WARF: P05046US
Control System for Internal Combustion Engines

INVENTORS

•

John Moskwa, John Lahti

Older internal combustion engines have valves that open and close at the same time during the engine cycle and were designed to be optimal over a specified speed range.  Outside of this range, fuel efficiency, emissions and power become unbalanced and suboptimal. Valve actuation systems that modify the valve position over the course of the engine cycle have been designed to attain better performance over a greater range of speeds.  However, greater freedom in valve actuation depends on knowledge of the correct mass air per cylinder (MAC) in order to provide the correct amounts of air and fuel to the combustion chamber.  Current methods to calculate MAC are difficult, time-consuming and based on incorrect assumptions.  A superior engine control system is needed to improve fuel economy, emissions and performance by providing real-time and accurate estimates of key engine parameters such as MAC. UW-Madison researchers have developed an engine control system that models and evaluates engine states in real-time, providing more precise control over performance, especially in engines with variable valve actuation. Key to the technology is a computationally efficient thermodynamic model of a cylinder, or “virtual cylinder,” which is implemented as part of the engine’s computer system. This model estimates the mass air per cylinder (MAC) for each actual cylinder at least a fraction of an engine cycle ahead of real-time operation (generally, 0.1 to 4 cycles ahead). This, in turn, allows real-time adjustments to fuel injection and other parameters, like spark advance, offering more precise engine control. Because the virtual cylinder model estimates MAC at the cylinder itself, these estimates may be more accurate than those achieved with traditional techniques that predict MAC at the throttle. The model also accounts directly for cylinder gas dynamics, rather than indirectly through volumetric efficiency (VE) corrections and other similar techniques. Moreover, because it models cylinders individually, the virtual cylinder approach allows the each cylinder’s fuel injection and spark to be set in accordance with its own MAC estimate, rather than an average MAC value for all cylinders.

• Thermodynamic and gas dynamic modeling of internal combustion engines
• Precise control of engines with variable valve actuation

• Promises improved fuel economy, lower emissions and better performance by providing real-time and potentially more accurate estimates of key engine parameters
• Requires fewer calibration tables than competing approaches, which reduces engine development time and possibly engine cost
• Models MAC for each cylinder individually, allowing each cylinder’s fuel injection and spark to be set in accordance with its own MAC estimate
• Because it accounts directly for cylinder gas dynamics, the model minimizes errors in MAC estimates that often occur under transient engine conditions.
• Measured engine parameters can be fed back to the virtual cylinder, enabling it to more accurately model actual engine states.
• In addition to intake parameters, model can calculate and control residual exhaust gas and, therefore, NO_X emissions.

For current licensing status, please contact our team at licensing@warf.org or phone 608.262.4924. (Clicking this link will open a contact form in a popup window. If you have problems viewing the form, try disabling your popup blocker software.)