Project 2

AIM :-

OBJECTIVES :-

Tobulote the fuel economy numbers (emp) for ucbs and HWST cycle Compow these numbers with the bussine numbers for conventionat vehicle model from Project 1

2 For the time trace for angin, tronsmission input, transmission output and wheel speed on one plot

3 Pot engine torque, engine powe, furate and fuel consumption using sutiploes

& Phot occelerator and broke pedol gear command vehicle desired and actual speed cer dotonice using

6.Plot the engine operating points on the engine full mop

Plot motor speet torque motor input power using stiglons 3. Put pock sollage, current and Soc uning subplots

the motor operating points on the motor input power maps, with the motor max motoring and generating forque curves

9. White down appropriata triel comments on ach of these plots, describing the vehicle behavior throughout the

10. Ganerot the sluts for both cycles

• The forward modelling approdeh is also known as cause-effect, engine-to-wheel or rear-to-front method. The direction of calculation is the same as the direction components and their dynamic interaction.
• This approach is based on vehicle dynamics equations and the behaviour of each powertrain components and their dynamic interaction
• Moreover, a driver controller is required to control the vehicle to follow, a desired speed and set the start of the calculations. The controller is implemented to model the driver that will either push the accelerator or the brake pedal to match the desired speed which enables the driver behaviour. The controller is used as part of a feedback loop that will determine the energy required to drive the vehicle.

Honda Insight motor and battery are considered for this project. Data is taken from ADVISOR data base developed by NREL, USA. Data provided in the project files.

VEHICLE MODEL :-

PRE-PROCESSING (MATLAB MODEL)

A MATLAB script has been created to load all the variables needed to run and post-process the Simulink model. Drive cycle selection is also done from here. Before running the Simulink vehicle model, the script is initiated at MATLAB to load all the variables in the workspace.

%%Powertrain Parameters

FDR = 3.73; %Final Drive Ratio / Diff ratio

Diffeff 0.99; %Differential efficiency (assumed independent of operating conditions)

NunGear - 4; %number of gears in transmission

TransGear = [1:NumGear]; %Transmission Gears

TrausRatio = [3.06, 1.62, 1, 0.7]; %Corresponding Transmission ratios

TransEff = 0.90; %Transmission efficiency (assumed independent of operating conditions)

The Drive can be selected from the MATLAB script, by changing the variable Drive_Cycle_select to,

1.) UDDS

2.) HWFET

3.) FTP

4.) US06

5.) NEDC

6.) WLTP

• The Simulink model for the P1 Hybrid model is created by using 3 main sub-system blocks ie, driver block.control block and powertrain block

•The actual vehicle speed is given as feedback to the driver block and the driver black gives the controller black the required acceleration or brake output while the controller block provides control signals for engine torque,gear shifting and brake torque to the powertrain model.

Driver Model :-

• The Driver model is a basic Pl controller that generates and provides accelerator and brake pedal outputs to match the desired and actual vehicle speeds

• The pi controlier controls the error between the required drive cycle and actual vehicle speed by providing acceleration and brake pedal output to the controler

Controller Model :-

• The controller block is the brains of the vehicle, representing the electronics control units: Based on the driver inputs it generates desired engine torque, desired motor torque, desired transmission gear and desired brake torque. These inputs are fed to the Powertrain block which represents the drivetrain of the vehicle
• A stateflow machine is used to represent the supervisory control unit which decides the operating mode. While it is start/stop mode or cruising mode or regen braking mode for each modes the engine drive and the o motor drive are controlled

Supervisory controller :-

The input to the stateflow chart is acceleration and brake peddal input from the driver unit Engine actual speed Actual vehicle speed 500 status and the clutch lookup stote. And the state flow outputs to the individual controllers are the Mode, Engine On/Off request, Engine input throttie and Electric Motor input throttle

The controler consists of an engine control unit, a transmission control unit electric motor control unit and a brake control unit

All control signats are possed to transmission model which represents the drive train.

Engine Control Unit :-

idle speed controller :-

• Engine control unit compare engine speed with the maximum torque and minimum torque curves of the lookup table and give the required torque command to the engine. block. The throttle input is combined with the idle speed throttle and gains with the torque output from the lookup table to estimate the torque input required for the engine.
• New enigne On/Off featur can be implemented in this to eliminate idle losses for the engine by eliminating idle throttle for engine off conditions

Transmission Control Block :-

• The transmission control block controls the gear shifting using the study flow variable chart

• The gear shifting is controlled according to the vehicle speed and throttle input. Here it is determined whether the clutch is locked up or not, if the gear selection is greater than or equal to 3, the clutch will lock.
• The gear command is passed to the transmission block to select the desired gear ratio.

Simulink Function :-

Electric Motor Control Unit :-

The EMcontrol unit provids the EM torqe required by analysing the engine speed and EM throttle

Brake Control Unit :-

• Brake Control unit produce required brake torque according to the brake pedal input and passes brake torque in to the wheek block in the transmission model.

Powertrain Model :-

• The powertrain model includes all the components that convert the power of the engine into vehicle motion.
• This includes Engine, Battery Pack, Electric Motor, Crank Hub, Transmission, Differential,Wheels and the vehicle body dynamics subsystems.
• The control signals form the control model are transmitted via a bus to the corresponding blocks in the powetrain model.

Battery Model :-

• A Battery pack subsystem is created with Electric power input, and Battery SOC as output.
• 2 different subblocks have been created to determine the SOC and terminal voltage seperately, the SOC being used to calculate the terminal voltage

SOC Estimation Model :-

• Pack current in Ampere is converted to Amphour and divides with Max Capacity and adds with the initial SOC to determine the SOC of the battery at each instance, the SOC value is limited between 0 to 1.

Terminal Voltage Model :-

• ideal voltage and internal resistance are determined by 10 lookup tables, and battery voltage is determined using model
• The specified values are sent back to workspace using the to workspace' block and can be used for post processing

Engine Model :-

• Based on the engine speed the required torque from the controller is saturated between max torque curve and min torque curve and passes the engine torque to the crankhub.
• The 2D lookup table is used to calculate the fuel from rate based on engine speed and engine torque. The fuel flow rate is then integrated to find the fuel consumption
• The new engine also has an on/off feature to eliminate the fuel flow rate when the engine is off. Also the engine torque cannot be negative torque as minimum torque curve made saturated
• Estimated fuel flow rate, fuel consumption, engine torque and engine speed are passed to the MATLAB workspace using the to workspace block
• Engine fuelflow rate and Fuel consumption are scoped.

Electric Motor Model :-

• Based on the engine speed the required EM torque from the controller is saturated between Max EM torque curve and Max EM torque generation curve and passes the EM torque to the crank hub.
• The 2D lookup table is used to calculate the input electric power to the motor based on EM speed and EM

Crank Hub :-

• Crank hub adds up the EM torque and the Engine torque and pass it to the transmission block as the crank torque

Transmission Model :-

• The crank is connected to the automatic transmission via a torque converter. The output of the transmission is connected to the differential
• New clutch lockup feature is adding to this Hybrid version
• The gear selection from the transmission control unit is multiplied by the engine torque in this block, and the efficiency and engine dynamics of the torque converter are applied in this model.

Torque Converter :-

• Torque converter defines the pump and turbine torque by the clutch lock up status, and the combination gives us the desired transmission torque.

Differential Model :-

• The transmission output torque is multiplied by the differential ratio and differential efficiency in this block and the torque is transmitted as the axle torque.

Wheet Model :-

• The brake torque from the control model is subtracted from the Axle torque and divides from the rolling radius to determine the tractive force
• The wheel speed is calculated from the vehicle velocity and saved in the workspace.

Vehicle Dynamics :-

• The dynamics of the vehicle alog with the road load is represented in the Vehicle Dynamics' block
• Tractive force and road loads are used to calculate the vehicle velocity
• The variables are loaded on the workspace using MATLAB script.
• The acceleration, velocity and distance travelled are calculated and stored in the workspace

Post Processing

A MATLAB script is created to analyse data and to generate plots. Here we rename the variables loaded from the model, do some basic post process calculations and generate results and plots.

%% Post processing file of P1 Hybrid Vehicle Model

%% By Suriyanithi

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 torquent [NM]

Eng_Spa = 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_Spd = out.wheelSpeed*30/pi; %Wheel speed [rpm]

Desired_Spd = out.Desired_velocity*18/5; %Desired Speed [kmph]

Eng_Fuel_Rate = out.Eng_Fuel_Rate; %Engine Fuel Rate [%]

EM_Speed = out.EMSpd*18/5; %Electric Motor Speed [rpm]

EM_Power = out.EMPwr; %Electric Motor Power

EM_Torque = out.EMTrg; %Electric Motor Torque [Nm]

Term_Volt = out.term_volt; %Terminal voltage of Battery

Soc = out.Soc; %State of Charge

Pack_Current = out.Pack_Current; %Pack Current of Battery

%% 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

RESULTS :-

1.) DRIVE CYCLE

UDDS :-

HWFET :-

2. Fuel economy numbers (kmpl) for UDDS and HWFET cycle

UDDS:

For convetional vehicle model (Project 1)

Fuel economy-16.89 [kmpl]

HWFET:

For convetional vehicle model (Project 1)

Fuel economy-21.228 [kmpl]

UDDS:

For P1 Hybrid vehicle model (Project 2)

Fuel economy-18.072 [kmpl]

Fuel economy improvement is observed in P1 hybrid and it shows better economy than conventional vehicle model in UDDS cycle

HWFET:

For P1 Hybrid vehicle model (Project 2)

Fuel economy-21.997 [kmpl]

Fuel efficiency is slightly improved as the highway has less negative power when driving. But all the negative power will be regenerated with regen braking and the battery SOC will increase.

3.) The time track for engine transmission input transmission output and wheel speed

UDDS

HWFET

• Much of the fluctuating input speed is initiated by the torque converter, and the transmission input speed fluctuates according to the engine torque required to achieve the drive cycle.

• Wheel speed and transmission output speed vary according to the gear and differential ratio.

4. Engine torque, Engine power, Fuel rate and Fuel consumption using subplots

UDDS

HWFET

• The torque requirements of the drive cycle are different so the fuel flow rate varies and fuel consumption is calculated
• The HWFET drive cycle has higher power and Torque requirements and less negative torque and power

5. Accelerator and brake pedal, Gear command, Vehicle desired and actual speed, Vehicle Distance

UDDS:

Acceleration and brake pedals are used more because the drive cycle is not very smooth and the gear has to be shifted frequently

HWFET:

Brake requirements are lower, more accelerator pedals are applied on the highway drive cycle, and gear shifts often occur because the drive cycle is smoother.

Acceleration and brake pedal, the gear command of the transmission control unit, the required speed of the vehicle, the actual vehicle speed and the actual vehicle distance are plotted.

6. The Engine Operating points on the engine fuel map

UDDS:

HWFET:

• The engine operating points are plotted on the fuel map and the operating point is under the maximum torque curve

7. The motor speed, torque and motor input. power using subplots.

UDDS:

• Motor torque request is for engine start and regen braking only. Electric input power is calculated by referring the motor speed according to the EM motor torque request.

HWFET:

• EM motor torque demand is low as the vehicle moves at high speeds and less idle on highway drive

8. Pack Voltage, current and SOC using subplots.

UDDS:

• Battery SOC is responding according to the motor torque request and the regen braking

HWFET:

• Battery SOC is increases on highway drive cycles due to lower EMotor usage and regen braking battery charging

9. The motor operating points on the motor input power map, with the motor max motoring and generating torque curves

USSD:

HWFET:

• Electric motor can operate between max motoring torque curve and max generating torque curve

CONCLUSION :-

• The forward energy-based fuel consumption model of a P1 hybrid vehicle: has been successfully simulated using MATLAB and Simulink.
• Vehicle operating points based on engine and motor speed, torque, transmission speeds, pedal positions, gear, distance travelled, battery voltage, current SOC etc have been analysed and understood
• Post process calculations were performed. and the required graphs were successfully plotted.
• The improvement in the fuel efficiency numbers of the hybrid vehicle(kmpl) compared to the conventional vehicle was calculated on the Urban cycle (UDDS) and Highway cycle (HWFET)