GB2251071A

GB2251071A - Vibration monitoring system

Info

Publication number: GB2251071A
Application number: GB9124452A
Authority: GB
Inventors: Robert Malcolm Newman; Brian Robinson
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-11-19
Filing date: 1991-11-18
Publication date: 1992-06-24
Anticipated expiration: 2011-11-18
Also published as: GB9124452D0; GB2251071B; GB9025142D0

Abstract

A vibration monitoring system is intended to enable a plurality of vibration sensors (10) to be coupled to a central computer or computers in an efficient manner to enable data to be collected from the sensors. The sensors are each associated with signal processing means (13, 14, 15) which transmits signals over a digital network to the central computer. Vibrations detected by the individual sensors generate signals which are processed adjacent or within the sensors and transmitted over the network to the central computer. In one embodiment (figs 6, 7, not shown) the circuit board (39) holding the signal processing means is folded over the assembly formed from the reaction mass (21), the machine element (24). securing screw (22) and insulator (23). The socket connection (31) is mounted directly onto one panel of the circuit board (39) and protrudes through the casing (22). <IMAGE>

Description

Vibration Monitorina Svstem This invention relates to vibration monitoring systems by which vibrations are detected, analysed and monitored.

Systems have been proposed for the monitoring, analysis and investigation of vibration phenomena in machinery, buildings and air, sea and land vehicles. These have generally made use of vibration sensors, typically accelerometers but also including other kinds of transducer placed at various points around the object or system being monitored. Such transducers have been coupled to a data collection and analysis system which generally comprises a computer and suitable signal processing and data capture apparatus.

Typically each sensor is linked to the computer by an individual cable, the signal carried by that cable being the signal output of the transducer.

In the case of systems requiring many transducers this method suffers from a number of disadvantages. Each transducer requires an individual analogue channel for signal processing and data conversion in the computer. As the number of transducers increases the data collection hardware of the computer becomes increasingly large, complex and expensive.

Systems using many transducers often suffer from a lack of processing resources to execute the analysis programs at the required speed. Moreover in systems in which the transducers are distant from the computer the low level analogue signals carried by the connecting cables may suffer from signal degradation, decreasing the performance of the system.

An object of the invention is to provide an improved vibration monitoring system.

According to the invention a vibration monitoring system comprises a plurality of vibration sensors, a central computer or computers for collecting data from the sensors, and a network connecting the sensors to the computer or computers, each of the sensors having associated with it signal processing means whereby signals generated by the sensors in accordance with vibration detected by the sensors are processed at or adjacent the sensors and then transmitted over the network to the computer or computers.

Preferably the data signal processing means of each sensor include means for processing signals generated by the sensor in one or more of the following ways: - Converting analogue signals to digital signals - Signal amplification Integration of the signal from an acceleration signal to a velocity signal - Integration of a velocity signal to a displacement signal - Digital signal processing including Fourier transforms - Charge amplification - Amplifying signals when the sensor is a transducer - Filtering signals from the sensors - Signal averaging - Signal storage of original signals and of transformed signals - Comparison of received signals with stored data and preprogrammed limits - Transmission of stored data signals to the computer or computers on demand or automatically.

Conveniently the network connecting the sensors and the computer or computers include signal transmission means common to a plurality of the sensors. The network may include a star network, a ring network or a bus network.

The signal processing means associated with a sensor may be located in a common housing or the sensor and the processing means may be physically separated from one another.

The signal processing means may include circuit boards rigidly connected to one another in spaced relationship and to the associated transducer which may include a reaction mass and piezoelectric means between the reaction mass and a base.

Alternatively the signal processing means includes a flexible circuit board located around a transducer, including a reaction mass, comprising the vibration detector.

The sensors may be connected together and to the computer or computers using a digital network which may also supply electrical power to the signal processing means. The digital network may use any applicable physical technology and data and control protocols.

The invention provides an integrated system which allows a number of tasks to be performed local to the sensors. The processing functions may include charge amplification (in the case where a Piezoelectric transducer is used), transducer signal amplification, integration of the signal from an acceleration to a velocity and again to a displacement signal, filtering, analogue to digital conversion, signal averaging, windowing, digital signal processing including Fourier transforms, storage of original and processed data, comparison of data against other data and preprogrammed limits, on demand and automatic transmission of stored data to the controlling computer and to other transducers. By providing an integrated system an open ended addition of processing power as transducers are added to the system is achieved.In addition low level analogue signals are replaced by more robust digital signals. Unnecessary data transmission is eliminated and there exists the possibility of continuing data capture and storage even when the controlling computer fails.

Provision may be made for two way communication between the sensors and the controlling computer. This allows the signal processor associated with a sensor to be issued with commands such as for new programs to be downloaded and for changes to be made in the reference data stored locally to the sensor.

The communication provisions also allow for communication between two or more of the sensors, allowing data transfer and computation using data from a number of sensors without intervention from the controlling computer.

Further features of the invention will appear from the following description of an embodiment of the invention given by way of example only and with reference to the drawings, in which: Fig. 1 is a schematic diagram showing a plurality of sensors, their associated network and a controlling computer, Fig. 2 shows a similar arrangement to Fig. 1 using a different network configuration, Fig. 3 shows an arrangement similar to Figs. 1 and 2 using a further network configuration, Fig. 4 is a block diagram showing the component parts of the system, Fig. 5 shows schematically one construction of sensor and associated signal processing equipment, Fig. 6 shows another construction corresponding to Fig. 5, Fig. 7 is an end view of the construction shown in Fig. 6, Fig. 8 shows an arrangement in'which a sensor is physically separated from the associated signal processing equipment, Fig. 9 shows an arrangement of multiple sensors, and Fig. 10 shows an arrangement whereby two sensors are associated with one signal processing system.

Referring to the drawings and firstly to Figs. 1, 2 and 3, in each case arrangements are shown in which a plurality of sensors 10, each associated with a signal processor 11, are connected through a digital network to a controlling computer 12. In Fig. 1 there is shown a multi-drop bus network, in Fig. 2 a ring network and in Fig. 3 a star network. In each case the controlling computer 12 is connected to the sensors 10 and signal processor 11 only by the digital data network.

More than one controlling computer may be present in the network, enabling access between the sensors and all the controlling computers in the network.

Usually the sensors take the form of transducers and, in association with the signal processing means, such combination is hereinafter termed an intelligent transducer.

Referring now to Fig 4 there is shown component parts of an intelligent transducer. The sensor 10, in this case a transducer incorporating an accelerometer, produces an analogue electrical output signal. However any kind of sensor which produces such a signal may be employed. In the case of an accelerometer the transducer consists of a reaction mass and an active element which converts the force produced by acceleration of the reaction mass into an electrical signal.

The signal produced by the transducer is passed to an analogue signal processing device 13, the nature of which is dependent on the type of transducer used. Usually it will include a low level input amplifier which may be a charge, current or voltage amplifier or bridge network, depending on the transducer. It may also include low pass or bandpass filtering, signal integration or differentiation, and an amplifier to produce a signal at the desired level for the next stage. Some kinds of transducer will also require the inclusion of an excitation voltage generator.

The signal from the analogue signal processing unit 13 is passed to an analogue to digital converter 14 which converts the analogue signal from the analogue signal from the transducer into digital data. The converter 14 is interfaced to a micropro-cessor 15. The microprocessor is provided with data memory 17 and program memory 18. An interface 19 to the digital network and timing control means 16 for timing the acquisition of data are also provided. These units are synchronised with the other intelligent transducers in the network.

The functional blocks shown in Fig. 4 may be realised by one or more monolithic or hybrid integrated circuits. In particular several of the blocks shown in Fig. 4 may be integrated into a microprocessor integrated circuit.

If multiple integrated circuits are used these are integrated together to provide the complete electronics package for a sensor on one or more printed circuit boards, using fibre glass, ceramic or other substrate material. The electronics package of the signal processing means is integrated with the reaction mass and the active element of the transducer.

Fig. 5 and Figs. 6 and 7 show two possible constructions for the complete intelligent transducer. Fig. 5 shows a construction in which two separate circuit boards are used.

In this arrangement a reaction mass 21 is retained by a screw 22 and is insulated electrically from the body of the unit by an insulator 23, compressing an active element 24 which comprises piezoelectric elements and electrodes between the reaction mass and base 25. The base is provided with a stud 25A to enable mounting of the complete assembly.

The active element 21 is connected by thin wires to a circuit board 30 which is secured to the base by threaded pillars 27 and washers 26. The circuit board 30 has a central hole to allow the active element to pass through it. Additional circuity is provided by a circuit board 29 secured on the pillars 27 by nuts 28. The circuit board 29 also provides a connection to a socket 31 which connects to the digital network. The whole assembly is enclosed by a cover 32 which is secured to the base 25 around its lower edge.

Figs. 6 and 7 show a simplified construction using a flexible circuit board 39, other parts of the Figs. 6 and 7 arrangement having the same reference numbers for similar parts to that of Fig. 5. The circuit board 39 is folded over the assembly formed of the reaction mass 21, active element 24, securing screw 22 and insulator 23. This arrangement avoids the need for the central hole and the mounting pillars of the Fig. 5 embodiment. The socket connector 31 is mounted directly onto one panel of the flexible circuit board 39 and protrudes through the cover 22. The circuit board 39 forms an inverted U shape and may be secured at each end by plates 33, as shown in Fig. 7.

Referring now to Fig. 8 this shows an alternative arrangement in which the sensor 10 is separated from an electronics package 11 which effects the signal processing. The connection is through a short length of cable 26 thereby allowing the positioning of the transducer 24 in an environment unsuitable for the electronics package.

Fig. 9 shows another arrangement by which two or more transducers may be associated with a single signal processing arrangement thereby allowing detection of vibration in three orthogonal directions. Thus there is a vertical transducer mounted internally within the electronics package which may be of the form shown in Fig. 5, or Figs. 6 and 7. Two additional orthogonal horizontal transducers 27 and 28 are mounted on adjacent walls of the enclosure, directed at right angles to one another and to the vertical transducer.

Fig. 10 shows an arrangement in which a single signal processing package is used to collect data from two transducers, in this case an accelerometer within the enclosure and a thermocouple 29 situated remotely and connected by a cable.

Claims

1. Vibration monitoring system comprising a plurality of vibration sensors, a central computer or computers for collecting data from the sensors, and a network connecting the sensors to the computer or computers, each of the sensors having associated with it signal processing means whereby signals generated by the sensors in accordance with vibration detected by the sensors are processed at or adjacent the sensors and then transmitted over the network to the computer or computers.

2. A system according to Claim 1 wherein the signal processing means of each sensor includes means for processing the sensor signals in one or more of the following ways: converting analogue signals to digital signals, signal amplification, integration of the signal from an acceleration signal to a velocity signal, integration of a velocity signal to a displacement signal, digital signal processing including Fourier transforms, charge amplification, amplifying signals when the sensor is a transducer, filtering signals from the sensors, signal averaging, signal storage of original signals and of transformed signals, comparison of received signals with stored data and preprogrammed limits, transmission of stored data signals to the central computer or computers on demand or automatically.

3. A system according to Claim i or 2 wherein the network connecting the sensors and the computer or computers includes signal transmission means common to a plurality of the sensors, the network including a star network, a ring network or a bus network.

4. A system according to Claim 1 or 2 comprising means for controlling or programming the signal processing means from the central computer through said network.

5. A system according to any one of the preceding claims wherein the signal processing means associated with one or each sensor is located in a common housing.

6. A system according to Claim 5 wherein the processing means includes circuit boards mechanically, rigidly connected to one another in spaced relationship and to the associated sensing means which includes a reaction mass and piezoelectric means between the reaction mass and a base.

7. A system according to Claim 5 wherein the processing means includes a flexible circuit board located around the sensing means which includes a reaction mass.

8. A system according to any one of the preceding claims wherein at least one of the sensors is coupled to but physically separated from the associated signal processing means.

9. A system according to any one of the preceding claims wherein two or more sensors are associated with one another and with signal processing means which is connected to the network.

10. Vibration monitoring system substantially as described with reference to Fig. 1, Fig.2 or Fig. 3 of the drawings having the sensor arrangement and signal processing means according to Fig. 4 and Fig. 5 or Fig. 6 and 7 or Fig. 8, 9 or 10.