Space Walking Robots - Robonaut

NASA The range of motion in the arm exceeds that of a human

Arms

Robonaut's arms are human scale manipulators designed to fit within the exterior volume of an Astronaut's suit (the EMU). Beyond its volume, design objectives were human equivalent strength, human scale reach, thermal endurance to match an 8 hour EVA, fine motion, high bandwidth dynamic response, redundancy, safety, and a range of motion that exceeds that of a human limb. The arm has a dense packaging of joints and avionics developed with the mechatronics philosophy. The endoskeletal design of the arm houses thermal vacuum rated motors, harmonic drives, fail-safe brakes and 16 sensors in each joint (saves on the health insurance quotes!). Custom lubricants, strain gages, encoders and absolute angular position sensors were developed in house to make the dense packaging possible. The Roll-Pitch-Roll-Pitch-Roll-Pitch-Yaw kinematic tree is covered in a series of synthetic fabric layers, forming a skin that provides protection from contact and extreme thermal variations in the environment of space. Two of these arm joints have already been tested in a thermal vacuum chamber at JSC, where they performed well as the temperature was varied from -25C to 105C.

Robonaut Control System

The Robonaut control system architecture must respond to several interesting challenges. It must provide safe, reliable control for 47+ degrees of freedom. It must be controllable via direct teleoperation, shared control, and full autonomy. It must maintain performance in a harsh thermal environment. It must execute at the required rate on reasonable computing hardware. These challenges cannot be met by using only classical robot control methods. Advanced control theory in the areas of grasping, force control, intelligent control, and shared control must be developed to the point where the control is suitable for critical applications to fully realize the capability of the Robonaut. The overall control architecture is being developed around the concept of creating sub-autonomies which are used to build the main system. These autonomies each combine controllers, safety systems, low-level intelligence, and sequencing. As a result, each is a self contained, peer system which interacts with the other peers.