TCP-Calibration Unit

End-of-arm sensor and tool centre point calibration is a critical aspect of successful system implementation. End-of-arm sensing, in the context of robotic welding, is used to detect the actual position of the seam on the workpiece with respect to the robot tool frame. 

Analysis of the profile data yields the relative position of the the seam with respect to the sensor reference frame. If the sensor reference frame pose is known with respect to the end-frame of the robot, and the tool frame pose is known with respect to the end-frame, then the sensor data may be used to accurately position the tool centre point (TCP) with respect to the workpiece.

While end-of-arm sensor based control would appear to solve both robot accuracy and workpiece position error problems, this is only so if the sensor frame, end frame, and tool frame are accurately known with respect to each other. 

Should the sensor be accidentally knocked out of position, the robot system becomes a highly consistent scrap production facility. Indeed, this very concern has been one of the reasons why some companies that would benefit from a sensor based correction system have been reluctant to implement such a system. What is required is not only a technique that enables the frames to be automatically calibrated, but that also enables the system to quickly determine if recalibration is necessary. This second capability is perhaps the more important in practice, since it can be reasonably assumed that any calibration error will be caused by an unanticipated event that could occur during any welding cycle.