Project 2

AIM: The main goal of this project is to understand the functionality of a P1 hybrid and be able to model it.

OBJECTIVE:

• To analyse and understand the vehicle operating points in terms of engine speed, torque, transmission speeds, pedal positions, gear, distance travelled.
• 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.
• Plot the time trace for engine, transmission input, transmission output and wheel speed on one plot.
• Plot engine torque, engine power, fuel rate and fuel consumption using subplots.
• Plot accelerator and brake pedal, gear command, vehicle desired and actual speed, vehicle distance using subplots.
• Plot the engine operating points on the engine fuel map.
• Plot motor speed, torque, motor input power using subplots.
• Plot pack voltage, current and SoC using subplots.
• Plot the motor operating points on the motor input power map, with the motor max motoring and generating torque curves.
• Write down appropriate brief comments on each of these plots, describing the vehicle behaviour throughout the drive cycle.
• Generate the plots for both drive cycles.

Project:

The following file is to use with the and Simulink results for post-processing of the data.

In this project there are three steps to get the required plots using Matlab and Simulink:

• Initialization file in Matlab
• Simulink model for vehicle model
• Post-processing file in Matlab

The attached Matlab and Simulink model are executed to study the objectives.

These plots are plotted considering there is grade = 0 during the drive cycles.

• Tabulate the fuel economy numbers for UDDS and HWFET cycle.
  • Refer to attached spreadsheet which has fuel economy numbers for the above cycles.

• Honda Insight motor and battery are considered for this project. Data is taken from ADVISOR data base developed by NREL, USA. Data provided in the project files.

Motor	10 kW PMSM
Battery	6Ah 154V NiMH battery pack

• The Simulink model for this project consists of three main blocks viz. Driver, Controller and Powertrain.
  • Driver model: The acceleration and brake are simulated through pedal.
  • Controller is the brain of the vehicle where the decision making is taken based on different operating conditions of the vehicle. It consists of Engine control unit, Transmission control unit, Brake control unit and EM control unit. Based on the values of acceleration, brake, vehicle speed, SOC, clutch and engine speed , the mode of the vehicle is changed.
  • Powertrain consists of Engine, Electric motor, crank hub, transmission, Differential, wheel and vehicle dynamics. Since it is a P1 hybrid architecture, the powertrain is modelled as per below figure. In this architecture, torque from engine and electric motor combines and is transferred to crankhub. From there it is transferred to it next stages as shown.
  • Refer to Simulink model images shown below for more clarity.

Simulink model for P1 hybrid:

UDDS plots:

Observations from the UDDS plots:

• UDDS cycle represents city/urban driving conditions, where the Vehicle average speed is around 9 mph.
• The braking is very frequent in case of this cycle along with the acceleration.
• The engine torque, clutch and gears decide the input transmission speed. Depending on positive or negative torque the transmission output is decided. We can see from the plot the output transmission speed is less most of the time during the drive cycle. This is mainly attributed to the braking of the vehicle.
• The Engine is on only when the engine speed is greater than idle speed, hence we can see the engine torque is zero in the plot for certain time instances and here the motor torque is positive. This means at low speed the engine is off and electric motor is on.
• From the Time vs Gear plot shows that most of the time the vehicle is in 2nd gear due to city driving conditions.
• From the Motor torque vs time plot we can see in some of the time instances the torque is negative, this mean that regen braking is active and the SOC is increased (Battery charging mode). This can be visualized from the SOC plot.
• The voltage and pack current which are a part of ESS are also plotted.
• From the engine operating points on engine fuel map we can see that during the drive cycle the engine speed was between 550 to 3000 approximately. The Red line in the plot represents “Max torque curve” that the engine is designed to operate.
• The operating points represent the engine torque vs engine speed during the drive cycle. These are represented in black points.
• The contour lines in the plot represents the engine fuel consumption. For the operating points which are below the contour line 1 means the fuel consumption is in these areas is less than 1 g/s. Most of the remaining operating points are falling in between 1g/s to 2 g/s
• Plots for engine power, vehicle speed and fuel rate are also plotted against time to understand their trend.

HWFET plots:

Observations from HWFET plot:

• HWFET cycle represents a mixture of rural and interstate highway driving, where the Vehicle average speed is around 21 mph.
• The braking is less frequent in case of this cycle.
• The engine torque, clutch and gears decide the input transmission speed. Depending on positive or negative torque the transmission output is decided. We can see from the plot the output transmission speed is almost equal to input transmission speed most of the time during the drive cycle. This is mainly attributed to less braking of the vehicle. In some of the areas the output transmission speed is more than input, this is mainly attributed to the gear of the vehicle. The output speed is more in the 4^th gear and the braking is almost zero.
• The Engine is on only when the engine speed is greater than idle speed, the engine torque remained positive throughout the drive cycle because there was les braking. This means at high speed the engine is on and electric motor is off.
• From the Time vs Gear plot shows that most of the time the vehicle is in 3^rd and 4^th gear due to highway driving conditions.
• From the Motor torque vs time plot we can see in most of the time instances the torque is negative, this mean that some of the torque from the engine is also being fed to electric motor and there by the battery is being charged. The SOC of the battery is seen to be increasing throught out the drive cycle. This can be visualized from the SOC plot.
• The voltage and pack current which are a part of ESS are also plotted.
• From the engine operating points on engine fuel map we can see that during the drive cycle the engine speed was between 550 to 3000 approximately. The Red line in the plot represents “Max torque curve” that the engine is designed to operate.
• The operating points represent the engine torque vs engine speed during the drive cycle. These are represented in black points.
• The contour lines in the plot represents the engine fuel consumption. For the operating points which are below the contour line 1 means the fuel consumption is in these areas is less than 1 g/s. Most of the remaining operating points are falling in between 1g/s to 2 g/s
• Plots for engine power, vehicle speed and fuel rate are also plotted against time to understand their trend.

Conclusion:

Thus, the functionality of a P1 hybrid is analyzed.

The fuel economy numbers for the given vehicle on the urban cycle (UDDS) and highway cycle (HWFET) are compared.

The vehicle operating points in terms of engine speed, torque, transmission speeds, pedal positions, gear, electric motor torque are also analysed.