Autonomous Cooperative Assembly by Force Feedback Using a Control Basis Approach
Rojas, Juan Luis
Recent goals in space missions require innovative technologies to develop and to build infrastructure for space exploration. NASA plans to have robots construct modular systems and habitats and prepare them for life support prior to the arrival of astronauts. Modular truss structures are the hardware of choice for such tasks, requiring robots to grasp, manipulate, and assemble these trusses through cooperative work. Remote teleoperation for the purposes of assembly is difficult, tiring, and prone to errors. More so when the task involves numerous operators and robots. Additionally, the communication latencies encountered in space missions preclude the instantaneous teleoperation of the kind that would be required to control such a team of robots. A viable solution is possible through the use of a variable autonomy architecture. In this architecture, teleoperators could guide a robot to an optimal location where grasp or assembly can take place. The system would then slide to autonomous mode and allow the robot to perform the lower-level task autonomously. This thesis proposes a control framework that enables short term autonomy and cooperative assembly by two robots of highly differing morphology. The work advances the capabilities of heterogeneous robots to cooperate on some of the low-level tasks necessary for autonomous assembly. The proposed control strategy allows independent robots in loosely structured environments to execute insertion tasks. The approach is to modularize and encapsulate the control problem by recasting it in terms of locally robust controllers. The controllers do not require explicit planning, rather through sensory stimuli they drive the system to optimal state configurations. A number of novel basis controllers are presented in this work and used by a pneumatically actuated and highly compliant humanoid robot and a rigid industrial manipulator. Active-static and active-active robotic roles are tested in a number of different experiments to study the performance and efficacy of the approach in assembly tasks. Results show that the proposed framework effectively executed the assembly tasks in a variety of cooperative schemes, experiencing the fastest times in scenarios where both robots actively drove the insertion.