Trajectory Planning And Position Force Coordination Control In Multi-robot Cooperative Welding Process

With the development of industry and advances in robotics,traditional single robot systems are not sufficient for today's increasingly diverse flexible automation production needs.In order to meet the requirements of task complexity,operational intelligence and system flexibility,multi-robot collaboration systems have been gradually promoted and applied in industrial environments.Compared with a single robot,the multi-robot collaboration system has more work ability,a larger working space,a more flexible system structure and organization,and is one of the current research hotspots.The research of multi-robot collaboration in the field of welding is carried out in this thesis,and the task of collaborative space weld welding is completed.The key scientific issues in the multi-robot collaborative welding process are studied.Compared with the traditional welding robot + positioner welding station or a cooperative system composed of two industrial robots,multi-robot(three or more)cooperative welding has more advantages,but it also brings more for complex control problems.This paper focuses on these difficult issues,the main contents of which are as follows:(1)In order to meet the task constraints and welding process requirements of complex weld welding in the continuous welding process,the handling robot must constantly change the position of the clamping workpiece to ensure that the welding point is always in the ideal welding position,welding The robot must also constantly adjust the position of the welding torch to ensure that the welding torch meets the welding requirements.This process requires that the handling robot,the handling robot and the welding robot meet certain posture constraints.In addition,in the collaborative welding process,the layout problem of the initial welding position needs to be considered.If the initial welding position is improperly selected,the entire welding process may not proceed smoothly.Aiming at the above difficult problems,this paper proposes a multi-robot planning method for the "strategic planning" of the operated object,and considers the optimal layout of the initial welding position for the first time,and establishes a mathematical model for solving the optimal layout according to multiple performance indicators.The optimal solution is solved by the optimization algorithm,and the solution result is integrated into the "hierarchical planning",and finally the operation trajectory of each robot is obtained.The proposed planning algorithm not only solves the difficulties of complex coordinate system transformation,but also considers the welding process requirements and pose constraints.(2)As the welding process progresses,the workpiece held by the transfer robot is gradually welded into one body,and the transfer robot and the workpiece form a closed chain system.In the actual control system,there are often calibration errors or external disturbances.These factors will cause time-varying trajectory deviations in the cooperative motion of the robot end.The dynamically changing trajectory deviation will cause huge losses between the robot and the workpiece,the robot and the robot.Internal force,improper control may result in damage to the workpiece or robot to be welded.Aiming at the above difficult problems,this paper proposes a symmetric internal and external impedance strategy for the manipulated object,and for the first time considers the dynamic and unknown trajectory deviation caused by external disturbance and calibration error in the actual control system,and proposes adaptive variable impedance.The control strategy is used to compensate for the unknown interference generalized forces caused by dynamically varying trajectory deviations.(3)In order to systematically study the scientific problems in the multi-robot collaborative welding process and verify the relevant theoretical research results,the multi-robot cooperative control system was independently developed by using the embedded PC+ servo bus architecture,and a typical multi-robot collaborative welding system was further established.Simulation and physical experiments were carried out on the proposed multi-robot trajectory planning algorithm and the two-arm position force coordination control algorithm.On this basis,the above algorithm was applied in the multi-robot cooperative welding experiment.For the first time,the welding experiment of the pipe-to-saddle saddle curve weld was successfully completed on the cooperative welding system consisting of three industrial robots.In a word,in view of the difficult problems in the multi-robot collaborative welding process,this thesis conducts in-depth research from the trajectory planning and the dualposition position force coordination control in the multi-robot collaborative welding process,and theoretically proposes the object-oriented and considers the optimal.Multi-robot trajectory planning method for initial welding pose layout and dual-position position force coordination control method based on symmetric adaptive variable impedance,and multi-robot with space complex welds completed based on open multi-robot controller independently developed Collaborative welding tasks.