| The SCARA robot is a special kind of cylindrical coordinate type of industrial robots,whose movement is smooth and reliable in horizontal direction and stiff in vertical direction.With the characteristics of high speed,high precision,small operating space and high flexibility,it has been widely used in the field of assembly,handling,welding,etc.Although the repeatability accuracy of SCARA robot is high,the absolute positioning accuracy is low.On requiring higher accuracy and absolute positioning accuracy of the occasion,which limits it.To improve the absolute positioning accuracy of SCARA robot,kinematic parameter calibration is one of the main methods.In this paper,based on the SCARA robot system design,the method of improving the accuracy of kinematic parameters calibration is studied.In the first chapter,the research background and significance of the paper are expounded.The key techniques of SCARA robot system design and the main theories and methods of kinematic parameters calibration are discussed.On this basis,the main research contents of this paper are put forward.In the second chapter,the overall transmission scheme and basic technical parameters of the designed SCARA robot are determined.By using the module design idea,the joint structure of SCARA robot is designed.And the key components of the robot are selected.By using SolidWorks software,the 3D model of SCARA robot is established.By static analysis,the weak link is analyzed.And the stress and strain map of weak link are obtained,so as to check their strength.After the design is completed.According to the drawings,the machining,assembling and debugging are carried out.Which lays the foundation experiment for the further study of the kinematics of the robot.In the third chapter,the control system hardware of SCARA robot is mainly based on PC and motion control card.Which mainly includes PC,PMAC four-axis motion control card,driver and servo motor.The software system platform is based on Windows 7 system and carried on modular design.Through a unified interface,each module communicates with PMAC.With Visual Studio 2015 as a development tool,control system software design of the robot is completed in the paper.By DH method,the kinematics model of SCARA robot is established in the fourth chapter.Based on the forward kinematics,the inverse kinematics equation is deduced.Which lays the foundation for the motion control and trajectory planning of the robot.Using Robotics toolbox of MATLAB,the robot’s graphical simulation platform is compiled to verify the correctness of the kinematics model of SCARA robot.By experiment,the kinematic parameter calibration method of SCARA robot is verified in the fifth chapter.According to the structural characteristics of SCARA robot,a calibration method based on SVD is put forward to calculate the DH kinematic parameters.The calibration method does not need high precision measuring instruments.And according to the cylinder size of the end-effector,the four-hole calibration plate is precisely machined.Using the calibration software,we recorded the size of the arms pulse when the cylinder insert the four holes.which can calculate the size of the arms length and the small arm joint zero pulse.The calibration software is programmed with MATLAB.And the kinematic parameters of the self-developed SCARA robot are calibrated,the calibration accuracy was evaluated.The causes of the error were analyzed and the precautions in the calibration process were put forward.Finally,the main work of this paper is summarized,and the future research is forecasted. |
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