Project 1

Aim:

To develop a forward energy-based fuel consumption model of a conventional vehicle using Matlab and Simulink to analyze data and generate plots.

Objective:

1) Load the Project1 folder as the Current Folder in Matlab.
2) Run the “Project1_InitFile.m” Matlab script.
3) The provided vehicle Simulink model “Project1_VehicleModel.slx” is incomplete. The engine and vehicle dynamics block contents have been deleted. Build the Simulink blocks by referring to the course lecture and example block images provided. You can run the model and analyze the results using a ‘Scope’ for debugging.
4) Add additional ‘To Workspace’ blocks for transferring the desired Simulink vehicle data into the Matlab workspace.
5) Modify the “Project1_ProcessingFile.m” as per the desired plots and required calculations.
6) Write a project report that contains the following:

a. Tabulate the fuel economy numbers (kmpl) for UDDS and HWFET cycle. This forms the baseline numbers for comparison with the future hybrid version.
b. Plot the time trace for engine, transmission input, transmission output and wheel speed on one plot.
c. Plot engine torque, engine power, fuel rate and fuel consumption using subplots.
d. Plot accelerator and brake pedal, gear command, vehicle desired and actual speed, vehicle distance using subplots.
e. Plot the engine operating points on the engine fuel map.f. Write down appropriate brief comments on each of these plots, describing the vehicle behaviour throughout the drive cycle.
g. Generate the plots for both drive cycles

Conventional Vehicle:

Conventional vehicles use an internal combustion engine fuel by gasoline or diesel to power the wheels, in this, the heat engine uses the principle of heat release through the combustion of a fuel with an oxidizer in a combustion chamber to create expanding gases which push against a piston creating forcce and torque output.

In this vehicle, the engine converts chemical energy stored in the fuel into heat which is used to produce useful work. Typically use fossil fuels like petroleum (petrol and diesel).

The most popular type of engine used in this system is 4 strokes reciprocating engine. The engine in-cylinder process can be represented by ideal thermodynamic cycles such as the Otto cycle and Diesel cycle. Otto cycle is an ideal cycle that describes the cycle process for spark ignited SI engine, and the Diesel cycle is the ideal cycle that describes the cycle process for a compression ignited Cl engine

Energy and performance of a vehicle

In this system, the power demand on the wheel needs to be instantly supplied by the powertrain. In another word the power coming from the powertrain dictates the power demands on the wheels (as per performance viz, acceleration, speed etc is determined by it

Conventional powertrain efficiency:

The engine generates power by converting chemical energy stored into mechanical energy through the process of combustion. This process of energy conversion also has efficiency and the energy input is in the form of fuel consumption.

The efficiency of an IC engine (Internal Combustion Engine) is defined as the ratio of work done to the energy supplied to an engine. The different types of efficiencies are:

(a) Mechanical efficiency. It is the ratio of brake power (B.P.) to the indicated power (I.P.).

(b) Overall efficiency. It is the ratio of the work obtained at the crankshaft in a given time to the energy supplied by the fuel during the same time.

(c) Indicated thermal efficiency. It is the ratio of the heat equivalent to one kW hour to the heat in the fuel per I.P. hour.

(d) Brake thermal efficiency. It is the ratio of the heat equivalent to one kW hour to the heat in the fuel per B.P. hour.

(e) Volumetric efficiency. It is the ratio of the actual volume of charge admitted during the suction stroke at N.T.P to the swept volume of the piston.

MATLAB Script:

A Matlab code “Project1_InitFile.m” was created to load the variable to the workspace. In this project, a typical midsize car with a 1.9L engine and a 4-speed automatic transmission is considered. Data is taken from the ADVISOR database developed by NREL, USA.

The transmission shift map and controller is taken from Matlab/Simulink example database. The model developed has the capability to simulate the vehicle on different drive cycles like UDDS, HWFET, FTP, NEDC, etc.

Used to load all the variables required for running the Simulink model and for post-processing. The drive cycle selection is also done here. Before running the Simulink vehicle model, run this initialization script.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Skill-Lync -> Hybrid Drives Development
% Project 1 - Conventional Vehicle Model


% Description:

%% Initialization File
% Initialization file for loading the variables for the Conventional vehicle simulation model

%% Vehicle Parameters
M = 1500;       % Vehicle weight [kg]
Cr = 0.015;     % Rolling resistance coefficient
Rw = 0.35;      % Rolling radius [m]
Cd = 0.33;      % Drag coefficient
Af = 2;         % Frontal area [m2]
rhoa = 1.225;   % Air density [kg/m3]
Vwind = 0;      % Wind velocity [kmph]
g = 9.81;       % Gravitational acceleration [m/s2]
theta = 0;      % Slope [deg]
myu_road_tire = 1; % Coefficient of friction between tire - road interface

%% Powertrain Parameters 
FDR = 3.73;                         % Final Drive Ratio / Diff Ratio
DiffEff = 0.99;                     % Differential efficiency (assumed independent of operating conditions)

NumGear = 4;                        % Number of gears in transmission
TransGear = [1:NumGear];            % Transmission Gears
TransRatio = [3.06, 1.62, 1, 0.7];  % Corresponding Transmission ratios
TransEff = 0.90;                    % Transmission efficiency (assumed independent of operating conditions)

TC_SR = [0, .5, .6, .7, .8, .87, .92, .94, .96, .97, 1];   % Torque Converter Speed Ratio (Matlab default) -> TurbSpd/PumpSpd  
TC_TR = [2.232, 1.5462, 1.4058, 1.2746, 1.1528, 1.0732, 1.0192, 1, 1, 1, 1];   % Torque Converter Torque Ratio (Matlab default) -> TurbTrq/PumpTrq
TC_Cf = 1e-4 * [.72558, .66322, .63463, .59042, .51331, .4144, .29287, .22444, .12186, .04386, 0]; % Torque Converter Capacity Factor (Matlab default) -> PumpTrq/PumpSpd^2 [Nm/rpm^2]

load Vehicle_Data/Engine_data_1_9L_Saturn_95kW
load Vehicle_Data/Trans_Shift_map

%% Driver Parameters
Kp = 10;                    % P gain for driver PI model
Ki = 1;                     % I gain for driver PI model
Drive_Cycle_Select = 3;     % Drive cycle selection

% Drive cycle values in m/s

if Drive_Cycle_Select == 1
    load DriveCycles/UDDS;
    
elseif Drive_Cycle_Select == 2
    load DriveCycles/HWFET;
    
elseif Drive_Cycle_Select == 3
    load DriveCycles/FTP;
    
elseif Drive_Cycle_Select == 4
    load DriveCycles/US06;
    
elseif Drive_Cycle_Select == 5
    load DriveCycles/NEDC;
    
elseif Drive_Cycle_Select == 6
    load DriveCycles/WLTP;
 
end

time_end = cyc_time(end);
vel_end = cyc_vel(end);

Simulink Model:

• It is modeled using a ‘Driver’ block, which is a basic PI controller that generates accelerator and brake pedal outputs to match the desired and actual vehicle speeds.
• This accelerator and brake pedaldata is generated using the drive cycle data in which is fed through look up table.

Driver Block:

Controller Block:

The 'Controller' block is the brains of the vehicle, representing the electronic controls units. It is based on the driver inputs, it generates desired engine torque, desired transmission gear and desired brake torque. These inputs are fed to the 'Powertrain' block which represents the drivetrain of the vehicle.

Power Train:

The data inputs are fed to the ‘Powertrain’ block which represents the drivetrain of the vehicle.

It consists of an ‘Engine’ connected to the ‘Automatic Transmission’ through a ‘Torque Converter’.

The output of the transmission is connected to the ’Differential’, which powers the ‘Wheels’, which provide the tractive force for vehicle acceleration.

The longitudinal dynamics of the vehicle along with the road load are represented in the ‘Vehicle Dynamics’ block. The solver selected is ode3 with a fixed step size of 0.01 sec.

Engine Block:

Transmission Block:

Torque Converter:

Differential Block:

Wheel Block:

Vehicle Dynamic Block:

A vehicle dynamic block has been created by this equation.

Project1_InitFile:

A Matlab code “Project1_InitFile.m” was created to load the variable to the workspace. In this project, a typical midsize car with a 1.9L engine and a 4-speed automatic transmission is considered. Data is taken from the ADVISOR database developed by NREL, USA. The transmission shift map and controller is taken from Matlab/Simulink example database.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Skill-Lync -> Hybrid Drives Development
% Project 1 - Conventional Vehicle Model
% By - Ullekh Gambhira 

% Description:
% The following file is to used with the Initialization file and Simulink
% results for post-processing of the data.
% The file is incomplete, has some examples of how the data is imported
% into a readable format, data analysis and plotting examples.
% Based on the project task, use commands in a similar format as given
% below, to analyse the data and generate required plots.
% You can change variable names if desired

%% Post-Processing File
%  File for post-processing the Conventional vehicle simulation model data

%% Renaming variables
Time = out.tout;
Acc_Pdl = out.Acc_Pdl;          % Accelerator pedal [%]
Brk_Pdl = out.Brk_Pdl;          % Brake pedal [%]
Gear_Cmd = out.Gear_Cmd;        % Transmission gear
Trans_In_Spd = out.Trans_In_Spd*30/pi;  % Transmission input speed [rpm]
Trans_Out_Spd = out.Trans_Out_Spd*30/pi;% Transmission output speed [rpm]
Eng_Trq = out.Eng_Trq;          % Engine brake torque [Nm]
Eng_Spd = out.Eng_Spd*30/pi;    % Engine speed [rpm]
Eng_Fuel_Consump = out.Eng_Fuel_Consumption;    % Engine fuel consumption [g]
Veh_Dist = out.Veh_Dist/1000;   % Distance traveled by vehicle [km]
Veh_Spd = out.Veh_Spd*18/5;     % Vehicle speed [kmph]


%% Data Analysis
Eng_Pwr = Eng_Spd.*pi/30.*Eng_Trq/1000;   % Engine brake power [kW]
rho_petrol = 0.7197;                    % Density of petrol [kg/L]
kmpl = Veh_Dist(end)/(Eng_Fuel_Consump(end)/1000/rho_petrol);    % Fuel economy [kmpl] 


%% Plotting vehicle characteristics time trace
figure(1)

hold on
grid on
plot(Time, Acc_Pdl, 'linewidth', 1, 'Color', 'black');
plot(Time, Brk_Pdl, 'linewidth', 1, 'Color', 'red');
ylabel('Pedal [%]')
xlim([0, Time(end)]);
legend('Accel','Brake');
figure(2)

hold on
grid on
plot(Time, Trans_In_Spd, 'linewidth', 1, 'Color', 'black');
plot(Time, Trans_Out_Spd, 'linewidth', 1, 'Color', 'red');
ylabel('Speed [rpm]')
xlim([0, Time(end)]);
ylim([0, 6000]);
legend('Trans Input','Trans Output');

figure(3)
hold on
grid on
plot(Time, Gear_Cmd, 'linewidth', 1, 'Color', 'black');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Gear');

%% Plotting engine operating points on engine fuel map
figure('Name','Engine Operating Points');
hold on
grid on
title('Engine Operating Points','fontsize',12);
p1=plot(Eng_map_spd*30/pi,Eng_max_trq,'linewidth',2,'color','r');
p2=line([Eng_map_spd(end)*30/pi Eng_map_spd(end)*30/pi],[0 Eng_max_trq(end)]);
set(p2,'linewidth',1,'linestyle','--','color','k');
p3=line([Eng_map_spd(1)*30/pi Eng_map_spd(1)*30/pi],[0 Eng_max_trq(1)]);
set(p3,'linewidth',1,'linestyle','--','color','k');
[c,h] = contour(Eng_map_spd'*30/pi,Eng_map_trq,Eng_fuel_map');
clabel(c,h);
xlabel('Engine Speed [rpm]');
ylabel('Engine Torque [Nm]');
title('Engine Fuel Consumption Map [g/s]');
% p4 = plot(Eng_Spd,Eng_Trq,'.','color','k');
% legend([p1 p4],{'Max Curve','Operating Points'});
axis([Eng_map_spd(1)*30/pi Eng_map_spd(end)*30/pi 0 Eng_map_trq(end)]);

Plot Graph:

UDDS Cycle:

Fuel Rate Vs Fuel Consumption.

From this simulation, we came to know that in the time gap between 200 to 400 sec the engine consumes more fuel which reflects that more power is produced due to an increase in acceleration of the pedal by the driver

Vehicle characteristics:

As per the driver speed requirement, the output speed has been obtained. In this graph also we see the maximum speed achieved between 200 to 400 cycles. In this time the fuel consumption, Power output, Torque, Engine speed, and Gear shift are achieved at a higher speed in the simulation.

Vehicle characteristics time trace accelerator and brake pedal, gear command, vehicle desired and actual speed:

In the plot, we absorbed that after 200 mins the acceleration reaches maximum pedal acceleration. brake also zero.

Due to the Gear shift, the Wheel speed is more in the cycle between 200 to 400 mins. wheel speed seems more while compared with the Engine during the time gap.

Due to gear shift in the cycle state of 200 to 350 mins. which results in the Wheel speed is higher than the Engine speed because of the gear ratio.

Engine operating points on engine fuel map:

Engine Torque is reached its peak point at the engine speed of 5000rpm.

From this simulation, we came to know that in the time gap between 300 to 350 sec the engine consumes more fuel which reflects that more power is produced due to an increase in acceleration of the pedal by the driver.

Vehicle characteristics:

As per the driver speed requirement, the output speed has been obtained. In this graph also we see the maximum speed achieved between 300 to 750 cycles. In this time the fuel consumption, Power output, Torque, Engine speed, and Gear shift are achieved at a higher speed in the simulation.

Vehicle characteristics time trace accelerator and brake pedal, gear command, vehicle desired and actual speed:

In the plot, we absorbed that after 300 mins the acceleration reaches maximum pedal acceleration. brake also zero till 750min. After that, the brake power is more than the engine power so that the Vehicle remains in an idle state.

Due to the Gear shift, the Wheel speed is more in the cycle between 300 to 780 mins. wheel speed seems more while compared with the Engine during the time gap.

Due to the gear shift in the cycle state of 350 to 700 mins but there is fluctuation in speed so the gear changes between 3 to 4 & 4 to 3. which results in the Wheel speed being higher than the Engine speed because of the gear ratio. When the end the engine acceleration is zero so the speed is reduced and the gear shifts to 1 in the end.

Engine operating points on engine fuel map:

Engine Torque is reached its peak point at the engine speed of 5000rpm. later it starts decrease.

Conclusion:

The Forward energy-based fuel consumption model of a conventional vehicle was developed using MATLAB and SIMULINK and the plots were obtained for UDDS and HWFET cycles.