Robonaut 2 – The First Humanoid Robot in Space *M.A. Diftler, *N.A. Radford, *J.S. Mehling, **M.E. Abdallah, *L.B. Bridgwater, **A.M. Sanders, *R.S. Askew **D. M. Linn, ***J.D. Yamokoski, ***F.A. Permenter, *** B.K. Hargrave *NASA/JSC , Houston, Texas **General Motors, Warren Michigan, ***Oceaneering Space Systems, Houston Texas Abstract—NASA and General Motors have developed the second generation Robonaut, Robonaut 2 or R2, and it is scheduled to arrive on the International Space Station in late 2010 and undergo initial testing in early 2011. This state of the art, dexterous, anthropomorphic robotic torso has significant technical improvements over its predecessor making it a far more valuable tool for astronauts. Upgrades include: increased force sensing, greater range of motion, higher bandwidth and improved dexterity. R2’s integrated mechatronics design results in a more compact and robust distributed control system with a faction of the wiring of the original Robonaut. Modularity is prevalent throughout the hardware and software along with innovative and layered approaches for sensing and control. The most important aspects of the Robonaut philosophy are clearly present in this latest model’s ability to allow comfortable human interaction and in its design to perform significant work using the same hardware and interfaces used by people. The following describes the mechanisms, integrated electronics, control strategies and user interface that make R2 a promising addition to the Space Station and other environments where humanoid robots can assist people. Robonaut 2 – The First Humanoid Robot in Space *M.A. Diftler, *N.A. Radford, *J.S. Mehling, **M.E. Abdallah, *L.B. Bridgwater, **A.M. Sanders, *R.S. Askew **D. M. Linn, ***J.D. Yamokoski, ***F.A. Permenter, *** B.K. Hargrave *NASA/JSC , Houston, Texas **General Motors, Warren Michigan, ***Oceaneering Space Systems, Houston Texas original Robonaut. Modularity Abstract—NASA and General is prevalent throughout the Motors have developed the hardware and software along second generation Robonaut, with innovative and layered Robonaut 2 or R2, and it is approaches for sensing and scheduled to arrive on the control. The most important International Space Station in aspects of the Robonaut late 2010 and undergo initial philosophy are clearly present testing in early 2011. This state in this latest model’s ability to of the art, dexterous, allow comfortable human anthropomorphic robotic torso interaction and in its design to has significant technical perform significant work using improvements over its the same hardware and predecessor making it a far interfaces used by people. The more valuable tool for following describes the astronauts. Upgrades include: mechanisms, integrated increased force sensing, electronics, control strategies greater range of motion, higher and user interface that make R2 bandwidth and improved a promising addition to the dexterity. R2’s integrated Space Station and other mechatronics design results in environments where humanoid a more compact and robust robots can assist people. distributed control system with a faction of the wiring of the I. INTRODUCTION introduction of robots in GM manufacturing, many of the N ASA and General Motors have a history of working together, targeted applications for robot use taking on formidable challenges, remain the same. Current that date back to the Apollo Lunar industrial robots operate in a Rover (need reference). The two highly structured task environment organizations have come together and are designed and again and this time to address a programmed to work in enclosed new challenge, developing robot workcells. The consistency of the assistants that can work in task structure enables robots to proximity to humans. safely perform their tasks. (Brief paragraph about how we However, this same structure also respect Justin, Asimov, Partner limits the robot task flexibility. robots etc, with references) While there has been some General Motors has been a technical progress that enables leader in the application and robots to operate in manufacturing development of robotic technology operations with less structure, the since its initial collaboration with full technical capability is still not Joseph Engelberger. GM was the mature, and has not been first manufacturer to use industrial realized. This "capability gap" has robots with its application of limited the range of robot Unimate robots in 1961. Today, applications for less structured General Motors employs uses environments. over 25,000 robots in its Manufacturing Operations worldwide. GM has influenced the industry over the years by leading technical development efforts in servo electric welding robots, paint application robots, the Unimate PUMA robot for light assembly, and fixturing robots. Fig. 1: Robonaut 2: units A and B Although performance, capability and reliability have greatly NASA experiences a very similar improved since the first robotics “capability gap.” The challenge in this case is to make are well suited for applications in more Extra-Vehicular Activity an unstructured environment and (EVA) tasks robotically are fully expected to reduce the compatible. Many of the work load on EVA crew by maintenance tasks on the performing routine maintenance, International Space Station (ISS) assisting crew members before, are robotically serviceable and the during, and after EVA, and serving Canadian Space Agency’s Special in a rapid response capacity. Purpose Dexterous Manipulator NASA’s success in developing (SPDM) currently on-board ISS and demonstrating R1’s has the capability to perform these capabilities attracted the attention tasks. However, to perform its job of GM. GM approached NASA in SPDM, utilizes different approach 2006 as part of a worldwide corridors than human EVA and review of humanoid robotics in must interface with specialized search of new technologies that robotically compatible interfaces. would help their skilled workforce While specialized worksites and improve product quality and interfaces for robotics system manufacturing assembly have been very successful in processes. A detailed review of space they only address a portion the Robonaut 1 system convinced of the servicing for ISS. GM that NASA’s expertise in Astronauts working with EVA upper body systems specifically compatible tools will perform a designed to assist astronauts considerable amount of the made the agency an excellent maintenance activities. partner for developing the robotic NASA developed Robonaut 1, technologies that would also meet R1, (ref) to assist the crew in GM’s goals of closing the these servicing tasks and reduce “capabilities gap”. It was realized this “capability gap.” R1 has by both organizations that there demonstrated, in high fidelity were enormous benefits from a ground based demonstrations, its robust anthropomorphic robotic ability to work with existing EVA system that relieves people - tools, and interfaces within the factory workers or astronauts - constraints of EVA worksites. from dangerous or ergonomically Anthropomorphic robots, like R1, painful and difficult activities. For NASA and GM to achieve runs of sensitive analog signals. the desired performance Therefore, the avionic architecture improvements, Robonaut 2 for R2 was designed and required a number of significant developed around one central advancements in the robot's theme – the reduction of the electromechanical design, sensing conductor count in the robot and integration, controls strategy, and specifically the two arms. user interface. At the heart of In order to fundamentally reduce these advancements are the conductor count, a new technologies and approaches that communication scheme was allow for increased speed, required. R1 was built upon a strength, and dexterity while not point to point RS-485 sacrificing, and in fact improving communication architecture that, upon, a system design compatible including power and other relevant with direct human interaction that signals, required over 100 hads always been a focus of conductors in each main arm previous Robonaut development. cable. This produced an unwieldy (arkward) amount of wires that often got damaged during unrelated II. MECHATRONIC DESIGN FOR servicing and the wires RELIABILITY themselves were often the reason With 42 independent degrees of for other maintenance required on freedom, 50 motors and over 350 the robot. Moreover, that amount sensors, R2, shown in figure 1, is of wiring for each arm forced the a mechatronic integration cabling to reside externally challenge. Prior lab experience whereby it created additional on R1 and other robots challenges in how to manage to demonstrated a direct correlation service loop. In contrast, R2 was between the overall wire count in designed to have a distributed a robotic system and the reliability processing architecture with a of said system. R1 had a high speed serial communication centralized processing and point network that utilized a bussed to point communication paradigm power configuration. This afforded which necessitated large the robot a minimal set of wires for conductor count cabling and long each internal main arm cable which totaled only 16. The high scale, 5 degree-of-freedom upper speed serial communication arms. The use of series elastic structure is a custom protocol actuation, however, differentiates which utilizes Multi-drop Low R2 from previous designs. Voltage Differential Signal Developed initially with legged (MLVDS) as the physical layer