Comprehensive Analysis And Control Scheme Of A 3-DOF Parallel Manipulator Supporting Secondary Mirror Used In Laser Beam Focusing

With the background of “863” sub-Project “XX LASER BEAM FOCUSING XX”, the paper is about the research and design of the overload 3-DOF parallel mechanism to support the secondary mirror used for laser beam focusing.First, A scheme that designing a mini 3-PRS parallel robot without any piezoelectric ceramic motions and which can realize one translational and two rotational motions to support the secondary mirror, is proposed; build the 3-D model of the 3-PRS parallel mechanism and traditional Euler angle for describing the motion of moving platform is adopted, and based on that, kinematic model of a 3-DOF mini mechanism is built to analysis its direct and inverse kinematics performance including Jacobian matrix generation and solve the problem of accompanying motions. Furthermore, qualitative analysis of singularity and quantitative analysis of the reachable workspace of the mechanism are given by making use of multi-rigid-body system ADAMS. Besides, some methods are given to eliminate singularities by mechanism design. Finally, the synthetically analysis lays the foundation for kinematic design.Second, dynamic model of the mini 3-PRS parallel manipulator was built. The optimal inverse dynamics modeling with principle of virtual work has been derived by introducing a mass distribution factor of link legs and by comparing the forces deviation of simulation result between the mathematic modeling algorithm and the virtual prototype in ADAMS. Furthermore, the stiffness model of the lead-screw system and links system was established and the resonance frequency was analyzed.Finally, based upon the established model, three control systems, including PID control, Force/Torque and passivity-based control have been implemented on the mini 3-PRS parallel manipulator. Then, control accuracy of the robot was obtained by combining ADAMS/Control with MATLAB/Simulink. Moreover, the quality of laser speckle was evaluated by applying the mini 3-PRS robots into an actual optical system The derived results prove that a mini 3-DOF mechanism can fulfill the design requirement of the structure for supporting secondary mirror.