Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle diagnosis or maintenance indication
Reexamination Certificate
2001-08-28
2003-04-29
Black, Thomas G. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle diagnosis or maintenance indication
C701S030000, C701S033000, C701S034000, C701S031000, C701S043000, C701S076000, C340S870030, C340S870030, C073S146500
Reexamination Certificate
active
06556900
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of storing information in the form of signals from a control system in a vehicle, counters being used to record on repeated occasions within which interval a signal is situated.
The invention also relates to a method, a device and a system for diagnosing errors and maintenance of vehicles.
TECHNICAL BACKGROUND
To handle the communication between various systems in a bus or a tram, it is known to use a system with a plurality of control or computer units which communicate via a communication channel (data bus). Each unit has a plurality of input and output terminals and wired logic to decide on available information at each separate moment and act accordingly. The system can receive information from a plurality of transducers, which generate signals representing different conditions in the vehicle, for instance, the temperature of the motor oil or if a door is open.
In order to diagnose the vehicle and detect errors, it is known to carry out an extensive analysis of the system at regular intervals, for instance, once a day. To carry out this analysis, a separate computer can be connected to one or more units of the control system and read the signals from one or more of the transducers in the system. This information gives a satisfactory on-the-spot account of the condition of the vehicle. For instance, information is provided concerning possible erroneous voltage levels which may be present in a component or a transducer.
If an analysis of this type suggests that a part of the different subsystems of the vehicle produces strange values or values indicating an error, the error may with any luck be rectified. It is, however, often necessary to carry out a more extensive analysis, in which measuring values from one or more transducers are measured and logged when driving for a whole day. When logging, the transducer signals are sampled and stored in a memory unit connected to the system.
In order to identify an error, it may be necessary to log several signals during the whole day. Since this results in very large quantities of data, they will be difficult to handle as concerns storage and communication, and therefore the measuring and analysis is a complicated and expensive process.
In order to store information from transducers in a storage-saving manner, it is known from U.S. Pat. No. 5,590,040 to use counters, which each represent an interval of the signal value of the transducer. The device according to this document determines to which value interval each sampling value belongs and increases the value of the counter in question.
One problem of this technique is that much information is lost. In principle, the counters can only reveal whether a measured value has once been located within an erroneous interval. Signal values which represent completely unphysical processes, i.e. processes which do not correspond to the physical reality and therefore indicate errors in, for instance, a component or a subsystem, may seem to be completely normal in such a limited representation, as long as they are situated within normal value intervals.
FIG. 1
shows how the method which is described in U.S. Pat. No. 5,590,040 generates substantially identical representations of two completely different series of measurements. The measuring signals in the series could, for instance, represent the number of revolutions or the temperature of the oil. In the first series (
FIG. 1
a
) an even increase of the voltage of the signal from 0 to 4 volt takes place. A division of the measured values into four intervals and an incrementation of counters associated with each interval would result in all four counters assuming substantially the same value since the signal has been situated for an approximately equally long period of time in each interval. In the second series, the signal is instead very unstable and fluctuates significantly during the increase (
FIG. 1
b
). On average, the distribution of measured values is, however, relatively even, and the signal is situated for an approximately equally long period of time in each interval. Thus, the values of the five counters would not differ materially from those of the counters recording the signal in
FIG. 1
a.
The series of measurements in
FIG. 1
b
could perfectly well indicate an error, for instance, in a transducer, a cord or the underlying physical process. This error is probably not detected using a method according to U.S. Pat. No. 5,590,040.
Furthermore, the device and the method according to U.S. Pat. No. 5,590,040 are primarily intended to reveal how an error occurred at the moment of occurrence. Thus, they cannot be used to prevent errors.
In systems of the above-mentioned type, an enormous quantity of data is, as already mentioned, available at each moment. It would be convenient if this information could be used with a view to preventing errors, instead of only indicating errors.
SUMMARY OF THE INVENTION
A first object of the present invention is to store data from a control system in a vehicle in a memory-saving manner.
A second object of the present invention is to store data in such manner that a sufficient amount of information is available for a satisfactory error detection and error diagnostics.
A third object of the present invention is to store data in such manner that a sufficient amount of information is available to prevent errors before they arise or at least detect an error before it has managed to attain such proportions so as to be of any practical relevance.
These and other objects are achieved by a method according to claim
1
. According to the method, use is made of change counters to record if a change in a signal value is greater than a defined change threshold value.
In this connection, change generally refers to the relation between a sampling value and previous sampling values. According to a preferred embodiment, the change consists of a difference between two sampling values and thus represents a derivative of the signal. It is, of course, also possible according to the method to use other change values, for instance, the divergence between two differences, which represents the second derivative of the signal.
By storing data according to the invention, a compact data set is provided, which contains great quantities of information about the condition of the system during a predetermined period of time. A data series of tens of thousands of values may be stored with a limited number of counters. Each counter only needs to handle integers, thus requiring little storage capacity.
Thus, the method according to the invention makes it possible to handle data in a fast and simple manner, said data representing large quantities of information about the condition of a vehicle during, for instance, a whole day. Therefore, information can be stored continuously in a vehicle without requiring extensive equipment.
Furthermore, the method of storing information, in which value interval counters and change counters are used, ensures that the information, in spite of its compact form, still contains a large amount of information. The structure in which the information is stored is also very well suited for analysis of the condition of the vehicle.
For instance, the physical process which a measuring signal represents can be determined to have a rate of change in time which is limited to a predetermined interval. According to the method, a change threshold value is associated which defines this predetermined interval with a counter. If this counter is incremented during a period, this immediately indicates that something is wrong. This may be due to a number of reasons, for instance, the facts that the transducer generates erroneous measuring signals, that there is a loose contact in a cord or that he physical process is disturbed. It is to be noted that the signal level in itself does not necessarily indicate an error, and therefore value interval counters would not alone be able to ensure that the error is detected.
In this connection, the word “error” does not only re
Birch & Stewart Kolasch & Birch, LLP
Black Thomas G.
Thoreb AB
To Tuan C
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