Force sensing device

Abstract

A force sensing device (101) comprises a first electrode (102) and a second electrode (103) arranged to provide an electrical output in response to an applied force to determine a magnitude of the applied force. The force sensing device comprises a collapsible structure (201) configured to provide an electrical short circuit in response to an applied force when the applied force exceeds a predetermined magnitude.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to UK patent application number 2203737.8 filed on March 17, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a force sensing device, a method of calibrating a force sensing device, and a method of manufacturing a force sensing device. Background Art

[0004] Force sensing devices are typically calibrated at the time of manufacture to correct for any differences in sensor response under load. During use, wear from repeated loading and / or environmental conditions that vary over time can cause irreversible changes in the sensing device.

[0005] Therefore, the initial calibration performed during manufacturing may not be sufficient to maintain acceptable performance of the force sensing device throughout the useful life of the force sensing device.

[0006] Therefore, there remains a need to maintain accurate force readings throughout the useful life of the force sensing device. Summary of the invention

[0007] According to a first aspect of the present invention, there is provided a force sensing device, comprising: a first electrode and a second electrode; the first electrode and the second electrode are arranged to provide an electrical output in response to an applied force to determine the magnitude of the applied force; the force sensing device also comprises: a collapsible structure, configured to provide an electrical short circuit in response to the applied force when the applied force exceeds a predetermined magnitude.

[0008] According to a second aspect of the present invention, there is provided a method for calibrating a force sensing device, comprising the following steps: obtaining a force sensing device comprising a first electrode and a second electrode, the first electrode and the second electrode being arranged to provide an electrical output in response to an applied force; and applying a force exceeding a predetermined value to the force sensing device; wherein a collapsible structure arranged within the force sensing device provides an electrical short circuit in response to the applied force.

[0009] According to a third aspect of the present invention, there is provided a method for manufacturing a force sensing device, comprising the following steps: arranging a first electrode and a second electrode to form a force sensing device, the force sensing device being configured to provide an electrical output in response to an applied force; and arranging a collapsible structure within the force sensing device, the collapsible structure being configured to provide an electrical short circuit in response to the applied force when the applied force exceeds a predetermined value.

[0010] Embodiments of the present invention will be described by way of example only with reference to the accompanying drawings. The detailed embodiments show the best mode known to the inventor and provide support for the claimed invention. However, they are merely exemplary and should not be used to interpret or limit the scope of the claims. Their purpose is to provide guidance to those skilled in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The different layers of the force sensing device are shown;

[0012] Figure 2 shows a schematic cross-sectional view of a force sensing device according to the present invention;

[0013] Figure 3 shows that under the applied force Figure 2 A force sensing device;

[0014] Figure 4 shows a force-resistance curve for a force sensing device; and

[0015] Figure 5 A method of calibrating a force sensing device is shown. DETAILED DESCRIPTION

[0016] Figure 1

[0017] Figure 1 1 shows a force sensing device 101 in the form of an exploded schematic diagram showing the layers that make up the force sensing device. The force sensing device 101 includes a first electrode 102 and a second electrode 103. In this embodiment, the electrode 102 is disposed on a first substrate 104 and the electrode 103 is disposed on a second substrate 105.

[0018] In one embodiment, electrode 102 includes a first conductive layer, and electrode 103 includes a second conductive layer. In one embodiment, the conductive layers include a metallic material, such as a silver-based ink or a carbon-based ink, coated on a respective substrate.

[0019] Additionally, in this embodiment, at least one electrode further comprises a resistive material layer 106, which may be coated on the surface of one or more conductive layers. In the illustrated embodiment, the resistive material layer is shown as being coated on electrode 103. It should be understood that in alternative embodiments, the resistive material layer 106 may be coated on electrode 102 or on both electrodes 102 and 103. In one embodiment, the resistive material layer comprises a quantum tunneling material, such as that available from the applicant Peratech Holdco Ltd under the trademark Thus, the resistive material layer comprises a material that exhibits a change in resistance in response to an applied force. It should be understood that other materials having a variable resistance may be used in the present invention.

[0020] In combination, electrodes 102 and 103 are arranged to provide an electrical output in response to an applied force to enable the magnitude of such applied force to be determined. In some embodiments, in addition to the magnitude of the applied force, electrodes 102 and 103 may also be configured to determine position data associated with the applied force.

[0021] Figure 2

[0022] Figure 2 A schematic cross-sectional view of the force sensing device 101 is further shown in FIG.

[0023] In the present embodiment, the force sensing device 101 further comprises a collapsible structure 201. The collapsible structure 201 comprises an electrical shorting contact and is configured to provide an electrical short in response to the applied force if the applied force exceeds a predetermined magnitude.

[0024] In the illustrated embodiment, the collapsible structure 106 includes four individual elements 201A, 201B, 201C, and 201D. As shown, elements 201A and 201C are disposed on substrate 104, and elements 201B and 201D are disposed on substrate 105. In this embodiment, the collapsible structure 201 is located at one end of substrates 104 and 105. Thus, elements 201A and 201B are disposed at a first end 202 of the force sensing device 101, and elements 201C and 201D are disposed at a second end 203 of the force sensing device 101. However, it should be understood that alternative collapsible structures may be located at other locations in the force sensing device where they are able to receive an applied force for calibration purposes.

[0025] In this embodiment, the collapsible structure 201 includes metal-based contacts that are configured to provide an electrical short circuit. In an alternative embodiment, the collapsible structure 201 includes a domed structure arranged to form an electromechanical switch. In one such embodiment, the domed structure includes an elastic material that collapses under an applied force of a predetermined magnitude, which causes the electrode to respond, thereby causing the measurement of the applied force from the electrode to short circuit.

[0026] Figure 2 The collapsible structure 201 is shown in an initial configuration, wherein elements 201A and 201B and 201C and 201D are not in contact with each other in a manner similar to electrodes 102 and 103. Under an applied force (which will be referred to as Figure 3As further described, the collapsible structure 201 is configured to transition into a collapsed configuration in response to the applied force.

[0027] Figure 3

[0028] exist Figure 3 In the embodiment shown, an applied force 301 is provided to the upper surface of force sensing device 101. Applied force 301 has the effect of bringing electrodes 102 and 103 into contact with each other to allow current to flow between the two electrodes so that the magnitude of the applied force can be calculated in a conventional manner.

[0029] At the same time, the collapsible structure 201 also receives an input of the applied force 301 using the force sensing device 101 and moves relative to the collapsible structure 201. Figure 2 The initial configuration is transformed into a collapsed configuration.

[0030] In this embodiment, the collapsible structure 201 includes a plurality of contact elements made of a material having a contact radius that is configured to expand under the action of an applied force. Examples of such materials include silver-based contact materials. Thus, in this embodiment, elements 201A, 201B, 201C, and 201D expand in cross-sectional area in response to an applied force 301. Thus, when a given contact radius is reached, corresponding to a predetermined magnitude of force, the collapsible structure provides an electrical short circuit.

[0031] Thus, a single output signal from an electrical short is provided at a known predetermined force of a given magnitude. The electrical short may be reported in the main sensing circuit of the force sensing device or an electronic device incorporating the force sensing device. If a short occurs in the main sensing circuit, the collapse force may be designed to be the upper limit of the sensing force range of the force sensing device so as not to compromise the sensing function at lower forces.

[0032] Alternatively, a separate circuit may be provided which receives the short circuit.

[0033] In this embodiment, the collapsible structure 201 is configured to Figure 3 The collapsed configuration returns to Figure 2 This return to the initial configuration is designed to be repeatable so that the force sensing device can be repeatedly calibrated throughout its life cycle.

[0034] Figure 4

[0035] Figure 4 A force-resistance curve 401 of a force sensing device is shown in FIG. The force-resistance curve 401 shows a typical response of a force sensing device (eg, force sensing device 101) to an applied force.

[0036] In an exemplary embodiment, the collapsible structure is configured to short the electrical contacts so that the measurement of the resistance in the sensing circuit provides a sudden change in resistance identified in the sensing circuit. As shown, at point 402, an applied force 403 of magnitude F is reached. At this point, the resistance suddenly changes due to the collapse of the collapsible structure 201. Therefore, the sensing circuit is able to use the change in resistance at point 402 as a reference point for a predetermined force. The resistance value measured before point 402 can then be used as the value in the calibration. This thereby reduces any previous force errors.

[0037] In an exemplary embodiment, the force F is configured to have a magnitude outside of normal use, such as at an upper limit. Therefore, the force sensing device can be provided with a calibration routine that can be activated by the user at given time intervals to recalibrate the force sensing device during its life cycle.

[0038] Figure 5

[0039] Figure 5 A method of calibrating a force sensing device as described herein is schematically shown. At step 501, a force sensing device (e.g., force sensing device 101) is acquired. As previously described, the force sensing device includes a first electrode and a second electrode arranged to provide an electrical output in response to an applied force.

[0040] When an applied force of a predetermined magnitude or exceeding the applied force is applied at step 502 , at step 503 , the collapsible structure 201 causes a short circuit in response to the applied force.

[0041] Then, at step 504, the sensing circuit and corresponding processor use the data from the short circuit to identify the collapse point. In one embodiment, the step of identifying the collapse point of the collapsible structure is identified by a change in resistance.

[0042] Therefore, at step 505, the force sensing device is adjusted or recalibrated to ensure that future outputs have any previous errors reduced.

Claims

1. A force sensing device, comprising: a first electrode and a second electrode; The first electrode and the second electrode are arranged to provide an electrical output in response to the applied force to determine a magnitude of the applied force; The force sensing device further comprises: The collapsible structure is configured to provide an electrical short circuit in response to an applied force when the applied force exceeds a predetermined magnitude.

2. The force sensing device according to claim 1, wherein: The first electrode includes a first conductive layer, and the second electrode includes a second conductive layer.

3. The force sensing device according to claim 2, wherein: At least one of the first electrode or the second electrode further includes a variable resistance material layer.

4. The force sensing device according to any one of claims 1 to 3, wherein: The first electrode is disposed on the first substrate, and the second electrode is disposed on the second substrate.

5. A force sensing device according to any preceding claim, wherein: The collapsible structure is configured to return from a collapsed configuration to an initial configuration upon application of an applied force exceeding a predetermined magnitude.

6. A force sensing device according to any preceding claim, wherein: The collapsible structure is configured to expand in a cross-sectional area in response to an applied force.

7. A method for calibrating a force sensing device, comprising the steps of: obtaining a force sensing device comprising a first electrode and a second electrode arranged to provide an electrical output in response to an applied force; as well as applying a force exceeding a predetermined magnitude to the force sensing device; in A collapsible structure disposed within the force sensing device provides an electrical short circuit in response to an applied force.

8. The method according to claim 7, wherein: The electrical short circuit provides a resistance change, and the method further comprises the steps of: The collapse point of the collapsible structure is identified by the change in resistance.

9. The method according to claim 8, further comprising the steps of: In response to the step of identifying the collapse point, an output of the force sensing device is adjusted.

10. A method of manufacturing a force sensing device, comprising the steps of: arranging the first electrode and the second electrode to form a force sensing device configured to provide an electrical output in response to an applied force; as well as A collapsible structure is disposed within the force sensing device, the collapsible structure being configured to provide an electrical short circuit in response to the applied force when the applied force exceeds a predetermined magnitude.

11. The method according to claim 10, further comprising the steps of: disposing a first electrode on a first substrate; and A second electrode is disposed on the second substrate.

12. The method according to claim 10 or claim 11, further comprising the steps of: A variable resistance material is applied to the first electrode or the second electrode.

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