| 摘要 |
A demodulated audio signal for detection of engine-knock is digitalized to produce a sequence of digital signals corresponding to the various cylinders of the engine in turn. These digital signals are recursively filtered by applying a factor k to a newer value and its complement (1-k) to an older value from the same cylinder or a value obtained therefrom by partial filtering and the sum of the two factor-modified terms is formed to provide a reference value with which the most recent digital signal is compared, to produce an indication of engine-knock when the latter exceeds a reference value by a predetermined amount. The factor k is varied in accordance with acceleration of engine speed or with the level of signals from the vibration sensor that exists before the application of automatic gain control prior to integration. The system, which can be implemented mostly in the software of a microcomputer, also includes provisions for adjusting from time to time minimum reference signal values for each of the cylinders, which are to be substituted for the reference signal values contemporaneously produced by recursive filtering if the latter fail to exceed the former in magnitude, and also for determining, at appropriate times, failures of the knock detection system from the absence of normal variations between the integrated signals from the respective cylinders, and providing corrective action in response thereto. |
