Engineering topics
Publications and source records attributed to Schenker, P. S..
The capability to remotely and robotically perform in-space assembly, inspection, servicing, and science functions would rapidly expand our presence in space, and the cost efficiency of being there.
Experiments are described which were conducted at the JPL Advanced Teleoperator Lab to demonstrate and evaluate the effectiveness of various teleoperator control modes in the performance of a simulated Solar Max Satellite Repair (SMSR) task. THe SMSR was selected as a test because it is very rich in performance capability requirements and it actually has been performed by two EVA astronauts in the Space Shuttle Bay in 1984. The main subtasks are: thermal blanket removal; installation of a hinge attachment for electrical panel opening; opening of electrical panel; removal of electrical connectors; relining of cable bundles; replacement of electrical panel; securing parts and cables; re-mate electrical connectors; closing of electrical panel; and reinstating thermal blanket. The current performance experiments are limited to thermal blanket cutting, electrical panel unbolting and handling electrical bundles and connectors. In one formal experiment even different control modes were applied to the unbolting and reinsertion of electrical panel screws subtasks. The seven control modes are alternative combinations of manual position and rate control with force feedback and remote compliance referenced to force-torque sensor information. Force-torque sensor and end effector position data and task completion times were recorded for analysis and quantification of operator performance.
Recent experiments conducted at the JPL comparing alternative manual control modes using the JPL Advanced Teleoperator system are described. Of particular interest were control modes that provide force reflection to the operator. The task selected for the experiment is a portion of the Solar Maximum Satellite Repair procedure we developed to demonstrate the repair of the Solar Maximum Satellite with teleoperators. The seven manual control modes evaluated in the experiment are combinations of manual position or resolved motion rate control with alternative control schemes for force reflection and remote manipulator compliance. Performance measures used were task completion times, average force and torque exerted during the execution of the task, and cumulative force and torque exerted. The results were statistically analyzed and they show that, in general, force reflection significantly improves operator performance and indicate that a specific force-reflecting scheme may yield the best performance among the control modes we tested. Also, our experiment showed that, for the selected task, the position control modes were preferable to the rate control modes and slave manipulator compliance reduced task interaction forces and torques.
The paper examines the performance of telerobotic tasks where the operator and robot are physically separated, and a comunication time delay of up to several seconds between them exists. This situation is applicable to space robotic servicing-assembly-maintenance operations on low earth or geosynchronous orbits with a ground-based command station. Attention is given to two developments which address advanced time-delay teleoperations for unstructured tasks: (1) the 'phantom robot', a real-time predictive graphics simulator developed to allow teleoperator eye-to-hand coordination or robot free-space kinematics under a time delay of several seconds; and (2) shared compliance control, a modified form of automatic electromechanical impedance control employed in parallel with manual position control to permit soft contact and grasp compliance with workpiece geometry under a time delay of several seconds.
The paper reports the ongoing development of a telerobot demonstrator. The demonstrator is implemented as a laboratory-based research testbed, and will show proof-of-concept for supervised automation of space assembly, servicing, and repair operations. The demonstrator system features a hierarchically layered intelligent control architecture which enables automated planning and run-time sequencing of complex tasks by a supervisory human operator. The demonstrator also provides a full bilateral force-reflecting hand control teleroperations capability. The operator may switch smoothly between the automated and teleroperated tasking modes in run-time, either on a preplanned or operator-designated basis.
The ongoing development of a telerobot technology demonstrator is reported. The demonstrator is implemented as a laboratory-based research testbed, and will show proof-of-concept for supervised automation of space assembly, servicing, and repair operations. The demonstrator system features a hierarchically layered intelligent control architecture which enables automated planning and run-time sequencing of complex tasks by a supervisory human operator. The demonstrator also provides a full bilateral force-reflecting hand control teleoperations capability. The operator may switch smoothly between the automated and teleoperated tasking modes in run-time, either on a preplanned or operator-designated basis.