Fast Kinematic Re-Calibration for Industrial Robot Arms

Abstract

Accurate kinematic modelling is pivotal in the safe and reliable execution of both contact and non-contact robotic applications. The kinematic models provided by robot manufacturers are valid only under ideal conditions and it is necessary to account for the manufacturing errors, particularly the joint offsets introduced during the assembling stages, which is identified as the underlying problem for position inaccuracy in more than 90% of the situations. This work was motivated by a very practical need, namely the discrepancy in terms of end-effector kinematics as computed by factory-calibrated internal controller and the nominal kinematic model as per robot datasheet. Even though the problem of robot calibration is not new, the focus is generally on the deployment of external measurement devices (for open loop calibration) or mechanical fixtures (for closed loop calibration). On the other hand, we use the factory-calibrated controller as an ‘oracle’ for our fast-recalibration approach. This allows extracting calibrated intrinsic parameters (e.g., link lengths) otherwise not directly available from the ‘oracle’, for use in ad-hoc control strategies. In this process, we minimize the kinematic mismatch between the ideal and the factory-calibrated robot models for a Kinova Gen3 ultra-lightweight robot by compensating for the joint zero position error and the possible variations in the link lengths. Experimental analysis has been presented to validate the proposed method, followed by the error comparison between the calibrated and un-calibrated models over training and test sets.

Towards Haptic-Based Dual-Arm Manipulation

“…We utilized an oracle to guide the calibration procedure and ensure the object kinematics were consistent with the robot kinematics obtained using on-board sensors. The detailed approach is presented in [ 28 ], which was also used in this work with the oracle replaced by a highly accurate motion tracking system, i.e., PTI Phoenix Visualeyez. Furthermore, calibrated wrenches (sensed by the force/torque sensors) are used as (computing from sensed wrenches is discussed in Appendix A.1 ).…”

Ground Force Precision Calibration Method for Customized Piezoresistance Sensing Flexible Force Measurement Mat

“…Because the power differs depending on the order of transmission and reception of the data and the distance at which the power is applied and transmitted, it is thought that there will be a difference in the measured value [22]. Various studies have been conducted to correct errors caused by factors such as the order of transmission, reception, and voltage differences [23][24][25][26]. A previous study measured and calculated the hysteresis for the value of the force applied in calibrating a force-sensing resistor, and a digital filter was designed to perform individual matching of the measured value of the sensor [26].…”

A ROS-Based Kinematic Calibration Tool for Serial Robots

“…In practice, defining a faithful model may become a complex task, depending on the diversity and complexity of the modeled phenomena: flexibilities, gear-induced drift, thermal effects, etc. Yet, discrepancies caused by manufacturing and assembling defects appear to have the most determining impact on the robot accuracy [15,19,20] and benefit from a simplified and often sufficient geometric modeling.…”