1. Field
This invention relates to the rate based monitoring, for example for leak check monitoring for an internal combustion engine.
2. Background
Legislation relating to emissions control for motor vehicles such as automobiles includes requirements that various tests are performed on internal combustion engines and the systems associated therewith to monitor the correct operation of those engines and associated systems with the aim of providing a fault indication when a malfunction occurs that could lead to undesired emissions. A fault indication can be in the form, for example of a malfunction indicator lamp (MIL) being illuminated in the vehicle.
For some tests to be performed, the regulation specifies that tests should be performed at a given rate. The given rate is determined in terms of a numerator that is calculated as a measure of the number of times a vehicle has been operated such that all monitoring conditions necessary for a specific monitor to detect a malfunction have been encountered divided by a denominator that is representative of the number of times that a standard driving cycle having predetermined operating characteristics (also referred to as a “normal” driving cycle) has been performed.
Where a judgment of normal operation (i.e. non-failure operation) and a judgment of failure operation can be performed at a specific given time, then a rate based monitoring (RBM) numerator count can be updated when either failure or normal judgment is completed.
However if a timing of a judgment of normal operation and a judgment of a failure operation cannot be performed at a given timing, or if they take different times from starting a test procedure or if there are statistical variations that means that there is a spread of times at which judgment results are available, this methodology cannot be used. For example, in a conventional system, a judgment of normal operation may be made at a timing where it is not possible to detect failure with failed system, whereby an RBM numerator count cannot be updated.
Exemplary, non-limiting embodiments of the present invention seek to provide a reliable system for updating the RBM numerator count.