Optimal Structural Size And Analysis Of Motion Characteristic For 3-RCU Parallel Manipulator

Parallel mechanism is one of the hot topics in the field of mechanism. It has a wide application prospect in the field of medical science, biology, aerospace et al. This paper chiefly focuses on the 3-RCU parallel mechanism. It is composed of three identical RCU branches and is able to move in three space directions. The paper mainly studied the kinematics and microkinematics, singular configuration, workspace, visual motion and the design of its control system on the 3-RCU parallel mechanism.Using the traditional calculation method and spiral method to calculate the degree of the 3-RCU parallel mechanism respectively, the results showed that the DOF of the 3-RCU parallel mechanism is three, verifying the correctness of the two methods. The movement situation of the 3-RCU parallel mechanism was analyzed based on the screw theory, getting that the 3-RCU parallel mechanism has a movement along the Z axis. Establishing driving model and constraint model respectively, it achieves the driving equations and constraint equations that can reflect the position relationship between the input and the output of the 3-RCU parallel mechanism.Using differential approximation algorithm to analyze its micro-kinematics can get the mapping relationship between the input and the output of the 3-RCU parallel mechanism in the case of micro motions.Calculate the constraint jacobian matrix, kinematic jacobian matrix and the complete jacobian matrix of the 3-RCU parallel mechanism. This paper also studied the singular configuration condition and species of the 3-RCU parallel mechanism based on singular configuration judge criterion. It obtained that there are 4 constraint singular configurations and 25 kinematic singular configurations when taking the prismatic pair in the cylindrical pair of the 3-RCU parallel mechanism as the active pair.Established the simulate frame of the 3-RCU parallel mechanism,inputted appropriate drive parameters and conducted simulation, then written program to collect the set of all point of the moving platform center, making these points displayed in the same 3D coordinate. This paper also analyzed the work space point chart after and before the size optimization, getting that the work space figure is scattered and the jump range is bigger, and the work space figure gets intensive.Using Sim Mechanics to realize the visualization simulation movement of the 3-RCU parallel mechanism, the results verified the correctness of the motion analyzed and it also examined the 3-RCU parallel mechanism works properly and there is no interference phenomenon in the branches. The control system of the 3-RCU parallel mechanism was designed by using Matlab software. By adding PID control and adjusting its parameters, we obtained different effects on the control system when increasing the value of PK and reducing the value. The better one control position variation figure was taken as position tracking figure of the moving platform.The research of this paper is helpful for the kinetic analysis of the 3-RCU parallel mechanism, also contributes to the design and development of prototype. Also, it provides the theoretical foundation for the research of the similar parallel mechanisms.