Research On Vibration Control Of The Flexible Planar Parallel 3-(?)RR Robot

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.