1. Integration of OCP and SIMULINK
7-8 August 2001
Gary Balas
Raktim Bhattacharya, Praveen Vijayaraghavan, Yohannes Ketema
Aerospace Engineering and Mechanics
University of Minnesota
Andrew Packard
Alpay Kaya, Zachary Jarvis-Wloszek,
Mechanical Engineering
UC Berkeley

2. F-16 Flight Control with OCP
Creating OCP components
Version 1.0
Using SIM2OCP to create F-16 flight control components
Suggestion for added OCP functionality
Basic idea
Advantages/Disadvantages
Scope for improvement

3. Creating OCP Components: (Version 1.0)

4. Creating OCP Components (Version 1.0)
Version 1.0 came with SIM2OCP tool
Converts SIMULINK skeleton models to OCP components
Easy to design OCP component skeletons
Source code generated takes care of I/O interface
Internal behavior still needs to be hand coded
Code generates Visual C++ project file
Very easy to build component data base library
Generates C++ objects for signals and their I/O
Also generates ProcessP1Main.cpp,…, ProcessPnMain.cpp
Unclear how to link ProcessPnMain.cpp with main OCP component code

5. Creating OCP Components (Version 1.0: contd)
SIMULINK process drives the simulation
System synchronization is maintained by SIMULINK
SIMULINK streams out control signal
Gateway to OCP process is a SIMULINK mex file
OCP component generates system derivative
Inter-process communication handled by OCP signal manager
Y(t) : To Integrator
OCP Component in C++
F-16 Model
I/O through OCP signal manager
MATLAB/SIMULINK
Flight Controller
U(t) : From Controller

6. Creating OCP Components (Version 1.0: contd)
OCP Component in C++
F-16 Model
I/O through OCP signal manager
Outer loop controller
LPV
longitudinal
axis
Vc , , p
HTC
Way-point
Generator y x
Integrator
Sensor
switch
Classical
lateral axis
Joystick
Inner loop controller
Flight controller implemented in MATLAB/SIMULINK

7. Creating OCP Components (Version 1.0: contd)
Currently SIMULINK synchronizes OCP components
OCP components still restricted to pure C++ code
Systems designed in SIMULINK require conversion to C++
By hand
MATLAB code generator
Server 3
Server 1

8. Using SIM2OCP to create F-16 flight control components …

9. Using SIM2OCP to create F-16 flight control components …
Create SIMULINK diagram for signal flow

10. Creating OCP components (contd.)
Start SIM2OCP …

11. Creating OCP components (contd.)
Create vector signals and define their
elements …

12. Creating OCP components (contd.)
F16_States: signal of width 16

13. Creating OCP components (contd.)
Connect components using signals created ….

14. Creating OCP components (contd.)
Decompose SIMULINK subsystems into OCP processes …

15. Creating OCP components (contd.)
Create software configuration states …

16. Creating OCP components (contd.)
Click on Finish to generate ComponentInfo.txt

17. Creating OCP components (contd.)
Generate code using
perl genocp.pl ComponentInfo.txt
Didn’t work the first time, had to call Brian.

18. Creating OCP components (contd.)
Code generator generates
Visual C++ project file / GNU makefile
Code compiles without any problem
Library ComponentDatabase_Debug.lib is created
Code generator also generates main process code
ProcessP1Main.cpp – F-16 Model
ProcessP2Main.cpp – LPV Controller
ProcessP3Main.cpp – Sensor Model
Unresolved Issues …
No information on how to compile ProcessP1Main.cpp, etc.
Brian had to create Visual C++ project files for each of the processes
Files had to be moved from one directory to another manually
Path problems related to location of libraries and header files hampers auto-code generation of VC++ project files.

19. Creating OCP components (contd.)
Unresolved Issues cont’d …
How is the controller scheduled?
How does the controller interact with other component in terms of time slices?
Is the controller responsible for all its static/dynamic memory management, state information, etc? I.e. Can the controller request 100 GB of address space independently?
Methods for testing the timing/memory footprint of the individual components?
Bottom line … a lot has been done … though more work is needed to bring OCP within reach of control engineers

20. Suggestion for added OCP functionality

21. Suggestion for added OCP functionality
Alternative approach to Component creation …

22. Suggestion for added OCP functionality
Basically the same
idea as SIMULINK,
graph representing
connections, algebraic
relationships 1 2 3 4 5 1 2 3 4 5
get_param(…,…) can extract blocks and connectivity

23. Suggestion for added OCP functionality
Component #3
Component #1
Component #2
MATLAB Engine
MATLAB Engine
MATLAB Engine
Sequence defined by
SIMULINK
OCP
Data transfer through
DDE/ActiveX/Pipes
Simulation Manager
Scheduling graph
and relationships
MATLAB Engine
MATLAB Engine
Component #4
Component #5

24. Suggestion for added OCP functionality
Library of C++ objects for systems in F-16 flight control example
Easy to create OCP components from these objects
The following C++ objects are available
F-16 Model
12 state full nonlinear
High and Low fidelity aerodynamic data
Linear System Class
Linear Parameter Varying System Class
First Order Actuator Class
Numerical Integration Class
Runge-Kutta fourth order

25. Suggestion for added OCP functionality
Alternative approach to MATLAB/OCP interaction
Design sub-systems in SIMULINK
Use MATLAB engine from C++ code to access SIMULINK
ActiveX, Dynamic Data Exchange (Windows)
Inter-process Communication based on pipes (Unix)
MATLAB is accessed as a function call (currently a MATLAB process needs to be running)
The synchronization that is currently being done by SIMULINK would then need to be done by the OCP
OCP responsibility would be similar to the Giotto scheduler (UC Berkeley). Problem is Giotto is time triggered.

26. Suggestion for added OCP functionality
Advantages:
Easy to generalize OCP components
Internal code can be MATLAB based.
Full block support of SIMULINK can be utilized.
Differs from RTW by taking advantage of full functionality of SIMULINK, perhaps at the expense of computation speed.
Sub-system can be designed in SIMULINK
More accessible to control practitioners
OCP implementation details are totally transparent
Less prone to programming errors
Disadvantage:
10 times slower than equivalent C code
Alternative :
Use RTW

27. Scope for improvement of OCP

28. OCP Version 1.0 : Scope for improvement
Easy to run examples
Less CS flavored examples
C++ language and template requires understanding of object oriented design.
Make computer science background not essential
More interaction between control engineers using OCP and Boeing OCP developers.
Better commented examples
More comments in the code to explain the inner workings