DE102008036437A1 - Method for determining the service life of a hazard detector and hazard detector - Google Patents

Abstract

The method involves determining a filtered signal (2) of measurement- or operation value (1) of a danger warning system i.e. fire alarm, by exponentially filtering first and second orders with filter parameters, and weighted summing of results from filtering the first and second orders. A momentary increase of the filtered signal is determined from the filter parameters and another filter parameter. Information about time period until exceeding or falling below a predetermined reference value through the filtered signal is determined by increasing the filtered signal. An independent claim is also included for a danger warning system including a signal processing device.

Description

The The invention relates to a method for operating a hazard detector in particular a scattered light fire detector with at least one sensor, which detector provided with at least one signal processing unit is, by means of which of the temporal development of measured values the sensor or operating data of the detector information about its remaining operating time is gained. Moreover, the invention relates a hazard detector, in particular for carrying out the aforementioned method.

Alarm Devices, including stray light fire alarms, are now being distributed, for example in building surveillance, used and are in many applications of an adverse environment in the form of dust exposed, for example, inside of a stray light fire detector settles on the walls of the measuring chamber.

This leads there to an increased Reflection of the light emitted for the smoke measurement on just this walls and thus to an increase of the basic signal. Under basic signal is the signal of a smoke detector to understand that is measured in smoke-free air. About the Operating time of the fire detector increases due to the increasing Pollution the ground signal in progress. The so-called alarm threshold, in which the alarm is triggered by the fire detector, must therefore be parallel in the signal processing unit by a in usually constant value can be increased to false alarms to avoid. For this tracking However, the alarm threshold has a physical upper limit, for example, from the linearity of the measurement signal or the resolution of the analog-to-digital converter of the signal processing unit. As soon as the distance between basic signal and alarm threshold is not more constant by a tracking the annunciator indicates an error and should be exchanged become.

Ideally should a detector be permanent or at least at the time of its maintenance calculate and spend the duration until the fault is reached. The operator or service technician can use this information decide whether the detector will survive the time until the next maintenance or test or should be replaced prematurely. Thus, the occurrence of pollution-related disorders diminished or unnecessary Exchange can be avoided, resulting in a cost savings.

The really unlikely would be Case of a constantly increasing pollution, it would be possible from the quotient of the difference between an older value z. B. the starting value of the detector and the current value and the in between lying operating time calculate the slope of the basic signal. from that could in principle the still available standing time until the fault occurs. In the In practice, however, the environmental conditions will change over the course of Changing time again and again, z. B. by reacting the detector or changing the use of the relevant Room (carpet or parquet, warehouse or office, air conditioning, craftsmanship Etc.). A pollution forecast as described above would become a variable Increase or decrease in dustiness but do not take into account and give too high or too low values. This great uncertainty makes such a prognosis pointless.

Independent of the history would let determine with knowledge of the current slope of the fundamental signal about that, even with an already high basic signal, but a very low slope, still expected to have a long service life is. On the other hand could even a low fundamental signal with a rapid increase a fault even before the next Maintain maintenance. For the Calculation of the current slope according to the methodology presented above must have resorted to at least one sufficiently long ago data value to compensate for short-term fluctuations. In addition, one must Variety of measured values between the sufficiently distant past Data value and current reading for future slope calculations get saved. However, this places high demands on the size of the internal Latch of the signal processing device and its internal Control software, so the firmware, and therefore finds in practice no use.

It is therefore the object of the present invention, a method to provide for the operation of a hazard detector, which at Reliable statement about the remaining operating time of the fire alarm when changing Operating conditions made light and thus allows a cost-reduced operation.

• a) Ermittlung eines geglätteten Signals G_t der Mess- oder Betriebswerte g_t mittels exponentieller Glättung erster und zweiter Ordnung mit Glättungsparametern α und β und Gewichtung der Ergebnisse g_t* aus der Glättung erster Ordnung und g_t** der Glättung zweiter Ordnung;
• b) Bestimmung der momentanen Steigung Ġ_t des geglätteten Signals G_t aus g_t*, g_t** und einem Glättungsparameter γ;
• c) Ermittlung der Information über die Zeitdauer bis zum vermutlichen Über- oder Unterschreiten einer vorbestimmbaren Schwelle durch das geglättete Signal G_t mittels der Steigung Ġ_t und gegebenenfalls deren Ausgabe als restliche Betriebsdauer oder Störung;

This initially contradictory object is achieved by a method which has at least partially the following method steps:

• a) Determination of a smoothed signal G _{t of} the measured or operating values g _t by means of exponential smoothing of first and second order with smoothing parameters α and β and weighting of the results g _t * from the First order smoothing and g _t ** second order smoothing;
• b) determining the instantaneous slope Ġ _{t of} the smoothed signal G _t from g _t *, g _t ** and a smoothing parameter γ;
• c) determination of the information about the time until the presumable exceeding or falling below a predeterminable threshold by the smoothed signal G _t by means of the slope Ġ _t and, if appropriate, their output as the remaining operating time or fault;

• a) Vorgabe wenigstens eines Glättungsparameters α, β und γ;
• b) Ermittlung einiger Messwerte g des Sensors, Bestimmung eines Startwertes g₀ für einen Zeitpunkt t = 0 aus der Mittelung dieser Messwerte g zu einem bestimmten Zeitpunkt, Verwendung des Mittelwerts als Funktionswert g₀* zu diesem Zeitpunkt;
• c) Ermittlung des Mess- oder Betriebswertes g_t zu einem nach t = 0 liegenden Zeitpunkt t;
• d) Exponentielle Glättung des Mess- oder Betriebswerts g_t zum geglätteten Wert g_t* Bildung der gewichteten Summe von g_t und dem Ergebnis einer vorangegangenen Glättung g_t-1* sowie dem Glättungsparameter α;
• e) Exponentielle Glättung von g_t* zum geglätteten Wert zweiter Ordnung g_t** durch Bildung der gewichteten Summe von g_t* und dem Ergebnis einer vorangegangenen Glättung zweiter Ordnung g_t-1**, sowie dem Glättungsparameter β;
• f) Ermittlung eines geglätteten (Grund-)Signals G_t aus einer gewichteten Summe von g_t* und g_t**;
• g) Bestimmung der momentanen Steigung Ġ_t des geglätteten (Grund-)Signals G_t;
• h) Ermittlung der Information über die Zeitdauer bis zum vermutlichen Über- oder Unterschreiten einer vorbestimmbaren Schwelle durch das geglättete Signal G_t mittels der Steigung Ġ_t und gegebenenfalls deren Ausgabe als restliche Betriebszeit oder Störung;
• i) Wiederholung der Verfahrensschritte c) bis h) zu Zeitpunkten t + 1, t + 2, ..., t + n.

A preferred variant of the method uses, in addition to the abovementioned method steps, additional method steps. This preferred variant has at least partially the following method steps:

• a) specification of at least one smoothing parameter α, β and γ;
• b) determination of some measured values g of the sensor, determination of a starting value g ₀ for a time t = 0 from the averaging of these measured values g at a specific time, use of the mean value as a function value g ₀ * at this time;
• c) determination of the measured or operating value g _t at a time t after t = 0;
• d) exponential smoothing of the measured or operating value g _t to the smoothed value g _t * formation of the weighted sum of g _t and the result of a previous smoothing g _t-1 * and the smoothing parameter α;
• e) exponential smoothing of g _t * to the smoothed value of second order g _t ** by forming the weighted sum of g _t * and the result of a previous smoothing second order g _t-1 **, as well as the smoothing parameter β;
• f) determining a smoothed (fundamental) signal G _t from a weighted sum of g _t * and g _t **;
• g) determining the instantaneous slope Ġ _{t of} the smoothed (fundamental) signal G _t ;
• h) determination of the information about the time duration until the presumable exceeding or falling below a predeterminable threshold by the smoothed signal G _t by means of the slope Ġ _t and, if appropriate, their output as the remaining operating time or fault;
• i) repetition of the method steps c) to h) at times t + 1, t + 2, ..., t + n.

The Thus, the method is based inter alia on the fact that at least a smoothing factor the influence of older ones Data values to the current value is determined. The smaller the or the smoothing values, the stronger is the influence of past data and the stronger it is the smoothing. The smoothed Value follows for trend changes the original one Value with a time interval. Nevertheless, you can recognize trends in a timely manner to be able to a second exponential smoothing takes place (exponential smoothing second Order) of the simply smoothed ones Values and a weighted offsetting of both values from first and second order with each other. The new data value contains clearly less fluctuations than the raw data, but follows trend changes faster than just once or twice smoothed values. The smoothing value Also determines the speed of adjustment here. Farther let yourself calculate the slope of the smoothed curve at the same time. Also here or the smoothing factors affect how fast the slope calculation follows the short-term curve.

The Method of exponential smoothing So first and second order can both be used to the values of a measured signal or other operating data such as To smooth the energy consumption of a hazard detector, ie short-term fluctuations to remove, as well as at the same time a prognosis over the Time to reach a certain, the operating time of the detector to create a limiting threshold, such as B of the degree of contamination or the rest of an energy store removable energy.

The basic signal to be measured and / or the corresponding operating data g _t are recorded at times t or in each case after the lapse of a corresponding time interval Δt. To smooth or dampen rapid fluctuations or signal increases, the smoothing parameters α, β and γ must be selected to be small. In this case, 0 <α <1, 0 <β <1 and 0 <γ <1, where as a rule, though not exclusively, α = β = γ holds.

The smoothed basic signal or the smoothed operating data G _{t are} calculated according to G t * = α · g t + (1-α) · g t-1 * (exponential smoothing of the first order), G t ** = β · g t * + (1-β) · g t-1 ** (exponential smoothing of second order) such as G t = 2 · g t * - g t ** (weighted sum), where t - 1 is t - Δt.

The slope Ġ _{t of} the smoothed curve G _t at time t is calculated according to G t = m 1 = γ 1 - γ ·(G t * - g t **)

woraus sich die Steigung m_t zu mt = γ·(gt* – gt**)ergibt.The following simplifications or estimates can be made with γ = 1 / A:

hence the slope m to _t m t = γ · (g t * - g t **) results.

If a linear curve is assumed in the future, it is possible to calculate the time t _v , at which a defined signal height or a defined operating data value g _v , will be achieved. It must be assumed that the smoothed value G _t to compensate for short-term signal fluctuations, for example by dust particles or consumption peaks or the like, even if G _t may differ due to the strong attenuation of the actual measurement or operating data g _t .

lässt sich der Zeitpunkt t_v zu

bestimmen.With

the time t _v can be

determine.

aus welchem sich die tatsächlich verbleibende Zeit durch Multiplikation mit dem Messintervall Δt (bspw. 60 Sekunden) zu TC = tc·Δtergibt.In practice, the determination of a so-called countdown value t _c until the occurrence of the disturbance by z. As pollution or lack of energy

from which the actual remaining time increases by multiplication with the measuring interval Δt (for example 60 seconds) T C = t c · .DELTA.t results.

at suitable choice of the smoothing value can so temporary Variations of the basic signal or the operating data, the z. B. by dust particles during construction or consumption peaks frequent testing be filtered out. The mode of action corresponds then about a moving averaging over a variety of measurements, the one area in the order of magnitude cover of several days.

The described method thus solves the above-described problem: the basic signal or an operating data sequence is smoothed. At the same time, the current slope of the basic signal or of the operating data sequence can be determined at any time and thus a fault prognosis can be created, for which at a Va From the weighted averages of g _t * and g _t ** a prediction value g _{t + r} ^{P is determined} for a future time t + r.

In a likewise expedient variant of the method, only the computationally determined, simply smoothed value g _t * and the twice smoothed value g _t ** are stored in a storage means for further use after a measurement and stand after the time Δt as values g _t-1 * and g _t-1 ** are available, because smoothing and forecasting, unlike other methods, do not need to save any data other than the previous one. This saves internal storage space. Since, in terms of the method, only two old data values have to be stored in memory per signal or data sequence, the exponential smoothing is particularly suitable for use in signal processing devices provided with microcontrollers.

In order to avoid the problem of a division by too large integer numbers in the signal processing device, a variant of the method may consist in that an offset g ^{0 is} subtracted from the respective measured value g _t , so that in the case of an analog-digital Conversion no information is lost.

In a further variant of the method, after each measurement, the slope value Ġ _t determined in method step b) or g) is compared with a predefinable value stored in a memory element. By calculating the current slope, it is then possible to check whether the maximum permitted slope of the signal tracking is exceeded by the standards. In this case, measures such as increasing the damping or stopping the tracking can be taken.

The object is also achieved by a fire detector in which the signal processing device is associated with a microcontroller, the successive measured values g _t at least one sensor and / or operating data of the fire detector of a multiple exponential smoothing and generates information about the remaining service life of the fire detector and optionally outputs ,

Further advantageous embodiments the fire detector according to the invention emerge from the dependent claims.

The The invention is explained below with reference to figures in the drawing. there show the

1 a diagram with a curve of measuring points and a smoothed curve;

2 a diagram with the smoothed curve from the 1 with gradients at different times;

3 - 5 various examples of digital filters for smoothing the respective measured values to the smoothed fundamental signal and for determining a prognosis value.

In the 1 is a diagram showing a possible development of a smoke detector measuring signal, wherein first the measured signal g _{t of} a fire detector is plotted point by point in arbitrary units over time t. Due to the large number of measured points after predetermined time intervals, the individual points are only to be resolved here if they stand out markedly from the other curve as outliers. The smoothed basic signal G _t determined from the measuring points is laid as a white curve over the multiplicity of measuring points, whereby it can be seen that the smoothed values G _t slightly follow the actual values due to the double exponential smoothing, but otherwise the trend is very good is shown. Next is in the diagram of 1 to recognize a horizontal, dashed line, which represents the maximum allowable fundamental signal to which a fixed amount can be added to the continuous pollution rising, smoothed fundamental signal G _t . The time indicated by the vertical dashed line at which the measured and smoothed signals reach this threshold substantially simultaneously forms the instant at which the detector must be replaced and which is determinable by calculating the slope of the smoothed fundamental.

In the 2 the measured signal g _{t is} omitted in the diagram and only the smoothed fundamental signal G _{t is} plotted over time. At the same time, two dash-dotted lines show slopes of this smoothed fundamental signal at different times. It can be seen here that in a time range of approximately 5000 (arbitrary) units, the slope of the smoothed signal initially indicates a shorter expected life of the fire detector until it is replaced. Due to the later signalent However, the gradient of the smoothed fundamental signal G _{t changes} and a correct prognosis about the time of the probable replacement of the detector is possible.

In the 1 and 2 By way of example, the effect of the above-described smoothing on the measurement signal of a scattered light smoke detector and the application of the inventive method to this signal has been shown. However, it is also conceivable that the method is based on an operating data sequence of parameters such. B. the energy consumption or the content of an energy storage, which serves to power the detector to apply, which have as well as the pollution of the measuring chamber of a stray light fire detector effects on the remaining service life of the detector.

In the 3 to 5 are various, the microcontroller of the fire detector associated digital filter structures is Darge provides, which can be implemented in software or hardware and apply in each case based on the measured signal or the operating data g _t to this various filter operations, so that through the structure of the 3 the simply smoothed value g _t *, by the structure of the 4 the doubly smoothed value g _t ** and finally the structure of 5 the smoothed basic signal or the smoothed operating data sequence G _t can be generated at a time t.

In the 3 to 5 represent the triangles multipliers, the input signal z. G _t , g _t * or g _t-1 * multiply by the factor next to it. The elements marked "+" are adders which sum the input signals coming from the left, top and bottom and output the sum of these signals as the output signal on the right. The elements labeled "T" represent timers which as memory means are the values g _t * and g _t ** applied to their input and at their output the respective values of the preceding instant t-1 as g _t-1 * and g _{t -1} ** ready.

Claims (14)

Method for operating a hazard detector with at least one sensor, which detector is provided with at least one signal processing unit, by means of which information about its remaining operating time is obtained from the development over time of measured values g _{t of} the sensor or operating values of the detector, characterized at least by the following method steps a) Determination of a smoothed signal G _{t of} the measured or operating values g _t by means of exponential smoothing of the first and second order with smoothing parameters α and β and weighting of the results g _t * of the first-order smoothing and g _t ** of the second-order smoothing ; b) determining the instantaneous slope Ġ _{t of} the smoothed signal G _t from g _t *, g _t ** and a smoothing parameter γ; c) determination of the information about the time until the presumable exceeding or falling below a predeterminable threshold by the smoothed signal G _t by means of the slope Ġ _t and, if appropriate, their output as the remaining operating time or fault; Method for operating a hazard detector with at least one sensor, which detector is provided with at least one signal processing unit, by means of which information about its remaining operating time is obtained from the development over time of measured values g _{t of} the sensor or operating values of the detector, characterized at least by the following method steps : a) specification of at least one smoothing parameter α, β and / or γ; b) determining a starting value g ₀ for a time t = 0; c) determination of the measured or operating value g _t at a time t after t = 0; d) exponential smoothing of the measured or operating value g _t to the smoothed value g _t * by forming the weighted sum of g _t and the result of a previous smoothing g _t-1 * and the smoothing parameter α; e) exponential smoothing of g _t * to the smoothed second order value g _t ** by forming the weighted sum of g _t * and the result of a previous second order smoothing g _t-1 ** and the smoothing parameter β; f) determining a smoothed signal G _t from a weighted sum of g _t * and g _t **; g) determining the instantaneous slope Ġ _{t of} the smoothed signal G _t from g _t *, g _t ** and the smoothing parameter γ; h) determination of the information about the time until the presumed exceeding or falling below a predeterminable threshold by the smoothed signal G _t by means of the slope Ġ _t and, where appropriate, their output as the remaining operating time or disorder; i) repetition of the method steps c) to h) at times t + 1, t + 2, ..., t + n. A method according to claim 1 or 2, characterized in that the hazard detector is a smoke detector with a scattered light smoke sensor, and that are used as measured values g _t the measured values of the smoke sensor. Method according to Claim 1 or 2, characterized in that voltage values of an energy store and / or energy consumption values of the detector and / or the remaining energy content of a store are used as operating values g _t . Method according to one or more of claims 1 to 4, characterized in that from the weighted averages g _t * and g _t ** a forecast value g _{t + r} ^{P is determined} for a future time t + r. Method according to one of claims 1 to 5, characterized that information about the remaining service life of the fire detector by a time or a period of time becomes. Method according to one of Claims 3 to 6, characterized in that the smoothed signal G _t determined at the respective instant t is interpreted as a basic signal and an alarm threshold of the fire detector is determined by adding a fixed value. Method according to one of the preceding claims, characterized in that, after each measurement, the slope value Ġ _t determined in method step b) or g) is compared with a predefinable value stored in a memory element. Method according to one of the preceding claims, characterized in that after a measurement only the mathematically determined, singly and doubly smoothed values g _t * and g _t ** are stored in a storage means for further use. Hazard detectors, in particular fire detectors for carrying out the Method according to one of the preceding claims, comprising a signal processing device is provided, which in turn is assigned to a microcontroller, characterized in that the microcontroller has a present Measured value of at least one sensor or operating data of the fire detector a multiple exponential smoothing and an information generated to the operating life of the fire detector and optionally outputs. Hazard detector, in particular fire detector according to claim 10, characterized in that the microcontroller the instantaneous Slope of the smoothed Signals determined. Hazard detector, in particular fire detector according to claim 10 or 11, characterized in that the microcontroller the smoothed one Signal as well as a defined or possibly further measured values Sensors influence the value of an alarm threshold of the fire detector generated. Hazard detectors, especially fire detectors after one the claims 10 to 12, characterized in that the microcontroller when exceeded permissible Slope values An adaptation of calculation parameters or a fault message causes. Hazard detectors, especially fire detectors after one of the preceding claims, characterized in that the microcontroller with at least is provided with a digital filter, which the exponential smoothing of Performs measured value.