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Technical Paper

IC Engine Retard Ignition Timing Limit Detection and Control using In-Cylinder Ionization Signal

2004-10-25
2004-01-2977
Internal combustion engines are designed to maximize power subject to meeting exhaust emission requirements and minimizing fuel consumption. However, the usable range of ignition timing is often limited by knock in the advance direction and by combustion instability (partial burn and misfire) in the retard direction. This paper details a retard limit management system utilizing ionization signals in order to maintain the desired combustion quality and prevent the occurrence of misfire without using fixed limits. In-cylinder ionization signals are processed to derive a metric for combustion quality and closeness of combustion to partial burn/misfire limit, which is used to provide a limiting value for the baseline ignition timing in the retard direction. For normal operations, this assures that the combustion variability is kept within an acceptable range.
Technical Paper

MBT Timing Detection and its Closed-Loop Control Using In-Cylinder Ionization Signal

2004-10-25
2004-01-2976
Maximum Brake Torque (MBT) timing for an internal combustion engine is the minimum advance of spark timing for best torque. Traditionally, MBT timing is an open loop feedforward control whose values are experimentally determined by conducting spark sweeps at different speed, load points and at different environmental operating conditions. Almost every calibration point needs a spark sweep to see if the engine can be operated at the MBT timing condition. If not, a certain degree of safety margin is needed to avoid pre-ignition or knock during engine operation. Open-loop spark mapping usually requires a tremendous amount of effort and time to achieve a satisfactory calibration. This paper shows that MBT timing can be achieved by regulating a composite feedback measure derived from the in-cylinder ionization signal referenced to a top dead center crank angle position. A PI (proportional and integral) controller is used to illustrate closed-loop control of MBT timing.
Technical Paper

Stochastic Limit Control and Its Application to Knock Limit Control Using Ionization Feedback

2005-04-11
2005-01-0018
Spark timing of an Internal Combustion (IC) engine is often limited by engine knock in the advanced direction. The ability to operate the engine at its advanced (borderline knock) spark limit is the key for improving output power and fuel economy. Due to combustion cycle-to-cycle variations, IC engine combustion behaves similar to a random process and so does the engine performance criteria, such as IMEP (Indicated Mean Effective Pressure), and knock intensity. The combustion stability measure COVariance of IMEP assumes the IMEP is a random process. Presently, the spark limit control of IC engines is deterministic in nature. The controller does not utilize any stochastic information associated with control parameters such as knock intensity for borderline spark limit control. This paper proposes a stochastic limit control strategy for borderline knock control. It also develops a simple stochastic model for evaluating the proposed stochastic controller.
Technical Paper

Closed Loop Maximum Dilution Limit Control using In-Cylinder Ionization Signal

2005-10-24
2005-01-3751
This paper presents a combustion stability index derived from an in-cylinder ionization signal to control the engine maximum EGR limit. Different from the existing approaches that use the ionization signal values to gauge how much EGR was added during the combustion, the proposed method concentrates on using the ionization signal duration and its stochastic properties to evaluate the end result of EGR on combustion stability. When the duration index or indexes are higher than pre-determined values, the EGR limit is set. The dynamometer engine test results have shown promise for closed loop EGR control of spark ignition engines.
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