Vehicle Dynamics using matlab

Introduction

The Texas Instruments C28x family of processors has been designed to implement control applications, for example digital motor control and un-interruptible power supplies. We shall start here with a simple application. In this Laboratory, you will build a simulation model of a vehicle dynamics using Simulink, and then emulate it using the eZDSP-F2812 board.

Related Files

Powerpoint Presentation - VehicleDynamics.ppt

Simulink Model for PC Simulation - VehicleDynamics.mdl

Simulink Model for Simulation with DSKF2812 - VehicleDynamicsF2812Simulation.mdl

Simulink Model for Real-Time - VehicleDynamicsDSKF2812.mdl

Objectives

Design a Simulink model of the motion of a vehicle.

Run the model using Simulink on a PC.

Modify the model for use with the Texas Instruments C28x Digital Signal Processor.

Run the modified model on the Texas Instruments F2812 ezDSP.

Level

Beginner; This is intended as the first complete project using Matlab and Simulink.

It is suitable for students who have only limited exposure to Texas Instruments DSPs before.

Requirements

In developing this Laboratory, the following hardware and software were used:

Matlab R2006b with Embedded Target for TI C2000.

Code Composer Studio (CCS) 3.1.

Spectrum Digital ezDSP F2812 Hardware

Some external electronic components costing about $2.

Simulation

Running the Vehicle Dynamics Simulation

Open VehicleDynamics.mdl.

**Figure 1:** Engine Management Subsystem

Run the Model.

The input to the model is a ramp generator, which simulates smooth acceleration.

You will see the graphs of Horsepower and Vehicle Speed.

Changing the Vehicle Mass

Double click on the “Vehicle Dynamics” block. This models the equation of motion using Simulink Blocks.

**Figure 2:** Vehicle Dynamics

At present, the vehicle mass is 8000 kg.

We will now simulate a small compact car. Change the 1/m gain block to 1/1000 and change the b/m block to 2/1000.

Run the model again and notice the effect on maximum vehicle speed and how long it takes to reach maximum vehicle speed

You might also like to simulate a 35,000 kg lorry. Change the 1/m block to 1/35000 and b/m to 10/35000.

Changing the Engine Power Profile

Double click on the “Engine Management” block. This models the gas in – horsepower out function of the engine.

**Figure 3:** Engine Management Subsystem

Double-click on the Power Transfer Function

**Figure 4:** Engine Power Transfer Function

Change the shape of the Power Transfer Function. You may wish to change the gradient or make the plateau wider. Run the model.

Other Modifications to the Model

Go to the Website of an automobile manufacture, and obtain the actual engine power transfer function for a real car. Run this in the model.

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.

**Figure 5:** Modified Model for F2812

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.

**Figure 6:** A New MatLab Model

The following screen will appear.

**Figure 7:** An Empty MatLab Model

Saving the New Model

Save the model as “vehicle_dynamics.mdl”.

**Figure 8:** Saving the new model

Opening the Library Browser

Select View-> Library Browser

**Figure 9:** Selecting the 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.

**Figure 10:** The Simulink Library Browser

Subsystems Added

Rename the Subsystems to “Engine Management” and “Vehicle Dynamics”.

**Figure 11:** Subsystems Added

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.

**Figure 12:** Adding a Ramp Generator

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.

**Figure 13:** Adding a Scope

Joining and Renaming the Blocks

Join the blocks as shown in the figure below. Change the names and add a title.

**Figure 14:** First Blocks Added

Setting the Solver

The ode45 solver is not suitable for use with DSP. “Fixed Point Discrete” is required.

**Figure 15:** Configuring the Solver

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.

**Figure 16:** The Engine Management Subsystem

Adding a Lookup Table

From the Simulink Lookup Tables, drag-and-drop the “Lookup Table” block onto the model.

**Figure 17:** Adding a Lookup Table

Double click on the “Lookup Table” block.

**Figure 18:** Lookup Table Block Parameters

The values for the table can also be inserted as a table. Click on the “Edit” box.

**Figure 19:** Lookup Table Values

Click on "Plot" as shown above, and you will see:

**Figure 20:** Adjusting the Lookup Table

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.

**Figure 21:** Vehicle Dynamics Subsystem

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.