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Engineering How Control Theory can be useful to Mechanical Engineers?

  1. Jul 30, 2016 #1
    I'm a student of Mechanical Engineering and I've been taking classes on Control Theory. Looks like a cool and very interesting field of study, but it seems to be more inclined towards Electrical Engineering (in fact, looks like most jobs on control go to electrical engineers).
    I wonder how a MechE could possibly use control theory, even if they are not full-time control engineers. Is it really useful for mechanical engineers?
     
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  3. Jul 30, 2016 #2

    Vanadium 50

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    Do mechanical engineers ever have to design things that will be controlled?
     
  4. Jul 30, 2016 #3

    Krylov

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    Given your member name, perhaps you find this link interesting, just as an example?

    Development and implementation of an optimized propulsion control system

    This a summary of past thesis work done within a faculty of mechanical engineering in The Netherlands. The thesis itself can be found here:

    https://www.researchgate.net/profile/Arthur_Vrijdag/publication/299354444_Control_of_Propeller_Cavitation_in_Operational_Conditions/links/56f1ab7d08aed354e56fc097.pdf?origin=publication_list [Broken].

    (Disclaimer: I am not the author of this work, nor am I involved in the research on which it is based.) More broadly speaking, I believe there are many uses of control theory for mechanical engineers. Another thing I could think of in a marine context is the control of antiroll tanks.
     
    Last edited by a moderator: May 8, 2017
  5. Jul 30, 2016 #4
    Very interesting links, thank you. Control engineering is a very interdisciplinar field, as I see it, so I think a good understanding of electronics/electrical is required (for programming PLCs, I think).
    So, how much electrical/electronics a MechE should know to be confortable working with controls?
     
  6. Jul 31, 2016 #5

    Krylov

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    I see that this was not answered yet, but I don't think I'm knowledgeable enough to do so. Maybe a practising engineer can join the discussion?

    You could also ask your prof. from your control classes. He knows the local situation, so he may be able to give advice on courses.
     
  7. Aug 1, 2016 #6

    donpacino

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    For my graduate degree I worked on a project team with 3 people ( including myself) on path-finding and control algorithms for a mechanum wheeled car.

    I have an EE background. the other two have a mechanical background. Like you said controls is multidisciplinary. You need to know a bit of everything. Sure the implementation of the control method might be electrical, but the theory and application is very often mechanical. If you want to be a control engineer, you'll need to learn some software. I recommend learning and mastering matlab, it will be your most important tool.
     
  8. Aug 1, 2016 #7

    FactChecker

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    In a futuristic vane, there will probably be controls build into materials to give things the desired properties. Airplane wing flexing/stiffness, buildings surviving earthquakes, electrical control of vehicle shock absorbers, etc. are some of the ideas being developed now. There will probably be more in the future.
     
  9. Aug 1, 2016 #8
    Yeah, I'm starting to learn Matlab right now. Looks like Aerospace has a lot of control and mechanical engineering disciplines working together.

    That's very interesting, indeed. Do you have some links where I could read more about this?
     
  10. Aug 1, 2016 #9

    FactChecker

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    Being able to program in Matlab is very helpful in obtaining a job. It shows a practical capability to apply the theories. Aerospace does have a significant amount of both control law and mechanical engineering. The inner and outer loop control of a plane is usually done with a separate on-board computer system, but the real high frequency stuff of actuators (and hydraulics?) is practically built into the individual devices.
    I'm afraid I don't. You can probably do as well as I can with Google searches. I remember an interesting NOVA series, "Making Stuff: Stronger / Smaller / Cleaner / Smarter" that may have touched on some of those ideas.
     
  11. Aug 1, 2016 #10

    symbolipoint

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    Do a web search about "the red bead experiment" and on the person named "W. Edwards Deming".
     
  12. Aug 2, 2016 #11

    donpacino

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    The actuators and hydraulics are controlled by individual on-board computer systems.

    In aircraft here is the typical flowdown for the controls process

    The systems engineers work to set high level goals.
    The control engineers determine what control laws are needed to meet those goals.
    The electrical engineers make a computer that implements those laws. There are all sorts of inner and outer loops.

    Also another place you'll need control theory that you might not think about. Thermal Analysis. A coolant pump is a control system (you can get destabilization or oscillation in a loop due to bad claw).
     
  13. Aug 2, 2016 #12

    FactChecker

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    I stand corrected. Some systems have separate FPGA controllers to take care of high frequency issues. I think those are usually separate from the actuator devices. They make sure that the actuator positions match the command inputs from the flight control computers. The flight control computers take care of the airplane inner loop stability and outer loop control.
     
  14. Aug 2, 2016 #13
    So, a MechE working with controls in aerospace would work alongside electrical engineers. The control engineers would work on the theory, while the EE's do the implementation. That's right?

    Also, didn't now about the usefulness of control theory on thermal analysis. Very interesting stuff. Are there applications of control theory on fluids, also? Things like turbomachinery, maybe?

    All this flight control, is it usually done by EE's or ME's?
     
  15. Aug 2, 2016 #14

    FactChecker

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    That is reasonable, but not a hard and fast rule.
    The best background for developing flight control laws would be Aeronautical Engineering. There is so much involved in the aerodynamics, equations of motion, and feedback design, that is specialized for that field. The hardware of the flight controls is a good EE application.
     
  16. Aug 2, 2016 #15

    donpacino

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    That entirely depends on the task and the skillset of the engineers. Remember many engineers gain skills in many different areas as they develop. Just because you get an undergraduate degree in meche doesnt meant you will allways be a meche.

    Lets say we're trying to design a sideslip controller. SOmeone with areodynamic knowledge will be needed to model the system. But once the system is modeled, people without aerodynamics modeling can take a crack at it. There are all sorts of levels to controls. You don't need a PHD in fluid dynamics to help design the control laws. You just need someone on the team who knows fluid dynamics.

    You might find yourself writing a kalman filter combining an INS and GPS unit. Although you might consider that EE, many meches work on that type of work as well.
     
  17. Aug 3, 2016 #16

    donpacino

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    You were correct. I replied to your comment instead of navierstrokes and did not mean to imply you were wrong.

    On most modern aircraft there is a dedicated box by the various actuators that does the individual loop closure. It takes inputs from the FCC system (used to be one unit, now distributed) and uses LVDTs to compute the actuator position. It then does any processing it needs, and powers up the actual actuator (*whether hydraulic or electric). It will also send status and fault information back to the FCC system.
     
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