DE102007058102B4 - Condition monitoring system for an aircraft - Google Patents

Abstract

A condition monitoring system for monitoring structural parameters on an aircraft, comprising a sensor network comprising a plurality of sensor devices (12) adapted for attachment to a structure of the aircraft and associated with identifiers, the sensor devices (12) including temperature sensor units (18) and Acceleration sensor units (20), wherein the sensor units (18, 20) signal processing units (16) for preprocessing signals (18a, 20a) of the sensor units (18, 20), wherein the signal processing units (16) for correlating the signals (18a, 20a ) of the sensor units (18, 20) are formed, and with a central computer, characterized in that the identifiers are associated with the sensor means (12) for localization of the sensor means (12), and in that the central computer has an allocation unit which assigns the identifiers to a location at the structure assigns that the central computer to the compute a local load distribution from the values of the acceleration units (20) is formed using the location information that with the acceleration sensor units (20) acceleration in all three spatial directions is measurable and that the signal processing units (16) have tables for storing material data, by means of which the signals (18a, 20a) of the sensor units (18, 20) are correlatable.

Description

The invention relates to a condition monitoring system for monitoring structural parameters on an aircraft. The condition monitoring system includes a sensor network having a plurality of sensor devices configured for attachment to a structure of the aircraft. The sensor devices are assigned identifiers. Furthermore, the sensor devices have acceleration sensor units. The condition monitoring system has a central computer.

The structure of an aircraft is subject to various forces that can cause stretching, cracking or other damage. For regular maintenance, the structure of aircraft is therefore examined using various non-destructive methods to safeguard aviation. These methods include in particular the visual inspection, but also ultrasound or, if possible, radiographic measurements.

Mechanical loads due to impact, air resistance and gravity are the most frequent strains on the structure of an aircraft. These structures cause the structure to deform plastically. If the loads exceed a threshold, permanent damage and weakening of the material will occur. Such overloads can not always be avoided.

It is known that the stress-overload characteristic of a material is temperature-dependent. In other words, a stress that does not harm a structure at room temperature can damage the structure at temperatures below 0 ° C.

So far, forces occurring at the structure are at best measured centrally. An exact assignment or localization of measured values is not possible.

Out DE 698 10 975 T2 For example, a sensor system is known which has a multiplicity of sensors which supply data to a main computer by means of a communication bus. The sensor system includes, among other things, a bus conversion device which converts the signals between two such communication bus systems.

WO 01/61301 A1 discloses a method for determining mechanical stresses, for example in ships and aircraft. To determine these mechanical stresses sensors for measuring the mechanical stress, such as strain gauges, attached to the surface to be measured. The measurement results of the sensors are transmitted to a central unit via a digital measurement bus.

DE 10 2006 020 341 A1 The expert takes a sensor for a measuring point and a method for its verification. The sensor can transmit the measured data wirelessly to a tester. In regular operation, the sensors are connected via wire cables.

WO 98/44400 A2 shows a method for the automatic assignment of addresses in a bus system, especially FireWire. A system controller maintains a list of which devices are located at which location. This list is updated when the connected device is relocated to another port.

DE 10 2004 025 319 A1 discloses a seat status display system for passenger compartments of aircraft and vehicles. For this purpose, a sensor arrangement is provided in each seat, which serves to detect the state of a seat. For this purpose, the sensor arrangements can have, for example, an occupancy sensor and a belt sensor. An operating and display unit is electrically connected to the sensor arrangements via a bus and can graphically represent the states of the individual seats.

DE 40 12 367 A1 the expert takes an air data system for aircraft, in which a pressure measurement is carried out at different locations of the aircraft. The data obtained is used for engine control.

From the US 2007/0265790 A1 a sensor network is known in which sensors are preferably arranged in pairs at corresponding positions on a structure to be monitored. By comparing the measured values of the different sensors, conclusions can be drawn about damage in the structure.

Against this background, the object is to provide a device and a method by means of which a distribution of mechanical loads on a structure can be reliably determined in a simple manner.

To solve this problem, a condition monitoring system according to claim 1 is proposed.

An aircraft provided with such a condition monitoring system and a method for monitoring the condition of a structure of an aircraft are the subject matter of the subsidiary claims.

Advantageous Augestaltungen of the invention are the subject of the dependent claims.

The condition monitoring system according to the invention has the advantage that it enables immediate measurement of parameters, such as acceleration, at different points of the structure of the aircraft with pinpoint accuracy. Furthermore, the measured parameters can be assigned to exact positions on the structure by the unique identifier of the sensor devices. The measurement of the acceleration values allows to calculate deflections of the structure. By measuring the acceleration in three spatial directions, not only the amount of acceleration but also its direction can be detected.

In an advantageous embodiment, the sensor devices have communication devices with which the measured parameters can be read out. Furthermore, these communication devices are advantageously designed for wireless information transmission. This has the advantage that the sensor devices can also be arranged at locations where a cable routing would be difficult to realize.

The communication devices can be designed to transmit the identifier together with the measured environmental parameters. Thus, with a transmission of the measured parameters, an assignment of the received parameters to a sensor device and thus to a location on the structure is possible directly.

In an advantageous embodiment, the sensor devices have temperature sensor units. Thus, it is possible to determine a temperature distribution in the structure. Furthermore, this information is useful to evaluate the maximum stress of the structure depending on the temperature.

The sensor devices advantageously have signal processing units for preprocessing signals from the sensor units. This can significantly reduce the amount of data to be transmitted. The signal processing units can be designed to correlate the signals of the sensor units.

In an advantageous embodiment, the signal processing units have tables for storing material data, by means of which the signals of the sensor units can be correlated.

The sensor devices can be designed to measure the distance from each other. This allows the detection of strains or compressions of the structure.

A method according to the invention has the following steps in particular:
Using a condition monitoring system;
Reading the values measured by the sensor devices as well as the identifiers;
Locating the respective sensor device on the basis of the identifier so as to obtain a location determination for the read-out parameter value;
Calculating the deflection of the sensor device from the measured acceleration values;
Determining a load distribution over the sensor network.

The method according to the invention has the advantage that parameters of the structure can be measured locally with little wiring effort. Low wiring costs result in a lower weight of the sensor system. Furthermore, by using acceleration sensors in the sensor devices, it is possible to measure one of the most important parameters of the structural load.

If, in fact, the deflection of the sensor devices is calculated from the measured acceleration values, then the strain of the structure can be deduced therefrom.

The correlation of measured temperature and deflection measured values allows adaptation of the maximum values for the load to temperature-dependent material properties.

Deciding whether damage to the structure is likely due to the correlated temperature and acceleration measurements allows for a targeted impact on the length of the maintenance interval and can help pinpoint damage. By measuring the distance between the sensor means located by means of identification, and a comparison of the measured distance with a stored reference value for these sensor devices, material deformations in the structure can be detected.

A comparison of two load distributions recorded at the same time offset under the same conditions and an estimation of the probability of damage to the structure due to the differences in the load distributions advantageously brings about early warning of damage. Thus it is already possible in flight to estimate whether damage to the structure is to be expected. According to the data collected in this estimation, maintenance intervals can be shortened or extended.

The invention will be described below with reference to an embodiment shown in the attached Drawings is shown schematically, explained in more detail. Show it:

1 an aircraft, here an airplane, with a sensor network and

2 a block diagram of a wireless sensor device

In 1 is the example of an aircraft 10 shown as sensor devices 12 on such an airplane 10 can be distributed.

2 shows a block diagram of a wireless sensor device 12 , The sensor device 12 has a communication device 14 , which is designed as an antenna with high-frequency electronics, a signal processing unit 16 an acceleration sensor unit 18 and a temperature sensor unit 20 on. The antenna and the high-frequency electronics are for example for radio frequencies (RF part of the sensor device 12 ) designed.

The acceleration sensor units 18 are preferred triaxial devices that the typical load range during the operation of the aircraft 10 cover. The temperature sensor units 20 cover typical temperature ranges for aircraft. Here the measuring range extends from -70 ° C to 50 ° C.

Load and stress profiles can be used during the flight or at maintenance intervals. This results in an on-board, real-time condition monitoring system that reduces maintenance costs and increases the usual maintenance intervals.

The sensor units 18 . 20 transmit measured signals 18a . 20a to the signal processing unit 16 , In the signal processing unit 16 become the signals 18a . 20a analyzed and processed. The value 22 from the signal processing unit 16 to the communication unit 14 contains information about the magnitude of the acceleration in each spatial direction, which are correlated with the temperature. By means of the antenna 14 and high-frequency electronics become the value 22 sent to a central computer. For localization, the high frequency electronics adds value 22 an identifier, such as a node number added.

In the system proposed here, sensors are added to a network node, thus providing a sensor device 12 in the form of a wireless network node. With the sensor devices 12 For example, information about parameters that influence the state of the structure can be obtained. Typical parameters that indicate congestion situations are acceleration and temperature, and the combination of these parameters.

A wireless sensor network equipped with sensor devices 12 is used to collect basic information about the condition of the (aircraft) structure. The sensor devices 12 are distributed throughout the structure so that critical areas can be monitored more closely monitored by a denser network, whereas less critical areas will result in less sensor device distribution 12 exhibit.

By analyzing the from the sensor devices 12 It is possible to detect congestion situations that may (or have already led to) damage the structure. It is even possible to detect damage directly by comparing two series of data collected under the same conditions.

This can be achieved, for example, by data stored in a sensor device 12 were recorded in a wing tip, with those from a sensor device 12 be compared at the wing root.

By double integration of the acceleration difference between the two points, the wing displacement and thus due to the expansion or compression of the wing, the mechanical load of the wing can be calculated. If the displacement exceeds certain reference values, an indication of weakening of the structure or even a defect is obtained.

The sensor devices 12 have a wireless communication interface, electronics, at least one supply device, and at least one sensor. The electronics have, for example, a sensor control, a memory device, a signal processing device and / or a data processing device.

The supply device supplies the sensor device 12 with energy. For this purpose, batteries, energy harvesting devices and / or energy converters are provided.

As sensors, for example, acceleration or temperature sensor devices 18 . 20 into consideration. Furthermore, moisture, gas or other advantageous sensors can be provided.

The communication can be realized by means of different network topologies. For the ground operation of the system, the network does not play an important role. Even point-to-point connections could be possible. However, in order to use the system in flight, a low-consumption, secure and fault-tolerant architecture is used.

The communication device 14 is accordingly designed so that the desired topologies can be used. If point-to-point connections are desired, these must be provided in the electronics.

So that the sensor devices 12 can be located, it is provided that they have an identifier for each sensor device 12 is unique. This identifier may be, for example, a code number, a location or - as mentioned above - node number.

A central computer containing the information of the sensor devices 12 reads out, for localization on an allocation unit, by means of which the identities places on the aircraft 10 or to whose structure can be assigned. This makes it possible to have the central computer calculate a load distribution, in particular a local load distribution.

In order to facilitate the linking of the identifier with the sensor data, it is provided according to an advantageous embodiment that the communication device 14 their identifier with each record that is transmitted with transmitted.

Another interesting factor of the proposed system is that the network allows the measurement of a load and stress profile across the aircraft structure using direct signal and data processing in flight.

The amount of calculations performed in the signal processing unit 16 depends on the available power. When the sensor device 12 wired (which is possible, but less preferred because of the need for cabling), enough power could be available to perform a large number of calculations using an internal database of material information. In contrast, an ultrasparsame wireless sensor device 12 mainly reduce and store signals. The data is only transmitted to the central computer on request, where it is additionally processed to create a general load profile.

In addition, the data can be linked to other information, such as an exact distance measurement between the nodes. This makes it possible to measure the change in position or the deviation of the structure. This could increase the value of records relating to congestion situations in parts of the structure.

LIST OF REFERENCE NUMBERS

10

plane

12

sensor device

14

communicator

16

Signal processing unit

18

Acceleration sensor unit

18a

signal

20

Temperature sensor unit

20a

signal

22

value

Claims (13)

Condition monitoring system for monitoring structural parameters on an aircraft, comprising a sensor network comprising a plurality of sensor devices ( 12 ), which are designed for attachment to a structure of the aircraft and to which identifiers are assigned, wherein the sensor devices ( 12 ) Temperature sensor units ( 18 ) and acceleration sensor units ( 20 ), wherein the sensor units ( 18 . 20 ) Signal processing units ( 16 ) for preprocessing signals ( 18a . 20a ) of the sensor units ( 18 . 20 ), wherein the signal processing units ( 16 ) for the correlation of the signals ( 18a . 20a ) of the sensor units ( 18 . 20 ) are formed, and with a central computer, characterized in that the identifiers the sensor devices ( 12 ) for the localization of the sensor devices ( 12 ), and in that the central computer has an allocation unit which assigns the identifiers to a location on the structure, that the central computer calculates a local load distribution from the values of the acceleration units ( 20 ) is formed using the location information that with the acceleration sensor units ( 20 ) an acceleration in all three spatial directions can be measured and that the signal processing units ( 16 ) Have tables for storing material data by means of which the signals ( 18a . 20a ) of the sensor units ( 18 . 20 ) are correlatable. Condition monitoring system according to claim 1, characterized in that the sensor devices ( 12 ) Have communication facilities with which the measured parameters can be read out. Condition monitoring system according to claim 2, characterized in that the communication means are adapted for wireless information transmission. Condition monitoring system according to one of claims 2 or 3, characterized in that the communication means for transmitting the identifier are formed together with the measured parameters. Condition monitoring system according to one of the preceding claims, characterized in that the sensor devices ( 12 ) are formed for measuring the distance from each other. An aircraft with a condition monitoring system according to any one of the preceding claims. A method of measuring structural parameters on an aircraft characterized by the steps of: a) using a condition monitoring system according to any one of claims 1 to 5; b) reading out from the sensor devices ( 12 ) measured values as well as the identifiers; c) locating the respective sensor device ( 12 ) on the basis of the identifier so as to obtain a location determination for the parameter value read out; d) calculating the deflection of the sensor devices ( 12 ) from the measured acceleration values; e) determining a load distribution over the sensor network. Method according to claim 7, characterized by the step: Correlation of measured temperature, displacement and acceleration measurements. Method according to claim 8, characterized by the step: Deciding if damage to the structure is likely due to the correlated temperature and acceleration measurements. Method according to one of claims 7 to 8, characterized by the step: measuring the distance between the sensor means located by means of identification ( 12 ) and comparing the measured distance with a stored reference value for these sensor devices ( 12 ). Method according to one of claims 7 to 10, characterized by: Compare two records taken under the same conditions to detect corruption of the structure due to differences in the records. A method according to claim 11, characterized in that measured data records are stored and later by the same sensor devices ( 12 ) are compared. A method according to claim 11 or 12, characterized in that the data sets to be compared are measured at different locations and the comparison result is compared with predetermined values for these locations.

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