Need Help!- I need a little fine tuning help

[springlakecnc]

Hi All,

Got my new Viper 200 drives, got em wired up.

The Servo’s seem to run smooth at fast rpm’s, but they have small oscillation when running slow. (Like a high frequency, real quick oscillation) I have those 2 brush nema34 motors Keling sells. They have 250 line differential Quadrature encoders from US digital. I think the motors are 90 volt and my power is about 80 volts.

What I did:
1) set p @ 0100
2) set I @ 0000
3) set d @ 0200
4) set l @ 0004

This is what I understood the manual to say.

I increased “p” to 1700, when the motor started oscillating. I dropped “l” (loop) to 0003, and the motor stopped oscillating. I brought “d” up to 3400. I increased “i” to 0003.

I have been changing all these parameters little by little, but can’t seem to smooth it out at slow speed, like going 1” per minuit.

Any ideas on what to tune?

Thanks

[sandefuj]

Springlakecnc:

Are your encoder wires shielded? Are they separated from the motor power cables? I had trouble adjusting my motors and drives, had to call Larry, and it turned out to be noise in the encoder cables. I replaced mine with shielded cables, and after that all was good. Super easy to tune and no more oscillations.

Jay

[springlakecnc]

Thanks for the responce Jay,

Yes, i always use shielded, twisted pair, encoder wire, although i always do strap them to the motor power cables which are shielded also. I have done that for years, and never had any problems in that area.

I do have the belts and pullys to reduce my gearing to 10 turns per inch, vs 5 turns on the x&y axis. My z axis is 20 turns per inch, and i don't notice anything on that axis.

I was using the 4x puls multiplier, and when i turned that off, it seemed to made a differance. today i'll play with it some more.

Thanks

[Larken]

I have been changing all these parameters little by little, but can’t seem to smooth it out at slow speed, like going 1” per minuit.

Increase the D (2 x P) as you increase the P. Increase the P 200 (and D 400) points at a time until you get the stiffness you need. A jump to 1700 is probably too high.
The D derivative is the vipers best software feature as it makes the motor stable without reducing bandwidth.

Disturb the motor (fast short burst of 50-100 steps) and adjust L for deadest responce.

Larry K

[springlakecnc]

Thanks Larry,

I'll give that a try.

BTW. I'm impressed with your drive.

Your documentation needs a little work. You have to remember, YOU are an electrical engineer, WE are Tool Makers trying to get our dead cnc going. Tool Makers don’t understand electrical engineer language, so please keep that in mind when you write your manual. Also many Tool Makers, know little about computers, like me!

An example is: “ Run the windows Hyper Terminal program from the Accessories group”

I looked through your web site for the Accessories group, and couldn’t find it, then it hit me, IT’S A WINDOWS PROGRAM!

Next, My computer I run my machine with is Windows 98. I build machines and program logic controls, so I have heard about things like 8 bit, 16 bit, etc, and in your specks is = 32 bit PID control with 16 bit RISC processor.
Due to me reading that, I suspected my windows 98 computer wouldn’t work for the Hyper Terminal hook up, and I was right! I think windows98 is 16 bit and your drive is 32 bit, or something like that.

You should have said in the instructions:

Run the Windows Hyper Terminal program from the Accessories group, located in your Windows XP or Windows Vista computer. Older Windows versions won’t work.

That’s the kind of instructions us outdated Tool Makers need.

I will be buying more of your drives, they are sweet!

[Larken]

Run the Windows Hyper Terminal program from the Accessories group, located in your Windows XP or Windows Vista computer. Older Windows versions won’t work.

Windows 98 and even windows 95 both have Hyperterminal. I use them all the time. A standard install doesn't always include all the accessory programs. You need to 'Add programs' and install them off the windows CD.

I will be buying more of your drives, they are sweet!

Glad you like the drives