Description: Development of a robotic manipulator called Momentum Device Actuated Canfield (MoDAC) Manipulator for integration on to the assistive free flyers (AFF) being developed by NASA for the International Space Station is proposed. Integrating a robotic manipulator with an appropriate end-effector to an AFF provides the capability to perform several autonomous functions such as material handling, fetching and handling tools, procedural support to astronauts during their experiments, etc. Additionally, it can help the AFF to dock into battery charging stations and perch by grabbing on to rails or other features on the ISS. Some of the technical challenges posed by incorporating a traditional multi-degree of freedom manipulator on an object of small inertia such as the AFF include complexity in attitude control and rapid depletion of battery (or propellant) due to (a) reaction disturbances caused by a joint motion and (b) Variation in the inertia of the AFF-manipulator system caused by manipulator movement. Additionally, mass, volume, and control issues are posed by utilizing a serial multi-DOF manipulator. Development of a parallel kinematic manipulator with a disturbance-free actuation mechanism will improve the performance of the AFF's attitude control system. Additionally, a manipulator-embedded mass property estimation scheme will complement the task of controlling the AFFs position and attitude. The proposed MoDAC manipulator achieves these objectives by using a reaction wheel based actuation method for a modified Canfield mechanism. Additionally, the manipulator electronics are embedded with a manipulator-inertia estimation algorithm that is transmitted to the AFF in real time for superior attitude control. The Phase 1 effort will demonstrate the technical feasibility to perform disturbance-free manipulator operations suited for Assistive Free Flyers such as SPHERES and HET-2 via high-fidelity simulations and proof of concept prototype development and testing.

Benefits: The MoDAC manipulator provides a means to achieve reaction-free actuation of manipulators. The technique is beneficial primarily for microgravity (on-orbit) applications and very low gravity applications (e.g., asteroids and comet surfaces) where reaction torque on the base body is a concern. The development of the MoDAC manipulator is therefore targeted only towards space based applications. The applications mainly include NASA and the Department of Defense's (DoD) space missions. The MoDAC manipulator will be designed specifically for integration on to AFFs being developed by NASA. Millennium will work closely with NASA to assure compliance with AFF specifications and to perform the developmental activities consistent with NASA's goals. However, the concept and the design can be applied to any of NASA's on-orbit robotic applications. As NASA pushes forward on the path to exploration of the Solar System and beyond, the necessity for manually controlled or automated robots is increasing. Example of such applications include sample retrieval from asteroids and planets, asteroid capture, proximity operations, docking, etc. Scaled versions of the MoDAC manipulator can be used for any and all of these applications.

The Department of Defense, specifically, the Defense Advanced Research Projects Agency (DARPA) has goals of protecting, servicing, and extending the life of national space assets using on-orbit robotic servicing missions. The MoDAC manipulator can be used effectively in these missions. The MoDAC manipulator can be used independently or attached to the end of another manipulator to perform precise "end-game" or terminal operations (e.g., final grappling, docking, etc.). The MoDAC manipulator on the AFFs can be used extensively to research algorithms and control strategies for such robotic applications.