Kinematics Analysis And Dimensional Synthesis And Structural Design Of 4-PRP_aU Parallel Manipulator

With the features of simple structure,less drive,simple control and low manufacturing cost,less degree of freedom(DOF)parallel mechanism is gradually becoming the research hot spot of parallel mechanism in recent years.Particularly,the end actuator is a parallel mechanism that has 3 degrees of freedom of translation and 1 degree of freedom of rotation(for short 3T1R),which is increasingly and widely used in the field of industrial manufacturing.This paper proposed a new 3T1R parallel mechanism(4-PRPaU parallel mechanism)and analyzed its configuration,kinematic,performance,scale optimization,and structural design to lay the foundation for 4-PRPaU parallel mechanism application and product sorting.The main contents of the article are shown as follows:Firstly,the configuration analysis of 4-PRPaU parallel mechanism was carried out.The corresponding branched-chain coordinate system was established,the screw theory to give the kinematic screw of all the kinematic pairs in the branched-chain coordinate system was used and the reverse screw was also found.According to the improved Grubler-Kutzbach formula,the calculation results showed that the end actuator 4-PRPaU parallel mechanism has three degrees of freedom of movement and one degree of freedom of rotation.The rationality of the selection of driving pairs is further analyzed.Secondly,kinematics analysis of 4-PRPaU parallel mechanism was accomplished.Using the coordinate transformation matrix and the mechanism condition of rod length,a 4-PRPaU parallel mechanism position forward and inverse solution model was established.The forward solution model of the mechanism position was transformed into an unconstrained optimization equation and solved by the Differential evolution algorithm.During the process of solution,an adaptive escape differential evolution(AEDE)algorithm with a strong global search ability was proposed,which improved the optimization efficiency of the DE algorithm and avoided the shortcomings of being easily trapped into a local optimum.Through the numerical example of 4-PRPaU parallel mechanism,all all high-accuracy position collections were obtained by using the AEDE algorithm,and the correctness of the forward position solution was verified by the inverse solution of the mechanism position.In the course of research,in order to verify the performance of the AEDE algorithm,the AEDE algorithm was applied to the forward position solution of a 3-RPS parallel mechanism and compared with the DE and Particle swarm optimization algorithms.The results showed that the performance of the AEDE algorithm is better than the comparison algorithm.In order to verify the correctness of the kinematics model of the mechanism,the vector method was used to establish the speed and acceleration mapping relationship between the input and output of a 4-PRPaU parallel mechanism by using the mechanism condition of rod length.The Matlab software was applied for the numerical simulation,and drawing the displacement,velocity and acceleration curves of the mechanism.At the same time,in order to verify the correctness of the numerical simulation of Matlab software,a corresponding three-dimensional model of the mechanism was established,and Adams software was imported for motion simulation.The driving function in the numerical simulation was used as the driving input for Adams motion simulation,and the corresponding displacement,speed and the acceleration curve were obtained.The results showed that the Adams motion simulation curve is consistent with the Matlab numerical simulation curve,which verifies the correctness of the models of forward and reverse solution,velocity,and acceleration,and lays the foundation for the subsequent performance analysis of the mechanism.Lastly,the performance analysis of 4-PRPaU parallel mechanism was conducted.The performance analysis and scale synthesis of 4-PRPaU parallel mechanism were carried out by using the motion/force transmission performance index.Based on the screw theory,the establishment of the input transfer index and the output transfer index of the mechanism were established,and the definition and numerical calculation method of the effective transfer workspace of the mechanism rules were given.With the maximization of RETW radius as the optimization goal,an optimal design model of mechanism scale parameters was established,and the accelerated artificial bee colony algorithm was used to solve the problem.An example of mechanism parameter optimization was given,and the results showed that the model and algorithm are feasible.Finally,the rod length results obtained by the scale optimization were used to design the structure of the mechanism for a three-dimensional virtual prototype.Among them,it mainly includes the selection of purchased components(motor,screw,linear module,bearing);the structural design and overall assembly layout of the PRPaU branch chain,fixed platform end effector.The research work in this paper lays a theoretical foundation for the development and practical application of 4-PRPaU parallel mechanism physical prototype,and can also extend the optimization design method of scale parameters in this paper to other parallel mechanisms.