Post on 01-Apr-2015
Feedback Speed Control
Embedded Systems Interfacing
Overview Background Task 1 MATLAB® Step Response Root Locus Task 2 Scaled Coefficients Task 3 Proportional-Integral Speed Control Task 4 Step Response for:
Critically Damped Over Damped Under Damped
PWM/Motor Speed Labs
ADC
+5 VDC
PWM
+12 VDC+5 VDC
PIC24FJ128
TD62003AP
LM2907
V(speed)
Open-Loop Load-Speed Characteristics
Speed
Load
Block Diagram
_k(z-b)___
z(z-1) B_ (s+A)
-
+ R(z)
Y(z) U(s) E(z) ADC
Y(s) DAC
U(z)
InternalTo
feedback.cPIC24FJ128
Darlington Driver,Motor and
Freq-to-Volt
PID Controller Time-Domain
Laplace-Domain of PI Controller
dt
tedKdtteKteKtu DIP
s
KsK
sE
sU
KKK
Kss
KK
sE
sU
IP
PID
DI
P
0 and 0 ,0
PID
Stability Control Ratio
Critically Damped
I
I
KBsAs
KB
sR
sC
2
B
AK
KBA
cab
I
I
4
014
04
2
2
2
Control Algorithm
Tnene
Knunu
nTTnnene
Knunu
I
I
2
))()1(()()1(
12
))()1(()()1(
Task 1 – Step Response Analysis Within MATLAB®
Define A and B Define transfer
Function Use step()
Task 2 – PID Gains
Condition K1 = 1024k K2 = bK1
Under Damped
Critical Damped
Over Damped
Unstable
Task 3 Within main( ) Initialization
RD0 Timer 3 ADC Interrupts and Timer 3 Interrupt PWM ADC PMP then LCD LCD text on screen
Task 3 Within main( ) Endless Loop
Wait for for semaphore == 1 Clear semaphore Calculate new output value using
difference equation Write to PWM Update out(k+1), in(k+1), and in(k+2) Display Speed
Task 3 Within Timer 3 ISR Clear Interrupt flag Start sampling
Task 3 Within ADC ISR Get new speed reading and clear DONE Set semaphore Check for one-hundred passes (100 x
50ms = 5 s) If 100 passes then
Toggle RD0 Calculate new reference = Step*D0 + Offset Reset pass count
Else Increment pass count
Clear ADC interrupt flag
Task 3 Download to project
folder feedback.c peripherals.a (library
archive) peripherals.h
Create project and add all three files
Add linker script Create heap
Open-Loop Load-Speed Characteristics
Speed
Load
Closed Loop
Open Loop
Task 4 Use Internal Reference Use MPLAB’s Data Monitor and
Control Interface to Adjust K1 and K2 Capture Image on MSO and repeat for
Critically Damped Over Damped Under Damped
Data Monitor and Control Interface
DMCI Configuration
Right Click
DMCI Use Press Save after
Dynamic Data Control is configured
Press Halt Adjust Sliders
Use Mouse Up arrow and
Down arrow Press Start