Need help interpreting a college class Labview assignment and advice on my work so far

[New-bee-Labview]

Hello everyone,
I am a college student working on an assignment and need some advice, as my lecturer is unreachable for advice.Any and all help is greatly appreciated.

1. First would be help on how to interpret the 4th task of my assignment ( picture attached).Does closed loop system in this case mean develop a PID controller? or does it simply mean the whole thing is in a continuous loop?

2) second issue is , when simulating the voltage i opted for using a digital wave with noise rather than random number generators as i think it closer to what output from an ultrasonic sensor would be like( picture 2 ). Is this correct or should i stick with random number generator( i ask because all my classmates have used the Random number gen).

3) any tips on improving my design would also be appreciated , and tips on PID implementation ( if needed)

  

[altenbach]

We can't really judge code pictures containing express VIs, because most of it is hidden. Why do you throw away all simulated data except for the first point? Seems wasteful. I really doubt you need any formula nodes.

Closed loop is typical for control systems where a response serves as input to the next iteration. Did you try to do a google search?

[Kevin_Price]

The 4th task sure *sounds* like it expects you to develop a control scheme, and PID would surely be one possible type.  However, in my opinion the task description seems incomplete. 

   Yes you can define a distance set point, calculate your average measured distance, and develop your error signal.  But then what?   In real life there'd be some kind of actuator and some kind of "plant" that the actuator operates on to drive the error signal toward 0.   But the assignment makes no mention of how you should simulate any such actuator and plant.

   I suppose one thing you could do is incorporate the error signal as a factor you use when simulating the ultrasonic sensor.  Perhaps you let the nominal amplitude of your sensor be a simple function of the error signal?   And perhaps that simple function can start by being the P term of a PID controller?

As to the noise simulation.  I like your idea of generating noise with realistic characteristics, though I can't judge what "realistic" should be for an ultrasonic sensor.   On the other hand, noise that looks discontinuous and chaotic from sample to sample can be a problem, especially when you're trying to wrap a control loop around it.   

   It's maybe beyond the scope of this assignment, but I might be tempted to simulate most of the noise as a kind of "random walk" because the *rate* at which a random walk migrates around the nominal value tends to be much more subdued, and thus much friendlier to a control loop.

-Kevin P

[Bob_Schor]

I'm going to focus on Question 2, simulating "noise" in measurement of a signal.  Have you (not?) taken a College-level Engineering class on Signal Theory?  What do you think about when you hear the terms "Signal" and "Noise"?  If you are interested in simulating a "noisy Signal", how would you characterize the "Noise"?  [I'm trying to get you to think about what "noise" is, and how you would simulate it.  You are partially on the right track thinking that Random Numbers are involved, and LabVIEW does provide a Uniform Random Number generator ...]

Bob Schor

P.S. -- I'd definitely give Extra Credit for a "reasoned solution" that was more complex than simply tacking on the output of LabVIEW's Random Number function to your simulated "true" measurement ...

[New-bee-Labview]

hi , thanks for the reply . Really appreciate it

I am using formula node to convert Voltage to distance. I am completely new to labview so if there is a better way of doing it please point me in that direction.

You mentioned im losing data( didnt realise) , is that because of the formula node?

[wiebe@CARYA]

---

@altenbach wrote:

Closed loop is typical for control systems where a response serves as input to the next iteration. Did you try to do a google search?

---

Isn't a feedback mechanism the definition of a closed loop?

[altenbach]

---

wiebe@CARYA wrote:

---

@altenbach wrote:

Closed loop is typical for control systems where a response serves as input to the next iteration. Did you try to do a google search?

---

Isn't a feedback mechanism the definition of a closed loop?

---

Yes, I could have been more clear. With "response" I meant the measured signals defining the system state. For example for a room thermostat, the "response" of the system is the measured room temperature which, when compared with a setpoint,  is then further used to adjust the heater in a closed loop. Sorry, English is not my primary language. 😉

[wiebe@CARYA]

---

@altenbach wrote:

---

wiebe@CARYA wrote:

---

@altenbach wrote:

Closed loop is typical for control systems where a response serves as input to the next iteration. Did you try to do a google search?

---

Isn't a feedback mechanism the definition of a closed loop?

---

Yes, I could have been more clear. With "response" I meant the measured signals defining the system state. For example for a room thermostat, the "response" of the system is the measured room temperature which, when compared with a setpoint,  is then further used to adjust the heater in a closed loop. Sorry, English is not my primary language. 😉

---

It was actually (at least 50%) serious question. English is my third language. I consider LabVIEW my 2nd.

Process control is hard. Thanks for confirming that my basic understanding of it is correct.