| Two degree-of-freedom translational parallel robotic mechanism,which possesses the least mobility and the simplest structure among the parallel mechanisms,has good application prospect in the planar machining equipments.In this paper,type synthesis method of the uncoupled two DOF translational parallel robotic mechanisms with three limbs is systematically studied.Kinematics,dynamics and optimal design of a novel 2-CPR/RRR parallel robotic mechanism are researched in detail.A novel type synthesis method for the uncoupled palnar translational parallel robotic mechanisms with one pure constraint limb is presented in this dissertation.According to the actuation wrench screw theory,structural synthesis criterion of the actuated limbs is established.Meanwhile,structural synthesis law of the constraint limb is set up based on the constraint screw theory.Then structural synthesis of two kinds of limbs has been completed.Finally,type synthesis and innovative design of two DOF translational parallel robotic mechanisms with three limbs are realized by using the approach propsed.3058 kinds of uncoupled planar translational parallel mechanisms are obtained,including 78 kinds of mechiansm without the idle joints.Kinematics and singularity of the novel 2-CPR/RRR parallel robotic mechanism are studied.Based on the screw theory,the degree of freedom and output motion characteristics of the mechanism are analyzed.The position,velocity and acceleration equations are dirived by vector elimination and derivation method.Kinematic simulations are performed by use of ADAMS and MATLAB softwares.Simulation results show that the theoretical analysis is correct and effective.In addition,the singularity of the mechanism is analyzed.Statics and dynamics equations of novel 2-CPR/RRR parallel robotic mechanism are established.Based on the principle of virtual work,the static equations of the mechanism are established,which reveals the relationship between the actuated forces and the external load on the moving platform.The dynamic models of the mechanism are put forward by means of the Lagrange Equation.Using ADAMS and MATLAB softwares to simulate the statics and dynamics of the mechanism the correctness of the theoretical analysis is verified.Workspace analysis and optimal design of the novel 2-CPR/RRR parallel robotic mechanism are analyzed.The workspace shape of the mechanism is drawn by use of the search method.The influence of structural parameters on the workspace size is analyzed.Taking the workspace maximization as the objective function,the structure sizes of the mechanism are optimized based on the particle swarm optimization.The research results of this dissertation will contribute to improve the type synthesis method of the uncoupled parallel robotic mechanisms.Furthermore,this work also provides the theoretical foundation for the innovative design and prototype development of the uncoupled two DOF translational parallel robotic mechanisms with three limbs. |
