Author Topic: Question about PID controller for Quadcopter  (Read 542 times)

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Offline ammjyTopic starter

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Question about PID controller for Quadcopter
« on: September 17, 2019, 07:34:29 am »
Hello.

Thanks you for your time.

Now, I'm studying one quadcopter simulation model that I found on Github.

that name of simulation is "QuadSim Master" and link is as follows. (https://github.com/dch33/Quad-Sim)
(Already I have sent question mail to publisher, but, it is already 5  years ago project so, I don't think that I can receive answer mail.)

and I have few question about it.

1st attached screenshot show us that PID controller block of Quadcopter.
as you see, P and I controller connected with Phi command.
but, D controller connected with Angular Velocity P.
I don't understand why only D controller not connected with Euler Angles Phi.

another, Theta and Psi controller also same. each D controller of Thea and Psi also connected with Q and R.
I want know reason or clue.


2nd attached screenshot show us that state-space model of BLDC motor.
but, as you see,
A = -1 / (Time Constant of Motor)

B = 1

C =  1 / (Time Constant of Motor)

D = 0

Initial conditions = Initial RPM * (Time Constant of Motor)

//Time Constant of Motor is quadModel.T
//Initial RPM is IC.w1

I can't make any clue that why developer of this simulation made state-space model of Motor with this form.

If anyone know about it, could you give me some clue or advise for these two questions ?
please, let me know.



« Last Edit: September 17, 2019, 07:36:10 am by ammjy »
 

Offline ammjyTopic starter

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Re: Question about PID controller for Quadcopter
« Reply #1 on: September 17, 2019, 01:06:12 pm »
Answer about second question :

Simple RC BLDC motor can be simplified as a first-order low-pass filter and It can be expressed as

w = 1 / (Ts + 1) * wss

where, wss - desired steady-state speed; T - Time Constant

if we express first-order low-pass filter transfer function "w" with state-space model.
it looks same with
A = -1 / (Time Constant of Motor)

B = 1

C =  1 / (Time Constant of Motor)

D = 0

namely,
1 / (Ts + 1) is same with
A = -1 / (Time Constant of Motor)
B = 1
C =  1 / (Time Constant of Motor)
D = 0
« Last Edit: September 17, 2019, 01:12:50 pm by ammjy »
 


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