Research On Automatic Conveying SCARA Robot For Large Area Screen Printing

To improve the yield of large area screen printed solar cell sheet,the shape measurement laser microsystem is used to detect the printing quality.Since flexibility and automation level of the existing single degree slide is low,it is difficult to adapt to flexible working environment,the main task of this paper is to design a lightweight robot,also meet the fast accurate and stable requirements on the solar cell sheet conveying.First,based on the compare of the existing robot,the SCARA(Selective Compliance Assembly Robot Arm)with fast motion speed and high location accuracy is selected according to the light weight and fragile characteristics of the battery sheet in loading and unloading.Taking into account the openness of the system and the special needs of operation,this paper studies the autonomous design of the SCARA under the requirements of this work.According to the requirements of the work,a compact and lightweight SCARA is designed and manufactured.The joint drive adopts AC servo motor,and the transmission structure is realized by harmonic reducer,ball screw spline and timing belt and pulley.According to the performance requirements,the speed and the driving torque demand of each joint of the robot are calculated,and the specifications of the drive system are determined.According to the requirements of the opening system,the control scheme of the PC+DMC is adopted and the circuit design of the control cabinet is completed.A flat end effector with vacuum pneumatic system is designed for the pickup of thin piece parts.By the analysis of robot kinematics,the working space of the robot is drawn by the positive solution.Based on the trapezoid velocity profile,the Cartesian space line trajectory motion of the robot end is realized.The NURBS curve path is used for trajectory planning to achieve a smooth and continuous feeding process.In addition,we simulate in MATLAB to analyze the change rule of driving torque under the trapezoid velocity profile based on Newton-Euler method,verify the drive ability of motor,check the load capacity of reducer,and provide theoretical guidance for good dynamic performance.In order to improve the positioning accuracy of the robot,using laser tracker as measurement means,the geometric model error of the robot is calibrated and compensated by the least squares method.After the calibration is completed,the accuracy of the average position of the robot is increased by 58.74%.And the positioning precision of the robot is evaluated.The position accuracy of the robot end reaches 1.19 mm,and the repeatability of the position reaches 0.03 + 0.07 mm.The motion checking experiment shows that the robot can return the horizontal distance of the 300 mm in 1s.Finally,based on the NURBS curve path,the robot's conveying experiment is completed,and the performance of the robot is verified.