Parameter identification for the ORNL CESAR manipulator

The scope of this study consists of three main areas. First, a test method is shown for measuring the CG location and inertia tensor for an arbitrary object. An inverted torsional pendulum is used for the tests. A full uncertainty analysis is presented. Extensive testing using a calibration block produced good results for the CG location and the moments of inertia. The products of inertia could not be measured accurately and had high levels of measurement uncertainty. Calibration problems were encountered with the torsional pendulum. A strong sensitivity to rod diameter was verified, with smaller rods giving better accuracy.

The second area of investigation is an analytical method of determining joint compliance for the Oak Ridge National Laboratory (ORNL) seven degree-of-freedom Center for Engineering Systems Advanced Research (CESAR) manipulator. The cable driven arm with a differential wrist was modeled, and estimated compliance values were determined. Also, a possible method for measuring the compliance at the motors is presented. Equations are given that transfer these motor values to the joints.

Third, a discussion of the damping in the arm is presented. Descriptions of damping in the joints and in the cables are given, along with a possible method for measuring the damping in the motors.