具有不确定雅可比矩阵机器人的鲁棒非线性PID控制器的抗饱和失效设计

对于雅克比阵不确定的操作机器人笛卡尔空间操作任务, 提出一种鲁棒非线性PID控制器的抗饱和设计方案, 解决了PID控制中的积分饱和问题. 该控制器通过引入有界递增分段连续函数于PID控制器中的积分环节, 限制了积分器的积分作用, 从而克服了积分环节对闭环系统的不利影响: 一方面使得闭环系统是渐进稳定的, 另一方面又保证了其鲁棒性; 特别是, 相比于其它的抗饱和设计方法, 显得更加简单有效.     

A new continuous high‐gain controller scheme for a class of uncertain nonlinear systems

In this study, we present a new robust continuous controller mechanism for the tracking problem of uncertain nonlinear systems. The proposed strategy is based on a Lyapunov‐type stability argument and only requires the uncertainties of the dynamical system to be the first‐order differentiable to achieve asymptotic practical tracking. For the ease of presentation, the controller formulation is presented on a general, second‐order dynamical system, extension to higher order versions are also possible with a considerably small effort. Simulation studies comparing the performance of the proposed method with the classical Sliding mode and robust integral of the sign of the error controller are presented to illustrate the performance and the feasibility of the proposed strategy. Experimental validation on a two link direct drive robot manipulator are also included to illustrate the implementability of the proposed method. Copyright © 2013 John Wiley & Sons, Ltd.     

A partial state feedback controller for tajectory tracking of rigid-link fiexible-joint robot using an observed backstepping approach

This article presents a partial state feedback controller for a rigid-link flexible-joint (RLFJ) robot using an observed integrator backstepping approach. The robot controller requires only link position and actuator position measurements, and eliminates the need for measuring link velocity and actuator velocity. The controller uses two exact knowledge, second-order nonlinear observers to estimate the link and actuator velocities. The overall control system achieves a semiglobal exponential stability result for the link position and velocity tracking errors as well as the velocity observation errors. A stability proof and simulation results for the proposed partial state feedback controller are included in the article. © 1995 John Wiley & Sons, Inc.     

A Robust Tracking Controller for Electrically Driven Robot Manipulators: Stability Analysis and Experiment

 In this paper, a robust controller for electrically driven robotic systems is developed. The controller is designed in a backstepping manner. The main features of the controller are: 1) Control strategy is developed at the voltage level and can deal with both mechanical and electrical uncertainties. 2) The proposed control law removes the restriction of previous robust methods on the upper bound of system uncertainties. 3) It also benefits from global asymptotic stability in the Lyapunov sense. It is worth to mention that the proposed controller can be utilized for constrained and nonconstrained robotic systems. The effectiveness of the proposed controller is verified by simulations for a two link robot manipulator and a four-bar linkage. In addition to simulation results, experimental results on a two link serial manipulator are included to demonstrate the performance of the proposed controller in tracking a given trajectory.     

Global tracking of nonlinear systems with simultaneous unknown time‐varying state and input delays

This paper presents the design of a robust control law for a class of nonlinear dynamical systems subjected to parametric uncertainty and simultaneous unknown, variable state and input delays. A novel controller is developed, which consists of a filtered tracking error and the integral of previous values of control input where the limits of integration are dependent on the known bound of the input delay. Lyapunov‐Krasovskii functionals–based stability analysis guarantees a global uniformly ultimately bounded tracking result where sufficient conditions on controller gains and maximum allowable delay are derived. The performance and robustness of the controller are evaluated by simulation on a two‐link robot manipulator for different combinations of time‐varying state and input delays.     

Repetitive Learning Control Design and Period Uncertainties

The aim of this brief is to show how stability proofs in the time‐domain involving suitable quadratic‐integral Lyapunov‐like functions can be derived in the repetitive control design scenario in the case of uncertain period for the reference signals/disturbances to be tracked/rejected. Even though the presented arguments are rather general, we apply them to the generalization of the proportional–integral–derivative (PID)‐like learning control that has been recently designed. The use of the presented results in multi‐link robot synchronization tasks provides simple and intuitive solutions to as yet unsolved problems.     

基于智能优化算法的Pendubot轨迹规划与控制方法设计

以垂直Pendubot为研究对象,提出一种基于智能优化算法的轨迹规划与控制方法,以解决Pendubot控制过程中难以从摇起区过渡至平衡区的问题.为Pendubot的驱动连杆规划一条从初始角度到中间角度的正向轨迹和一条从中间角度到目标角度的反向轨迹.欠驱动连杆在系统耦合关系作用下进行运动,对应的Pendubot末端点也运动至相应位置.通过遗传算法优化轨迹参数,将正向和反向轨迹拼合为一条由初始角度到目标角度的驱动连杆轨迹的同时,对应的Pendubot末端点轨迹拼合为一条由垂直向下平衡位置到垂直向上平衡位置的完整轨迹,然后设计跟踪控制器跟踪优化后的驱动连杆轨迹至目标角度,由于耦合关系的存在,Pendubot末端点也运动至垂直向上平衡位置.由于Pendubot受重力作用,其末端点很难长时间稳定在垂直向上平衡位置,故设计镇定控制器,实现Pendubot末端点在垂直向上平衡位置的镇定控制.最后通过仿真实验验证所提出方法的有效性,并通过对比说明所提出方法在奇异点规避、控制器设计和控制效果方面的优势.     

Stability and control aspects of flexible link robot manipulators during constrained motion tasks

The effect of robotic manipulator structural compliance on system stability and trajectory tracking performance and the compensation of this structural compliance has been the subject of a number of publications for the case of robotic manipulator noncontact task execution. The subject of this article is the examination of dynamics and stability issues of a robotic manipulator modeled with link structural flexibility during execution of a task that requires the robot tip to contact fixed rigid objects in the work environment. The dynamic behavior of a general n degree of freedom flexible link manipulator is investigated with a previously proposed nonlinear computed torque constrained motion control applied, computed based on the rigid link equations of motion. Through the use of techniques from the theory of singular perturbations, the analysis of the system stability is investigated by examining the stability of the “slow” and “fast” subsystem dynamics. The conditions under which the fast subsystem dynamics exhibit a stable response are examined. It is shown that if certain conditions are satisfied a control based on only the rigid link equations of motion will lead to asymptotic trajectory tracking of the desired generalized position and force trajectories during constrained motion. Experiments reported here have been carried out to investigate the performance of the nonlinear computed torque control law during constrained motion of the manipulator. While based only on the rigid link equations of motion, experimental results confirm that high-frequency structural link modes, exhibited in the response of the robot, are asymptotically stable and do not destabilize the slow subsystem dynamics, leading to asymptotic trajectory tracking of the overall system. © 1992 John Wiley & Sons, Inc.     

机器人系统输出反馈重复学习轨迹跟踪控制

针对高度非线性多关节机器人的轨迹跟踪问题,提出一类输出反馈重复学习控制算法,使得在只有位置信息可测以及模型信息不确定的条件下即能获得良好的控制品质.非线性滤波器的引入解决了现实中速度信号较难获得的问题,重复学习控制策略实现了对周期性参考输入的渐近稳定跟踪.应用Lyapunov直接稳定性理论证明了闭环系统的全局渐近稳定性.三自由度机器人系统数值仿真结果表明了所提出的输出反馈重复学习控制的有效性.     

PD manipulator controller with fuzzy adaptive gravity compensation

This paper presents a PD manipulator controller with fuzzy adaptive gravity compensation. The main idea is to use a fuzzy adaptive controller to compensate for the gravity term of the robotic manipulator. This controller is designed by using Lyapunov's stability theorem, which guarantees system stability. Simulation is implemented on a two‐link manipulator by using MATALAB and SIMULINK. The results show that this fuzzy adaptive controller makes the manipulator trajectory converge to a desired position. Compared with other proposed fuzzy adaptive manipulator controllers, the PD manipulator controller with fuzzy adaptive gravity compensation is conceptually and structurally simpler and guarantees zero position error. ©2000 John Wiley & Sons, Inc.     

Bringing a multilink pendulum to the equilibrium position using a single control torque

The problem of controlling the multilink pendulum in the neighborhood of a given equilibrium position is considered. A feedback control bringing the pendulum to the equilibrium position in a finite time using a bounded torque applied to the first link is constructed. The proposed approach is based on stability theory of motion and uses the concept of the Lyapunov function that is common for two different stable systems of differential equations. The efficiency of the control is demonstrated by a computer simulation of the three-link pendulum dynamics.     

Dynamics and Noncollocated Model‐Free Position Control for a Space Robot with Multi‐Link Flexible Manipulators

In this paper, both the dynamics and noncollocated model‐free position control (NMPC) for a space robot with multi‐link flexible manipulators are developed. Using assumed modes approach to describe the flexible deformation, the dynamic model of the flexible space robotic system is derived with Lagrangian method to represent the system dynamic behaviors. Based on Lyapunov's direct method, the robust model‐free position control with noncollocated feedback is designed for position regulation of the space robot and vibration suppression of the flexible manipulators. The closed‐loop stability of the space robotic system can be guaranteed and the guideline of choosing noncollocated feedback is analyzed. The proposed control is easily implementable for flexible space robot with both uncertain complicated dynamic model and unknown system parameters, and all the control signals can be measured by sensors directly or obtained by a backward difference algorithm. Numerical simulations on a two‐link flexible space robot are provided to demonstrate the effectiveness of the proposed control.     

基于鲁棒性的链路权重规划算法

在IP网络中,链路权重规划是流量工程中的重要问题。为了优化网络流量并实现负载均衡,针对业务量矩阵的不确定性,依据鲁棒性理论提出一个链路权重规划的MIP模型。该模型使用Γ模型描述业务量矩阵的不确定集,通过表示扰动程度的参数Γ实现了对鲁棒性的调节,在此基础上求得不确定集中最差情况下的最优解。实验结果表明,与传统的链路权重规划方法以及新出现的MRC规划模型相比较,该算法可降低最大链路利用率,分别达到了40%和20%。     

Guaranteed-cost active disturbance rejection control for uncertain systems with an integral controller

Guaranteed-cost active disturbance rejection control (ADRC) for uncertain systems is investigated in this study. Firstly, an integral action is introduced in the framework of ADRC to measure and reduce the tracking error. Then, a robust stability condition is presented, and a quadratic cost function where the tracking error is appearing explicitly is used for ADRC performance assessment. The cost bound is formulated by linear matrix inequality and optimised to obtain controller parameters. Full-dimension extended state observer is used, and thus, the proposed strategy is applicable to an uncertain system that allows relative-degree varying or right-half-plane zero. Finally, the validity of the proposed method and its advantages is demonstrated through the simulations of comparative examples and experiments on a motor speed control system.     

Nearly optimal neural network stabilization of bipedal standing using genetic algorithm

In this work, stability control of bipedal standing is investigated. The biped is simplified as an inverted pendulum with a foot-link. The controller consists of a general regression neural network (GRNN) feedback control, which stabilizes the inverted pendulum in a region around the upright position, and a PID feedback control, which keeps the pendulum at the upright position. The GRNN controller is also designed to minimize an energy-related cost function while satisfying the constraints between the foot-link and the ground. The optimization has been carried out using the genetic algorithm (GA) and the GRNN is directly trained during optimization iteration process to provide the closed loop feedback optimal controller. The stability of the controlled system is analyzed using the concept of Lyapunov exponents, and a stability region is determined. Simulation results show that the controller can keep the inverted pendulum at the upright position while nearly minimizing an energy-related cost function and keeping the foot-link stationary on the ground. The work contributes to bipedal balancing control, which is important to the development of bipedal robots.     

Augmented Sliding Mode Control for Flexible Link Manipulators

A method of sliding mode control (SMC) is proposed for the control of flexible, nonlinear, and structural systems. The method departs from standard sliding mode control by dispensing with generalized accelerations during the control law design. Global, asymptotic stability of rigid body motion is maintained if knowledge on the bounds of the neglected terms exists. Furthermore, this method provides damping for the measured flexible body modes. This paper investigates an augmented SMC technique for slewing flexible manipulators. A conventional sliding surface uses a first order system including a combination of error and error rate terms. The augmented sliding surface includes an enhanced term that helps to reject flexible degrees-of-freedom. The algorithms are theoretically developed and experimentally tested on a slewing single flexible link robot. The test apparatus is instrumented with a strain gauge at the root and an accelerometer attached at the tip. A DC motor and encoder are used to servo the link from an initial position to a final position. A standard cubic polynomial is employed to generate the reference trajectories. The augmented SMC algorithm showed improved performance by reducing the flexible link tip oscillations.     

Adaptive Output Feedback Control of Flexible-Joint Robots Using Neural Networks: Dynamic Surface Design Approach

In this paper, we propose a new robust output feedback control approach for flexible-joint electrically driven (FJED) robots via the observer dynamic surface design technique. The proposed method only requires position measurements of the FJED robots. To estimate the link and actuator velocity information of the FJED robots with model uncertainties, we develop an adaptive observer using self-recurrent wavelet neural networks (SRWNNs). The SRWNNs are used to approximate model uncertainties in both robot (link) dynamics and actuator dynamics, and all their weights are trained online. Based on the designed observer, the link position tracking controller using the estimated states is induced from the dynamic surface design procedure. Therefore, the proposed controller can be designed more simply than the observer backstepping controller. From the Lyapunov stability analysis, it is shown that all signals in a closed-loop adaptive system are uniformly ultimately bounded. Finally, the simulation results on a three-link FJED robot are presented to validate the good position tracking performance and robustness of the proposed control system against payload uncertainties and external disturbances.     

Position Control of a Flexible Manipulator Using a New Nonlinear Self-Tuning PID Controller

In this paper, a new nonlinear self-tuning PID controller(NSPIDC) is proposed to control the joint position and link deflection of a flexible-link manipulator(FLM) while it is subjected to carry different payloads. Since, payload is a critical parameter of the FLM whose variation greatly influences the controller performance. The proposed controller guarantees stability under change in payload by attenuating the non-modeled higher order dynamics using a new nonlinear autoregressive moving average with exogenous-input(NARMAX) model of the FLM. The parameters of the FLM are identified on-line using recursive least square(RLS) algorithm and using minimum variance control(MVC) laws the control parameters are updated in real-time. This proposed NSPID controller has been implemented in real-time on an experimental set-up. The joint tracking and link deflection performances of the proposed adaptive controller are compared with that of a popular direct adaptive controller(DAC). From the obtained results, it is confirmed that the proposed controller exhibits improved performance over the DAC both in terms of accurate position tracking and quick damping of link deflections when subjected to variable payloads.     

控制量前具有不确定系数的电液伺服系统自适应控制

针对控制输入前具有不确定系数的电液伺服位置系统精确跟踪控制问题, 提出了一种改进的自适应Backstepping控制器设计方法. 该方法通过对系统模型的等价变换和选择合适的Lyapunov函数, 有效解决了系统模型中控制输入前存在不确定系数而导致所设计的控制器存在参数自适应律, 而自适应律中存在控制量造成的嵌套难题. 以驱动连铸结晶器的电液伺服位置系统为例, 进行了控制器的设计和稳定性证明. 仿真研究结果表明, 所提出的改进设计方法是可行的, 设计的控制器具有较强的鲁棒性和良好的跟踪性能.     

移动自组织认知网络中的路由选择与信道分配方法

针对移动自组织认知网络中路由不稳定的问题,提出了一种路由选择与信道分配方法。首先,设计数据传输花费度量,兼顾路由稳健性和信道干扰;其次,依据认知节点的位置和速度信息计算链路剩余时间,预测路由稳健性;再次,针对不同的信道干扰模式实施信道分配,规避主节点干扰;最后,通过路由发现和路由确认步骤,选择最佳链路。仿真实验表明,与 经典的AODV方法相比,所提方法丢包率低、传输时延小。