The Synthesis And Performance Analysis Of A 2UPU/SPR Parallel Mechanism

As a kind of robot operating mechanism,parallel mechanism with the high precision,strong carrying capacity and lower movement inertia,has become a hotspot of mechanism research recently.In this paper,the kinematics,workspace,performance analysis and size optimization of 2UPU/SPR 3-DOF parallel mechanism are studied.The specific contents are presented as follows:In this paper,the combination principle of motion branching and the configuration synthesis of parallel mechanisms are studied.A 2 UPU/SPR parallel mechanism is proposed by using the combination of under-constrained active branches,which can realize two movements and one rotation in space.The degree of freedom of the mechanism is analyzed by the modified Kutzbach-Grubler calculation formula.Based on the space position vector method,the position equation of the mechanism is established.The Jacobian matrix and Hessian matrix are derived,and the kinematic position,velocity and acceleration of the mechanism are numerically simulated.The workspace of the mechanism is solved according to the constraints of joint space.The singularity of the parallel mechanism is analyzed by Gosselin singularity analysis method.The dexterity evaluation index is introduced and the dexterity of the mechanism in different postures is analyzed by numerical method.Based on the principle of virtual work,the rigid body dynamics model of the mechanism is established,and the dynamic inverse problem is solved.The variation of the driving force of each branch under the given motion law is obtained.Based on the screw theory,the input motion screw,the transfer force screw and the output motion screw of the mechanism are solved.On this basis,the local and global motion/force transfer performance of the mechanism is analyzed,and the performance spectrum under relevant parameters is obtained.Taking the global motion/force transfer performance index as the optimization objective,the structural dimension parameters of the mechanism are optimized to obtain the optimal dimension space of the mechanism when the size of the mechanism satisfies the geometric conditions.By comparing the performance spectrum before and after optimization,it can be seen that the transmission performance of the mechanism has been greatly improved.Finally,according to the characteristics of the parallel mechanism combined with the mobile platform,a Chinese massage robot is proposed,which can realize a variety of massage manipulation operations.