Technical information

Summary of Repairs Conducted on the Debris Removal Vehicle (DRV) During

Field Testing for the Period 1/01/01 – 5/31/02

January 2001

Report

Auto dump function will not work.

Problem

The position sensor on the short arm joint drifted out of calibration due to mechanical

forces causing loosening. This prevented the arm from reaching the targeted coordinates

required due to travel limitations on the joint. Therefore, the motion sequencing could

not be completed. The controller remained in the auto-dump mode trying to obtain an

unreachable coordinate.

Fix

Re-calibrate the position sensor. Tighten the locking nut on the position sensor.

February 2001

Report

There appears to be reduced clearance between the clamshell and the dump body.

Problem

The position sensor on the long arm drifted. The controller sees the clearance as being

greater than it really is. The position sensor has mechanically loosened and the axle bolt

has started rocking on the setscrew.

Fix

The seats for the setscrews in the axle bolts were re-drilled and the setscrews replaced. In

addition, the position sensors were replaced. The mechanics were trained on how to

check all joint coordinates for slipping.

March 2001

Report

The position sensor coordinates have drifted again.

Problem

The robotic arm has several sections that are twisted, or bent; however, because the joints

use spherical bearings, the mechanical system is still functional. The joint position

sensors are mechanically connected to the axle bolts via a flexible coupling.

Unfortunately, the axle bolts exhibit a procession rather than a simple rotation, due to the

bent sections. The precession of the bolt exceeds the range of the flexible coupling