WO2020039170A1

WO2020039170A1 - Vibration monitors and methods therefor

Info

Publication number: WO2020039170A1
Application number: PCT/GB2019/052317
Authority: WO
Inventors: Leif Anderson; Jacqueline MCLAUGHLIN; Eleanor Barnard
Original assignee: Reactec Limited
Priority date: 2018-08-19
Filing date: 2019-08-19
Publication date: 2020-02-27
Also published as: GB201813493D0

Abstract

A vibration monitor (30) which is configured to be releasably attached to an arm or hand of an operator during use of a power tool.The vibration monitor (30) comprises a vibration sensor (36) and a processor (32). The vibration sensor (36) is operative to sense in at least one axis vibration sustained by the arm or hand of the operator when the vibration monitor (30) is attached to the arm or hand of the operator. The processor (32) receives sensed vibration data from the vibration sensor (36) and applies a transformation to the received vibration data to provide transformed data. The transformed data comprises a predetermined physiological response of at least one person which is obtained by application of the transformation to the received vibration data.The processor (32) also makes a determination on risk of physiological damage to the operator in dependence on the transformed data.

Description

Title of Invention: Vibration monitors and methods therefor

Field of the Invention

The present invention relates to a vibration monitor configured to be attached to the body of an operator during use of a power tool and more specifically, but not exclusively, a vibration monitor configured to be attached to an arm or hand of the operator during use of a power tool. The present invention also relates to a method of monitoring vibration sustained by the body of an operator, and more specifically but not exclusively vibration sustained by an arm or hand of the operator, during use of a power tool.

Background Art

Hand held and hand guided powers tools usually transmit vibration to the hands and arms of a power tool operator. It is known that such transmitted vibration, which is often termed Hand Arm Vibration (HAV), can lead to painful and disabling disease, such as white finger, as a consequence of long-term exposure.

Vibration monitors for monitoring vibration sustained during use of power tools are known. GB 2542027 discloses a vibration monitor that is worn on the wrist of an operator during use of vibrating apparatus. The vibration monitor of GB 2542027 senses vibration, determines vibration exposure risk and provides an exposure risk output in the form of a risk score.

The present inventors have recognised known vibration exposure monitors to have shortcomings. The present invention has been devised in light of the inventors’ appreciation of such shortcomings. It is therefore an object for the present invention to provide an improved vibration monitor which is configured to be releasably attached to an arm or hand of an operator during use of a power tool. It is a further object for the present invention to provide an improved method of monitoring vibration on an arm or hand of an operator during use of a power tool.

Statement of Invention

According to a first aspect of the present invention there is provided a vibration monitor which is configured to be releasably attached to an arm or hand of an operator during use of a power tool, the vibration monitor comprising:

a vibration sensor operative to sense in at least one axis vibration sustained by the arm or hand of the operator when the vibration monitor is attached to the arm or hand of the operator; and

a processor configured: to receive sensed vibration data from the vibration sensor; to apply a transformation to the received vibration data to provide

transformed data, wherein the transformed data comprises a predetermined physiological response of at least one person obtained by application of the transformation to the received vibration data; and to make a determination on risk of physiological damage to the operator in dependence on the transformed data.

The vibration monitor is configured to be releasably attached to an arm or hand of an operator during use of a power tool. The vibration monitor comprises a vibration sensor operative to sense in at least one axis, such as in at least one of x, y and z axes, vibration sustained by the arm or hand of an operator when the vibration monitor is attached to the arm or hand of the operator. In addition, the vibration monitor comprises a processor which is configured, e.g. programmed, to receive sensed vibration data from the vibration sensor. The vibration sensor may provide a sensed vibration output in dependence on sensed vibration, the sensed vibration data corresponding to the sensed vibration output, such as after analogue-to-digital conversion. Alternatively, the vibration sensor may provide the sensed vibration data.

The processor is configured, e.g. programmed, to apply a transformation to the received vibration data to provide transformed data. Furthermore, the processor is configured, e.g. programmed, to make a determination, and more specifically a deduction, on risk of physiological damage to the operator in dependence on the transformed data. A predetermined physiological response of at least one person, who may be the operator wearing the vibration monitor, another person or a plurality of persons, to vibration sustained by the arm or hand of the operator is obtained from application of the transformation to the received vibration data. The transformed data therefore corresponds to the predetermined physiological response.

When a known vibration monitor is used, the vibration sustained by the operator is sensed and vibration exposure is monitored on an ongoing basis during use of a power tool. An exposure risk score is accumulated over time in dependence on the sensed vibration and in accordance with the ISO 5349-2 standard with the risk score being interpreted in light of previously determined outcomes based on statistical analyses of historical epidemiology studies of the effects of vibration on physiology. According to the approach of GB 2542027 vibration is measured on the wrist rather than on the tool. Therefore, and according to GB 2542027, the measured vibration is referred from the wrist to the tool grip point before processing in accordance with the ISO 5349-2 standard. In contrast, the present vibration monitor applies a transformation that relates the received vibration data to a predetermined

physiological response, it being noted that the present vibration monitor measures vibration sustained by the arm or hand of the operator. The present invention therefore dispenses with obtaining a risk score in accordance with the ISO 5349-2 standard and instead involves a more direct approach in which a predetermined physiological response is obtained. The present invention may provide for improved and, perhaps, more accurate vibration exposure monitoring by relating sensed vibration directly to at least one predetermined physiological response. The present invention may provide for monitoring of one or more of a plurality of different physiological responses whereas the known, more blunt approaches provide a vibration exposure risk score which represents physiological response of a general nature.

As mentioned above, the processor is configured to make a determination on risk of physiological damage to the operator in dependence on the transformed data. The determination may be made by comparing the transformed data with predetermined reference data. If the transformed data falls within the scope of the predetermined reference data, such as within a range defined by the predetermined reference data or within a percentage deviation from the predetermined reference data, a

determination may be made of the like of risk of damage and more specifically irreversible damage being sustained. Alternatively or in addition, the determination may be made by proportional comparison of the transformed data with

predetermined reference data to thereby provide a level of risk of physiological damage to the operator.

The vibration sensor may be operative to sense vibration sustained by the arm or hand of the operator at spaced apart times and to provide corresponding plural sensed vibration data. The processor may be configured to receive the plural sensed vibration data and may apply the transformation to the plural sensed vibration data as a whole or to each of the plural sensed vibration data in turn. In addition, the processor may be configured to provide transformed data in the form of a trajectory of risk of physiological damage to the operator. The processor may be further configured to compare the trajectory of risk of physiological damage with a predetermined risk trajectory. The step of making a determination on risk of physiological damage to the operator may be made in dependence on the

comparison with the predetermined risk trajectory. The transformation may relate the received vibration data to a predetermined physiological response of at least one part of the anatomy of the operator. For example, the transformation may relate the received vibration data to a

predetermined physiological response of the fingers or the arm of the operator. As mentioned above, known approaches provide a vibration exposure risk score which represents physiological response of a general nature, such as effect of vibration on the arm and hand of the operator as a whole and without distinguishing between effects on different parts of the arm and hand of the operator.

Furthermore, the transformation of the present invention may relate the received vibration data to a physiological response of each of a plurality of different parts of the arm and hand of the operator. For example, the transformation may relate the received vibration data to a physiological response of the arm and of the fingers of the operator and more specifically of the arm and of each of the fingers of the operator. Different parts of the anatomy, such as different fingers, may be affected to differing extents by vibration sustained by power tool use. An arm and hand risk score obtained from a known approach may be within a safe limit. Flowever, according to the known approach, risk presented to the arm and to the hand with the exception of the fingers may be comfortably within safe limits whereas risk presented to the fingers may be considerably over the safe limit with the low risk in respect of the arm and the low risk in respect of the hand with the exception of the fingers masking the high risk in respect of the fingers.

The predetermined physiological response of at least one person derived from application of the transformation may comprise at least one of: physiological response of the neurological system; physiological response of the cardiovascular system; and physiological response of the musculoskeletal system. The

transformation may be configured accordingly. More specifically, the transformation may relate vibration data to at least one of: physiological response of the

neurological system; physiological response of the cardiovascular system; and physiological response of the musculoskeletal system. The vibration monitor may therefore make a determination on risk of physiological damage to at least one of these physiological systems of the operator.

The predetermined physiological response may comprise physiological response data corresponding to a physiological response per se. For example, where the predetermined physiological response comprises physiological response of the neurological system, the physiological response data may comprise vibrotactile perception threshold data and more specifically vibrotactile temporary threshold shift (TTS) data. TTS after short duration of exposure has been shown to reflect permanent threshold shift after prolonged exposure to vibration and hence to reflect risk of neurological damage.

The transformation may provide for two or more of: physiological response of the neurological system; physiological response of the cardiovascular system; and physiological response of the musculoskeletal system. The vibration monitor may therefore make a determination on risk of physiological damage to the operator in respect of each of plural different physiological systems of the operator. An arm and hand risk score obtained from a known approach may be within a safe limit.

However, according to the known approach, risk presented to a first physiological system of the operator’s arm and hand, such as the neurological system, may be comfortably within a safe limit whereas risk presented to a second physiological system of the operator’s arm and hand, such as cardiovascular system, may be considerably over the safe limit with the low risk in respect of the first physiological system masking the high risk in respect of the second physiological system.

The transformation may be obtained by a calibration process comprising determining a relationship between vibration sustained by at least one person and data on physiological response of at least one person to vibration. The relationship may be determined where the at least one person is the operator who will be using the vibration monitor. The vibration monitor may therefore be calibrated for a particular operator. Calibration for a particular operator may be carried out during a calibration phase prior to use of a power tool. Alternatively or in addition, calibration for a particular operator may be after ongoing use of the power tool has started whereby the transformation is, for example, adapted during ongoing power tool use to take account of physiological changes to the operator.

The calibration process may comprise acquiring by way of measurement apparatus data on physiological response of at least one person to vibration. More specifically, the data on physiological response may be for plural persons. The calibration process may comprise subjecting the at least one person to different frequencies of vibration and acquiring data on physiological response at each of different frequencies. In addition, the at least one person may be subject to different magnitudes of vibration. The transformation relating the received vibration data to the predetermined physiological response may be operative in respect of plural frequencies of vibration and respective amplitudes of vibration. The measurement apparatus may be operative to acquire data on at least one of physiological response of the neurological system; physiological response of the vascular system; and physiological response of the musculoskeletal system.

The measurement apparatus may perform analysis of at least one person’s blood and/or relevant tissues. The analysis may comprise analysis of at least one biomarker, such as blood ion concentration. Analysis of blood ion concentration may provide for determination of endothelial cell function and/or smooth muscle cell function. The ability of endothelial cells to regulate vasoconstriction is an indicator of a compromised vascular system.

The measurement apparatus may measure blood flow in the skin. The

measurement apparatus may be operative by imaging, such as by way of laser doppler imaging or magnetic resonance angiography, or more specifically by optical imaging, such as by way of optical coherence tomography or Nailfold capillaroscopy.

The measurement apparatus may determine physiological response of the neurological system. The measurement apparatus may therefore comprise at least one of a thermal aesthesiometer and a vibrotactile perception meter.

Physiological response data may comprise at least one of: neurological system response data; cardiovascular system response data; and musculoskeletal system response data. Such system response data may be obtained by the measurement approaches described above, such as during a calibration process. The

physiological response data may therefore comprise at least one of: blood composition data; blood flow data; thermal aesthesiometer data; and vibrotactile perception data.

The step of making a determination on risk of physiological damage to the operator may be made in dependence on at least one factor of the operator which is not measured or ascertained by the vibration monitor. The factor may be a genetic factor, for example race, sex or predisposition to a medical condition, such as Raynaud’s disease. The factor may be a lifestyle factor, for example whether or not and the extent to which the operator smokes or drinks alcohol. The factor may be a medical factor, for example presence of high blood pressure or diabetes. The factor may be a physiological factor, for example, body mass index or age. The at least one factor may be used to adjust risk of physiological damage determined on the basis of the vibration data. More specifically, and in view of many of the examples of factors given above predisposing an operator to physiological damage, the at least one factor may be used to increase the determined risk of physiological damage.

The at least one factor may be used in the step of making a determination on risk of physiological damage to the operator. Alternatively or in addition, the at least one factor may be comprised in the transformation whereby the at least one factor is applied upon application of the transformation to the received vibration data.

The processor may be configured, e.g. programmed, to transform time domain output from the vibration sensor to a frequency domain signal. The processor may be configured to perform a Fourier transform and more specifically an overlapping windowed Fourier transform, such as Welch’s method. The processor may be configured to form plural frequency bands, the frequency bands being between 500 and 1300, between 700 and 1100 or between 800 and 1000. For example, there may be 896 frequency bands. The lower limit of the frequency bands may be 0 Hz,

1 Hz, 2 Hz, 3 Hz, 4 Hz, 5 Flz or 6 Hz. The upper limit of the frequency bands may be 500 Hz, 600 Hz, 700 800 Hz or 900 Hz. A Power Spectral Density (PSD) may be determined in dependence on the frequency domain signal. Furthermore, an energy value may be determined by integration over a predetermined interval. For example, the energy value may be determined in respect of the frequency range 0 Hz to 650 Hz.

Alternatively or in addition, the processor may be configured, e.g. programmed, to apply the transformation in the time domain. Processing described herein may be performed entirely in the time domain. Time domain processing may be appropriate where the processor is of sufficient capability.

The processor may be configured to determine a time remaining for use of a power tool in dependence on the determination on risk of physiological damage to the operator. The time remaining for use may be determined further in dependence on at least one previous determination on risk of physiological damage, such as in respect of the same power tool or a different power tool. For example, the vibration monitor may store an accumulation of risk determinations, such as in the form of a level of risk, and upon start of use of a power tool, the vibration monitor may provide a time remaining for use of the power tool which takes into account the accumulation of risk and the current risk exposure during use of the present power tool. The time remaining for use may be displayed to the operator, such as by way of a display comprised in the vibration monitor, or conveyed to a remote location whereby another party is apprised of the operator’s present status vis-a-vis the time remaining for use. The processor may be configured to decrement the time remaining for use in dependence on ongoing determinations.

The vibration monitor may be configured to be attached and more specifically releasably attached to the operator. The vibration monitor may be configured to be attached to the arm and more specifically to the wrist of the operator. The vibration monitor may have the form of a wrist watch. The vibration monitor may therefore comprise an attachment device, such as a strap or a band, whereby the vibration monitor may be attached to the arm and more specifically the wrist. The attachment device may be configured such that vibration is coupled properly to the vibration monitor and more specifically vibration in a relevant frequency band is coupled to the vibration monitor. The attachment device may be configured such that it is substantially inelastic when the vibration monitor is attached to the operator. The vibration monitor may comprise a housing. The housing may contain the vibration sensor and the processor. The attachment device may be attached to an exterior of the housing. The housing may be formed at least in part of a substantially rigid material whereby vibration is coupled from the operator to the vibration sensor. The housing may be formed at least in part from a plastics material, such as PC- ABS.

The vibration monitor may comprise a data store, such as data memory which may be comprised in the processor, which stores the transformation. The vibration sensor may comprise a tri-axial vibration sensor. The transformation may therefore be applied to the received vibration data in three axes and more specifically to vibration data in three mutually orthogonal axes. The vibration sensor may comprise an accelerometer. The processor may comprise a microcontroller. Alternatively or in addition the processor may comprise electronic circuitry further to or instead of a microcontroller, the electronic circuitry being configured to perform processes described herein. The vibration monitor may therefore comprise circuits having structures and/or non-transitory memory having programmed instructions to perform these processes.

The vibration monitor may comprise an analogue to digital converter which is operative to sample an output for each of at least one of the first to third axes from the vibration sensor. The analogue to digital converter may be operative to sample an output from the vibration sensor at a rate of at least 1 kHz, 2 kHz, 4 kHz, 6 kHz or 8 kHz. The analogue to digital converter may be operative to sample an output from the vibration sensor at a rate of no more than 10 kHz.

The vibration monitor may comprise a display, such as an LCD display. The LCD display may be supported by the housing. The vibration monitor may be configured to display vibration exposure as determined by the vibration monitor in accordance with the known approach. Alternatively or in addition, the vibration monitor may be configured to display level of risk of physiological damage to the operator or indication of a predetermined level of risk of physiological damage having been exceeded. Alternatively or in addition, the vibration monitor may comprise at least one of: an audible output device, such as a buzzer, operable to provide an audible output; and an output device, such as a vibrating motor, operable to provide an output susceptible to pallesthesia. The processor may be configured to operate such an output device in dependence on determined vibration exposure or level of risk of physiological damage to the operator. For example, an output device may be operated when a predetermined vibration exposure limit is reached, such as a daily vibration exposure limit, or when a certain level of risk of physiological damage is reached.

The vibration monitor may be configured for communication of data, such as vibration exposure data, from the vibration monitor. The data may be communicated wirelessly. More specifically, the vibration monitor may be received in a holder when not in use on an operator. The holder may be configured to receive plural vibration monitors. The holder may be configured for communication of data and more specifically wireless communication of data between the holder and the vibration monitor. Data on risk of physiological damage to the operator or vibration exposure data may thus be conveyed to the holder with the holder being configured to convey the received vibration exposure data to computing apparatus, which may be at a location remote from the holder. Vibration exposure data may be stored in the computing apparatus. The computing apparatus may provide for analysis of stored vibration exposure data.

According to a second aspect of the present invention there is provided a method of monitoring vibration sustained by an operator during use of a power tool, the method comprising:

releasably attaching a vibration monitor comprising a vibration sensor to an arm or hand of the operator;

sensing vibration sustained by an arm or hand of the operator in at least one axis by way of the vibration sensor when the vibration monitor is attached to the arm or hand of the operator;

receiving sensed vibration data from the vibration sensor in a processor, the processor being programmed to apply a transformation to the received vibration data to provide transformed data, the transformed data comprising a predetermined physiological response of at least one person obtained by application of the transformation to the received vibration data; and

determining in the processor risk of physiological damage to the operator in dependence on the transformed data.

The method may further comprise the processor being programmed to at least one of: store in the vibration monitor the determined risk of physiological damage; and output, such as by displaying, the determined risk of physiological damage.

Further embodiments of the second aspect of the present invention may comprise one or more features of the first aspect of the present invention.

According to a further aspect of the present invention there is provided a vibration monitor which is configured to be releasably attached to a limb of an operator during use of a power tool, the vibration monitor comprising: a vibration sensor operative to sense in at least one axis vibration sustained by the limb of the operator when the vibration monitor is attached to the limb of the operator; and a processor configured: to receive sensed vibration data from the vibration sensor; and to make a

determination on risk of physiological damage to the operator in dependence on the received vibration data. Embodiments of the further aspect of the present invention may comprise one or more features of the first aspect of the present invention.

According to a yet further aspect of the present invention there is provided a method of monitoring vibration sustained by an operator during use of a power tool, the method comprising: releasably attaching a vibration monitor comprising a vibration sensor to a limb of the operator; sensing vibration sustained by the limb of the operator in at least one axis by way of the vibration sensor when the vibration monitor is attached to the limb of the operator; receiving sensed vibration data from the vibration sensor in a processor and determining in the processor risk of physiological damage to the operator in dependence on the received vibration data. Embodiments of the yet further aspect of the present invention may comprise one or more features of the first aspect of the present invention. Brief Description of Drawings

Further features and advantages of the present invention will become apparent from the following specific description, which is given by way of example only and with reference to the accompanying drawings, in which:

Figure 1 shows a vibration monitor according to an embodiment of the present invention in situ;

Figure 2 is a block diagram representation of the embodiment of Figure 1 ;

Figure 3 is a flow chart setting out the main steps involved in calibration and operation of the vibration monitor of Figure 1 ; and

Figure 4 is a representation of a calibration process.

Description of Embodiments A vibration monitor 10 according to an embodiment of the present invention is shown in situ on the wrist of a power tool operator. The vibration monitor 10 comprises a housing 12 having the general form of rectangular cuboid and a strap 14 attached to the housing whereby the vibration monitor 10 may be attached to the wrist of the operator in the manner of a wrist watch. A face of the housing 12 defines a rectangular window 16 through which an LCD display may be seen by the operator. An embodiment of the vibration monitor 10 of Figure 1 comprises a user operable on-off switch whereby the vibration monitor may be turned off to stop recording vibration at inappropriate times, such as when the operator is driving. The vibration monitor 30 is represented in block diagram form in Figure 2. The vibration monitor 30 comprises a microcontroller 32, namely an Atmel ARM Cortex M4 SAM4LS with 512K of flash memory, an LCD 34, which is driven by the microcontroller 32 by way of a i2c bus, a tri-axial accelerometer 36 (which constitutes a vibration sensor), namely an ST Microelectronics MEMS LIS3DSHTR, and an RFID transceiver 38, namely an NXP 13.56MHz CLRC66301 HN/TR having multiple protocol support. Each of the accelerometer 36 and the RFID transceiver 38 communicates with the microcontroller 32 by way of an SPI bus. The accelerometer 36 comprises an analogue to digital converter. The design of the vibration monitor 30 in respect of the microcontroller 32, the LCD 34, the accelerometer 36 and the RFID transceiver 38 is within the ordinary design capabilities of the person skilled in the art. The vibration monitor 30 further comprises a buzzer 40 and a vibration motor 42 which are operative under control from the microcontroller 32 to provide a warning of different sensory forms when vibration exposure exceeds a

predetermined level or risk of physiological damage exceeds a predetermined level. The design of the vibration monitor 30 in respect of the buzzer 40 and the vibration motor 42 is within the ordinary design capabilities of the person skilled in the art. The vibration monitor 30 yet further comprises a rechargeable battery 44, battery protection circuitry 46, galvanically isolated communications circuitry 48, an on-off switch 50, power supply circuitry 52 and a temperature sensor 56. The design of the vibration monitor 30 in respect of these components is within the ordinary design capabilities of the person skilled in the art. A docking station 54 is represented in Figure 2. The docking station 54 is configured to hold plural vibration monitors 30 in respective bays formed in the docking station 54. When received in the docking station 54 the rechargeable battery 44 of the vibration monitor 30 is charged by way of a copper connection between the docking station 54 and the vibration monitor 30. The communications circuitry 48 of the vibration monitor 30 provides for

communication of data between the vibration monitor 30 and the docking station 54. Data communicated to the docking station 54 includes the like of vibration exposure data, data on risk of physiological damage, and Power Spectral Density (PSD) data stored in the vibration monitor 30 during use thereof. Such data is stored for compliance and record keeping purposes and further analysis of power tool usage if such is required. Data communicated to the vibration monitor 30 from the docking station 54 includes the like of vibration exposure thresholds, risk of physiological damage thresholds and other configuration data for the vibration monitor 30 and provides for clearing of data memory within the vibration monitor 30 such as data memory used to store vibration exposure data, operator exposure data and PSD data. The power supply circuitry 52 comprises a regulator and a DC/DC converter which are operative to draw current from the rechargeable battery 44 and provide electrical power of appropriate voltage to each of the buzzer 40 and the vibration motor 42. The on-off switch 50 enables the operator to turn the vibration monitor 30 on and off. The temperature sensor 56 is operative to sense the temperature of the rechargeable battery 44 during charging and to convey the sensed temperature to the docking station 54. Damage to the rechargeable battery 44 may occur if the temperature of the rechargeable battery 44 rises above a threshold temperature. The docking station 54 is therefore configured to cease charging of the rechargeable battery 44 if the sensed temperature rises above a threshold temperature.

A vibration monitoring arrangement according to an embodiment of the present invention comprises the vibration monitor 30 of Figures 1 and 2 and an RFID tag (not shown). Power tool data is stored in the RFID tag and the RFID tag is brought into use by being attached by way of adhesive to a power tool. The power tool data comprises an identification code for the power tool, a noise rating for the power tool and a weight of the power tool. The noise rating provides for determination of exposure of the operator to noise based on length of time of use of the power tool. The weight of the power tool provides a basis for determining physical stress of the user on account of bearing the weight of the power tool during use. A vibration monitoring arrangement according to another embodiment of the present invention comprises the vibration monitor 30 of Figures 1 and 2 but lacks the RFID tag. Operation of the vibration monitor 30 of Figure 2 will now be described with reference to the flow chart of Figure 3 and the representation of a calibration process shown in Figure 4.

Before use of the vibration monitor 30, the transformation of the vibration monitor 30 is formed by way of a calibration process. The calibration process involves taking physiological measurements of each of plural subjects who have been subject to vibration or are sustaining vibration 72. The physiological measurements comprise one or more of the following. Analysis of blood ion concentration to determine endothelial cell function. Measurement of blood flow in the skin by way of at least one of laser doppler imaging, magnetic resonance angiography, optical coherence tomography and Nailfold capillaroscopy. Measurement of response of the

neurological system by way of at least one of thermal aesthesiometry; vibrotactile perception measurement; and digital plethysmography. Correspondence between the physiological measurement data and vibration exposure is then determined 74. Then the transformation is formed to reflect the correspondence between the physiological measurement data and vibration exposure 76. The transformation is stored in the vibration monitor. For the most part, the physiological measurements described above involve longer term studies to provide for correspondence between physiological effect, physiological measurements and vibration exposure.

Vibrotactile perception measurement is an example of a physiological measurement that requires no such longer term studies. Calibration involving vibrotactile perception measurement is now described with reference to Figure 4. Each person of a group of persons grips a source of vibration which is controllable in respect of magnitude and frequency of vibration 102. A vibration sensor is used to measure vibration, Ax, at the wrist of the person gripping the source of vibration. The person is subject to vibration at a first frequency, x, for a predetermined time. After exposure to vibration for the predetermined time, the person is subject to vibrotactile perception measurement 104. More specifically, the vibrotactile temporary threshold shift (TTS), Rx, arising from the vibration exposure is determined to thereby provide the relationship between vibration, Ax, at the first frequency, x, and the TTS, Rx, which reflects the physiological effect of exposure to vibration at the first frequency. The transformation coefficient at frequency x is Tx, where Tx is a function of the relationship between Ax and Rx. In its simplest form Tx = 1/(Ax/Rx). This process is repeated at plural different frequencies across a frequency spectrum of interest 106 whereby the relationship between vibration and TTS is determined across the frequency spectrum and the transformation is formed accordingly.

The vibration monitor is brought into use by being attached to the operator’s wrist 78. During use of a power tool, the vibration monitor senses vibration sustained by the operator 80. The sensed vibration is sampled 82. The sampled sensed vibration is converted to the frequency domain 84. The stored transformation is applied by the microcontroller 32 to the frequency domain converted vibration data to provide transformed data 86. The risk of physiological damage to the operator is determined in the microcontroller 32 in dependence on the transformed data 88. In a first approach, determination of risk is by comparing the transformed data with predetermined reference risk data. If the transformed data falls within the scope of the predetermined reference data, a positive risk determination is made. In a second approach, the determination is made by proportional comparison of the transformed data with predetermined reference data to thereby provide a level of risk of physiological damage to the operator. In a third approach, the transformed data has the form of a trajectory over time based on vibration measurements taken over time. In this approach, the trajectory formed by the transformed data is compared with a predetermined risk trajectory.

In a form of the vibration monitor 10, plural different factors of the operator which are not measured or ascertained by the vibration monitor are used to adjust the risk of physiological damage to the operator. The plural different factors are: genetic factors; lifestyle factors; medical factors; and physiological factors. Genetic factors include the operator’s race, sex and predisposition to medical conditions, such as Raynaud’s disease. The lifestyle factors include whether or not and the extent to which the operator smokes or drinks alcohol. The medical factors include whether or not the operator has high blood pressure or diabetes and the severity thereof. The physiological factors include the body mass index and age of the operator.

According to one approach, the plural different factors are used to adjust the determination on risk of physiological damage as determined on the basis of vibration measurement. Each factor may have a respective weighting which increases or, in some cases, reduces risk. For example, and where the calibration process has been carried out with plural subjects such that the transformation represents median characteristics, a higher than median age for the operator provides for an increase in risk and, conversely, a lower than median age for the operator provides for a reduction in risk. According to another approach, the plural different factors are applied by way of the transformation. More specifically, the transformation comprises at least one weighting factor representing the plural different factors to thereby provide for adjustment based on the plural different factors. Following the risk determination, data relating to risk is stored in the vibration monitor 90. The vibration monitor is operative to display a level of risk to the operator based on the data relating to risk. As the operator continues to use the power tool, the level of risk is updated with need to cease use of the power tool being intimated to the operator by way of a warning of the different sensory forms described above.

Further to this, the vibration monitor is operative to display a time remaining for safe use of the power tool being used presently by the operator. The time remaining for safe use is the time left for use of the power tool before the like of a daily level of risk is reached. The time remaining for safe use is calculated based on accumulated risk determinations and determinations made during use of the present power tool. The time remaining for safe use is decremented as more use is made of the present power tool.

Claims

1. A vibration monitor which is configured to be releasably attached to an arm or hand of an operator during use of a power tool, the vibration monitor comprising: a vibration sensor operative to sense in at least one axis vibration sustained by the arm or hand of the operator when the vibration monitor is attached to the arm or hand of the operator; and

2. The vibration monitor according to claim 1 , wherein the determination on risk of physiological damage to the operator is made by comparing the transformed data with predetermined reference data.

3. The vibration monitor according to claim 1 or 2, wherein the vibration sensor is operative to sense vibration sustained by the arm or hand of the operator at spaced apart times and to provide corresponding plural sensed vibration data, the processor configured to receive the plural sensed vibration data and to apply the transformation to the plural sensed vibration data.

4. The vibration monitor according to claim 3, wherein the processor is configured to provide transformed data in the form of a trajectory of risk of physiological damage to the operator.

5. The vibration monitor according to claim 4, wherein the processor is further configured to compare the trajectory of risk of physiological damage with a predetermined risk trajectory, the step of making a determination on risk of physiological damage to the operator being made in dependence on the comparison with the predetermined risk trajectory.

6. The vibration monitor according to any one of the preceding claims, wherein the transformation relates the received vibration data to a predetermined

physiological response of each of a plurality of different parts of the arm and hand of the operator.

7. The vibration monitor according to any one of the preceding claims, wherein the transformation relates vibration data to at least one of: predetermined

physiological response of the neurological system; predetermined physiological response of the cardiovascular system; and predetermined physiological response of the musculoskeletal system, the processor making a determination on risk of physiological damage to at least one of these physiological systems of the operator.

8. The vibration monitor according to claim 7 and where the predetermined physiological response comprises the predetermined physiological response of the neurological system, the predetermined physiological response comprises

physiological response data, the physiological response data comprising vibrotactile temporary threshold shift (TTS) data.

9. The vibration monitor according to any one of the preceding claims, wherein the transformation relates vibration data to at least two of: predetermined

physiological response of the neurological system; predetermined physiological response of the cardiovascular system; and predetermined physiological response of the musculoskeletal system, the processor making a determination on risk of physiological damage to the operator in respect of each of the at least two

physiological systems of the operator.

10. The vibration monitor according to any one of the preceding claims, wherein the transformation is obtained by a calibration process comprising determining a relationship between vibration sustained by at least one person and data on physiological response of the at least one person to vibration.

11. The vibration monitor according to claim 10, wherein the relationship is determined where the at least one person is the operator who will be using the vibration monitor.

12. The vibration monitor according to claim 11 , wherein calibration for a particular operator is after ongoing use of the power tool has started whereby the transformation is adapted during ongoing power tool use to take account of physiological changes to the operator.

13. The vibration monitor according to any one of claims 10 to 12, wherein the calibration process comprises acquiring by way of a measurement apparatus data on physiological response of at least one person to vibration, the calibration process comprising subjecting the at least one person to different frequencies of vibration and acquiring data on physiological response at each of different frequencies, the data being acquired by way of the measurement apparatus.

14. The vibration monitor according to claim 13, wherein the measurement apparatus performs analysis of the at least one person’s blood and/or body tissues.

15. The vibration monitor according to claim 14, wherein the analysis comprises analysis of blood ion concentration.

16. The vibration monitor according to any one of claims 13 to 15, wherein the measurement apparatus measures blood flow in the skin of the at least one person.

17. The vibration monitor according to any one of claims 13 to 16, wherein the measurement apparatus determines physiological response of the neurological system of the at least one person, the measurement apparatus comprising at least one of a thermal aesthesiometer and a vibrotactile perception meter.

18. The vibration monitor according to any one of the preceding claims, wherein the step of making a determination on risk of physiological damage to the operator is made in dependence on at least one factor of the operator which is not measured or ascertained by the vibration monitor.

19. The vibration monitor according to claim 18, wherein the at least one factor comprises at least one of: a genetic factor; a lifestyle factor; a medical factor; and a physiological factor.

20. The vibration monitor according to claim 18 or 19, wherein the at least one factor is used to adjust risk of physiological damage determined on the basis of the vibration data.

21. A method of monitoring vibration sustained by an operator during use of a power tool, the method comprising: