Design, Analysis And Control Of Planar3-RRR Parallel Manipulator Driven By Ultrasonic Motor

As the technology in high-tech fields such as the precision manufacturing and equipmentdevelops, conventional electromagnetic motor cannot entirely meet the requirements of bothscientific research and engineering applications. Ultrasonic motor possesses many goodproperties such as small size, light weight, low noise, free of electromagnetic interference andhigh torque at low speed. When a joint is actuated by the ultrasonic motor, no reduction gearis required. Therefore, using ultrasonic motor to actuate a parallel manipulator will improvethe control performance and precision, and expand the application range of the parallelmanipulator. In this paper, the ultrasonic motor takes place of the electromagnetic motor, andthe design, analysis and control of the planar3-RRR parallel manipulator actuated byultrasonic motor are studied.Firstly, the design of the planar3-RRR parallel manipulator is optimized. The planar3-RRR parallel manipulator is treated as a non-dimensional structure. By considering theworkspace of the parallel manipulator, the design plane of the non-dimensional parallelmanipulator is set up. Then, the atlases of global conditioning index, global velocity index,global stiffness index and force transfer index are presented and analyzed in the design space.Finally, based on the atlases of these four indices, the optimization of the planar3-RRRparallel manipulator is achieved by using the genetic algorithm.Secondly, the dynamic analysis of the planar3-RRR parallel manipulator is obtained inSimMechanics. The motion-actuated and torque-actuated dynamic simulation methods areproposed. The models of the two simulation methods are proposed before simulation. Thenthe advantage and disadvantage of the two methods are compared. The impacts of the loadand motion trail of the moving stage to the dynamics of the planar3-RRR parallelmanipulator are analyzed by using the motion-actuated simulation method.Finally, the planar3-RRR parallel manipulator actuated by the ultrasonic motor iscontrolled and tested. At the beginning, the point-to-point control model of the planar3-RRRparallel manipulator is built in Simulink. Then, the kinematic calibration and errorcompensation of the planar3-RRR parallel manipulator is obtained with the assistance ofLeica AT901B laser tracker. At last, the positioning of the planar3-RRR parallel manipulatoris studied, and the causes of the positioning accuracy are analyzed. The experimental resultshows the planar3-RRR parallel manipulator actuated by the ultrasonic motor has a goodpositioning accuracy.