AB Motor Autotune Issue

I am having problems with a motor that suspect is autotune issue.

PLC-AB 1769-L18ERM-BB1B
Motor-AB TLY-A130T-HJ62AA TL-Series Servo 502.200/EA 502.20 Motor
Driver: AB 2097-V31PR0-LM

I have gotten different errors but what appears to be happening is the motor tries to turn to fast then gives an excessive velocity error. The encoder has 8000 counts per revolution. The gear box has a 5:1 ratio. I set the scaling to 40,000 counts per revolution.

What parameters should I use for the autotune? Almost everything I have tried has the motor turn fast for a very short time. Sometimes I get completed test but I suspect the tuning parameters are bad. Other times I can an error saying:
The command cannot apply the tuning parameters because of an error in the rune tuning command.

Any thoughts on whats happening would be appreciated. I happily provide more information if that will help.

Where is the encoder? On the motor? or on the gearbox?
Normally, the encoder would be on the motor, and you set the CPR for the motor, not the output of the gearbox.

The encoder is on the motor.

Then don't set it for 40000 rev's. Set it for 8000. It is measuring motor RPM.

I think the math on your scaling may be off. I'm assuming the gearbox is reducing, so the output shaft is 5 times slower than the input shaft. If that's correct, and the encoder is on them motor shaft, then your scaling should be 1600 counts per revolution of the output shaft, not 40,000.

The Encoder is measuring MOTOR SPEED. The encoder scaling in the drive is expecting just that.

jwm9876


There may be a little confusion going on
there are TWO places to enter scaling

1. the Motor TAB feedback - This should be 8000 counts per Rev (of the motor)
2. the Conversion Tab - for a 5:1 reducing gearbox where the output units are in REVS (of the gearbox output shaft) the scaling should be 40000

To assist on the autotune settings can you post your program?

For the scaling of
8000 counts per rev of motor
40000 counts per rev of output shaft
motor has a maximum speed of 6000 rpm (motor)
so your axis has a top speed of 1200 rpm (6000/5) (Gearbox)

There may also be a safety factor on the top speed so that you do not get to use all of the RPM of the motor

MichaelG:

I had my scaling done the way you had said with 8000 counts per rev of motor, with the 5:1 ratio, and the scaling of 40000 counts per 1 rev of the motor. I have since changed a few things but I haven't really seen much progress. When I use the values from autotune, I get violent motions, loud noises and Excessive Velocity Faults.

When I use the settings out of the box, with no gearbox, I get very jerky motion. I double and triple checked the wiring. Any ideas or similar experiences?

need the axis settings to assist further


Have you done the Hookup Tab Tests?

At this Point I need the motor turning and the direction correct
Before doing an Autotune I use out of the box settings that defaulted with the motor. I then use MDO MDF MSO MSF MAJ and MAM MRP motion direct commands to make sure that I can control the axis and that I can set up the travel limits

Use a trend! - have Position, Velocity, Acceleration, Torque and Position Error


Auto Tune - What are the settings you are using?

I usually start with 30% to 50% of Top Speed
I sometimes need to back off the Torque /Force % initially
I set the damping factor to 1 initially - this determines if overdamped (0.8) / critically damped (1) or underdamped (1.2)

I untick All options - No Integrators, No Feed forwards, No Filters, No compensation

You must know what the options are for and how to use, they are usually application and drive train dependant

Start Low (Speed and or Torqueforce) and then work up

I did do the hook up test and motor turns and in the correct direction. I tried using the autotune some more with your suggestions but I keep running into the same problems. The motor does not run in smooth motions with the out of the box settings, it always makes a lot of noise, and gives excessive velocity faults after autotuning. I am still new to the RSlogix evironmnet but I will get the trends going soon. I think that this might be a noise issue or an issue with the connections. I hooked up some wiring based on the advice of on a post here and did not fully understand why I did what I did. See following thread:
http://www.plctalk.net/qanda/showthread.php?t=94173

I'll continue to keep trying on my own but any advice would be appreciated.

MichaelG said:

need the axis settings to assist further

Click to expand...

Post your program if you can

Or even Just the Axis

are you sure that all motor wires are connected correctly?
Are the firmware versions of drive en CompactLogix compatible?

I am checked the wiring again and everything seems fine. Someone else here checked them for me as well. I'll look in to the firmware, but everything I purchased was new, directly from a Rockwell Distributor. I had to load new firmware to the PLC but I don't recall making any adjustments to the firmware on the motor drive. I am still trying to load my program on here but cannot figure out how to get it to the right file type.

Thanks for the input. It does not look like a wiring or noise issue. The out of the box settings were just not very good. The autotune worked well when I set the speed at %80 of the max, 100% torque, and with 1 revolution of the motor. Other settings that seemed perfectly reasonable gave horrible results.