Research On Double NURBS Curve Milling For 6DOF Series Robot

Since the 1950 s,the serial robot has been applied to actual production.Due to the characteristics of simple operation,low price,and easy disassembly,serial robots have been widely used in various industries,and a variety of industrial robots designed for different working conditions have been derived,such as spraying robots,assembly robots,handling robots,carving robots,etc.In terms of mechanical processing,due to the high degrees of freedom and flexible processing posture of serial robots,serial robots can replace multi-axis numerical control machine tools when processing soft materials,such as wood,foam,nylon,etc.,and have great advantages when processing complex curves and curved surfaces such as impeller blades.The processing work can be completed by requiring reasonable planning of the robot's processing posture and processing path.In the design of curves and surfaces,NURBS(Non-Uniform Rational B-Spline)is an excellent modeling design method.At present,some operating systems of NC machine tools can directly perform NURBS interpolation calculation,but NURBS interpolation for serial robots is still a problem under study.An Anchuan MOTOMAN-UP6 industrial robot is used to analyze the interpolation points and the control of the robot's end posture in the process of double NURBS curve processing in this topic.Meanwhile,the control method of the end tool's cutter axis direction is analyzed.The industrial robot can realize the processing of double NURBS curve model.The node insertion and stepup method in the process of double NURBS curve is also studied.Firstly,the forward and inverse kinematics of UP6 robot is solved to handle the coordinate transformation problem of the robot in processing,and the inverse kinematics of the robot is also solved.Since this topic mainly studies the milling problem of robots,it is necessary to reasonably plan the robot's position and posture to ensure the processing.Then MATLAB software is used to verify the correctness of the forward and inverse kinematics algorithm of robots.Secondly,NURBS curves and surfaces are studied and analyzed,various parameters of NURBS curves and surfaces are calculated,and interpolation points on the surfaces are calculated accordingly.Then,according to the definition requirements of dual NURBS curves,node insertion algorithm and step-up algorithm of NURBS are calculated,which makes the design of dual NURBS curves more convenient and reasonable.According to the characteristics of flexible movement and high degree of freedom of serial robots,the cutter axis direction is kept on the straight generatrix of the ruled surface of the double NURBS curve.Therefore,when the double NURBS curve model needs to be processed,the cutter axis direction of the processing tool needs to be controlled,and the curved surface points generated by NURBS algorithm can be directly used as interpolation points of the robot.However,it is found that the method has high requirements on the processing environment,and the interference between the tool and the workpiece and the interference between the end tool and the robot will occur during the processing.Hence,it is necessary to select an appropriate processing method to ensure the safe processing before processing.Meanwhile the speed control during the processing is analyzed according to the actual processing situation.Finally,the generated program is imported into the robot control cabinet for actual processing.Due to the insufficient rigidity of the robot,the experiment uses polystyrene high density foam board as the material to analyze the robot state and processing results during the processing.The robot runs smoothly during the processing and the processing results are basically consistent with the design model,which verifies the effectiveness and practicability of the algorithm in the experiment.