. The resulting ARC controller achieves a guaranteed transient performance and a guaranteed final tracking accuracy in the presence of both parametric uncertainties and uncertain nonlinearities. In addition, in the presence of parametric uncertainties, the controller achieves asymptotic output tracking. Extensive simulation results are shown to illustrate the effectiveness of the proposed algorithm.     

Position control of an electro-hydrostatic asymmetric actuator operating in all quadrants

Pump-controlled actuators generally use single-rod cylinders in order to provide high output forces and reduce the installation space. According to the working principle of such systems, there are four possible circuit configurations, corresponding to four operational quadrants. This paper presents the design and experimental validation of a robust, fixed-gain, linear position controller for a newly developed single-rod pump-controlled actuator, i.e., electro-hydrostatic actuator (EHA) that operates in all quadrants. The actuator operates under different loading, being subjected to an alternating resistive-assistive load force. The controller has been built upon the quantitative feedback theory (QFT), and is designed to satisfy tracking, stability and disturbance rejection specifications, considering a wide range of parametric uncertainties. The ability of the proposed controller to maintain the actuator position within acceptable response envelopes, has been examined with the aid of an instrumented John Deere JD-48 backhoe. The experimental results show that oscillations in position responses are not observed during quadrant switch up to a load mass of 367 kg.     

Precise angular speed control of permanent magnet DC motors in presence of high modeling uncertainties via sliding mode observer-based model reference adaptive algorithm

The major concentration of this study is on developing a control scheme with parameter- and load-insensitive features capable of precise angular speed regulation of a permanent magnet (PM) DC motor in the presence of modeling uncertainties. Towards this objective, first, an appropriate nonlinear dynamic model of friction, the modified LuGre model, is opted and incorporated into the mathematical model of a PM DC motor. Then a sliding mode observer (SMO) is designed to estimate the state variable of the friction model. Next, a model reference adaptive control system into which estimated values of the friction state and parameters are fed is designed to track the desired speed trajectory while alleviating the adverse effects of model uncertainties and friction. Stability of the proposed SMO-based MRAC system is discussed via the Lyapunov stability theorem, and its asymptotic stability is verified. In addition to simulation studies, the algorithm is implemented on a new variable structure test-bed which gives us the ability to simulate desired parameter variations and external disturbance changes in experiment. The main contribution of the proposed scheme is the bounded estimation of the system’s friction parameter. While similar control solutions do estimate these parameters, there is no guarantee that they will estimate the correct value of friction parameters. However, in the proposed method, by properly choosing the design parameters, if certain criteria is satisfied, the estimated friction parameters will be in the bounded vicinity of their actual values. The obtained results show the effectiveness of the proposed tracking algorithm and its robustness against load and system parameters’ variations.