EuRoC Forum

[5dpo]

I realize this might seem like a silly question but...
Reading the documentation, i don't seem to find how to close or open the gripper. Is there a service i haven't been able to find? I haven't manage to control with the servotarget service. Any help would be appreciated.
Kind regards.

[Peter Lehner]

The gripper can be controlled like any joint of the system with the move_along_joint_path or set_servo_target services. You can pass 'gripper' as the joint name and a position value between 0 - 0.07 meters to control the opening of the gripper jaws. For more information see section 2.2.2 of the technical annex.

Best
Peter

[kaust]

Just for confirmation:

The telemetry only has one joint value for gripper, whereas the gripper URDF has two joints - one for each finger.
Do we assume that the value is the same for both fingers, or is some other semantics being used?

[Peter Lehner]

Do we assume that the value is the same for both fingers, or is some other semantics being used?

The gripper value specified to the movement services directly corresponds to the opening between the gripper jaws as specified in the technical annex Section 2.2.2. The jaws move each half the value to produce the opening.
So the urdf joint values would be:
joint_before_finger1 = -0.5 * opening
joint_before_finger2 = 0.5 * opening
Note that the movement services limit the opening of the jaws to max. 0.07 m (The joint limits in the URDF are +-0.035 m).