Patent Application
20190162748
The invention relates to pump assemblies, methods and computer programs and in particular to monitoring the condition of a pump in such an assembly.
Pumps are precision instruments manufactured with tightly controlled tolerances which require careful use and regular servicing to maintain condition. The wear of moving parts and the requirement for servicing will vary with type of use and characteristics of the pump. Furthermore, misuse or accidental knocks may damage parts and trigger an unexpected servicing or repair requirement. Operation of the pump in a compromised or worn condition can lead to further damage.
It would be desirable to be able to provide a means of detecting the condition of a pump.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.
A first aspect of the present invention provides a pump assembly comprising: a pump, an associated motor controller and an accelerometer mounted on said pump; said motor controller being configured to control power supplied to drive said pump and to receive data output from said accelerometer, said motor controller comprising processing circuitry configured to process said data received from said accelerometer to determine accelerations experienced at said pump due to said pump operation.
The inventors of the present invention recognised that how smoothly a pump operates is an indication of its condition. An accelerometer mounted on the pump could be used to detect the smoothness of operation of the pump and how this changes with time. In particular, it could detect increases in vibrations for example, generated by operation of the pump in a non-optimal condition. Processing circuitry receiving data from such an accelerometer could be used to determine accelerations experienced at the pump due to its operation and from analysis of these signals, the condition of the pump could be estimated. Providing the processing circuitry for processing signals received from the accelerometer as part of the motor controller allows the processing circuitry to be mounted in an environment that is necessarily maintained at a temperature and position suitable for electronic circuitry as the motor controller comprises electronic motor controller circuitry. Furthermore, control signals for the control of the pump motor generated by the controller are also relevant when analysing the accelerations and this is a further advantage of mounting the processing circuitry for processing signals from the accelerometer within the motor controller.
In some embodiments, said processing circuitry is operable to process data received from said accelerometer in conjunction with motor controller data so as to separate acceleration data generated by said pump operation and other signals.
By providing the processing circuitry for processing the accelerometer data within the motor controller, motor controller data regarding the operation of the pump is also available and processing the accelerometer data in conjunction with this data allows accelerations experienced at the pump to be tied to different aspects of the driving of the pump, and also allows signals that are not caused by accelerations due to pump operation to be identified and separated from those that are due to such operation. In effect, by combining the acceleration and motor controller data which are both relevant to the operation of the pump and by analysing them together a better picture of its operation can be obtained.
The other signals may comprise electronic noise signals arising perhaps from switching circuitry associated with driving the pump motor or they may be accelerations detected by the accelerometer that are experienced at the pump and are due to external forces as opposed to operation of the pump itself. Being able to distinguish the accelerations that are due to pump operation, allows the operation to be more accurately analysed. Furthermore, detecting accelerations due to external factors such as the pump being knocked allows misuse to be detected.
In some embodiments, said processing circuitry is configured to synchronise sampling of data signals output from said accelerometer with at least one type of said motor controller data.
One way of combining the motor controller data and the accelerometer data to allow a more accurate analysis of the acceleration is to synchronise the sampling of the accelerometer data with at least one type of the motor controller data. For example, where the driving of the motor is via a pulse width modulated drive signal, then the switching of the signal will generate noise and synchronising the sampling of the acceleration signal to a mid point of this switching where the current, for example, is at its most stable value will enable a signal with lower noise components to be sampled and thereby increase the accuracy of the analysis.
In some embodiments, said processing circuitry is operable to correlate said data received from said accelerometer with said motor controller data.
One way in which the processing circuitry may combine the accelerometer data and the motor controller data is by correlating it in some way. In this regard, where data regarding the driving of the pump motor is known, then acceleration signals at particular frequencies can be tied to the frequency of the drive motor and in this way, accelerations due to the rotation of a rotor for example, or to the slower or faster rotation of the bearing elements can be isolated and analysed.
It should be noted that the motor controller data, that is available within the motor controller, may be motor control data which is indicative of motor control signals that are generated by the motor controller to control the motor. Alternatively and/or additionally, it may be data received by at least one sensor within the motor controller which is there to sense signals such as current output to the drive of the pump, voltage output, temperature of the motor controller and/or power supplied to it.
In some embodiments, said pump comprises a rotor and said at least one sensor is for sensing rotor speed or rotor angular position.
The sensor within the motor controller may determine rotor angular position or rotor speed. Alternatively, this may be determined at the processing circuitry from motor controller data indicative of control signals sent to the motor controller. In either case, the determination of rotor angular position and rotor speed can be used by the processing circuitry in conjunction with the data received from the accelerometer to generate rotor condition data. In this regard, accelerations experienced at the pump at particular rotor angular positions are indicative of the rotor with increased level of unbalance and thus, such signals can be used to help reduce the level of unbalance in the rotor initially and/or they can be used during servicing or later during operation to determine where there is change in the unbalance of the rotor and it requires rebalancing.
Furthermore, the rotor speed is related to bearing elements speed, the bearing elements move at a lower or higher multiple speed of the rotor. Thus accelerations that occur at particular frequencies may be indicative of bearing wear and can be used in the analysis of bearing condition. Bearing condition is important to accurately determine to try to avoid bearings deteriorating to a point where they may damage the pump. Furthermore, worn bearings make for a noisier pump particularly on start-up and an indication of bearing wear may indicate the reason for a noisy pump.
In some embodiments, the processing circuitry is configured to determine acceleration amplitude and phase from the signals received.
Both the acceleration amplitude and the acceleration phase are important indicators of pump conditions and can be used in the analysis of the pump.
In some embodiments, said processing circuitry is configured to convert sampled data from said accelerometer to the frequency domain.
As noted previously, vibrations at certain frequencies may be indicative of different elements of the pump and thus, when analysing the data, converting periodically sampled data from the accelerometer into the frequency domain, allows accelerations occurring at particular frequencies to be easily identified and this can be helpful in the analysis of the data and in particular in fault diagnosis.
In some embodiments, said processing circuitry comprises comparison circuitry for comparing data output by said accelerometer and processed by said processing circuitry with at least one threshold value to generate at least one warning signal.
As noted previously, signals from the accelerometer are indicative of pump condition and can be used for fault diagnosis. When used in conjunction with threshold values, they can be used to generate warnings indicating that operation of the pump is moving out of normal operational limits and as such may need some servicing or repair. This may take the form of rotor rebalancing, bearing replacement and/or other actions.
These warning signals may be used in conjunction with output circuitry for outputting warning indications, said output circuitry being configured to be triggered by said warning signals.
Once it has been determined that the signals received from the accelerometer indicate it is not operating within normal limits, then the warning signal so generated may be routed to trigger a warning indicator. This warning indicator may be in the form of lights on the pump or motor controller, which may indicate the severity of the warning using colour coding, amber perhaps indicating that a check is required or servicing should be done soon and red that the pump should not be operated. Alternatively, the warning indicators may be output on a communication line from the pump to an external system where a user or operator can be provided with information regarding the event detected. A memory may also be present in the motor controller or on the pump for recording acceleration events and the warning signals may be recorded in the memory and downloaded therefrom either via the communication line or via an output port such as a USB port.
Although the accelerometer is particularly useful for determining accelerations experienced at the pump due to pump operation which are indicative of the condition of the pump, the accelerometer can also be used to detect external forces causing acceleration at the pump. Such external forces may be due to an external impact and can be detected during operation, analysis of the frequency and amplitude of the signal indicating that it is not due to normal operation. Although it is helpful to detect such events during operation, such impacts may also occur when the pump is not in operation and in fact this may be more likely as the pump may be being moved between locations. As an accelerometer is provided on the pump to determine accelerations due to operation of the pump it can also be used to detect accelerations due to other causes. In order for this to function when the pump is not in operation a remote power source such as a battery may be required and thus, one may be associated with the accelerometer such that it can operate when the pump is not powered and any accelerations it detects can be stored within a data store and can be used to detect accelerations due to external forces caused by mishandling and/or other instances which may affect the condition and future operation of the pump.
The accelerometer may be mounted directly on the pump for example, on the housing of the pump, and in which case it experiences directly accelerations felt by the pump. This may be the case where the motor controller is separate from the pump and in such a case is configured to receive data from the accelerometer mounted on the pump by at least one of a wired and wireless connection.
As noted previously, the motor controller comprises electronic circuitry and this needs to be protected from excessive vibrations and high temperatures. Thus, in some cases it may be appropriate to mount this remotely from the pump to protect it from the conditions that the pump experiences. In such a case, the accelerometer will need to be mounted on the pump so that it experiences the accelerations that the pump experiences and it can transmit data to the processor mounted within the motor controller across wired or wireless connections. Such connections will be present between the motor controller and the pump as the motor controller will need to signal to the pump to control its motor.
In other embodiments, said pump comprises a pump mechanism and a pump housing, and said motor controller is mounted within a housing that is rigidly connected to said pump housing, said accelerometer being mounted within said motor controller housing.
In some cases the motor controller is mounted directly on the housing of the pump and where it is rigidly connected to it, the accelerometer may be mounted within the motor controller itself. At such a location it will both experience the vibrations of the pump and have ease of access to motor controller data.
Although the accelerometer may comprise any detection device for detecting acceleration in at least one axis, in some embodiments it comprises a MEMS device, (a Micro Electro Mechanical System), which can detect acceleration in at least one axis. In some embodiments, a MEMS device which detects acceleration in three orthogonal axes is used. Such a device is a low cost, small, yet accurate device.
Although embodiments are suitable for use with many different types of pumps, in some embodiments the pump comprises a compressor while in other embodiments the pump comprises a vacuum pump.
Vacuum pumps are often manufactured to particularly high tolerances making their use with embodiments of the invention particularly applicable. Compressors suffer from wear of moving parts and differing servicing requirements, such that they benefit from embodiments of the invention.
Embodiments are particularly suitable for use with a turbomolecular vacuum pump as such pumps have a drive fitted to the pump in a way that provides very tight mechanical coupling between the pump mechanism and the motor controller electronics. They are also machined to high accuracy and have a very high rotational speed such that it is important that their bearings remain in good condition and that the rotor is accurately balanced.
In other embodiments, the vacuum pump comprises a dry pump. A dry pump is also suitable for embodiments as such pumps require careful maintenance of their bearings and it is important to know if they are about to fail. Such pumps generate significant vibrations and in this case, the motor controller and processing circuitry for the accelerometer may be mounted remotely from the pump.
In still other embodiments the pump comprises a rotary vane pump.
As noted above, the information from the accelerometer can be used to detect and monitor the condition of the pump and this data can be used to provide warning indicators. The data can also be input to on-board logging systems which are used to determine both use and servicing requirements of the pump. The information can also be used pre and post servicing to determine that the servicing has been correctly performed and has improved the operation of the pump.
A second aspect of the present invention provides a method of analysing data received from an accelerometer mounted on a pump comprising: receiving data output from said accelerometer, receiving motor controller data from a motor controller for controlling a drive motor of said pump; and processing said acceleration data in conjunction with said motor controller data to determine acceleration experienced at said pump due to operation of said pump.
In some embodiments, said step of receiving data output from said accelerometer comprises sampling data signals output from said accelerometer, said sampling being synchronised with at least one type of said motor controller data.
In some embodiments, said step of processing said data comprises correlating said data received from said accelerometer with said motor controller data.
In some embodiments, said motor controller data comprises motor controller data indicative of motor control signals generated by said motor controller.
Alternatively and/or additionally, said motor controller data comprises data received from at least one sensor.
Examples of said motor controller data are at least one of current output to drive said pump, voltage output to drive said pump, temperature and power.
In some embodiments, the method comprises a further step of determining at least one of rotor angular position and rotor speed from said motor controller data.
In some embodiments, the method comprises a further step of generating rotor condition data from said data received from said accelerometer and said at least one of said determined rotor angular position data and said rotor speed.
In some embodiments, the method further comprises converting data from said accelerometer to the frequency domain.
In some embodiments, the method further comprises a comparing step for comparing data output by said accelerometer and processed by said processing circuitry with at least one threshold value; and in response to said at least one threshold being reached generating a corresponding warning signal.
A third aspect of the present invention provides a computer program which when executed by a processor is operable to control said processor to form steps in a method according to a second aspect to the present invention.
Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.
Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.
The Summary is provided to introduce a selection of concepts in a simplified form that are further described in the Detail Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:
Before discussing the embodiments in any more detail, first an overview will be provided.
An acceleration sensor (accelerometer) is embedded in a pump or in its associated motor controller electronics and the acceleration signal is processed within processing circuitry within the motor controller electronics allowing accelerations due to the operation of the pump to be analysed and the condition of the pump determined. Locating the processing circuitry within the motor controller electronics, provides a location that is suitable for such circuitry and allows easy access to the motor control signals, allowing the motor control signals and acceleration signals to be correlated providing improved information on the operation and condition of the pump. The sampling of the acceleration signal may for example be synchronised with the other control processors in the motor controller and specifically with the PWM of the output voltage.
Mounting the accelerometer within the motor controller means that it is in a position that is designed to be suitable for electronic circuitry as it is where the control circuitry of the motor controller is also located and it is also at a location that is convenient for receiving signals indicative of the driving and operation of the vacuum pump. Thus the acceleration signals and the motor control signals may be analysed in combination allowing more detailed and accurate analysis of the pump's operation.
In this embodiment there is a communication link 4 between the motor controller 3 and the pump 1 to provide drive control signals to the vacuum pump motor. This link is also be used to transmit acceleration signals from the accelerometer 5 to the motor controller 3 such that these signals are received at the motor controller and can be processed by processing circuitry 7. Once again, processing circuitry 7 will process the signals from the accelerometer in conjunction with the signals from the motor controller allowing detailed analysis of operation of the vacuum pump to be performed.
In this regard, the combination of motor controller or drive and acceleration signals can be used so that accelerations experienced at particular frequencies can be related to operation of particular elements of the pump such as the bearings or the rotor and can be used to diagnose faults with these elements. Alternatively, the combination can be used to reduce noise in the signals received from the accelerometer and increase accuracy in that way.
Although the pumps shown in
Processing circuitry 7 may process the signals in a number of ways and may include a frequency domain convertor for converting the signals from amplitude versus time to amplitude versus frequency. This allows the peak values of acceleration amplitude at specific frequencies to be determined and these may indicate particular faults within the vacuum pump.
For example where the rotor speed is known, then accelerations detected at a frequency corresponding to this speed may indicate problems with the rotor while accelerations at a frequency corresponding to a factor of this speed may indicate bearing wear. Furthermore, where the angular position of the rotor is known then accelerations related to that position may indicate an unbalanced rotor. This can be useful when balancing the rotor using balancing screws, when the vacuum pump is being made ready for use or as an indicator that servicing is required.
The presence of an accelerometer and processing circuitry which can coordinate with the motor controller circuitry is particularly useful during pump final test and avoids the need of temporarily fitting testing circuitry to every pump that is built and tested. Tests performed involve performing a FFT (Fast Fourier Transform); results input to the threshold comparison circuitry 9 which uses a pass/fail envelope indicate whether the pump is suitable for use or not. The accelerometer may also be used in pre and post service testing where, for example, the field bearings have been changed to check that the pump has not been compromised by the field service operation and that the rotor is still in the correct position.
In addition, during normal operation, any deterioration in the pump condition may be determined from increases in acceleration values at particular frequencies and warning signals can be generated. For example, it may be used to automatically identify when the bearings need changing or to provide some early warning system that they will need replacements soon.
In addition or as an alternative to illuminating warning signals, the signals collected during analysis may also be sent to output 12, where they may be transmitted to the operator or customer to help fault finding. Where there is data logging of vacuum pump operation, the accelerometer may also provide its data to that onboard data logging system and this may be useful in recording the pump running history. This can be advantageous in identifying where particular use of the pumps may have caused damage to the pump. In effect, it may be useful for detecting abuse events where the pump has been misused.
In some embodiments, there is a battery associated with the accelerometer shown as 18 in
In one embodiment, analysis of the accelerations at different frequencies can be used to provide information about the condition of the pump and in particular, the contact angle and hence the preload of the rotor. This can be useful particularly after service when changes in the preload may indicate significant impeller temperature changes, which again are indicative of possible faults.
Examples of the motor controller data that may be combined with the accelerometer data are the rotational frequency measurements which can be used as an input to the final balance process. Phase and magnitude information relating to the rotor position poles from the accelerometer amplitude poles are indicative of the angular position of any unbalance. A plot of the frequency response of the system during coast down or ramp up could also be generated by the processing circuitry and used to detect critical speeds in specific issues like back-up bearing touch or rotor clash in final tests and in pump development. In this regard back-up bearings are provided to limit the movement of the drive shaft away from its normal position.
The above gives some examples of uses of a pump assembly according to an embodiment. It is particularly applicable to turbomolecular pumps as they have a drive fitted to the pump in a way that provides very tight mechanical coupling between the pump mechanism and the motor control electronics. In turbomolecular pump applications, the motor control electronics and the accelerometer are mounted rigidly to the pump as in
As processing circuitry is already present within the motor controller and as low cost accelerometers using MEMS devices are now available, the fitting of an accelerometer and processing device to such pump assemblies is very low cost and can provide much additional data, which may be transmitted to a user using existing serial communication channels.
Embodiments of the present invention which provide transmission of the collected data either wirelessly or via a communication port to a remote location, provide a way of detecting operation of the pumps which can be useful to determine operation issues such as the noisiness of the pump from this remote position. One of the most common complaints for a pump is that it is noisy but this is difficult to quantify and verify the scale of the issue without having a service personnel visit or having the pump returned. Being able to collect data from an accelerometer remotely will provide a useful indication of the size of this problem.
Furthermore, periodically pumps require bearing replacements or other service and it is difficult to predict the correct interval for preventative maintenance as these intervals can vary considerably with the customer application. Monitoring the amplitude and frequency of acceleration peaks could be used to provide early warning that maintenance is really required and also of the nature of the maintenance. This could allow service intervals to be safely extended and could provide early warnings in the cases where the bearing has deteriorated more quickly for whatever reason.
Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.
Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1610244.4 | Jun 2016 | GB | national |
This application is a Section 371 National Stage Application of International Application No. PCT/GB2017/051362, filed May 16, 2017, and published as WO 2017/216514 A1 on Dec. 21, 2017, the content of which is hereby incorporated by reference in its entirety and which claims priority of British Application No. 1610244.4, filed Jun. 13, 2016.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2017/051362 | 5/16/2017 | WO | 00 |
