WOT Condition Part-2
Q1: What is the difference between mapped and dynamic model of engine, motor and generator? How can you change model type?
Q2: How does the model calculate miles per gallon? Which factors are considered to model fuel flow?
Q3: Run the HEV ReferenceApplication with WOT drive cycle. Change the grade and wind velocity in the environment block. Comment on the results.
Q4: Keeping all other parameters same, compare the simulated results of hybrid and pure electric powertrains.
Aim: To study the powertrain blockset and also comment results by making some changes.
A1: The difference between mapped and dynamic model of engine, motor and generator
Theory:
| Mapped model of engine | Dynamic model of engine |
| Model uses a set of steady-state lookup tables to characterize engine performance. | 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. |
| The tables provide overall engine characteristics, including actual torque, fuel flow rate, BSFC, and engine-out exhaust emissions. | If you need a more detailed dynamic model and have component-level data. |
| If you have engine data from a dynamometer or a design tool like GT-POWER. | To analyze the impact of individual engine components on the overall performance. |
| For quasi steady-state engine simulations. |
| Mapped | Dynamic |
| The Mapped Motor block implements a mapped motor and drive electronics operating in torque-control mode. | It contains, Interior PM controller, three phase voltage source inverter and internal permanent magnet synchronous machine(PMSM). All these combination gives EV dynamic. |
| The output torque tracks the torque reference demand and includes a motor-response and drive-response time constant. | Parameters of motor, current, electrical etc are given. |
| Maximmum torque, maximum power and time control time constant need to be given. | |
| Electric losses need to be specified if present. |
EV reference Application:
Opening and changing the model:
- Open EVreferenceapplication simulink model. The model contains drive cycle, driver, environmet conditions, controllers and passenger car. For results, open visualisation.
- Open passenger car subsystem and it contains drivetrain, electric plant input and output blocks.
- Open electric plant which contains motor, battery and other calculation blocks.
- Open motor block which contains both mapped and dynamic block systems.
- By default, mapped motor is selected.
- To change mapped to dynamic blockset, we need to right click on the screen and select variant.
- Then select Label Mode Active Choice. Then select MotGenEvDynamic.
Step by step process:
Results: These results were obtained when FTP75 drive cycle is used for simulation time of 2474 seconds. We can visulaise the values between any two intervals of time.
A2:
- Open EVreference application model. Under visualisation block we can see various blocks used for calculation.
- Open performance calculation block, which has vehicle speed and battery power as inputs.
- MPG is different from MPGe. MPGe means miles per gallon equivalent. MPGe is calculated in the model with the help of battery power and vehicle speed.
- Vehicle speed is multiplied itself and square rooted it. Then divided with time and converted m to mile.
- Then it is divided with gallon.
- Battery power is divided by 1000 and then divided with 33.7. Then it is converted to s per hour and then converted to m^3 per gal.
- The value is converted into gallon and used as MPG after dividing miles with gallon.
Blocks used for calculation:
Factors considered to model fuel flow:
- One gallon is equivalent to 33.7 kilwatt hours of electricity.
- Unlike mpg, the lower the kWh/100m number, the better.
- Adapting to this smaller-is-better figure is likely the roughest math most of us will face in relation to EVs.
- Vehicle speed and battery power are main factors of MPGe.
A3: Running the HEVReference Application and applying conditions as mentioned.
Hybrid Electric Vehicle Multimode Reference Application:
The hybrid electric vehicle reference application represents a full multimode hybrid electric vehicle (HEV) model with an internal combustion engine, transmission, battery, motor, generator, and associated powertrain control algorithms. Use the reference application for powertrain matching analysis and component selection, control and diagnostic algorithm design, and hardware-in-the-loop (HIL) testing.
By default, the HEV multimode reference application is configured with:
-
Mapped motor and generator
-
1.5–L spark-ignition (SI) dynamic engine
Diagram of HEV:
Description:
- Open HEVReference application.
- It contains various subsystems like environment, logitudinal driver, passenger car, visualisation etc.
- By default it is FTP75 drivecycle with 2474 seconds. Change it to the WOT drive cycle with WOT simulation time as 100 seconds.
- Now, run the application with 100 seconds.
Model:
Results:
- The current increases initially upto 500 and decreases at 18 seconds. It increases for some seconds and goes negative after 20 seconds.
- After 25 seconds, current becomes constant.
- The RPM increases and decreases upto 25 seconds. The peak RPM is around 8500.
- The battaery SOC decreases from 80 to 72. After 20 seconds there is a little amount of increase when engine works.
- Engine torque increases initially and goes negative after 20 seconds. The peak torque achieved is around 275.
- The fuel economy increases continuously upto 16.
HEV model with grade and wind velocity:
- Now, open environmet subsystem in the HEV reference application.
- Change the grade as 5 and wind velocity as 10.
Results:
- We can observe that, battery current increased upto around 500 and changes occurs upto 20 seconds.
- At 20 seconds, the current becomes negative. Battery current is same when compared with above condition.
- The RPM is positive and doesnt go to negative.
- Due to grade and wind velocity, the SOC decreases more due to more required power. It falls below 72 slightly less SOC than previous condition.
- Torque is same as previous condition.
- Due to HEV, the fuel economy increases only upto 10. This is less when compared with previous condition.
A4:
EVReferenceApplication:
- Open EVReferenceApplication.
- It consists of drive cycle, environment, logitudinal driver, controller, passenger car and visuals subsystem.
- Open the environment subsystem and change grade as 5 and wind velocity as 10.
- Run the simulation with 2474 seconds.
Model:
Results:
- First plot shows, the drive cycle.
- Second plot shows battery SOC. Soc falls from 80 to 42 for this drive cycle.
- Third plot shows motor speed.
- Fourth plot shows battery current. It changes continuously increases and decreases between 0 and 175.
- Fifth plot shows motor torque.
- Sixth plot shows fuel economy. Initially it increases upto 37 and after upto 41. It decreases and increases. It is almost constant at 40 after 750 seconds.
HEVReferenceApplication:
- Open HEVReferenceApplication.
- It consists of drive cycle, environment, logitudinal driver, controller, passenger car and visuals subsystem.
- Open the environment subsystem and change grade as 5 and wind velocity as 10.
- Run the simulation with 2474 seconds.
Results:
- First plot shows, the drive cycle.
- Second plot shows battery current. It increases and decreases continuously throughout the drive cycle.
- Third plot shows motor speed and engine speed.One speed is almost lower than other time.
- Fourth plot shows battery SOC. The battery decreases and increases throughout the drive cycle. When it reaches to 70% the engine produces power and the vehicle is run. It charges for some time upto 80% and continuously goes on throughout the drivecycle. During deceleration the battery charges.
- Fifth plot shows motor torque, engine torque and generator torque.
- Sixth plot shows fuel economy. Initially it increases upto 28 and maintains almost constant. It decreases and increases around 10. It is almost constant after 250 seconds.
Conclusion:
- Changes between mapped and dynamic engine, motor and generator are explained. Changing model is explained.
- Miles per gallon in model calculation is explained. Factors are explained.
- Observations are explained by running HEV ReferenceApplication model without grade and wind velocity and with grade and velocity.
- Compared HEV adn pure electric vehicle model and observations are done.
References:
https://in.mathworks.com/help/autoblks/ug/electric-vehicle-reference-application.html
https://in.mathworks.com/help/autoblks/getting-started-with-.html
https://en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equivalent