Robustness analysis of a pd controller with approximate gravity compensation for robot manipulator control

Asymptotically stable robot manipulator control in both joint space and Cartesian space can be achieved by using a PD controller with gravity torque compensation. However, the stability of this class of control law has not been analyzed with the use of estimated gravity torques. The objective of this article is to present such a stability proof assuming uncertainty in the gravity estimate. The proof is carried out for the Cartesian space controller. The result is supported by computer simulation. © 1994 John Wiley & Sons, Inc.     

地面装调的空间机械臂在空间应用时的自适应鲁棒控制

针对空间机械臂在轨操控过程中,重力加速度不同于地面装调阶段的重力加速度,会随着空间位置的改变而变化的问题.本文提出了一种自适应鲁棒控制策略,用于空间机械臂的末端控制,从而使在地面重力条件下装调好的空间机械臂能够在空间微重力条件下实现在轨操控任务.通过分析重力项对空间机械臂轨迹跟踪控制的影响,设计自适应律在线估计重力加速度,从而得到重力项的估计,系统的不确定性通过鲁棒控制器来补偿.基于李雅普诺夫理论证明了闭环系统的稳定性.仿真结果表明,在地面装调阶段的重力环境下和空间应用阶段的微重力环境下,该控制器对空间机械臂的末端控制均能达到较高的轨迹跟踪精度,具有重要的工程应用价值.     

卫星天线展开臂的随动吊挂重力补偿系统设计

为了给卫星天线展开臂的展开特性测试提供真实的零重力地面仿真环境,设计了卫星天线随动吊挂重力补偿系统.首先设计了与卫星天线展开臂结构相同的3轴随动吊挂机械臂,对卫星天线展开臂进行位置跟随,并通过有限元方法分析其受载时的位置精度;然后根据导纳控制方法设计出随动机械臂的力跟随控制器,采用基于位置内环的PD （比例-微分）力控制策略设计出拉力系统对吊索拉力的控制算法;最后通过实验考核了随动吊挂机械臂各关节对在轨运行模式下的天线展开臂相应关节的位置跟随性能和重力平衡补偿.实验结果表明各轴位置跟随误差均不超过±0.03°,稳定运行时吊索张力控制偏差均小于1.2% F.S.（全量程）,在天线展开机械臂的展开过程中实现了较高精度的位置跟随和重力补偿,满足天线展开测试要求.     

基于模糊PID的悬吊式机械臂重力补偿控制系统设计

针对悬吊式机械臂在工作过程中受起吊荷载的影响而产生的重心不稳现象,在模糊PID控制算法的支持下,进行悬吊式机械臂重力补偿控制系统设计研究。硬件方面,改装主控制器、传感器和通信模块,加设重力补偿装置及驱动电机设备。在此基础上完成软件设计,根据机械臂的组成结构以及工作原理,构建悬吊式机械臂数学模型。在该模型下,检测悬吊式机械臂实时位姿,针对不同位姿建立相应的重力平衡方程。计算机械臂负载力矩,利用模糊PID算法求解机械臂重力补偿控制量,实现悬吊式机械臂重力补偿控制功能。实验结果表明：与传统重力补偿控制系统相比,优化设计系统的控制误差降低了0.056kN,机械臂的稳定系数提升了0.14,即优化设计系统可提高补偿控制效果,具有一定应用价值。     

具有固定重力补偿的模糊免疫PD控制在气动人工肌肉驱动机械手位置控制中的应用

为了克服具有固定重力补偿的传统PD控制存在的不足,提高气动机械手位置控制的精度和控制系统的适应性和鲁棒性,借鉴生物免疫反馈响应过程的调节作用和模糊推理逻辑可逼近非线性函数的特性,将模糊控制算法和免疫反馈机理与具有固定重力补偿的传统PD控制算法相结合,提出了具有固定重力补偿的模糊免疫PD控制算法,并将它应用到气动人工肌肉驱动的机械手的固定点位置控制中.实验结果表明,该控制方法的控制性能优于常规的PD控制,具有一定的实际应用价值.     

Fuzzy sliding-mode control with rule adaptation for nonlinear systems

Abstract: A fuzzy sliding-mode control with rule adaptation design approach with decoupling method is proposed. It provides a simple way to achieve asymptotic stability by a decoupling method for a class of uncertain nonlinear systems. The adaptive fuzzy sliding-mode control system is composed of a fuzzy controller and a compensation controller. The fuzzy controller is the main rule regulation controller, which is used to approximate an ideal computational controller. The compensation controller is designed to compensate for the difference between the ideal computational controller and the adaptive fuzzy controller. Fuzzy regulation is used as an approximator to identify the uncertainty. The simulation results for two cart–pole systems and a ball–beam system are presented to demonstrate the effectiveness and robustness of the method. In addition, the experimental results for a tunnelling robot manipulator are given to demonstrate the effectiveness of the system.     

PD control with on-line gravity compensation for robots with elastic joints: Theory and experiments

A proportional-derivative (PD) control with on-line gravity compensation is proposed for regulation tasks of robot manipulators with elastic joints. The work extends a previous PD control with constant gravity compensation at the desired configuration. The control law requires measuring only position and velocity on the motor side of the elastic joints, while the on-line gravity compensation torque uses a biased measure of the motor position. It is proved via a Lyapunov argument that the control law globally asymptotically stabilizes the desired robot configuration. A simulation study on a two-joint arm reveals the better performance that can be obtained with the new scheme as compared to the case of constant gravity compensation. Moreover, the proposed controller is experimentally tested on an eight-joint cable-driven robot manipulator, in combination with a point-to-point interpolating trajectory, showing the practical advantages of the on-line compensation.     

Adaptive nonlinear control of induction motor

This work addresses the problem of controlling a rigid arm (one degree of freedom robot manipulator) directly driven by an induction motor. A Lyapunov-based adaptive nonlinear controller is designed. The developed controller compensates for parametric uncertainty associated with the resistance of the rotor windings and it is capable to track asymptotically a trajectory for an angular position keeping all the internal signals bounded and guarantees the asymptotical stability of the system. Simulations are presented to illustrate the performance of this controller.     

空间机械臂地面竖直方向重力补偿控制系统设计

为解决大型空间机械臂地面微重力模拟实验问题,设计了一种3维主动悬吊式重力补偿系统.系统主要由水平2维直线运动单元与竖直重力平衡吊挂单元组成,在竖直方向上通过恒张力控制思想实现微重力模拟,并给出了带负载的伺服电机的数学模型.提出一种基于模糊PID(比例―积分―微分)参数整定的力/位混合控制方法,并研究了在未知负载干扰、系统干扰以及机械臂不同运动速度下控制器的控制性能.仿真实验结果表明,该控制方法能够将重力补偿精度保持在0.3%F.S(全量程)之内,使得系统具有较强的鲁棒性和动态响应能力.     

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.     

下肢携行外骨骼系统模糊自适应位置控制研究

研究下肢携行外骨骼系统稳定性控制问题。下肢携行外骨骼系统支撑行走阶段位置控制存在稳定性、实时性不足,提高位置控制的速度及精度,使具有适应性和鲁棒性,为了克服具有实时重力补偿的传统方法,提出固定重力补偿的位置控制方法,并利用模糊推理逻辑可逼近非线性函数的特点,将模糊控制算法与具有固定重力补偿的传统PD控制算法相结合,提出了具有固定重力补偿的模糊自适应位置控制算法,应用到下肢携行外骨骼支撑行走阶段的位置控制中。仿真结果表明控制方法能够使外骨骼准确迅速跟踪人体运动,并能够显著减小人所施加的力矩,系统鲁棒性较强,能够适应负载的变化,证明是一种行之有效的控制方法。     

Adaptive control of harmonic drive with parameter varying friction using structurally dynamic wavelet network

In this paper, an adaptive controller with structurally dynamic wavelet network is developed for a harmonic drive subject to parameter varying friction. The control architecture integrates a proportional controller, a feedback adaptive component and sliding component to adaptively compensate for the friction to achieve accurate position tracking. Global asymptotic stability of the algorithm is proved by using Lyapunov function. In parallel to the adaptive controller, a fuzzy reconfiguration scheme is devised to change the structure of the network along with weights updating to improve the system tracking performance and robustness. Experimental tests on a harmonic drive manipulator verify the effectiveness of the proposed control method.     

Design,analysis and control of a winding hybrid-driven cable parallel manipulator

This paper is related to the design, analysis and control of a winding hybrid-driven cable parallel manipulator (WHCPM). The WHCPM has the advantages of both cable parallel manipulator and hybrid-driven planar five-bar mechanism. Design of the WHCPM is explained, and the structure static analysis is carried out by using finite element method. Dynamics and payload capability of the WHCPM are studied. The WHCPM prototype is built for precision tracking experiments. To evaluate the manipulator design, the dynamic control compensation is performed on the basis of the conventional PID controller and the adaptive fuzzy sliding mode controller. The simulated and experimental results are reported and the tracking performance of the WHCPM is significantly improved by applying the proposed control technique in comparison with the performance when applying the conventional PID controller.     

不确定非线性系统的模糊鲁棒??∞ 跟踪控制

针对一类不确定非线性系统,提出一种新的模糊鲁棒H∞跟踪控制方案。应用模糊T-S模型表征非线性系统,系统不确定性通过模糊逻辑系统消除。由线性矩阵不等式和自适应律给出了模糊控制器存在的一个充分条件。基于Lyapunov稳定性理论,模糊控制方案在所有闭环信号最终一致有界下保证了期望的H∞跟踪性能。两连杆机械臂的仿真结果表明了该方案的可行性。     

PD‐like controllers for delayed bilateral teleoperation of manipulators robots

This paper proposes a compensated PD‐like controller for delayed bilateral teleoperation of a manipulator robot. The scheme has a PD‐like remote controller, a damping into the master, and a compensation strategy. The proposed compensation removes part of potential energy of the user's command depending on the difference between the situation on the remote site and the situation as perceived by the human operator. In addition, the stability of the delayed teleoperation system is analyzed, and a comparison based on experiments is carried out in order to analyze the advantages of using the proposed compensation. Finally, results of a bilateral teleoperation including the proposed control scheme, where the master and slave exchange information by using a low‐cost connection of mobile Internet, are shown. Copyright © 2014 John Wiley & Sons, Ltd.     

非线性系统的直接自适应输出反馈监督模糊控制

针对一类单输入单输出非线性不确定系统，提出一种稳定的直接自适应模糊输出反馈监督控制算法，该算法不需要系统的状态完全可测的假设条件，监督控制不仅迫使系统的状态在指定的集合内，而且当模糊自适应控制处于良好的工作状态时，监督控制可以关闭，证明了整个模糊自适应输出反馈控制算法可以保证闭环系统稳定。     

A Review of: “Fuzzy Sets and Their Applications”. By C. V. NEGOIT[Abreve] and D. A. RALESCU. (In Rumanian) (Bucharest: Editura Technica, 1974.) [Pp.219.]

This paper presents a new controller for position and force control of robotic devices interacting with passive environments. In this approach, for the manipulator dynamics in joint space, suitable output equations are defined which represent the position control and force control subspaces. The dynamics of the manipulator are projected along these subspaces to obtain the dynamics in the respective subspaces. The resulting dynamics are linearized and decoupled using a nonlinear input-state linearizing controller. For the position control subspace dynamics, desirable stability features are achieved through pole placement design. Along the force control subspace, a soft base is introduced, the compliance effect of which is controlled by an appropriate compensation term. Based on the force feedback information, this compensation is modifed online using an extended dynamics. Assuming a model of the passive environment, aspects of local stability of the controller have been discussed. The theory has been presented for a two-link planar manipulator example, based on which, a numerical simulation is discussed.     

基于模糊控制系统的机械臂自适应控制算法设计

针对现有机械臂控制算法,在轨迹控制和精度补偿方面存在的不足,设计了一种基于模糊补偿系统的自适应控制算法。先在笛卡尔空间内分析了机械臂的空间动力学运动过程,并得出机械臂运动中的最优力矩值,构建模糊控制规则并设定模糊子集;对经典模糊理论进行优化,引入可变论域思维在机械臂运动过程中,系统会实时反馈末端执行器行动轨迹,并实施动态化补偿;基于自适应算法对可变论域模糊控制器进行二次优化,修正模糊规则并校正模型的控制量参数,提升和改善整个机械臂系统的控制精度。实验结果显示,模糊补充自适应控制算法在多关节和多连杆机械臂的角度控制和位移控制精度方面有较大的优势,同时各关节和连杆的运动相应时间仅为0.27s和0.20s。     

An Adaptive Regulator of Robotic Manipulators in the Task Space

This note addresses the problem of position control of robotic manipulators both nonredundant and redundant in the task space. A computationally simple class of task space regulators consisting of a transpose adaptive Jacobian controller plus an adaptive term estimating generalized gravity forces is proposed. The Lyapunov stability theory is used to derive the control scheme. The conditions on controller gains ensuring asymptotic stability are obtained herein in a form of simple inequalities including some information extracted from both robot kinematic and dynamic equations. The performance of the proposed control strategy is illustrated through computer simulations for a direct-drive arm of a SCARA type redundant manipulator with the three revolute kinematic pairs operating in a two-dimensional task space.     

非线性系统的间接自适应模糊输出反馈监督控制

In this paper, an indirect adaptive fuzzy output feedback controller with supervisory mode for a class of unknown nonlinear systems is developed. The proposed approach does not need the availability of the state variables, moreover, a supervisory controller is appended to the adaptive fuzzy controller to force the state to be within the constraint set. Therefore, if the adaptive fuzzy controller cannot maintain the stability, the supervisory controller starts to work to guarantee stability. On the other hand, if the adaptive fuzzy controller works well, the supervisory controller will be deactivated. The overall adaptive fuzzy control scheme guarantees the stability of the whole closed-loop systems. The simulation results confirm the effectiveness of the proposed method.