Replace the ramp generator input with a step function. This simulates someone stamping on the gas!
Reference simulation for f2812
Running the vehicle dynamics simulation
Open VehicleDynamicsF2812Simulation.mdl .
Run this model. This is the behavior that should be seen when the real-time model is run on the ezDSP for F2812.
Creating your own models
Creating a new matlab model
Start Matlab 7.3.0 R2006b
In the top left hand corner of the Matlab screen, select: File ->New ->Model.
The following screen will appear.
Saving the new model
Save the model as “vehicle_dynamics.mdl”.
Opening the library browser
Select View->Library Browser
Selecting the subsystems
A list of available blocks will appear. Select “Commonly used blocks”. Highlight “Subsystems”. Drag-and-drop two copies of this block into the model.
Subsystems added
Rename the Subsystems to “Engine Management” and “Vehicle Dynamics”.
Drag-and-drop a “saturation” block onto the model.
Adding a ramp generator
From the Simulink Library Browser, select “Sources”. Drag-and-drop the “Ramp” block onto the model.
Adding scope blocks
From the Simulink Library Browser, select “Sinks”.
Drag-and-drop the “Scope” block onto the model twice.
Drag-and-drop the “Display” block onto the model twice.
Joining and renaming the blocks
Join the blocks as shown in the figure below. Change the names and add a title.
Setting the solver
The ode45 solver is not suitable for use with DSP. “Fixed Point Discrete” is required.
The engine management subsystem
Overview of the engine management subsystem
The first stage of the Engine Management Subsystem is a “Gain” block, which converts the Gas Pedal input (0-100%) to 0-4000 rpm.
The second stage is a lookup table. This converts from rpm to hp.
Adding a lookup table
From the Simulink Lookup Tables, drag-and-drop the “Lookup Table” block onto the model.
Double click on the “Lookup Table” block.
The values for the table can also be inserted as a table. Click on the “Edit” box.
Click on "Plot" as shown above, and you will see:
The vehicle dynamics subsystem
Overview of vehicle dynamics subsystem
The C28x operates in discrete-time; therefore the continuous integrator must be replaced by a “Discrete Time Integrator” for DSP model implementation.
Select the “Main” tab. Change the “Constant value” to 0. Click on “OK”.
Running the simulation
The ramp generator gently changes the Gas Pedal from 0% to 100%. This simulates smooth acceleration. The Horsepower and Vehicle Speed are shown on the graphs.
Modifications for ezdsp f2812
In order to run the model on the ezDSP F2812, some additional blocks need to be added to the project:
- An Analog-to-Digital Converter (ADC) to allow a potentiometer input.
- A block to scale the ADC input to the range 0 to 100%.
- A Digital-to-Analog Converter (DAC) to convert the Vehicle Speed to an analog output in the range 0 to 3.3V
Connecting the f2812 ezdsp
For Matlab and Simulink to run correctly, you need to run the F2812 ezDSP.
Connect the F2812 hardware to the parallel port of the computer and turn on the supply to the board.
When the board is powered, the two green LED lights on the board will come on during self-test.
Start Code Composer Studio for F2812 ezDSP and use Debug ->Connect
Opening the library browser
Select View->Library Browser
The simulink library browser
A list of available blocks will appear. We are particularly interested in the “Embedded Target for TI C2000 DSP”. Click on this selection.
In the following sections we will select the building blocks for the DSP model shown in Figure 30.
Selecting target preferences
From the C2000 Target Preferences, select “F2812 ezDSP”. Drag-and-drop the icon onto the new model.
Figure 26 – Selecting Target Preferences
When the following screen appears, it is important to select “Yes”.
Scaling the adc readings
To scale the ADC reading to the Gas Pedal 0 to 100% we will multiply the ADC input by 800 then divide by 32768.
Figure 28 – Scaling the ADC
Scaling the dac output
To scale the kph to the DAC output, we will multiply the kph input by 312.5. The “Saturation” block limits the output to 200 kph.
The finished model
To scale the kph to the DAC output, we will multiply the kph input by 312.5.
Building the model
Select Tools ->Real-Time Workshop ->Build Model.
You may find the final model here .
Comparing performance
The real-time model running on the ezDSP F2812 should now be behaving in the same way as the Simulation.
References
- Spectrum Digital Incorporated, "eZdspTM F2812 Technical Reference" Rev. F, September 2003. ( (External Link) )