Control-Oriented Knock Simulation

A comparative study of fixed-gain classical knock control strategies

“…The simulated knock events are therefore also binomially distributed with the same knock probability p as the experimental data, so the statistics of simulated knock events match those observed experimentally with a high degree of accuracy. 29 Finally, as shown in Figure 3, a unit cycle delay prevents ''algebraic loops'' in the simulation and models the fact that the knock status of an engine is derived from the prior combustion cycle.…”

“…For clarity, disturbance events are not shown in this case, though disturbances are considered in the stochastic analysis below. Results for the (disturbance-free) independent count strategy (28) are shown in red, while those for the count reset strategy (29) are shown in green. The standard advance-retard response is shown in blue for comparison.…”

“…An alternative and commonly used practice that can be applied to any engine, is simply to map these properties by recording the engine knock response across a range of steady state spark conditions. 29 This work is based on this approach and uses the same dataset analyzed and described in detail in Spelina et al 9 Data was recorded from a 5.4 L Ford V8 gasoline engine operated at 1000 rpm, full load, using 91 RON fuel. Each cylinder was instrumented with a cylinder pressure sensor, but the knock feedback signal was based solely on two accelerometer-type sensors (one on each bank of the engine).…”

“…This is because the binary classification of cycles into knocking or non-knocking events means that the knock event process must, by definition, conform to a binomial distribution – a fact confirmed by analyzing experimentally recorded knock event data. 29 The only variable in this process is then the spark-angle-dependent knock probability characteristic of the engine which is defined by the blue curve obtained in Figure 2. This curve can be embedded in a look-up table and used to obtain the prevailing knock probability p for any simulated spark advance condition, (see Figure 3).…”

A dual-threshold knock controller

“…A one-cycle engine delay also models the transport delay through the engine. Open-loop tests of the knock event simulator have shown that it replicates the statistical properties of the original data very accurately, 21 and this simulation tool has therefore been used to generate the results in the remainder of this article.…”