Classical knock control strategies are still widely used in production vehicles but exist in several variant forms whose performance with respect to one another, and to engine efficiency, ease of calibration and analytical tractability has not been rigorously evaluated. This paper examines the absolute and relative performance of these strategies subject to both transient and systematic disturbances using both time history simulation methods and analytical methods. The former illustrates the response to specific instances of the knock process, while the latter enables the statistical properties of the closed loop response to be computed and compared.

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Individual instances of the knock resonant response are easy to acquire but these are subject to noise and vary considerably from cycle to cycle due to random variations in the knock process. This work provides a new way to quantify and model the stochastic properties of knock signals, capturing both the time domain resonant characteristics within a cycle as well as the random variations from cycle to cycle. A new phase alignment method enables the ensemble mean knock waveform to be identified from the data which also removes noise components without the need for narrowband filtering. This ensemble waveform shows the empirical characteristics of knock onset, decay, and frequency slurring within the cycle as the gas expands and cools. The phase-aligned cyclic variations of the knock waveform are also shown to approximate a (time-varying) dual-Gaussian distribution, and fitting such a model to the data enables the statistical properties of the dataset as a whole to be decomposed into separate knocking and non-knocking populations providing further insight into the knock process. The technique is applied both to filtered cylinder pressure signals and to accelerometer-based knock signals, and the results are compared and contrasted.

Introduction: Field transmission of pre-hospital ECG images to facilitate advance activation of the STEMI system of care has been shown to be effective in improving patient care and prognosis. Current commercial wireless ECG transmission systems available are effective, but are expensive to implement and maintain. Head to head testing was performed using an iPhone application to mediate ECG image transmission on three national cellular carriers in comparison to one commercial ECG transmission system. This resulted in comparable performance particularly in signal rich coverage environments contained three or greater bars. Hypothesis: An iPhone application that mediates pre-hospital ECG image transmission could be a cost effective alternative to current commercial systems incorporated in the pre-hospital STEMI system of care. Using a mobile phone signal booster could enhance application performance to consistently transmit in all signal coverage environments. Testing: The application was tested on three national cellular carriers with two commercial systems. Data was collected with and without the addition of the mobile phone signal booster at 75 waypoints covering the entire signal coverage environment. Application performance was determined by the average percentage of successful transmission and duration of transmission within the total signal coverage environment. Results: As shown in Figure 1, using the mobile phone signal booster resulted in marked improvements to successful transmission. Performance of the carriers under boosted conditions was merged, as the differences were not statistically significant enough to warrant differentiation. Within the signal-limited environment, the application displayed superior reliability to the two commercial systems, while in the signal rich environment it was comparable. Minimal improvement was also seen in the duration of transmission of the application, although it was more apparent within the signal limited environment than in the signal rich environment. Conclusion: The addition of the mobile phone signal booster enhances the performance of the iPhone application, allowing it to successfully transmit ECGs more consistently than commercial systems in all signal coverage environments.