Research On Lower-Mobility Parallel Robots For Automatic Assembly

The lower-mobility parallel robots have less DOFs(degrees of freedom), agile movement, simple structure and high degree of modularity.These types of robots can be applied in all kinds of fields such as electronics assembly, welding, sorting and painting.This study designed a new lower-mobility parallel robot named SCARA_Tau which combined the advantages of SCARA and Delta. This robot had three translational DOFs and all three drive motors were in a same vertical axis, its structure created a rotating work space like torus. This study did a brief research on the kinematics, dynamics, structural design and the optimization, all these work have provided theoretical basis for the engineering applications and optimization design of SCARA_Tau. The main work was as follows:Established a kinematics screw system based on screw theory and calculated its DOFs through the corrected Kutzbach-Grübler equation.Established the inverse kinematics model by using coordinate transformation. Compared the model with commercial analysis software's simulation results and the correctness of the model was verified. Analyzed the robot's workspace by the method of cyclic search. Calculated the robot's Jacobian matrix and analyzed the singularity configuration. Gained the equation of parasitic motion around the z-axis and provided the solutions to counteract it.Established the dynamics model by using principle of virtual work. Allotted the mass of the middle connecting rods to the actuating arms and moving platform, gained the expressions of simplified dynamics model to meet the demands of real-time control. Compared the dynamics model with commercial analysis software's simulation results and the correctness of the model was verified.Selected the key structure parameters which had impacts on workspace and flexibility of movement. Took the workspace and flexibility of movement as object functions, used genetic algorithm to find out the optimal structure parameters and the robot's performance was highly promoted in the meantime.Designed the structure of SCARA_Tau based on the optimal results, Designed the transmission systems inside the column and divided the column into three parts for the convenience of machining and assembling. Conducted finite-element analysis on SCARA_Tau's structure, verified the structural strength.