Servo - May 2015

Bracing, Anchoring

Since RoboSimian is still in its early design phases, its creators have not fully exercised every capability the robot has, such as passively stable stances, multipoint anchored connections, and bracing itself during forceful manipulation operations.

"The idea of the multipoint anchor connections is that in 3D, we can apply the end-effectors such as in a ladder climbing scenario," Kennedy commented. In this scenario, RoboSimian's hands and feet can grab the ladder rungs at at least three points with three end-effectors at any one time and maintain stability.

Further, if the ladder tips over and is suddenly like a set of monkey bars, the robot would be insensitive to the fact that the ladder is at another angle. "It would simply go into a sort of monkey/sloth mode," said Kennedy. If the robot should try to open a door that is stuck shut, it could use one lower limb to brace itself while using two upper limbs to open the door if necessary.

Heading Agnostic Perception

RoboSimian is enabled with heading agnostic perception, which enables the robot to change direction without first reorienting itself. "By design, because each limb is the same and has multiple cameras, there is nothing different in terms of functionality based on heading," explained Kennedy.

There really is no front or back to the robot, so it does not have to move in a certain direction based on what it is or is not facing at the moment it changes direction. This enables the robot to change direction in fewer steps and movements. "The fewer the steps, the less the risk," smiled Kennedy.

The robot's axisymmetric distribution of the limb workspace and visual perception enable the robot with this heading agnostic perception. Because the four limbs are basically on a square with sufficient cameras all around to fill in each hemisphere of visible space with stereo data

(two camera eyes in each case like a human being, but with more sets of them), and because the cameras build a 3D model of the world around the robot in every direction, any set of cameras can point to the direction the robot wants to take next. "That's why the robot doesn't have to reorient itself first before moving in a new direction," Kennedy commented.

The Surrogate

While RoboSimian is great at generalized tasks, it is slow in benign movement tasks such as just walking across a long stretch of terrain. So, comes the Surrogate version of RoboSimian. "We gave it wheel accessories so it can roll. Wheels make sense for certain operational conditions," explained Kennedy.

While there are lots of tracked vehicles with robotic arms, Surrogate uses what was one of RoboSimian's arms as its spine. "The seven jointed spine allows us to position the Surrogate's upper body in any place or orientation in reach of the spine," said Kennedy. There are two more limbs on top of that spine that are not as generalized as the ones on RoboSimian. "They are more like arms and are more robust on the Surrogate," commented Kennedy.

The Surrogate also has a head and neck with two cameras on the head, which operators can point at whatever they are trying to work with. "It is more straight forward as a bi-manual robot with two limbs like a human being would use," concluded Kennedy. SV

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Early RoboSimian videos: www-robotics.jpl.nasa.gov/roboticVideos/vid1016-152-video.mp4 www-robotics.jpl.nasa.gov/roboticVideos/vid1016-154-video.mp4