Stepper Motor control issues with Micro850 and CCW

[MikeBriggs]

I'm controlling an Applied Motion HW23-601D using a Leadshine EM542S connected to a 2080-LC50-48QBB, using CCW, and experiencing some weird issues. The motor is connected to a linear actuator with almost no load.

1. It will randomly (maybe 10-20% of the time) go in the wrong direction, when using MC_MoveAbsolute commands. for example, if it's at a current position of 6 cm and I tell it to go to 8 cm, most of the time it will correctly move in the + direction. But occasionally it goes in the negative direction. The MoveAbsolute command doesn't use the direction input, it figures out direction based on the current and set position, and sets the direction output for the axis accordingly. Maybe that output is getting set late?

But, something just happened that makes me think it's not just that. I was having it move from 3 cm to 6 cm, and it started moving in the + direction but then shifted to moving in the - direction, ending up almost back where it started (although it thinks it's now at 6 cm).

2. There seem to be certain velocities at which it goes nuts - moving very erratically, sometimes just jittering around in place.

3. If the velocity is more than 0.8 cm/s, I start running into missed steps during acceleration (even if I make the acceleration very small, like 0.05 cm/s^2, and even though there's practically no load so very little torque required).

The motor is 1.8 degree, so 200 pulses per revolution, which I have configured correctly in CCW and also on the Leadshine driver. It's 4.2A max current, which is also set correctly on the Leadshine.

Any thoughts?

Thanks,
Mike

 

[MikeBriggs]

Forgot to add - it also stalls intermittently on longer moves when the speed is higher, like 4 cm/s (which is still very slow for the motor, since it's 0.585 cm/revolution, so this is only about 2 rps, well inside it's torque curve). This is supposed to be a high torque motor, and right now it's only moving a linear actuator with very little torque load. Yet it's still skipping steps and stalling at speeds that should be well within its capabilities.

 

[MikeBriggs]

I found the problem - bad motor. I measured the resistance of the two phases and they're not identical (I would think they should be. Each one is really a couple windings connected in parallel, and I'm getting 0.7 Ohms on one phase and 1 Ohm on the other, perhaps because one of the parallel windings is disconnected on one phase).

I replaced it with a different motor (Oriental Motor PV267) and everything is working perfectly now.