两种补偿动态摩擦力的先进控制策略1)

在小型DC伺服电机中，静摩擦力和库仑摩擦力的影响是相当明显的. 本文提出了改善系统响应特性的两种控制策略. 第一种基于摩擦力模型的在线补偿， 适用于变化信号的跟踪. 第二种基于自学习原理的重复控制，适用于周期信号的跟踪. 两种控制策略均已实施在计算机控制的伺服系统中. 给出了与常规控制结果的对比.     

仿生假手抓握力控制策略

为了使仿生假手完成各种精细作业,提出一种抓握力控制策略.在自由空间和约束空间中分别使用基于位置的阻抗控制和力跟踪阻抗控制.在过渡过程中使用模糊观测器切换控制模式.两种控制模式采用同一个基于位置的阻抗控制器,在约束空间向阻抗控制器中引入参考力,以满足约束空间的抓握力控制要求.这种方法可以使关节在自由空间和约束空间中分别实现良好的轨迹跟踪和力矩跟踪,在过渡过程中实现控制模式的可靠切换和系统的稳定过渡.提出一种自适应滑模摩擦力补偿方法,利用终端滑模思想设计了滑模函数,使得系统跟踪误差在有限时间内收敛,避免了传统线性滑模面状态跟踪误差无法在有限时间内收敛至0的问题.根据指数形式摩擦力的特点,利用终端滑模控制思想获得包含摩擦力参数估计的滑模控制律,并基于李亚普诺夫稳定性定理推导了估计参数的在线自适应律.对该抓握力控制策略在HIT假手上进行了抓取实验,实验结果证明了控制策略的有效性.     

基于滑动模型与图论的多机器人跟踪控制

移动机器人系统的非线性环节是导致控制设计困难的主要原因之一,在三维空间中的运动较二维空间更为复杂.针对三维空间中非线性移动机器人系统的跟踪控制问题,为了提高跟踪速度和改善动态特征,提出了一种基于滑动模型与图论相结合的控制策略.滑模控制方法广泛地适用于非线性对象,并且具有良好的鲁棒性,适合用于非线性机器人控制;从系统整体出发利用图论的知识,对整个编队进行约束,从而构成对整个系统的控制策略,表明能跟踪静态的目标和跟踪动态的目标.仿真提高了系统的稳定性,说明了控制方法的有效性和适用性.     

全局稳定的PD+前馈机器人鲁棒自适应控制

研究应用PD+前馈控制结构的不确定性机器人轨迹跟踪问题.在忽略摩擦力和外部 扰动情况下,设计了一大类综合的自适应控制策略,能保证系统全局的渐近稳定;在摩擦力和外 部扰动存在时,提出两种新颖的鲁棒自适应混合控制方法,不仅可以保证闭环系统的全局稳定 性,同时还能给出系统清晰的暂态性能.严格的理论证明和二自由度机器人的仿真验证了控制 器的有效性.     

基于新型补偿控制策略的柔性关节控制器设计

柔性关节机器人控制系统中存在不确定性扰动、摩擦力、参数变化以及建模误差等问题,而常规PID控制无法兼顾稳定性和控制精度的要求,为此设计了一种基于新型补偿控制策略的柔性关节鲁棒控制器.控制器设计中,将摩擦力分为线性和非线性两部分,扰动分为确定性和不确定性两部分:机器人自身结构相关量、确定性扰动以及摩擦力的线性部分可以通过...     

含有驱动器模型的移动机器人自适应跟踪控制

本文针对包含驱动器模型的移动机器人, 考虑到其在粗糙表面上运动过程中所受的摩擦力以及不可建模的动态的影响, 使用反步设计法(Backstepping)给出了一种自适应跟踪控制策略.其中对于不可建模的动态, 本文使用一种非线性函数对其影响进行抵消,使得机器人的路径跟踪对不确定具有鲁棒性; 对于摩擦力项, 使用径向基神经网络(RBFNN)对其进行逼近, 在控制器中能够根据逼近值给予相应的摩擦力补偿量, 从而使移动机器人比较适合在粗糙度大的路面(如沙地)上进行路径跟踪. 仿真结果验证了该控制方法的有效性.     

车辆主动转向系统的鲁棒控制器设计研究

本文将H2/H∞鲁棒控制理论应用于电动助力转向系统的控制策略研究,在建立前轮转向理想跟踪模型基础上,提出一种基于H2/H∞模型跟踪技术的主动转向控制方法,并对设计的控制器进行仿真分析与对比.通过仿真分析,从理论上验证基于H2/H∞跟踪控制理论的转向控制器可以适用于汽车的EPS转向系统,能很好地跟随理想车辆转向模型,有利于提高车辆的主动安全和稳定性.     

基于一阶不确定项估计律的机械臂鲁棒控制研究

针对多自由度机械臂控制系统的模型参数误差、关节摩擦力以及外部输入扰动等不确定项,设计了一类一阶误差估计律;结合基于机构动力学名义模型的输入输出反馈线性化控制算法,对六自由度刚性机械臂的时变轨迹跟踪控制进行了研究,理论上证明了设计的鲁棒控制器是全局渐进稳定的.仿真结果表明该控制策略对系统的各类不确定项具有很好的鲁棒性,能够实现高精度的轨迹跟踪控制.     

多指灵巧手的位置/力矩控制

提出了一种新的多指手位置/力矩控制策略.该策略基于滑模位置控制和PD力矩控制分别实现自由空间中的轨迹跟踪和约束空间中的力矩跟踪,利用简单的系统观测器实现灵巧手在过渡过程中的控制模式切换.该策略具有很好的位置/力矩跟踪能力,并且可以保证过渡过程的稳定性.实验结果证明了该控制策略的有效性和可行性.     

基于级联式控制策略的农业机械鲁棒自适应路径跟踪控制

在机具负载和外部干扰的影响下,农业机械的横摆角速度动力学特性会发生变化,从而导致基于位置偏差控制方法的路径跟踪性能变差.为此,提出一种基于级联式控制策略的鲁棒自适应路径跟踪控制方法.该方法将路径跟踪控制分解为横向位置控制和横摆角速度控制两个级联的控制任务来完成.在横向位置控制中,根据横向位置偏差和航向偏差,采用模糊自适应纯追踪模型确定农业机械期望的横摆角速度;在横摆角速度控制中,提出一种鲁棒自适应控制方法,使农业机械在机具负载变化或者受到外部干扰时,仍然保证横摆角速度具有期望的响应性能.仿真实验和实际的农业机械实验结果验证了所提出方法的有效性和优越性.     

Adaptive positioning control of an ultrasonic linear motor system

A 3PRR parallel precision positioning system, driven by three ultrasonic linear motors, was designed for use as the object stage of a scanning electron microscope (SEM). To improve the tracking accuracy of the parallel platform, the positioning control algorithms for the drive joints needed to be studied. The dead-zone phenomenon caused by static friction reduces the trajectory tracking accuracy significantly. Linear control algorithms such as PID (Proportion Integration Differentiation) are unable to compensate effectively for the dead-zone nonlinearity. To address this problem, two types of feedforward compensation control algorithms have been investigated. One is constant feedforward with the integral separation PID; the other is adaptive feedback and feedforward based on the model reference adaptive control (MRAC). Simulations and experiments were conducted using these two control algorithms. The results demonstrated that the constant feedforward with integral separation PID algorithm can compensate for the time-invariant system after identifying the dead-zone depth, while the adaptive feedback and feedforward algorithm is more suitable for the time-varying system. The experimental results show good agreement with the simulation results for these two control algorithms. For the dead-zone nonlinearity caused by the static friction, the adaptive feedback and feedforward algorithm can effectively improve the trajectory tracking accuracy.     

Adaptive Task-Space Control of Flexible-Joint Manipulators

This paper considers the motion control and compliance control problemsfor uncertain rigid-link, flexible-joint manipulators, and presents newadaptive task-space controllers as solutions to these problems. The motioncontrol strategy is simple and computationally efficient, requires littleinformation concerning either the manipulator or actuator/transmissionmodels, and ensures uniform boundedness of all signals and arbitrarilyaccurate task-space trajectory tracking. The proposed compliant motioncontrollers include an adaptive impedance control scheme, which isappropriate for tasks in which the dynamic character of theend-effector/environment interaction must be controlled, and an adaptiveposition/force controller, which is useful for those applications thatrequire independent control of end-effector position and contact force. Thecompliance control strategies retain the simplicity and model independenceof the trajectory tracking scheme upon which they are based, and are shownto ensure uniform boundedness of all signals and arbitrarily accuraterealization of the given compliance control objectives. The capabilities ofthe proposed control strategies are illustrated through computer simulationswith a robot manipulator possessing very flexible joints.     

Adaptive integral backstepping sliding mode control for opto-electronic tracking system based on modified LuGre friction model

In order to improve the control accuracy and stability of opto-electronic tracking system fixed on reef or airport under friction and external disturbance conditions, adaptive integral backstepping sliding mode control approach with friction compensation is developed to achieve accurate and stable tracking for fast moving target. The nonlinear observer and slide mode controller based on modified LuGre model with friction compensation can effectively reduce the influence of nonlinear friction and disturbance of this servo system. The stability of the closed-loop system is guaranteed by Lyapunov theory. The steady-state error of the system is eliminated by integral action. The adaptive integral backstepping sliding mode controller and its performance are validated by a nonlinear modified LuGre dynamic model of the opto-electronic tracking system in simulation and practical experiments. The experiment results demonstrate that the proposed controller can effectively realise the accuracy and stability control of opto-electronic tracking system.     

Hybrid optimal control of dry clutch engagement

Lately, with the increasing use of automated manual transmissions (AMT) the engagement control of the dry clutch becomes more important. The engagement control plays a crucial role, since different and conflicting objectives have to be satisfied: preservation of driver comfort, fast engagement and small friction losses. In this paper two optimal control strategies for clutch engagement, based on hybrid control principles, are compared. For developing a useful clutch control scheme, the driveline is modelled as a piecewise linear system. The first control strategy is widely known as explicit MPC. However, it seems that it is not suitable (yet) for this type of problem. The second strategy is a piecewise LQ controller, based on piecewise quadratic Lyapunov functions. Simulation results obtained with both strategies are presented and discussed.     

基于控制性能的MIMO非线性系统动态面控制

针对一类不确定非线性MIMO(multiple-input multiple-output)系统,在动态面控制方法的基础上,提出了自适应跟踪控制方案.通过引入性能函数和输出误差转换,保证输出信号具有指定的跟踪速度、跟踪误差、最大超调量.为了避免控制奇异问题,采用神经网络直接逼近期望控制信号.该方案无需估计神经网络的权值,仅对1个参数进行自适应律设计.理论证明了闭环系统所有信号有界,仿真结果验证了所提方案的有效性.     

Synchronization and tracking control for multi‐motor driving servo systems with backlash and friction

This paper presents a novel switching controller incorporated with backlash and friction compensations, which is utilized to achieve speed synchronization among multi‐motor and load position tracking. The proposed controller consists of two parts: synchronization and tracking control in contact mode and robust control in backlash mode, where a function characterizing whether backlash occurs is used for switching between two modes. Using the proposed switching controller, several control objectives are achieved. Firstly, the coupling problem of speed synchronization and load tracking in contact mode is addressed by introducing a switching plane. Secondly, based on the switching plane, an improved prescribed performance function is introduced to attain load tracking with prescribed performances, and L_∞ performance of speed synchronization is guaranteed by initialization method, maintaining the transient performance of synchronization behavior. Thirdly, the lumped uncertain nonlinearity including friction and other uncertain functions is compensated by Chebyshev neural network in contact mode. Furthermore, a robust control is adopted in backlash mode to make system traverse backlash at an exponential rate and simultaneously eliminate low‐speed crawling phenomenon of LuGre friction. Finally, comparative simulations on four‐motor driving servo system are provided to verify the effectiveness and reliability. Copyright © 2015 John Wiley & Sons, Ltd.     

Robust adaptive control of nonlinear non-minimum phase systems with uncertainties

This paper, presents a robust adaptive control method for a class of nonlinear non-minimum phase systems with uncertainties. The development of the control method comprises two steps. First, stabilization of the system is considered based on the availability of the output and internal dynamics of the system. The reference signal is designed to stabilize the internal dynamics with respect to the output tracking error. Moreover, a combined neuro-adaptive controller is proposed to guarantee asymptotic stability of the tracking error. Then, the overall stability is achieved using the small gain theorem. Next, the availability of internal dynamics is relaxed by using a linear error observer. The unmatched uncertainty is compensated using a suitable reference signal. The ultimate boundedness of the reconstruction error signals is analytically shown using an extension of the Lyapunov theory. The theoretical results are applied to a translational oscillator/rotational actuator model to illustrate the effectiveness of the proposed scheme.     

谐波驱动系统的特性及控制策略研究

谐波传动有很多优点,在机器人驱动中经常被使用．但谐波传动也有一些缺点,如柔性等因 素影响负载端轨迹跟踪精度．本文系统地分析了谐波传动系统的动力学特性,建立了包括电 机转子惯量在内的动力学模型,并且在对系统进行全面实验研究的基础上总结出谐波传动系 统中存在的问题,采用相应的基于传感器的控制策略克服存在的问题,提高系统的响应性能 ．从理论分析和实验结果证实了提出方法的可行性．