What does it take to be a "Drive Expert"

D

Thread Starter

David Judd

Hi all,
I have been asked to put together a synopsis on what it takes to be a Drive Expert and would like the input of people who have experience in that
field. I have worked around drives, AC, DC and Servo for a while but do not consider myself an expert. Is this expertise something that can be
gained by education or is it dependent solely on experience? I am looking for what it takes to design drive systems, from drive selection to cabinet layout to electrical drawings. Any feedback would be greatly appreciated.

David Judd
Carolina Automation, Inc.
864.254.0050
 
K

Kaufman, George

David:

Concerning ac servo drives and motors, please visit www.MotionOnline.com and download the Handbook of AC Servo Systems. You can get a very good overview of servo system operation and a
thorough overview of application guidelines. The Handbook also includes a reference of other excellent sources of information for servo drives.

Regards,
George Kaufman
 
D
All,
Thank you for all of the valuable replies both on and off the list. Once again, the List has been a great place to tap into a large experience base.

David Judd
Carolina Automation, Inc.
864.254.0050
 
> -----Original Message-----
> From: David Judd [SMTP:[email protected]]
>
> Ken,
> I wanted to thank you for your prompt and well thought out reply to
> my question. I am new to the controls engineer field and find it a
> great help to be able to 'pick the brains' of some of the people who
> have been doing this for so long. The automation list is a great
> place to do so. I received a number of replies with valuable
> information. I especially like the idea that you brought forth
> about using an Excel spreadsheet to compare possible drive/motor
> choices for an application. Would you be willing to expand on this,
> would it be possible to get a generic copy of what you use?
> I have written a small program for my HP48 calculator that will
> return a minimum HP rating for web handling applications
> but it is very specific.
> It would be great to get my hands on or come up with something more
> generic that could be applied to a broader application spectrum.
> Thank you again for your input and direction.
>
> David Judd
> Carolina Automation, Inc.
> 864.254.0050
>
>
> -----Original Message-----
> From: Ken Brown [SMTP:[email protected]]

> David,
>
> You ask a question that will have as many answers as there are
> people willing to stick their necks out and state their opinion . .
> . that said, here it goes:
>
> First, the drive system is often the bridge between two engineering
> disciplines - Mechanical and Electrical. By far the best drives
> guys I have worked with are mechanical engineers with a knack for
> understanding the electrical aspects of the drive (converter /
> inverter) technology who also posses a strong physics / dynamics
> background. (do I hear groans and hisses from the EEs?) The
> emphasis here is that these guys usually have a better idea of what
> is going on dynamically with the app.
>
> Since most companies divide the responsibilities for a machine
> design among two disciplines, there is often no end to the finger
> pointing that occurs when the machine will not perform due to
> inadequacies in the "integration" of the mechanical and electrical
> aspects of the system. More often than not, those responsible for
> the electrical / software aspects of the machine are hung with
> programming around deficiencies in the mechanical / electrical
> integration.
>
> To be a "drives expert" you need to have a good understanding of the
> mechanical dynamics of the application AND a THOROUGH understanding
> of the capabilities and quirks of the various drive technologies.
> If you don't catch anything else about this thread . . . you will
> still do well to imprint this in your brain and never forget it!
>
> I spent a day last week convincing a cadre of "Corporate Drives
> Experts" that a servo drive and motor would be a sub-standard choice
> for a paper converting application that required high speed
> registration. Knowing the process, the mechanical design and the
> capabilities of ACVector technology made this design choice obvious
> and an easy one to justify.
>
> The evaluation process can include bandwidth, mechanical size, cost,
> accuracy, availability, conformance to corporate purchasing
> standards . . . . the list goes on an on. You also bring up a good
> point about cabinet layout, this is a huge deal when dealing with a
> 700VDC bus drive that is switching currents with IGBT's. Grounding,
> PWM noise, regenerative braking, isolation of signals between drives
> and controllers . . . if you screw this up it will cause you no end
> of pain.
>
> From an education standpoint, the best way that I have found to get
> my arms around the various motor technologies AND the applications
> is to model them on a plain old Excel spreadsheet. My first
> experience doing this was modeling hydrostatic drive systems for
> Tunnel Boring machines for the English channel (Lotus 123 back
> then). I then moved to VF drives on the same application and then
> to Vector drives. Creating a spreadsheet that incorporates motor
> performance (varying swash plate angles at pump and motor, then # of
> poles, frequency, breakdown torque rating, voltage) and seeing how
> the motor reacts is immensely valuable. Plug in the various system
> inertias, gearbox ratios, efficiencies, etc. and now you can swap
> motor/drive technologies and play what if. After you have done a
> few dozen models for different applications / drive technologies . .
> . you get a much better understanding of the strengths and weakness
> of each.
>
> The fact of the matter is that very few people really understand all
> the interrelated systems involved in a motion control application.
> Trajectory planning, axis coordination, (current / torque / position
> / velocity) loops, system resonance, stiffness, backlash,
> synchronization with external events, etc. all are factors that come
> to bear on a motion / drives application. Some requirements are
> more stringent than others, but unless you really know the
> application, you will not know which ones are most important.
>
> It is best to have a strong theoretical background so that when
> confronted with "real" experience that you have a chance of
> correlating observed behavior with a reasonable explanation of the
> laws of physics governing that behavior. I have yet to attend a
> class or course that has done a good job of pulling it all together.
> The danger of presenting a class that supposedly "covers it all" is
> that you give people a false sense of confidence. The best college
> classes that I have to fall back on were the Newtonian physics
> classes and System dynamics classes. This has been followed up by
> much in the way of experience designing custom drives and
> integrating drive systems. IMO . . . the more you know, the lower
> your estimation should be of how much you really know. I learn
> something new about these things we call drives every day!
>
> Hope this helps,
>
> Ken Brown
> Applied Motion Systems, Inc.
> http://www.kinemation.com
 
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