VIBRATION DOSE MEASUREMENT APPARATUS

Abstract

A vibration dose measurement apparatus 10 for an operator's hand 1 comprises a sensing assembly 20 connected to a control unit 25. The sensing assembly 20 comprises an accelerometer 21, gyroscope 22, and gripping force sensor 23 and may be packaged within a protective housing (not shown). By monitoring output of the sensor assembly 20, the vibration dose experienced by the hand 1 can be estimated. In the present invention, the provision of gripping force sensor 23 allows for vibration dose measurement to be adjusted based on the output of gripping force sensor 23. This can therefore take into account the force applied by an operator in gripping machinery, which can impact significantly on the effective vibration dose.

Claims

1. A vibration dose measurement apparatus suitable for use by a machine operator, the apparatus comprising: a sensor assembly; and a support operable, in use, to urge the sensor assembly toward the palm of the operator wherein the sensor assembly comprises an accelerometer operable to detect linear motion; a gyroscope operable to detect rotary motion; and a gripping force sensor operable to detect gripping force applied by the operator.

2. (canceled)

3. (canceled)

4. A vibration dose measurement apparatus as claimed in claim 1 wherein the support is integrated into a glove or gauntlet.

5. (canceled)

6. A vibration dose measurement apparatus as claimed in claim 1 wherein the support comprises an inner surface which faces toward the operator's hand in use and an outer surface that faces away from the operator's hand in use, the inner surface lined with fabric.

7. A vibration dose measurement apparatus as claimed in claim 1 wherein the support comprises a sensor pocket adapted to accommodate a sensing assembly defined by the accelerometer, gyroscope and gripping force sensor.

8. A vibration dose measurement apparatus as claimed in claim 1 wherein the gripping force sensor is a force-sensing resistor.

9. A vibration dose measurement apparatus as claimed in claim 8 wherein the gripping force sensor is bonded to a mounting substrate housed within the pocket.

10. (canceled)

11. A vibration dose measurement apparatus as claimed in claim 1 wherein the apparatus comprises a processor connected to the outputs of the accelerometer, gyroscope and gripping force sensor, the processor operable to receive and process output signals from the accelerometer, gyroscope and gripping force sensor so as to determine whether a safe vibration dose is exceeded.

12. A vibration dose measurement apparatus as claimed in claim 11 wherein the vibration dose is be the A(8) value.

13. A vibration dose measurement apparatus as claimed in claim 12 wherein the vibration dose is calculated based on a modified A(8) value including an additional term derived from the gripping force sensor output.

14. (canceled)

15. A vibration dose measurement apparatus as claimed in claim 11 wherein the apparatus comprises a dose indicator operable in response to the processor to output an indication when it is determined that a safe vibration dose is exceeded.

16. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

20. A vibration dose measurement apparatus as claimed in claim 1 wherein the apparatus comprises a visual sensor operable to capture a series of images of the operator's skin.

21. A vibration dose measurement apparatus as claimed in claim 20 wherein the visual sensor or the processor is operable to apply spatial decomposition and temporal filtering to captured images so as to provide an output indicative of the operator's blood flow.

22. A vibration dose measurement apparatus as claimed in claim 21 wherein the processor is operable to determine that a safe vibration dose is exceeded if a pulse rate or blood mass flow rate falls outside a safe threshold range.

23. A vibration dose measurement apparatus as claimed in claim 21 wherein the processor is operable to compare current visual sensor output to a stored visual sensor output for a particular operator.

24. A method of monitoring the vibration dose experienced by a machine operator, the method comprising the steps of: providing the operator with a vibration dose measurement apparatus comprising: a sensor assembly; and a support operable, in use, to urge the sensor assembly toward the palm of the operator wherein the sensor assembly comprises an accelerometer operable to detect linear motion; a gyroscope operable to detect rotary motion; and a gripping force sensor operable to detect gripping force applied by the operator; monitoring the vibration dose detected by the apparatus; and outputting a warning if the detected dose exceeds a threshold.

25. A method as claimed in claim 24 wherein the vibration dose the vibration dose is calculated based on a modified A(8) value including an additional term derived from the gripping force sensor output.

26. A method as claimed in claim 24 wherein a visual sensor s operable to capture images so as to determine an operator's pulse rate or blood mass flow rate and it is determined that a safe vibration dose is exceeded if a pulse rate or blood mass flow rate falls outside a safe threshold range

27. A method as claimed in claim 24 including the step of outputting a shut down signal to a machine where a vibration dose threshold is exceeded.

28. A method as claimed claim 24 including the step of storing vibration dose data relating to particular operator and/or machines.

29. A method as claimed in claim 28 including the additional step of comparing vibration dose data to stored vibration dose data to identify potential problems.

30. (canceled)

Description

DETAILED DESCRIPTION OF THE INVENTION

[0036] In order that the invention may be more clearly understood embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

[0037] FIG. 1 is a schematic block diagram of the vibration dose measurement apparatus of the present invention;

[0038] FIG. 2 is a schematic exploded diagram of a first embodiment of the vibration dose measurement apparatus of the present invention;

[0039] FIG. 3 shows (a) upper, (b) side and (c) lower views of the gauntlet support of the embodiment of FIG. 2;

[0040] FIG. 4 shows an alternative embodiment of a vibration dose measurement apparatus according to the present invention;

[0041] FIG. 5a shows another alternative embodiment of a vibration dose measurement apparatus according to the present invention;

[0042] FIG. 5b shows the vibration dose measurement apparatus of FIG. 5a fitted to the hand of a machine operator;

[0043] FIG. 6 shows a further alternative embodiment of a vibration dose measurement apparatus according to the present invention; and

[0044] FIG. 7 shows a still further alternative embodiment of a vibration dose measurement apparatus according to the present invention.

[0045] Turning to FIG. 1, a vibration dose measurement apparatus 10 for an operator's hand 1 comprises a sensing assembly 20 connected to a control unit 25. Optionally, as is shown in FIG. 1, a separate visual sensor 24 may additionally be provided.

[0046] The sensing assembly 20 comprises an accelerometer 21, gyroscope 22, and gripping force sensor 23 and may be packaged within a protective housing (not shown). The accelerometer 21 and gyroscope 22 allow linear movement, rotational movement and orientation of the sensor assembly 20 to be detected. By monitoring the magnitude and direction of this movement, as well as the orientation of the sensor assembly 20, the vibration dose experienced by the sensor assembly 20 can be determined and hence the vibration dose received by the hand 1 can be estimated.

[0047] The accelerometer 21 and gyroscope 22 are typically MEMS devices. Optionally, a combined MEMS accelerometer and gyroscope can be used in place of separate dedicated sensors.

[0048] The gripping force sensor 23 is typically a force-sensing resistor. The gripping force sensor 23 is mounted to a substrate, typically a printed circuit board upon which the accelerometer 21 and gyroscope 22 are also mounted. As will be described in more detail below, the gripping force sensor 23 is positioned so as to experience force applied by the gripping force of the operator's hand 1. The force applied by the hand 1 can be taken into account either in calculating the vibration dose experienced by the hand 1 or in calculating a safe vibration dose threshold.

[0049] In the example of FIG. 1, the control unit 25 comprises a processor 26, a communication unit 27 and an optional data storage unit 28. Typically, each said component is mounted on a common printed circuit board. In many instances, the control unit will optionally further incorporate a power source such as a battery (not shown)

[0050] The processor 26 is operable to receive the outputs from sensors 21-24, typically by way of a common cable 30. These sensor outputs are typically processed by the processor 26 in order to determine the vibration dose and to determine whether or not the vibration dose exceeds a safe threshold. Alternatively, the sensor outputs can simply be collated by the processor 26 and passed to the communication unit 27.

[0051] Determination of vibration does may be carried out by calculating a conventional A(8) value as is known in the art. In this context:

[00001]$\begin{array}{cc}A\left(8\right)=a_{h.Math.v}.Math.\sqrt{\frac{T}{T_o}}& \left(1\right)\end{array}$

where a.sub.hv is the total vibrational vector characterising a particular vibration, T is time that an operator is exposed to the vibration characterised by a.sub.hv and T.sub.o is a reference time value. Typically T.sub.o may be defined by reference to a working shift, say 8 hours (28,800 seconds. The value of a.sub.hv can be determined from the outputs of accelerometer 21 and gyroscope 22. In particular, the value of a.sub.hv may be determined from the square root of the sum of the root mean square (RMS) values of orthogonal vector components a.sub.f. More particularly

[00002]$\begin{array}{cc}{a}_{h.Math.v}=\sqrt{a_{\mathrm{fx}}^2+a_{\mathrm{fy}}^2+a_{\mathrm{fz}}^2}.Math..Math.\mathrm{and}& \left(2\right)\\ a_{\mathrm{fx},y,z}={\left(\frac{1}{T}.Math.{\int }_0^T.Math.a_{\mathrm{fx},y,z}^2\left(t\right).Math.\mathrm{dt}\right)}^{1/2}& \left(3\right)\end{array}$

[0052] In the present invention, the provision of gripping force sensor 23 allows for vibration dose measurement to be adjusted based on the output of gripping force sensor 23. This can therefore take into account the force applied by an operator in gripping machinery, which can impact significantly on the effective vibration dose. This can be achieved by adding an additional term to equation (1) above when calculating vibration dose. accordingly, vibration dose is calculated from

[00003]$\begin{array}{cc}A\left(8\right)=a_{h.Math.v}.Math.\sqrt{\frac{T}{T_o}}+\frac{V_{E.Math.T}.Math.T}{\rho .Math.A_s.Math.A_h}& \left(4\right)\end{array}$

Where V.sub.ET is the vibrational energy transmitted, which can be determined from the output of the gripping force sensor 23; ρ is the density of the operator's palm skin tissue (typically ˜110 kgm.sup.−3); A.sub.s is the area of the operator's skin in contact with the machinery; and A.sub.h is the area of the handle of the machinery. Typically, ρ, A.sub.s and A.sub.h may be treated as constants for specific operator/machinery combinations. In some embodiments, A.sub.s may be varied in response to orientation. this would reflect a difference in grip of the handle by the operator. In this context, the vibrational energy transmitted V may be calculated from the measured gripping force F by:

V.sub.ET=F∫a.sub.hvdt   (5)

[0053] In embodiments where the processor is operable to determine whether a safe vibration dose is exceeded, the apparatus 1 is provided with an optional output indicator 29, which may comprise one or more LEDs. If a safe vibration dose is exceeded, the output indicator can provide the operator with a suitable indication, such as switching on a red LED or the like.

[0054] The communication unit 28 is operable to communicate data with one or more external devices 40. This data may include data relating to the outputs of sensors 21-24. In embodiments where the processor 26 is operable to calculate a vibration dose and/or whether the vibration dose exceeds a safe threshold, the communication unit 27 may additionally communicate this data to one or more external devices 40.

[0055] The external devices 40 may include a personal device associated with the operator, such as a smartphone, or the machine that is being operated. In the case of a smartphone this may be adapted to work with the apparatus by downloading a dedicated software application. This thus allows the operator to have access to a personal record of vibration exposure. Additionally or alternatively, the smartphone may be operable to output an alarm if the vibration dose exceeds a safe threshold. In the case of a machine, in addition to outputting a local alarm to the operator, the machine may output an alarm to the operator's supervisor and/or automatically shut down.

[0056] In some embodiments, the external device 40 is a computer or server providing operator vibration dose monitoring. Such a computer or server may automatically generate alarms if a safe vibration dose is exceeded and/or output a shutdown signal to a machine where an operator has exceeded a safe vibration dose. Additionally or alternatively, such a computer or server can maintain records of vibration dose exposure for multiple operators. This can allow audits of vibration dose to take place in the future. Stored vibration dose data may also enable comparisons of vibration dose experienced by different operators to be made. This could help identify operators in need of further training. Stored vibration dose data may also be compared to quality analysis of work completed using particular machines. Unusual vibration readings may indicate that a machine requires servicing or that an operator is operating a machine unsafely or has become fatigued.

[0057] In embodiments, comprising the optional a visual sensor 24, this would typically comprise a camera 8 mounted adjacent to the operator's wrist where there are blood vessels readily visible beneath the skin. The visual sensor 24 is operable to capture a series of images of the operator's skin. Subsequently, spatial decomposition and temporal filtering is applied to the captured images so as to provide an indication of pulse rate and/or blood mass flow rate immediately below the skin. The pulse rate and/or blood mass flow rate can be taken into account in determining the apparent vibration dose experienced by the operator or in calculating a safe vibration dose threshold.

[0058] In one example, the processor 26 may be operable to compare the blood mass flow rate determined by processing the output of the visual sensor 24 to one or more threshold values or ranges. The threshold values are typically based on average biological characteristics for an operator but may be based on specific capacities of a particular operator. For instance, a typical male operator will have a blood mass of say ˜7% to 8% of total body mass. Therefore, a typical male weighing 75 kg will have approximately 5.6 kg of blood. Considering that the typical wrist veins diameters of a healthy hand-arm system are 2.5 mm, the average full body blood circulation rate is 23 seconds per cycle and the average hear rate of a healthy male is 72 bpm one might expect that a typical healthy male may have a blood mass transfer into the hand of say 70 g per heart beat and thus a typical blood mass flow rate of the order of 5.04 kg of blood entering the hand per minute. Based on the above estimate, a safe vibration dose may be determined to be exceeded if the blood mass flow falls outside the threshold range of: 4.9 kg/min to 5.9 kg/min. Similarly, based on the above estimate, an immediately dangerous vibration dose may be determined to have been experienced if the blood mass flow falls outside the threshold range of: 4.6 kg/min to 6.2 kg/min.

[0059] In another example, the processor 26 may be operable to compare current visual sensor 24 output to historical visual sensor 24 output for a particular operator stored in data storage unit 28. In this context, a reduction in blood mass flow rate for the same operator for the same vibration dose may indicate contraction of blood vessels at the extremities of the operator's hand 1. Such contractions are associated with vibration damage and thus can provide an early indication that an operator may be suffering from an excessive cumulative vibration dose.

[0060] Turning now to FIGS. 2 & 3, one possible embodiment of the apparatus 10 is illustrated. In this example, the sensing assembly 20 is provided on a support 11 in the form of an extended fingerless gauntlet. The support 11 is formed from a suitable flexible material, typically a synthetic fabric or the like. The support 11 is optionally lined with an absorbent layer (not shown) for the comfort of the operator. The skilled man will appreciate that other forms of support 11 are applicable to the present invention.

[0061] The support 11 has a sensor pocket 12 formed between two layers which is held against the operator's palm 9 in use. The sensor pocket 12 thus locates the sensing assembly 20 and urges it toward the palm 9 of the operator. This enables the sensing assembly 20 to output an accurate determination of the vibrations applied to the operator's hand 1 and the gripping force applied by the operator's hand 1.

[0062] A sheath 13 formed between two layers of the support 11 runs from the pocket 12 to control unit 25. The sheath 13 can provide space for cable 30 to connect the sensing assembly 20 and control unit 25 without presenting a snagging hazard. The cable 30 can terminate at a connecter socket 31. This can facilitate ready removal of control unit 25. Beneficially, this might facilitate repair, replacement or recharging of the control unit 25 after use.

[0063] The control unit 25 can be provided in a control unit pocket 14. The control unit pocket 14 can be formed between two layers of support 11 and/or between opposing faces 32, 33 of a control unit protective housing.

[0064] In an alternative embodiment, shown in FIG. 4, the support 11 is additionally provided with a visual sensor pocket 15 adapted to house the visual sensor 24. The visual sensor pocket 15 is provided between two layers of support 11 and provides an aperture enabling visual sensor 24 to capture images of the operator's skin. Typically, this is provided in the vicinity of wrist 8 where major blood vessels to the hand 1 are close to the skin. In the example shown, sheath 13 is split into different sections 13a, 13b & 13c as required to house respective sections of cable 30.

[0065] Turning to FIG. 5a, another alternative vibration dose measurement apparatus 10 comprises a support 101 made up of a main body 111 and straps 112. The body 111 is substantially planer with an outward bulging pocket 113 on the front side 111a, the pocket 113 housing the sensing assembly 20 and optionally the control assembly 25. The support 101 is formed from a flexible material such as thermoplastic polyurethane (TPU) or the like. As shown in FIG. 1, the straps 112 are formed integrally with the body 111. Nevertheless, the skilled man will appreciate that the straps 112 may be formed separately to the body 111 and attached to the body 111. In such circumstances, the straps 112 may be formed of a different material to the body 111.

[0066] The straps 112 may be provided with releasable attachment and adjustment means (not shown) such that opposing straps 112 may be connected together to hold the support 101 in place. Typically, the releasable attachment and adjustment means might comprise hook and loop fabric patches, buckles, slides, clips, catches or the like.

[0067] In use, as is illustrated in FIG. 5b, the apparatus 1 is fitted to the hand 1 of an operator. The support 101 is orientated such that the recess at the rear of pocket 13 is orientated towards the palm 9 of the operator. This ensures that the sensing assembly 20 is positioned as close as possible to the centre of vibration of the hand 1. One pair of straps 112 is connected together at the wrist end 8 of the hand 1, the other pair of straps 112 is connected together at the end of the hand adjacent to fingers 2-5. The thumb 6 projects between the two pairs of straps 112. By tightening the releasable attachment and adjustment means of the straps 112, the body 111 can be urged into contact with the palm 9, further ensuring that the sensing assembly 20 experiences as close as possible a vibration dose to that experienced by the hand 1.

[0068] In order to increase the comfort and safety of the operator whilst the apparatus 1 is fitted, the support 101 or at least the side of the body 111 facing the palm 101 may be fabric lined. In particular, the fabric may be suitable for soaking up excess sweat.

[0069] Turning now to FIGS. 6 and 7, two alternative embodiments of the apparatus are shown. In these alternative embodiments, the key difference is that form of the support. In FIG. 6, the support 102 comprises straps 112 with an ‘X’ form such that all four straps 112 can be connected using a single releasable attachment and adjustment means. The embodiment of FIG. 7 provides a support 103 with only a single one-piece strap 112 and has a much smaller body portion 111. This provide a simpler and lower cost version of the apparatus. Optionally, the one-piece strap 112 in FIG. 7 may be replaced by two straps 112 connected by a releasable attachment and adjustment means.

[0070] The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.