AASD Servo driver and torque problem

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21 Jan 2024 22:35 - 21 Jan 2024 22:39 #291288 by besriworld
You need to set a speed ramp / acceleration.
Usually the drivers come with a factory setting that can run the motor without noise.
Have you tried playing with the pid settings Pn115 -pn116; Pn153-pn156

Ps: I think they are trying to work in positional mode.
First make the motor move from the driver's keyboard, then with linuxcnc
Last edit: 21 Jan 2024 22:39 by besriworld.

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22 Jan 2024 05:55 - 22 Jan 2024 05:55 #291310 by Gnevko
Firstly, I'd like to thank all of you for your answers!

I'm using the motor in positions mode (Pn002=2) with step/dir pulses from a MESA card. When I run the motor on its own, without connecting it to the spindle, everything works perfectly out of the box. I can go up to 3000 rpm without any issues, tested with both LinuxCNC and the jog function Fn002. The problem arises when I connect the motor to the spindle using an HTM 5M belt.

My question now is, can I drive the motor in speed mode using step/dir pulses, or do I need to use -10/+10 voltage for that?
Last edit: 22 Jan 2024 05:55 by Gnevko.

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22 Jan 2024 07:40 #291315 by tommylight
Most probably +-10V.
Step/dir is position mode, so requires tuning in the drive, several steps usually.

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22 Jan 2024 16:12 - 22 Jan 2024 16:25 #291348 by 0x2102
Speed mode is fine for Step/Dir as well. You want to run your Mesa StepGen in velocity mode.

I am running my Spindle with Step/Dir and velocity mode.

linuxcnc.org/docs/html/man/man9/hostmot2.9.html#stepgen

control-type
Switches between position control mode (0) and velocity control mode (1). Defaults to position control (0).

I think Pncconf will use velocity mode when you connect/assign a spindle to a StepGen - try that as an example. 
Last edit: 22 Jan 2024 16:25 by 0x2102.

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25 Jan 2024 17:07 #291613 by Gnevko
If you allow me a couple more questions:
  1. I still haven't found information about the maximum length of step/dir pulses and the minimum pause between them?
  2. In speed mode, the driver refused to operate from positioning pulses, the motor jast rotaties very slowly and don't reacts on step pulses.
  3. At high speeds (from 1000), an unpleasant screeching sound appears. is it normal?
  4. I delved into the function Fn018 (determining inertia), ended up with Pn257=6, but with such inertia, I can't set Pn259 > 4 without to get vibrations. How important is inertia in this case?
Thank you all in advance! 

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29 Jan 2024 22:02 #291939 by 0x2102
I think in this particular case you might need +/- 10V to drive your AASD in velocity mode. My spindle servo amp (different brand) can handle both modes with Step/Dir - which doesn't seem to be the case here.

The unpleasant noise is not normal but difficult to troubleshoot / advise from remote.

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13 Feb 2024 10:23 #293213 by DEVILHUNTER
I use several of this motors (600w and 750w for motion control and 3.8kW one as servo spindle). What you are experiencing is not normal. Mines use the A1-SVD drives, not the AASD, but they seem to be the same as the manual and all parameters are equal.

Lets start with your last questions.
-The manual states that the maximum input pulse frequency is 550kHz for diferential input (and encoder input) and 200kHz for single ended. With 500kHz your motor (with 2500 lines encoder) turn at maximum speed wihtout the need of any electronic gearing (Pn098=1, Pn102=1). If I remember right, I have 800ns as step lengh and step space, but redoing the math it should be 900.

-With your drive in speed or torque mode, it does only uses the +/-10V input. Your Mesa board don't have +/-10V signal but you can use your drive in position mode, there is no problem on that. This is how I work on my lathe, since I have a 7i96s. The pncconf utility does use velocity mode even to motion control. Your board will send the driver pulses at the right frequency and it should follow the speed command without problem. At startup and stop it will not follow the right speed as it will try to follow the position, but you can put some acceleration and deceleration ramps in linuxcnc. I haven't programmed them yet on my lathe and it does work with the 160mm chuck, so on your spindle should not be needed either.

-It's werid that you get to move your motor well unatached but not with the belt, given than the load is quite small. Is the belt well tensioned? Does it spin freely? Sounds like a mechanical issue.

-How have you performed your load-intertia ratio estimation? First you have to calculate the inertia ratio between your motor and your load (motor pulley and complete spindle) and introduce it on Pn266 before executing the Fn018. The spindle must be also engaged. I have found that the inertia ratio calculated by the autotune (inserted into Pn257) is not the one that give me the best sharp movements (at least for position control). I use it as reference but I tweek it up and down to get a faster response with the higher rigid grade selection (Pn259, usually 6 to 8) I can set.

-Have you programmed the right motor on Pn001?

-The AL-04 is probably overheating of your drive caused by the sudden stop of the motor after several test. The energy of the motor is dissipated on the internal breaking resistor and it will get hot. Since you are probably testing the motor with many start and stops, it will accumulate heat and the driver will enter on that alarm until it cools back. Either program on linuxcnc the deceleration ramp or use an external resistor.

-For the queston of besriworld about the pid settings: if he is using automatic gain adjustment (Pn258=1), all those PID parameters (Pn115,116,153 to 156, 196 and 197) are not used. All are overrun but the rigid grade selected on Pn259. If the drive is set to manual adjustment because he needs better response (for spindle use I don't think so), then he could tweek those paremeters.

-I have no idea why you have set Pn275 = 1.20. This parameter is for internal use and is not described in the manual. Also leave Pn020=0 and set the correct Pn001, the manual says not to modify the Pn020 for general use as it does affect other parameters.

Since you have tweeked several parameters, I would set to factory the drive and start over again.

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