Integral controller design based on disturbance cancellation: Partial LTR approach for non-minimum phase plants

For non-minimum phase plants, the loop transfer recovery (LTR) design of integral controllers based on the disturbance cancellation is considered. Since the design requires an unstabilizable extended plant, the standard LTR method cannot be applied. A new partial LTR method is proposed to overcome the difficulty. The target of the proposed design is a fictitious controller including a disturbance estimator based on the measurement of the minimum phase state. It is shown that the Riccati equation including the gain matrix of the disturbance estimator in the target can be used to recover the target feedback property in the output feedback controller. A simple design example is presented to show the effectiveness of the proposed method.     

LTR design of disturbance cancellation integral controllers for time-delay plants

For time-delay plants, the loop transfer recovery (LTR) technique for the integral controller design based on disturbance cancellation is discussed. Since the design requires an unstabilizable extended plant, the standard LTR method cannot be applied. The new LTR method proposed by the authors for lumped plants is extended to time-delay plants by introducing appropriate predictors. A simple design example is presented to illustrate the proposed design method.     

A simple robust PI/PID controller design via numerical optimization approach

This paper presents a simple but effective method for designing robust PI or PID controller. The robust PI/PID controller design problem is solved by the maximization, on a finite interval, of the shortest distance from the Nyquist curve of the open loop transfer function to the critical point-1. Simulation studies are used to demonstrate the effectiveness of the proposed method.     

分域设计迭代学习控制器抑制非重复性扰动

为了抑制迭代方向上已知重复样式的非重复性输出扰动,提出了迭代学习控制(Iterative Learning Control,ILC)的分域算法。时间域内设计传统PID型迭代学习控制器,并且优化其参数;迭代域内利用内模原理抑制非重复性输出扰动,跟踪期望轨迹;利用加权思想将两者相结合,得到迭代学习控制器的分域设计算法。相对于已有算法,建立了针对一般扰动的设计框架,并且合理配置了算法的参数,使收敛速度及精度有所提高。仿真结果说明了该算法的有效性。     

低阶时滞过程的伪预测PI／PID控制

基于单位反馈控制结构,根据期望的闭环传递函数设计得到了一种伪预测PI/PID(ADQPI/ADQPID)控制器。这种控制器只有一个可调参数,可调参数与系统动态响应性能和鲁棒稳定性之间存在直接关系,只需单调的调节控制器参数,便可实现系统的动态响应性能与鲁棒稳定性之间的最佳折衷。仿真实例表明,这种控制器在扰动和模型失配的情况下仍然具有良好的控制性能和鲁棒稳定性,是一种值得在实际工程中推广运用的新型控制器。     

Enhanced design of cascade control systems for unstable processes with time delay

In this paper, optimal H₂ internal model controller (IMC) is designed for control of unstable cascade processes with time delays. The proposed control structure consists of two controllers in which inner loop controller (secondary controller) is designed using IMC principles. The primary controller (master controller) is designed as a proportional-integral-derivative (PID) in series with a lead-lag filter based on IMC scheme using optimal H₂ minimisation. Selection of tuning parameter is important in any IMC based design and in the present work, maximum sensitivity is used for systematic selection of the primary loop tuning parameter. Simulation studies have been carried out on various unstable cascade processes. The present method provides significant improvement when compared to the recently reported methods in the literature particularly for disturbance rejection. The present method also provides robust closed loop performances for large uncertainties in the process parameters. Quantitative comparison has been carried out by considering integral of absolute error (IAE) and total variation (TV) as performance indices.     

A simple and robust speed control scheme of permanent magnet synchronous motor

This paper presents a simple and robust speed control scheme of Permanent Magnet Synchronous Motor (PMSM). It is to achieve accurate control performance in the presence of load torque and plant parameter variation. A robust disturbance cancellation feed forward controller is used to estimate the torque disturbance. The simple and practical control scheme is easily implemented on a PMSM driver using a TMS320LF2407 DSP. The effectiveness of the proposed robust speed control approach is demonstrated by simulation and experhnental results.     

Inertia‐free saturated output feedback attitude stabilization for uncertain spacecraft

In this article, the problem of robust output feedback attitude stabilization control for a class of uncertain spacecraft is investigated, which contains external disturbances, model parameter uncertainty, unknown and uncertain inertia, controller's gain perturbations, measurement errors, and input saturation. The aim of this work is to design a dynamic output feedback controller such that the closed‐loop attitude system is stabilized, while the H_∞ norm of the transfer function from the lumped disturbance and measurement error to output is ensured to be less than a pre‐specified disturbance attenuation level, and the actual control input is confined into a certain range simultaneously. Based on the Lyapunov theory, the existence conditions of such controller are derived in terms of linear matrix inequalities. It is worth mentioning that the controller's additive and multiplicative perturbations are accounted for respectively. An illustrative example is given to demonstrate the effectiveness and advantage of the proposed control design method.     

Nonlinear cascade control of an electro-hydraulic actuator with large payload variation

Electro-hydraulic actuators have been widely used in industrial production, but the unknown variable payload seriously affects its position control accuracy. Therefore, a radial basis function neural network disturbance observer is designed to estimate the lumped disturbance force through strong online learning ability in the absence of force sensor. Besides, a nonlinear cascade controller with double loop structure is proposed in this paper. A global fast terminal sliding mode control method is firstly applied in the outer loop position system, which can eliminate chattering and improve convergence speed comparing to traditional sliding mode control. The inner loop force system adopts a backstepping control method to calculate the actual input of the whole system. Theoretical analysis indicates that the proposed controller is stable even if existing time-variant disturbance. Moreover, three comparative controllers are designed and tested in both simulations and experiments. Comparative results show that the developed method has absolute average errors of 1.14 and 0.49 mm in different position tracking, which means more satisfactory tracking performance compared to the contrast controllers.     

不确定时滞系统的鲁棒H∞控制

基于Lyapunov稳定性理论,研究一类同时具有状态非线性不确定和线性不确定时变时滞系统的鲁棒控制器的设计问题。在非线性不确定性满足增益有界条件下,得到该类时变时滞系统依赖于时变延迟导数的最大值的满足鲁棒H∞性能的一个充分条件。通过求解一个线性矩阵不等式-LMI,即可获得鲁棒H∞控制器。给出的两个具体算例说明该方法的有效性。     

一种新的双环结构机器人无标定自抗扰视觉伺服控制方法

在研究基于自抗扰控制器的机器人无标定视觉伺服方法的基础上，提出了一种新的双环结构机器人无标定自抗扰视觉伺服控制方法．内环采用Kalman滤波算法进行图像雅可比矩阵的在线辨识，可较好地逼近真实模型；外环采用自抗扰控制器，利用非线性观测器实时估计系统相对于当前估计模型的总扰动，并在控制中加以动态补偿．针对六自由度工业机器人进行了二维运动目标的跟踪实验，实验结果表明了该方法的可行性和有效性．     

Robust tracking enhancement of robot systems including motordynamics: a fuzzy-based dynamic game approach

A robust tracking control design of robot systems including motor dynamics with parameter perturbation and external disturbance is proposed in this study via adaptive fuzzy cancellation technique. A minimax controller equipped with a fuzzy-based scheme is used to enhance the tracking performance in spite of system uncertainties and external disturbance. The design procedure is divided into three steps. At first, a linear nominal robotic control design is obtained via model reference tracking with desired eigenvalue assignment. Next, a fuzzy logic system is constructed and then tuned to eliminate the nonlinear uncertainties as possibly as it can to enhance the tracking robustness. Finally, a minimax control scheme is specified to optimally attenuate the worst-case effect of both the residue due to fuzzy cancellation and external disturbance to achieve a minimax tracking performance. In addition, an adaptive fuzzy-based dynamic game theory is introduced to solve the minimax tracking problem. The proposed method is appropriate for the robust tracking design of robotic systems with large parameter perturbation and external disturbance. A simulation example of a two-link robotic manipulator driven by DC motors is also given to demonstrate the effectiveness of proposed design method's tracking performance     

Analytical method of PID controller design for parallel cascade control

An analytical method of PID controller design is proposed for parallel cascade control. Firstly, a general structure for parallel cascade control is proposed that takes both setpoint and load disturbance responses into account. Analytical tuning rules for the PID controllers are then derived for the general process model by employing the IMC design procedure. The proposed method offers a simple and effective way to obtain the PID controller rules for parallel cascade control system which takes into account the interaction between primary and secondary control loops. The simulation results illustrate the application of the proposed method and demonstrate its superiority compared to several alternatives.     

基于功率控制的三相电压型PWM整流器控制器设计

提出基于功率控制的三相电压型PWM(pulse width modulation)整流器控制器设计方法。根据能量守恒原理建立的VSR(voltage source rectifier)数学模型可通过忽略回路电阻及电感充放电所消耗的能量等效成线性定常系统。系统外环采用电容储能控制,内环采用电流控制,同时引入直流负载功率补偿,实现对电容储能变化率的直接控制。电流内环采用前馈解耦PI(proportional-integral)控制,将内环等效成一阶惯性环节。电容储能外环采用PI控制,利用代数分析及根轨迹分析,提出外环PI参数的设计方法。VSR系统整体等效为二阶系统。仿真结果表明：本文所提出的控制器设计方法能使得VSR达到优异的性能。     

H∞ control via output feedback for linear systems with time-varying delays in state and control input

In this paper, an observer-based H_∞ controller for systems with time-varying delays in state and control input is proposed. Using the solution of proposed modified algebraic Riccati equation, we can construct a controller which depends on the maximum value of the time derivative of time-varying delay and guarantees a prescribed H_∞ norm bound of the closed-loop transfer matrix from the disturbance to the controlled output. A given example illustrates the availability of the proposed design method.     

Tuning of multi-loop PI controllers based on gain and phase margin specifications

In this paper, a single-iteration strategy is proposed for the design of a multi-loop PI controller to achieve the desired gain and phase margins for two-input and two-output (TITO) processes. To handle loop interactions, a TITO system is converted into two equivalent single loops with uncertainties drawn from interactions. The maximum uncertainty is estimated for the initial controller design in one loop and single-input and single-output (SISO) controller design is applied. This controller is substituted to other equivalent loop for design, and finally, the first loop controller is refined on knowledge of other loop controller. For SISO controller tuning, a new method is presented to determine the achievable gain and phase margins as well as the relevant controller parameters. Examples are given for illustration and comparison.     

Decoupling two-degree-of-freedom control strategy for cascade control systems

In this paper, two new two-degree-of-freedom control structures are proposed for cascade control systems, both of which are identical in the controller design procedure. The primary controller used for setpoint tracking is derived in terms of H₂ optimal performance objective. The secondary controller is responsible for rejecting load disturbances that seep into the intermediate process and therefore is called a load disturbance estimator, which is inversely figured out by proposing the desired complementary sensitivity function of the inner loop for disturbance rejection. As a result, the nominal setpoint response is decoupled with the load disturbance response of the inner loop, both of which can be optimized independently. Based on the control system stability analysis, the rule of thumb for tuning the single adjustable parameter of each controller is provided to cope with the process uncertainty in practice. Several illustrative examples are included to demonstrate the superiority of the proposed method.     

Pi Tuning Under Performance Constraints

In this paper, a PI controller tuning method is proposed to meet several practical constraints such as the system bandwidth, the stability robustness and the low‐frequency disturbance rejection ability. An objective sensitivity function is first given subject to the above constraints. The PI controller is then designed by making the actual closed‐loop sensitivity function close to the optimal one in the frequency domain. Simulation examples are provided to demonstrate the effectiveness of the proposed method.     

一阶参数不确定滞后过程的鲁棒PID控制器设计

提出一种针对一阶参数不确定滞后过程的鲁棒PI／PID控制器优化设计方法。首先基于D-分割法技术,给出确定一阶参数不确定滞后过程的整个PI／PID控制器的可行鲁棒稳定域算法;在定义一个与控制器给定点跟踪性能、鲁棒性能和抗扰动性能相关的目标函数的基础上,给出PI／PID控制器设计的约束优化问题;最后应用一种启发式粒子群优化（PSO）算法对该约束问题进行求解。仿真结果表明,所提出的方法可得到更小的调节时间、更小的超调、较强鲁棒性和更好的抗扰动性能,表明了所提出的方法的有效性。     

Anti‐windup design of active disturbance rejection control for sampled systems with input delay

A novel anti‐windup design of active disturbance rejection control (ADRC) is proposed for industrial sampled systems with input delay and saturation. By using a generalized predictor to estimate the delay‐free system output, a modified extended state observer is designed to simultaneously estimate the system state and disturbance, which could become an anti‐windup compensator when the input saturation occurs. Accordingly, a feedback controller is analytically designed for disturbance rejection. By proposing the desired closed‐loop transfer function for the set‐point tracking, a prefilter is designed to tune the tracking performance while guaranteeing no steady‐state output tracking error. A sufficient condition for the closed‐loop system stability is established with proof for practical application subject to the input delay variation. Illustrative examples from the literature are used to demonstrate the effectiveness and merit of the proposed control design.