GB2336675A - Vibration monitoring system - Google Patents

Abstract

A vibration sensor monitoring system (10) comprises a plurality of accelerometers (12) located to monitor the vibration of a process or machine, each sensor being connected to a waypoint (16) comprising a multiport connector. A connector element (26,28) is adapted to detachably connect with the or each waypoint. A multiplexor (24) selects signals from sequential ones of said sensors and comprises means to activate the sensors. A conditioner (32) amplifies/conditions the signal received from each sensor. Transmission means (36) transmits the digitised signals to a computer device (30). At least the multiplexor and conditioner are portable, integrated components (20) for selective connection to the sensors, although they could be integrated with the functional components mentioned above.

Description

2336675 VIBRATION MONITORING SYSTEM This invention relates to a vibration

monitoring system for industrial s processes and machinery. The invention finds application where it is necessary to monitor vibration in several positions in a process or piece of machinery to ensure the process/machinery is maintained in a satisfactory condition.

Thus it is frequently required to ensure that vibration is within design io limits at different points in a process. Sometimes it is necessary to monitor vibration constantly; minor variations being a cause for concern and provoking immediate remedial action, which can sometimes, of course, be automatic. Other processes merely require occasional monitoring, on the basis that vibration is only expected to vary gradually, or is not expected under normal circumstances to vary at all, and therefore periodic checking of vibration status is all that is needed.

Some processes require monitoring in several different places at a close proximity. For example, working machinery is always subject to some vibration, which is almost impossible to avoid. However, by monitoring the vibration at different points of a machine, it is frequently possible to diagnose the condition of the machine; to anticipate potential failures; and to identify the nature of such failures.

Vibration monitoring is conducted by probes or sensors (usually accelerometers) securely fixed to the machine so that their response reflects the vibration of the machine. Typically, bearings, fans, gearboxes, transmissions, pumps, in fact, generally all rotating or reciprocating components, may each have one or more associated sensors. However, since the monitoring is to check the health of the machine, it is not required frequently, but rather only occasionally. Thus it is common practice only to provide fixed sites on s machinery to which a probe can be temporarily connected. For example, the site may comprise a socket welded to the machine at an appropriate place to which the sensor, provided with bayonet lugs, can be connected.

The sensor is connected to a monitoring device and can be connected to lo each socket in turn. A reading is taken by the monitoring device when the sensor has settled down after connection of the sensor to a socket. By necessity, the monitoring device is small enough to be portable, and consequently has limited capabilities. Nevertheless, it powers and receives the signal from the sensor; it conditions the signal; converts the signal from analogue to digital; transforms it; and stores it. Moreover, it can analyse the stored signal so that particular aspects of it can be examined (for this, purpose it has a display); cursors can be inserted for identification, marking and sectioning; aggregate values can be extracted from the stored data and trend of these values can be produced from a stored history. Later, the stored signals are downloaded to a computer where they can be further analysed and a diagnosis of the condition of the machine produced.

Some of the functionality mentioned above is, or can be, implemented in software, but, at the front end of the system, the signal from the sensor requires ampIffication and immediate processing in order to put it in a condition where it can be handled relatively easily with conventional processors and appropriate software. Consequently there is usually some unique signal detection, amplification and conditioning hardware which is dedicated to the sensor in question and the parameter it is detecting.

Another feature of such a portable device is its ruggedness; it must be capable of fairly rough handling because it win be taken to, and used in, an area where industrial machinery or processing apparatus is operating. Such areas are inevitably dusty, hot, contaminated, cold, noisy, or any combination thereof, and delicate computer equipment can easily be damaged. As a consequence, such portable devices as mentioned above are usually dedicated lo pieces of equipment for the fimction which they are to accomplish and are given the requisite environmental protection to carry out their job.

Unfortunately such dedication inevitably results in an expensive piece of equipment. Even more expensive is a presently available alternative where sensors and a non-portable monitoring device are permanently fixed in place and plumbed into the machinery they are monitoring.

Typically, up to 32 sensors can be connected to some piece of equipment, or maybe several pieces, if they are located adjacent each other.

Moreover, there may be more than 32, whether in blocks of 32,, or some other convenient multiple, or even not in blocks at all.

These sensors are connected to a multiplexor in a front-end processor unit within the vicinity of the 32 sensors (bearing in mind the proximity needed in order to retain signal strength). In turn, the processor interrogates each channel and carries out the first stages of signal amplification and conditioning, before analogue/digital conversion, sampling, transformation and finally transmission to some remote computer. Other front-end processors may also be in communication with the remote computer, covering other multiples of 32 sensors (or more or less, depending on the system). The remote computer win conduct a fifil signal analysis of each signal in turn and provide the diagnosis of the equipment monitored by the various sensors.

Such a fixed system is very expensive, but little or no alternative appears to be available. Despite the expense, if such system monitoring prevents catastrophic failures and enables planned servicing to cure anticipated lo problems before they become serious, the expense is frequently worthwhile.

Nevertheless, it is an object of the present invention to provide a system which will reduce the expense, certainly of the portable system mentioned above, and especially of the fixed system where the present invention finds application by providing a system which permits the use of more commonly available, and therefore less expensive, equipment.

Thus,- in accordance with the a first aspect of the present invention, there is provided a vibration sensor monitoring system comprising:- a) a plurality of vibration sensors located to monitor the vibration of apparatus or a process; b) one or more waypoints, each comprising a multiport connector, and each being connected to one or more of said sensors; c) a connector element adapted to. detachably connect with the or each waypoint; d) a multiplexor to select signals from sequential ones of said sensors and comprising means to activate the sensors; and e) a conditioner to amplify/condition the signal received from each sensor, wherein at least said multiplexor and conditioner comprise integrated components in a portable adaptor for connection between the or each waypoint and a personal computer.

Preferably, the system also includes a sampler to sample conditioned signals, and/or a converter to transform conditioned signals.

Said sampler may be disposed on a data acquisition card inserted in a personal computer. Moreover, said adaptor may have an output cable for local connection to said card, which may be a PCMCIA card. Said converter may be a program incorporated in the personal computer.

Said adaptor may be adapted to connect directly with the or each waypoint. Alternatively, and this is preferred, said connector element may comprise a multi-line input cable and interface for connection with the or each waypoint.

Said adaptor, in a second aspect of the present invention, includes said sampler and is in the form of a data acquisition card inserted in a personal computer, in which event said connector element comprises said multi-line input cable and interface for connection with the or each waypoint.

A problem with this aspect, which is not presently preferred, is that said conditioner needs to be adapted to the signal which said sensors produce and which will vary from sensor type to sensor type. Since PCMCIA type cards or similar devices for direct insertion in personal computers are expensive to develop, and usually employ expensive miniaturised construction techniques in their manufacture, it is likely to be prohibitively expensive to develop and manufacture them for merely a vibration analysis applications. Since it is an object of the present invention to minimise the expense of the vibration monitoring system, this alternative is unlikely to be implemented, at least while production methods and costs are at current levels. However, the pace of development in this field cannot rule out this possibility in the medium to long term.

Software in the computer may be adapted to initiate the multiplexor to commence sequential sampling of signals from the sensors connected to it.

A timer may be included, enabling each sensor to be sampled in turn and for sufficient time to receive a representative signal. The computer device may have a storage device in which information about said conditioned signals can be stored for subsequent downloading or processing.

Said vibration sensors are preferably accelerometers.

In a basic form, being a third aspect of the present invention, there is also provided a vibration sensor monitoring system comprising:- a) a vibration sensor, adapted to be placed in a position to sense the vibration of a machine or process; b) an adaptor connected to the sensor comprising means to activate the sensor and a conditioner to amplify/condition the signal received from each sensor, said adaptor having substantially no other functionality; and, c) a personal computer, to which said adaptor is connectible, said computer including a sampler to sample signals from the adaptor and a converter to transform said signals.

is The invention also provides a method of monitoring vibration of a process or machinery including a vibration sensor monitoring system according to the first aspect of the present invention, comprising the steps of, a) selectively connecting said connection element to the or one of the waypoint(s); b) initiating said multiplexor to commence sampling signals from sequential ones of said sensors; c) conditioning said signals; d) transmitting said signals to said computer device.

There are presently available standard integrated samplers capable of direct insertion into commercially available computer devices. Such converters are adapted to receive signals within certain specified voltage ranges and to present such signals to the computer device in such a way that, under appropriate software control, the computer can store, process and analyse said signals. For example, PCMCIA cards are available for insertion in personal computers in their expansion slots which perform this function.

The computer can then flirther process the received signals, for example, converting them from raw data to spectra and subsequent analysis against historical information, alarm threshold data etc.

The benefit of the present invention is that multiple sensors are placed in position on machinery or processing equipment and left in place. Each sensor is wired to a waypoint which is local to the sensor but in a convenient and "computer-friendly" environment.

Preferably, where there are more than one waypoint, each waypoint is coded to identify itself.

From time to time, an operator interested in collecting data about the io performance of machinery or process incorporating a vibration monitoring system in accordance with the first aspect of the present invention, visits the or each waypoint with either the adaptor and portable computer device, or the computer device with incorporated adaptor, depending on which embodiment of the invention is applicable.

In the case of the first aspect of the present invention, the adaptor, or its multi-line cable if it has one, is plugged into the waypoint and the system is activated. Each sensor is selected in turn according to a preprogrammed or random sequence (as long as each sensor being sampled is identified). Signals received are amplified and conditioned, as necessary according to the nature of the signal emanating from the sensor, sampled and converted. Additionally, the computer can conduct various forms of analysis straight after reception of the signals, but typically, the primary task is first to collect signal samples, and probably to analyse them later.

In the case of the second aspect, a similar scenario applies, except here the connector element, in the form of said multi-line cable connected to the personal computer, is plugged into the or each waypoint.

In each case. software in the computer, will be invoked to initiate the multiplexor so that it commences sampling signals from the sensors connected s to the relevant waypoint. Each sensor will be sampled in turn and for sufficient time to receive a representative signal.

Thus the system of the present invention, at least in its first aspect, comprises the minimum dedicated electronics for the two purposes of io multiplexing and conditioning and so that a conventional portable computer, provided with conventional signal processing means, or relatively inexpensive sampling and conversion means, can be employed. The result is a minimisation of the specialisation of the equipment, thereby rendering the cost much more affordable. While there is the extra cost of actually plumbing-in all the sensors required and feeding their cables back to one or more central waypoints, nevertheless, this means that the exposure of standard portable computers, which are sensitive pieces of equipment, is minimised, and the danger of damage being caused to them by operatives clambering over equipment with the computer in one hand and the sensor in the other is avoided. Indeed, this extra cost is often in any event incurred, both with existing fixed systems and some portable systems. In the latter, for example, it is known to connect several sensors to a manual switch which connects each sensor in turn to an output socket to which an input of the portable device may be connected.

Of course,, not all these advantages are felt with the basic system of the third aspect of the present invention, but if the personal computer is protected, -1 0- it represents a very cost-effective solution. Moreover, the second aspect is presently not a particularly cost-effective option, given the specialisation required of the interface card inserted in the personal computer, but time may prove this option to be just as, or even more, attractive than the first aspect.

The first and second aspects of the present invention are best employed with a single adaptor/personal computer, and multiple waypoints being visited m turn (however many times a day, week or month is required), readings being taken and the results downloaded, either at the end of the day or more io frequently. For example, the personal computer could have, or be connected to,, a modem employing a mobile telephone, so that data could be downloaded almost as quickly as it is collected.

The invention is flu-ther described hereinafter, by way of example, with is reference to the accompanying drawings, in which:- Figure 1 is a schematic representation of a system according to a second embodiment of the present invention; Figure 2 is a schematic representation of the ftmctions performed in a sensor monitoring system; and, Figure 3 is a schematic representation of a system according to the first aspect of the present invention; Figure 4 is a schematic representation of a system according to the second aspect of the present invention; and, Figure 5 is a schematic representation of a system according to the third aspect of the present invention.

In Figure 1, a series of accelerometers 12 form the working face of a vibration monitoring system 10. The accelerometers are connected to various parts of machinery (not shown) in strategic positions so that, should any component within the machinery begin to vibrate unusually, this fact is s detected by one or more local accelerometers. Accelerometers produce very weak signals. Consequently, cabling from them before the equipment which receives their signals must be short in order to prevent signal distortion.

All the cables 14 form a group, typically of 8, 16 or even 32 cables, io which are brought together at a waypoint 16, comprising a connector strip, fixed in some convenient location sufficiently close to the machinery to avoid any substantial signal loss or distortion, but which is clean and "computerfriendly".

Adaptor 20 comprises a component housing 22 mounting a multiplexor 24 to which an input cable 26 is connected. The cable 26 has a plug 28 at its end adapted to fit and connect with waypoint 16. The multiplexor is under the control of a computer 30 and activates the accelerometers and sequentially selects signals from the different accelerometers and passes such signals to a conditioner 32. It is accordingly bi-directional and has at least eight channels. The conditioner is also under control of the computer 30.

A timer (not shown) in the computer 30 controls the selection time of the multiplexor to ensure a sufficiently meaningftd sample of signal is taken.

Similarly, the timer can delay sampling to allow the system to settle when new connections are made by the multiplexor.

The conditioner 32 provides power for the accelerometers and conditions the signals received from them by amplification and possibly some shaping/filtering to remove noise or unwanted artefacts, for example. The signal is also rendered in a form such that signal reception devices currently available for personal computers can accept the signal and process it. One such device is in the form of a PCMCIA card which is insertable in the expansion slot of most personal computers on the market today. Such a data acquisition tool should have at least a single channel with bi-polar operation; it should have at least 12-bit resolution; and at least 60 KHz sampling frequency.

lo The buller amplifier of the conditioner should have a frequency response appropriate to the sampling frequency of the PCMCIA card.

A PCMCIA card is a complex piece of equipment requiring advanced manufacturing processes for its construction. Sampling and processing of various signals is, of course, a common requirement and so it is worth the expense associated with the design, development and manufacture of a suitable interface for the reception of signals for their subsequent manipulation and processing by a computer. However, not all signal sources provide a signal which such a general interface can accommodate. Moreover, in many specialised areas of signal generation and analysis, it is not, at least at present, cost efFective to provide a PCMCIA card adapted to handle such signals.

The present invention therefore provides the conditioner 32 adapted to the signals emanating from the accelerometers 12 to provide at its output 34 a signal which a currently available PCMCIA card 36 inserted into the computer 30 can receive and manipulate. The output 34 of the adaptor 20 is therefore adapted to plug into the socket (not shown) of the PCMCIA card 36.

Turning to Figure 2, the signal from an accelerometer 12 is therefore first selected and conditioned at 40. Thereafter the signal undergoes a first conversion, possibly merely an analogue to digital conversion at 42. The signal is then sampled at 43 and transformed at 44. This transformation may comprise convertion of raw data to a spectrurn, for example. It is then stored locally at 48 and can either be analysed locally at 50 or, after transportation at 46, remotely, but in either case to produce a user output at 52.

For example, the computer may store vibration signatures for the accelerometer in question. Analysis may then comprise a comparison of subsequent signal samples against stored samples. The signal may also be analysed to establish possible causes of any variations detected, and whether such variations are potentially catastrophic, requiring immediate attention, or is merely developmental, requiring attention at a subsequent routine service of the machinery.

Returning to Figure 1, after connection of the computer 30 and its adaptor 20 to the waypoint 16, and after a signal from each of the accelerometers has been sampled and stored in the storage device of the computer 30, the plug 28 is disconnected from the waypoint and, in a site having multiple waypoints, the computer 30 and sampler 20 are taken to the next waypoint.

A great advantage of the present arrangement is that the identities of the accelerometers can be pre-programmed into the computer so that the computer can sample each accelerometer in its own pre-programmed or random sequence depending on which waypoint it is connected to. The only requirement is that the personal computer knows which sensor is being sampled. However, this is inevitable since it selects the sensor itself through the multiplexor. Which waypoint is chosen my be a matter of choice for the operator, and so those, at least, are preferably coded so that the computer knows which one it is connected to. For example, each waypoint could include a two pin socket across which is connected a resistor of specific resistance.

When connected to the waypoint, the resistance could be measured by the computer and this would identify the waypoint. Other suitable coding lo techniques will be apparent to the skilled person. Alternatively, the operator could input the waypoint identity.

With presently available portable systems, the system is capable of handling multiple samples, but only in the order in which the user connects the is system to each accelerometer site. If he/she connects in the wrong order, the system will be none the wiser.

Consider that a known system, analogous to the arrangement described above with reference to the top part of Figure 1, is employed: here groups of accelerometers would be connected together and fed to a manual switch having a single output fed to the standard meter. Indeed the meter can be programmed with the sequence of accelerometers to be sampled, but again the switch is under manual control and mistakes can be made. For example, the same signal could be read twice if the operator forgets to switch to the next signal. A system along these lines is disclosed in US-A-4612620.

With the processing power of a personal computer on hand, such -1 5mistakes can be avoided, at least in respect of the sampling of the accelerometer in any one waypoint group.

In any event, when all waypoints and accelerometers have been sampled, several options are now available to the user of the present invention. Any of the myriad communications techniques available to personal computer users can be employed. The sampled data can be downloaded to another computer by direct connection, by floppy disc or by remote connections through a modem and telephone line. Where sampling is required urgently or io merely in a more timely manner, communication through a mobile phone also connected to the computer is possible, perhaps even while the signals are being received.

On the other hand, processing and analysis of the signals may be conducted on the same computer 30 responsible for their collection.

The present invention therefore serves not only to minimise the amount of specialised equipment required to sample a wide variety of difFerent signals from various parameter sensors, and therefore reduce the high cost of presently available equipment, but also serves to give much greater flexibility and functionality to the overall system by virtue of the introduction of regular personal computing equipment.

This is possible by virtue of the realisation that the specialised and 2s dedicated equipment required can be significantly reduced to the basic mtegrated components of a multiplexor and conditioner, the waypoint being located in a computer-fdendly environment permitting the application of everyday portable computers.

This is represented in a different way in Figure 3, where the functions performed are represented in the basic components of the system, namely the adaptor 20, which is arranged to SELECT and CONDITION the signal, and the personal computer 30, which is arranged to SAMPLE, in a PCMCIA card, and subsequently to TRANSFORM, STORE and ANALYSE the signal.

It is within the ambit of the present invention that the multiplexor and lo conditioner may in the future be incorporated into a plug-in expansion card along the lines of a PCMCIA card. This does not detract from the principle of the present invention, and this scheme, being the second aspect of the present invention, is illustrated in Figure 4. Here the four functions of SELECT,.AMPLIFY, CONDITION and SAMPLE are all integrated in a dedicated PCMCIA type card 36', inserted in a computer 30.

Finally, in Figure 5, the invention, in its third aspect, is reduced to its barest essentials,, in which a personal computer having the functions described above with reference to Figure 3 is connected to an adaptor 20' to which a single accelerometer 12 is permanently connected. Here there is therefore no SELECT function, and no multiplexor to perform that function. The adaptor 20' has no other functionality than to provide power for the accelerometer and render the signal received therefrom suitable for processing by a standard PCMCIA card in a personal computer. It is therefore very inexpensive to manufacture.

Claims (18)

1. A vibration sensor monitoring system comprising:- a) a plurality of vibration sensors located to monitor the vibration of apparatus or a process; b) one or more waypoints, each comprising a multiport connector, and each being connected to one or more of said sensors; c) a connector element adapted to detachably connect with the or each waypoint; d) a multiplexor to select signals from sequential ones of said sensors and comprising means to activate the sensors; and e) a conditioner to amplify/condition the signal received from each sensor, wherein at least said multiplexor and conditioner comprise integrated components in a portable adaptor for connection between the or each waypoint and a personal computer.

2. A system as claimed in claim 1, ftu-ther comprising a sampler to sample conditioned signals.

A system as claimed in claim 2, in which said sampler is disposed on a data acquisition card adapted for insertion in a personal computer.

4. A system as claimed in claim 3, in which said adaptor has an output cable for local connection to said card.

A system as claimed in claim 3 or 4, in which said card is a PCMCIA card.

6. A system as claimed in any preceding claim, in which said adaptor is adapted to connect directly with the or each waypoint.

7. A system as claimed in any of claims 1 to 5, in which said connector element comprises a multi-line input cable and interface for connection with the or each waypoint.

io

8. A system as claimed in claim 2 and 3, in which said adaptor includes said sampler and is in the form of a data acquisition card for insertion in a personal computer.

9. A system as claimed in any preceding claim, further comprising a is personal computer including a converter to transform conditioned signals.

10. A system as claimed in claim 9, in which software in the computer is adapted to initiate the multiplexor to commence sequential sampling of signals from the sensors connected to it.

11. A system as claimed in claim 10, ftu-ther including a timer, enabling each sensor to be sampled in turn and for sufficient time to receive a representative signal.

12. A system as claimed in claim 9, 10 or 11, in which the personal computer has a storage device in which information about said conditioned signals can be stored for subsequent downloading or processing.

13. A system as claimed in any preceding claim in which said sensors are accelerometers.

s

14. A vibration sensor monitoring system comprising:

a) a vibration sensor, adapted to be placed in a position to sense vibration of a machine or process; b) an adaptor connected to the sensor comprising means to activate the sensor and a conditioner to condition the signal received from each sensor, said adaptor having substantially no other fimctionality; d) a personal computer, to which said adaptor is connectible, said computer including a sampler to sample signals from the adaptor and a converter to transform said signals.

15. A method of monitoring vibration of a process or machine including a vibration sensor monitoring system as claimed in any of claims 1 to 13, comprising the steps of, a) selectively connecting said connection element to the or one of the waypoint(s); b) initiating said multiplexor to commence sampling signals from sequential ones of said sensors; c) conditioning said signals; d) transmitting said signals to a personal computer.

16. A method as claimed in claim 15, further comprising the step of digital conversion of the signals.

17. A method as claimed in claim 15 or 16, in which said initiation is effected under software control in the computer device.

18. A system and method for monitoring vibration in machinery, substantially as hereinbefore described with reference to the accompanying drawings.