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Homework Help: Electrical position feedback for hydraulic servomechanism

  1. Apr 6, 2016 #1
    1. The problem statement, all variables and given/known data
    Assume that you are employed by a company that manufactures hydraulic servomechanisms. You have been asked to recommend an electrical method of providing position feedback rather than the mechanical method used at present (pictured below).

    The demand signal has been chosen to be a d.c. voltage. Cost-effectiveness and reliability are essential.

    Examine position sensor options and select a cost-effective and reliable solution. Justify your choice.

    Sketch a closed-loop block diagram of the modified hydraulic servomechanism, identifying the sensor, its signal conditioning and the form of error detector. You can assume that the servo valve will
    be operated by a progressive solenoid that receives its operating current from a voltage-to-current converter


    2. Relevant equations


    3. The attempt at a solution

    I am looking for some guidance on this question. I believe it is asking me to change the mechanical link to some type of position sensor. The output of this sensor will then need to feedback to the solenoid valve and adjust its position. This will then intern change the position of the hydraulic ram (output). ultimately I think the purpose of the system is to ensure that the ram is returned to a central position if the input position changes.

    Selecting the position sensor. I think the obvious option would be to use an LVDT. Would this be correct?

    I have come up with this block diagram for the new servomechanisms. I am not totally sure that it is correct. should I be looking at proportional control or integral action instead?

  2. jcsd
  3. Apr 7, 2016 #2
    You could talk to local companies that provide control systems. Some of them, I'm sure, would be glad to send you literature explaining what their various devices do. An in-person visit is even better. Maybe call and see if you can set up an appointment with one of their application engineers. I did this waaaaaay back when I was in engineering school (not the same problem, but similar) and was inundated with information and explanations. I learned a lot.
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