压电柔性机械臂的主动振动控制研究

针对柔性机械臂的振动问题,采用压电智能结构作为敏感器和驱动器进行主动控制.首先建立柔性机械臂的实验装置,其次对设计的柔性机械臂系统进行辨识研究,得到系统的前二阶模态频率,再次采用PD控制和PPF控制算法对柔性机械臂进行主动振动控制.实验结果表明,采用压电智能结构可以抑制柔性机械臂的振动,效果明显.     

基于压电陶瓷的柔性机械臂主动振动控制实验研究

柔性机构因其工作效率高,能量消耗低和结构简单等优点被广泛应用于机器人领域.但柔性机构由于刚度较低,易产生弹性振动,使机器人的定位精度和运动精度降低.为了验证在前期的工作中提出的柔性机械臂主动振动最优控制位置分析的正确性,搭建了一个基于Labview的测试系统.在柔性臂上不同位置粘贴压电片来实现对柔性臂不同位置的主动振动控制,通过测试系统得到最优控制位置处和最优控制位置附近的柔性机械臂振动的传感电压,根据控制前后传感电压的变化分析柔性臂抑制的强弱.根据实验结果显示,柔性臂在前三阶振动下,分别在其最优控制位置上获得最高的抑振率,从而验证了最优控制位置的有效性.     

柔性遥操作机器人系统的滑模变结构控制

针对遥操作机器人系统,在空间与医疗手术中应用时出现的从机械臂柔性问题,为了提高跟踪性能,采用拉格朗日法结合假设模态法,建立了末端有集中质量的单连杆柔性从机械臂的动力学模型。在此基础上,设计了一种基于柔性从机械臂的遥操作机器人系统的新型滑模变结构控制方案。进行实例仿真,结果表明,控制方案能有效地抑制柔性从机械臂的弹性振动,自由运动情况下系统能较好地实现位置跟踪。     

柔性臂机器人控制方法的研究

柔性臂机器人由于具有质量轻、惯性小和能耗低等优点,在制造业和航空航天领域的的应用越来越广泛.但是柔性臂在运动过程中时产生的振动,使力和位置等控制精度大大降低,直接影响了机器人的响应速度和控制精度等运行指标,因此对其控制策略的研究显得十分重要.本文对柔性臂的常用控制方法进行了介绍,如PID控制、自适应控制、变结构控制等.指出柔性臂的控制方法在很多方面还存在共性的问题,并针对这些问题指出了今后的研究方向.     

采摘机械臂自适应输入整形控制研究

采摘机械臂在夹住柔性果茎后运输果实时,执行器末端的加减速运动使得果实在移动过程中产生摆动,易引发掉落,进而导致采摘失败.本文以单个西红柿作为负载,将果茎近似为柔性连杆.由于每一个果实的质量是不同的,因此,针对机械臂抓取可变柔性负载移动过程中的振动抑制问题,提出了自适应输入整形控制方法.当系统模型由于负载的不确定性发生变化后,传统的输入整形算法无法抑制柔性连杆移动过程中产生的振动.因此采用自适应输入整形算法,实时计算脉冲的幅值和时间.构造二次性能指标函数,通过对机械臂移动的加速度和负载的摆角实时数据进行迭代运算,达到零残余振动的目的.仿真实验结果表明,在变负载情况下,自适应输入整形算法有良好的末端振动抑制能力,获得满意的控制效果.     

智能柔性机械臂的建模和振动主动控制研究

针对伺服电动机、谐波齿轮减速器、柔性臂及压电致动器组成的智能柔性机械臂系统,基于假设模态法和Hamilton原理建立系统动力学方程.为了实现系统较高精度的位置控制,同时快速抑制柔性臂的弹性振动,提出了对伺服电动机采用PD(proportional derivative)控制、对压电致动器采用模糊(fuzzy)控制的复合控制策略.在数值仿真分析的基础上,搭建了智能柔性机械臂系统测控平台.数值仿真和实验结果表明所提出的控制策略是可行的:PD控制算法控制伺服电动机以较高的位置精度完成了系统运动控制,模糊控制算法控制压电致动器较快地抑制了柔性臂的弹性振动.实验中柔性臂的振动衰减时间由6.5s缩短为3.5s,提高了柔性臂末端的定位控制精度,改善了系统的操作效率.     

受限柔性机器人臂的鲁棒变结构混合位置/力控制

针对一类平面双连杆受限柔性机器人臂提出一种混合位置/力控制方案,采用鲁棒变 结构控制策略对控制方案进行修正,以改善该柔性机器人系统的鲁棒性,控制机器人终端执行 器的位置和接触力.通过引入变结构鲁棒控制器,可确保输出跟踪误差在有限时间内收敛到零, 或一致终结有界.计算机仿真结果证明了这种控制方案的可行性和有效性.     

柔性臂仿人智能变结构控制

柔性臂的位置控制中，最大的难点是柔性振动的抑制，常规控制方法往往不能同时得到良好的关节跟踪轨迹和对柔性振动的补偿。本文提出了仿人智能变结构控制方法，此方法综合了仿人智能控制与变结构控制的优点，仿真结果表明，这种控制方法能有效的抑制柔性振动，同时具有良好的关节跟踪能力。     

光电传感器跟踪瞬态过程

<正> 工业机器人,由于需要具有快速与低能耗特性,要求其机构轻.尤其是安装在卫星上的机器人更要求其轻便.当轻型机器人带有一重的末端执行器时,机械臂不再是刚性的,由于它们的柔性,可能发生所不希望频率下的振动.因此,为了控制机器人臂的运动及抑制或减小振动幅度,需要复杂的位置控制.     

柔性智能结构的振动主动控制仿真和实验研究

基于模态坐标表示的含压电片结构横向振动系统方程,采用独立模态法直接针对系统的高阶模型设计控制律,利用劳斯判据证明由所设计的控制器引起的控制溢出可被有效抑制,极大地降低了由于模型降阶引起的误差。同时,对压电柔性悬臂梁的高阶振动模态进行主动控制仿真模拟和实验研究,结果表明施加主动控制后柔性悬臂梁的模态阻尼显著提高,受控悬臂梁的振动得到了快速抑制。仿真计算和实验结果取得了良好的一致性。研究结果表明,利用压电陶瓷作为驱动元件,采用独立模态控制法实现柔性结构的振动抑制是一种高效的振动主动控制方法,在航天航空等领域中     

Hybrid Control Scheme for Robust Tracking of Two-Link Flexible Manipulator

The hybrid control scheme is proposed to stabilize the vibration of a two-link flexible manipulator while the robustness of Variable Structure Control (VSC) developed for rigid manipulators is maintained for controlling the joint angles. The VSC law alone, which is designed to accomplish only the asymptotic decoupled joint angle trajectory tracking, does not guarantee the stability of the flexible mode dynamics of the links. In order to actively suppress the flexible link vibrations, hybrid trajectories for the VSC are generated using the virtual control force concept, so that robust tracking control of the flexible-link manipulator can also be accomplished. Simulation results confirm that the proposed hybrid control scheme can achieve more robust tracking control of two-link flexible manipulator than the conventional control scheme in the presence of payload uncertainty.     

Hybrid Control Scheme for Robust Tracking of Two-Link Flexible Manipulator

A hybrid control scheme is proposed to stabilize the vibration of a two-link flexible manipulator while robustness of Variable Structure Control (VSC) developed for rigid manipulators is maintained for controlling the joint angles. The VSC law alone, which is designed to accomplish only the asymptotic decoupled joint angle trajectory tracking, does not guarantee the stability of the flexible mode dynamics of the links. In order to actively suppress the flexible link vibrations, hybrid trajectories for the VSC are generated using the virtual control force concept, so that robust tracking control of the flexible-link manipulator can also be accomplished. Simulation results confirm that the proposed hybrid control scheme can achieve more robust tracking control of two-link flexible manipulator than the conventional control scheme in the presence of payload uncertainty.     

Vibration Control of a Planar Parallel Manipulator Using Piezoelectric Actuators

This paper presents an active damping control approach applied to piezoelectric actuators attached to flexible linkages of a planar parallel manipulator for the purpose of attenuation of unwanted mechanical vibrations. Lightweight linkages of parallel manipulators deform under high acceleration and deceleration, inducing unwanted vibration of linkages. Such vibration must be damped quickly to reduce settling time of the manipulator platform position and orientation. An integrated control system for a parallel manipulator is proposed to achieve precise path tracking of the platform while damping the undesirable manipulator linkage vibration. The proposed control system consists of a PD feedback control scheme for rigid body motion of the platform, and a linear velocity feedback control scheme applied to piezoelectric actuators to damp unwanted linkage vibrations. In this paper, we apply the proposed vibration suppression algorithm to two different types of piezoelectric actuators and evaluate their respective performances. The two piezoelectric actuators are (i) a PVDF layer applied to the flexible linkage and (ii) PZT actuator segments also applied to the linkage. Simulation results show that both piezoelectric actuators achieve good performance in vibration attenuation of the planar parallel manipulator. The dynamics of the planar parallel platform are selected such that the linkages have considerable flexibility, to better exhibit the effects of the vibration damping control system proposed.     

Dynamic modeling and vibration characteristics analysis of flexible-link and flexible-joint space manipulator

With the development of space technology, lighter and larger space manipulators will be born, of which flexible characteristics are more obvious. The manipulator vibration caused by the flexibility not only reduces the efficiency of the manipulator but also affects the accuracy of the operation. The flexibility of space manipulator mainly comes from structural flexibility of links and transmission flexibility of harmonic gear reducer in joints. The vibrations generated by these two kinds of flexibility are coupled and transformed mutually, making the dynamics characteristics of space manipulator system complicated. Therefore it is difficult to assess respective effects of these flexibilities on vibrations of the manipulator tip. And the characteristics of integrated vibration of manipulator tip with different link and joint stiffnesses are not very clear. In this paper, the dynamic equations of multi-link multi-DOF flexible manipulator are established. Then, vibration responses of the tip under different elastic modulus, damping and joint stiffness were studied, and vibration characteristics of the tip with both link and joint were also analyzed. Moreover, the effects of motion planning on the vibration of the tip were analyzed. Finally, the vibration characteristics of the manipulator with flexible joints and links are verified by a two-degree-of-freedom manipulator experimental system. Dynamics analysis results presented some useful rules for the path planning and control to suppress the vibration of the flexible space manipulator.     

Position/vibration control of two-degree-of-freedom arms having one flexible link with artificial pneumatic muscle actuators

A manipulator with a light and thus flexible link would be advantageous over a rigid link in the sense that it is physically safer when it comes into contact with its environment than a manipulator with a rigid and thus heavy link, even though it is harder for a flexible link manipulator to be robustly controlled. On the other hand, if an actuator can deliver enough force while maintaining proper compliance, it would be advantageous for the sake of safety. An artificial pneumatic muscle-type actuator is an adequate choice in this case. In this work, position control problem of a two-degree-of-freedom arm system having a flexible second link with artificial pneumatic muscle-type actuators is addressed. A composite controller design method is proposed in the framework of the singular perturbation method. Various robust control schemes are designed in order to meet with payload variation, parameter uncertainty, unmodeled vibration mode, actuator dynamics both in the slow and the fast subsystems.     

无杆气缸驱动的柔性机械臂振动控制

提出了一种无杆气缸驱动的柔性机械臂定位和振动抑制系统,采用脉冲码调制(pulse code modulation,PCM)方法实现.首先,推导了气动驱动柔性臂的系统模型,对采用的复合定位和振动抑制控制算法进行理论分析.其次,气缸行程长、气体具有压缩性以及气动驱动存在非线性和阀门开关有时延等因素会引起控制作用的滞后问题,容易激发高阶模态的极限环振荡,导致观测和控制溢出,这将影响控制系统的稳定性.为了克服上述问题,在控制算法中引入时延补偿、低通滤波法.最后,进行气动驱动柔性臂同时定位和振动抑制的试验研究.试验结果表明,采用的气动驱动控制方法可以有效地抑制柔性臂的低频模态振动,并同时实现定位.     

基于压电陶瓷的柔性机器人主动抑振控制策略研究

柔性机器人因其轻质、高效、低能耗等优点已被广泛应用于航空航天,工业制造等诸多领域。然而,柔性机构易产生弯曲变形,引起系统振动而大大降低机器人的工作精度。为提高柔性机器人的工作性能,多种抑振策略得以研究与应用。提出了基于压电陶瓷（PZT）的柔性机器人振动主动抑制策略。其中,PZT传感器和PZT制动器分别被用来检测和抑制柔性臂的振动。本文构建了基于PZT材料的单自由度柔性机械臂的理论模型,并获得了传感电压与制动电压的传递函数。设计了一个可变控制方案的抑振器以抑制系统在不同频率下的振动。在COMSOL中进行仿真,获得了系统的抑振率。根据仿真结果显示,柔性臂在前三阶振动下,臂的末端位移分别得到了57.04%,57.76%与58.96%的抑制;系统的动能得到了57.95%,71.19%与87.81%的抑制。     

柔性臂建模与控制方法研究

综述柔性臂建模与控制的主要理论与方法。其中,控制问题包括:位置控制、力控制和柔性振动控制。在考虑参数不确定性和外部扰动的情况下,给出了一种自适应控制方法。最后,指出了今后值得进一步研究的方向。