Project 2
Aim:- Modeling of development of a forward energy-based fuel consumption model of a P1 hybrid vehicle.
Objectives:-
1] Tabulate the fuel economy numbers (kmpl) for UDDS and HWFET cycle. Compare these numbers with the baseline numbers for conventional vehicle.
2] Plot the time trace for engine, transmission input, transmission output and wheel speed on one plot.
3] Plot engine torque, engine power, fuel rate and fuel consumption using subplots.
4] Plot accelerator and brake pedal, gear command, vehicle desired and actual speed, vehicle distance using subplots.
5] Plot the engine operating points on the engine fuel map.
6] Plot motor speed, torque, motor input power using subplots.
7] Plot pack voltage, current and SoC using subplots.
8] Plot the motor operating points on the motor input power map, with the motor max motoring and generating torque curves.
9] Generate the plots for UDDS and HWFET drive cycles.
Theory:-
P1 Mild Hybrid Electric Vehicle:-
The P1 architecture, with the electric machine connected directly to the crankshaft, is the solution adopted by Honda on their first generation Integrated Motor Assist (IMA) technology. The electric motor functions as a generator, during vehicle deceleration, as an engine starter, and as a motor (to assist the engine) during vehicle accelerations. One of the biggest advantage of this solution is that the electric motor can provide higher torque than the BiSG, since there is no belt limitation (due to slip). However, since there is no speed / torque ratio between the electric machine and crankshaft, the torque requirements on the electric motor can be quite demanding.
Two examples of P1 MHEV architectures are:
- Honda Insight Hybrid 2009 (with Integrated Motor Assist technology)
- Mercedes Benz S400 Bluehybrid 2010
For example, the main characteristics of the P1 MHEV.
1] ELectric Machine Performance:-
Maximum torque up to 34 Nm.
Maximum power: 10KW
Efficiency: Up to 94 Percent
2] Hybrid Modes:-
Idle stop and stop
Moving stop and start
Engine load shift
Torque assist
Torque boost
Energy recuperation
Brake generation
3] Advantages:-
Higher efficiency
The 12V starter can be removed
4] Disadvantages:-
Output torque limited by thje size of the elctric machine
Energy recuperation affected by engine friction losses
High impact on existing vehicle architecture
Higher overall cost of the electrical components
Air cooling not possible for electric machine
5] Overall charcteristics:-
Toruqe Boosting capacity: High
Electrical energy recuperation: Medium
Driveability improvements: Medium
Electrical Creep/drive: Possible
In this model We use Forward Model:-
It also known as dynamic simulation. Dynamic models are used for detailed simulations. In this model force/torque/power is the input and the vehicle state variable velocity and acceleration are outputs. The models and simulatios are more realistic due to phhysical casualty hence appropriate for control development. There is feedback loop to meet the desired vehicle state. It is mainly used to simulate a vehicle on a driving cycle to analyse the dynamic behaviour of the system helps significantly in control development.
Process:-
Load the Project2 folder as the Current Folder in Matlab.
Run the “Project2_InitFile.m” Matlab script.
The Drive cycle selection is done here.
Que:- Tabulate the fuel economy numbers (kmpl) for UDDS and HWFET cycle. Compare these numbers with the baseline numbers for conventional vehicle model from Project 1.
Answer:-
Fuel Economy Numbers for project 2
| S.No | Drive cycle | Fuel Economy Number (KMpl) |
| 1 | UDDS | 35.0352 |
| 2 | HWFET | 40.6827 |
As we see the fuel economy is high in HWFET compared to UDDS. It is because in urban driving the vehicle encounters more traffic and it has to stop for fever distance and it consumes more fuel at the starting. In HWFET the vehicle encounters no traffic and it moves without use of too much braking so it will have more fuel economy number.
Comparing with fuel economy numbers for project 1
| S.No | Drive cycle | Fuel Economy Number (KMpl) |
| 1 | UDDS | 14.209 |
| 2 | HWFET |
16.503 |
In this we can see the graph is more fluctuate into UDDS drive cycle compared to HWFET drive cycle. It is because UDDS has more starts and stops and in HWFET less starts and stops.
Braking is high in UDDS compared to HWFET.
Vehicle consumed more power in UDDS drive cycle because in urban area the vehicle require many starts and stops so it required more power compared to HWFET.
Engine is high in UDDS drive cycle compared to HWFET drive cycle because the starting from rest the vehicle requires more torque to overcome the static friction.
The fuel rate is high in HWFET drive cycle compared to UDDS drive cycle because it will be in continues movement so it consumes more fuel.
The fuel economy is high in HWFET because In UDDS cycle many starts and stops so more fuel cosumes and the engine is in idle position.
In UDDS The acceleratior and brake pedal have more fluctuations because of frequent starts and stops. but in HWFET the brake pedal fluctuations are almost near to the zero line as there will be no frequent stops.
In UDDS cycle mostly runs on 1st and 2nd gears and the 3rd and 4th gears are rarely useas it does not achieve high speed inn that traffic. In The HWFET cycle the vehicle mostly run in 3rd and 4th gears as it will moving at high speeds.
The fluctuations will be more in UDDS cycle compared to HWFET cycle because UDDS has many starts and stops due to traffic as the purpose of motor in P1 hybrid is initiation of crank rotation and they are more in UDDS cycle when compared to HWFET cycle.
If the purpose of the motor is to provide traction then both the cycles would have more fluctuations.
We can observe that the motor power and torque are very high in HWFET at the start and they are almost zero after few seconds but in UDDS it has continued fluctuations this is because of frequent braking in UDDS.
The pack voltage and current will have more fluctuations in UDDS as compared to HWFET cycle because of the frequent start and stops throughout the drive and the battery has to provide the energy everytime when the car is starting from the idle position.
SOC decreased in the UDDS cycle wrt time but it has increased in HWFET cycle. It is because in UDDS we have frequent start and stops and battery has to provide the energy everytime when the car is starting from the idle position and the SOC decreases but in HWFET cycle The Vehicle will be moving continuously without braking frequently and the generator is utilised to transfer some engine power to the battery through motor so SOC increase in the HWFET cycle.
Conclusion:-
The various performance of characteristics and operating points of UDDS drive cycle and HWFET drive cycle are analysed and the graphs are plotted
- Time trace for engine, Transmission input, Transmission output and wheelspeed with respect to time.
- Engine torque, Engine power, Fuel rate and Fuel consumption with respect to time.
- Accelerator and brake pedal, gear command and vehicle desired, actual speed, vehicle distance with respect to time.
- Engine operating points on the engine fuel map with respect to time.
- Motor speed, Torque, Motor input power with respect to time.
- Pack voltage, Current and State of charging with respect to time.
- The motor operating points on the motor input power map with respect to time.
and also it comparing with HWFET drive cycle and their numbers also compared.