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Question about PID controller for Quadcopter
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ammjy:
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.
ammjy:
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
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