Project 2
Aim: To analyze the various performance characteristics and operating points of UDDS and HWFET cycles
Objectives:
- Tabulate the fuel economy numbers (kmpl) for UDDS and HWFET cycle. Compare them with the previous project i.e. only with conventional vehicle.
- Plot the time trace for engine, transmission input, transmission output, and wheel speed on one plot.
- Plot engine torque, engine power, fuel rate, and fuel consumption using subplots.
- Plot accelerator and brake pedal, gear command, vehicle desired and actual speed, vehicle distance using subplots.
- Plot the engine operating points on the engine fuel map.
- Plot motor speed, torque, motor input power using subplots.
- Plot pack voltage, current, and SoC using subplots.
- Plot the motor operating points on the motor input power map, with the motor max motoring and generating torque curves.
- Write down appropriate brief comments on each of these plots, describing the vehicle behavior throughout the
- Generate the plots for both drive cycles
Procedure:
- Load the Project2 folder as the Current Folder in Matlab.
- Run the “Project2_InitFile.m” Matlab script for drive cycle 1 i.e. UDDS
Code of the 'Project2_IntiFile':
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Skill-Lync -> Hybrid Drives Development
% Project 1 - Conventional Vehicle Model
% By - Ullekh Gambhira
% 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
load Vehicle_Data/EM_Honda_Insight_10kW
load Vehicle_Data/ESS_NiMH6
ESS_init_soc = 0.8;
ESS_soc_max = 0.9;
ESS_soc_min = 0.6;
%% 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);
Eng_idle_spd = 600;
SOC_min = 0.6;
SOC_max = 0.9;- After loading the variables into the workspace, now open the Simulink model given
Vehicle Model:
Driver:
Controller:
Stateflow chart of supervisory controller:
- Open the Simulink workspace and type 'chart' and the Stateflow chart opens up
- Create an initial block
- The initial block represents the 'stop' condition, in which the engine is off, engine and motor throttle conditions are zero
- Create a second block that represents mode-1. In this, the electric motor throttle is only used to provide the required torque and power to the vehicle. The engine is off and engine throttle condition is zero
- States 1&2 are connected using the links i.e. it moves from state-1 to state-2 when acceleration is less than one or SOC is less than the minimum SOC
- State-3 represents mode-2 i.e. engine is on and the engine throttle is also having some positive value from the driver but the electric motor throttle is zero. It changes from state-2 to state-3 when engine speed is greater than or equal to the engine idle speed
- State-4 represents regenerative braking which is mode-3. In this state, the engine is on but the engine throttle is having no input from the driver, whereas the electric motor receives the negative power i.e due to the braking
- State-4 is achieved from the state-3 when SOC is less than maximum SOC or when clutch lockup is greater than zero
- State-4 moves to state-3 when SOC is greater than or equal to maximum SOC or when clutch lockup is equal to zero
- There is a chance of state-3 moving to state-1 when SOC is greater than minimum SOC and acceleration is zero
- The inputs given to the chart are acceleration, brake, engine speed, vehicle speed, SOC, and clutch lockup
- The outputs that we get from the chart are mode, engine condition (on or off), engine throttle condition, and electric motor throttle condition
Modifications are done to the engine, transmission, electric motor, brake control units
Engine control unit:
Transmission control unit:
Electric motor control unit:
Brake control unit:
Power Train:
Engine:
Electric Motor:
Crankhub:
ESS:
SOC Estimation:
Terminal Voltage:
Transmission:
Torque Converter:
Differential:
Wheels:
Vehicle Dynamics:
- Simulink model has been executed for time of 1000 sec with 'auto(ode14x)' solver
- Now, the MATLAB code is written and made run
Code:
%% 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_Speed = Eng_Spd*30/pi; % Engine speed [rpm]
Veh_Distance = Veh_Dist/1000; % Distance traveled by vehicle [km]
Veh_Speed = Veh_Spd*18/5; % Vehicle speed [kmph]
Motor_Speed = Motor_Spd*30/pi; % Motor speed [rpm]
%% 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_Distance(end)/(Eng_Fuel_Consump(end)/1000/rho_petrol); % Fuel economy [kmpl]
%% Plotting engine, transmission input, transmission output and wheel speed
figure();
grid on
hold on
plot(Time, Trans_In_Spd, 'linewidth', 1, 'Color', 'black');
hold on
plot(Time, Trans_Out_Spd, 'linewidth', 1, 'Color', 'red');
hold on
plot(Time,Eng_Speed,'linewidth',1,'Color','blue');
hold on
plot(Time,Whl_Spd,'linewidth',1,'Color','green');
xlabel('Time [s]');
ylabel('Speed [rpm]')
xlim([0, Time(end)]);
ylim([0, 6000]);
legend('Trans Input','Trans Output','Engine Speed','Wheel Speed');
%% Plotting engine torque, engine power, fuel rate and fuel consumption
figure()
subplot(4,1,1)
hold on
grid on
plot(Time, Eng_Trq, 'linewidth', 1, 'Color', 'black');
xlabel('Time [s]');
ylabel('Engine Torque [N-m]')
xlim([0, Time(end)]);
subplot(4,1,2)
hold on
grid on
plot(Time, Eng_Pwr, 'linewidth', 1, 'Color', 'blue');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Engine Power [kW]');
subplot(4,1,3)
hold on
grid on
plot(Time, Eng_Fuel_Rate, 'linewidth', 1, 'Color', 'red');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Fuel Rate');
subplot(4,1,4)
hold on
grid on
plot(Time, Eng_Fuel_Consump, 'linewidth', 1, 'Color', 'green');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Fuel Consumption');
%% Plotting vehicle characteristics time trace
figure()
subplot(4,1,1)
hold on
grid on
plot(Time, Acc_Pdl, 'linewidth', 1, 'Color', 'black');
plot(Time, Brk_Pdl, 'linewidth', 1, 'Color', 'red');
xlabel('Time [s]');
ylabel('Pedal [%]')
xlim([0, Time(end)]);
legend('Accel','Brake');
subplot(4,1,2)
hold on
grid on
plot(Time, Gear_Cmd, 'linewidth', 1, 'Color', 'black');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Gear');
subplot(4,1,3)
hold on
grid on
plot(Time, Veh_Speed, 'linewidth', 1, 'Color', 'green');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Vehicle speed (kmph)');
subplot(4,1,4)
hold on
grid on
plot(Time, Gear_Cmd, 'linewidth', 1, 'Color', 'blue');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Vehicle Distance (km)');
%% 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 motor parameters
figure()
subplot(3,1,1)
hold on
grid on
plot(Time, Motor_Speed, 'linewidth', 1, 'Color', 'red');
xlabel('Time [s]');
ylabel('Motor Speed [rpm]')
xlim([0, Time(end)]);
subplot(3,1,2)
hold on
grid on
plot(Time, Motor_Trq, 'linewidth', 1, 'Color', 'black');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Motor Torque [N-m]');
subplot(3,1,3)
hold on
grid on
plot(Time, Motor_Pwr, 'linewidth', 1, 'Color', 'green');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Motor Power [kW]');
%% Plotting Battery parameters
figure()
subplot(3,1,1)
hold on
grid on
plot(Time, term_volt, 'linewidth', 1, 'Color', 'red');
xlabel('Time [s]');
ylabel('Pack Voltage [V]')
xlim([0, Time(end)]);
subplot(3,1,2)
hold on
grid on
plot(Time, pack_current, 'linewidth', 1, 'Color', 'black');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('Pack Current [Amp]');
subplot(3,1,3)
hold on
grid on
plot(Time, SOC, 'linewidth', 1, 'Color', 'green');
xlim([0, Time(end)]);
xlabel('Time [s]');
ylabel('SOC');
%% Plotting motor operating points on motor input power map
figure('Name','Motor Operating Points');
hold on
grid on
title('Motor Operating Points','fontsize',12);
p1=plot(EM_map_spd*30/pi,EM_max_trq,'linewidth',2,'color','r');
p2=line([EM_map_spd(end)*30/pi EM_map_spd(end)*30/pi],[0 EM_max_trq(end)]);
set(p2,'linewidth',1,'linestyle','--','color','k');
p3=line([EM_map_spd(1)*30/pi EM_map_spd(1)*30/pi],[0 EM_max_trq(1)]);
set(p3,'linewidth',1,'linestyle','--','color','k');
[c,h] = contour(EM_map_spd'*30/pi,EM_map_trq,EM_inpwr_map');
clabel(c,h);
xlabel('Motor Speed [rpm]');
ylabel('Motor Torque [Nm]');
title('Motor input power map [g/s]');
p4=plot(Eng_Spd,Eng_Trq,'.','color','k');
legend([p1 p4],{'Max Curve','Operating Points'});
axis([EM_map_spd(1)*30/pi EM_map_spd(end)*30/pi 0 EM_map_trq(end)]);- Fuel economy number (kmpl) is found out from that program using formula
- Engine, transmission input, transmission output, and wheel speed are plotted on one graph with respect to the time
- Engine torque, engine power, fuel rate, and fuel consumption are plotted wrt the time using subplots
- Accelerator and brake pedal, gear command, vehicle speed, and vehicle distance are plotted wrt the time using subplots
- The engine operating points are plotted on the engine fuel map
- Motor speed, torque, motor input power are plotted wrt time using subplots
- Pack voltage, current and SoC are plotted wrt time using subplots
- The motor operating points on the motor input power map, with the motor max motoring and generating torque curves are plotted
- A similar procedure is followed by changing the drive cycle to 2 i.e. HWFET
Results:
Fuel economy numbers for project-2:
- As we see, the fuel economy is high in HWFET compared to UDDS, it is because, in urban driving, the vehicle encounters more traffic and it has to stop for fewer distances and it consumes more fuel at the starting. In HWFET, the vehicle encounters no traffic and it moves without use of too much braking, so it will have more fuel economy number
Comparison of fuel economy numbers with project-1:
- As, we see, the fuel economy numbers for project-2 are bit higher when compared to the project-1 because of implementing the electric motor. As it is P1 hybrid, it may not have much variation in the fuel economy but as we implement other architectures, it will increase by huge amount
Engine, transmission input, transmission output and wheel speed plot
UDDS drive cycle:
HWFET drive cycle:
- We can see that the graph has more fluctuations in UDDS compared to the HWFET cycle because UDDS has more starts and stops but HWFET does not have too many starts and stops
- Braking is high in UDDS when compared to HWFET due to traffic
- Peak engine power reached in UDDS is nearly 4400 RPM and that in HWFET is 3000 RPM at the start, because, in UDDS, the vehicle requires more power to start from the initial condition
Engine torque, engine power, fuel rate, and fuel consumption plot
UDDS drive cycle:
HWFET drive cycle:
- Vehicle consumed more power in the UDDS compared to HWFET cycle because it has too many starts and stops compared to HWFET. When starting from the initial condition vehicle requires more power
- Engine torque is also high in UDDS because while starting from rest, the vehicle requires more torque to overcome the static friction
- The fuel rate is high in HWFET because the vehicle will be in continuous movement, it consumes more fuel
- But, fuel economy will be high in HWFET compared to UDDS because there are many stops and starts in UDDS and more fuel is consumed when the vehicle is in an idle position
Accelerator and brake pedal, gear command, vehicle speed, vehicle distance plot
UDDS drive cycle:
HWFET drive cycle:
- For UDDS, the accelerator and the brake pedal have more fluctuations because of frequent starts and stops. But in HWFET, the brake pedal fluctuations are almost near to the zero line as there will be no frequent stops
- UDDS cycle mostly runs on 1st, 2nd gears, and uses 3rd, 4th gears very rarely as it does not achieve high speeds in that traffic. In the HWFET cycle, the vehicle mostly runs on 3rd, 4th gears as it will be moving at high speeds. It uses 1st, 2nd gears very frequently when braking is required
- Obviously, the vehicle speeds will be high in HWFET compared to UDDS. UDDS also has more fluctuations in the speed due to frequent braking
- The distance travelled in the given time will be high in HWFET than UDDS because of the traffic barrier in UDDS
Engine operating points on the engine fuel map
UDDS drive cycle:
HWFET drive cycle:
Motor speed, motor torque, motor power plot
UDDS drive cycle:
HWFET drive cycle:
- The fluctuations will be more in UDDS cycle compared to HWFET cycle because, UDDS has many starts and stops due to traffic, as the purpose of motor in P1 hybrid is initiation of crank rotation and they are more in UDDS cycle when compared to HWFET cycle
- If the purpose of the motor is to provide traction, then both the cycles would have more fluctuations
- We can obeserve that, the motor power and torque are very high in HWFET at the start and they are almost zero after few seconds but in UDDS it has continuous fluctuations. This is because of frequent braking in UDDS
Pack voltage, Pack current, SOC plot
UDDS drive cycle:
HWFET drive cycle:
- The variations will be similar to that of the motor because, battery is the energy reservoir and it gives the energy for the motor to run
- Pack voltage and current will have more fluctuationsin UDDS as compared to HWFET because of frequent start and stops throughout the drive and battery has to provide the energy everytime when the car is starting from the idle position
- SOC decreased in the UDDS cycle wrt time but it has increased in the HWFET cycle. It is because in UDDS cycle we have frequent start and stops and battery has to provide the energy everytime when the car is starting from the idle position and the SOC decreases. But in HWFET cycle, the vehicle will be moving continuously without braking frequently and the alternator is utilised to transfer some engine power to the battery through motor, so SOC increases in the HWFET cycle
Motor operating points on the input power map
UDDS drive cycle:
HWFET drive cycle:
Conclusion:
The various performance characteristics and operating points of UDDS and HWFET cycles are analyzed and the graphs are plotted for
- Engine, transmission input, transmission output and wheel speed wrt the time
- Engine torque, engine power, fuel rate and fuel consumption wrt the time
- Accelerator and brake pedal, gear command, vehicle speed, vehicle distance wrt the time
- The engine operating points on the engine fuel map
- Motor speed, torque, motor input power wrt the time
- Pack voltage, current and SoC wrt the time
- The motor operating points on the motor input power map
Also, the fuel economy numbers are tabulated and compared with the project-1