In December 2013, 16 teams from around the world gathered at Homestead Speedway near Miami, FL to participate in the DARPA Robotics Challenge DRC Trials, an aggressive robotics competition partly inspired by the aftermath of the Fukushima Daiichi reactor incident. While the focus of the DRC Trials is to advance robotics for use in austere and inhospitable environments, the objectives of the DRC are to progress the areas of supervised autonomy and mobile manipulation for everyday robotics. NASA's Johnson Space Center led a team comprised of numerous partners to develop Valkyrie, NASA's first bipedal humanoid robot. Valkyrie is a 44 degree-of-freedom, series elastic actuator-based robot that draws upon over 18 years of humanoid robotics design heritage. Valkyrie's application intent is aimed at not only responding to events like Fukushima, but also advancing human spaceflight endeavors in extraterrestrial planetary settings. This paper presents a brief system overview, detailing Valkyrie's mechatronic subsystems, followed by a summarization of the inverse kinematics-based walking algorithm employed at the Trials. Next, the software and control architectures are highlighted along with a description of the operator interface tools. Finally, some closing remarks are given about the competition, and a vision of future work is provided.

Valkyrie: NASA's First Bipedal Humanoid Robot

A robot arm assembly includes a support arm, a connecting arm, and an end arm. The support arm is rotatably assembled with the connecting arm along a first axis, and is located at one end of the connecting arm. The end arm is rotatably assembled to the other end of the connecting arm along a second axis substantially perpendicular to the first axis, such that the connecting arm is rotatably assembled between the support arm and the end arm.

Robot arm assembly

A modular rotational electric actuator includes an output housing and internal drive components that include integrated control electronics, a torque sensor, and a portion of a joint assembly. The joint assembly includes a joint connector coupled to the internal drive components, including integrated control electronics, e.g., by a resilient member. The resilient member elastically couples the joint connector to a portion of the output housing, the joint connector including a portion that extends outward therefrom.

Modular rotational electric actuator

For safety purposes, cooperative robots are installed with an actuator composed of a low-power servo motor, a reduction gearbox, and a torque sensor. When cooperative robots make contact with humans or the environment, they must detect the contact force with a force sensor, a contact sensor, or a joint torque sensor. Equipping these sensors increases the cost and size of the application, but can be avoided under sufficient backdrivability of the actuator. To this end, we propose a method that maximizes the power transmission efficiency of the 3K planetary reduction gearbox and develop a prototype of the backdrivable reduction gearbox called the bilateral drive gear. For this maximization, the profile shift coefficients and the number of teeth are decided under some conditions. The forward- and backward-driving efficiencies of the prototype gearbox were 89.0% and 85.3%, respectively, and the reverse-drive starting torque was 0.020 N $\cdot$ m. The drive efficiency of the same gearbox with uncorrected teeth is 68.5%. The forward-driving efficiency was 20.5% higher than the nonoptimized one. We confirmed that prototype gearboxes with different gear ratios are easily backdrivable by hand.

/pdf/bilateral-drive-gear-a-highly-backdrivable-reduction-gearbox-59z8d2poeq.pdf

Bilateral Drive Gear—A Highly Backdrivable Reduction Gearbox for Robotic Actuators

Recent advances in mobility, manipulation, and intelligence of robots have promoted the usability of humanoid robots to support humans in their daily lives in the future. The multi-axis force-torque sensor is an essential sensor for the biped humanoid robot to maintain balance during walking and running since it is used to calculate the zero-moment point, the criterion of dynamic stability. Force-torque sensors will be widely used in the future because they are essential for service robots to interact with people in unstructured environments. However, due to special design considerations and requirements, it is difficult to find a suitable commercial force-torque sensor for biped humanoid robots and the price is very expensive. This paper reviews the multi-axis force-torque sensor used in current state-of-the-art humanoid robots based on the understanding of biped walking, zero-moment point, and ground reaction force. From an in-depth analysis of relevant information, sensor requirements are discussed with the robot performance. In addition, the structural design of the sensors is classified into four types and described in detail. This comprehensive review will facilitate the development of force-torque sensors in humanoid robots and will be helpful in extending their application in the various fields of service robots.

Multi-Axis Force-Torque Sensors for Measuring Zero-Moment Point in Humanoid Robots: A Review

A rotary actuator assembly is provided for actuation of an upper arm assembly for a dexterous humanoid robot. The upper arm assembly for the humanoid robot includes a plurality of arm support frames each defining an axis. A plurality of rotary actuator assemblies are each mounted to one of the plurality of arm support frames about the respective axes. Each rotary actuator assembly includes a motor mounted about the respective axis, a gear drive rotatably connected to the motor, and a torsion spring. The torsion spring has a spring input that is rotatably connected to an output of the gear drive and a spring output that is connected to an output for the joint.

/pdf/rotary-series-elastic-actuator-8j2du2xv32.pdf

Rotary series elastic actuator

An electromagnetic braking system and method is provided for selectively braking a motor using an electromagnetic brake having an electromagnet, a permanent magnet, a rotor assembly, and a brake pad. The brake assembly applies when the electromagnet is de-energized and releases when the electromagnet is energized. When applied the permanent magnet moves the brake pad into frictional engagement with a housing, and when released the electromagnet cancels the flux of the permanent magnet to allow a leaf spring to move the brake pad away from the housing. A controller has a DC/DC converter for converting a main bus voltage to a lower braking voltage based on certain parameters. The converter utilizes pulse-width modulation (PWM) to regulate the braking voltage. A calibrated gap is defined between the brake pad and permanent magnet when the brake assembly is released, and may be dynamically modified via the controller.

/pdf/method-and-apparatus-for-electromagnetically-braking-a-motor-1oynqtch7g.pdf

Method and apparatus for electromagnetically braking a motor

Eine Drehstellgliedanordnung zur Betatigung einer Oberarmanordnung fur einen geschickten humanoiden Roboter wird bereitgestellt. Die Oberarmanordnung fur den humanoiden Roboter umfasst eine Vielzahl von Armstutzgerusten, die jeweils eine Achse definieren. Eine Vielzahl von Drehstellgliedanordnungen ist jeweils an einem der Vielzahl von Armstutzgerusten um die jeweilige Achse herum montiert. Jede Drehstellgliedanordnung umfasst einen Motor, der um die jeweilige Achse herum montiert ist, einen Zahnradantrieb, der mit dem Motor drehend verbunden ist, und eine Torsionsfeder. Die Torsionsfeder weist einen Federeingang, der mit einem Ausgang des Zahnradantriebs drehend verbunden ist, und einen Federausgang auf, der mit einem Ausgang fur das Gelenk verbunden ist.

Adam H. Parsons

Papers

Rotary series elastic actuator

Method and apparatus for electromagnetically braking a motor

Serielles elastisches Drehstellglied