Closed Feedback Loop mechanical system examples

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Discussion Overview

The discussion revolves around identifying examples of closed feedback loop mechanical systems suitable for a controls class project. Participants are seeking simple mechanical systems that can be modeled, linearized, and analyzed for their transfer functions and state space representations.

Discussion Character

  • Homework-related
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant suggests that cruise control is a common example but is not an option for their project.
  • Another participant emphasizes the need for the original poster to share their thoughts on potential systems before receiving suggestions.
  • A participant proposes a system with 1 or 2 degrees of freedom, where the input is a force or torque and the output is velocity or position, but notes that a 3rd order transfer function is required.
  • There is confusion regarding the switching of inputs and outputs in the proposed system models.
  • A home thermostat is suggested as a potential example, but it is dismissed due to prior use in class.
  • One participant describes a saline solution manufacturing system involving a continuous flow of distilled water and a feedback-controlled valve to maintain salt concentration, suggesting it has both continuous and discrete elements.
  • The saline solution example includes a consideration of simplifying the valve control for analysis purposes.

Areas of Agreement / Disagreement

Participants do not reach a consensus on a specific example of a closed feedback loop mechanical system. Multiple competing views and suggestions are presented, and some ideas are dismissed based on prior use.

Contextual Notes

Participants express limitations in their choices based on previous examples used in class, and there is uncertainty about the requirements for the transfer function order.

nakas12
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Homework Statement



Hello everybody I was hoping some of you could give me some some examples of some closed feedback loop mechanical systems.

This is for my controls class where we have to design our own control system. I'm having trouble trying figure out some systems. I know one would be cruise control but that is not an option considering it was shown as an example in our class.

Our goal is to model the system, linearize it and then find the systems transfer function and then find the state space representation.

Any suggestions would be helpful, but please nothing too difficult. Our goal is to use a simple mechanical problem.
 
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nakas12 said:

Homework Statement



Hello everybody I was hoping some of you could give me some some examples of some closed feedback loop mechanical systems.

This is for my controls class where we have to design our own control system. I'm having trouble trying figure out some systems. I know one would be cruise control but that is not an option considering it was shown as an example in our class.

Our goal is to model the system, linearize it and then find the systems transfer function and then find the state space representation.

Any suggestions would be helpful, but please nothing too difficult. Our goal is to use a simple mechanical problem.

It would be best if you would post your thoughts on such systems first. We don't do your homework for you here (which you know), but we should be able to suggest some systems for you to think about and build upon, as long as you show us your thoughts first. I have a few good suggestions for you, but would like to see how your are thinking about this school project first...
 
Ok sorry about that. But I'm thinking of having a system with either 1 or 2 degrees of freedom. I was thinking of a simple system where the input would be a force or torque and the output could be some kind of velocity or position.

The transfer function our professor wants though is a 3rd order or more.
 
nakas12 said:
Ok sorry about that. But I'm thinking of having a system with either 1 or 2 degrees of freedom. I was thinking of a simple system where the input would be a force or torque and the output could be some kind of velocity or position.

The transfer function our professor wants though is a 3rd order or more.

Wouldn't the inputs and output be switched from what you propose? Maybe I'm not understanding the systems you want to model...
 
Umm I guess. Now I'm a little confused about what you mean. A system that was applied a force such as a car would have a certain velocity that it would to reach like cruise control.
 
How about a home thermostat? The system would include the heater, room heat capacity, etc.
 
Unforunatley no I can't use that system. It's been used before too many time apparently.
 
Ok, you're manufacturing saline solution for medical use. You start with distilled water continuously flowing into a tank at a constant rate, and a valve that drops salt from a salt container into the tank. A pair of electrodes measures the salt concentration and controls the valve so as to set the concentration to the desired level. Fresh distilled water continuously pours into the tank so the valve will be shutting on and off to keep the saline level constant.

(Salt when dropped in water ionizes almost completely so the water's conductivity is a measure of saline concentration.)

This feedback system has elements of continuous as well as discrete subsystems in it.

If you have trouble with the on-off valve, you could assume a continuously variable valve aperture to control the flow of salt continuously rather than the way a house furnace turns on & off. the analysis would be simpler in that case.
 

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