R90H Servo Drive

[Verboten]

Hello!

I have a couple of higher voltage DC brush servo motors and am thinking about purchasing the R90H drive.

My questions:

How hard is it to tune this drive for a motor? I'd like to use it to test a few motors on and am wondering if this will be a pain.

200 volts at 40 amps seems like quite a bit of power to pass through something so small. Would it really be possible to run a 200 volt motor at 40 amps continuously on this drive? (I won't be using that much power - but it would be nice to know)

This drive will need a pretty large heatsink (?) - wouldn't this make it pretty hard to use it with their motherboard?

Any input will be greatly appreciated! Thanks!

[peterklos]

HI Contact To: 'Vladimir Huzevka at Rutex on mail@rutex.com he is the manufacturer of the boards and I have found in the past he is very helpful.

Peter

[intek cnc]

I'm using r90h drives in retrofitting my knee mill. I'm having trouble getting them set up. my first proublem is that the tuning software dose not run under XP. I also can't get the servo to ocillate by adjusting the Ki as decribed in the tuning guide. And last I can only jog the servo in the clock wise dirrection. I'm using Baldor 120 volt 39 amp servos, and Mach2 software. Can anyone help?

[ger21]

If you don't get any help here, try asking on the Mach2 yahoo group. I thought I read something there about a Rutex tuning utility included with Mach2.?

Gerry

[ynneb]

intec, I have just tuned my rutex drivers using the rutex tuning software in win 98.
It really is worth using it. You can see where you have turned the pots on the computer screen.
Before I tuned the servos I was getting about 200 pulse overshoot before they would return to where they should be. With the software I have tuned them down to zero overshoot. That means from full speed spinning the servos stop with no overshoot what so ever. I find it amazing that a servo can stop like that. I use 2000 pulse encoders.

I recomend installing 98 on another partition just for this purpose.

When you say you cant get it to osillate, I discoverd that if you spin the servo a bit it will start to osillate violently. You will get a shock the first time. They wont osillate if the encoders are in the correct position.

[intek cnc]

YNNEB,
Thanks for the help. How can I be sure what pulse my encoders are? 1000, 2000, etc. I'm not sure what I have and don't know how to tell. The servos and encoders that I'm using are from the old cnc control that was on the machine, autocon delta20. I'm thinking that knowing this maybe part of my problem.
What servo, encoder combination are you using?

[Monte]

Intek CNC,
You can use the Rutex tune program and winxp, in a round about way. You have to create a dos boot disk and boot to dos, then run the tuning program. Make sure you copy the program to some directory on c:\, like c:\rutex. Long file/folder names are a hassle in dos. I'm running xp and building up a rutex controller, I've tuned my servos this way.

Monte

[ynneb]

Yes Monte is right, I also discovered doing what he suggested about using the boot disk.

You asked about finding out how many pulses your encoder is. With the test sostware you can tell the servo to spin a certain amont of pulses. First try 500, then 1000 and so on untill you note that the servo spins and stops exactly one revolution. It may be a bit of trial and error, but it wont take long to figure it out. Put a peice of tapes on the servo spindle and another on the servo casing, put a pen mark on each tape and line them up. This will show you if the servos completes a full spin.

[Monte]

ynneb,
When tuning the drivers did you have anything attached to the motor shafts? I've been trying to get a 'cut and dry' description on how to tune the drivers and it's still a little fuzzy to me. I've tried it with and without weight on the shaft. My first attempt was with Gecko drivers and it's all by feel unless you have a scope. Sold them and got the Rutex.

Anyway the short of it is could you describe your tuning proccess a little? And how did you adjust the pots in the center of the boards with them attached to the motherboard?

Thanks,
Monte

[ynneb]

Yes, there is a error in the rutex pdf picture of the pots and thier labels.
I am sure Vlad hates me for all the emails I sent him for all the dumb questions i asked him.
Trust me you are not dumb by having a hard time doing it. I was intending to do a step by step guide of what to do. I am sure I will give a better explanation. Give me a few hours to write the guide down and i will post it. I am wondering two things, either other rutex users are very clever working out what to do from the rutex instructions, or they have shelved them.
Back in a few hours.

[Monte]

Originally posted by ynneb Yes, there is a error in the rutex pdf picture of the pots and thier labels. I am sure Vlad hates me for all the emails I sent him for all the dumb questions i asked him. Trust me you are not dumb by having a hard time doing it. I was intending to do a step by step guide of what to do. I am sure I will give a better explanation. Give me a few hours to write the guide down and i will post it. I am wondering two things, either other rutex users are very clever working out what to do from the rutex instructions, or they have shelved them. Back in a few hours.

Wow, that would be great. I can see getting at Ki, Kd and Kp, but the other one looks a bit tricky. Unless you only go at one board at a time. I bought the motherboard, but not the IO board. I think I need that in order to use the motherboard, which I'm not at this time.

Monte

[ynneb]

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