Research and Study of Different types of Power-train in Automobile

Aim - Research Study of Different types of Power-train in Automobile

Objective -

• To determine the difference between the Mapped and Dynamic Model of Engine, Motor, and Generator
• To perform Simulink model-based calculation to find outMiles per Gallon requirement for a fuel
• To simulate the model with WOT condition to find out the difference by changing the grade angle and wind velocity.
• To compare the simulated results of hybrid and pure electric powertrains.

Study I

#Difference between the mapped & dynamic model & changing the model type.

Mapped Model(Static):

This type of model will have the lookup table frow where the data is taken and the simulation is run. This runs faster based on the data in the lookup table.

Lookup tables -

Dynamic Model:

This type of model will have the actual component from which the data is taken by providing the inputs and the simulation is carried out to get the results. This will take a long time for simulation than compared to the mapped model.

#Difference between the mapped and dynamic model of engine

Mapped Model of Engine:

In the mapped model of an Engine, there is an engine block for which the input is taken from either the lookup table or else from the spreadsheet. The data can also be taken from the model workspace if you have already data available with you for the engines. Here for the mapped engine, the input is the torque command and the engine speed. If we click on those blocks there is an option to connect the input from spreadsheets or workspace. This is shown below in the image.

If we look under the mask of the engine model we may see the lookup table for the engine core block.

Dynamic Model of Engine:

In a dynamic model of an engine, the input data is taken from the actual components of the engine. The components are linked with each other representing the actual model. The input values are given to the particular blocks of the component and the required output is passed on to the engine to run the simulation. In a dynamic model, the data from each block is of prime importance to run the simulation. A dynamic model of the engine is represented below

Here we can see how the actual component is linked with the engine. The data of each component is compiled with the engine and the model is simulated using this data.

#Difference between the mapped and dynamic model of motor:

Mapped Model of Motor:

In the mapped model of a motor, the input is supplied through the data from the workspace. The spreadsheet can also be linked to run the simulation Three inputs need to be supplied to get the rated current and torque from the motor to run the vehicle. Three inputs are BusVolt, Motor Speed & Motor Torque Command.

Dynamic Model of Motor:

In a dynamic model of a motor, three actual components are used to run the simulation. Three components are Interior PM Controller, Three Phase Voltage Source Inverter & Interior PMSM SS Speed. The controlled voltage is supplied to the motor with the use of a controller and inverter along with the motor speed to generate the required torque for a vehicle.

#Difference between the mapped and dynamic model of generator:-

Mapped Model of Generator:

In the mapped model of a generator, the input is supplied through the data from the workspace. The spreadsheet can also be linked to run the simulation Three inputs need to be supplied to get the rated current and torque from the generator to charge the battery. Three inputs are BusVolt, Generator Speed & Generator Torque Command.

Dynamic Model of Generator:

In a dynamic model of a generator, three actual components are used to run the simulation. Three components are Interior PM Controller, Three Phase Voltage Source Inverter & Interior PMSM SS Speed. The controlled speed is supplied through the motor to the generator with the use of a controller and inverter along with the motor speed to generate the required current to be stored in the battery.

How to change the model type

To change the model type we have to go to the main subsystem block of the engine where all the other model is present inside the subsystem block.

Right-click on the same model and go to the variant tab. Under this tab, there is an option for label mode active choice. Select the choice of model. The way to change the model is represented below through an image,

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Study II

#Performed Simulink model-based calculation to find outMiles per Gallon requirement for a fuel

figure - Miles Per Gallons Estimation

Battery Power Estimation

figure - Battery Power Estimation

• The battery power is drawn from the battery to run the motor(Hybrid Case).
• The battery power is in W(watt) so converting this to kW using product block where the watt unit is converted into kW.
• One more product block is used to covert the power in kwh/USgal equivalent.
• Again one product block is used to covert the seconds in an hour.
• Next, the gain block is used to covert the power in cubic meters to gallon.

Fuel Volume Flow

• Mass of fuel is added with the battery power and integrated concerning time to get the volumetric fuel flow in a cubic meter.
• This fuel flow is then converted from cubic meter to liter using gain block and then multiplied with the vehicle speed to calculate the volume fuel requirement per 100 km.

Vehicle Speed

• The vehicle speed is taken and then it is squared using the product block. Next, its square root is taken using the square root block considering the deceleration case where the vehicle speed can be negative.
• The integration block is added below the gain block to integrate the vehicle speed concerning time to get the distance in the meter.
• Next, the gain block is used to covert the speed to 100 km. The saturation block will function in such a way that if the value of vehicle speed is above the specified limit then it will pass the same value ahead or else it will pass the lower limit value to the next block.
• Then the product block is used to calculate the liter of fuel required per 100 km (L/100 Km Calc).

To calculate Miles per Gallon

• Two inputs are taken simultaneously one is vehicle speed in m(meter) and second the fuel flow in m^3(cubic meter). Speed is then converted into a mile using the gain block and fuel flow into the gallon.

• Saturation block is added after the conversion of fuel in US gallons to limit the specification value of a conversion.
• Next, the product of miles per US gallon is done using the product block and this is how the model calculates the miles per gallon of fuel.

Factors considered for modeling fuel flow

From the above image of MPG, we can say that three factors are considered to model the flow of fuel for this model because this is the case in the Hybrid Electric Vehicle model. Here the fuel flow will depend upon the flow of fuel, the battery power & the speed of the vehicle.

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Study III

#Simulated the model with WOT condition to find out the difference by changing the grade angle and wind velocity

WOT drive cycle is used to simulate the HEV Ref Application Model with & without changing the grade and wind velocity. The results of both are represented below.

Case I - WOT without grade and wind velocity

Case II - WOT with grade angle 10 Deg and wind velocity 31 mph

Results:

1) Drive Cycle - Looking at the above two results we can say when the grade angle and wind velocity are added there is a decrement in the velocity of a vehicle. The maximum velocity in 70 mph is Case I and 28 mph(approx) in Case II.

2) Battery Current (A) - Battery Current is varied from 0 to 500 A in case II till 20 sec of acceleration time and then it went negative for deceleration period and while on the other hand, it started decreasing in case I from 17 sec onward only.

3) Engine, Motor & Generator Speed - Till acceleration time the motor speed was found to be maximum to value of 8000 rpm in case 1, and engine and generator are not activated during this time. In case II the maximum speed of the motor was 8000 rpm(approx) and during the deceleration period due to braking regenerative action, the motor is acting as a generator and it got activated.

4) SOC (State of Charge) - The Battery State of Charge after completing the drive cycle is 72% in case I. In Case II the battery found to be charging after 21 sec during deceleration due to regenerative action and it is charged to 72% from 70%.

5) Engine, Motor & Generator Torque - In Case I during the acceleration period the motor was running, and torque was positive. After that during the deceleration motor torque is negative. In case II during deceleration, from 21 sec the generator got activated due to regenerative action, and engine torque is positive.

6) Fuel Economy - The fuel economy in Case I is 16 MPGe and 4 MPGe in Case II. It says that when the vehicle is subjected to grade angle and wind velocity there will be a decrement in the fuel economy.

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Study IV

#Comparison of the simulated results of hybrid and pure electric powertrains.

The Simulation is run for 50 sec using the WOT cycle with a nominal reference speed of 40m/s and deceleration start after 30 sec. The results are represented below,

Hybrid Electric Powertrain

Output Result Plot -

Pure Electric Powertrain

Output Result Plot-

Result Comparison:

In HEV, the vehicle can attend the maximum speed of 90 mph in 25 sec. Here we see the actual velocity curve is not following the trace velocity curve because the battery current is limited to 500A. The engine and generator are following the same path as the generator is run by an engine. The motor can attend the maximum speed of 11000 rpm(approx). After 25 sec the battery current is negative because the braking regenerative action comes into effect due to the deceleration of the vehicle. The battery state of charge is increased during the deceleration because the torque of a motor is negative and it acts as a generator. The battery state of charge before deceleration was 68% and it is increased to 75% after regeneration action. The fuel economy at the end of the driving cycle is 7MPGe.

In Pure EV, the vehicle can attend the maximum speed of 90 mph in 25-sec. Here we see the actual velocity curve is not following the trace velocity curve because the battery current is limited to 225A. The motor can attend the maximum speed of 9300 rpm(approx). After 30 sec the battery current is negative because the braking regenerative action comes into effect due to the deceleration of the vehicle. The battery state of charge is increased during the deceleration because the torque of a motor is negative and it acts as a generator. The battery state of charge before deceleration was 77.6% and it is increased to 77.9% after regeneration action. The fuel economy at the end of the driving cycle is 42MPGe(approx).

From the above two-vehicle comparison Pure EC controller is more efficient than the HEV controller. The efficiency of HEV is better than EV at the same velocity.

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