Trajectory Planning Algorithm Of Welding Robot With Gantry

How to improve the industrial automation and intelligent level is a permanent topic in recent years.Nowadays more and more large scale manipulators are used in industrial processes.They take place of manual labor to complete tasks in wide working space.This paper designs trajectory planning algorithm for welding manipulators with gantry used in ship assemble line,which shows low efficiency of labor and unstable technological level of manual work.In this field a lot of job positions are replaced by intelligent machines.There exists several problems,such as analysis difficulties caused by complex structure.Meanwhile it's hard to make choice among more than one solutions derived from redundant degree of freedom.Gantry's movement with low accuracy also makes great effect on manipulator location.Besides,there are contradictions between rapid calculation and simplifying procedure.Taking requirements of operation quality into consideration,the goal of controller design is clear after model structure and material character analysis.Based on those existing theoretical achievement,a trajectory planning algorithm is proposed by taking advantages of model predictive control.The main work of this paper can be summarized as follows:(1)Choosing trajectory algorithm type of welding manipulator system with gantry.At first this paper analysis problems during motion control for this kind of manipulator.Due to the complex structure of system,it's hard to make accurate description of manipulator.The whole manipulator system has 17 independent axis in all,which brings serious redundancy.There are many constraints lead by the mutual coupling between every single module in various industrial procedure.Despite the complexity of technological requirements and uncertainty of working environment,the algorithm need to be adjusted frequently in real time.Instead of using pre-existing algorithms with apparently shortcoming,this paper choose model predictive control to solve those problems.(2)Establish kinematic model for the double arm welding system with gantry.The different degree of vertical deflection on the beam,which is caused by the two hanging links' moving horizontally,will exercise influence on the two vertical degree of freedom of manipulator.Hence,the flexibility should not be ignored in modeling.After analyzing material mechanics,calculation formula for the deflection of simply supported beam under two independent concentrated load is deduced by using superposition principle.The equations are tested by simulations in Ansys software.Since the two arms have mutual effects on beam only,they can be decoupled as two 9-degree-of-freedom manipulator.Next,coordinate systems for each of the axes are established and the Denavit-Hartenberg(D-H)model is built according to the structure of joints and links.The differential kinematics equation,Jacobian matrix,is used to make connection between each axis and the end-effector.Thus an accurate kinematics model of manipulator system is presented.(3)Design trajectory planning algorithm for welding manipulator system with gantry.The model established before is simplified to be linear and low-order,for following algorithm design.And Increment Control is used to eliminate static errors.All of the joints are classified into different movement priority according to their motion range and positioning accuracy.The redundancy problem can be solved by setting different weight for control variable of each joint in optimization problem.In addition,for various setting points,different weighting selections are considered by analyzing joints' motion characteristics.Meanwhile,rolling optimization style of MPC scheme makes it possible to online continuously make trajectory planning with updated information.At last the algorithm is tested in SIMULINK platform of MATLAB.(4)Design control system for objection debugging.Appropriate equipment is selected to establish the hardware part of control system.A series of function modules are designed to complete the software part of control system,which includes three-dimensional calibration module,mission planning module,human interaction module,trajectory planning module,servo tracking module and three-dimensional exhibition module.Each module's function and the operation procedure under various mission types are introduced in detail.The results demonstrates that this algorithm can not only solve redundancy problem,but also make appropriate trajectory planning according to different kinds of setting points,by taking full advantage of joint characteristics.