About the Robot Platform

Manipulators

The three fingers are referred to as “finger0”, “finger120” and “finger240”. The number denotes the angular position of the finger in the platform. In the robot observations, they are ordered like they are listed above.

Position Limits

If all joint positions are set to zero, the fingers point straight down. Note, however, that this configuration is not reachable as it would collide with the floor.

There is a lower and upper limit for the angular position (in radian) of each joint:

	lower limit	upper limit
upper joint	-0.33	1.0
middle joint	0.0	1.57
lower joint	-2.7	0.0

The limits are enforced in the software. If a joint moves out of the limits, actions for that joint will be overwritten by a command pushing it back inside the valid range. If a joint exceeds the limits too much, the robot will stop with an error.

Torque and Velocity Limits

To avoid damage of the system, the maximum torque is limited to +/- 0.396 Nm on all joints.

Further there is some velocity damping happening to prevent the robot from moving too fast.

Push Sensors

Each finger is equipped with a push sensor at the finger tip. The readings of these sensors are included as fingertip_force in the observations. The value is unit-less and lies in the interval of [0, 1] where a higher value corresponds to a higher force.

Note

The sensors have some offset, so they typically report a non-zero value even when there is no contact.