High precise and zero-cost solution for fully automatic industrial robot TCP calibration

Abstract

Purpose The purpose of this study is to present a novel method for industrial robot TCP (tool center point) calibration. The proposed method offers fully automated robot TCP calibration within a defined cycle time. The method is applicable for large-scale installations due to its zero cost for each robot. Design/methodology/approach Precise and expensive measuring equipment or specially designed reference devices are required for robot calibration. The calibration can be performed by using only one plane plate in this method, and the calibration procedure is defined step by step: the robot moves to the target plane position. Then, the TCP touches the plane and the actual robot configuration is recorded. Then robot moves back into position and the same step is repeated for a new sample. Alternatively, the robot can be stationary and the plane can be moved towards the robot TCP. TCP is calculated by processing the difference of the contact points recorded at different positions. The process is fully automated. No special equipment is used. The calculations are very simple, and the robot controller can easily be realized. Findings The conventional manual robot TCP calibration process takes about 15 min and takes more time in case of the high accuracy. The proposed method reduces this time to less than 3 min without operator support. Practical tests have shown that TCP calibration can be performed with 0.1-0.6 mm of accuracy. This solution is an automated process and does not require special installation and it also has approximately zero cost. For this reason, this study recommends using the proposed solution widely in areas where even one or hundreds of robots are located. Research limitations/implications In this study, the data were directly taken from the robot controller without using any special measuring equipment. The industrial robot used in the tests has no absolute calibration. The classical “four-point method” was used for reference TCP data. It is the initial acceptance that this process conducted with extreme care and by using a needle-tipped tool will not produce exact values. It was observed that deviation of the TCP from a fixed point in reorient motions was not more than 0.5 mm. This method has been validated for different bits. The pilot works for different robot applications in Ford Otosan Gölcük Plant have been completed and dissemination has started. Originality/value Although the approach uses is clear and simple, it is surprising that the calculation of TCP using plane equations has so far not been mentioned in the literature. The disadvantage of using either fixed point or sphere as a reference is that the TCP cannot automatically guide to the target. This problem was overcome with the use of a larger target plane plate and the process was fully automated. The proposed method can be widely used in practical applications.

A Novel 3D Complex Welding Seam Tracking Method in Symmetrical Robotic MAG Welding Process Using a Laser Vision Sensing

“…X T , Y T , Z T representing the coordinate axis of the robotic welding torch coordinate system {T}, respectively. To perform the first step of the coordinate system conversion, the welding robot TCP (tool center point) calibration of welding torch was conducted [24]. The compatibility conditions and the governing statics and dynamics equations have been combined to find the transformation matrix of the robot [25].…”

“…To improve the reliability and accuracy of the calibration results, the welding torch calibration experiment was repeated three times to obtain three sets of welding robot pose data, and the results were then averaged. The computed results of the transformation matrix 𝑻 and 𝑻 are shown in Equation ( 6 To perform the first step of the coordinate system conversion, the welding robot TCP (tool center point) calibration of welding torch was conducted [24]. The compatibility conditions and the governing statics and dynamics equations have been combined to find the transformation matrix of the robot [25].…”

Automatic Calibration of the Adaptive 3D Scanner-Based Robot Welding System

“…The method ( Deniz and Cakir, 2017b ; 2017a ) represents the mentioned equation in quaternion representation, solving an absolute orientation problem. Hand-eye calibration often mimics the well-known method of Tool Center Point (TCP) determination (Handbook of Industrial Robotics, second Edition | Wiley) by touching a fixed point either mechanically with an end-effector from different orientations ( Cakir and Deniz, 2019 ), where a novel method of automatically calculating TCP using plane equations is introduced. The method is based on detecting the contact between a robot tool and a flat, electrically conductive plate.…”

Efficient TCP Calibration Method for Vision Guided Robots Based on Inherent Constraints of Target Object

“…Hong and Ji et al [18] have used the geometric constraints between the sphere center and the spherical plane's points. Cakir and Deniz [19] and Han and Li et al [20] have used instead a flat plate as a calibration tool.…”