Analysis of a Six-Axis Industrial Robot's Dynamic Path Accuracy Based on an Optical Tracker
Although robot calibration has maturational fundamental theories, its practical application is still in the primary phase. In fact, most users are hard to manipulate an industrial robot with high absolute positioning accuracy. Thus, this study intends to measure the dynamic path accuracy of a six-axis industrial robot based on an optical tracker, instead of an expensive laser tracker. The motion tracking approach was based on three robot motions, i.e. linear motion, circular motion, and cornering motion, with a series of varied motion speeds from 100 to 800mm/s. Results show the dynamic path errors (the difference between the presupposed position and the measured position) for linear, circular, and corner motions were 0.662±0.169mm, 1.901±0.109mm, and 17.334±7.572mm, respectively. Obviously, the corner path error was far more than the other two motions. Furthermore, we found that the relationship between path error and the robot motion speed, was not completely linear. The performance assessment aims to provide feedback information for the accurate robot motion control in a specific target workspace. It is therefore of paramount importance for industrial robot users who are interested in precise applications to fully understand the test methods used for assessing robot path precision.
Design and Fabrication of 6-axis Gesture Controlled Robot
In this paper, a six-axis robot which can be controlled by gestures is fabricated. The robot has six degrees of freedom and is easily accessible since the robot does not need higher efforts of controlling. A human hand glove is integrated with transceiver and flex sensors, the resistance variation of the flex sensor is transmitted to the robot axis. Based on the variation the robot can rotate angular or in a linear manner about its axis. A simple transceiver is used in order to control the signals which are sent and received between the robotic arm and the human hand. Arduino programming is used for controlling the system.
Kinematic calibration of a five-bar planar parallel robot using all working modes
We present a simple low-cost calibration procedure that improves the planar positioning accuracy of a double-arm SCARA robot to levels difficult or impossible to achieve using an equivalent serial robot. Measurements are based on the use of five custom designed magnetic tooling balls fixed to the periphery of a detachable working plate. Three of these tooling balls define the world reference frame of the robot, and the positions of the centers of all balls are measured on a CMM. A special magnetic cup end-effector is used. Measurements are taken by manually positioning the end-effector over each of the tooling balls, with each of the maximum of four possible robot configurations. Each of these measurements is repeatable to within+/-0.015mm. The robot calibration model includes all 12 kinematic parameters, and the calibration method used is based on the linearization of the direct kinematics model in each calibration configuration. The optimal number and location of the tooling balls is obtained by studying the observability index. Finally, an experimental validation at 14 additional tooling balls shows that the maximum position error with respect to the world frame is reduced to 0.080mm within the entire robot's workspace of 600mmx600mm.