【作者】 杨杰；

【导师】 邱志成；

【作者基本信息】 华南理工大学 ， 机械电子工程， 2017， 硕士

【摘要】 并联机器人具有高速、高精度、大刚度、承载能力强等特点,广泛应用在电子装配,精密加工与测量,航空航天等领域。而柔性平面并联3-RRR机器人的被动杆比较薄,相对刚度低,从而使并联平台具有了柔性。这也使得结构在高速运动停止时,容易弯曲过大而产生振动,影响系统的稳定性和定位精度。平台和杆件的耦合作用、摩擦、间隙等非线性因素共同影响下的三自由度并联柔性机器人是一个强耦合、非线性的多输入多输出(MIMO)控制系统,加大了控制难度。为了让平台高速稳定运行,必须研究平台的振动,并设计控制算法,对振动进行有效抑制。本文的主要研究内容如下:建立了平台的运动学模型,进行运动学逆解。并规划了直线,圆弧轨迹。由于并联结构本身的特点,并联机器人会在除运动边界外的某些位置呈现出奇异位形。在奇异位置处,动平台将失去部分约束,动力学性质会变差,并可能产生不可控的运动甚至发生危险。快速运行到奇异附近区域时,残余振动容易转换为自激振动。将平台振动分为残余振动和自激振动,并详细地分析自激振动原因。搭建了以PMAC2多轴运动控制卡、PCI-8193数据采集卡为核心,以PC机为支撑的3自由度柔性平面并联机器人平台,基于MFC在VS2010环境下开发控制平台。在运动中,实时采集柔性杆上压电陶瓷所测的振动信息,再存储分析其幅值、频率。实验发现,平台快速运动停止时,杆在短时间内残余振动,而后停止。但在靠近各轴附近,残余振动容易转换为自激振动,可以一直等幅振动,甚至振幅加大。采取的主动振动控制主要有压电陶瓷控振,电机控振。利用压电陶瓷的逆压电效应,采用压电陶瓷致动,可一定程度减小柔性杆的振动。但自激振动能量很大,并不能控制住自激振动。因此使用伺服电机来控制自激振动,采取编码器反馈,脉冲补偿的控制方式。算法是振动主动控制的核心,很大程度决定了控制效果的好坏。针对伺服电机主动控制,首先通过非线性算法在不同的位置对平台进行了实验研究,并采用模糊控制对平台进行了振动控制仿真和实验研究。实验表明,两种算法都能有效地控制住自激振动。这样验证了自激振动产生的原因,控制策略的可行性。更多还原

【Abstract】 Due to its high-speed,high-precision,large stiffness,high load carrying capacity,parallel robots have been successfully used in many aspects,such as in the electronic assembly industry,precision machining and measurement field,aerospace industry and so on.The passive component is too thin so the flexible planar parallel 3-RRR robot is flexible.It can easily bend when a high speed motion stops,affecting stability and positioning precision of the robot.The robot control system is typically a strong coupling nonlinear multiple-input multiple-output(MIMO)system,under the influence of coupling effect,friction,clearance,making it hard to be controlled.For high-speed,high-precision and efficient working,the reason of its vibration must be deeply researched.And it is necessary to design control algorithm to suppress the vibration of 3-RRR planar parallel robot.The main research work is listed as follows:A kinematic model of a flexible planar parallel 3-RRR is established,inverse kinematic solution is carried out.Line and arc trajectory is designed.Because of the characteristics of structure of parallel robot,it can show its singularity in different situation except for the working boundaries.Its dynamic properties can become badly in singular regions.When moving at a high speed near the singular regions,vibration can happen.The vibration of platform is classified into residual vibration and self-excited vibration,and the reason of self-excited vibration is deeply analyzed.Build a control system of flexible 3-RRR planar parallel robot with three degree of freedom,using Programmable Multi-Axis Controller(PMAC)and data acquisition card PCI-8193.During the motion of the platform,real-time sample of vibration on the Lead Zirconate Titanate(PZT)surface-bonded on flexible links is taken.So the vibration situation of the flexible links and the main mode shape of the platform are obtained.Active vibration control strategies include PZT control and Servo motor control.PZT actuator can reduce the vibration to some degree.But self-excited vibration’s energy is too big to use PZT actuator only.The experiments are conducted by utilizing AC servo motor control,encoder feedback and pulse compensation.Algorithm is core of the active vibration control.A nonlinear proportional and derivative(NPD)controller is developed and implemented to control the vibration in different configuration firstly.Then a fuzzy based control algorithm is stimulated and adopted to vibration control.The experimental results demonstrate investigated NPD algorithm and fuzzy control algorithm is feasible.So it shows the reasons of vibration,especially the self-excited vibration,the control strategy’s feasibility.更多还原