Abstract
It is easy to realize that most robots do not move to the desired endpoint (Tool Center Point (TCP)) using high-resolution noncontact instrumentation because of manufacturing and assembly errors, transmission system errors, and mechanical wear. This paper presents a robot calibration solution by changing the endpoint trajectories while maintaining the robot’s control system and device usages. Two independent systems to measure the endpoint positions, the robot encoder and a noncontact measuring system with a high-resolution camera, are used to determine the endpoint errors. A new trajectory based on the measured errors will be built to replace the original trajectory. The results show that the proposed method can significantly reduce errors; moreover, this is a low-cost solution and easy to apply in practice and calibration can be done cyclically. The only requirement for this method is a noncontact measuring device with high-resolution and located independently with the robot in calibration.
Highlights
Actuators, robots, will have kinetic errors after a long working time
Ultrasonic triangulation sensors used for the position tracking had increased processing speed and reduced the computational power, allowing the robot to react faster. e kinematics can be identified by EKF (Extended Kalman Filter) after estimating the robot positions
Wang et al [2] calibrated a 5500 kg 8-DOF engineering robot based on joint angle division and an artificial neural network (ANN)
Summary
Robots, will have kinetic errors after a long working time. Over the years, researchers have proposed various methods to employ software interference to overcome this problem. E kinematics can be identified by EKF (Extended Kalman Filter) after estimating the robot positions This method can reduce parameter errors, constant adjustment of the robot joint to achieve the target point is necessary. [10] showed a closed-loop tracking system based on a laser sensor to reduce the robot’s approximation error to less than 0.2 mm and ±1” during the drilling process for aircraft-assisted robot assembly These methods have restrictions, as their requirements are complex steps, such as camera calibration, angle detection, and laser alignment. The calibrated parameters could not be imported directly to the robot controller and a new kinematic solver was required to handle the new model definition This tolerance was only a simulated result from MATLAB and still needed to be confirmed in real experiments. We introduce a new method to calibrate the robot’s accuracy by a noncontact measuring device with a suitable resolution to the required accuracy. e measured TCP errors will be converted backward to find a replacement point to reduce the kinetic error. is technique is and cheaply applied in industry, which makes it perfect for calibration in robot maintenance cycles
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