METHOD FOR PROVIDING A RELIABLE TIME SIGNAL

Abstract

A method for providing a reliable time signal. In the method, a first time signal from a first time source and a second time signal from a second time source are received and evaluated by an arrangement, the first time source and the second time source being independent of each other, the arrangement including a first unit in the arrangement which fulfills an observer and comparator function, the two time signals are compared with each other and a detected deviation between the two time signals is evaluated, and the reliable time signal is output on the basis of this evaluation.

Claims

1-10. (canceled)

11. A method for providing a reliable time signal, comprising the following steps: receiving and evaluating a first time signal from a first time source and a second time signal from a second time source, by an arrangement, the first time source and the second time source being independent of each other; comparing, by a first unit in the arrangement which carries out an observer and comparator function, the first and second time signals with each other; evaluating a detected deviation between the first and second time signals; and outputting the reliable time signal based on the evaluation.

12. The method as recited in claim 11, wherein an independent time base which is used in carrying out the observer and comparator function, is associated with the first unit.

13. The method as recited in claim 11, wherein the observer and comparator function is carried out cyclically.

14. The method as recited in claim 11, wherein a second unit is provided with which different formats of data carried by the first and second time signals are harmonized with each other.

15. The method as recited in claim 11, wherein a third unit is provided which, in the event that the comparison results in a deviation of the first and second time signals which lies outside a specified tolerance, triggers an error reaction.

16. The method as recited in claim 11, wherein a status signal is output dependent on the comparison.

17. The method as recited in claim 11, wherein a fourth unit is provided which is provided to detect freezing of at least one of the first and second time sources.

18. The method as recited in claim 11, wherein at least one of the first and second time signals is a GPS signal or a UTC signal.

19. The method as recited in claim 11, wherein the reliable time signal is provided in a vehicle.

20. An arrangement for providing a reliable time signal, the arrangement configured to: receive and evaluate a first time signal from a first time source and a second time signal from a second time source, by the arrangement, the first time source and the second time source being independent of each other; compare, by a first unit in the arrangement which carries out an observer and comparator function, the first and second time signals with each other; evaluate a detected deviation between the first and second time signals; and output the reliable time signal based on the evaluation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 shows a schematic illustration of a specific example embodiment of the arrangement for carrying out the presented method, according to the present invention.

[0035] FIG. 2 shows one possible sequence of the presented method in a flow diagram, according to the present invention.

[0036] FIG. 3 shows a further possible sequence of the presented method in a flow diagram, according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0037] The present invention is illustrated schematically in the figures with the aid of specific embodiments, and will be described extensively below with reference to the figures.

[0038] FIG. 1 shows a schematic illustration of a specific embodiment of the arrangement for carrying out the method described herein that is denoted overall by the reference numeral 10. The illustration furthermore symbolically shows a globe 12, to which a real universal time 14 which is transmitted once via satellites 16 and, independently thereof, via radio links 18 is transmitted. Thus there is a first time source 13 and a second time source 15, which are independent of each other. This results in a first time signal 22, in this case a GPS time signal, transmitted via a GPS receiver 20, and a second time signal 26, in this case a UTC time signal, transmitted via mobile phone networks, Wi-Fi, and comparable networks 24. The two time signals 22 and 26 are input variables of the arrangement 10.

[0039] The arrangement 10 carries out an observer and comparator function. This means that the arrangement observes or monitors, in particular cyclically, the two time signals 22, 26, or the information carried by the two time signals 22, 26, and compares them with each other. For this purpose, a first unit 30 is provided which compares the two time signals 22, 26 with each other and detects deviations, with tolerances being able to be taken into account. Since in this case the two time signals 22, 26, or the time values which they transmit, are present in different representations, a second unit 32 is provided which converts the time values to a common type of representation.

[0040] An absolute time indication can be represented in different ways. The UTC's Unix time stamp, which represents the current time as a numerical value of the seconds elapsed since Jan. 1, 1970, is widely used. A time indication may however also be stored, transmitted, or agreed in “human” form as “year-month-day-hour:minute:second”, in this case both as “text” or encoded by numbers in a data structure, or, as used in “GPS time”, as an indication of the weeks elapsed since Jan. 6, 1980 plus the “seconds of the current week” as numerical values.

[0041] Alternatively, any unambiguous definition whatsoever of one's own representation, e.g., “seconds since 1.1.2020”, may also be used. Furthermore, systematic, known deviations, for example in the form of the leap seconds, can be corrected at this point.

[0042] In the variant shown of the arrangement 30, furthermore a third independent time base 34 is provided, on the basis of which the observer and comparator function is executed. This separate time base is furthermore required in order to implement tolerance times, within which invalid deviations or the failure of one or both signals are/is briefly tolerated.

[0043] A third unit 36 triggers an error reaction 40 if detected deviations lie outside of predetermined tolerances. Furthermore, a status signal 42 is output dependent on the comparison.

[0044] Furthermore, a fourth unit 42 is provided which is provided for detecting in particular the freezing of the two time signals at a plausible pair of values 22, 26.

[0045] The first unit 30 then outputs the reliable time signal 46 dependent on the comparison of the two time signals 22, 26 which is carried out.

[0046] In principle, here, corresponding to the further use of the time indication, there may be strategies of different suitability, e.g., including the selection of the “most recent”, the “oldest” value, or a defined value between these, such as a weighted mean, arithmetic mean, etc. In the present case, only the time value of a signal source for which a greater availability and accuracy is expected in normal error-free operation is always used, as long as the deviation of the two signals lies within the tolerance. In the error case of a greater deviation, the last correct time value confirmed by the comparison is retained.

[0047] If both time values match sufficiently again within a short tolerated time interval, normal error-free operation is resumed, and the current time value is again provided.

[0048] Upon starting up, first of all a plurality of valid time values are verified before switching from a defined initial value, which is always invalid and incorrect, to the current time value. The associated status in so doing changes from “initial”/“invalid” to “valid”.

[0049] The described units 30, 32, 36, and 42 may be implemented as hardware modules in the arrangement, as pure software modules, or as hardware/software solutions.

[0050] FIG. 2 shows one possible sequence of the described method in a flow diagram. In a first step 50, an arrangement for carrying out the method receives a first time signal carrying a first time value, and a second time signal carrying a second time value. In a second step 52, the two time signals or time values are compared with each other. From the result of the comparison, and taking account of tolerances, in a third step 54 the reliable time signal is formed and output together with a status signal indicating the correctness status or error status. Additionally, in a fourth step 56 an error reaction is triggered once a tolerance time has elapsed.

[0051] The specific configuration of the output signals is typically dependent on the system design. In the present design, a time together with a separate status signal is always output by this safe time function. In alternative variants, it is possible to freeze the time, set it to an invalid value, or, upon the error reaction being triggered, to terminate the provision of the time, in which case a status may possibly no longer be necessary. If no separate status signal is used, the status may also be represented by special values of time (e.g., as an “invalid value”, time=“−1”, “−2”, etc.). It should be noted that in these cases the status is relayed implicitly by the status of the safe time (invalid value, or no time provided, here interpreted as status=“invalid”).

[0052] FIG. 3 shows a further possible sequence of the method presented, with in particular optional steps being emphasized in this case.

[0053] During an optional startup phase 70, in a first step 72, times are received. These are compared with each other in a second step 74. Then in a third step 76 the times are verified multiple times, and it is checked whether they are stable. If this is not the case, the variant returns (arrow 78) to the first step 72. If this is the case (arrow 80), the startup phase 70 ends and the method continues with a fourth step 82.

[0054] In this fourth step 82, times are received. In a fifth step 84, these times are compared with each other. If the comparison is successful and the times are within the tolerance (arrow 86), then in a sixth step 88 a reliable time is output. If the comparison in the fifth step 84 fails, or if the times are outside of the tolerance (arrow 90), then in an optional seventh step 92 a tolerance time is checked. If this is not exceeded (arrow 94), then there is a return to the fourth step 82. If the tolerance time is exceeded, then in an eighth step 96 there is a transition into a safe state.