Challenge

Project 2

HHariram Senthilkumaran1 Sept 2023

FORWARD MODEL APPROACH

The engine-to-wheel, rear-to-front, and cause-and-effect methods are other names for the forward modelling methodology. Calculation flows from engine to wheel in the same direction as positive power flow.

• This method is based on equations for vehicle dynamics, the behaviour of individual powertrain parts, and their dynamic interplay.

• In addition, a driver controller is necessary to establish the calculation start time and operate the vehicle to follow a chosen speed. The controller is set up to simulate how the driver will operate the brakes or the accelerator to match the intended speed, allowing for the study of driver behaviour. The controller is utilized as a component of a feedback loop to calculate the amount of energy necessary to power the vehicle.

This model includes a driver model that provides input commands acceleration and brake torque depending on the drive cycle and the actual speed of the vehicle.
A control model that controls the engine torque to the desired range and changes the gear command and control brake torque according to the driver input.
The transmission model that gives the actual speed of the vehicle as feedback to the driver model. The model includes the engine, transmission, differential, wheel and vehicle dynamics models separately.

VEHICLE MODEL

Pre-Processing

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 initialised at MATLAB to load all the variables in the workspace.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Skill-Lync -> Hybrid Drives Development

% Project 1 - Conventional Vehicle Model

% By - Ullekh Gambhira

�scription:

%% 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 = 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);

SIMULINK MODEL:

The driver model, control model, and powertrain block are the three basic sub-blocks used to form the convection model in Simulink.

The controller block sends control signals for engine torque, gear shifting, and brake torque to the Powertrain model while the driver block receives feedback on the actual vehicle speed and supplies the controller block with the necessary acceleration or braking output.

DRIVER MODEL

A fundamental PI controller called Driver Model produces outputs from the accelerator and brake pedals that are matched to the desired and actual vehicle speeds.

By giving the controller output for the accelerator and brake pedals, the PI controller manages the discrepancy between the needed driving cycle and the actual vehicle speed.

CONTROLLER MODEL

The 'Controller' block, which stands in for the electronic control systems, is the brain of the car. It produces the required engine torque, desired gearbox gear, and desired brake torque based on the driver's inputs. The 'Powertrain' block, which symbolizes the vehicle's drivetrain, receives these inputs. An engine control unit, a transmission control unit, and a brake control unit make up the controller.

CHART BLOCK

This Block contains the basic control of the logical operation such as STOP, START,DRIVE & REGEN BRAKING MODES. These modes are selected based on the conditions based on acceleration pedal inputs, Battery SOC, Brake pedal inputs and clutch position.

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.
Throttle input, idle throttle and their sum can be scoped from this block.

TRANSMISSION CONTROL UNIT

SHIFT LOGIC

· 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.
The gear command is passed to the Transmission block to select the desired gear ratio.

EM CONTROL UNIT

EM control unit controls the torque output based throttle input.

BRAKE CONTROLLER

Brake Control unit Produce required brake torque according to the brake pedal input and passes the brake torque in to the wheel block in the transmission model.

POWERTRAIN

The powertrain model includes all the components that convert the power of the engine into vehicle motion.
This includes Engine, Transmission, Differential, Wheels and the vehicle body dynamics subsystems.

ENGINE BLOCK

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 Transmission block.
The 2D lookup table is used to calculate the fuel flow rate based on engine speed and engine torque. The fuel flow rate is then integrated to find the fuel consumption.
Estimated fuel flow rate, fuel consumption, engine torque and engine speed are passed to the MATLAB workspace using the to-workspace block.
Engine fuel flow rate and Fuel consumption are scoped.

MOTOR BLOCK

CRANK HUB

TRANSMISSION BLOCK

The engine block is connected to the automatic transmission via a torque converter. The output of the transmission is connected to the differential.

TORQUE CONVERTOR BLOCK

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.

DIFFERENTIAL BLOCK

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

WHEELS BLOCK

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 BLOCK

The longitudinal dynamics of the vehicle along with the road load is represented in the 'Vehicle Dynamics' block.

ELECTRICAL SUBSYSTEM BLOCK

Tractive Force and Road loads are used to calculate the vehicle velocity,

ηt⋅λt⋅Te/Rω= M dVveh/dt + ½(ρa.Af.Cd.(Vveh+Vωd)^2 + CrMgcosθ + Mgsinθ

ηt⋅λt⋅Te/Rω= Tractive force

½(ρa.Af.Cd.(Vveh+Vωd)^2 + CrMgcosθ + Mgsinθ = Road Load

Where,

ρa−Air Density

Af−-Frontal Area

Cd−-Drag Coefficient

Cr−-Rolling Coefficient

M−-Mass of Vehicle

g−-Acceleration due to gravity

θ−-Slope

The variables are loaded on the workspace using MATLAB script.
The Acceleration, Velocity and Distance travelled are Calculation and stored in the workspace
SIMULATION RESULTS

1. UDDS Drive Cycle

Drive Cycle and Actual Velocity :



Control Signal (Engine Torque, Transmission Gear and Brake Torque) :



Engine Fuel Rate and Fuel Consumption :



Engine Torque:
ear Ratio, Transmission Input and Output Speed :



Tractive Force, Road Load and Acceleration :
HWFET Drive Cycle

Drive Cycle and Actual Velocity :
Control Signal (Engine Torque, Transmission Gear and Brake Torque) :
Engine Fuel Rate and Fuel Consumption :
Engine Torque:
Gear Ratio, Transimission Input and Output Speed :
Different Road Load :
Tractive Force, Road Load and Acceleration :
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.
%% Skill-Lync -> Hybrid Drives Development

% Project 1 - Conventional Vehicle Model

% By - Ullekh Gambhira

�scription:

% 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.

�sed on the project task, use commands in a similar format as given

�low, 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;          �celerator 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]

%�ta Analysis

Eng_Pwr = Eng_Spd*pi/30.*Eng_Trq/1000;   % Engine brake power [kW]

rho_petrol = 0.7197;                    �nsity of petrol [kg/L]

kmpl = Veh_Dist(end)/(Eng_Fuel_Consump(end)/1000/rho_petrol);    % Fuel economy [kmpl]

%% Plotting vehicle characteristics time trace

figure()

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, 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');

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 p4],{'Max Curve','Operating Points'});

axis([Eng_map_spd(1)*30/pi Eng_map_spd(end)*30/pi 0 Eng_map_trq(end)]);

2. Fuel economy numbers (kmph) for UDDS and HWFET cycle.
UDDS:
HWFET:
3. The time trace for engine, transmission input, transmission output and wheel speed

UDDS :
HWFET :
- Much of the fluctuating input speed is facilitated 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 gear and differential ratio.
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.
  - Acceleration and brake pedals are used more because the drive cycle is not very smooth and the gear has to be shifted frequently.
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.
HWFET :
The engine operating points are plotted on the fuel map and the operating point is under the maximum torque curve.

Project 2

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in your own course.