Optimizing knock thresholds for improved knock control

Jones, James C. Peyton; Spelina, Jill M.; Frey, Jesse

doi:10.1177/1468087413482321

Cited by 26 publications

(12 citation statements)

References 16 publications

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“…As Peyton Jones et al shown in [26], weak knocking cycles detection would substantially improve knock control algorithms. Nevertheless, normal combustion can be confused with autoignition of a low thereshold is chosen.…”

Section: A New Knock Definition For Knock Detection and Control Optimmentioning

confidence: 95%

A new knock event definition for knock detection and control optimization

Bares

Selmanaj

Guardiola

et al. 2018

Applied Thermal Engineering

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In this paper, the knock phenomenon is studied and characterized by time-frequency analysis and a new definition that is capable of differentiating normal combustion from autoignition of the end gas, is proposed. The new definition permits detecting low-knocking cycles, and consequently, more knocking information is available for updating knock models or for improving knock control strategies. The new definition of knock is implemented online in a four stroke SI engine and its performance is illustrated by using a classical knock control strategy. Results obtained under different operating conditions demonstrate that the improved knock definition can substantially reduce the dispersion of Spark advance angle control and reach higher mean values, obtaining then, higher combustion efficiencies and reducing engine vibration.

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Section: A New Knock Definition For Knock Detection and Control Optimmentioning

confidence: 95%

A new knock event definition for knock detection and control optimization

Bares

Selmanaj

Guardiola

et al. 2018

Applied Thermal Engineering

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“…Indeed, it has recently been suggested that more informative feedback and better closed-loop performance may be obtained using a lower threshold than is typical. 26,27 By controlling the resultant “weak knock” rate, the probability of “strong” knock events is also controlled by default, since both are drawn from the same distribution.…”

Section: Properties Of the Knock Processmentioning

confidence: 99%

Stochastic simulation and analysis of a classical knock controller

Spelina

Jones

Frey

2014

International Journal of Engine Research

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Knock control remains a critical issue in modern engine powertrains, and a renewed emphasis on knock as a stochastic process has proved beneficial in the development of new controller designs. However, the random nature of knock also makes it hard to evaluate the closed-loop performance of a knock controller in a rigorous, repeatable way. This work therefore focuses particularly on the statistical properties of knock intensities and knock events, and a new Markovbased analysis is used to compute the corresponding statistical properties and distribution of the closed-loop response. The method is applied to a conventional knock controller, revealing new aspects of its behavior. In particular, the closedloop spark advance distribution is found to be periodic initially, only collapsing to an invariant steady-state distribution as a result of limits applied to the spark advance actuation. The stochastic response of the controller to different initial conditions is also investigated, providing a more rigorous insight into its performance. The results of the Markov-based analysis are confirmed using Monte Carlo simulations.

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“…Although a variety of measures have been proposed, the most common and widely used practice is to apply a threshold, such as that shown in Fig 3, and to control the rate or probability of knock events that exceed this threshold value. Recent work has argued that the threshold level can be optimized in order to maximize the information fed back to the controller, and that this can significantly improve closedloop performance, [24]. However, in this work, following typical practice, the threshold is set such that a small number of cycles (1%) classify as knocking at BorderLine (BL) knock conditions.…”

Section: Methodsmentioning

confidence: 99%

“…This strategy has a proven record for engine protection against engine damage but it operates at a mean spark advance which is significantly retarded relative to the desired BorderLine (BL) knock limit target, and therefore suffers some efficiency penalty. In a series of recent papers [20][21][22][23][24][25][26], the authors have advocated a new approach to knock control based on the fundamental binomial properties of knock events. Unlike the traditional controller which reacts deterministically to each knock event, the new controllers only adjust the spark when the statistical likelihood ratio of the observed knock events falls below some user-specified threshold.…”

mentioning

confidence: 99%

Experimental Validation of a Likelihood-Based Stochastic Knock Controller

Thomasson

Shi

Lindell

et al. 2016

IEEE Trans. Contr. Syst. Technol.

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Abstract-New likelihood-based stochastic knock controllers have the potential to deliver significantly improved regulatory response relative to conventional strategies, while also maintaining a rapid transient response, but evaluation studies to date have only been performed in simulation. In this paper an experimental validation of the new strategy is presented. To demonstrate the robustness of the method, the algorithm is implemented on two different engine platforms, using two different knock intensity metrics, and evaluated under different operating conditions. One of these platforms is a five cylinder variable compression ratio engine, enabling the controller to be tested under different compression ratios, as well as different speed and load conditions. The regulatory and transient performance of the likelihood-based controller is assessed in a back-to-back comparison with a conventional knock controller and it is shown that the new controller is able to operate closer to the knock limit with less variation in control action without increasing the risk of engine damage.

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Optimizing knock thresholds for improved knock control

Cited by 26 publications

References 16 publications

A new knock event definition for knock detection and control optimization

A new knock event definition for knock detection and control optimization

Stochastic simulation and analysis of a classical knock controller

Experimental Validation of a Likelihood-Based Stochastic Knock Controller

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