The importance of reliably detecting misfire in internal combustion engines is becoming more prominent. Misfiring cylinders increase emissions, decrease fuel economy, and can cause or be indicative of faulty or deteriorating mechanical condition, even possible impending catastrophic failure. Particularly on high cylinder count engines, a misfire is often not apparent to the operator. Even when an operator perceives that the engine is misfiring, the offending cylinder must still be identified for repairs.
Improvements in misfire detection methods are required to comply with evolving emission regulations, to maximize fuel economy, and to advance maintenance, service and production quality checks. Misfire detection approaches that measure crankshaft torsional vibration are popular, primarily because the hardware required is inexpensive and reliable. These approaches, however, are restricted to engines with a smaller number of cylinders and apply only to lower speed and load ranges. These limitations are inherent in existing torsional vibration based misfire detection schemes which assume non-overlapping firing pulses and rigid crankshafts. Neither of these assumptions are valid for high cylinder count engines and/or engines operating at high speed and load.
SDL has developed a misfire detection technology that is effective on small and large cylinder count engines over the entire speed and load range. The approach uses inexpensive and reliable sensors to measure torsional vibration at the crank nose and flywheel. Crankshaft flexibility and resonant dynamics are accommodated by utilizing a full dynamic torsional model of the engine. This approach traditionally has not been mathematically possible. |
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SDL, however, uses a patented approach that circumvents this mathematical limitation. Advanced digital signal processing is employed to achieve higher resolution torsional vibration signals and is being developed as a method of measuring cylinder pressure contributions in real-time.
The figure above shows the ability of the technology to detect partial misfires of a single cylinder. Each of the lines corresponds to the estimated combustion pressure of a cylinder, measured over five experimental conditions. Fueling to cylinder three was progressively reduced to simulate a misfire. The algorithm correctly estimated the reduction in pressure associated with cylinder three.
An additional problem with existing torsional based misfire detection algorithms is that they are sensitive to the loads applied to the engines. They must be manually tuned to particular engine/drive train configurations. SDL's misfire detection technology is robust and adaptively "learns" the model of the torsional dynamics. This results in a substantial reduction of the need to manually tune the algorithm for specific configurations.
Development and commercialization of this technology is being conducted by SDL with support from the U.S. Army Tank-Automotive and Armaments Command (TACOM).
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