A method was developed to reduce the point-based registration error by restoring the rigid body condition (RRBC method). Registration is the process of transforming one coordinate frame to another coordinate frame. The coordinate frame from which points are transformed is called the working frame and the coordinate frame to which points are transformed is called the destination frame. The RRBC method can be used to reduce the uncertainty of a hole location and thus, improve the success rate for insertion tasks. Peg-in-hole experiments were conducted to quantify the level of improvement.

How the RRBC method works: A grid of points is measured in two different coordinate frames - working and destination. The basic premise of the RRBC method is that the distance between any two points should be same in the working and destination frames - a fundamental concept for rigid bodies. However, due to systematic and/or random measurement error, the distances are not exactly the same in the two frames. Using the two sets of measured points (fiducials), the RRBC method calculates the corrections to the fiducials in the working frame so that the rigid body condition is restored. For points that are measured only in the working frame (targets), corrections for these points are linearly interpolated from the closest corrected fiducials.

Data and results from three peg-in-hole experiments may be downloaded from this site.