Results of Human-in-the-Loop Testing of the Force/Moment Accommodation Feature using the Special Purpose Dexterous Manipulator Ground Test Bed 2000-01-2360

The Special Purpose Dexterous Manipulator (SPDM) is part of Canada's contribution to the International Space Station. Crew members inside the pressurized volume will command this dexterous robot to perform maintenance operations on the station that are normally associated with Extra-Vehicular Activities (EVA's). Operations will include complex tasks such as the replacement of faulty electronics units and battery boxes, collectively called Orbital Replaceable Units (ORUs). This type of task requires a manipulator that precisely controls and regulates contact forces. Precision is necessary to sense and correct for positional misalignments during the insertion of ORUs as well as to prevent jamming and overloading the ORU and worksite. The SPDM employs a feature called Force/Moment Accommodation (FMA), which is the robotic analogue of the crew member's sense of touch and muscle response, to actively regulate or accommodate the forces and moments generated during contact operations in all six degrees of freedom. This feature allows the robot to handle the fine alignment function during an ORU insertion task without operator input. The FMA feature has been demonstrated on the SPDM Ground Test Bed (SPDM GT), a gravity compensated robotic arm that is functionally and dynamically equivalent to the flight SPDM arm. An international crew evaluation of the berthing task using two types of flight ORUs and the SPDM GT was conducted. Trials with and without FMA active show that FMA significantly reduces operator workload and timeline. In addition, FMA enables the operator to perform robotic tasks that are not possible without this type of automatic control feature. The crew rated the ORU insertion task a 1 on the Cooper-Harper scale (excellent) when FMA was active, and rated the task between 6 and 9 (poor) when FMA was disabled. The trials have confirmed that the SPDM with FMA enabled is a capable, flexible tool suited for a variety of tasks normally performed by EVA's.