Force sensing device and apparatus

Abstract

The invention relates to a force sensing device. The force sensing device comprises a floating element, a base and an intermediate shear spring connecting the floating element and the base together. An external force applied to the floating element is transmitted to the base via the shear spring. One or more non-contact displacement sensors are disposed below the floating element on the sensor mounting surface with a gap between the floating element and the sensor. When the floating element displaces due to an external force, the sensor measures the amount of displacement of the floating element entering the gap. This enables the measurement of the applied force on the basis of the elastic properties of the shear spring without direct contact. Multiple such force sensing devices can be combined together to form a composite force sensing apparatus, e.g., to simulate fruit and measure the force experienced by the fruit during post-harvest processing.

Description

Technical Field

[0001] This invention relates to a force sensing device. More specifically, but not exclusively, the invention relates to a force sensing apparatus that may comprise a number of force sensing devices adapted to simulate an article among many articles to be subjected to bulk material handling, transport, and / or storage operations, in order to help determine the impact forces and load forces applied to the article during such operations. More specifically, but not exclusively, the force sensing device can determine the additional environmental conditions it experiences. In particular, but not exclusively, the force sensing device simulates an apple, avocado, or pear by means of shape and weight. Background Technology

[0002] Numerous methodologies for force sensing are known, employing various physical principles. For example, strain gauges and similar sensors experience changes in resistance during deformation, and force can be calculated based on these changes. Another approach is to indirectly calculate force by deriving it from acceleration (e.g., calculated by an accelerometer or inertial measurement unit). However, known force sensing techniques suffer from drawbacks, particularly when incorporated into miniaturized force sensing arrangements.

[0003] For example, at a small scale, deformation-based force sensing arrangements in practical applications can become extremely sensitive to temperature. Even if the sensor itself is calibrated and produces accurate outputs over a wide sensor temperature range, the surrounding mechanical structure of the sensing arrangement will have independent temperature response characteristics that are often difficult to characterize and can lead to deformations detected by the sensor, thus resulting in force reading errors.

[0004] Force sensing based on acceleration may not have the same degree of temperature sensitivity problem, but it is completely unsuitable for measuring certain types of forces. For example, crushing forces may not produce (or produce very little) acceleration that can be detected by a sensor.

[0005] Other issues include the fact that many miniature sensors are easily damaged when the sensing arrangement is subjected to overload, and that they are generally not waterproof—size constraints make force-limiting mechanisms and waterproof housings difficult to implement.

[0006] One size-constrained application of known force sensing technology is associated with the fruit processing industry, where a significant portion of fruit may suffer mechanical damage during post-harvest processes (e.g., when moved / packed by industrial machinery). Bruisted or damaged fruit is discarded as waste, or at least its value is reduced.

[0007] To investigate potential causes of fruit damage during postharvest processing, a known technique involves using a sensing device shaped like a fruit (e.g., an apple) alongside the actual fruit during the postharvest process, continuously collecting data. Typically, acceleration-based force sensing is employed for this purpose, but the resulting readings are known to only provide a rough, at best, reflection of the actual forces being experienced by the fruit. Example of such a device is described in U.S. Patent No. 4,745,564.

[0008] Given that apples may be subjected to a wide range of temperatures during post-harvest processing (e.g., from 35 degrees Celsius at harvest to 4 degrees Celsius in cold storage), the sensing device needs to adapt to a large thermal range and provide accurate readings within that range. Therefore, there is a trade-off between reducing sensor size for a compact design and improving the precision of force readings on the surface of dummy apples, and the adverse effects of a wide temperature range on providing accurate force recordings over a considerable period.

[0009] Therefore, it is desirable to develop improved micro force sensing devices that will be able to better characterize applied forces in contexts with physical size constraints (e.g., to name just a few, in fruit-shaped force sensing devices as discussed above, or in other applications such as robotic gripping or tactile sensing).

[0010] The object of the present invention is to provide a miniature force sensing device that overcomes or at least partially mitigates some of the disadvantages mentioned above, or at least provides the public with a useful alternative. Summary of the Invention

[0011] According to a first aspect, the present invention broadly includes a force sensing device comprising: Floating components exhibit characteristics of being subjected to external forces; Base; A shear spring, surrounding the floating element or base, is located between the floating element and the base, and connects the floating element to the base in a manner that transmits external forces as shear forces to the base. One or more non-contact displacement sensors are located on a sensor mounting surface that is mounted on or forms part of a base and is disposed below a floating element with a gap therebetween. The displacement sensors are configured to each sense a corresponding portion of the floating element in response to displacement of an external force relative to the base in the direction of shear force.

[0012] On the other hand, the shear spring continuously surrounds the floating element or base.

[0013] On the other hand, the shear spring forms a waterproof seal between the floating element and the base.

[0014] According to another approach, the shear springs discontinuously wrap around the floating element or base, such that the shear springs exist in three or more spaced-apart regions between the floating element and the base.

[0015] On the other hand, the floating element is nested within the base, and a shear spring surrounds the floating element.

[0016] On the other hand, the base is nested within the floating element, and a shear spring surrounds the base.

[0017] On the other hand, the shear spring follows a meandering path between the floating element and the base.

[0018] On the other hand, the shear spring is held between the floating element and the base and is in a compressed state.

[0019] According to another perspective, the stiffness of a shear spring in the lateral direction is at least five times higher than its stiffness in the shear force direction.

[0020] On the other hand, the lateral thickness of the shear spring is less than 10mm.

[0021] According to another aspect, the force sensing device also includes a contact element integral with or joined to the floating element, the contact element extending from the floating element in a normal direction and including a contact surface for receiving external forces.

[0022] On the other hand, the contact element is basically triangular in shape.

[0023] On the other hand, the contact surface of the contact element is convex.

[0024] On the other hand, the contact surface of the contact element is concave.

[0025] According to another aspect, the floating element includes one or more engagement features of the engagement contact element.

[0026] According to another aspect, one or more engagement features are cavities that receive corresponding pins of contact elements.

[0027] On the other hand, the contact element and the floating element can be releasably engaged.

[0028] On the other hand, the base also includes a flange.

[0029] According to another aspect, the contact element also includes a lip that presses against the flange when the contact element is fully displaced from the floating element, thereby providing an upper limit for the displacement and thus for the measurable force.

[0030] According to another perspective, a shear spring includes an elastic body.

[0031] On the other hand, the sensor mounting surface is a circuit board to which one or more displacement sensors are electrically connected.

[0032] On the other hand, one or more displacement sensors are at least two displacement sensors.

[0033] According to another aspect, one or more displacement sensors are at least three displacement sensors arranged nonlinearly, so that the point where an external force is applied to the floating element can be calculated based on a combination of displacement measurement results.

[0034] According to another aspect, the displacement sensor consists of three displacement sensors arranged in an equilateral triangle around the central axis.

[0035] On the other hand, one or more displacement sensors are non-contact sensors.

[0036] On the other hand, one or more displacement sensors are MEMS sensors.

[0037] On the other hand, one or more displacement sensors are optical / laser sensors.

[0038] On the other hand, one or more displacement sensors are capacitive or inductive sensors.

[0039] On the other hand, the floating element, base, and shear spring are all arranged concentrically.

[0040] On the other hand, the force sensing device is basically triangular in shape.

[0041] On the other hand, the span of the force sensing device is less than 100mm in any dimension.

[0042] On the other hand, the span of the force sensing device is less than 60mm in any dimension.

[0043] According to another perspective, the ratio of the height of the force sensing device to the diameter of the lateral boundary is one-third or less.

[0044] According to another aspect, the present invention broadly includes a force sensing device comprising: Multiple force sensing devices, with a base connected together, Multiple force sensing devices can independently measure the external force applied to them.

[0045] On the other hand, multiple force sensing devices are arranged in a close-packed manner, thus presenting a force measurement surface with virtually no gaps.

[0046] On the other hand, the force measuring surface is basically spherical.

[0047] According to another aspect, the force measuring surface is formed by the contact surface of the force sensing device, which is mainly convex, but some of the contact surfaces are at least partially concave.

[0048] On the other hand, multiple force sensing devices each have different orientations.

[0049] According to another aspect, the force sensing device also includes a frame for mounting the force sensing device on a base.

[0050] According to another aspect, the frame is a polyhedral shape.

[0051] On the other hand, the frame is basically a triangular polyhedron.

[0052] On the other hand, the frame is basically icosahedral in shape.

[0053] According to another perspective, the frame is at least partially hollow.

[0054] According to another aspect, the frame includes multiple faces, each face having a recess, and one of the force sensing devices is disposed within the recess.

[0055] On the other hand, the size and shape of the force sensing device are set to mimic a type of fruit.

[0056] On the other hand, this type of fruit is the apple.

[0057] According to another aspect, the present invention broadly includes a force sensing device comprising: Internal components with external mating walls; An outer element has an inner joining wall, and an inner element is nested within the outer element; A shear spring, disposed between an outer joint wall and an inner joint wall, serves as an interface between an inner element and an outer element; the shear spring is a conformal elastic layer. One or more non-contact displacement sensors, In this design, one of the internal and external components is a base, and the other is a floating component. The external force applied to the floating component generates a shear motion relative to the base, controlled by the elastic shear deformation of the conformal elastic layer. One or more displacement sensors are located on a sensor mounting surface, which is mounted on or forms part of a base and is positioned below the floating element with a gap therebetween. The displacement sensors are positioned to measure the displacement of the floating element, thereby enabling the measured displacement to be used to calculate the external force applied to the floating element based on the pre-characterized elastic properties of the conformal elastic layer.

[0058] On the other hand, the internal element is the base, and the external element is the floating element.

[0059] On the other hand, the external element is the base, and the internal element is the floating element.

[0060] On the other hand, the meandering profiles of the outer and inner joint walls are complementary.

[0061] Other aspects of the invention will become apparent from the following description, which is given by way of example only and with reference to the accompanying drawings.

[0062] As used in this article, the term “and / or” means “and” or “or”, or both.

[0063] As used in this article, the “(s)” after a noun indicates the plural and / or singular form of that noun.

[0064] As used in this specification and claims, the term "comprising" means "consisting of at least in part...". When interpreting statements in this specification and claims that include this term, the feature beginning with the term in each statement must be present, but other features may also be present. Related terms such as "comprise" and "comprised" will be interpreted in the same manner.

[0065] In this specification, references to external sources of information, including patent specifications and other documents, are generally made for the purpose of providing background for discussing the features of the invention. Unless otherwise stated, references to such sources of information shall not be construed in any jurisdiction as an admission that such sources are prior art or form part of common general knowledge in the art.

[0066] For the purposes of this specification, when method steps are described in sequence, the sequence does not necessarily mean that the steps are ordered in chronological order unless there is no other logical way to interpret the sequence. Attached Figure Description

[0067] The invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1A An exploded perspective view of the force sensing device is shown. Figure 1B An exploded perspective view of the force sensing device is shown. Figure 2A A top view of the force sensing device is shown; Figure 2B A side sectional view of the force sensing device is shown; Figure 3A A bottom view of the force sensing device is shown; Figure 3B A side view of the force sensing device is shown; Figure 4A A simplified side sectional view of the shear spring is shown; Figure 4B A simplified perspective view of the floating element and its axis of motion is shown; Figure 4C A simplified side sectional view of a shear spring with multiple concentric sections is shown. Figure 4D A simplified perspective view of a shear spring with multiple stacked sections is shown; Figure 5A A perspective view of the force sensing device is shown; Figure 5B A perspective view of the frame of the force sensing device is shown; Figure 5C An exploded view of the force sensing device is shown; Figure 6A An exploded view of the frame and a single force sensing device with its contact elements is shown; Figure 6B A perspective view of a force sensing device with contact elements is shown; and Figure 6C An exploded view of a force sensing device with contact elements is shown. Detailed Implementation

[0068] Figures 1A to 6C The force sensing device 10 (and force sensing apparatus 30) are illustrated in the diagram. Figures 1A to 3B As shown more clearly in the diagram, the force sensing device 10 includes: a floating element 12, a base 14, and a shear spring 16 located between the floating element 12 and the base 14.

[0069] Force sensing device 10 is used to determine the force between floating element 12 and base 14. Base 14 may be mounted on or part of an object, and floating element 12 is subjected to the external force to be measured. Shear spring 16 connects floating element 12 to base 14 in a manner that transmits the external force acting on floating element 12 as a shear force to base 14. Shear spring 16 enables base 14 and floating element 12 to be displaced relative to each other in a restricted manner along the shear direction. This displacement is resisted by shear spring 16 in a spring-like manner.

[0070] The force sensing device 10 also includes one or more non-contact displacement sensors 20, each sensing a corresponding portion of the floating element 12 in response to an external force displacement relative to the base 14 along the shear force direction. The measured displacement facilitates the calculation of the external force applied to the floating element 12 based on the pre-characterized elastic properties of the shear spring 16.

[0071] Although the accompanying drawings depict a preferred configuration in which the floating element 12 is nested inside the base 14, making the floating element 12 the internal element and the base 14 the external element, the base 14 may alternatively be nested inside the floating element 12, thus making the base 14 the internal element. However, this reverse configuration may result in a larger overall size of the force sensing device 10.

[0072] The shear spring 16 surrounds either the floating element 12 or the base 14, depending on which is the internal element. This document will assume that the floating element 12 is the preferred configuration as the internal element, but it should be understood that the features described may be adapted to the opposite configuration.

[0073] For example, the main advantage of using the shear spring arrangement described above instead of the traditional axial spring arrangement is that the expansion or contraction of the components due to temperature changes does not cause as much distortion in the direction of the measured displacement. This means that the measurement error of external force due to thermal effects will not be too significant, thereby improving the accuracy of the force sensing device 10.

[0074] When a spring arrangement is scaled down by a certain factor, it typically becomes thinner and less stiff. For axial spring arrangements, this exacerbates sensitivity to thermal distortion and other distortions that produce force measurement errors. Because the shear spring arrangement of the present invention experiences less distortion in the direction of the measured displacement, the percentage error growth rate of the shear spring arrangement is lower than that of the axial spring arrangement when each arrangement is scaled down by an equal factor. Therefore, the smaller the force sensing device 10, the more pronounced the benefits described above become. Preferably, the force sensing device 10 has a span of less than 100 mm in any dimension (i.e., the diameter of its boundary sphere is less than 100 mm), and more preferably, a span of less than 60 mm in any dimension. Such a force sensing device 10 can be considered a “miniature” force sensing device.

[0075] The height-to-width ratio (height measured along the displacement measurement direction) of the force sensing device 10, and particularly its floating element 12 and shear spring 16, can also affect the temperature response. Generally, a larger height relative to width will weaken the temperature response and thus reduce error. However, this must be balanced with the expectation of keeping the force sensing device 10 compact and easy to install for practical use; for practical applications, a thinner shape (i.e., a larger width relative to height) may be more ideal. Other factors such as the stiffness and maximum rated force of the shear spring 16 may also be relevant to the ratio selection.

[0076] Preferably, the height of the force sensing device 10 is less than the diameter of the lateral boundary, and preferably, the ratio of height to boundary diameter is one-third or less, preferably at least one-seventh. In a preferred example, this ratio is approximately one-fifth.

[0077] Preferably, the shear spring 16 is thin-walled. Its cross-section along its path can be rectangular, and preferably, its width is significantly smaller than its height. The shear spring 16 is positioned between the outer engaging wall 13 of the floating element 12 and the inner engaging wall 15 of the base 14. The shear spring is connected (preferably, mechanically, thermally, and / or chemically bonded to) the outer engaging wall 13 of the floating element 12 and the inner engaging wall 15 of the base 14.

[0078] The shear spring 16 can be considered a conformal elastic layer because it conforms to the shapes of the outer joining wall 13 and the inner joining wall 15. Preferably, the shapes of the walls are complementary, so that the lateral thickness of the conformal elastic layer is approximately constant, such as... Figure 2A As shown in the image.

[0079] To enhance the force holding the shear spring 16 between the floating element 12 and the base 14, the shear spring is preferably compressed between them (i.e., between the outer engaging wall 13 and the inner engaging wall 15). This can be achieved, for example, by a press fit. This increases friction with the walls, thereby helping to better transmit the shear force. The interface between the shear spring 16 and the wall can also employ a keyway structure, which can also be used to enhance the holding force.

[0080] Preferably, the lateral thickness of the shear spring 16 is less than 10 mm in any orientation, and more preferably less than 6 mm, which helps limit the maximum displacement caused by shear deformation. This allows the sensing device 10 to be smaller and therefore more compact.

[0081] The shear spring 16 preferably follows a meandering path between the floating element 12 and the base 14, which is facilitated by the complementary meandering profiles of the outer engagement wall 13 and the inner engagement wall 15. This meandering shape increases the contact surface area, thereby enhancing adhesive strength and holding force. The meandering path increases the working length of the shear spring. This helps to distribute shear stress to avoid shear stress overload, which could otherwise cause the shear spring to separate from the base or the floating element. By deforming in multiple directions, the meandering path also better distributes stress (including stress that can be generated by thermal expansion / contraction) and improves vibration absorption. This helps protect the shear spring 16 from damage and extend its service life. However, various other shapes are equally applicable.

[0082] Preferably, the shear spring 16 continuously wraps around the floating element 12, i.e., it is formed as a continuous strip without gaps. In an alternative configuration, the shear spring 16 may discontinuously wrap around the floating element 12, thus allowing at least one gap. If more than one gap exists, the shear spring 16 may comprise a plurality of preferably equidistant segments. Minimizing the size of the gaps helps achieve the desired characteristics of the force sensing device 10, such as minimizing temperature response and preventing water ingress. When the shear spring 16 is continuous, it preferably forms a waterproof seal between the floating element 12 and the base 14.

[0083] Preferably, the shear spring 16 comprises an elastomer, such as silicone rubber. The elastomer may be an elastomer with room temperature vulcanization properties, which makes the shear spring 16 easier to manufacture. The elastomer is preferably a hyperelastic material because it can withstand large strains while still returning to its original shape and maintaining its mechanical properties.

[0084] like Figure 1A and Figure 2A As shown, the floating element 12 may include one or more engagement features 22, such as cavities as illustrated. These engagement features 22 enable the mounting of contact elements, which will be described in more detail later. Otherwise, they do not affect the function of the floating element 12, which may also optionally have other surface configurations.

[0085] like Figure 1B and Figure 3B As most clearly shown, the base 14 may include a flange 24. The flange 24 may assist in mounting the force sensing device 10, but it may also be combined with a contact element to perform a force limiting function, as will be described in more detail later.

[0086] The accompanying drawings depict the force sensing device 10 as generally triangular (and essentially equilateral), but various other shapes are also applicable. The triangle facilitates an efficient checkerboard arrangement of multiple force sensing devices 10, as described below. This also facilitates the positioning of the displacement sensor 20 in a preferred triangular configuration, as described below.

[0087] Preferably, the shapes of the floating element 12, the base 14, and the shear spring 16 all correspond to the overall shape of the force sensing device 10, thereby helping to reduce the overall size and save material usage. However, the floating element 12 may alternatively be a different shape (e.g., circular) from the base 14 (e.g., square). Preferably, the floating element 12, the base 14, and the shear spring 16 are at least partially concentric.

[0088] Figure 4AThe diagram, in simplified form, illustrates how the shear spring 16 deforms due to an external force, and how this results in a measurable displacement of the floating element 12. Specifically, the shear spring 16 undergoes elastic shear deformation, corresponding to a displacement Δx of the floating element 12. The external force F can be calculated based on the displacement Δx using pre-characterized elastic properties of the shear spring 16, such as its shear modulus (typically denoted by G). The shear modulus is a measure of the elastic shear stiffness of a material.

[0089] The force sensing device 10 is configured to measure the normal component of the external force F relative to the surface of the floating element 12. If the external force F is applied at a certain angle, then according to the above principle, the tangential component will generally not cause a predictable displacement. To ensure that the tangential force component or lateral expansion due to temperature changes does not interfere with the accurate measurement of the normal force component, preferably, the stiffness of the shear spring 16 in the lateral direction is much greater than its stiffness in the shear force direction (i.e., the direction of displacement of the floating element 12). For example, the stiffness of the shear spring 16 in the lateral direction can be at least five times higher.

[0090] like Figure 4B As shown, the shear spring 16 is preferably present in at least three or more spaced-apart regions (preferably equidistant) between the floating member 12 and the base 14. This can be a single segment of the shear spring 16, as shown, but it should be understood that a single segment may exist in more than one spaced-apart region.

[0091] Figure 4C and Figure 4D The diagram shows that the shear spring 16 can also have vertically or concentrically spaced segments. It should be understood that various arrangements of segments can work together to provide an elastic response characterizable for force measurement purposes, and thus multiple segments can be considered together to constitute the shear spring 16. However, dividing the shear spring 16 into such segments increases complexity and is therefore generally less preferred than a simpler (e.g., a single) arrangement.

[0092] Figure 4B The pitch and roll axes of the floating element 12 are also shown. If an external force F is applied to the floating element 12 in an eccentric direction, the floating element 12 may tilt along these axes (yaw is generally negligible). This tilting occurs in conjunction with the uneven shear deformation of the shear spring 16, because the deformation in some areas will be greater than in others. If only a displacement sensor 20 is used to measure the displacement of the floating element 12, the external force F will not be measured with the same accuracy, because not all parts of the floating element 12 will displace equally due to tilting.

[0093] In view of the above, preferably, more than one displacement sensor 20 is provided to better cope with the eccentric application of external forces. Two displacement sensors 20 can assist in coping with an axis tilt, but preferably, at least three displacement sensors 20 are arranged non-linearly (e.g., at the corners of an imaginary triangle or other polygon). Because if the floating member 12 tilts, the displacement sensors 20 will measure different displacement values, so the orientation of the floating member 12 and its displacement can be correctly characterized using standard algorithms. In addition to correcting the external force measurements, this can also determine the point on the floating element 12 where the external force F is applied (i.e., its Cartesian coordinates in the plane of the floating element 12) based on the combination of displacement measurement results.

[0094] While various arrangements of the displacement sensors 20 are applicable, a preferred example arrangement of three displacement sensors 20 arranged in an equilateral triangle around a central axis is shown in the previous figures. This is a particularly convenient arrangement that facilitates the calculations described above.

[0095] Various types of sensors can be used for displacement sensor 20, and can be selected based on the size of force sensing device 10. Since it is generally desirable for force sensing device 10 to be as small as possible, the sensor is preferably a MEMS sensor that is typically small in package size and well-suited for precise measurements over a small range.

[0096] The displacement sensors 20 are non-contact type because they are not incorporated into the shear spring 16 itself and can function without relying on contact, for example, by directly measuring shear strain. Examples of suitable non-contact sensors include: optical or laser sensors that can function based on the propagation time of light; and capacitive or inductive sensors that can function based on changes in capacitance or inductance when two elements move relative to each other.

[0097] Preferably, each displacement sensor 20 is located on a sensor mounting surface 18, which is mounted to or forms part of the base 14, as shown in the previous figures. This ensures that the displacement sensor 20 can be fixed relative to the base 14, which is important for accurate displacement measurement. It also ensures that the position of the sensor relative to the base 14 (and by extension relative to the floating element 12) can be accurately determined for computational purposes. Accurate positioning can be facilitated by through-holes or similar features on the sensor mounting surface 18.

[0098] The sensor mounting surface 18 can be disposed below the floating element 12, with a gap between them. Therefore, the displacement sensor 20 is mounted facing the floating element 12 and measures displacement as the floating element 12 moves into the gap. Preferably, the height of the gap is less than 10 mm, and more preferably less than 5 mm, which helps limit the size of the force sensing device 10. In a preferred example, the height of the gap can be as small as 1 mm. The design of the gap height and the selection of the displacement sensor 20 are interrelated, as the selected displacement sensor 20 must function adequately within a potentially small range of the gap height.

[0099] The sensor mounting surface 18 may be a circuit board with electrical connections to the displacement sensor 20. However, the circuitry may alternatively be located elsewhere, and the displacement sensor 20 may be operatively connected via wires.

[0100] The force sensing device 10 has various advantages over alternative arrangements.

[0101] First, as previously mentioned, the shear spring 16 provides a mechanical structure with temperature-responsive characteristics, whose temperature response is significantly weaker than that of an axial spring arrangement of similar size. This is particularly advantageous for miniaturizing the force sensing device 10.

[0102] Secondly, the shear spring 16 can provide a waterproof seal between the floating element 12 and the base, which can help protect the displacement sensor 20 and any other electronic components from moisture damage.

[0103] Third, using at least three displacement sensors 20 corresponding to different portions of the floating element 12 enables better accuracy and allows determination of the point of application of the external force F in addition to the magnitude of the force. This can be used in various applications where precise force measurement is required and the point of contact may change—some specific applications will be described later.

[0104] Fourth, shaping the shear spring 16 into a meandering path provides various benefits, including better distribution of stress and strain, improved vibration absorption performance, improved thermal expansion adaptability, and enhanced adhesive strength.

[0105] A force sensing device 30 including a force sensing element 10 will now be described.

[0106] like Figure 5A As shown, the force sensing device 30 may include a plurality of force sensing devices 10. Each force sensing device 10 has a base 14 connected together and can independently measure the external force applied to it. This effectively creates a composite force sensing device with a force measurement surface area larger than that of a single force sensing device 10, and also allows for geometries suitable for specific sensing applications.

[0107] like Figures 5B to 5C As shown, preferably, the force sensing device 30 includes a frame 32 for mounting a base 14 of the force sensing device 10. Therefore, the shape of the frame 32 determines the orientation of the force sensing device 10. However, in alternative configurations, the base 14 of the force sensing device 10 can be directly connected, connected via an intermediate connector, or integrally formed with each other.

[0108] Preferably, the plurality of force sensing devices 10 each have different orientations, thereby enabling them to measure external forces from different directions. However, in an alternative configuration (not shown), at least some areas of the force sensing device 30 may exist in which the plurality of force sensing devices 10 are presented in the same orientation, for example, to present a substantially flat force measuring surface, or to present the force sensing devices 10 at different heights.

[0109] To facilitate mounting of the force sensing device 10 in various orientations, the frame 32 can be substantially polyhedral in shape—where at least some (preferably all) of the faces 34 are fitted with the force sensing device 10. Preferably, the shape of each face 34 substantially corresponds to the shape of the force sensing device 10 it is fitted with, thereby enabling convenient installation and efficient use of surface area. Therefore, to correspond to the preferred configuration where the force sensing device 10 is substantially equilateral triangular, the preferred polyhedron for the frame 32 is a triangular-faced polyhedron, i.e., having faces 34 that are equilateral triangles. As shown in the figures, a preferred example is an icosahedron with twenty such faces 34. However, it should be understood that many other geometries are also feasible.

[0110] Preferably, the frame includes a plurality of surfaces 34, each surface having a recess 36 in which one of the force sensing devices 10 is disposed. If present, then the flange 24 of each force sensing device 10 can be positioned precisely outside the recess 36.

[0111] Preferably, the force sensing device 30 includes electronics that facilitate independent operation. Such electronics may include a battery, a charging interface, a real-time clock module, a memory storage medium (e.g., a removable SD card), an electronic controller for the displacement sensors 20 that interface with and manage them, and / or wireless communication hardware to facilitate (e.g., using Wi-Fi, Bluetooth, or radio protocols) the transmission of sensor data to external devices. However, for some "in-place" applications, it may be sufficient for the force sensing device 30 to be at least partially hardwired to external electronics via a direct wired connection to the force sensing device 10, thereby replacing some or all of these functions.

[0112] The electronics of the force sensing device 30 may include secondary sensors. Such secondary sensors can be used in conjunction with the measurement results from the force sensing device 10 and can also be managed by an electronic controller. Some degree of sensor fusion may occur between the data from the secondary sensors and the data from the force sensing device 10.

[0113] For example, inertial measurement units (IMUs) make impact loads from falling or dropping motions easier to identify and more comprehensively characterize in force-sensing data, as they are accompanied by corresponding acceleration readings. Tracking rotation / orientation using gyroscope and magnetometer data is also beneficial, for example, for better characterizing tumbling or pushing motions.

[0114] Another example of a secondary sensor that can be incorporated into the force sensing device 30 is a temperature sensor. Temperature readings can be used to respond to a pre-characterized temperature response of the mechanical components of the displacement sensor 20 or the force sensing device 10, for example, through correction in embedded software or in post-processing on an external device. Temperature readings can also be used for other purposes, such as battery management or general environmental monitoring.

[0115] Preferably, the frame 32 is at least partially hollow, allowing it to accommodate the electronic devices described above. It may provide compartments or mounting points for certain components and may incorporate externally accessible connector ports (e.g., according to the USB standard) for charging and / or data transfer.

[0116] like Figure 6A As shown, the force sensing arrangement 10, and more specifically, its floating element 12, is capable of engaging with the contact element 38. The purpose of the contact element 38 is to receive the external force to be measured and transmit it to the floating element 12. Therefore, the contact element 38 extends from the floating element 12 in the normal direction and includes a contact surface 40 for receiving the external force.

[0117] The shape of the contact surface 40 and the contact element 38 as a whole can be adapted to meet a specific application. Preferably, the shape of the contact element 38 substantially corresponds to the shape of the force sensing device 10. In a preferred example, the shape of the contact element 38 is substantially triangular.

[0118] Preferably, the contact surface 40 is convex, which helps to define a composite bending force measuring surface together with the contact surfaces 40 of other force sensing devices 10, as will be described later. However, depending on the specific application requirements, the contact surface 40 may alternatively be, for example, any other shape, such as flat or concave.

[0119] Preferably, the contact element 38 engages with the engagement feature 22 of the floating element 12, which can be formed as a cavity. The contact element 38 may include a plug 42 corresponding to the cavity (e.g., configured to press into the cavity).

[0120] The engagement between the contact element 38 and the floating element 12 can be releasable, which facilitates modularity because the contact element 38 can be replaced to meet different application requirements. Alternatively, the engagement can be designed to be permanent, which can be achieved by using an adhesive (e.g., applied to the cavity prior to the insertion plug 42).

[0121] In an alternative configuration, the contact element 38 may be integrated with the floating element 12, rather than being coupled to it.

[0122] Contact element 38 may include a lip 44 that extends beyond the periphery of floating element 12 and rests above base 14. Thus, contact element 38 can perform a force / displacement limiting function because when a sufficiently large external force is applied, lip 44 will press against base 14 (e.g., against its flange 24) or frame 32. This prevents any further displacement of floating element 12 and protects shear spring 16 and / or displacement sensor 20 from damage due to external forces exceeding a certain threshold. The mechanical design of adjustable components (taking into account the elastic characteristics of shear spring 16) can be used to set the upper limit of force / displacement to a desired value.

[0123] like Figures 6B to 6C As shown, the force sensing device 30 can provide a force measuring surface, which is defined by the contact surface 40 of a plurality of contact elements 38 associated with the force sensing device 10.

[0124] Therefore, the shape of the force measuring surface is determined by the shape of the contact surfaces 40, which can all be substantially the same or at least similar. Alternatively, some or all of the contact surfaces 40 can have unique geometries.

[0125] Preferably, the multiple force sensing devices 10 (and extending to their contact elements 38) are arranged in a close-packed manner, thereby presenting a force measurement surface with virtually no gaps. Minimizing the size of the gaps enables better force sensing coverage because external forces cannot be easily applied into the gaps, where they will not be sensed.

[0126] In a preferred example as shown in the accompanying drawings, the force measuring surface is substantially spherical. This can be achieved by the frame 32 having a suitable polyhedral shape. The contact surfaces 40 are also convex in shape, so that they can collectively define a substantially spherical surface. However, one or more of the contact surfaces 40 may be at least partially concave, for example, to mimic the concave shape surrounding the stem of a typical apple.

[0127] In one configuration, the size and shape of the force sensing device 30 can be set to mimic a fruit, preferably an apple. This allows the force sensing device 30 to be transported along with the real fruit during the post-harvest process and to collect force data that indicates how, when, or where the fruit has experienced mechanical damage. A spherical shape, as described above, can be suitable for mimicking a fruit. For the example of mimicking an apple, the diameter of the force sensing device 30 is preferably between 40 mm and 120 mm.

[0128] The force sensing device 30 can be video-recorded as it travels through the post-collection process, for example, using one or more external cameras configured to observe the process and track the force sensing device 30. The timestamps of the sensor data stream and the video are matched, which enables visual analysis of the video to help identify where the device 30 is subjected to potentially damaging forces, the magnitude and cause of the forces, the frequency of the forces, the location of the forces on the device 30, and the orientation of the forces relative to the horizontal plane.

[0129] Preferably, the force sensing device 30 is configured to simultaneously monitor all external forces F, such as those detectable from any force sensing device within its force sensing unit 10, during operation. This enables the characterization of external forces impacting from various directions when the force sensing unit 10 is in different orientations. This can include crushing forces, which are particularly useful for measurements in fruit simulation applications.

[0130] Preferably, at least some processing of the sensor data is performed on the force sensing device 30, for example, via its electronic controller. This processing may include signal filtering, force calculation, temperature correction, or other sensor fusion. This is preferably performed by embedded software, but may be performed at least partially by dedicated hardware electronics. However, some or all of the processing of the sensor data may be performed on an external device to which the data is transmitted.

[0131] For example, more complex sensor fusion or other tasks, especially those that are more computationally intensive, can preferably be performed on an external device. One such task could be synchronizing and playing back sensor data streams with corresponding video recordings as described above.

[0132] Another example of a task that can be performed on an external device is to realize a three-dimensional visualization of the force sensing device 30 and its sensor data stream. For example, the external device can display a 3D model of the force sensing device 30 and convert the sensor data stream (whether it is streamed in real time or played back later) into a graphical indication (e.g., using color mapping) of the external force at the corresponding location on the force sensing device 30. If an inertial measurement unit is provided onboard, the 3D model can also be animated to rotate and / or translate in space based on the corresponding sensor data.

[0133] Having multiple force sensing devices 10 in the force sensing device 30 has several advantages over other types of force sensing devices.

[0134] First, by providing multiple independent force sensing devices 10 in different orientations, crushing / compression forces can be accurately characterized, which would not be possible with acceleration-based force sensing. This is particularly relevant to fruit mimicry applications.

[0135] Second, the structure of the force sensing device 10 facilitates a checkerboard grid arrangement to achieve a force measurement surface with virtually no gaps, which helps to ensure that all external forces of interest are captured.

[0136] Taking the force sensing device 30, which mimics an apple, as an example, setting up at least ten force sensing devices in a checkerboard pattern might be sufficient. However, in the most preferred form, there are twenty force sensing devices 10 arranged in a checkerboard pattern, which is particularly convenient for a triangular checkerboard pattern. Furthermore, it has been found that with this number, each force sensing device 10 can only contact one apple, meaning that only one force source is applied to a force sensing device 10.

[0137] Third, since the shear spring 16 can provide a waterproof seal between each base 14 and the floating element 12, the force sensing device 10 can be mounted such that the internal space of the force sensing device 30 (e.g., at least part of the hollow interior of the frame 32) is inherently waterproof. This is beneficial for isolating the internal electronics from moisture damage.

[0138] Many structural changes and a wide variety of embodiments and applications of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims.

[0139] The invention may also be broadly defined as any part, element, and feature individually or collectively mentioned or indicated in the description of this application, and any or all combinations of any two or more of such part, element, or feature, and where a particular whole is mentioned herein as having a known equivalent in the field to which the invention relates, such known equivalents are deemed to be incorporated herein as if described separately.

Claims

1. A force sensing device, comprising: Floating components exhibit characteristics of being subjected to external forces; Base; A shear spring surrounds the floating element or the base, the shear spring being located between the floating element and the base, and connecting the floating element to the base in such a way that it transmits the external force as a shear force to the base; One or more non-contact displacement sensors are located on a sensor mounting surface, which is mounted on or forms part of the base and is disposed below the floating element with a gap therebetween. The displacement sensors are configured to each sense a corresponding portion of the floating element in response to the displacement of the external force relative to the base along the shear force direction.

2. The force sensing device according to claim 1, wherein, The shear spring continuously surrounds the floating element or the base.

3. The force sensing device according to claim 2, wherein, The shear spring forms a waterproof seal between the floating element and the base.

4. The force sensing device according to claim 1, wherein, The shear springs are discontinuously wrapped around the floating element or the base, such that the shear springs exist in three or more spaced-out regions between the floating element and the base.

5. The force sensing device according to any one of claims 1 to 3, wherein, The floating element is nested within the base, and the shear spring surrounds the floating element.

6. The force sensing device according to any one of claims 1 to 3, wherein, The base is nested within the floating element, and the shear spring surrounds the base.

7. The force sensing device according to any one of the preceding claims, wherein, The shear spring follows a meandering path between the floating element and the base.

8. The force sensing device according to any one of the preceding claims, wherein, The shear spring is held between the floating element and the base and is in a compressed state.

9. The force sensing device according to any one of the preceding claims, wherein, The stiffness of the shear spring in the lateral direction is at least five times higher than its stiffness in the shear force direction.

10. The force sensing device according to any one of the preceding claims, wherein, The lateral thickness of the shear spring is less than 10 mm.

11. The force sensing device according to any one of the preceding claims further includes a contact element integral with or joined to the floating element, the contact element extending from the floating element in a normal direction and including a contact surface for receiving the external force.

12. The force sensing device according to claim 11, wherein, The contact element is basically triangular in shape.

13. The force sensing device according to claim 11 or 12, wherein, The contact surface of the contact element is convex.

14. The force sensing device according to claim 11 or 12, wherein, The contact surface of the contact element is concave.

15. The force sensing device according to any one of claims 11 to 14, wherein, The floating element includes one or more engagement features that engage with the contact element.

16. The force sensing device according to claim 15, wherein, The one or more engagement features are cavities that receive the corresponding pins of the contact elements.

17. The force sensing device according to any one of claims 11 to 16, wherein, The contact element is releasably engaged with the floating element.

18. The force sensing device according to any one of claims 11 to 17, wherein, The base also includes a flange.

19. The force sensing device according to claim 18, wherein, The contact element also includes a lip that presses against the flange when the contact element is fully displaced from the floating element, thereby providing an upper limit for the displacement and thus for the measurable force.

20. The force sensing device according to any one of the preceding claims, wherein, The shear spring includes an elastic body.

21. The force sensing device according to any one of the preceding claims, wherein, The sensor mounting surface is the circuit board to which the one or more displacement sensors are electrically connected.

22. The force sensing device according to any one of the preceding claims, wherein, The one or more displacement sensors are at least three displacement sensors arranged nonlinearly, so that the point where the external force is applied to the floating element can be calculated based on a combination of displacement measurement results.

23. The force sensing device according to claim 22, wherein, The displacement sensors are three displacement sensors arranged in an equilateral triangle around the central axis.

24. The force sensing device according to any one of the preceding claims, wherein, The one or more displacement sensors are MEMS sensors.

25. The force sensing device according to any one of the preceding claims, wherein, The one or more displacement sensors are optical / laser sensors.

26. The force sensing device according to any one of claims 1 to 24, wherein, The one or more displacement sensors are capacitive or inductive sensors.

27. The force sensing device according to any one of the preceding claims, wherein, The floating element, the base, and the shear spring are all arranged concentrically.

28. The force sensing device according to any one of the preceding claims, wherein, The force sensing device is essentially triangular in shape.

29. A force sensing device, comprising: The plurality of force sensing devices according to any one of claims 1 to 28, wherein the force sensing devices have bases connected together, Each of the multiple force sensing devices can independently measure the external force applied to it.

30. The force sensing device according to claim 29, wherein, The multiple force sensing devices are arranged in a close-packed manner, thus presenting a force measurement surface with virtually no gaps.

31. The force sensing device according to claim 30, wherein, The force measuring surface is substantially spherical.

32. The force sensing device according to any one of claims 29 to 31, wherein, The plurality of force sensing devices each have a different orientation.

33. The force sensing device according to any one of claims 29 to 32, further comprising a frame for mounting the base of the force sensing device.

34. The force sensing device according to claim 33, wherein, The frame is in the shape of a polyhedron.

35. The force sensing device according to claim 34, wherein, The frame is basically a triangular polyhedron.

36. The force sensing device according to claim 35, wherein, The frame is essentially icosahedral in shape.

37. The force sensing device according to any one of claims 33 to 36, wherein, The frame is at least partially hollow.

38. The force sensing device according to any one of claims 33 to 37, wherein, The frame includes multiple surfaces, each surface having a recess, and one of the force sensing devices is disposed within the recess.

39. The force sensing device according to any one of claims 29 to 38, wherein, The size and shape of the force sensing device are designed to mimic a type of fruit.

40. The force sensing device according to claim 39, wherein, The type of fruit mentioned is the apple.

41. A force sensing device, comprising: Internal components with external mating walls; An external element having an internal engagement wall, wherein the internal element is nested within the external element; A shear spring is disposed between the outer joint wall and the inner joint wall to provide an interface between the inner element and the outer element; the shear spring is a conformal elastic layer. as well as One or more non-contact displacement sensors, In this configuration, one of the internal and external elements is a base and the other is a floating element. An external force applied to the floating element produces a shear motion relative to the base, controlled by the elastic shear deformation of the conformal elastic layer. The one or more displacement sensors are located on a sensor mounting surface, which is mounted on or forms part of the base and is disposed below the floating element with a gap therebetween. The displacement sensors are positioned to measure the displacement of the floating element, thereby enabling the measured displacement to be used to calculate the external force applied to the floating element based on the pre-characterized elastic properties of the conformal elastic layer.

42. The force sensing device according to claim 41, wherein, The internal element is the base, and the external element is the floating element.

43. The force sensing device according to claim 41, wherein, The external element is the base, and the internal element is the floating element.

44. The force sensing device according to any one of claims 41 to 43, wherein, The meandering profiles of the outer and inner joint walls are complementary.

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