Force Sensing Device

Abstract

The 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, i.e., an applied force, and to determine the magnitude of the applied force. The force sensing device is configured with a foldable structure (201) configured to provide an electrical short in response to the applied force when the applied force exceeds a predetermined magnitude, thereby maintaining accurate force measurements throughout the usable life of the force sensing device.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to UK patent application number 22 03 737.8, filed March 17, 2022, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] The present invention relates to a force sensing device, a method for calibrating a force sensing device, and a method for manufacturing a force sensing device. Force sensing devices are typically calibrated at the time of manufacture to compensate for differences in sensor response under load. During use, irreversible changes can occur in the sensing device due to wear from repeated loading and / or changing environmental conditions over time. As a result, an initial calibration performed at the time of manufacture may not be sufficient to maintain acceptable performance of the force sensing device throughout its usable life. Summary of the Invention [Problem to be solved by the invention]

[0003] Thus, there remains a need to maintain accurate force measurements throughout the usable life of a force sensing device. [Means for solving the problem]

[0004] [Brief Description of the Invention] 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 and to determine a magnitude of the applied force; and the force sensing device further comprises a foldable structure configured to provide an electrical short in response to the applied force when the applied force exceeds a predetermined magnitude.

[0005] According to a second aspect of the present invention, there is provided a method of calibrating a force sensing device, comprising the steps of: obtaining a force sensing device including a first electrode and a second electrode arranged to provide an electrical output in response to an applied force; and applying a force to the force sensing device of greater than a predetermined magnitude, where a foldable structure disposed within the force sensing device provides an electrical short in response to the applied force.

[0006] According to a third aspect of the present invention, there is provided a method of manufacturing a force sensing device configured to provide an electrical output in response to an applied force, the method comprising the steps of: disposing a first electrode and a second electrode within the force sensing device, the foldable structure configured to provide an electrical short in response to the applied force when the applied force exceeds a predetermined magnitude. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the different layers of a force sensing device; [Diagram 2] FIG. 2 is a schematic cross-sectional view of a force sensing device according to the present invention; [Diagram 3] FIG. 3 shows the force sensing device of FIG. 2 with an applied force; [Figure 4] FIG. 4 shows the force-resistance curve of the force sensing device; and [Diagram 5] FIG. 5 illustrates a method for calibrating the force sensing device.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which:

[0024] The detailed embodiments show the best mode known to the inventors and support the invention as claimed; however, they are merely illustrative and should not be used to interpret or limit the scope of the claims; their purpose is to educate those skilled in the art.

[0009] [Detailed Description of the Invention] (Figure 1) 1 shows a force sensing device 101, in an exploded schematic diagram illustrating 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 an embodiment, the electrode 102 is provided on a first substrate 104 and the electrode 103 is provided on a second substrate 105. 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 the respective substrates.

[0010] Moreover, in an embodiment, at least one electrode further comprises a resistive material layer 106, which may be coated on the surface of the conductive layer or layers. In this illustrated embodiment, the resistive material layer is coated on electrode 103. It can 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, for example, a quantum tunneling composite material available under the trademark QTC® from applicant Peratec Holdco Limited. Thus, the resistive material layer comprises a material whose resistance changes in response to an applied force. It can be understood that other materials having variable resistance may also be applied in the present invention.

[0011] In combination, electrodes 102 and 103 are arranged to provide an electrical output in response to an applied force, and the magnitude of such applied force can be determined. In some embodiments, in addition to the magnitude of the applied force, electrodes 102 and 103 may be further configured to determine position data associated with the applied force.

[0012] (Figure 2) FIG. 2 is a further schematic side view of the force sensing device 101. In an 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 an applied force when the applied force exceeds a predetermined magnitude.

[0013] In this illustrated embodiment, the foldable structure 106 includes four separate 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 an embodiment, the foldable structure 201 is disposed at the ends of the 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 will be appreciated that alternative foldable structures may be disposed elsewhere within the force sensing device that can receive an applied force for calibration purposes.

[0014] In an embodiment, the foldable structure 201 includes metal-based contacts configured to provide an electrical short. In an alternative embodiment, the foldable structure 201 includes a dome-shaped structure arranged to form an electromechanical switch. In one such embodiment, the dome-shaped structure includes a resilient material that folds under a predetermined amount of applied force, which causes a measurement of the applied force from the electrodes to short.

[0015] Figure 2 shows the foldable structure 201 in an initial configuration in which elements 201A, 201B, 201C, and 201D are not in contact with one another, as are electrodes 102 and 103. As will be further described with respect to Figure 3, under an applied force, the foldable structure 201 is configured to deform into a folded configuration in response to the applied force.

[0016] (Figure 3) In the embodiment shown in Figure 3, an applied force 301 is applied to the upper surface of the force sensing device 101. The applied force 301 has the effect of bringing electrodes 102 and 103 into contact with one another such that upon contact a current flows between the two electrodes and the magnitude of the applied force can be calculated in a conventional manner. At the same time, in the force sensing device 101, the collapsible structure 201 further receives the input of the applied force 301 and transforms into a folded configuration compared to the initial configuration of FIG.

[0017] In an embodiment, the foldable structure 201 includes a plurality of contact elements made of a material having a contact radius configured to expand with 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. As a result, when a predetermined contact radius is reached, an electrical short is created in the foldable structure corresponding to a predetermined force magnitude.

[0018] Thus, a single output signal from the electrical short is provided at a known, predetermined force of a predetermined magnitude. The electrical short may be reported in the force sensing device or in a main sensing circuit of the electronic device in which the force sensing device is incorporated. If a short occurs in the main sensing circuit, the folding force may be designed to be at the upper end of the sensing force range of the force sensing device to avoid compromising the sensing function at lower forces.

[0019] Alternatively, a separate circuit may be provided to receive the short circuit. In an embodiment, the foldable structure 201 is configured to return from the folded configuration of Figure 3 to the initial configuration of 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 lifecycle.

[0020] (Figure 4) 4 illustrates a force-resistance curve 401 for a force sensing device. The force-resistance curve 401 illustrates a typical response to an applied force to a force sensing device, such as the force sensing device 101. In one exemplary embodiment, the foldable structure is configured to short the electrical contacts, and a measurement of the resistance in the sensing circuit provides an abrupt change in resistance that is identified in the sensing circuit. As shown, at point 402, an applied force 403 of magnitude F is reached. At this point, a sudden change in resistance occurs due to the collapse of the foldable structure 201. As a result, the sensing circuit can use the change in resistance at point 402 as a reference point for a given force. The resistance value measured before point 402 can then be used as a calibration value. This can reduce any prior force errors.

[0021] In one exemplary embodiment, the force F is configured to be a magnitude outside of normal use, such as an upper limit. Thus, the force sensing device may be provided with a calibration routine that a user can activate at predetermined intervals to recalibrate the force sensing device over its lifecycle.

[0022] (Figure 5) A method for calibrating a force sensing device as described herein is outlined in Figure 5. In step 501, a force sensing device is obtained, such as force sensing device 101. As described above, the force sensing device includes a first electrode and a second electrode arranged to provide an electrical output in response to an applied force.

[0023] Upon providing an applied force at or above a predetermined magnitude in step 502, the collapsible structure 201 induces a short circuit in response to the applied force in step 503. When a predetermined applied force or greater is applied in step 502, the collapsible structure 201 induces a short circuit in response to the applied force in step 503.

[0024] The sensing circuitry and corresponding processor then use the data from the short circuit to identify the point of collapse in step 504. In one embodiment, identifying the point of collapse of the collapsible structure is identified by a change in electrical resistance. Therefore, in step 505, the force sensing device is adjusted or recalibrated to ensure that future outputs will reduce previous errors.

Claims

1. a first electrode and a second electrode; the first electrode and the second electrode are configured to provide an electrical output in response to an applied force and to determine a magnitude of the applied force; Furthermore, the force sensing device a collapsible structure configured to provide an electrical short in response to the applied force when the applied force exceeds a predetermined magnitude; Force sensing device.

2. The force sensing device of claim 1 , wherein the first electrode comprises a first conductive layer and the second electrode comprises a second conductive layer.

3. The force sensing device of claim 2 , wherein at least one of the first electrode or the second electrode further comprises a layer of variable resistance material.

4. 4. The force sensing device according to claim 1, wherein the first electrode is provided on a first substrate, and the second electrode is provided on a second substrate.

5. 5. A force sensing device according to claim 1, wherein the collapsible structure is configured to return from the collapsed configuration to an initial configuration after an applied force exceeding a predetermined magnitude.

6. 6. A force sensing device according to claim 1, wherein the collapsible structure is configured to expand in cross-sectional area in response to the applied force.

7. obtaining a force sensing device including a first electrode and a second electrode arranged to provide an electrical output in response to an applied force; and applying a force to the force sensing device that exceeds a predetermined magnitude; where A collapsible structure disposed within the force sensing device provides an electrical short in response to the applied force: A method for calibrating a force sensing device.

8. The electrical short provides a change in electrical resistance, and the method further comprises: Identifying a point of collapse of the collapsible structure by the change in electrical resistance: The method of claim 7 further comprising:

9. adjusting an output of a force sensing device in response to identifying said point of collapse; The method of claim 8 further comprising:

10. forming a force sensing device configured to provide an electrical output in response to an applied force, disposing a first electrode and a second electrode; and Placing a foldable structure within the force sensing device. wherein the collapsible structure is configured to provide an electrical short in response to an applied force when the applied force exceeds a predetermined magnitude: A method for manufacturing a force sensing device.

11. providing the first electrode on a first substrate; and providing the second electrode on a second substrate; The method of claim 10 further comprising:

12. applying a variable resistance material to the first electrode or the second electrode; The method of claim 10 or claim 11, further comprising:

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