Project 1
Aim:
Development of a forward energy-based fuel consumption model of a conventional vehicle
Objectives:
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.
Tasks:
The task of this project is to compute the fuel economy numbers for the given vehicle (kmpl) on the urban cycle (UDDS) and highway cycle (HWFET). Also, to analyse and understand the vehicle operating points in terms of engine speed, torque, transmission speeds, pedal positions, gear, distance travelled, etc. The following observations need to be made:
A. Tabulate the fuel economy numbers (kmpl) for UDDS and HWFET cycle. This forms the baseline numbers for comparing 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.
Simulink model:
The given model is a pre-built model with the Engine and Vehicle dynamics blocks left empty to work upon. The model developed has the capability to simulate the vehicle on different drive cycles like UDDS, HWFET, FTP, NEDC, etc.
In the model, “Project1_InitFile.m” is the Matlab script used to load all the variables required for running the Simulink model and for post-processing. The drive cycle selection is also done here. “Project1_VehicleModel.slx” is the Simulink model of the vehicle. It is modelled 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. 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. These 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. After running this Simulink model, data from the model will be loaded in the Matlab workspace.
“Project1_ProcessingFile.m” is the Matlab script used to analyse this data and to generate plots. This script needs to be executed after the Simulink model data has been loaded into the workspace. As the Engine and Vehicle dynamics subsystems are blank, we need to model them. Accordingly, they have been modelled as:
Project1_VehicleModel/Controller
project1_vehicleModel/Driver
project1_vehicleModel/powertrain
Project1_VehicleModel/Powertrain/Engine
Project1_VehicleModel/Powertrain/Transmission
Project1_VehicleModel/Powertrain/Differential
Project1_VehicleModel/Powertrain/Wheels
Project1_VehicleModel/Powertrain/Vehicle Dynamics
so we have to work upon 2 drive cycles UDDS And HWFET The initialisation scripts has provisions in it to switch between various cycles
1.) Frist lets have a look at outputs for UDDS Cycles
The Initisation Scripts:
% Project 1 - Conventional Vehicle Model
% By - Anbarasan N
% 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 = 1; % 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 Post Processing Scripts
% 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]
Eng_Fuel_Rate=out.Fuel_rate; % Fuel rate
Veh_Dist = out.Veh_Dist/1000; % Distance traveled by vehicle [km]
Veh_Spd = out.Veh_Spd*18/5; % Vehicle speed
%% 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('Name','Time Trace')
plot(Time,Eng_Spd,'b-',Time,Trans_In_Spd,'g-',Time,Trans_Out_Spd,'r-',Time,Veh_Spd,'m-')
legend('Engine Speed','Transmission Input Speed', 'Transmission Output Speed','Wheel Speed');
title('Time trace');xlabel('Time(s)');ylabel('Speed(rpm)')
%% 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)]);
%% Plotting Engine performance parameters
figure('Name','Engine Performance Parameters')
subplot(411);plot(Eng_Trq,'b-');xlabel('Time');ylabel('Engine Torque')
subplot(412);plot(Eng_Pwr,'g-');xlabel('Time');ylabel('Engine Power')
subplot(413);plot(Eng_Fuel_Rate,'k-');xlabel('Time');ylabel('Engine Fuel consumption rate')
subplot(414);plot(Eng_Fuel_Consump,'m-');xlabel('Time');ylabel('Engine Fuel Consumption')
%% Plotting Vehicle Parameters
figure('Name','Vehicle parameters')
subplot(321);plot(Time, Acc_Pdl, 'b-');title('Acceleration Pedal');
xlabel('Time(s)');ylabel('Pedal[%]')
subplot(322);plot(Time, Brk_Pdl, 'g-');title('Brake Pedal');
xlabel('Time(s)');ylabel('Pedal[%]')
subplot(323);plot(Time, Gear_Cmd, 'r-');title('Gear command');
xlabel('Time(s)');ylabel('Gear engaged')
subplot(324);plot(cyc_time,cyc_vel*1.609,'b-');title('Desired Vehicle Speed');
xlabel('Time(s)');ylabel('Speed(kmph)')
subplot(326);plot(Time,Veh_Spd,'m-');title('Actual Vehicle Speed');
xlabel('Time(s)');ylabel('Speed(kmph)')
subplot(325);plot(Time,Veh_Dist,'c-');title('Distance travelled by Vehicle')
xlabel('Time(s)');ylabel('Distance(km)')Outputs as per tasks
A.The fuel economy for UDDS as obtained at the end of simulation is 20.29kmpl.
B.The time trace for the speeds are as
Its quite evident that the engine that the engine rotates at higher rpm the same is transferred to the transmssion inputs with same losses and hence the output speed drop greatly similary there are losses while going from transmission output to the wheels as well. hence the speed of the wheel is way lower than the speed of the engine revolution
C.The engine performance parameters are plotted as
As the UDDS represents city driving conditions, there are frequent starts and stops in the cycle. Also, the torque and power requirements are high as the vehicle needs to be set into motion from a standstill, frequently, and that requires a high torque. The vehicle consumes about 425 grams of fuel during the 12 km drive.
D.The various vehicle parameters are plotted as:
As this drive cycle is representative of an city driving condition, there is frequent braking here. Also, the vehicle operates mostly in the lower gears only. The similarity of the desired speed plot and the actual speed plot indicate that the model is a feedback control system.
E.The engine operating points are plotted as:
The operating points for the given cycle are spread over a greater area of the map. The fuel consumption in such a case is more, indicating reduced efficiency of the engine.
2.) Lets now look at the outputs for the HWFET Drive cycle
There this only change in the initialisation script of changing the drive cycle to 2
%% 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 == 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);OUTPUT:
A.The fuel economy for HWFET as obtained at the end of simulation is
is 29.11 kmpl. This goes on to verify that when operated at certain speeds constantly, over a journey, the engine tends to perform better. Thats the economy region mentioned on vehicles urging operators to hover around those values for better performance.
B. The time trace for this cycle is as:
Here its evident that the wheel speed significantly drops to lower levels from the transmission output speed verifying the fact that at higher speeds the vehicle faces greater resistance (due to aerodynamic drag being proportional to square of velocity) and hence higher are the losses.
C. The engine performance parameters are plotted as:
As the cycle is for highway driving conditions, after starting initially, the engine operates in constant torque region and after reaching the critical velocity operates in the constant power region. As the vehicle doesn't go through much start and stop cycles the torque and power requirements are lower than the UDDS cycles as the ineria of the vehicles comes into play. The vehicle here consumes about 408 grams of fuel for a drive of about 16 kms. This indicates that the cycle is comparatively efficient than the UDDS cycle.
D. The various vehicle parameters are plotted as
As is evident, the vehicle undergoes very less braking during its journey. Speed can mostly be controlled by the force on the pedal and as the vehicle doesn't face major roadblocks there isn't a significant requirement for braking. Here, the vehicle operates more in the higher gears to meet the higher speed requirements of the vehicle. Also, the vehicle travels greater distance in a shorter duration of time signifying higher average speed of the journey.
E. The engine operating points are plotted as:
The operating points for the given cycle are spread over a smaller area of the map. The fuel consumption in such a case is less, indicating higher efficiency of the engine.