Resampling of angle-synchronized signals to time domain for engine knocking calibration 2018-36-0136

In some engine measuring systems, the signal acquisition is synchronized with crank angle, rather than time. This technique is particularly beneficial when dealing with parameters such as incylinder pressure and other combustion analysis data that are closely linked to the engine working cycle. In such system, the crankshaft’s top dead center triggers the start of an acquisition with periods of varying time duration, which depends on engine speed [1]. However, there are scenarios where these very signals must be analyzed along with signals acquired with time synchronization. This is the case, for example, of engine knocking calibration, in which combustion data should be linked with injection, ignition, and other engine parameters, which are time-based. Moreover, most used signal processing algorithms are conceived for uniform sampling. In such scenarios, the angle-synchronized signals shall be resampled to a desired fixed frequency rate, i.e. despite of the varying time acquisition in the original signal, samples of the output signal should have equidistant intervals. This work presents a study on a resampling method for converting angle-synchronized signals to time domain, in order to enable proper data analysis and calibration. The interpolation methods are evaluated in terms of accuracy and use of computing resources. An example of resulting resampling method application is featured in a knocking calibration task.