PhD Student Lars Eriksson. This project was initially performed in sole collaboration with Mecel AB from 1995 to 1997. In 1997 SAAB Automobile AB entered and the project is now participating in the ISIS competence center with the project Signal Interpretation and Control in Combustion Engines.

The spark plug can act both as actuator and sensor. When using the spark plug as sensor a DC-bias is applied to the gap and the current that goes through the circuit is measured, the current is called the ionization current. This project aims at controlling the spark advance using information deduced from the ionization current. Current ignition systems are based on precalibrated spark-advance tables that measure several parameters affecting the best spark advance setting. When the environmental conditions change the calibrated spark advance is no longer optimal. By continuously monitoring the combustion and updating the spark advance it can be held at optimum and increase engine efficiency.

We are studying a method for controlling the spark advance that is based on pattern recognition on the ionization current, in a fast inner loop. An idealized model of the ionization current, with six parameters, is fitted to the measured ionization current. Information extracted from the fitted model is then used to control the spark advance.

Feed-back control of the spark advance and disturbance rejection from the ionization current has been demonstrated. By injecting water into engine intake the combustion is slowed down and the optimal spark advance is increased. The feed back scheme senses the change in burn rate and adjusts the spark advance back to optimum. The combination of closed loop spark advance and water injection increased the engine efficiency with 2%.

Some more information about the project and the results is given in the project summary which summarize the project status and results. See below for a list of publications.

List of Publications

Licentiate Thesis

• Closed-Loop Spark-Advance Control using the Spark Plug as Ion Probe
  Lars Eriksson , 1997
  Linköping University, ISBN 91-7871-935-6, ISSN 0280-7971, LiU-TEK-LIC-1997:14, Thesis No. 613

Journal Papers

• An Ion-Sense Engine-Fine-Tuner
  Lars Nielsen and Lars Eriksson , 1998 , October
  IEEE Control Systems (special issue on powertrain control), vol. 18, no. 5, pages 43--52
• Ionization Current Interpretation for Ignition Control in Internal Combustion Engines
  Lars Eriksson and Lars Nielsen , 1997 , August
  IFAC Control Engineering Practice, Issue 8, Volume 5 , p.1107-1113
• Closed Loop Ignition Control by Ionization Current Interpretation
  Lars Eriksson, Lars Nielsen and Mikael Glavenius , 1997
  SAE SP-1236, SAE paper No. 970854, p.159--166

Conference Papers

• Requirements for and a Systematic Method for Identifying Heat-Release Model Parameters
  Lars Eriksson , 1998
  Modeling of SI and Diesel Engines, SP-1330, SAE Technical Paper no.980626 , 19--30
• Increasing the Efficiency of SI-Engines by Spark-Advance Control
  Lars Eriksson and Lars Nielsen , 1998
  IFAC Workshop -- Advances in Automotive Control (Preprints), 211-216
• Ignition Control by Ionization Current Interpretation
  Lars Eriksson, Lars Nielsen and Jan Nytomt , 1996
  SAE SP-1149, SAE paper No. 960045, p.73--79
• Ionization Current Interpretation for Ignition Control in Internal Combustion Engines
  Lars Nielsen and Lars Eriksson , 1996
  13'th World Congress of IFAC, Vol. Q, p.117-122

Departemental Reports

• A Real-Time Platform for Spark Advance Control
  Lars Eriksson , 1997
  LiTH-R-1938, ISSN 1400-3902, Linköping University, S-581 83 Linköping, Sweden, Department of Electrical Engineering
• Increasing the Efficiency of SI-Engines by Spark Advance Control and Water Injection
  Lars Eriksson , 1997
  LiTH-R-1939, ISSN 1400-3902, Linköping University, S-581 83 Linköping, Sweden, Department of Electrical Engineering