5500 Servo Torque Limit

I have an AB 5500 servo that drives an arm up an down. Periodically, a jam occurs that blocks the arm's path with product while the arm is moving. Sometimes the resulting crash causes a timing belt to jump a tooth or get damaged.

Under normal operation, the motion of the arm is never a significant load on the servo. So I thought I would try limiting the torque such that the servo might give up sooner when the crash occurs.

I used an SSV to set the Axis.TorqueLimitPositive to lower values (originally 200 percent). I planned to keep lowering it until the servo couldn't perform the move so I could find my lower limit of operation. Well... I ran the Axis.TorqueLimitPositive value down to 0.0 and the servo continued to move without any issues. Not what I expected.

Any ideas on what I was missing? ( I was moving in the positive direction - also moved in the negative direction as well)

Hey.

Try setting the limit positive and negative to 50, and then do the same with Overtorque limit.

And remember, it is acoording to the rated motor current. so make sure that the motor is the right dimention in the program.

See all the parameters for torque in the picture attached.

I'll give a try the next time I get some downtime opportunity

Any chance the axis was set up for "inverted" direction ? Evidently v20 and v21 had a bug where the Positive torque limit affected negative direction movement, and vice versa, when the axis had been set up for Inverted direction.

You might want to look into the Overtorque Limit parameter instead.

Also, monitor the TorqueThresholdStatus bit to see if either direction's excess torque is going over the defined threshold.

Hmmm...

The motor polarity is normal, but the motion polarity is inverted...and it is version 21. So I will make note of that.

Another weird thing about this is that I alter the TorqueLimitNegative when I home (make it very low as I run up against a hard stop) and I always thought that worked. I had found that if I set that too low, it would stall out before it hit the stop on a very slow downward (negative) MAJ.

So I figured that setting the TorqueLimitPositive lower on an upward (positive) MAM would eventually stall out the MAM . But that didn't seem to be the case.

Production is back into 24/7 mode, so I'll have to play around with some of these other suggestions in a few weeks.

Select your cyclic parameters

For anybody viewing this to troubleshoot, I have learned that you must select your cyclic parameters in order to live edit your torque limits. Go offline, go to the axis, go to Cyclic Parameters, then check Positive and Negative torque limits as well as torque reference. This will allow you to view their values live and change them. If these cyclic parameters are not checked they will not be updated in the servo.