The AKR 3 (Knock Control System) is based on the principle of the measurement of vibration transduced in the crankcase. This vibration is measured with Piezo sensors (knock sensors) which are attached to the crankcase and which convert the vibration into electrical signals. Analysis of these signals can be used to determine engine knock.
The AKR 3 uses digital signal processing to analyse signals caused by engine knocking.
Using digital signal processing offers two benefits compared to conventional analog systems:
it is possible to determine signals with a high degree of precision and the opportunity to monitor multiple signals (frequencies) caused by engine knocking simultaneously.
By using digital signal processing (DSP) the AKR 3 can very accurately determine which frequency is caused by engine knock and can thus influence the engine at the correct moment, i.e. only then when engine knocking really occurs.
Conventional knock control systems use analog filters to determine which frequencies are related to engine knock (ordinary bandpass filtering). With such systems it is difficult and expensive to determine the exact knocking frequency.
The poor filter gain characteristics of the analog filters used may cause other nearby frequencies to be detected as well. These other frequencies are not necessarily related to engine knock, however they would influence the operation of such systems; false detection of engine knock.
This reduces the efficiency of the engine needlessy.
Using DSP also offers the opportunity to analyse and process multiple signals caused by engine knocking. During engine analyses all crankcase vibration frequencies are being registered. These frequencies are then analysed and the most important frequencies caused by engine knocking are then programmed into the AKR 3, offering a highly improved control of engine knocking.
