Force sensor reading

Hello!

I would like to design some functions using force as feedback and I notice that stretch has force sensors on the lift and arm. Is there a way I can get data from the embedded force sensor and what’s its min/max limit?

Hi @jiawei_li, welcome to the forum! We have coarse force sensing via motor current on the lift and telescoping arm thanks to low gear ratios in the actuators for these joints. This feedback is best used for contact detection and more granular sensing. With an active instance of stretch_body, you can read the status of these joints to read this data:

import stretch_body.robot
r = stretch_body.robot.Robot()
r.startup()
print(r.arm.status['force'])
print(r.lift.status['force'])

If you’re interested in attaching a force-torque sensor to Stretch, please take a look at our tool share to get a sense of how accessories are attached.

Thank you! But what’s the load limit so I can prevent the overload on the motor

The limit at the end of arm is 1.5kg (3.3lbs) not including the Stretch gripper.