Research And Analysis Of A 7 DOF Hybrid Manipulator

In the face of complex surface machining problem,the machining precision,working space and flexibility of the machining machine are required to be higher.To solve the problem of complex surface machining by introducing multiple free manipulators,comparing the advantages and disadvantages of series and parallel mechanisms,choosing a series-parallel hybrid structure with both advantages,and increasing the kinematic accuracy and stiffness of the parallel mechanism by adding closed loop to the parallel mechanism is a direction worthy of research and discussion.Therefore,it is of great significance to design and research a novel hybrid mechanism with multi-degree of freedom with closed loop.This paper studies and discusses the mechanism from the following aspects.Using the Solid Works 3D modeling software to draw a new hybrid organization simplified model,parallel and series of hybrid mechanism part coordinate system is set up respectively,are derived in parallel parts closed-loop vector equation and calculate the parallel position inverse solution,using the D-H parameters method to find out the location of the positive and negative solution of the transformation matrix of the structure,location of the whole structure of the solution.According to the set mechanism parameters,rod length conditions,restricted motion pair and other constraints,the workspace of the mechanism is planned.When modeling the dynamics of the whole mechanism,the velocity,acceleration and corresponding mapping relations of each part of the parallel mechanism were obtained through the vector relations,and the gravity vectors,inertial forces and inertial moments of each part were obtained.The dynamics mathematical model of the parallel mechanism of the hybrid manipulator was obtained by Principle Of Virtual Work.By means of D'Alembert's Principle,the force balance equation of 2R mechanism is written,and the relationship between the external forces and torques at the end points in series and the equal force and equivalent torques at the reference points of the moving platform is obtained.Finally,the mathematical relationship between the external forces and torques at the end of the whole hybrid mechanism and the driving force of the branch chain moving pair is obtained.The virtual prototype model of the hybrid mechanism was directly established in ADAMS,and the spline curve of the moving pair was obtained by driving the hybrid mechanism with reference points according to the motion trajectory.The spline curve of the moving pair was transformed into the data input driver,so as to realize the kinematics and dynamics verification simulation of the hybrid mechanism virtual prototype.