Francis G. King

Vision Guided Robots For Automated Assembly

A vision guided robot for assembly is defined to be a robot/vision system that acquires robotic destination poses (location and orientation) by visual means so that the robots end-effector can be positioned at the desired poses. In this paper, the robot/vision system consists of a stereo-pair of CCD array cameras mounted to the end-effector of a six-axis revolute robot arm. From a systems point of view, accuracy issues of the vision system, the robot, and the manufacturing requirements are considered for the development of automated calibration methodologies for local and global work volumes of the robot/vision system. Resulting accuracy of local calibration on the order of 1.5 mm is sufficient for many automotive assembly applications. Multiple component assembly and robotic fastening has been demonstrated with the developed vision guided robot.

Vision guided robots for automated assembly

A vision guided robot system consisting of a stereo-pair of CCD array cameras mounted on the end-effector of a six-axis revolute robot arm is presented. The accuracy of the vision system, the robot, and the manufacturing requirements is considered from a systems point of view. The development of automated calibration methodologies for local and global work volumes of the robot/vision system is discussed. The accuracy of local calibration which is on the order of 1.5 mm is sufficient for many automotive assembly applications. The assembly strategy is described, and multiple-component assembly and robotic fastening with the vision guided robot is reported.<<ETX>>

Robot/vision system calibrations in automated assembly

A vision guided robot for assembly is defined to be a robot/vision system that acquires robotic destination poses (location and orientation) by visual means so that the robot’s end-effector can be positioned at the desired poses. In this paper, the robot/vision system consists of a stereo-pair of CCD array cameras mounted to the end-effector of a six-axis revolute robot arm. Automated calibration methodologies for local and global work volumes of the robot/vision system are described, including a perspective error transform calibration method for cameras. Multiple component assembly and robotic fastening has been demonstrated with the developed vision guided robot.

Improvement of robot overshoot by motor controller design

A number of industrial robots today have relatively good repeatability, yet, lack good accuracy and stability at high speeds. This paper presents an approach to measuring the positional overshoot of a six-axis revolute robot and a motor controller scheme to improve this problem. Positional accuracy data were collected for various speed ranges to characterize the overshoot phenomenon. This problem, to a great extent, was attributed to the controller design in which a simple positional feedback law was used to drive a stepper motor on each joint of the robot. To compensate for this, a second-order model for the motor and an optimal control law, which comprises position and velocity feedback, are proposed to improve the stability of the motor. A single-axis motion control system was developed to simulate the joint motion of the robot, and to evaluate the control scheme. Simulation results show that significant improvement in overshoot is achieved by the new controller.