How to Convert Lead Compensator Output to PWM for Hexacopter Height Control?

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Discussion Overview

The discussion centers around the conversion of lead compensator output to PWM for controlling the height of a hexacopter. Participants explore the relationship between PWM signals and thrust generation, as well as the implications of specific constants derived from motor tests.

Discussion Character

  • Homework-related, Technical explanation

Main Points Raised

  • One participant seeks hints for converting lead compensator output to PWM, noting that a scaling factor of 0.1956 N/PWM is established for their hexacopter's motors.
  • Another participant questions the meaning of 143 PWM, seeking clarification on the units for the scaling factor and the implications of PWM values exceeding 100%.
  • A third participant provides insight into the derivation of the scaling factor, explaining that it is based on a linear regression from motor tests conducted between 150 PWM and 170 PWM.
  • A later reply clarifies that the Arduino board uses a PWM range of 0-255, where 0 corresponds to a 0% duty cycle and 255 corresponds to a 100% duty cycle.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the interpretation of PWM values and the scaling factor, with no consensus reached on the implications of the PWM range or the meaning of specific values.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about PWM signal interpretation and the specific conditions under which the scaling factor was derived. The relationship between PWM values and thrust generation remains partially unclear.

Who May Find This Useful

Individuals interested in control systems, hexacopter design, or PWM signal applications may find this discussion relevant.

huntflex
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Homework Statement



Hello, I'm not looking for an answer to my problem, just some hints. Any help would be greatly appreciated.
I am required to control a hexacopter, so I'm designing a lead compensator to control the height, it should be able to counteract the pull of gravity. So far I have designed it, but my problem is that I need its output to be in PWM form.
I already have a scaling which is a= 0.1956 N/PWM, it is also given that a value of 143 PWM will generate hover thrust.(These constants are found from tests on the motor, and are for all 6 motors).

Homework Equations


I realize that the feedfwd (see block diagram) should be some value, but I don't know what.


The Attempt at a Solution



Attached is a snapshot of the block diagram.

Thanks for any help :)
 

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I've long since forgotten my control theory but what does 143PWM mean? What are your units for PWM in a= 0.1956 N/PWM ?

Is it a = 0.1956 Newtons/percent ?

If the pulse width modulation can vary from 0% to 100% how can you have 143%
 
That is actually a very good question, what I can see from the data that was given to me is that the transfer function for the motor was derived by subjecting it to steps from 150 PWM to 170 PWM, from there a linear regression could be made, and from there it is derived that the slope is a = 0.1956 Newton/PWM. Which means for every PWM sent in, 0.1956 Newton is added to the system.
 
I just found out, that it's how the Arduino board works, you write 0-255, where 0 is 0% duty cycle, and 255 is 100 % duty cycle
 

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