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 setting in powertrain blockset.It is used to measure to 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 value of brake torque,commanded torque and engine speed.if any other parameters like input engine temperature is selected then lookup table value are also a function of the temperature parameter.the data extracted from lookup table 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 users 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 subsystem 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 change are made.input torque or speed can be specified,elecrical losses and maximum motor power and torque can be defined.

dynamic motor:

In the dynamic motor 3 phases interior permanent magnet synchronous motor(pmsm)is used.the block uses 3 phases input voltages to regulate the intividual phase current,allowing control of the motor torque or speed.this block is used then the particular simulation.this motoris more accurate.

Mapped generator:

the mapped generator block is also similar like other blocks.most of the data requires is taken from the lookup tables corresponding on the given input parameters.its simulation time is less.

dynamic generator:

the dynamic generators involves user entering the parameters manually during the run time for their particular applications. the results take time and more accurate.

open the hybrid matlab powertrain file as upload below,

open the passenger car block.and open sub block of electric plant upload and mention below,

open open the generator block and sub blocks as seen below,

Right click and select following options to change the model

>>variant

>>label mode active choice

>>GenDynamic.

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

Factor affecting the fuel efficiency are listed below.

• vehicle speed
• battery power
• fuel flow

MPGe: In the US to compare the efficiency of gasoline vehicle with the BEV,PHEVs, or FCEVs MPGe unit was formulated.MPGe stands for mile per gallon equivalent.it has been found that 1 gallon of gas ,same amount of energy as 33.7 kwh of electricity.theis rating given by environmental protection agency(EPA).

the above rating has two value as it is a PHEV.one is for pure EV mode and other one is for pure engine mode.

eg. A battery propells the vehicle for 3.125 miles per kwh capacity of battery. so

3.125 miles/kwh*33.7kwh/gallo=105MPGe

in this model calculated by this block:performance calculation upload below

the input are vehicle speed,fuel volume flow & battery power.

below image has two fuels, electricity and fuel.as discussed earlier 1 gallon of gas equal to 33.7 kwh of electricity.

so battery power is first converted into kw (w/1000) then its divide by 33.7kwh.the fuel equivalent of battery is added to the fuel flow.using the vehicle speed and time the distance of travel is calculated.the distance is converted into miles by conversions.then we have the flue flow in m^3 nd distance in miles.we can calculate the fuel efficiency.

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

• double click the drive cycle source block
• change the drive cycle to 'WOT'
• parameters like time duration,WOT start time,initial speed,final speed,max speed and time to start deceleration.
• click to run button.set the time for 100 seconds following are results mention below. and set the wind and velocity is 5.

RESULT:-

current goes to 235 and then decreases,peak RPM is about 9000

making change the wind and velocity and grade to set grade=5;velocity =5; output upload below.

• trace velocity target and actual graph: yellow line indiacate desired path ,blue line actual path.so it can be seen that battery power is not enough to meet requirements of the grade and wind velocity.
• battery current graph: when the vehicle is accelerating the battery current is also increasing .velocity is constant current requirement is constant .when the decelerating starts the battery current becomes negative indiacating regenerative braking.
• battery soc: the battery soc keeps on depleting until regenerative braking starts.
• engine,motor and generator speed: initial only motor is used to start the vehicle as motor has high initial torque.later generator(red line)kicks in charging the battery when soc drops below 70% engine graph can't be seen as it may have overlaped with generator.
• engine,motor and generator torque: motor torque is high initially (blue line) and then engine kicks in at a later stage (yellow line).generator torque(red line) is negative as its charging the battery

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

now the simulation the EV with WOT drive cycle. wind velocity as 5m/s,grade as 5 degree and keeping the rest of the parameters same as HEVMM case.

we get the following performance graphs: and mention upload below.

after comapring the graphs 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 500A and later decreasing 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 that current drawn by motor reduces.during deceleration it is seen that negative current flows for a longer time in HEV compare to EV.

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 fluctuation a lot in HEV during the starting.also the peak RPM of the motor in EV is less than HEV. these different can attributed to the fact that battery power of EV is more than EV.

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