Research On A Kind Of Hybrid Planar Three DOF Hybrid-driven Mechanism

The concept of traditional mechanisms is limited to rigid mechanism system which has adetermined movement and is not controllable. Traditional closed-loop mechanism is oftendriven by a constant speed motor and the law of movement is determined by the size of themechanism. The output can only finish simple task and achieve a few track points on thetrajectory curve. So, it can not accurately complete any given movement. The main drawbackof traditional processing machinery is lack of flexibility and if change the output of the system,the size or type of the mechanism must be changed. However, this change usually bringshigher cost and troubles, even could not realize sometimes. In the conditions, thehybrid-driven mechanism is a good compromise in cost and performance of the traditionalmechanisms and modern robot mechanisms. In theory, it can combine the flexibility of robotmechanism with high speed, high efficiency, high bearing capacity of traditional mechanism,and provides a new idea for modern mechanical creative design.This task presents a new hybrid-driven mechanism based on the3-RRRmechanism.Through the application of Assur bar groups method and graph theory, the linkclassification and link composition are finished to get the most basic kinematic chain’sstructure of the planar3-DOF mechanism with full revolute pairs which has three symmetricallimb chains. Then topological embryonic graph is drawn using the interpolation point methodof the topological embryonic graph. The classification of the branched chains is done and thechains are inserted in the topology embryonic graph. Through the isomorphism analysis, the6configurations of kinematic chains are obtained. Finally, using a new graph theory descriptionmethod based on the link’s relationship the hybrid configuration of planar3-DOF is obtained,then the application research is proceeded. In the analysis of kinematics, modeling method of vector ring is commonly used toanalysis the motion of the traditional mechanism. This paper introduces various mathematicalmodeling methods, such as the quaternion method, dual matrix and the dual vector method. Inthe solution of kinematics equation, this paper compares the Wu Wenjun method, null bracketalgebra method,and so on. Through the comparing of these math methods, the D-H matrixmethod is selected to establish the mathematical model and complete the direct kinematicsanalysis of the hybrid mechanism because of its simple and clear.About the modeling constraints of the hybrid mechanism, this paper analyzes themovable property and singularity of the hybrid mechanism. Firstly, this chapter analyzes thedouble crank existent condition of the two independent closed loop based on the assemblyprinciple of the planar closed-loop linkage mechanism and the series and parallel singularityof the more important five bar loop are analyzed, finally the work space of this mechanism areanalyzed through the computational geometry.Lastly, the assembly model of the hybrid mechanism is established by Pro/E. Thekinematics and the trajectory simulation are analyzed in the mechanism module of Pro/E.Then for the collaborative simulation, the model is imported to Adams, the change rule of themotion parameters is gotten. The displacement, speed and acceleration curve of the trajectoryreference point C in this hybrid mechanism are obtained with the selected length size. Thenthe displacement curve is changed to a spline function by the spline curve fitting function ofAdams, a constant speed motor of the frame F points is deleted, the hybrid mechanism isdriven with two constant speed motor and the spline function of the point C. Through doingthese, the inverse solution of the servo motor rotation rule is gotten. With the research result,the theoretical foundation is established for the further study of this new hybrid mechanism,the design method for spatial multi-DOF hybrid driven mechanism is provided.