SPORTS PAD WITH FORCE SENSORS

Abstract

A sports pad for use in estimating a force exerted by an external object on the sports pad is provided. The sports pad comprises: an array of sensors, the sensors being spaced apart from one another across a grid of sensor positions of the sports pad, each sensor being configured to independently collect data indicative of the force acting on the respective sensor; and a data receiver configured to receive the collected data from each of the array of sensors such that data from a plurality of the sensors may be used to estimate a force.

Claims

1. A sports pad for use in estimating a force exerted by an external object on the sports pad, the sports pad comprising: an array of sensors, the sensors being spaced apart from one another across a grid of sensor positions of the sports pad, each sensor being configured to independently collect data indicative of the force acting on the respective sensor; and a data receiver configured to receive the collected data from each of the array of sensors such that data from a plurality of the sensors may be used to estimate a force.

2. A sports pad according to claim 1, wherein the sensors are arranged across a substrate layer of the sports pad.

3. A sports pad according to claim 2, wherein the substrate layer defines a grid, each sensor being located at an intersection of the grid defined by the substrate layer.

4. (canceled)

5. A sports pad according to claim 1, wherein the grid of sensor positions is a non-uniform grid of sensor positions.

6. A sports pad according to claim 5, wherein sensor positions are randomly or pseudo-randomly arranged across the grid of sensor positions.

7. A sports pad according to claim 1, comprising at least 10 sensors, preferably at least 20 sensors, more preferably at least 40 sensors.

8. A sports pad according to claim 1, wherein each sensor comprises a force sensitive area and wherein the total force sensitive area of the array of sensors is at most 50%, more preferably at most 30%, further preferably at most 20%, of the total area covered by the array of sensors.

9. A sports pad according to claim 1, wherein each sensor comprises a force sensitive area of at most 25 cm.sup.2, preferably at most 10 cm.sup.2, more preferably at most 5 cm.sup.2, most preferably at most 1 cm.sup.2.

10. (canceled)

11. A sports pad according to claim 1, further comprising a data transmitter configured to transmit the data received by the data receiver and preferably being configured to wirelessly transmit the data.

12. (canceled)

13. A sports pad according to claim 1, wherein the sports pad is configured to be fitted to a non-planar surface such that the array of sensors defines a non-planar sensing layer.

14. A sports pad according to claim 1, wherein the sports pad is incorporated in a sports item, such as body armour, sports clothing, or sports training equipment.

15. (canceled)

16. A system configured to estimate a force exerted by an external object on a sports pad, the system comprising: a sports pad according to claim 1; a processor configured to calculate an estimated force based on the data collected by a plurality of the sensors.

17. A system according to claim 16, wherein the processor is configured to calculate an estimated force by fitting a continuous function to the data collected by the plurality of sensors.

18. (canceled)

19. A system according to claim 16, wherein the processor is configured to calculate an estimated force based on the data collected by a plurality of the sensors and based on a predetermined spacing of the plurality of sensors.

20. A system according to claim 16, wherein the processor is configured to select data from a subset of the plurality of sensors and to calculate an estimated force for a subarea corresponding to the selected subset based on the data collected by said subset of the plurality of sensors.

21. A system according to claim 20, wherein the subset of the plurality of sensors is selected based on the data collected by the plurality of sensors.

22. (canceled)

23. A system according to claim 21, wherein the processor is configured to repeat the calculation of estimated force and wherein data is collected from the subset of the plurality of sensors at faster rate than data is collected from sensors outside of the subset of the plurality of sensors.

24. A system according to claim 16, wherein the processor is configured to repeat the calculation of estimated force using data collected by a plurality of sensors at non-uniform time intervals, preferably at random or pseudo-random time intervals.

25. A system according to claim 16, wherein the sports pad is a first sports pad and further comprising a second sports pad and a processor, wherein the second sports pad comprises a second array of sensors, the sensors being spaced apart from one another across a second grid of sensor positions of the second sports pad, each sensor of the second array of sensors being configured to independently collect data indicative of the force acting on the respective sensor; and a second data receiver configured to receive the collected data from each of the second array of sensors such that data from a plurality of the sensors of the second array of sensors may be used to estimate a second force, and wherein the processor is configured to calculate an estimated force based on the data collected by the plurality of the sensors of the second array of sensors of the second sports pad, the processor being configured to compare the data collected by the plurality of sensors of the first sports pad with the data collected by the plurality of sensors of the second sports pad, to identify an event occurring between the two sports pads based on said comparison, and to output an indication of the event occurring between the two sports pads.

26. (canceled)

27. A method of estimating a force exerted by an external object on a sports pad, the method comprising: collecting, using an array of sensors, data indicative of the force acting on each of the respective sensors, wherein the sensors are spaced from one another across a grid of sensor positions within the sports pad, and wherein each sensor is configured to independently collect the data indicative of force; receiving, at a data receiver, the collected data from each of the array of sensors; calculating, using a processor, an estimated force based on the data collected by a plurality of the sensors.

28.-32. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will now be explained with reference to the Figures, of which:

[0043] FIG. 1 shows a prior art sports pad in a top view;

[0044] FIGS. 2A to 2C show a sports pad according to a first embodiment of the invention in a top view and a portion of the sports pad in an enlarged top view and an enlarged cross-section view respectively;

[0045] FIG. 3 shows, schematically, a system integrating the sports pad according to the first embodiment; and

[0046] FIG. 4 is a flow diagram illustrating a method of using the system of FIG. 3 to estimate a force exerted by an external object on the sports pad.

DETAILED DESCRIPTION

[0047] FIG. 1 shows a prior art force pad 1 for measuring the force exerted by an external object on the force pad. Specifically, FIG. 1 shows a generally U-shaped shoulder pad configured to sit on a wearer's shoulders, with two shoulder covering portions connected by a central portion that extends over a wearer's upper back.

[0048] The prior art force pad 1 shown in FIG. 1 comprises six flexible sensors R1 to R3 and L1 to L3, with three on either side. When fitted, each shoulder thereby has a first sensor R1, L1 positioned on the front of the shoulder, a second sensor R2, L2 abutting the first sensor and positioned on the top of the shoulder and a third sensor R3, L3 abutting the second sensor and positioned on the back of the shoulder and extending towards the centre of the wearer's upper back. Each of these flexible sensors is connected via wiring 2 to an electronics unit 3 arranged to sit approximately between the shoulder blades of the wearer.

[0049] Together, the flexible sensors R1 to R3 and L1 to L3 substantially cover the shoulders of the wearer. Each of the flexible sensors R1 to R3 and L1 to L3 in the prior art force pad directly measures a force acting on the respective sensor by monitoring the separation of the upper and lower surfaces of the sensor. Together, the sensors are able to measure a force over the complete shoulder area of the wearer. However, as will be appreciated from FIG. 1, each of the flexible sensors R1 to R3 and L1 to L3 is required to bend to match the contours of the wearer's shoulders. This bending of the sensors also causes a decrease in the separation between upper and lower surfaces, leading to the reading of fictitious forces. Furthermore, wear-and-tear on flexible sensors (through tackles made, scrumming etc.) causes accumulation of creases which results in further fictitious forces being recorded and can ultimately lead to the force pad to cease working.

[0050] FIGS. 2A to 2C show a sports pad 100 according to the present invention. The sports pad 100 is again a generally U-shaped shoulder pad configured to sit on a wearer's shoulders, with two shoulder-covering portions 101, 102 connected by a central portion 103 that extends over a wearer's upper back. The sports pad thus takes a similar profile to a yoke.

[0051] The sports pad 100 comprises an array of spaced apart force sensors 104 arranged across the two shoulder-covering portions 101, 102 and extending into the central portion 103. In particular, the force sensors 104 are arranged across a flexible PET substrate layer defining an open grid, with each force sensor being located at a junction of the grid defined by the substrate. The spacing of the force sensors is non-uniform across the array of force sensors in order to provide an irregular or non-uniform arrangement of the sensors, which is less susceptible to periodicity bias for the reasons described above. That is, as shown in FIG. 2B, which corresponds to area A of the sports pad in FIG. 2A, each force sensor is positioned at a junction between multiple grid elements of the grid defined by the substrate layer. This grid arrangement reduces the weight of the sensor layer since it provides apertures through the substrate layer 108. In this embodiment, the substrate also comprises printed circuitry 105 in the form of printed silver for transmitting power to the sensors and transmitting the data collected by the force sensors. The force sensors 104 are arranged in a plurality of rows along the sports pad and the grid defined by the substrate 108 generally extends along the rows and between neighbouring sensors in adjacent rows, i.e. generally along columns of the array.

[0052] The printed circuitry 105a extending along the rows of the array supplies power to each of the plurality of sensors 104. This printed circuitry joins a main circuitry path 106 at the end of each row, which then extends around the periphery of the sports pad to the electronics unit 107. Meanwhile, the printed circuitry 105b extending between the rows, i.e. generally along the columns of the array, provides the data paths along which data from each of the force sensors 104 is transferred to the electronics unit 107.

[0053] Suitable force sensors include the FlexiForce A101 Sensor sold by Tekscan, Inc. of 307 West First Street, South Boston, Mass. 02127, United States.

[0054] As most clearly shown in FIG. 2C, the array of force sensors 104 are distributed across the substrate layer 108 and are interconnected by the printed circuitry. An inner padded layer 109a is provided beneath the substrate layer 108 to separate and cushion the force sensors and substrate layer 108 relative to the wearer's shoulders. An outer padded layer 109b is also provided over the array of force sensors to shield the force sensors from the environment and to cushion any impacting object, which may be another person. Preferably the substrate layer 108, inner padded layer 109a and outer padded layer 109b are also waterproof, to protect the force sensors 104.

[0055] FIG. 3 shows, schematically, a system for estimating a force exerted by an external object on the sports pad. FIG. 3 shows, schematically, a sports pad 100, which may be the sports pad shown in FIGS. 2A to 2C. FIG. 3 shows a plurality of force sensors 104 connected via circuitry 105b to an electronics unit 107. In this Figure, only seven force sensors are shown for simplicity; however, it will be appreciated, especially in view of FIG. 2A, that many more sensors are typically connected to the electronics unit 107. The electronics unit 107 may comprise a memory module for storing data received from the force sensors. This is particularly suitable where the sports pad is configured to collect data relating to a session, before the data is transferred to an external electronics unit 110 after the session for evaluating impact forces relating to the entire session. This may be performed by removing the memory module, which may for example be a memory card. The electronics unit may, alternatively, or in addition, comprise a data transmitter configured to transmit data to a receiver of an external electronics unit. FIG. 3 shows a connection 111 between the electronics unit 107 and the external electronics unit 110. The data transmitter may utilise a hardware port, such as a USB port, to connect the electronics unit 107 to the external electronics unit 110. However, preferably, the data transmitter uses a wireless data transmission means, for example a Bluetooth transmitter or radio transmitter. A wireless transmitter, as used in this preferred embodiment, may allow for data to be transmitted in real-time, which is preferable for broadcast sports. A small power supply is also provided within the external electronics unit 110 to power the components on the sports pad. This may be, for example, a battery module comprising one or more replaceable or rechargeable batteries.

[0056] The external electronics unit 110 may be, for example, a computer, having a processor, e.g. a central processing unit (CPU), hard drive, random access memory (RAM), display and one or more input devices. Where the electronics unit 107 comprises a data transmitter, preferably the external electronics unit has a complementary data receiver for establishing a direct data connection 111 between the electronics unit 107 of the sports pad and the external electronics unit 110.

[0057] While the embodiment of FIG. 3 uses an external electronics unit 110 to carry out the estimation of force experienced, in alternative embodiments, the electronics unit 107 on the sports pad may comprise a processor and the electronics unit 107 may thereby be adapted to estimate a force directly on the sports pad.

[0058] A method of using the system shown in FIG. 3 will now be described with reference to FIG. 4, which is a flow diagram showing the steps taken to estimate the impact force of an object with the sports pad.

[0059] The sports pad 100 is fitted to a wearer who is to engage in a sports activity in which one or more external objects will come into contact with the sports pad. In step S100, the sports pad collects force data using each force sensor 104 of the array of force sensors. The collection of the force data captures data relating to an increase in force exerted on a plurality of the force sensors by an external object.

[0060] In step S200, the force data is received at the electronics unit 107, having been transmitted to the electronics unit 107 via the circuitry 105b.

[0061] In step S300, the collected force data received by the electronics unit 107 is transmitted, e.g. wirelessly, to an external electronics unit 110, such as a computer.

[0062] The external electronics unit 110 then fits a continuous function to the data collected by the plurality of force sensors using a processor in step S400. One way of fitting a continuous function to the data will now be described in detail.

[0063] Each of the sensors can be labelled with an index i. The coordinates of each sensor are fixed relative to one another by their positioning on the substrate layer 108 at the junctions of the grid. Their coordinates can be expressed as (x.sub.i,y.sub.i) while the force output for each sensor, can be expressed as f.sub.i. As has been mentioned above, the surface area of the force sensors is fixed and so the sensor can be adapted to either measure a pressure, which can be used to determine the force in combination with the surface area, or directly measure a force. The resulting data set will comprise, for each force sensor, the coordinate data of the force sensor in the array, and the force data collected by the sensor. The resulting data set, for a specific time t, may therefore be represented as

[(x.sub.1, y.sub.1, f.sub.1), . . . (x.sub.n, y.sub.n, f.sub.n).]

[0064] where n is the number of sensors in the array.

[0065] The surface form must be specified a priori. The form may be selected as desired to balance the accuracy of the estimate with the computational power required to process higher surface forms. To fit a surface of degree two, one needs to determine the coefficients a.sub.jk in the equation

g(x, y)=a.sub.20x.sup.2+a.sub.11xy+a.sub.02y.sup.2+a.sub.10x+a.sub.01y+a.sub.00

[0066] If there are exactly six sensors, with six force outputs, then this surface can be determined exactly. However, in the above sports pad, there are more sensors than there are coefficients in the equation, and therefore the coefficients are overconstrained. In order to determine the coefficients in the overconstrained scenario, construct an error function and to then minimize it with respect to the coefficients. The present method minimizes the sum of the square errors.

[0067] Let the error function be

E=Σ.sub.i[g(x.sub.i,y.sub.i)−f.sub.i].sup.2

[0068] Now, the six equations for the six coefficients can be constructed by taking the partial derivative of the error function with respect to each of the coefficients and setting it equal to zero. This approach allows us to determine the coefficients which minimize the error function, or make it stationary for small perturbations in the coefficients.

[00001]$\frac{\partial E}{\partial a_{\mathrm{jk}}}=2{.Math.}_i[g\left(x_i,y_{i)}-f_i\right]\left[\frac{\partial g\left(x,y\right)}{\partial a_{\mathrm{jk}}}\right]=0$

[0069] These equations can be arranged into a matrix as follows

[00002]$\left[\begin{array}{cccccc}.Math.x_i^4& .Math.x_i^3{y}_i& .Math.x_i^2{y}_i^2& .Math.x_i^3& .Math.x_i^2{y}_i& .Math.x_i\\ .Math.x_i^3{y}_i& .Math.x_i^2{y}_i^2& .Math.x_i{y}_i^3& .Math.x_i^2{y}_i& .Math.x_i{y}_i^2& .Math.x_i{y}_i\\ .Math.x_i^2{y}_i^2& .Math.x_i{y}_i^3& .Math.y_i^4& .Math.x_i{y}_i^2& .Math.y_i^3& .Math.y_i^2\\ .Math.x_i^3& .Math.x_i^2{y}_i& .Math.x_i{y}_i^2& .Math.x_i^2& .Math.x_i{y}_i& .Math.x_i\\ .Math.x_i^2{y}_i& .Math.x_i{y}_i^2& .Math.y_i^3& .Math.x_i{y}_i& .Math.y_i^2& .Math.y_i\\ .Math.x_i^2& .Math.x_i{y}_i& .Math.y_i& .Math.x_i& .Math.y_i& N\end{array}\right]\{\begin{array}{c}{a}_{20}\\ a_{11}\\ a_{02}\\ a_{10}\\ a_{01}\\ a_{00}\end{array}\}=[\begin{array}{c}.Math.x_i^2{f}_i\\ .Math.x_i{y}_i{f}_i\\ .Math.y_i^2{f}_i\\ .Math.x_i{f}_i\\ .Math.y_i{f}_i\\ .Math.f_i\end{array}]$

or in a more compact notation as

[Σ]{a.sub.jk}={b}

[0070] The coefficients can now be determined by premultiplying both sides by the inverse

{a.sub.jk}=[Σ].sup.−1{b}

[0071] The total force F can then be estimated in step S500 by integrating g(x.sub.i,y.sub.i) over the total area A and then dividing by the total area as follows:

[00003]$F=\frac{\int g\left(x,y\right)dA}{\int dA}$

[0072] The total force may then be output in step S600. For example, the force may be displayed on a screen of the external electronics unit 110. It should be noted here that any surface fit, for example a two-dimensional spline interpolation, may be used according to the present invention to determine the continuous function and ultimately arrive at the total force output in step S600.

[0073] This process may be repeated over time in order to monitor the development of an applied force. As explained above, the the force output for each sensor f.sub.i may be sampled at irregular or non-uniform time intervals and used in successive force estimations to remove periodicity bias in the monitoring of the development of an applied force to give a truer representation of the development of the applied force.

[0074] While the above process describes estimating the force across the entire sensor array, it will be appreciated that it can equally be applied to subsets of the array. As explained above, the subsets may be predetermined, e.g. subsets may be programmed in that correspond to areas of interest of the sports pad, such as certain anatomical regions of a player. Alternatively, the subset may be selected dynamically. In one instance, all sensors detecting a pressure over a predetermined value may be selected to define the subarea and the above calculations adapted for that dynamically selected subset.

[0075] This process may be performed for multiple events occurring at different times and on different sports pads used in the system in order to estimate the force of impact of a number of different objects over a training or playing session, for example. Where multiple sports pads are used in the system, the above calculation processes may be run simultaneously and in parallel for each sports pad.

[0076] This information can be valuable in training, for example, to measure the strength of a tackle and track players who are improving or deteriorating over time. The information can also be used to compare static and dynamic forces, e.g. how much force a player imparts when a scrum engages compared with how much they are able to impart when the scrum is underway. The information can be medically useful in determining the forces imposed on players in play. If the values exceed those which are believed to be acceptable then players can be removed from the field of play to avoid injury, rules can be modified or additional protective equipment can be introduced. Forces can also be tracked over time to monitor player fatigue, which can be helpful for deciding when a player should be rested, but also monitoring player development, e.g. after how long fatigue begins to set in. The information may also be of great interest to spectators, especially those not physically present at the event who watch the event as a broadcast, for example television broadcast or a webcast. In this case, not all of the collected information need be displayed to the spectators but a selection which can be selected by the end user or by an editor of the broadcaster. Thus in the first case an individual end user could choose to monitor the performance of a favourite player. In the second case an editor of the broadcaster, for example seeing a player about to be tackled, could choose to broadcast the forces acting on that player.

[0077] While the invention has been described by reference to a shoulder pad for use in rugby, it will be appreciated that the sports pad can be used in many different sports contexts. For example, the sports pad could be provided on the exterior of body armour used in American football for example, or used in training items, such as tackle shields. The sports pad could also be integrated across a full shirt so to provide data concerning forces measured across the whole upper body of a wearer.