Using current to measure servo motor power

Thread Starter

Involute

Joined Mar 23, 2008
92
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.
 

sailorjoe

Joined Jun 4, 2013
362
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?
 

Thread Starter

Involute

Joined Mar 23, 2008
92
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?
 
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