servo motor control

sevensages

Member
Join Date
Mar 2004
Posts
22
hi all,

what are the basic design parametes for a servo motor control which have to rotate a table (load) of 45 kw in 0-360 degree positions, combined with vertical & horizontal movement control. further this motor control will communicate with a centralised plc, which i m takin care off. but regarding servo motor control i am in total dark. plz. help.

regards
 
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I find that this web site is good:

http://www.sew-eurodrive.com/

Go to the documentation page and do a search on:
Drive Engineering - Practical Implementation - Volume 7

This is a pretty good introductory handbook, although it is based on the older 'Movidyne' series drives. The more modern ones are similar to the movidynes, but better.

Hope this helps,

Doug
 
I STRONGLY recommend you get some professional assistance with this. Trying to get a multiaxis servo system going without any experience will cause you and the person paying for you a lot of trouble.

Modern servo systems are a lot easier to get going than the older ones, but they still take some real knowledge and understanding to get them to work well.

Can you tell us more about your system? What PLC and what is the application? How far does the load move, in what time? Do you plan to use gearing? What is the inertia of the load, and do the axis need to be coordinated?

All these are important questions that you will need solid answers to before even beginning to engineer the system.
 
dear philip,

its a car parking lot, where the car is washed & some other maintenace jobs will be going on. after that the car will be placed in parking quee. now data available with me -

1) weight of the washing/maintenance table which has to rotate in between 0-360 degree, is 45 kg. speed in this purpose is not a factor but precision positioning has to be within 5 degree range.

2) load of the car (four wheelers only, no heavy duty) varies.

3) after washing/maintenance the table will lift the car from 0
position to 10'/20'/30' height. then at desired height it has to be lifted up & to be placed at pre-determined space. this horrizotal movement is min. 4' & max. 80'.

now i am going with Modicon premium range plc with vijeolook SCADA. there are other operations like entry & exit gate control, fire alaram, auto traffic system, Survileance camera control which can be controlled through plc.

as you proposed to have assistance from some experinced guy, thats is what i am lacking of. further i am totally in-experienced with servo. so what u suggest next.........

p.s. thanks to philip for the link. i am going through the manual. be there guys if i have to clarify something.
 
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From what I can understand I think this is NOT a servo application. I would suggest that using standard induction motors, with high performance sensorless vector VSD's controlling their speed is the correct way to go.

You will need to arrange for significant gearing 1:20, maybe 1:50. There are lots of ways to use a VSD to control position quite effectively for this kind of application.

The main thing will be to use a VSD which has the ability to FULLY control the motor torque all the way down to zero speed, or as close as is needed. These drives are usually called "sensorless vector"...but do not be fooled by all the advertising. My first two choices would be AB's Powerflex 700's or ABB DTC drives, and there are others that are very similar....but there are many, many other drives on the market that DO NOT offer the same ability to control torque.

Servo motors are usually used for much higher speeds, lighter loads and much more precision than you need for this job. Using a servo will be a waste of your money and time.
 
Iwould use hydraulic motors

I would use a SSI absolute encoder for position feedback
5 degress would be easy.

The rotation part could be done with an electric motor but when the lift part was mentioned then it is time to consider hydraulics for everything. I have customers that have done this sort of thing storing recreational vehichles and small trucks.
 
Have to agree with Philip,

The servo control can easily get you 0.1 degree accuracy or better.
If you don't need that accuracy, then a servo is overboard.
You could even use a geared down DOL if speed is no problem. If you wanted some extra speed, a 2/8 pole changing motor may work just as well. I found that DOL with absolute encoders can be suprisingly accurate and repeatable.

The other suggestion of using hydraulics for the lifting component would be the best.

Hydralics and DOL is also good because it is easy to understand for most trades level people, and therefore easy for them to maintain.

As for the variable load, DOLs built for a heavy load tend to have no problems at lighter loads, and hydraulics can be run at constant speed over a wide range of loads.

Hope this helps,

Doug
 
Thanks to you all.

I am conversant with sensorless vector control drives. You suggest that it will serve the purpose along with hydraulic controls. Ok. Now let me re-design the system with absolute encoders & propose to customer. As servo control was speciifed i was totally confussed & i have to rush after you.

Just one more thing apart from Ab's or ABB's I think Telemecanique range drive do also have sensor less vector control. Is there any problem from your point of view.

regards.
 
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sevensages said:
Now let me re-design the system with absolute encoders & propose to customer. As servo control was speciifed i was totally confussed & i have to rush after you.

Rockwell has a new motion module for the Control Logix that works like the M02AE. It is called the M02AS and it can interface to SSI rotatory absolute encoders ( 10-32 bit ) or linear MDT ( Tempsonic or Balluff ) rods. The three modules I am familiar with ( M02AE, M02AS and HYD02 ) all work pretty much the same way with the same motion blocks.
 
danatech said:
hmmmm, i think i'll just keep washing my car the old-fashioned way; "drive real fast in a heavy rain"! :D

Yes, and hydraulic oil is environment crime.

VFD and ABS-Encoder in filedbus gives as good accuracy as ABS can.
 

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