Kuka robot project - hardware choice

I'd like your help in organizing my project.

i managed to recover a KUKA Kr15 robot but without the control bay.
and i'd like to get my hands on it and learn all about it. “Denavit-Hartenberg (DH) parameters”, ‘genserkins’ ...

After calling KUKA, they told me that only their KRC1 with old electronics was compatible with the KR15-1.

So I'd like to go with linuxcnc.

my first question is about the harware:

after several searches, i could see that the motors were siemens servos with a kuka label. the encoders seem to be cos/sin.

www.robot-forum.com/robotforum/thread/32...0-servomotor-pinout/

As for motor control, I'm a bit confused, on the motor nameplate you can see 1.5A / Uistr 146V / 6000/9000tr. they are in 3-phase AC.

after a long search on drivers, i find many with 200V -400V. I see that all the drivers have an encoder input. Is it wiser to connect the encoders to the drivers or to the mesa card? Are there AC drivers without encoder feedback?

-can a mesa card read cos/sin encoders? or do you need a card between the encoder and the mesa card?

 

All Kuka robots i have worked with have resolvers on motors, that is the sine/cosine thingy, not encoders. Those were KR150 and KR320, so much bigger.
Mesa has something that can read resolvers, but you need to find the exact model of the resolvers to know for sure.
Motors might also use something for comutation, but not sure if that is also done from resolvers.
I did a lot of wiring on one of those, but never needed to mes with motors or drives as all were working.
I was not on robot forums for a long time, i was the one who posted the hack to make Kuka robots work in Auto mode when they are factory disabled. They are usually controlled by a central computer for synchronization.

Pico systems also has resolver to quadrature converters that can make the resolver signals usable with standard drives. We also have brushless drives that sound like they can drive these motors. Our PWM controller can drive our brushless drives.
Jon

thank you for your feedback.

- yes, I was mistaken about these motors, they're not called encoders but resolvers.

-how to recognize the model of my resolvers?
motor :1fk6032-6AK71-1ZZ9
doc : cache.industry.siemens.com/dl/files/364/.../v1/PFK6_0503_fr.pdf (sorry is in french)
but the resolver reference is not indicated ... zz is not in the command reference.
i found this video on youtube that look like my motor :

on my motor i have a 12 pin connector but only 8 pins are functional.
To finish with my questions about the cos/sin resolvers, is it indicate absolute position or relative position?

-For Pico systems,do you think your brushless PWM servo Amp can drive my motor and the robot's largest motors? (unfortunately, I don't have the nameplates of the largest motors, but I was able to look up on a kuka KR16 that the motors are 2.5KW 5.4A 185V).

 

greg23_78 wrote:

-For Pico systems,do you think your brushless PWM servo Amp can drive my motor and the robot's largest motors? (unfortunately, I don't have the nameplates of the largest motors, but I was able to look up on a kuka KR16 that the motors are 2.5KW 5.4A 185V).
 

Well, the 185 V is an issue, we do not recommend running over about 122 V DC on our servo amps, so that would limit the top speed to about 66% of the rating.  The 5.4 A is not an issue, our amp can go up to 20 A peak.
In principle, resolvers are somewhat absolute,  but if you convert them to quadrature, then you lose the absolute alignment, and have to perform a homing procedure whenever you start the control software.

Jon

ok, so the 160 V on your website corresponds to a peak voltage?
For the input voltage, for reasons of economy, a DC power supply to manage the 6 motors is likely to be expensive.
What's more, being in Europe, I have to manage with 240/400 volts. It's easier to find an auto-transformer to output 110V and add a 3-phase bridge rectifier with capacitor.
is it possible to supply your amps with RMS voltage?

for resolvers, is there a way to manage robot position data with batteries (like kuka) without continuously powering the computer with linuxcnc open? because manually homing robot axes could take a long time ...
 

In Europe you can get toroidal transformes for any secondary voltage, that is the easy part, the 5.4A rating is most probably the long term current the motor can withstand, peak current will be much higher so the drives are usually 20A or 30A rated, hence the power supply must be rated accordingly, in your case at a guess at least 60A transformer and rectifier. Or have 2 of the big motors on one power supply and 4 smaller on another power supply, at 30A to 40A each are easier to manage and find and might even be cheaper. You might easily make do with much less as it is a small weight, and use moderate accelerations.
Does the control box have power info on it? Should be in KW,

i don't have the electrical cabinet with the robot
i'd like to start with a second-hand 400 to 240V high-power three-phase autotransformer because it's “quite easy to find”. i'd like to share the phases and neutral to supply the drivers with 110V single-phase power.
i have 3xbig motor and 3xsmall motor so 1 phase for 1 big and 1 small.
after some research i managed to find some data on robot or control electrical power.
robot KR16(more recent than my robot but quite similar) = Installed motor capacity 8.8 KW
cabinet : Rated power input depending on the drive class: 7.3 -- 13.5 kVA.
I don't know which transformer power I should look for 12 KVA minimum? 400V/18.1A - 230V/31.4A

assuming that large motors will be at a maximum of 50%-60% of their maxspeed (110V instead of 180V)

KR16 powerKW
 

KRC2 power KW
 

 

I have a feeling you are using the "autotransformer" name wrong, that is the name for the round transformers with a big rotating knob at the top that can adjust the output voltage in a wide range.
Nothing wrong with that, but autotransformers are much more expensive and finding a 3 phase one will be a stretch. 3 of single phase ones should also do just fine.
- some ideas:
-3 of normal transformers, at least 3KW each, should be easy to find torroidal ones at any output voltage and are quite cheap. If you can choose, get the 400/110V ones, saves quite a bit on mains cabling as the current draw is smaller.
-a big used 3 phase transformer, usually with multiple input voltages 380/400/420/460/480V, at 10 to 15KW easy to find from used machines, usually not cheap at all, usually 200 to 220V outputs.
This should still be usable for 110V AC as you can wire inputs with common neutral for 3x220V and get out roughly from 100-125V depending on what input windings you use.
-
If you go for the used version, do try to find matching rectifier, at those current requirements the rectifier gets pricey.

greg23_78 wrote:

ok, so the 160 V on your website corresponds to a peak voltage?
For the input voltage, for reasons of economy, a DC power supply to manage the 6 motors is likely to be expensive.
What's more, being in Europe, I have to manage with 240/400 volts. It's easier to find an auto-transformer to output 110V and add a 3-phase bridge rectifier with capacitor.
is it possible to supply your amps with RMS voltage?

 

Sorry, I really ought to change that.  The amps won't blow up at that voltage, but you have a high probability of having nuisance trips of the overcurrent fault logic.  So, I really recommend 122 V as the highest DC supply voltage.
for resolvers, is there a way to manage robot position data with batteries (like kuka) without continuously powering the computer with linuxcnc open? because manually homing robot axes could take a long time ..

For the input voltage, for reasons of economy, a DC power supply to manage the 6 motors is likely to be expensive.

A simple power supply can be built with a transformer, rectifier and capacitor bank.  In the US, there are commonly-used "step down transformers" that have split primary and secondary windings.  These can be strapped to give various voltages, and are used in large machine tool controls to provide 120 and 240 V from 480 V mains. These can often be found at scrapyards for the salvage metal price. To get 122 V DC with a capacitor-input filter, you would want about 86 VAC from the transformer.  Possibly this can be arranged with a buck-boost autotransformer before the isolation transformer.  If you can find suitable tranformer(s) surplus, this can be done quite cheaply.  The amps definitely need isolation from the mains, and DC input.

for resolvers, is there a way to manage robot position data with batteries (like kuka) without continuously powering the computer with linuxcnc open? because manually homing robot axes could take a long time ...

Our resolver converters have no way to provide absolute position via quadrature output.  That's one of the reasons why some vendors use exotic absolute encoders.  Also, most robots have gearing on the joints, so the motors make many turns for the full motion range.  Fanuc serial encoders, for instance, report # of full turns from the home position, but need a backup battery..
Homing should not be a huge issue, especially if the robot is placed in a good pre-home stance when LinuxCNC is shut down. LinuxCNC can do a sequenced home procedure where each joint is homed in a specified order to be safe.

Jon