Granite VSD-XE tuning

[richienz]

Need a bit of guidance please on tuning my VSD-XE drives , running a 1500w 70vdc linear psu and 940W Motionking AC servo motors.

I have set the position tuning in bench testing, the motors on command from MACH3 position quickly and reliably. However using the ever so dodgy "hand squeeze test" on motor shaft indicates to me I could get more stiffness.

I can easily force shaft to move position on a stationary motor, or slow the moving rotor, by hand friction grabbing the 4cm diameter coupling on the motor shaft, which for this combination I would expect higher stiffness and response.

So I have trawled the forums and found indications that perhaps I am doing something wrong. Since I am using position mode for my cnc I assumed I would only need to tune position so I have the PID position settings adjusted. Some forum posts have suggested that I need to tune all three velocity torque and position. Is this correct or do I just tune position?

Otherwise the system is behaving and stable and not faulting,

I had early issues with the PIV being crazy and untunable, so I used PID. And I stopped using the hall sensors for startup phasing and just let it settle. Now while bench testing with mach3 I am getting long test periods running for 18hours+ without a fault trip of any kind on both drives and motors x and y axis so at least a good start I think.

So in a nutshell although its stable, how do I get more stiffness? Do I need to tune all three modes position / velocity / torque ?

cheers
Richard

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[Larken]

How many lines is the encoder ?

[richienz]

hi thanks for your response, they are 1000ppr or 4000 counts/revolution . Cheers, Rich

[legendboy]

What low pass filter frequency are you using

[richienz]

I'll have to check what I set it with but pretty sure it was "by the book", to be honest I have not quite figured out the filter frequency and how it impacts the tuning. Any lay mans guide or handy tips you can offer on this appreciated!!!! I'll be having another crack at it in a couple fo days when I get home, right now I just want to complete bench testing my servo system and be confident in its torque and position holding stiffness before I start on my table and gantry build. cheers Rich

[Larken]

hi thanks for your response, they are 1000ppr or 4000 counts/revolution . Cheers, Rich

1000 line should be plenty for high stiffness. On low res encoders, it can make the motor soft.

Is the PS voltage close to the max motor voltage ? (which motor model is it ?... they seem to all be rated at 220 V)
If your running a 220V motor on 70 volts, it can't tune properly unless the P and D settings are really high, even with that you will get poor performance.

Larry

[richienz]

yup its 940W 70VDC 18A 8 pole 1000ppr , and my psu is outputting 65VDC and its pretty beefy 1500W psi in theory so should be able to deliver the current to the motors. All my DC supply cabling is super tidy and heavy duty cabling and connections all via Shneider din rail connectors and heavy gauge wire using crimp on boot lace ferrule too to avoid any broken strands. Its honesty got me a bit stumped Larry I must be miles out with my tuning to not be able to get them stiff like I expected. Thanks for your help many further guidance appreciated!!!

[legendboy]

post your gain values

[richienz]

I'm going to redo the tuning with a shaft lock on. I didn't realize I had to lock the shaft to do the torque tuning although it makes sense when you think about it, its just not int he VSD-XE manuals!!!!! Another fella DRNOS referred me to the Granite Devices Argon tuning manual which was where I saw the shaft lock instructions. Once I have that tuning done as a baseline I'll post my more realistic values. Thanks again for the help @legendboy

cheers, Rich