EuRoC Forum

[AM-Robotics]

Hello! We have a question regarding the stop condition service: How does that exactly work?

Does it work for both motion services (movealongjointpath and servomode ?)?
Does the service has to be called before each motion or does the robot store the settings?
Why do we have to specifiy the "condition type" field, isn't that a redundant information to the "joint_name" field or isn't the "tool_force_threshhold" only applicable to the gripper, respectively?

Thank you!

[Peter Lehner]

Hello, thank you for posting on the forum! Please see the answers below.

Does it work for both motion services (movealongjointpath and servomode ?)?

No, the stop condition service only has an effect on movements with the move along joint path service. During servo mode the user is expected to monitor the movement on its own, for example by listening to the telemetry topic.

Does the service has to be called before each motion or does the robot store the settings?

The stop conditions are stored until you call the set stop conditions service again. The robot motions do not reset the stop conditions.

Why do we have to specifiy the "condition type" field, isn't that a redundant information to the "joint_name" field or isn't the "tool_force_threshhold" only applicable to the gripper, respectively?

The "tool_force_threshold" is not the same as the "joint_ext_torque_threshold" for the gripper. A "tool_force_threshold" stop condition specifes a threshold for an estimated cartesian force at the TCP of the robot, estimated from torque measurements in the arm joints. A "joint_ext_torque_threshold" stop condition with "joint_name = gripper" specifies a threshold for the measured force on the gripper jaw joints.
For example: If you would pick up an object with the gripper the "tool_force" would be the force exerted by the weight of the object pulling the TCP towards the floor. The "joint_ext_torque" at the gripper would be the force exerted by the gripper to hold the object in place.