Pose Precision Analysis And Modeling Of The Serial Robot

The pose precision of the robot is represented by the error of the robot’s end-effector. It is an important indicator to reflect the performance of the robot, as well as the guarantee for the robot’s normal operation and meeting the requirements of the high precision duty. This paper is taken a five Degree-of-Freedom (5-DOF) serial robot as the research object. From the point of multiple factors of the static error and the dynamic performance of the serial robot, a series of simulation analyses and academic research are achieved. The model of the serial robot’s static error, the kinematic model and the dynamitic model of the serial robot are established. To analyze the effect of main factors on the serial robot’s pose precision, this paper shows how to test the pose and path characteristics of robot based on the non-contact three-dimensional laser tracing measurement system. The main content of this current research includes:(1) Link coordinates of the5-DOF serial robot are set up by Denavit-Hartenberg method. Simultaneously kinematic model of serial robot is established through homogeneous transformation. Based on this, the pose error of the serial robot resulting from static errors is analyzed. The static pose error analytic model of the serial robot is developed by using "small displacement perturbation method". The mechanism reliability is considered as the evaluation guidelines of pose precision. The errors of links parameters influence the robot static pose precision, which can be obtained by using Monte Carlo method. Meanwhile that which joint has the greatest impact on the static pose precision can be received.(2) Based on the contact dynamics theory, a revolute clearance joint model for journal and bearing is presented according to the practical related motion. The discriminate equation which decided contact and separation is formulated. The normal contact force model and tangential friction model between journal and bearing are modeled. Based on the clearance vector model of revolute joint clearance of the5-DOF serial robot, the method that a massless and variable-length link instead of clearance is proposed. The kinematic and dynamic analyses of the serial robot, which is added the generalized degree of freedom, are accomplished in consideration of the revolute joint with clearance based on the multi-body dynamic theory. The kinematic and dynamic models of the serial robot with the clearance joint are presented.(3) The virtual prototyping analysis of the5-DOF serial robot with the clearance joint is implemented. Three dimensional model of the5-DOF serial robot is established by using Pro/E. Then, the total workspace and flexible workspace of the robot are simulated based on the method of Monte Carlo simulation. At last, the kinematic and dynamic analyses are implemented based on the virtual prototype analysis of the serial robot by the ADAMS code. The kinematic and dynamic characteristics of the serial robot are researched in different clearance sizes. By parameterzing the size of clearance, the impacts on kinematic and dynamic characteristic in different clearance are achieved.(4) To overcome the problem of measuring the pose precision of the serial robot, laser tracing measurement system is proposed. The principle of non-contact laser tracing measurement system for the5-DOF serial robot is described in detail. Take pose repeatability, pose accuracy, path velocity accuracy, path velocity repeatability, path velocity fluctuation as the precision evaluation index, the measurement scheme and result by using non-contact laser tracing measurement system are showed.