Structural Design And Analysis Of A Novel Reconfigurable Parallel Robot

In the modern production process or in many high-risk or special occasions,mechanism are required to have good adaptability and variable structural features,and even the freedom of the structure is required to be variable to meet the requirements of different processes,different conditions and different tasks.Based on backgrounds above,this paper presents a design method of reconfigurable parallel mechanism with kinematic bifurcation based on the Screw theory.Then designs a novel 3-R(P)RPS reconfigurable parallel mechanism and select it as the subsequent study mechanism.Firstly,this paper transforms the problem of searching the kinematotropic closed-loop chains with motion bifurcation into the rank-seeking problem of parametric matrix through the Screw theory,and obtains the structural features of kinematotropic chain by means of the mathematical rank-reduction method.From this point of view,we can get some conclusions from the existing kinematic bifurcation chain.By integrating singular closed-loop chains and serial limbs with fixed degrees of freedom(DOFs),hybrid limbs and subsequently,a novel type of 3-R(P)RPS reconfigurable parallel mechanism are constructed.By using the Screw theory,the moving platform of this mechanism proved can have three degrees of freedom,four degrees of freedom,five degrees of freedom and six degrees of freedom.We can determine the organization's assembly conditions and create the correct there-dimensional modeling by Creo.Then,the kinematics of the 3-R(P)RPS parallel mechanism were analyzed,including the decoupling property,the forward and inverse kinematic model of the mechanism,the velocity analysis and acceleration analysis of the mechanism.The mapping relationship between the position of moving platform and the position of the drive,as well the velocity of the moving platform and the velocity of the drive,as well the acceleration of the moving platform and the acceleration of the drive,which lays theoretical foundation for the subsequent research.Then,the performances of the mechanism were analyzed,including workspace analysis,singularity and dexterity analysis,stiffness analysis.Using Mathematica software to get the mechanism's reachable workspace and the new representation method is used to express its workspace with the mechanism inverse kinematic.Using the velocity Jacobian matrix,to get the Jacobian condition number,and the stiffness matrix can be established by Jacobian matrix and static stiffness analysis was carried out.Then,taking the workspace performance point and stiffness as two objective functions,the genetic algorithm is used to optimize the structural parameters of the mechanism.The optimal structural parameters of the two objective functions under the same weight are obtained.Finally,the kinematics simulation of 3-R(P)RPS parallel mechanism was carried out by constructing a virtual prototype modeling via ADAMS.The change of the mechanism under different rotational and eccentric axes was verified with theory and calculation results.Trajectory planning of the moving platform of the mechanism completed the motion simulation based on the task of sanding the U-shaped groove,further verifying the reliable movement capability of the 3-R(P)RPS parallel mechanisms.