Research On The Dynamic Dimensional Synthesis And Compliance Control Of A3-PPSR Precision Parallel Robot

Precision parallel robots have high stiffness and position accuracy. Withprecision driver such as piezoelectric motors, precision parallel robots have a widerange of applications in precision scale operations. While the precision parallelrobots work, they often have contact with the environment objects, therefore theyare no longer an independent motion control systems. In this situation, the precisionparallel robots need to have a certain flexibilty to adapt the environmental objects.In this paper, the dynamic dimensional synthesis and a application of comliancecontrol strategy in precision parallel robot is studied.3-PPSR precison parallel robots have several kinematic closed chainconstraints, resulting in that the inverse kinematics is easy and kinematics isdifficult. By using configuration constraints and vector theory, inverse kinematicssolution and jacobian matrix are proposed. With the Newton iterarive method, thenumerical solution of direct kinematics is obtained. The dynamic model of theparallel manipulator is provided in detail based on the inverse kinematics.Global manipulability index describe the kinematic performance, but can notreflect the dynamic performance of parallel robots. A novel global dynamicperformance index of parallel manipulator defined by the maximum driving torqueof a single active joint is proposed as the optimization objective function. A set ofoptimized dimensional parameters of the parallel manipulator is obtained forachieving a good dynamic performance throughout the entire workspace of themanipulator. On the basis of optimal key size of parallel robot, the movingplatform、transfer parts and rods are designed. Also, the stiffness and modal analysisof the parallel mechanism are presented by Abaqus software.The piezoelectric motor driver control is the basis of precision parallel robotposition control, with the high resolution grating position feedback components, asaturated integral separation PID position controler is designed. On the basis ofkinematic model, the position control of3-PPSR precision parallel robot is studied.The position control performance is verified by measuring the repeatability andresolution.The paper proposed impedance control of compliance control method by usingthe six axis force/torque sensor installed in the moving platform of3-PPSRprecision parallel robot as a force feedback. Environment parameters are verydifferent for different environmental objects and not esay to obtain accurately. Inorder to avoid dependence on environmental parameters, adaptive impedancecontrol are implemented in the3-PPSR precison parallel robot.