Preliminary results in force-guided assembly for teams of heterogeneous robots

Abstract

The missions to the Moon and to Mars currently being planned by NASA require the advanced deployment of robots to prepare sites for human life support prior to the arrival of astronauts. Part of the robot's work will be the assembly of modular structures such as solar arrays, radiators, antennas, propellant tanks, and habitation modules. The construction will require teams of robots to work cooperatively and with a certain degree of independence. Such systems are complex and require of human intervention in the form of teleoperation attending unexpected contingencies. Latency in communications, however, will require that robots perform autonomous tasks during this time window. This paper proposes an approach to maximize the likelihood of success for teams of heterogeneous robots as they autonomously perform assembly tasks using force feedback to guide the process. An evaluation of the challenges related to the cooperation of two heterogeneous robots to join two parts into a stable, rigid configuration in a loosely structured environment is conducted. A control basis is such approach: it recasts a control problem by concurrently running a series of controllers to encode complex robot behavior. Each controller represents a control law that parses the underlying continuous control space and provides asymptotic stability, even under local perturbations. The control basis approach allows several controllers to be active concurrently through the null space control technique. Preliminary experimental results are presented that demonstrate the effectiveness of the control basis to address the challenges of assembly tasks by teams of heterogeneous robots.