Arm Control and Dexterous Manipulation
Saika: a light-weight, full-sized humanoid robot developed a the University of Tokyo.
The University of Tokyo Department of Mechano-Informatics has developed a humanoid robot, Saika, with a two-DOF neck, dual five-DOF upper arms, a torso and a head. Saika is able to dribble a bouncing ball and catch a thrown ball. It can grope for and grasp unknown objects. Whereas many humanoids are heavy and require large, unwieldy off-board apparatus for actuation, Saika is designed to be lightweight and has almost all the motors built into the arms and torso. The head, torso and arms together weigh less than 17 pounds. 3
MIA Arm S. Sugano Laboratory Waseda University.
The majority of industrial robots are position-controlled devices that move exactly as they are told. Some of these arms can easily lift over 2,000 lbs. For machines intended to interact with people, those that move with such force are a definite danger. For humanoids, it is crucial to develop arms that monitor the interacting forces between the robot and the many other parts of the environment with which the arm may come in contact. Ideally, humanoid arms will be lightweight manipulators that can provide strength while exhibiting compliant motion. Compliance includes the ability to "give" when the arm encounters impedance. For example, if a robot is reaching to pick up an object and a human gets in the way, the force exerted by the arm should give accordingly. Seeking a compliant, yet strong robot arm, Waseda developed a 7-degrees-of-freedom (D.O.F.) anthropomorphic manipulator, which consists of shoulder, elbow and wrist.
Robonaut's upper body. NASA Johnson Space Center
Instead of using an active (motor-driven) approach to compliance where performance is limited by the response of servo motors, Waseda uses a passive compliance control method in which a linear spring and brake systems are used to dynamically adjust the "give" in each arm. The result is a force-controlled robot that can safely cooperate with humans while carrying out advanced dexterous manipulation tasks.
NASA has engineered a dexterous humanoid robot that will deploy, maintain and operate a wide variety of shuttle and space-station components. Currently, astronauts must perform a variety of extremely dangerous and costly dexterous tasks. The objective of the Robonaut project is to develop a space robot with dexterous capability exceeding that of a suited astronaut. This will reduce response time, high costs and some of the dangers associated with sending an astronaut into space. To accomplish these aims, Robonaut must be able to efficiently assist astronauts by sharing their space and tools. Robonaut will need to respond to natural communication and learn through what NASA JSC calls virtual-reality coaching where the human will effectively take control of the robot and guide it through certain movements and behaviors.
Robonaut's hand holding a space torque tool. NASA Johnson Space Center.
To accomplish much of this work, JSC plans to use advances in learning to coordinate vision, tactile and proprioceptive sensing and action. Currently, Robonaut can be teleoperated by a human using a VR interface. Motion-sensitive apparel help map human actions to the body of the robot. To facilitate the interface, stereoscopic cameras provide the user with a panoramic view to give the feeling of being in the robot's body. The VR interface is so natural that even first-time users can learn to control Robonaut in minutes. Even greater skill will be enabled once haptic forces can be applied to the hand of the human operator.
This work has proved to be an incredible integration effort. NASA reports that approximately 50 percent of the work has been spent integrating various components into a single body. Within the body, components are interconnected to a spinal cord that sends sensory signals back to a centralized core. Once a cognitive architecture is in place, the brain stem will allow sensory feedback to flow quickly between the body and brain.
Parts of Robonaut's hand, showing the dexterous and grasping sets. NASA Johnson Space Center