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Robot Calibration

The calibration of redundant robots poses challenges to the roboticist that are not present in the calibration of their nonredundant counterparts. A motivation for this project is space applications, mainly in light of the imminent commissioning of the International Space Station. In these applications, the robot must be calibrated without external sensors, for a fixed base is not readily available.

One basic item to identify in the context of robot calibration is the offsets in the joint-angle dials, whose zero does not always coincide with their nominal locations. However, when attempting to identify the joint offsets with the aid of the robot's own encoders, using self-motions, it turns out that, upon fixing the end-effector (EE) to the robot base, the offsets of the end joints cannot be identified. A set of measurements is needed in a different EE pose--position and orientation. We have established identifiability conditions and developed an identification algorithm that has undergone satisfactory tests in a dual-arm robotic workcell that is under development, as outlined in this same issue. (Figure 6.12).

Y. Gonthier, G. Bilodeau, F. Ranjbaran, J. Angeles, A. Robins (Bombardier Services)

Figure 6.12: REDIESTRO 1

Annual Report

Mon Jun 26 21:22:20 GMT 2000