Vehicle modelling using Powertrain Blockset.

Aim:

To model Electric and Hybrid Electric vehicles using Powertrain blockset.

Objective:

1. What is the difference between the mapped and dynamic model of engine, motor, and generator? How can you change the model type? 
2. How does the model calculate miles per gallon? Which factors are considered to model fuel flow? 
3. Run the HEV ReferenceApplication with the WOT drive cycle. Change the grade and wind velocity in the environment block. Comment on the results.
4. Keeping all other parameters the same, compare the simulated results of hybrid and pure electric powertrains. 

Theory:

Powertrain Blockset:

Powertrain Blockset^™ provides fully assembled reference application models of automotive powertrains, including gasoline, diesel, hybrid, and electric systems. It includes a component library for simulating engine subsystems, transmission assemblies, traction motors, battery packs, and controller models. Powertrain Blockset also includes a dynamometer model for virtual testing. MDF file support provides a standards-based interface to calibration tools for data import.

Powertrain Blockset provides a standard model architecture that can be reused throughout the development process. You can use it for design tradeoff analysis and component sizing, control parameter optimization, and hardware-in-the-loop testing. You can customize models by parameterizing components in a reference application with your own data or by replacing a subsystem with your own model.

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

 Mapped Model:

• The mapped model is one type where the data points are pre-assigned in lookup tables.
• The engine or motor torque required is sensed and the motor or engine block generates the required torque output just as required simply without considering the real-time motor or engine, parameters.
• The output values are stored for the corresponding given input values of the engine. motor and generator.
• The accuracy of this type is not that high but the simulation will be done in much less time as it does not run by real-time parameters.

 Dynamic Model:

• The dynamic model on the other hand uses the combination of the outputs from various subsystems to generate the output.
• It runs by real-time simulation where the required input from the drive cycle is taken and for that individual real-time simulation gets performed and summing all the results of the subsystem gives the output for the simulation.
• As per the drive cycle requirements the initial Bus voltage, the current is given along with the vehicle feedback so that it runs the actual simulation at that particular moment throughout the drive cycle.
• The accuracy of this model is very high as it considers the real outputs from all the subsystem to generate the output.
• The simulation will take a very long time to complete as it has so many individual simulations running by all the subsystems of the engine, motor/generator.

Steps to select the Model Type:

1. In the powertrain blockset module, we first need to select the vehicle type first whether it is a full electric, full engine, or the type of hybrid vehicle.
2. After that, the Simulink model appears by showing the workflow blocks of the model.
3. In that, we need to go to Passenger Block → Electric plant → EV Motor/Generator block.
4. After this just right click and go to Variance → Label mode Active choice → MotorGenEV Mapped or Dynamic.

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

Miles per gallon:

• Miles per Gallon is a fuel economy rating determined by how far a car can travel on a gallon of petrol or Diesel for an Engine powered car.
• In the case of an electric vehicle, it tells us the energy which is equivalent to that of an engine-powered car to propel the car through a distance.
• The amount of Fuel Energy required to move an engine-powered car through a distance is determined and then it is compared to the equivalent amount of electric energy required to move the car through the same distance and is expressed as the miles per gallon.

Vehicle speed & Fuel flow:

• Vehicle speed is an important factor while considering the fuel consumption at that particular time, so to determine the fuel consumption throughout the drive cycle.
• To convert speed to Distance we can Integrate with time and we are doing the same of converting the velocity to get distance covered by integrating.
• Then the Fuel flow is expressed as the mass flow rate (i.e) the amount of fuel at each moment in Kg/Sec. Now integrating this will result in the mass of the fuel and by using this 1/(1000*0.739) we convert it to the volume and multiply by 1000 to get it in Litres.
• By comparing the two results we can get the amount of liter consumed to Run for 100km.

Battery Power:

• The amount of energy from battery power required to propel the vehicle Equivalent to that of the Engine is calculated here.
• The battery power is given in watts and it is converted to Kw by dividing with 1000.
• Then we convert the Energy from kWh to equivalent energy in US gallon of automotive gasoline by dividing with 33.7. since we get the energy in US Gallons equal in KWh we are trying to get the energy of equivalent US Gallons per seconds and we do this by dividing with 3600 and we convert the hour to seconds.
• Then multiplying with 0.00378541 we convert the US Gallons per sec to the volume of the fuel flow in (m^3/ s) and then we multiply with 739 (California Phase II Gasoline density) (i.e) m^3/s * kg/m^3 which gives the result as mass flow rate kg/s.
• Then finally the Battery energy equivalent in kg/s is given as an input for the fuel flow parameter in order to find the equivalent US Gallons energy and estimate the Miles per Gallons.

Calculating Miles per Gallon:

• The inputs from the vehicle speed (i.e) the Distance we found (in meters) are taken into the calculation and it is converted to the miles by multiplying with 0.000621371.
• Then the inputs from fuel flow (Battery energy + Fuel energy) taken in m^3 and are converted into equivalent US Gallons by multiplying with 264.172.
• Then the two inputs Miles covered and equivalent US Gallon are further divided and the result is got in Miles / Gallon.

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

• In the powertrain blockset we have selected the hybrid electric vehicle and this is the Simulink model.
• Here we can select the input parameters as we wish and we can run the simulation to check the results.

Simulation 1:

The simulation is done for a Hybrid electric vehicle with a Wide-open Throttle Drive cycle.

• The Total cycle time = 100 seconds.
• The Top speed of this cycle = 80 mph.
• Time to start deceleration = 50seconds.
• The Grade angle = 0 degrees.
• The wind velocity = 0 m/s.

Simulation 2:

The simulation is done for a Hybrid electric vehicle with a Wide-open Throttle Drive cycle.

• The Total cycle time = 100 seconds.
• The Top speed of this cycle = 80 mph.
• Time to start deceleration = 50seconds.
• The Grade angle = 8 Degrees.
• The wind velocity = 10 m/s.

Results:

• In all the results we can observe some changes from simulation 1.
• The vehicle parameters and the drive cycle are the same, but we have made some changes in the environment blocks by adding some hill climb angles and wind velocity.

Observation:

• The simulation results for both the cases are found and we can see that the simulation 1 without the inclusion of hill-climbing conditions and the wind drag velocity is much more efficient when compared to the simulation which includes the hill-climbing conditions and the wind drag velocity.
• The vehicle was not able to achieve the required top speed though using the highest possible current discharge of that same battery used before.
• The state of charge also shows that the discharge is also high compared to simulation 1.
• The Fuel Economy is also down to half of the simulation 1.
• Therefore, it is evident that the efficiency of the no-load vehicle is high compared to the vehicle with additional loads acting on them.

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

We considered the default FTP75 drive cycle for 2474 seconds for both simulations.

Hybrid Electric Vehicle:

• A hybrid electric vehicle (HEV) is a type of hybrid type that combines a conventional Internal combustion engine (ICE) system with an electric propulsion system.
• The presence of the electric powertrain is intended to achieve either better fuel economy than a conventional vehicle or better performance.
• An example of HEV is the Toyota Prius.

Pure Electric Vehicle:

• A battery-electric vehicle or pure Electric vehicle is an EV that exclusively uses chemical energy stored in rechargeable battery packs with no secondary source of propulsion (e.g. hydrogen fuel cell, internal combustion engine, etc.) of energy.
• BEVs use electric motors and motor controllers instead of conventional Internal combustion engines for propulsion. They derive all power from battery packs.
• So they don't produce any emission of waste gas and they are eco friendly.
• They also have their own limitations such as range etc.
• An example of Pure EV is Nissan Leaf.

Observation:

1. The electric vehicle when compared with hybrid electric vehicles with the same environmental and Drive cycle conditions results in less top speed achievement.

• The electric vehicle produces more values of Motor speed and motor torque compared to the hybrid vehicle's motor alone, but hybrid vehicle when it combines the torque of both motor and it's the engine it is higher than the electric vehicle's torque.
• This is responsible to pull the Hybrid car at higher top speed compared to the pure electric.

2. As the pure electric car here uses Lithium-ion battery compared to the Nickel-metal hydride battery the discharging capacity and the rate of charging are higher in the pure electric car.

• As it is able to discharge at a fast rate the motor can produce a high amount of torque instantly compared to the hybrid vehicle.
• Also, the state of charge shows the battery efficiency of the pure electric to be higher than the hybrid vehicle and this is also due to the battery type used in these cars.

3. The efficiency of the Electric car is higher than the hybrid car which is evident from the miles per gallon numbers of both of these cars.
4. The electric vehicle produces zero emissions whereas the hybrid ones produce waste gas emission.

Conclusion:

Thus, we have successfully simulated the objectives with the help of Powertrain blockset in MATLAB.