Week-4 Challenge WOT Condition Part-2

QUESTION 1:

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

Ans:powertrain blockset provides two types of combustion engine models:mapped and dynamic.

Mapped engine:

1.Mapped engines represent macro engine behaviour as a set of lookup tables(brake torque,fuel flow,air masflow,exhaust temperature,efficiency and emissions) as functions of commanded load and measured engine speed.

2.Mapped engine models are suitable for analysis and design activities that do not require enigne subsystem dynamic characteristics,for example in egine and transmission powertrain matching analysis for fuel economy,emissions and performance trade-offs.

Mapped Engine is the default settings in powertrain blockset. It is used to measure to measure performance parameters of the vehicle by using standard lookup tables which are prefed to the system. This type of modelling is less accurate. The lookup tables value are based on the values of brake torque, commanded torque and engine speed. If any other parameter like Input engine temperature is selected then lookup table values are also a function of the temperature parameter. The data extracted from lookup tables are: air mass flow, fuel flow, emission data, exhaust temperature and efficiency. This data is used to find out other parameters which are needed by the end user.

Dynamic engine:

1.Dynamic engine decompose engine behaviour into individual component models that account for engine dynamics,most notably intake airflow and turbo charger dynamics.

2.Dynamics engine models are suitable for desiging control,estimator and diagnostic,algorthims that depend on dynamic subsysytem states,for example in closed loop AFR(air fuel ratio)control algorithm development.

 This type of model uses real time data fed by the user at run time for modelling. This model is more accurate than mapped engine model. This type of model is used when the data of subsystems of a vehicle is required. We can calculate : Brake torque, fuel flow, port gas mass flow, exhaust temperature, exhaust mass flow rate and exhaust emissions.

Mapped Motor: The mapped motor works in torque control mode. This type of motor is used when the user requires a faster simulation and doesn't have the knowledge of motor parameters. The output torque and reference torque is compared and changes are made. Input torque or speed can be specified, electrical losses and maximum motor power and torque can be defined.

Dynamic Motor: In the dynamic motor a three phase interior permanent magnet synchronous motor (PMSM) is used. The block uses three phase input voltages to regulate the individual phase currents, allowing control of the motor torque or speed. This block is used when the user knows what parameters are to be used in that particular simulation. This motor is more accurate.

Mapped Generator: The mapped generator block is also similar like other blocks. Most of the data required is taken from the lookup tables corresponding to the given input parameters. Its simulation time is less.

Dynamic Generator: The dynamic generator involves user entering the parameters manually during the run time for their particular applications. The results take time and are more accurate.  

We can switch between mapped and dynamic engines by following below procedures:

1.oepn the ev model in simulink.

2.enter the passenger car block by double clicking it.

3.then go to electric plant block.

4.inside the motor block right click to find the variant option.

Type		Implementation	When to Use
Mapped	CiMappedEngine SiMappedEngine	Model uses a set of steady-state lookup tables to characterize engine performance. The tables provide overall engine characteristics, including actual torque, fuel flow rate, BSFC, and engine-out exhaust emissions.	If you have engine data from a dynamometer or a design tool like GT-POWER. For quasi steady-state engine simulations.
Dynamic	CiEngine SiEngine	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.	If you need a more detailed dynamic model and have component-level data. To analyze the impact of individual engine components on the overall performance.

question 2:

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

Ans:

Miles per gallon (mpg) & miles per gallon equivalent (mpge):

for a conventional gasoline vehicle,the fuel efficiency is calculated via miles per gallon (mpg).however fuel efficiency for hybrid electric vehicles is calculated via miles per gallon equivalent(pge).mpg is the number of miles your car can drive per gallon of gas.figuring out an mpge rating is a littile more complicated.since engines that can use an alternative source of fuel cant be measured by liquid gallons of fuel,the mpge rating is calculated by figuring out the number of milles a vehicle can go using the same energy content as gallon of gas.the epa calculated that 33.7 kilowatt hours of electriccity is equivalent to one gallon of gas.

We should go inside ev reference block that is performance calculations:

inside this block will get actual mpg calculations:

Here,three different inputs are taken into considerations:

1.vehicle speed.

2.fuel flow.

3.battery power.

The vehicle speed inputs is in m/s which is 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(sincw 33.7 kwh=1 gallon)

then divide the value by 3600 to get in per seconds and multiply by 0.00378541nto get the value in cubic meter per gallons.

QUESTION 3:

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

here we have changed drive cycle to wot with a sample time 40 seconds.

we have also altered environment block and changed wind speed to 25 m/s & grade to 10.

environment block:

Results:

Conclusion:

plot 1:trace velocity,target,actual:

top velocity achieved =50.1 mph.

time taken to accelerate = 29.034 sec.

time taken to deaccelerate = 2.471  sec.

plot 2: motor&engine rpm:

top motor rpm=5712 rpm.

top engine rpm = 5451 rpm.

plot 3:motor& engine torque:

maximum motor torque = 306.6 N-m.

maximum engine torque = 174.7 N-m.

plot 4:battery current:

the battery supply current is at its maximum value of 167 ampere when full throttle is applied by the user it reduces drastically to the value of negative 150 during deaccelaration of the vehicle.

plot 5:battery soc:

the battery soc will falls from 80 to 65 % during accelaration of vehicle and it increases slightly to 65 to 70 % during de accelaration due to regenerative braking.

plot 6:fuel economy:

maximum fuel economy achieved = 4.675 .

QUESTION 4:

4. keeping all the parameters same,compare the simulated results of pure and hybird electric powertrains.

Ans:

simulated results of hev:

simulated results of ev:

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

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 500 A and later decreases to 200 A. This can be attributed to the fact that initially only motor takes all the load and later engine kicks in so motor load drops thus 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 can say that, regenerative braking is more aggressive in HEV.

3. SOC improvement 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 reason explained in point 2.

4. Motor torque 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 battery power of EV is more than HEV.

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

Conclusion:

1.The top speed is achieved by hybrid electric vehicle is more than that of EV.

2.The battery current capacity of pure EV is much higher compared to that of HEV since in EV battery is the only driving unit.

3.Higher fuel economy is achieved in case of pure EV.