Embedded Final Project

Michigan Technological University
Final Report
Design of a control system for a
configurable hybrid electric
vehicle
Final project
Amol Galande
5/2/2013

Index
1. Project Summary…………………………………………………………………………………………………………………1
2. Introduction……………………………………………………………………………………………………………………….3
3. Model development…………………………………………………………………………………………………………..4
4. Validation………………………………………………………………………………………………………………………….14
5. Validation in MotoTron……………………………………………………………………………………………………..27
6. Conclusion…………………………………………………………………………………………………………………………47.

Project summary:
The primary aim of the project is to develop a multi component control system model for the
configurable hybrid electric vehicle using embedded system design.
Figure 1: Configurable hybrid electric vehicle.
Figure 1 shows the configurable hybrid electric vehicle for which the control system is being developed.
The hybrid electric vehicle has a complex architecture and has three modes of operation the electric
solo mode, the blending mode and the engine only mode. The components like the IC engine, the
Battery pack, Electric motor that works as a motor or a generator depending mode of operation need to
be controlled simultaneously. Hence an efficient and effective control system is essential in controlling
the synchronized working each component together.
The Control Module for the hybrid electric vehicle consists of three modules i.e. sensor module the
control module and the actuator module.
Sensor Module: The main components that are being controlled in the hybrid electric vehicle are the
engine, motor and the battery. The working of each of these components has to follow a logic which is
depended on the parameters of the vehicle. In order to detect signals from of the engine, the motor, the
battery and other vehicle parameters the sensor as used to convert the physical data into signals that
can be used by the ECU. It is an interface between the hardware and the ECU i.e. the control module.

Control Module: The control Module is the block that consist the logic and the inter relationship of each
of the components working together. Based on the inputs provided by the control module provides
control signals to move the actuators to the desired position.
Actuator Module: The control signals generated by the control system are used to actuate the engine
throttle or the motor torque request by varying the current being supplied to the motor etc.
INPUT &OUTPUT Signals:
The following inputs were provided to the control system:
• Motor On Switch: Electric Solo Mode
• Engine on Switch: Engine Solo Mode
• Forward Switch: move forward switch in Electric Solo Mode
• Reverse Switch: move backward switch in Electric Solo Mode
• Crank Switch: vehicle key switch
• Accelerator Pedal Position (APP): speed/torque request command
• Engine Average RPM: engine speed sensor input
• Vehicle Speed: vehicle speed sensor input
• Throttle Position Sensor (TPS): throttle position sensor input
The following are the output signals provided by the control system:
• E-motor Torque Request: the power control signal of the E-motor
• E-motor On: a control signal to turn on the E-motor
• Forward: the motor moves forward.
• Reverse: the motor moves backward.
• Engine Crank: a control signal to start engine
• Engine Kill: a control signal to stop engine
• Driving signals for four stepper motor coils

Introduction:
A hybrid electric vehicle basically uses an electric motor and a gasoline engine to power the vehicle. The
opportunistic use of the electric motor during time periods, where the IC engine is in efficient and is
ineffective results in reduction in fuel consumption of the vehicle. This helps improve the fuel economy
of the vehicle and the range for which the vehicle can run. The reduction in fuel consumption is gaining
importance with the increasing crisis of energy resources and rising fuel prices.
The hybrid electric vehicle can be classified based on the configuration of the electric motor and IC
engine i.e. the series configuration and the parallel configuration. In the series configuration the Engine
is not connected to the wheel but is used to the power the generator and recharge the battery pack. The
E-motor is used to power the wheels and provide required amount of torque to the wheels. The main
drawback of this configuration is that energy is converted from heat to electric to chemical and back to
electric and mechanical to power the vehicle. This results in high amount of conversion loses and is
inefficient, hence the series configuration is not utilized in the current vehicles.
The parallel configuration has both the IC engine and the electric motor providing torque to the wheels
based on the torque request. The battery pack is used power the electric motor which can be recharged
either by regenerative braking or by an electric grid plug in. The parallel configuration allows the vehicle
to be run in three modes the electric mode, the blending mode and the engine only mode.
In the electric mode the electric motor is the primary power source while the engine is turned off. Thus
the vehicle does not use any fuel in this mode provides the required torque output. This mode can be
highly effective in the low speed city driving as the engine is inefficient at low speeds and has high brake
specific fuel consumption at lower rpms.
In the blending mode the engine and the electric motor simultaneously power the vehicle through the
transmission. The torque provided by the E- motor and the engine add up to meet the torque
requirements. Based on the speed the percentage of torque supplied by the motor and engine changes
i.e. the blend factor for the E-motor and the Engine changes. The main advantage of this mode is that
the engine is being run at an rpm with lowest brake specific fuel consumption, thus improving fuel
economy.
The IC engine only is the only power source used in the engine only mode and used at high speeds i.e.
highway. The essentially factor in the functioning of a hybrid electric vehicle is the synchronous working
of it electric and gasoline systems. Using embedded control systems the control logic for the hybrid
electric vehicle can be uploaded into an ECU to facilitate efficient control and also can be used for on
board diagnostics systems. The Engine control unit replaces the conventional wire and link based control
system thus improving the efficiency and accuracy of the system.

Model Development:
The model development of the control system is based on the following control logic.
Figure 2: Top layer of the control logic
Figure 2 shows the top layer of the control module showing the relationships of the sensor inputs the
control inputs and the actuator outputs.
The control module has different sub model each controlling a set of parameters
1. Driving mode model.
2. Blend Factor look up tables
3. Engine State logic model
4. Torque/Throttle request model
5. Engine start/stop model
6. E-motor start/stop model
7. Stepper motor driving model.

1. Driving mode model
This model determines the mode in which the hybrid electric vehicle is functioning.
Mode 1: Electric solo mode
Mode 2: Blending mode
Mode 3: Engine only mode.
Table 1: Control logic for driving mode model
Engine on
Switch
Motor on
Switch
Vehicle
Speed
Electric solo
mode (1)
Blending
mode (2)
Engine solo
mode (3)
True False v<1 mph False False True
False True True False False
False False False True False
True True N/A N/A N/A
v>1 mph Driving Mode will stay unchanged
Figure 3: Driving mode model (top layer)
Figure 3 shows the top layer of the control logic used to determine the driving mode of the vehicle. Here
the truth table is provided with the Engine On, Motor On and Vehicle speed inputs and the driving mode
is the output.

Figure 4: Control logic for Driving mode (bottom layer)
Here the truth table follows the control logic defined in the table 1. The electric solo mode is turned on
when the conditions in the column 2 are matched, the blending mode is on when the conditions in the
column 3 are matched and similarly when the conditions in the column 1 are matched the engine mode
is on. There is an added condition of mode change when the vehicle speed below 1mph above the speed
of 1 mph the driving mode is N which is the same mode as the previous driving mode and hence driving
mode does not change above 1mph.
Figure 5: Blend factor look up table
Figure 5 shows the blend factor lookup table model. As the name suggests this model basically uses two
2-D look up tables with Accelerator pedal position and vehicle speed as their inputs. With changing APP
and vehicle speed the E-motor blend factor and the Engine blend factors changes.

3. Engine State logic model.
The Engine state model as the name suggests is used to map the sequence in which the engine starts up
or fails to start. It can be used as a diagnostic tool in case the engine has a fault in it. Depending on the
state at which the engine stopped fault finding or debugging the engine problem becomes easier. The
Engine has 5 states namely 1] Engine Off state 2] Engine Crank state 3] Engine Warm-up state 4] Engine
On state 5] Engine start fail state.
Table 2: Condition for Engine states model
Here three inputs are provided to the engine states model the Engine Rpm that provides the current
rpm of the engine, the engine crank it is a binary input to the model that turn 1 when the engine is crank
to start the engine and the engine kill is used to switch the engine off manually.
Figure 6: Top layer for engine states model.

Figure 7: Control logic for engine states model.
Here the Engine off state is given as the default state, when the engine crank input changes to 1 the
state changes to state 2 i.e. the crank state. The command temporalCount(sec) is used to count the time
for which the state 2 is active. If the engine rpm is below 800 after 1 sec, the engine transitions to
engine state 5 and if the engine rpm is above 800 after 0.6 seconds, then engine reaches the warm up
state. Similarly in state 3 if the engine rpm is greater than 500 after 1 sec the engine transitions to the
engine on state else it reaches the state 5.
4. Torque and throttle request model.
The torque and throttle request model regulates the torque being output from the e-motor and the IC
engine. Here the model control logic can be divided into the Engine throttle request logic and the E
motor torque request logic.
Table 3: Control logic for engine throttle request
Conditions Driving Mode Electric solo
mode (1)
Blending mode
(2)
Blending mode
(2)
Engine solo
mode (3)
Engine State No impact ==2or==3 ==2or==3 Other states No impact
Engine throttle
request
0 7.5 7.5 APP*(Engine
Blend Factor)
APP
The table three defines the Engine throttle request based on different driving modes of the hybrid
electric vehicle.

Table 4: Control logic for E motor torque request
Driving Mode Electric solo mode
(1)
Blending mode
(2)
Engine solo mode
(3)
Motor torque request APP APP*(Motor Blend
Factor)
0
Figure 8: Top layer Throttle/Torque request model
Figure 9: Throttle/Torque request logic bottom layer
The main factor controlling the blend factor of the engine and the E- motor is the driving mode of the
hybrid electric vehicle. In electric solo mode the E-motor torque request matches the APP and in the
Engine solo mode the Engine throttle request matches the APP i.e. in the respective modes they will

provide torque based on the accelerator pedal position. In the blending mode the E motor torque
request is set to a multiple of the APP and the blend factor but the Engine throttle request changes
based on the states of the engine. Here B1 and B2 represent the two modes within blend mode where
the engine throttle request differs. In the mode B1 the Engine throttle request is set as 7.5 while in
mode B2 the throttle request is set as a multiple of the Engine blend factor and the APP.
5. Engine start stop model.
In the hybrid electric vehicle the engine is frequently switched on and off based on the modes of drive
hence to facilitate this engine start stop model is used. Depending on the inputs provided the control
logic determines when to turn the engine off and when to crank the engine.
The engine start stop logic can be divided into three sub logics the engine kill, the manual start and the
engine automatic start. The engine kill logic is used to improve the fuel economy of the vehicle, by
switching off the engine when the engine is being used below its potential it is turned off.
Table 5: Engine Kill logic
Mode Electric solo mode
(1)
Blending mode
(2)
Engine solo mode
(3)
Engine Blend
Factor
No impact >0.01 <0.01 No impact
Engine Kill True False True False
The above table states that in the blending mode when the engine blend factor is below 0.01 i.e. less
than 1% of the engine torque is being used the engine should be turned off as in this state the engine
has a high bsfc thus contributing to increase in fuel consumption.
The manual and automatic engine start logic are the way the driving mode transitions. If the hybrid is in
the engine solo mode the engine has to be turned on when the user cranks it, this uses the manual
crank logic and when the driving mode transitions from electric solo to blending mode the engine has to
be automatically turned on based on the driving force requirement.
Table 6: Manual Crank logic
Driving Mode Electric solo mode
(1)
Blending mode
(2)
Engine solo mode
(3)
Manual Crank False False True when the
Crank Switch is
True

Table 7: Automatic Crank logic.
Conditions Driving Mode Electric solo mode
(1)
Blending mode
(2)
Engine solo mode
(3)
Engine Blend
Factor
Irrelevant >0.01 <0.01 Irrelevant
Engine State Irrelevant ==1 Irrelevant Irrelevant
Automatic Crank False True False False
Figure 10: Engine start stop logic (top layer)
Figure 11: Engine start stop logic

6. E-motor start stop model
Similar to the engine start stop logic the E motor start stop logic is based on the driving mode
transition and the blend factor. The E-motor start stop model is also used to switch the motor
direction to forward or reverse based on the requirement.
Table 8: E- motor On logic
Conditions Driving Mode Electric solo
mode (1)
Blending mode
(2)
Engine solo mode
(3)
Motor Blend
Factor
Irrelevant >0.01 <0.01 Irrelevant
Motor On True True False False
Table 9: E-motor forward & reverse logic
Driving Mode Electric solo mode (1) Blending mode (2) Engine solo mode (3)
Forward signal Forward Switch True False
Reverse signal Reverse Switch False False
`
Figure 12: E-motor start stop logic.
The E motor start logic is used to determine when the E-motor should be switched on or off. Here in the
blending mode when the blend factor of the E-motor is low i.e. less 0.01 it is beneficial to switch off the
E-motor and save battery pack energy. When the E-motor torque request is significant it should be
turned on. The E-motor forward and reverse logic is only functional when the hybrid is driving mode 1.
The forward and reverse switch can facilitate the forward and reverse motion of the vehicle when the
engine is in electric solo mode. E motor forward and reverse state are exclusive to each other and
cannot run simultaneously.

Figure 13: E-motor Start Stop logic
7. Stepper motor logic.
The stepper motor driving model generates driving signals for the coils of the stepper motor
depending on the direction of the motor switch the stepper motor will be driven in the forward or
the reverse direction.
Figure 14: Stepper motor logic
Figure 14 displays the stepper motor logic in the form of a flow chart and a truth table.

Figure 15: Stepper Motor logic.
Figure 16: Stepper Motor Driving model

Model Validation :
1. Driving mode model:
Figure 17: Inputs from the signal generator
Figure 18: Driving Mode logic output
0 20 40 60 80 100 120 140 160 180 200
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
Time (seconds)
DrivingMode
Driving Mode

From figure 17 and 18 it can be seen that for time 1 to 80sec the vehicle speed is below 1mph and the
engine is switched on and off three times the output follows the input and the mode changes to
blending and back to engine solo. At point time t=80 sec the vehicle speed goes beyond 1 mph and
hence the driving mode does not change from mode 2. At time t=120 sec the vehicle speed goes below
1mph and the motor is on hence the driving mode switches to mode 1.
Figure 19: Signal generated for the Blend factor look up tables
Plot 1: E-motor blend factor variation with APP and vehicle speed
0 20 40 60 80 100 120 140 160 180 200
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time (seconds)
Blendfactor
E-motor Blend factor

Plot 2: Engine blend factor output
From the plot 1 and 2 it can be seen that from time 0 to 18.38 sec the vehicle speed is below 5 mph
hence the E-motor blend factor is 1 i.e. it matches APP and at the same time the Engine blend factor is 0.
The vehicle speed increases after t=18.38 sec, the engine blend factor increases and the E-motor blend
factor decreases and the torque request from engine and the motor depend on the blend factor. At time
t=100 sec the accelerator pedal is released and vehicle speed reduces hence the blend factor of motor
increases and that of the engine decreases.
3. Engine State logic model
Figure 20: Input Signals to the Engine State model
0 20 40 60 80 100 120 140 160 180 200
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time (seconds)
EngineBlendFactor
Time Series Plot:

Plot 3: Engine States output
The logic follows the input signal this can be seen from the plot 3 the Engine is cranked at t= 3sec and
transitions from state 1 to 4 as it meets all the conditions during and the engine is in state four i.e. the
engine on state.
Plot 4: Engine time in state 2
0 20 40 60 80 100 120 140 160 180 200
1
1.5
2
2.5
3
3.5
4
4.5
5
Time (seconds)
EngineStates Engine States output

Plot 4 shows that the engine stays in the state 2 for 0.6 sec at this time the engine rpm is above 800 and
hence transitions to state three in state three the state 3 is active for 1sec and then transitions to state
the engine on state.
Plot 5: Engine in state 3
Figure 20 shows that at time t=188.6 sec the engine kill switch is turned on this turns the engine to state
1. At time t=190.6 sec the engine crank is switched on but as the engine kill is on it does not allow the
engine to move into the engine on state.
4. Torque and throttle request model
Figure 21: Input signal for torque and throttle request model

Plot 6: Motor Torque Request
Plot 7: Engine Throttle Request
The above plots show the synchronous working of the Engine and the E motor torque request logics.
From the input signals it can be seen that for three instances the driving mode is 1 i.e. from time t=0 to
20 sec, t=60 to 80 sec and t=100 to 120 sec. The plots show that the Engine is turned off at these
instances and the E-motor is on and the torque provided by the e motor depends on the APP and the
vehicle speed. Similarly the hybrid is for time t=40 to 60sec, t=80 to 100sec and t=150-200 sec the
0 20 40 60 80 100 120 140 160 180 200
0
10
20
30
40
50
60
70
80
90
100
Time (seconds)
MotortorqueRequest
Motor torque
0 20 40 60 80 100 120 140 160 180 200
0
10
20
30
40
50
60
70
80
90
100
Time (seconds)
EngineThrottlerequest

vehicle is in driving mode 3. During these intervals the E- motor is turned off and the engine is on. For
the remaining time periods the vehicle drives in blend mode and the torque provided is the sum of the
torques of the engine and the E-motor.
5. Engine start stop model.
Figure 22: Input signal to Engine start stop model
Plot 8: Engine Crank Plot
0 1 2 3 4 5 6 7 8 9 10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time (seconds)
EngineCrank
Engine crank plot

Plot 9: Engine Kill Plot
The plot above plots display the engine crank and engine kill logic when the blend factor for the engine
is low the engine is switched of for time t=0-3.33sec the blend factor is less than 0.01 hence the engine
is turned off in this case when the engine at 3.33 sec the blend factor goes above 0.01 and hence the
engine is cranked. At t=4 sec the vehicle transitions to driving mode 1 and hence the engine kill is
switched on and the engine is turned off.
6. E-motor start/stop model
Figure 23: E-motor start/stop model
0 1 2 3 4 5 6 7 8 9 10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time (seconds)
EngineKill
Time Series Plot:

Plot 10: E motor on
Plot 11: Forward On
`
Plot 12: Reverse
0 1 2 3 4 5 6 7 8 9 10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time (seconds)
E-motoron
0 1 2 3 4 5 6 7 8 9 10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time (seconds)
Forward
Time Series Plot:
0 1 2 3 4 5 6 7 8 9 10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Time (seconds)
Reverse
Time Series Plot:

The above figure shows that initially the driving mode is 3 and then switches to driving mode 1, the
blend factor is above 0.01 and simultaneously the reverse switch is on thus the motor moves in the
reverse direction. At t=7.8 the forward switch is turned on but the blend factor is below 0.01 so the
motor is switched off.
7. Stepper Motor
Figure 24: Input signal 1 to the stepper motor .
Plot 13: Stepper motor output 1.

Figure 25: Input 2 to the stepper motor
Plot 14: Output 2 for the stepper motor
Plot 13 shows the output when the engine torque request is 35 and the throttle opening is 25% and
hence the motor moves in the clockwise direction. For input 2 the throttle request is 10 and the motor
in this condition rotates in the counter clockwise direction.

5. MotoTron Validation and Results:
Figure 26: Simulink Validation Model (Top layer)
Figure 26 shows the hardware in loop testing model used for validation using MotoTron. It consists of
the three sub systems the sensor module, Control module and the actuator module. The sensor module
is the interface between the hardware and the desktop simulator. The sensor inputs are provided to the
control module and it provides the control output based on the control logic. The control outputs are
provided to the Actuator module.

Figure 27: Validation Circuit diagram
The above figure shows the circuit diagram for the validation circuit. A square wave input with varying
frequency from the function generator is used to simulate the vehicle speed input to the model. Hall
Effect sensor is used to sense engine rpm. A potentiometer is connected to DC motor that is used to
vary the Engine RPM input.
Table 10: Input and output signals
Input Signals
Output Signals

Figure 28: Control Module (Bottom layer)
Validation Tasks:
1. Calibration:
Vehicle Speed Calibration:
The vehicle speed is provided by the function generator to simulate the output of a digital speed sensor.
The vehicle speed is to be set in the range of 0-19 mph; the speed can be varied by varying the
frequency of the square wave input from 100Hz to 290Hz.
The range of frequency in counts = Counts at 290Hz – Counts at 100 Hz
= 29000-10000= 19000.
The vehicle speed gain = speed range/ range of frequency in counts
= 19/19000.
= 0.000998.
Therefore gain =0.000998 and the offset= -10 mph as the range has to be set from 100Hz and not 0Hz.

Figure 29: Vehicle speed calibration
Engine RPM calibration:
The Hall Effect sensor provides Engine RPM from 0-21500 counts. A gain of 0.14 is used to convert the
counts to RPM in a range of 10-3000 rpm. The offset is set to zero.
Figure 30: Engine RPM calibration

APP calibration:
The accelerator pedal has to be in the range of 0-100, the analog input provides pedal position in counts.
In order to convert counts the counts have to be multiplied by a gain (100/1023=0.0978). The offset in
this case is set as zero.
Figure 31: APP Calibration
TPS calibration:
Figure 32: TPS Calibration

The throttle valve has to be in the range of 0-100, the analog input provides throttle position in counts.
In order to convert counts to percentage, the counts have to be multiplied by a gain (100/1023=0.0978).
The offset in this case is set as zero.
2. EST1 output voltage vs. E-motor torque request.
EST1 port is set as the output signal port for E-motor torque request. The vehicle speed is set to 7 mph
as the APP is changed the torque request changes and simultaneously the voltage output from the EST1.
Table 11: E-motor Torque request and EST1 output voltage at different APP
APP E-motor Torque request Voltage
24 17 1.44
50 33 2.115
60 40 2.41
70 46 2.663
80 52 2.991
90 58 3.195
100 63 3.407
3. EST1 output voltage vs. E-motor torque request curve
Plot 15: E-motor torque request vs. EST1 output voltage
Plot 15 shows the change output voltage as the E-motor torque request changes.
0 10 20 30 40 50 60
0
0.5
1
1.5
2
2.5
3
3.5
E-motor torque request (Nm)
EST1outputvoltage(V)
E-motor torque request vs. EST1 output voltage

4. E-motor torque request for different switching inputs, APP and vehicle speed.
Case1: Drive mode=Electric solo mode; vehicle speed < 5mph.
Plot 16: E-motor throttle request
In the electric solo mode the E-motor torque request varies linearly with the APP. In this state the
Engine kill is on and the motor forward is on.

Case 2: Drive mode=Blending mode; 15mph >vehicle speed >5mph.
Plot 17: E-motor torque request at Blending mode
In this case the driving mode is blending and E-motor torque request= (APP * blend factor). In this state
the Engine kill is off and the engine is turned on.

Case 3: Drive mode=Engine only mode; 15mph <vehicle speed
Plot 18: E- motor Torque request at Engine solo mode
In this case the engine solo mode is on and the E-motor is turned off and E-motor torque request is zero.

5. Engine States:
Case 1: Engine Cranked but Engine Rpm =0
Figure 33: Engine changing states from 1-2-5
Figure 34: Display window for changing engine states
The vehicle here is in blending mode and the hence the automatic engine crank switch is on but as the
engine rpm is zero the engine does not go to engine on state, but transitions between states 1-2-5.

Case 2: Engine cranked and Engine transitions from state 1-2-3-4.
Figure 35: Engine state changes from 1-2-3-4.
Figure 36: Engine on state.
In this case after the engine is cranked the engine rpm increases from 0 to 800 from the state 2 and
hence passes to the engine warm up and the engine on state.

Case 3: Engine Kill is switched on.
Figure 37: Engine kill on APP at 80 Engine state 1
Figure 38: Engine kill on APP at 93 engine state 1.
Even after changing the APP the position the Engine kill does not allow the engine to change the engine
state 1.

6. Test E-motor On, Engine-kill and Engine Crank
Case 1: vehicle speed < 5 mph
Figure 39: E motor on, Engine kill on Engine crank off
Here as the vehicle speed is below 5 mph the E-motor is on and the engine kill is on.
Figure 40: E motor on, Engine kill off engine crank on

In the above figure as the vehicle speed goes above 5 mph due the increased torque request the
controller cranks the engine and the switches the engine kill off.
Increasing the vehicle speed further more requires high torque to accelerate and maintain the vehicle at
a constant speed and hence motor here is turned off and the engine solely provides the torque.
7. Improve the model
As the configurable hybrid is not a Plug in hybrid there has to be regenerative braking or opportunity
charging that recharges the depleted battery whenever the state of charge of the battery falls below the
allowable limit.
Regenerative Braking: The concept of regenerative braking is that whenever the vehicle is braking the
i.e. whenever the torque request of the engine is negative and the vehicle speed still above a certain
limit the kinetic energy usually lost as heat through the brake pads can be reclaimed by using
regenerative braking. During deceleration the motor is coupled with the wheels thus turning the motor
in the reverse direction .i.e. motor acts as a generator thus recharging the battery.
Opportunity charging: When the hybrid is in the blending mode and the battery SOC is below the
maximum allowable limit the E-motor is turned off and the Engine torque request is scaled up which is
used to run the motor as a generator, this continues until the battery is charged above the lowest SOC
limit. In the model we have implemented opportunity charging along with hysteresis for the battery
charging. The lower limit of SOC is set at 55% , whenever the battery goes below 55% the engine is
torque request is scaled up to start charging the battery. The battery charging will continue until the
SOC is above 65% thus this does not allow hysteresis while battery charging.

Figure 41: Opportunity charging logic
Figure 42: Battery Protection incorporated
The battery protection logic restricts the battery to be charged above 95% SOC and thus protecting the
battery from being damaged.
Opportunity
charging logic

In order to test the opportunity logic an analog input was added to the model namely SOC. Thus by
varying the analog input the SOC can be varied from 0-100.
Figure 43: SOC above 0.95
Here when the SOC is above 0.95 which is set as the upper limit of charging the battery protection kicks
in and this can be seen from the fact that battery protection flag is 1 and the charge state flag is 0.
Figure 44: 0.95>SOC>0.65

Figure 45: SOC<0.55
As the SOC goes below 0.55 the motor is shut down and the engine torque is used to charge the battery
via the motor.
Figure 46: SOC increasing and greater than 0.55

Now as the SOC increases the charge state flag i.e. charging will be on until the SOC goes above 0.65
Figure 47: SOC increasing an SOC=0.63
Figure 48: SOC increasing and above 0.65
Charge state flag goes off once the SOC goes above 0.65.

8. E-motor Forward and Reverse:
Figure 49: E-motor Forward
As the forward switch is on the E-motor moves in the forward direction while when the reverse switch is
turned on the motor moves in the reverse direction.
Figure 50: Reverse motor direction.

9. Stepper Motor.
Figure 51: Stepper motor plot
The direction of rotation of the stepper motor depends on two factors the engine torque request and
the throttle position sensor. As can be seen from the display window the Engine throttle request is more
than the TPS value hence the diff >1 and the diff>0 hence the motor moves in the Clockwise direction.
In case the Engine throttle request is less than the TPS then the motor moves in the counter clockwise
direction.

Conclusion:
 The control strategy for the configurable hybrid electric vehicle was developed consists of
different sub models.
 Testing of each module both in Matlab and Moto-Tron is essential as the model logic is validated
using simulation and hardware in loop testing.
 Hardware in loop testing is important as it helps in calibrating each hardware component so that
it works in sync with the control logic.
 Fault finding in the logic is important and this is possible by testing the control logic in every
possible condition, this helps in full proofing the model.
 State flow is an effective way of implementing the control logic as the debugging of a complex
control logic becomes easier.

Embedded Final Project

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