Download Why Feed-forward Controller?

Internal Model Control
for
DC Motor Using DSP Platform
By: Marcus Fair
Advisor: Dr. Dempsey
Outline
Problem description
Objectives
Functional Specs
Sub-system Overview
Software
Design
Summary
Design, build, and test IMC (Internal Model
Control) system to control a DC motor
32-bit TMS320F2812 digital signal processor
(DSP)
Design for IMC controller built in Simulink
Input to system uses graphical user interface
(GUI) built in Matlab
Preliminary Work
DC Motor block diagrams from Senior Miniproject
Also based on DC Motor Speed Control Demo
M-files to run software
Speed Measurement block in Simulink
Common Problems in Control
Systems
Load Changes
-Load shaft
Plant Changes
-Armature Resistor, Armature Inductor, Rotor Inertia, etc
Power Supply Changes
Objectives
Build DSP/motor hardware interface
Design and build (GUI)
Design closed-loop controllers
Compare conventional controller results
with the IMC method
Functional Requirements and
Performance Specifications
Closed-loop operation: Determine optimum
gains for controllers
Rise time: 20 ms or less
Settling time: 100ms or less
Overshoot: < or = 5%
Steady state error: + or – 5 RPM
Equipment List
GM9236C534-R2 Pittman DC motor
Ezdsp F2812 Board
LMD18200 H-bridge
3 - SN74LVC4245A voltage shifter
6-Pin DIP Opto-isolator
2N2222A BJT
2 - Diodes
Agilent 30V power supply and HP 5V power
supply
Tektronix Oscilloscope
Overall Block Diagram
Overall Block Diagram
Dsp board technical specs
Generation
TMS320F281x
CPU
1 C28x
Peak MMACS
150
Frequency(MHz)
150
RAM
36 KB
OTP ROM
2 KB
Flash
256 KB
EMIF
1 16-Bit
PWM
16-Ch
CAP/QEP
6/2
ADC
1 16-Ch 12-Bit
ADC Conversion Time
80 ns
McBSP
1
UART
2 SCI
SPI
1
CAN
1
Timers
3 32-Bit GP,1 WD
GPIO
56
Core Supply (Volts)
1.9 V
IO Supply (Volts)
3.3 V
Inputs and Outputs
H-bridge
Delivers up to 3A continuous output
Operates at supply voltages up to 55V
Low RDS(ON) typically 0.3W per switch
TTL and CMOS compatible inputs
No “shoot-through” current
Thermal warning flag output at 145°C
Thermal shutdown (outputs off) at 170°C
Internal clamp diodes
Shorted load protection
Internal charge pump with external bootstrap capability
Internal clamp diodes
Shorter load protection
Internal charge pump with external bootstrap
capability
Pittman DC Motor
Motor Specs
Part #
GM9236C534R2
Gear ratio
5:9:1
No-load at
30V
834 RPM,
current 100
ma
Encoder Specs
Input Voltage
5V
Resolution
512 ppr (before gear
reduction
Pittman Motor Block Diagram
t
Clock
Velocity
To Workspace
To Workspace1
1
1
0.0582
0.00424 s+3.91
0.00000706 s+0.00000354
Step
Scope
kt
EE side
0.0582
kv
ME Side
Root Locus of Plant
Bode Plot for Plant
Software
Matlab
-Simulink
-main m-files
-Gui m-files
Code Composer Studio
2.0
-Auto-code
generation
-Communication
with Dsp board
Software flowchart
Software flowchart
Design Work
Matlab GUI
-Gui m-file
Controller Design Iterations
-Proportional Controller
-Feed-forward Controller
-IMC controller
GUI
Proportional Controller
Target Speed
Set
Speed
Reference
Feedback
----------> DC MOTOR ------------>
&
OPTICAL ENCODER
Speed in RPM
Measure
Speed
Speed
Correction
Build/Reload
& Run
F2812 eZdsp
Proportional Controller
Take Samples
1
Reference
2
Feedback
Subsystem
90
Gain
Convert
Data Type
Conversion
C281 x
W1
PWM
C28 x PWM
Other Block diagrams
From RTDX
mfichan 1
double
From RTDX
Data Type Conversion 1
ref
1
Target Speed
C281 x
cnt
QEP
C28 xQEP1
In1
Out1
theta
In2
Generate Theta
dir
Speed RPM
Speed Measurement
43 .3
Terminator
DMC
freq
Convert
1
Out 1
Data Type
Conversion
1
Take Samples
Shaft Encoder
Resolution
Direction
Subsystem
Proportional Controller
Error
Command signal
Gain
90
.0001
Output
1937362
6
s2 +922 s+113296
Step
Gain
Unknown
RPM conversion
Sampling
0.001
29 .29
H-bridge
Transfer Fcn
Quad Gain
4
Feedback signal
simout
Clock
To Workspace
Rotary Encoder
81 .5
Proportional Controller
Simulink Results
Proportional Controller
Actual Results
Proportional Controller
Actual Results
Feed-forward Controller
Why Feed-forward Controller?
Faster response to command changes than
single-loop controllers
Less overshoot: More accurate than single-loop
controllers
Better system for Dc Motor control
Feed-forward Controller
0.001149 z2 -0.0015 z+0.0004378
z2 +1.889 z+0.892
Feedforward
Target Speed
Feedforward
Reference
----------> DC MOTOR ------------>
&
OPTICAL ENCODER
Speed in RPM
Feedback
Set
Speed
Measure Speed
Speed Correction
Build/Reload
& Run
F2812 eZdsp
Feed-forward Equations
C/R = (Gc*Gp + Gp) / (1 + Gp)
Desired C/R = 1.0
So Gc = 1/Gp to get desired controller
Gain K calculated based on DC gain of plant
Feed-forward Controller
0.001149 z2 -0.0015 z+0.0004378
z2 +1.889 z+0.892
Feedforward
Target Speed
Feedforward
Reference
----------> DC MOTOR ------------>
&
OPTICAL ENCODER
Speed in RPM
Feedback
Set
Speed
Measure Speed
Speed Correction
Build/Reload
& Run
F2812 eZdsp
Feed-forward Controller
Take Samples
1
Feedforward
Subsystem 1
2
Reference
3
Feedback
90
Gain
Convert
Data Type
Conversion 1
C281 x
W1
PWM
C28 x PWM
Feed-forward Controller
Simulink Results
Feed-forward Controller
Actual Results
Feed-forward Controller
Actual Results
Internal Model Controller
IMC uses a plant model for disturbance
rejection
More ideal control system
Faster and more robust system
Internal Model Controller
IMC Equations
C/R = (Gc*Gp)/(1 + Gc*Gp - Gc*Gp’)
Desired C/R = 1.0
So Gc = 1/Gp’ = 1/Gp to get desired controller
Gain K calculated based on DC gain of plant
Internal Model Controller
Target Speed
Reference
IMC
Set
Speed
Feedback
----------> DC MOTOR ------------>
&
OPTICAL ENCODER
Speed Correction
Speed in RPM
Measure Speed
0.3252 z 2 +0.6504 z+0.3252
z 2 -1.305 z+0.3809
57 .29124
Compensation Gain
IMC
Build/Reload
& Run
F2812 eZdsp
Internal Model Controller
1
Reference
Take Samples
0.07355 z2 -0.09597 z+0.02802
z2 +1.111z+0.3086
Subsystem1
42 .3737
Convert
Data Type
Conversion 1
Gain
2
Feedback
C281 x
Controller
W1
IMC
1
PWM
C28 x PWM
Internal Model Controller
Simulink Results
IMC Controller
Actual Results
Hardware didn’t support algebraic loops
Unable to Run IMC from processor
Conclusion
Overall Hardware fully functional
Functional parts of GUI work correctly/ extra
features never implemented
All Controllers work in Simulation
Only proportional and feed-forward run off
hardware
Questions?
Feed-Forward Equations
C = Gp*(R*Gc + E)
E=R-C
C = Gc*Gp*R + Gp*R – C*Gp
C + C*Gp = Gc*Gp*R + Gp*R
C = R*(Gc*Gp + GP) / (1 + GP)
C/R = (Gc*Gp + Gp) / (1 + Gp)
IMC EQUATIONS
C = E*Gc*Gp
E = R – (E*Gc*Gp – E*Gc*Gp’)
E + E*Gc*Gp - E*Gc*Gp’ = R
E = R / (1 + Gc*Gp - Gc*Gp’)
C = (R*Gc*Gp) / (1 + Gc*Gp - Gc*Gp’)
C/R = (Gc*Gp) / (1 + Gc*Gp - Gc*Gp’)
Spring Semester Schedule
Week
Goals
1-7
Build and test single-loop controller, Design Gui layout
8
Build and test feed-forward controller
9-10
Implement IMC with linear model
11
Final testing, final Gui design
12-13
Final documentation
Pinout
Pinout