Week-4 Challenge WOT Condition Part-2

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

MAPPED ENGINE : Mapped Engine is the default settings in powertrain blocketset. It is used 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 : 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. Open 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.

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

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 electricity is equivalent to one gallon of gas.

Lets 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:

• Vehicle speed
• Fuel flow
• 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 by 1/(1000*0.739). This cubic meter value is then converted into gallons by multiplying it with 2640172. The mile value and gallons 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 33.7kwh = 1gallon

Then divide the value by 3600 to get in per seconds and multiply by 0.00378541 to get the value in cubic meter per gallon.

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

Sol: Opened the HEV multimode reference Application and we have changed drive cycle to WOT with a sample time 40seconds.

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

Environment block:

Results :

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.

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

Sol: Simulated results of Hev:

Simulated results of Ev:

Conclusion:

1. The top speed 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.