I'm going to be building a servo motor-driven two-finger gripper for a robot whose gripping force I need to measure. I'm thinking of using AVR-based current sensing on the servo to measure the force. Of course, I'd use an appropriate peripheral (like a current shunt monitor) to do the heavy lifting. Just thought I'd see if anyone here has tried something like this before and might have some tips. Thanks.

 

Yes. I work with a FIRST robotics team, and we've done something similar.
We used motor current to measure motor speed indirectly. You need the Speed-Torque-Current graph for the motor, which you can draw easily from the motor specs. From this graph you develop the equation for Torque vs Current. The format is just y = mx + b.

Things to look out for. Motor current can be very noisy, so you may need to filter it a bit before it goes into your AVR measuring system.

OK?

 

Thanks. I don't think I'll need torque, or even force specifically, just the current level when the gripper is empty and when it's gripping something. I figured the signal would be noisy and require filtering, but there's no way to know how bad it is until I start playing with it.

How did you measure motor current? What specific parts did you use? Can you post your schematic?