Energy-based fuel consumption model of a conventional vehicle

OBJECTIVE:

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

THEORY:

• In a conventional vehicle the power is generated by a an Internal Combution Engine that converts the chemical energy in the fuel to mechanical energy.
• This mechanical energy reach the wheels through a drive train which contains the transmission, differential components.
• The efficiency of an IC engine (Internal Combustion Engine) is defined as the ratio of workdone 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.

MODEL:

INITIAL MATLAB CODE:

• 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 ADVISOR data base developed by NREL, USA. 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.

The CODE:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% 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 = 2;     % 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);

THE 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. Based on the driver inputs, it generates desired engine torque, desired transmission gear and desired brake torque.

• 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’, that provides the tractive force for vehicle acceleration. The longitudinal dynamics of the vehicle along with the road load is represented in the ‘Vehicle Dynamics’ block. The solver selected is ode3 with a fixed step size of 0.01 sec.

POWERTRAIN:

THE ENGINE BLOCK:

THE TRANSMISSION BLOCK:

THE DIFFERENTIAL BLOCK:

THE WHEELS BLOCK:

THE VEHICLE DYNAMICS BLOCK:

• The equation used here is:

POST PROCESSING:

• The Data from the SIMULINK model was transferred to matlab workspace using 'To Workspace' block
• A post processing MATLAB code was used to gererate the necessary plots.

THE CODE:

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

% 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]
Wheel_speeed = out.Wheel_speed.Data; % Wheel speed [kmph]
Eng_Fuel_rate = out.Eng_Fuel_Rate; % Engine Fuel Rate [%]
Veh_Desired_Sped = out.Veh_desired_spd; % Desired 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 Fuel Consumption vs Fuel Rate
figure(1)
hold on
grid on
plot(Time, Eng_Fuel_Consump.Data, 'linewidth', 1, 'Color', 'black');
plot(Time, Eng_Fuel_rate.Data, 'linewidth', 1, 'Color', 'red');

xlabel('Fuel Consumption ')
ylabel('Fuel Rate ')
xlim([0, Time(end)]);
legend('Fuel Consumption','Fuel Rate');


%% Plotting vehicle characteristics time trace Engine,Transmission Input, Transmission Output and Wheel Speed
figure(2)
hold on
grid on
plot(Time,Eng_Spd.Data,'LineWidth',1,'Color','g');
plot(Time,Trans_In_Spd,'LineWidth',1,'Color','black');
plot(Time,Trans_Out_Spd,'LineWidth',1,'Color','red');
plot(Time,Wheel_speeed,'LineWidth',1,'Color','blue');

xlabel('Time [s]')
ylabel('Speed [rpm]')
xlim([0, Time(end)]);
ylim([0, 6000]);
legend('Transmission Input','Transmission Output','Wheel Speed','Engine Speed');

%% Plotting vehicle characteristics time trace engine torque, engine power, fuel rate and fuel consumption

figure(3)
subplot(2,2,1)
plot(Time,Eng_Trq.Data,'LineWidth',1,'Color','g')
xlabel('Time [s]')
ylabel('Torque [Nm]')
legend('Torque')

subplot(2,2,2)
plot(Time,Eng_Pwr.Data,'LineWidth',1,'Color','black')
xlabel('Time [s]')
ylabel('Power [kW]')
legend('Engine Power')

subplot(2,2,3)
plot(Time,Eng_Fuel_rate.Data,'LineWidth',1,'Color','red')
xlabel('Time [s]')
ylabel('Fuel Rate [%]')
legend('Fuel Rate')

subplot(2,2,4)
plot(Time,Eng_Fuel_Consump.Data,'LineWidth',1,'Color','blue')
xlabel('Time [s]')
ylabel('Fuel Consumption [kmpl]')
legend('Fuel Consumption')


%% Plotting vehicle characteristics time trace accelerator and brake pedal, gear command, vehicle desired and actual speed.
figure(4)
subplot(3,1,1)
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');
subplot(3,1,2)
hold on
grid on
plot(Time,Veh_Desired_Sped.Data, 'linewidth', 1, 'Color', 'black');
plot(Time,Veh_Spd.Data, 'linewidth', 1, 'Color', 'red');
ylabel('Speed [rpm]')
xlim([0, Time(end)]);
legend('Vehicle Desired Speed','Vehicle Actual Speed');
subplot(3,1,3)
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 p3],{'Max Curve','Operating Points'});
axis([Eng_map_spd(1)*30/pi Eng_map_spd(end)*30/pi 0 Eng_map_trq(end)]);

THE PLOTS:

UDDS CYCLE:

(1) Fuel Consumption vs Fuel Rate:

(2) Vehicle characteristics time trace Engine,Transmission Input, Transmission Output and Wheel Speed:

(3) Vehicle characteristics time trace engine torque, engine power, fuel rate and fuel consumption:

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

(5) Engine operating points on engine fuel map:

HWFET CYCLE:

(1) Fuel Consumption vs Fuel Rate:

(2) Vehicle characteristics time trace Engine,Transmission Input, Transmission Output and Wheel Speed:

(3) Vehicle characteristics time trace engine torque, engine power, fuel rate and fuel consumption:

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

(5) Engine operating points on engine fuel map:

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.