Air-Fuel Ratio Control in Spark-Ignition Engines

1
Air-Fuel Ratio Control in Spark-Ignition Engines

• Presented to
• Dr. Riadh Habash, Fouad F. Khalil
• Presented by
• Ziad El Kayal, Hassan Fakih
• Umar Qureshi, Marc Topalian

2
How it Works

• Air and the fuel enter the carburetor, then
  through the engine and finally past a senor
• Using a sensor to measure the oxygen content of
  the engine's exhaust, the system keeps the
  fuel-air ratio very close to the proportion for
  chemically perfect combustion

3
References

• Air-Fuel Ratio Control in Spark-Ignition Engines
  Using Estimation Theory Chen-Fang Chang,
  Nicholas P. Fekete, Alois Amstutz, and J. David
  Powell
• Development of a Transient Air Fuel Controller
  for an Internal Combustion Engine Stewart P.
  Prince
• Digital Control of an Automobile Engine Air-Fuel
  Ratio System Martin J. Dubois, Robert P. Van
  Til, Nicholas G. Zorka
• Individual Cylinder Air-Fuel Ratio Control with
  a Single EGO Sensor Jessy W. Grizzle, Kelvin L.
  Dobbins, and Jeffrey A. Cook
• Design and Development of an ECU and its
  Air-Fuel Ratio Control Scheme Myomgho Sunwoo,
  Hansub Sim and Kangyune Lee

4
Requirements

• The controller must keep a fuel to air ratio of
  114.7 (0.068)
• The overshoot at the output must not be greater
  than 16.
• The settling time must be less than or equal to
  10 seconds.

5
Required Characteristic Equation

• From the IEEE article, the maximum overshoot
  required is 16 and the maximum settling time was
  10 seconds.
• Required Characteristic Equation
• s2 2wn?s 2wn
• Through calculation we found
• ? (damping factor) 0.5
• wn0.8 rad/s
• Therefore, set s equal to zero and find the
  poles, using the quadratic equation
• s1-0.4 0.4v3 i
• s2-0.4 - 0.4v3 i

6
Open Loop Transfer Function

• We needed to find a transfer function we could
  use to plot a root locus diagram
• We found the open loop transfer function of our
  block diagram to get the following formula
• (0.5t2Td 0.5t1Td)s Td
• T1t2s2 (t1 t2)s 1
• Using constants from IEEE references we were able
  to plot the following root locus diagram
• The diagram allowed us to find the roots and
  poles of the transfer function
• From the diagram we were able to design the lead
  compensator

7
Root Locust Diagram
8
Design of Lead Compensator

• Required Formula
• Gc(s) (sz) / (sp)
• The zero is found from the previous calculations,
  z 0.4
• Use Root Locus method to find the value of the
  pole.
• Draw straight lines from s1 to all the poles and
  zeros found on the root locus
• No need to use s2 because it is just a complex
  conjugate
• Find the angle at which the pole is located
• ?1 177 degrees
• ?2 50 degrees)
• ?3 5 degrees)
• ?4 1 degree
• ? 19 degrees
• Using ? -?1 -?2 -?3 -?4 -?d-180 degrees
•   ?d65 degrees
• Using this we were able to find the pole which we
  used to design our lead compensator
• Gc(s) (s0.4) / (s0.6)

9
Open Loop Transfer Function Diagram
10
Closed Loop Transfer Function Diagram
11
Simulink Design
12
Simulink Closed Loop Transfer Function Diagram
13
Conclusion

• Through research, we were able to design a
  controller to regulate the fuel to air ration in
  a spark-ignition engine with an overshoot of 11
  and a settling time of 10 seconds.
• We were able to accomplish the emission standards
  by adjusting the fuel to air ratio required by
  the IEEE paper.