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R2 uses brushless DC motors, harmonic drive gear reductions, and electromagnetic failsafe brakes as the building blocks for the powerful, torque-dense actuators in its human-scale, 5 DoF upper arms. Moreover, the use of series elastic actuators and novel tension sensing & control systems represent some of the most innovative technologies present in the humanoid robotic arms of R2. Series Elastic Actuators (SEAs): R2s SEAs achieve fine torque sensing at each of its joints without sacrificing strength or payload capacity. Such capabilities are enabled through the development of several advanced technologies. Specifically, novel planar torsion springs (U.S. Patent No. 8,176,809) are integrated into each rotary series elastic actuator (U.S. Patent No. 8,291,788), while two absolute angular position sensors, calibrated using a novel technique (U.S. Patent No 8,250,901), measure the deflection of each spring. Force and Impedance Control Systems (U.S. Patent No. 8,525,460): These systems use position sensor signals for sending position data to an embedded processor that determines the positional orientation of the load relative to a motor shaft and its related torque on a string. A FPGA-based controller (U.S. Patent No. 8,442,684) provides a high-speed (10 KHz) control loop for the electric motor and gear reduction assembly present in R2 joints. Tension Sensing & Control of Tendon-Based Robotic Manipulators: NASA has also developed technologies to provide tension sensing & control of humanoid robotic arms. First, a tendon tension sensor (U.S. Patent No. 8,371,177) measures strain on tendons (strings) employed in robotic arms. A novel calibration system (U.S. Patent No. 8,412,378) calibrates the tendon tension sensors. Finally, joint space impedance control systems (U.S. Patent Nos. 8,170,718 & 8,060,250) provide closed-loop control of joint torques or joint impedances without inducing dynamic coupling between joints, as well as programmable Cartesian arm stiffness.

NASA's soft, portable, wearable robotic device is "plug and play" - it includes all necessary electronics, actuation, software, and sensors required to achieve augmented limb movement. The garment is designed such that the human-robot interface distributes load across the torso, maximizing user comfort. Donning and doffing is simple, as the device lowers over the head, straps to the torso via Velcro, and possesses adjustable custom arm cuffs. Actuators are housed in the back of the garment, which pull custom conduit-tendon-based systems attached to the limb at optimized locations, causing the joint of interest to move to the specified orientation. Force sensing is employed to enable optimal control of the limb, measuring user-applied force to maintain commanded joint orientations. Integrated electronics and software provide power distribution, safety monitoring, data transfer and data logging. NASA's garment has multiple modes of operation. In active assist mode, shoulder abduction and flexion, and elbow flexion, may be commanded either simultaneously via coordinated control or individually while holding position/orientation of the other joints. In passive assist mode, the user can freely move the limb while the system provides minimal torque to the shoulder and elbow. The upper body robotic exoskeleton is at a TRL 6 (system/subsystem prototype demonstration in a relevant environment) and it is now available for your company to license and develop into a commercial product. Please note that NASA does not manufacture products itself for commercial sale.

<i>Technologies for Safe Workspace Control of Humanoid Robots:</i> Safety is critical in scenarios where humans (e.g., factory workers or astronauts) are working in proximity to, or interacting with, R2. Methods for applying workspace limitations in velocity-controlled robotic mechanisms (U.S. Patent No. 8,676,382) and force or impedance-controlled robots (U.S. Patent No. 8,483,877) help to ensure such safety. <i>Autonomous Control Systems for Humanoid Robotics:</i> A multiple priority operation space impedance control system (U.S. Patent No. 8,170,718) provides arm control, including programmable Cartesian stiffness. An interactive robot control architecture (U.S. Patent Nos. 8,364,314, and 8,260,460, and 8,706,299), including a simple GUI, provides an interactive development and work environment that integrates sensor data and feedback generated by R2. An additional system selects and controls appropriate manipulators to perform grasping operations (U.S. Patent No. 8,483,882). <i>Humanoid Robotic Health Management System:</i> A diagnostics, prognostics, and health management system for human robotics (U.S. Patent No. 8,369,992) operates at all hardware and software levels of the robotic system, enabling system-wide observability, controllability, maintainability, scalability, and extensibility. <i>Electromagnetic Motor Braking:</i> Electromagnetic fail-safe brakes (U.S. Patent No. 8,067,909) allow for selective, reliable braking of robotic motors (e.g., brushless DC motors) to ensure safe and effective operation. <i>Highly Durable Connector Pin:</i> To address the high failure rate of connectors in robotic systems with flexible members, a highly durable connector pin (U.S. Patent No. 8,033,876) was developed. The pin increases durability of connectors that are frequently flexed a condition that causes deformation and compromises connectivity.