Research On Real-time Motion Of Rod-type Parallel Machine Tool Based On Branch Angle Information

Because of the strong mechanical coupling between the driving rods of parallel machine tools,how to quickly find its kinematic solution has always been a hot and difficult problem in real-time motion control of parallel machine tools.In order to accelerate the speed of kinematics solution,this paper studies a real-time motion control method of rod-type parallel machine tool based on the angle information of branch chain.The main elements are as follows:Firstly,the kinematics calculation method of rod parallel mechanism with different degrees of freedom is studied by using the angle information of branch chain.A method of measuring the angle information of the branch chain and obtaining the direction cosine of the branch chain by adding rotating sensors to the hinges of the parallel mechanism is proposed.The mapping relationship between the displacement increment of moving platform and the feed of each branch drive rod in Cartesian coordinate system is established.Secondly,taking the six-degree-of-freedom parallel mechanism as an example,the kinematics solution process of each branch chain with additional angle sensors is simulated and the pose error is analyzed.Compared with the Newton-Raphson numerical iterative method without additional angle information,the accuracy and efficiency of the new method are verified.Further,an algorithm is proposed to add only an angle sensor at a specific branch chain to obtain a unique positive solution by eliminating the order of elements,and its feasibility and efficiency are verified by numerical examples.And then,taking the Three-Translational C-shaped gantry parallel machine tool as an example,the real-time motion control method of parallel machine tool based on branch angle information is studied.In view of the structure of machine tool,the formulas of kinematics forward solution and velocity inverse solution based on the angle information of branch chain are derived,and the mapping relationship between the displacement of moving platform and the feed of each driving rod of machine tool in Cartesian coordinate system is obtained.The feasibility of the control scheme is verified by simulation.Lastly,the feedback system of angle information measurement of branch chain is constructed on the C-shaped gantry parallel machine tool,and the algorithm of solving kinematics of machine tool based on angle information of branch chain is embedded in the CNC module of parallel machine tool PA numerical control system.And the debugging of the machine tool is completed.