Week-4 Challenge WOT Condition Part-2

Q:- 1. What is the difference between mapped and dynamic model of engine, motor and generator? How can you change model type? 

Ans:-

Power train blockset provides the two types of combusition engines: mapped and dynamic

Mapped engine: Model uses a set of steady-state lookup tables to characterize engine performance(break torque, feul flow, air mass flow, exhaust temparature,efficiency and emissions).

mapped engines models are suitable for analysis and design activiteis that do not require engine substem dynamic characteristics.

mapped system are represent macro engine behaviour as a set of lookup tables as functions of commanded load and measured engine speed of the vehicle.

the mapped motor selection path is evrefferenceapplication ----- passenger car ---- electrical plant ---- motor ---- mapped.

Dynamic model: Model decomposes the engine behavior into engine characteristics that are separated into lower-level components. By combining components in this way, the models capture the dynamic effects.

Dynamic engine models are suitable for designing control, estimators, diagnostic, algorthims that depends on dynamic subsystem states.

the mapped motor selection path is evrefferenceapplication ----- passenger car ---- electrical plant ---- motor ----dynamic model

here, now we can switch between the mapped and dynamic engines by following below procedures.

1. open the Evrefferenc application model in simulink.

2. enter into the passenger car block by double clicking on the subsystem block .

3. go to the electrical plant subsystem block by doule clicking.

4 . select the motor block subsystem in the inside of the electrical plant subsystem.

5. right click on the motor block to find the variant option.

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Q:-2. How does the model calculate miles per gallon? Which factors are considered to model fuel flow? 

Ans:- For conventional gasoline vehicle, the fule efficiency is calculated via Miles per gallon (mpg). however fuel efficiency of the hybride electrical vehicle is calculated cia miles per galllon equivalent (mpge). mpg is the number of miles your car can derive per gallon of gas. figuring out an mpge rating is little more complecated. since engines that can use an alternative source of the fuel cant be measured by liquid gallons of fuel, the mpge rating is calculated by figuring out the number of miles a vehicle can drive using the same energy content as gallon of gas. the epa calculated that 33.7 KWH of electricity is equivalent to one gallon of gas.

we should go inside of hev refference application that performance calculations: 

double clicking the performance calculation subsystem will get actual mpg calculations.

here, there are different inputs are taken into considerations:

1. vehicle speed.

2. fuel flow.

3. battery power.

The vehicle speed inputs is in m/s which converted into miles by multiplying with 0.000621371.

similarly, the kilogram of fuel is converted into cubic meter by multiplying by1/(1000 * 0.739).

this cubic meter value is then converted into gallons by multiplying it with 264.172. the mile value and gallon value is used to find mpg of the vehicle.

now the battery value is initially converted from watts to kwh by dividing with 1000 and then to gallon equivalent by again dividing it with 33.7 ( since 33.7Kw= 1gallon).

then divide the value by 3600 to gert in per seconds and multipy by the 0.00378541 into get value in cubic meter per gallons.

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Q:-3.Run the HEV ReferenceApplication with WOT drive cycle. Change the grade and wind velocity in the environment block. Comment on the results.

Ans:-

HEV reference application with WOT drive cycle:-

use the command ' autoblkHevStart' in the command window to open the HEV reference application. then double click drive cycle source block and then change the drive cycle to 'WOT' as shown in the dropdown. Also configure the parameters like time duration, Wot start time, initial speed, final speed, max speed and time to start deceleration.

change the wind speed and grade from environment block.

the following graphs are obtained for WOT analysis.

from the above graphs we can see that, 

Trace velocity target and actual graph: the yellow line indicates the desited path and blue line is the actual path. so it can be seen that battery powe is not wnough to meet the requirements of the grade and wind velocity.

Battery current Graph: When the vehicle is accelerating the battery cirrent is also increasing. when the velocity is constant the current rquirement also becomes constant. when the deceleration starts the battery current becomes negative and its indicating the regenerative breaking.

Battery SOC: The battery SOC keeps on depending until regenerative braking starts. This increases the SOC.

Engine, Motor and generator speed: initially only motor is used to start the vehicle as motor has high initial torque. later generator(red line) kicks in charging the batteru when SOC drops below 70% enginegraph can't be seen as it mau have overlaped with generator.

Engine, Motor and generator torque: Motor torque is high initially(blue line) and then the engine kicks in at a later stage(yellow line).generator torque (red line) is negative as its charging the battery.

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Q:-4. Keeping all other parameters same, compare the simulated results of hybrid and pure electric powertrains. 

Ans:-

Now simulating the EV with WOT drivecycle, wind velocity as 5m/s, grade as 5 degree and keeping the rest of the parameters same as above HEV case.

we get the following performance graphs:

After comparing the graphs of both EV and HEV following conclusions can be drawin:

1. The first graph ( target and actual velocity graph) performance is almost same. the reason could be that in that region only motor was operating so the performance in both EV and HEV is similar.

2. The battery current drawn by HEV initially is upto 500A and later decreases to 200A. This can be attributed to the fact that initially only motor takes all the load and later engine kicks in so motor load drops this current drawn by motor reduces. And during the deceleration it is seen that negative current ( regenerative braking) flows for a longer time in HEV as compared to EV. so we van say that, regenerative braking is more aggressive in HEV.

3. SOC impovement of almost 15% is seen in HEV during deceleration and only 2% improvement can be seen in EV during deceleration. This can be understood by the same reasin explained in point2.

4. motortorque and motor speed are stable in EV and they keep fluctuating a lot in HEV during the starting. Also the peak RPM of the motor in EV is less than HEV. These differences can attributed to the fact that batteru power of EV is more than HEV.

5. Fuel economy of the EV is significantly greater than HEV. this is because electric motor is more efficient than engine.

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