This is an email that Vlad forwarded me that he originally sent to another Rutex user.
I'm not quite sure who build the machine for you originally. You might try to contact them and ask them about the tuning. The tuning is very much motor/machine/encoder depended. There is not a universal procedure.
When you going to tune the R990H (R990H/R991H/R992H/R90H) drive you will have to run program such as:
http://www.rutex.com/zip/RT990H.zip
or latest version of Mach2
The older R990 (R90/R990/R995/R996/R997) drive can be tuned with the:
http://www.rutex.com/zip/R90.EXE
The reason for that is that the older version do the calculations in 16-bit and the 'H drives in 32-bit.
Before you start to tune drive you should mechanically disconnect motor from the machine and you should have the E-stop switch very close to your hand. Incorrectly tuned drive can violently oscillate which can do mechanical damage to the machine/motor or overheat the drive. As well, it is good idea to start the tuning at lower voltage (if you can drop down the voltage) to families yourself with tuning. There is much less mechanical/electrical energy.
Secondly, you should know if your system needs the Ki or not.
The difference is that without Ki the system is bit faster - sort of 'snappier' when traveling, but there is a inherent error of few encoder counts - somewhere around 5-50 encoder counts. With Ki the system might be slightly less dynamic but it will correct the steady error down to +/-1 encoder count. Most of the application is tuned with Ki.
Typical setup for DC PM running at DC30V with 500-line encoder could be somewhere Kp=1000, Ki=0, Kd=2000. If you apply Ki, then the Kp and Kd has to be dramatically increased. As well, the Ki has to be adjusted over certain value to work correctly. Usually very low Ki does no do good job at all. So the setting could be somewhere Kp=5000, Ki=150, Kd=3000. If you double the Voltage and double the encoder resolution, then the Kx values should be about the half. The above values are very bulk figures and you might end up with completely different.
When you look at the step response graph output, then it should be tuned for fastest setting time to acceptable error and not the zero overshoot. The step response does not have preprogrammed acceleration/deceleration so it can or it should overshoot.
Cheers
vh |
As you can see below, I used the RD990h.exe program.
If you select the Regs button for a servo you will see that the current KP, KI, KD settings are on display.
This is a real time viewer, so as you adjust the settings you will see the numbers change. I tried out using the suggested setting that Vlad mentioned in his email. Much to my amazement the servos were very tight and very snappy. It was just a matter of then pressing the tune button to see the results displayed on the graph.
I took note of what Vlad said about not been too concerned about the overshoot. I got mine down to about 60 steps overshoot. That may sound bad but when you think about it I was driving the servos at full speed and expecting them to snap to a halt, and that is on a 2000 pulse encoder.
If you make the speed slower then you get no overrun. When you think about it, It is rare for a machine to be running at full speed anyway. Usually the driving software decelerates the servos anyway. Oh for those who think overshoot means you lose steps, what it means is when it comes to an instant stop it temporarily overshoots by that margin before it corrects itself to where it should be. Its a bit like putting the brakes on in a car and expecting it to stop in an instant with no travel. MY settings are at Kp=4992, Ki=150, Kd=3024. Why dont you try that as a starting piont and work from there.
At first I followed the original method of moving the settings and waiting until the sevos vibrated, the problem was they suddenly vibrated so violently I was sure they were going to cook.
As for the I limit, well to tell you the truth I havn't adjusted it. My servos have heaps of torque just as they are, and I havnt even geared them down yet. I recon they would move a car as they are. I guess you just tune one board on the heat sink and then add another when you have finished the last one. It is a strage design to have that I limit where it is.
This is just my experience and not to be an absolute guide. I am happy for anyone to make corrections to anything I have said.
EDIT: If you are using XP just reboot the computer with a startup disk and then run the mouse file and then run the rd990h file. It may pay to have all the files on your bootup disk. Less DOSing around the place. When you boot with the floppy you will eventually see a:\ just type the word mouse and press enter.
then type the word rd990h and press enter. No need to type in the .exe part.
I hope all this helps. Could you please post back with your results.
Thanks