Methods and devices for measuring a mechanical force

Abstract

Sensor device for sensing a mechanical force, comprising: a substrate comprising one or more magnetic sensors (M1, M2, M3); an elastomer having a first surface area (111) fixedly arranged relative to the substrate, and having a second surface area (112) for receiving said force (F); magnetic material (104) arranged inside the elastomer such that the magnetic material will move when said force is exerted upon the second surface area (112); one or more pressures or stress sensors (P1, P2, P3) for sensing a pressure or stress induced by said force (F); a processing circuit (1130) for determining one or more force components of the force (F) exerted upon the second surface area (112), based on the sensor signals from the magnetic and / or pressure sensors; the magnetic sensors and the pressure sensors having a fixed relative position. Method (1000) of measuring a force.

Description

[0001] METHODS AND DEVICES FOR MEASURING A MECHANICAL FORCE

[0002] Field of the invention

[0003] The present invention relates in general to the field of methods and devices for measuring a mechanical force, and more specifically to methods and force sensors or tactile sensors as may be used in industrial and robotic applications for gripping and / or lifting objects.

[0004] Background of the invention

[0005] Tactile sensors for industrial applications and robotic applications are known in the art. They may comprise for example piezo-resistive, piezo-capacitive, piezo-electric or barometric sensing elements. Robotic grippers comprising two or more fingers comprising such tactile sensors can be used for grasping and lifting objects.

[0006] Different types of sensor devices exists, each with their advantages and disadvantages, for example in terms of sensitivity, cost, size, accuracy, measurement range, robustness against external influences, error-detection capabilities, etc. Often two or more of these requirements conflict with each other, and a compromise is chosen.

[0007] There is always room for improvements or alternatives.

[0008] Summary of the invention

[0009] It is an object of embodiments of the present invention to provide a sensor device, e.g. a force sensor device or a tactile sensor device capable of measuring a force (e.g. capable of measuring 1 force component (e.g. a force component perpendicular to a substrate, also known as "normal force component"), or 2 force components (e.g. two shear force components, or a normal force component and a shear force component), or 3 force components (e.g. a normal force component and two shear force components).

[0010] It is also an object of embodiments of the present invention to provide a method of measuring a force (e.g. measuring 1 force component, or 2 force components, or 3 force components of said force).

[0011] It is an object of embodiments of the present invention to provide a method and a device for measuring a force with high or increased accuracy or sensitivity (especially for relatively small forces) over a high or increased measurement range. Such a method or device is capable of measuring both relatively small and relatively large forces with a good or decent accuracy. The improved accuracy may apply for at least 1 force component, or for at least 2 force components, or for at least 3 force components. The improved accuracy may be related to a reduced hysteresis.

[0012] It is an object of embodiments of the present invention to provide such a method and / or such a device having an improved reliability or robustness or trustworthiness of the measurement, e.g. by providing an output which may be slightly less accurate but which is highly insensitive to external disturbances (e.g. an external magnetic field). It is an object of embodiments of the present invention to provide such a method and / or such a device which is not only capable of measuring a force, but is also capable of detecting an error (e.g. an inconsistency or a defect or an unreliable measurement).

[0013] These and other objectives are accomplished by embodiments of the present invention.

[0014] According to a first aspect, the present invention provides a sensor device for sensing a mechanical force (e.g. for sensing one or more components of said mechanical force), the sensor device comprising: a substrate (e.g. a semiconductor substrate or a printed circuit board) comprising one or more magnetic sensors (e.g. at least three 2D magnetic pixels, or at least four 2D magnetic pixels, or at least three 3D magnetic pixels, or at least four 3D magnetic pixels) for sensing one or more characteristics of a magnetic field, and for providing one or more first sensor signals, e.g. a first set of at least three sensor signals (e.g. ml, m2, m3); an elastomer having a first surface area fixedly arranged relative to the substrate (e.g. fixedly connected to said substrate, directly or indirectly), and having a second surface area for receiving said force that needs to be measured; magnetic material (e.g. a permanent magnet and / or magnetic powder and / or magnetic particles) for generating said magnetic field, the magnetic material being arranged or embedded inside the elastomer such that the magnetic material will move when said force is exerted upon the second surface area; one or more pressure or stress sensors, e.g. at least one pressure sensor, or at most one pressure sensor, or at least three pressure or stress sensors (e.g. Pl, P2, P3), arranged for sensing (e.g. directly or indirectly) a pressure or stress induced by said force, and configured for providing one or more second sensor signal, e.g. a set of at least three sensor signals (e.g. pl, p2, p3); a processing circuit configured for determining one or more force components (e.g. only one force component, e.g. a normal force component, or a shear force; or two force components, e.g. a normal force component and a shear force; or two shear force components; or three orthogonal force components Fx, Fy, Fz) of the force exerted upon the second surface area based on said one or more first sensor signal and said one or more second sensor signal (e.g. based on the first set of at least three sensor signals and based on the second set of at least three sensor signals); and wherein the one or more magnetic sensor and the one or more pressure or stress sensor have a fixed position relative to each other.

[0015] It is an advantage of using "magnetic sensing", that such the sensor can measure very small forces with a high sensitivity (albeit over a relatively small measurement range). This is beneficial when then sensor is used for touching (e.g. gripping, clamping) delicate objects. It is an advantage of using "pressure sensing", that such the sensor can measure over a relatively high measurement range (albeit with a reduced sensitivity). By using both sensor types in a single device, the sensor device of the present invention combines the best of both worlds. As far as the inventors are aware, a combination of a magnetic force sensor and a pressure sensor does not exist yet. But even if it would, the present invention is not a mere combination of two existing technique, but in preferred embodiments furthermore adds error detection capabilities, and / or a more reliable measurement than existing sensor devices.

[0016] It is an advantage of this sensor device (e.g. force sensor device, or tactile sensor device) that it can measure a force with an increased accuracy, and / or with an increased sensitivity, and / or over a larger measurement range. Such a sensor device is very well suited for use as a "tactile sensor" in robotic applications.

[0017] It is also an advantage that the one or more force components can be measured in a redundant manner, by using two different types of sensors, which allows error detection in at least a portion of the measurement range, and / or allows for a more robust detection (e.g. the pressure sensors are insensitive to a magnetic disturbance field; but when using a gradient measurement, also the magnetic sensors are highly insensitive to a magnetic disturbance field).

[0018] The elastomer functions as a transducer, to "transfer" the force exerted upon the second contact surface to the one or more pressure or stress sensors.

[0019] The one or more magnetic sensors may be mounted to, or embedded in said substrate.

[0020] The one or more pressure or stress sensor may also be mounted to, or embedded in said substrate.

[0021] The one or more pressure or stress sensors may comprise for example one or more piezo- resistive, piezo-capacitive, piezo-electric or barometric sensing elements. The pressure or stress sensor may comprise a micro-electromechanical (MEMS) structure, e.g. a membrane.

[0022] Alternatively, the sensor device may comprise a second substrate, separate from the first substrate, but having a fixed position relative to the first substrate, and the one or more pressure or stress sensor may be mounted to, or embedded in the second substrate.

[0023] If the first and second substrate are two separate substrates, they are preferably arranged parallel to each other.

[0024] Preferably, the substrate comprising the one or more magnetic sensors (also referred to as "the substrate" or "the first substrate") is a rigid substrate (e.g. a semiconductor substrate, a semiconductor die, or a printed circuit board).

[0025] Preferably, the second substrate comprising the one or more pressure or stress sensors is a rigid substrate (e.g. a semiconductor substrate, a semiconductor die, or a printed circuit board).

[0026] In an embodiment, the first substrate comprising the magnetic sensor(s) and the second substrate comprising the pressure or stress sensor(s) is one and the same semiconductor substrate, i.e. a single semiconductor substrate, e.g. a single semiconductor die, e.g. as illustrated in FIG. 1 to FIG. 4, FIG. 14, FIG. 15.

[0027] In an embodiment, the first substrate comprising the magnetic sensor(s) and the second substrate comprising the pressure or stress sensor(s) is one and the same printed circuit board (PCB), i.e. a single PCB, e.g. as illustrated in FIG. 7A or FIG. 7B or FIG. 14. In an embodiment, the first substrate comprising the one or more magnetic sensors and the second substrate comprising the pressure or stress sensors are two separate substrates, and the first substrate is a semiconductor substrate, and the second substrate is a printed circuit board (PCB), e.g. as illustrated in FIG. 5 and FIG. 6.

[0028] In an embodiment, the first and the second substrate are two separate semiconductor substrates, incorporated in a single semiconductor package (chip), e.g. as illustrated in FIG. 16 or FIG. 17).

[0029] In an embodiment, the first and the second substrate are two separate semiconductor substrates, incorporated in two separate semiconductor packages (chips), mounted on opposite sides of a third substrate, e.g. a printed circuit board, e.g. as illustrated in FIG. 18 or FIG. 19).

[0030] In an embodiment, said at least three magnetic sensors comprise three 2D magnetic pixels, or comprise four 2D magnetic pixels, or comprise three 3D magnetic pixels, or comprise four 3D magnetic pixels.

[0031] If the sensor device is for example implemented in a chip or a module or a printed circuit board, said chip or module or printed circuit board may provide a first output signal indicative of the measured force or force component(s) to an external system controller, e.g. an ECU (electronic control unit). If the system controller is provided (e.g. mounted) on the same module or PCB, the first output signal indicative of the measured force or force component(s) may still be output by the processing circuit, but does not have to be output by the PCB.

[0032] In an embodiment, the sensor device is configured for measuring a single force component, e.g. Fz oriented in a direction perpendicular to, or substantially perpendicular to the substrate.

[0033] In an embodiment, the sensor device is configured for measuring three orthogonal force components.

[0034] In certain embodiments, the sensor device is configured to detect a strength of a magnetic disturbance field and / or to detect a mismatch between the values given by the two types of transducers (magnetic versus pressure), and upon such detection the sensor device may provide a warning message and / or stop trusting the values provided by the magnetic sensors, and solely rely on the values obtained from the pressure sensors, even for relatively small forces, resulting in a loss of resolution / precision but still returning accurate values. Such a sensor device is highly robust.

[0035] The one or more pressure or stress sensors may be located at the first surface area, but that is not absolutely required. They may for example be arranged lower than said first surface area, but functionally connected thereto, e.g. via a portion of a plastic mould, or via an amount of air or gas that is trapped between the pressure / stress sensors and the elastomer. The gas may be nitrogen-gas or another suitable gas.

[0036] The pressure or stress sensors may be in direct or indirect mechanical contact with the elastomer, e.g. in direct mechanical contact with the elastomer (e.g. as illustrated in FIG. 4, FIG. 6), e.g. in indirect mechanical contact via a plastic mold compound (e.g. as illustrated in FIG. 1, FIG. 2, FIG. 5), e.g. indirectly via an enclosed amount of air or gas (e.g. in a variant of FIG. 7B where the pressure sensors are located within the cavity), e.g. indirectly via an enclosed amount of air or gas and a plastic mold compound (not shown). If the contact is indirect via an amount of air or gas, then the force applied to the elastomer will first compress said amount of air or gas, and this amount of compressed air or gas will exert a pressure upon the pressure or stress sensors. When a force is exerted upon the elastomer, the gas will be compressed, and will transfer a force or stress upon the pressure / stress sensors.

[0037] In an embodiment, the number of magnetic sensors (#MS) is only one, and the number of pressure or stress sensors (#PS) is only one.

[0038] In an embodiment, #MS is one, and #PS is at least two.

[0039] In an embodiment, #MS is one, and #PS is at least three.

[0040] In an embodiment, #MS is two, and #PS is only one.

[0041] In an embodiment, #MS is two, and #PS is only two or at least two.

[0042] In an embodiment, #MS is two, and #PS is only three or at least three.

[0043] In an embodiment, #MS is three, and #PS is only one.

[0044] In an embodiment, #MS is three, and #PS is only two or at least two.

[0045] In an embodiment, #MS is three, and #PS is only three or at least three.

[0046] In an embodiment, #MS is four, and #PS is only one.

[0047] In an embodiment, #MS is four, and #PS is only two or at least two.

[0048] In an embodiment, #MS is four, and #PS is only three or at least three.

[0049] In an embodiment, #MS is at least four, and #PS is only one.

[0050] In an embodiment, #MS is at least four, and #PS is only two or at least two.

[0051] In an embodiment, #MS is at least four, and #PS is only three or at least three.

[0052] In an embodiment, the number of magnetic sensors is at least three, and the number of pressure or stress sensors is only one.

[0053] In an embodiment, the number of magnetic sensors is at least three, and the number of pressure or stress sensors is at least three.

[0054] In an embodiment, the number of magnetic sensors is equal to the number of pressure sensors or stress sensors.

[0055] In an embodiment, the number of magnetic sensors is different from the number of pressure sensors or stress sensors.

[0056] In an embodiment, the one or more magnetic sensors are one or more detection coils or inductors, e.g. planar coils, e.g. implemented in a multi-layer printed circuit board or in the "interconnection stack" (sometimes also referred to as "metal stack") of a semiconductor substrate. The one or more detection coils may be configured for sensing one or more characteristics of an alternating magnetic field. In this case, the magnetic material may be an electrically conductive magnetic material, for example an electrically conductive soft magnetic material, or an electrically conductive ferromagnetic material. The electrically conductive magnetic material may be arranged for indirectly generating a secondary magnetic field in response to a primary magnetic field generated by one or more excitation coils, which may also be implemented in said printed circuit board or in said "interconnection stack" of the semiconductor substrate. The one or more excitation coils may be located in the vicinity of the detection coil.

[0057] In an embodiment, the one or more magnetic sensors are horizontal Hall elements, and the one or more stress sensors comprise one or more piezo-electrical strips, e.g. a plurality of piezo-electrical strips arranged around respective horizontal Hall elements. In this embodiment, the locations of the stress sensors are the same locations as the locations of the magnetic sensors.

[0058] In an embodiment, the sensor device comprises only one permanent magnet.

[0059] In an embodiment, the magnet is a two-pole magnet, or a four-pole magnet.

[0060] The magnet may have a cylindrical shape, or a disk shape, or a prism shape with a polygonal cross-section in a plane parallel to the substrate (e.g. triangular, square, hexagonal, octagonal).

[0061] The magnet may be magnetized in a direction perpendicular to the substrate.

[0062] In an embodiment, the magnet may have a cylindrical shape having a predefined radius Rm, and the magnetic sensors are arranged on a first virtual circle having a radius Rl. A ratio (Rl / Rm) may be a value in the range from 0.5 to 2.0, or from 0.8 to 1.2.

[0063] In an embodiment, an orthogonal projection of a centre of the magnet on the substrate (e.g. single substrate or first substrate), and an orthogonal projection of the centre of the first circle (upon which the magnetic sensors are located) upon said substrate substantially coincide.

[0064] In an embodiment, an orthogonal projection of a centre of the magnet upon the substrate, and an orthogonal projection of the centre of the second circle (upon which the pressure or stress sensors are located) upon said substrate substantially coincide.

[0065] In an embodiment, the semiconductor substrate may be surrounded, at least partially, by a plastic moulding compound. The elastomer may be applied on top of the plastic moulding compound, and the elastomer may be in direct mechanical contact with the pressure / stress sensors (e.g. via an opening in the plastic moulding compound), or may be in indirect mechanical contact with the pressure / stress sensors through the plastic moulding compound.

[0066] In an embodiment, the substrate is a semiconductor substrate. The one or more, e.g. at least three magnetic sensors may be embedded in said semiconductor substrate. The one or more, e.g. at least three pressure sensors or stress sensors may also be embedded in said semiconductor substrate.

[0067] In an embodiment, the semiconductor device may comprise a lead frame and / or a plurality of leads (also known as pins).

[0068] In an embodiment, an orthogonal projection of a periphery of the elastomer on a plane parallel to the substrate is larger than an orthogonal projection of a periphery of the moulding compound, e.g. as illustrated in FIG. 5. In an embodiment, an orthogonal projection of a periphery of the elastomer on a plane parallel to the substrate is smaller than an orthogonal projection of a periphery of the moulding compound, e.g. as illustrated in FIG. 1.

[0069] In an embodiment, the semiconductor substrate is surrounded by a plastic moulding compound (also referred to as "package"), and the elastomer is situated on top of the moulding compound. The moulding compound may be in direct contact with the magnetic sensors and may be in direct contact with the pressure sensors or stress sensors, and the elastomer may be in direct contact with the moulding compound, e.g. as illustrated in FIG. 1A and FIG. 2. Thus the elastomer may have indirect mechanical contact with the pressures sensors or stress sensors.

[0070] In an embodiment, the moulded package may have a recess situated above the semiconductor substrate, and the elastomer may be situated in and above said recess (e.g. as illustrated in FIG. 2 or FIG. 3). The elastomer may be in direct contact with the pressure sensors or stress sensors (e.g. as illustrated in FIG. 3), or may be in indirect contact with the pressure sensors (e.g. as illustrated in FIG. 2).

[0071] In an embodiment, the moulded package may have a recess situated above the semiconductor substrate, and the elastomer may be applied above said recess and an amount of air or gas may be enclosed in said recess. During use, the cavity may function as a compression chamber, and the air or the gas inside that chamber may pass the mechanical force or pressure onto the pressure or stress sensors.

[0072] In preferred embodiments, the sensor device further comprises at least one temperature sensor. This temperature sensor may be incorporated into the semiconductor substrate, or may be a discrete temperature sensor. The processing circuit may be configured to estimate a temperature of the elastomer, based on the measured temperature, and to take this estimated temperature into account when determining the force exerted upon the elastomer. Indeed, the elastomer may become more flexible at higher temperatures, hence the magnet displacement may be temperature dependent.

[0073] In an embodiment, the substrate is a printed circuit board (PCB), and the one or more, e.g. at least two or at least three magnetic sensors are incorporated in a first packaged device mounted on said PCB, and the one or more, e.g. at least two or at least three pressure sensors are discrete components also mounted on said PCB, e.g. arranged around the first packaged device (e.g. as illustrated in FIG. 5 and FIG. 6).

[0074] In an embodiment, the substrate is a printed circuit board (PCB), and each of the one or more magnetic sensors and each of the one or more pressure sensors is a discrete component mounted on said PCB (e.g. as illustrated in FIG. 7B).

[0075] In an embodiment, some or all of the one or more magnetic sensors or "magnetic sensor units" are one-dimensional (ID) magnetic pixels, e.g. horizontal Hall-elements, each configured for measuring a magnetic field component Bz at the respective location. In an embodiment, some or all of the one or more magnetic sensors or "magnetic sensor units" are two-dimensional (2D) magnetic pixels. Each such magnetic sensor unit may e.g. comprise two vertical Hall elements, configured for measuring a Bx and a By-component. Or each such magnetic sensor unit may e.g. comprise an integrated magnetic concentrator (IMC) and two Horizontal Hall elements arranged near a periphery of the IMC, 180° spaced apart.

[0076] In an embodiment, some or all of the one or more magnetic sensors or "magnetic sensor units" are three-dimensional (3D) magnetic pixels. Each such magnetic sensor unit may e.g. comprise a horizontal Hall element and two or four vertical Hall elements located adjacent or around the horizontal Hall element. Or each such magnetic sensor unit may e.g. comprise a circular IMC and four horizontal Hall elements arranged near a periphery of the IMC, angularly spaced apart by multiples of 90°.

[0077] In an embodiment, the second surface area has a dome shape. Such a surface area may be very well suited for gripping applications.

[0078] In an embodiment, the substrate comprises said one or more magnetic sensors and also comprises said one or more pressure or stress sensors. This substrate may also be referred to as "single substrate" or "single semiconductor substrate".

[0079] In an embodiment, the substrate comprising said one or more magnetic sensors is a first substrate, and the sensor device further comprises a second substrate, and the second substrate comprises said one or more pressure or stress sensors.

[0080] In an embodiment, the first substrate is a first semiconductor substrate, and the second substrate is a second semiconductor substrate, and the one or more magnetic sensors (e.g. Ml, M2, M3) are embedded in the first semiconductor substrate, and the one or more pressure or stress sensors (e.g. Pl, P2, P3) are embedded in the second semiconductor substrate. Examples of such sensor devices are shown e.g. in FIG. 1A to FIG. 4, and FIG. 14 and FIG. 15.

[0081] The first and the second substrate may be a single semiconductor substrate, e.g. a single silicon substrate, e.g. a single CMOS die. This single substrate may be over-moulded to form a packaged semiconductor device (also known as "chip").

[0082] The first and the second substrate may be two separate substrates, e.g. two semiconductor dies, incorporated in a single packaged device. These substrates may be mounted on top of each other, e.g. on the top side of a lead frame (e.g. as illustrated in FIG. 16), or the second substrate may be mounted on a top side of a lead frame and the first substrate may be mounted on the bottom side of the lead frame (e.g. as illustrated in FIG. 17).

[0083] The first and the second substrate may be two separate substrates, e.g. two semiconductor dies. The first substrate may be incorporated in a first semiconductor chip, and the second substrate may be incorporated in a second semiconductor chip. The first chip may be mounted on an upper side of a third substrate (e.g. a printed circuit board, or a flexible substrate), and the second chip may be mounted on a bottom side of the third substrate (e.g. said PCB or said flexible substrate), e.g. as illustrated in FIG. 18 and FIG. 19.

[0084] In an embodiment, the substrate comprising the one or more magnetic sensors is a semiconductor substrate, and the one or more magnetic sensors are embedded in the semiconductor substrate, and the semiconductor substrate is incorporated in a packaged device, and the one or more pressure or stress sensors are discrete components surrounding said packaged device.

[0085] The second substrate may be a printed circuit board (PCB). Preferably the packaged device is an integrated semiconductor device (also known as "chip").

[0086] The elastomer may be in physical contact with the packaged device and / or with the pressure / stress sensors, directly or indirectly.

[0087] An example of such embodiment is illustrated in FIG. 5 or FIG. 6. The packaged device and the pressure sensors may be mounted on a second substrate, e.g. a printed circuit board (PCB). The packaged device may have a closed upper surface, or an upper surface with a cavity or an opening (e.g. as illustrated in FIG. 6). The opening may be fully filled with said elastomer, or may be partially filled with said elastomer and partially with an air or a gas.

[0088] In an embodiment, the substrate comprising the one or more magnetic sensors is a first substrate, and the sensor device further comprises a second substrate, and the second substrate is a semiconductor substrate comprising the one or more pressure or stress sensors, and the second substrate is incorporated in a packaged device, and the one or more magnetic sensors are discrete components surrounding said packaged device.

[0089] Preferably the packaged device is an integrated semiconductor device (also known as "chip"), and preferably this chip and the one or more discrete magnetic sensors are mounted on a printed circuit board (PCB). An example of such embodiment may be implemented as a variant of FIG. 5 or FIG. 6, wherein the first substrate is a PCB.

[0090] In an embodiment, the substrate is a printed circuit board; and the one or more magnetic sensors (e.g. Ml, M2, M3) and the one or more pressure or stress sensors (e.g. Pl, P2, P3) are discrete components mounted on the printed circuit board. An example of such embodiment is illustrated in FIG. 7. Preferably the sensors are located on at least three different locations.

[0091] In an embodiment, the elastomer has an overarching or bridge-like shape with a hollow cavity and a supporting rim or supporting legs, and the one or more magnetic sensors (e.g. Ml, M2, M3) are arranged under or inside said cavity, and the one or more pressure or stress sensors (e.g. Pl, P2, P3) are arranged under said supporting rim or supporting legs.

[0092] In an embodiment, the elastomer has an overarching or bridge-like shape with a hollow cavity and a supporting rim or supporting legs, and the one or more magnetic sensors (e.g. Ml, M2, M3) and the one or more pressure or stress sensors (e.g. Pl, P2, P3) are arranged under or inside said cavity. The magnetic material or magnetic particles are preferably situated in the overarching portion. When a force is exerted upon such an elastomer, the magnetic material or particles may experience a relatively large displacement, and thus the sensitivity of the sensor device may be further increased.

[0093] An example with discrete magnetic sensors and discrete pressure sensors is shown in FIG. 7B.

[0094] In a variant of FIG. 7B, the magnetic sensors are integrated in a single device.

[0095] In an embodiment, an object having a height smallerthan the height of the cavity may be placed at a central location inside the cavity, for limiting the displacement of the overarching portion. An additional pressure sensor may be provided under this object.

[0096] In an embodiment (not shown), the sensor device comprises at least one sensor unit, or at least two sensor units, or a plurality of at least three sensor units, each sensor unit comprising a magnetic sensor and a pressure or stress sensor.

[0097] In an embodiment, the substrate comprises at least three magnetic sensors (Ml, M2, M3) arranged on a first virtual circle; and the sensor device comprises at least three pressure or stress sensors (Pl, P2, P3) arranged on a second virtual circle; and the second virtual circle is concentric with the first virtual circle, or an orthogonal projection of the second virtual circle upon the substrate comprising the first virtual circle, is concentric with the first virtual circle.

[0098] In an embodiment, these at least three magnetic sensors and these at least three pressure or stress sensors are mounted to and / or embedded in a single substrate.

[0099] In an embodiment, the first virtual circle has a first radius (Rl) and the second virtual circle has a second radius (R2); and wherein the second radius (R2) is smaller than, substantially equal to, or larger than the first radius.

[0100] The magnetic sensors may be equidistantly angularly spaced on said first circle.

[0101] The pressure or stress sensors may be equidistantly angularly spaced on said second circle.

[0102] In an embodiment, the magnetic material is a permanent magnet, e.g. a single permanent magnet, and the first radius is smaller than or equal to the second radius.

[0103] In an embodiment, the first substrate comprises at least three or at least four magnetic sensors arranged on a virtual circle or a virtual ellipse, and orthogonal projections (in a direction perpendicular to the first substrate) of the one or more pressure or stress sensors onto the substrate are located inside said virtual circle or virtual ellipse.

[0104] An example of such an embodiment is shown in FIG. 15.

[0105] Each magnetic sensor may be capable of measuring at least two or at least three magnetic field components.

[0106] The sensor device may comprise three 2D magnetic pixels, or three 3D magnetic pixels, or four 2D magnetic pixels, or four 3D magnetic pixels, equidistantly spaced apart on said virtual circle.

[0107] Each 2D magnetic pixel may be capable of measuring one magnetic field component (e.g. Bx or By) parallel to the first substrate, and one magnetic field component (e.g. Bz) perpendicular to the first substrate. Each 2D magnetic pixel may comprise: a horizontal Hall element and a vertical Hall element without integrated magnetic concentrator (IMC), or may comprise: a circular IMC disk and two horizontal Hall elements arranged near a periphery of the IMC, angularly spaced apart by 180°.

[0108] Each 3D magnetic pixel may be capable of measuring two magnetic field components (e.g. Bx and By) parallel to the first substrate, and one magnetic field component (e.g. Bz) perpendicular to the first substrate. Each 3D magnetic pixel may comprise: a horizontal Hall element and two vertical Hall elements oriented with their axes of main sensitivity perpendicular to each other, or may comprise: a circular IMC disk and four horizontal Hall elements arranged near a periphery of the IMC, angularly spaced apart by multiples of 90°.

[0109] In an embodiment, this sensor device comprises only one pressure or stress sensor located in the centre of the virtual circle.

[0110] In an embodiment, the processing circuit is configured for determining one or more first force components (e.g. a single force component, e.g. Flz, or a normal force component and a shear force component Fsh, or three force components Fix, Fly, Flz) based on the one or more first signals obtained from the one or more magnetic sensors; and the processing circuit is configured for determining one or more second force component (e.g. a single force component F2z, or three force components F2x, F2y, F2z) based on the one or more second sensor signals obtained from the one or more pressure or stress sensors; and the processing circuit is further configured for determining one or more force components of the force (F) exerted upon said second surface based on the one or more first force components and the one or more second force components.

[0111] In some embodiments, only the force component oriented perpendicular to the sensor substrate is determined. In other embodiments, three orthogonal force components are determined.

[0112] In an embodiment, the sensor device comprises at least two magnetic sensors, and the processing circuit is configured for determining the one or more first force components based on one or more pairwise differences between the first sensor signals obtained from the at least two magnetic sensors.

[0113] In an embodiment, the sensor device comprises four magnetic sensors (e.g. Ml, M2, M3, M4), each capable of measuring three orthogonal magnetic field components (e.g. Ml: Bxl,Byl,Bzl; M2: Bx2,By2,Bz2; M3: Bx3,By3,Bz3; M4: Bx4,By4,Bz4); and the processing circuit is configured for determining at least two magnetic field differences (e.g. dBxdx, dBydx, dBzdx, dBxdy, dBydy, dBzdz) between parallel magnetic field components; and the processing circuit is configured for determining the one or more first force components (e.g. Fix, Fly; Flz) based on said magnetic field differences.

[0114] For example, Fix may be determined as a function of one or more magnetic field differences along the X-axis, e.g. as a function of dBxdx only, or as a function of dBzdx only, or as a function of dBxdx and dBzdx, or as a function of dBxdx, dBydx and dBzdx (e.g. as defined in FIG. 15). For example, Fly may be determined as a function of one or more magnetic field differences along the Y-axis, e.g. as a function of dBydy only, or as a function of dBzdy only, or as a function of dBydy and dBzdy, or as a function of dBxdy, dBydy and dBzdy (e.g. as defined in FIG. 15).

[0115] For example, Flz may be determined as a function of dBzdx and dBzdy, or as a function of dBzdx, dBzdy, dBxdx and dBydy (e.g. as defined in FIG. 15).

[0116] In an embodiment, the sensor device comprises four magnetic sensors (Ml, M2, M3, M4), each capable of measuring at least two (or only two) orthogonal magnetic field components (e.g. Ml: Bxl,Bzl; M2: By2,Bz2; M3: Bx3,Bz3; M4: By4,Bz4); and the processing circuit is configured for determining at least two magnetic field differences (e.g. dBxdx, dBzdx, dBydy, dBzdy); and the processing circuit is further configured for determining the one or more first force components (Fix, Fly, Flz) based on said magnetic field differences.

[0117] An example of such embodiment is a variant of FIG. 15 where H2, H4, H10, H12, H13, H15, H5, H7 are omitted.

[0118] For example, Fix may be determined as a function of one or more magnetic field differences along the X-axis, e.g. as a function of dBxdx only, or as a function of dBzdx only, or as a function of dBxdx and dBzdx (e.g. as defined in FIG. 15).

[0119] For example, Fly may be determined as a function of one or more magnetic field differences along the Y-axis, e.g. as a function of dBydy only, or as a function of dBzdy only, or as a function of dBydy and dBzdy (e.g. as defined in FIG. 15).

[0120] For example, Flz may be determined as a function of dBzdx and dBzdy, or as a function of dBzdx, dBzdy, dBxdx and dBydy (e.g. as defined in FIG. 15).

[0121] In an embodiment, the processing circuit is configured for determining the value or values of the one or more components (e.g. Fx, Fy, Fz) of the force (F) exerted upon said second surface as the one or more first force component (e.g. Fix, Fly, Flz) if this first force component value is smaller than a first threshold value, or as the one or more second force component (e.g. F2x, F2y, F2z) otherwise.

[0122] In an embodiment, the processing circuit is configured for determining a first amplitude of a first vector corresponding with the one or more first force components (Fix, Fly, Flz), and for testing if this first amplitude is smaller than a first predefined threshold value; and if an outcome of this test is true, (meaning that the first vector is relatively small, hence no clipping occurred) to determine the one or more force components of the force to be measured based solely on the one or more first force components, and if an outcome of this test is false, (meaning that the first vector is relatively large) to determine the one or more force components of the force to be measured based solely on the one or more second force components.

[0123] In embodiments were a single force component is measured, e.g. Fz, this means that Fz is either set to Flz (if this value is smaller than a predefined threshold value), or to F2z otherwise. In embodiments where three force components are measured, this means that the values of (Fx, Fy, Fz) are either set equal to (Fix, Fly, Flz), if the amplitude of this vector is smaller than a predefined threshold value, or are set equal to (F2x, F2y, F2z) otherwise.

[0124] In a variant, the processing circuit is configured for determine a single first force component (e.g. Flz) and a single second force component (e.g. F2z), and for testing if the second force component is larger than a predefined threshold value, and if an outcome of this test is true, to determine the force to be measured as said second force component (e.g. F2z), and if an outcome of the test is false, to determine the force to be measured as said first force component (e.g. Flz).

[0125] In a variant, the processing circuit is configured for determining a largest value from the second set of three force components (F2x, F2y, F2z), and for testing if this largest value is larger than a predefined threshold value, and if an outcome of this test is true, to determine the one or more force components (Fx, Fy, Fz) of the force (F) as one or more components from the second set of force components (F2x, F2y, F2z), and to determine the one or more force components (Fx, Fy, Fz) of the force (F) as one or more component from the first set of force components (Fix, Fly, Flz) otherwise.

[0126] In an embodiment, the processing circuit is configured for determining the value or values of the one or more force components (Fx, Fy, Fz) of the force (F) exerted upon said second surface as a combination (e.g. linear combination, average, weighted average) of the component value from the first force component (Flz) or from the first set of components (Fix, Fly, Flz) (on the one hand), and the component value from the second force component (F2z) or a corresponding component from the second set of components (F2x, F2y, F2z) (on the other hand).

[0127] In this embodiment, the value for (Fx, Fy, Fz) may be calculated in accordance with one or more of the following formulas: Fx=wll*Flx+wl2*F2x; Fy=w21*Fly+w22*F2y; Fz=w31*Flz+w32*F2z, where wll to w32 are predefined weighting factors, which may be determined during a calibration procedure. These weighting factors may depend on the shape and size of the elastomer and on the relative position of the sensor elements.

[0128] In an embodiment, the sensor device is configured for determining and outputting three orthogonal force components (e.g. Fx, Fy, Fz) comprising a normal force component (e.g. Fz) and two shear force components (e.g. Fx, Fy).

[0129] In an embodiment, the sensor device is configured for determining and outputting two shear force components (e.g. Fx, Fy).

[0130] In an embodiment, the sensor device is configured for determining and outputting a normal force component (e.g. Fz) and a single shear force component (e.g. Fsh).

[0131] In an embodiment, the sensor device is configured for determining and outputting a single shear force component (e.g. Fsh).

[0132] The single shear force component Fsh may be calculated in accordance with the formula: Fsh = sqrt[sqr(Fx) + sqr(Fy)], where sqrt() is the square-root function, and sqr() is the square function. In an embodiment, the single shear force component (e.g. Fsh) or the two (e.g. orthogonal) shear force components (e.g. Fx, Fy) are derived from (or solely derived from) signals obtained from the one or more magnetic sensor, optionally taking into account a measured temperature value.

[0133] In the latter case, the sensor device may further comprise a temperature sensor for measuring a temperature of the first or the second substrate, as an estimate of the temperature of the elastomer.

[0134] In an embodiment, the normal force component is determined based on signals obtained from both the one or more magnetic sensor(s) and from the one or more pressure of stress sensor(s), optionally taking into account a measured temperature value.

[0135] In an embodiment, the normal force component (e.g. Fn) is determined as a weighted average between a first force component (Flz) and a second force component (F2z), using predefined weighting factors, or using temperature dependent weighting factors.

[0136] For example in accordance with the formula: Fn=wl*Flz + w2*F2z, where wl and w2 are the weighting factors, which may be predefined constants, or functions of temperature, which may be stored in any suitable way in a non-volatile memory, e.g. in the form of one or more look-up table, or as coefficients of a polynomial expression.

[0137] In an embodiment the normal force component (e.g. Fn) is determined as a weighted average of a first normal force component Flz derived from magnetic field difference signals, and a second normal force component F2z derived from one or more pressure signals, wherein the weighting factors are optionally temperature dependent.

[0138] In an embodiment, the processing circuit is configured for performing a consistency test between the one or more first sensor signals obtained from the one or more magnetic sensors and the one or more second sensor signals obtained from the one or more pressure / stress sensors, or between the one or more first force components (e.g. Fix, Fly, Flz) and the one or more second force components (e.g. F2x, F2y, F2z); and if an inconsistency is detected, to determine the one or more force components (Fx,Fy,Fz) of the force to be measured based solely on the one or more second force components (e.g. F2x, F2y, F2z).

[0139] In an embodiment, the sensor device may optionally also provide an error signal based on an outcome of this consistency test. This error signal may be output by the sensor device, or may be transmitted (e.g. to another processor, e.g. to an ECU).

[0140] A result of the consistency test may be provided as an error signal. For example, if the sensor device is implemented in a chip or a module or a printed circuit board, said chip or module or printed circuit board may provide a first output signal indicative of the measured force components, and may provide a second output signal indicative of an error.

[0141] In an embodiment, such a consistency test may comprise: 1) testing if each force component (Fix, Fly, Flz) of the first set of force components is smaller than a respective value of a first set of predefined threshold values (Tlx, Tly, Tlz); and if an outcome of this test is true, (meaning that all values are relatively small, and that no clipping or saturation occurs) testing a consistency between Tlx and T2x, and testing a consistency between Tly and T2y, and testing a consistency between Tlz and T2z, for example by testing if these values deviate less than a predefined absolute value, and / or by testing if these values deviate less than a predefined percentage, e.g. by testing if a ratio of Tlx / T2x is a value in a predefined range such as e.g. in the range from 80% to 120%, or in the range from 90% to 110%, or in the range from 95% to 105%. If at least one of the component values (e.g. Fix) is larger that its respective first threshold value (e.g. Tlx) the other pairwise consistency tests, e.g. between F2y and T2y, and / or F2z and T2z may be skipped.

[0142] In an embodiment, the processing circuit is configured for determining a presence of a magnetic disturbance field (e.g. by measuring a magnetic field that is larger than the field generated by the magnetic material, e.g. by the magnet in the elastomer); and if it is detected that a magnetic disturbance field of at least a predefined magnitude is present, to determine the one or more, e.g. three force components (Fx, Fy, Fz) of the force (F) based solely on the one or more second force components (F2x, F2y, F2z).

[0143] In an embodiment, the processing circuit is further configured for detecting the presence of a magnetic disturbance field, for example by determining a magnitude of the magnetic field measured by any of the magnetic sensors, and to determine that a magnetic disturbance field is present if the value of the measured magnitude is larger than a predefined maximum value.

[0144] According to a second aspect, the present invention also provides a robotic gripper comprising two or more movable elements (e.g. robotic fingers), each movable element comprising at least one sensor device according to the first aspect.

[0145] According to a third aspect, the present invention also provides a method of determining one or more (e.g. only one, only two or three) force component (e.g. Fx, Fy, Fz) of a force (F) using a sensor device according to the first aspect, the method comprising the steps of: a) receiving one or more first sensor signals (e.g. ml, m2, m3) from the one or more magnetic sensors (e.g. Ml, M2, M3), and determining one or more first force component (e.g. Flz; Fix, Fly, Flz) based on this one or more first signal (e.g. ml, m2, m3); b) receiving one or more second sensor signals (e.g. si, s2, s3) from the one or more pressure or stress sensors (e.g. Pl, P2, P3), and determining one or more second force components (e.g. F2z; F2x, F2y, F2z) based on this one or more second sensor signal (e.g. si, s2, s3); c) determining one or more force components (e.g. Fz; Fx, Fy, Fz) of the force to be measured based on said one or more first force components (e.g. Fix, Fly, Flz) and based on said one or more second force components (e.g. F2x, F2y, F2z).

[0146] In an embodiment, step a) comprises: determining the first force component (e.g. Flz) or the first set of force components (e.g. Fix, Fly, Flz) based on pairwise differences between the first set of signals (e.g. ml, m2, m3). In an embodiment, step a) comprises: determining a first force component (e.g. Flz) oriented in a direction perpendicular to the substrate; and step b) comprises: determining a second force component (e.g. F2z) oriented in said direction perpendicular to the substrate; and step c) comprises: determining the force to be measured as the first force component (e.g. Flz) if its value is smaller than a first predefined threshold value.

[0147] In an embodiment, step a) comprises: determining a first force component (e.g. Flz) oriented in a direction perpendicular to the substrate; and step b) comprises: determining a second force component (e.g. F2z) oriented in said direction perpendicular to the substrate; and step c) comprises: determining the force to be measured as the second force component (e.g. F2z) if this value is larger than a second predefined threshold value.

[0148] In an embodiment, step a) comprises: determining a first set of three force components (e.g. Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (e.g. F2x, F2y, F2z); and step c) comprises: determining the force to be measured as the first set of force components if each of the values of the first set of force components is smaller than a first predefined threshold value, and determining the force to be measured as the second set of force components otherwise.

[0149] In an embodiment, step a) comprises: determining a first set of three force components (e.g. Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (e.g. F2x, F2y, F2z); and step c) comprises: determining the force to be measured as the second set of force components if at least one of the values of the second set of force components is larger than a second predefined threshold value, and determining the force to be measured as the second set of force components otherwise.

[0150] In an embodiment, step a) comprises: determining a first set of three force components (e.g. Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (e.g. F2x, F2y, F2z); and step c) comprises: determining each component of the force to be measured as the corresponding component from the first set of force components if its value is smaller than a first predefined threshold value, and as the corresponding component from the second set of force components otherwise.

[0151] In an embodiment, the method further comprises a step of performing a consistency check between the first and the second set of sensor signals, and / or between the first (e.g. Flz) and second (e.g. F2z) force component, or between the first set (e.g. Fix, Fly, Flz) and second set (e.g. F2x, F2y, F2z) of force components, and providing a result of the consistency check (e.g. an error signal).

[0152] In an embodiment, the method further comprises a step of measuring or estimating a temperature of the elastomer; and step a) comprises determining said first component or said first set of force components taking into account said temperature, e.g. taking into account a temperature dependent flexibility of the elastomer. Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

[0153] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

[0154] Brief description of the drawings

[0155] FIG. 1A is a cross-sectional view of an illustrative example of a force sensor device according to an embodiment of the present invention. The device comprises an elastomer, magnetic material in the form of a magnet, one or more, e.g. at least three magnetic sensors and one or more, e.g. at least three pressure / stress sensors. In the example of FIG. 1A, the magnetic sensor(s) and the pressure / stress sensor(s) are integrated in a single semiconductor substrate.

[0156] FIG. IB shows an illustrative example of a semiconductor substrate as may be used in FIG. 1A in top view, showing a possible arrangement of three magnetic sensors on an inner circle, and three pressure / stress sensors on an outer circle.

[0157] FIG. 1A and FIG. IB may be jointly referred to as FIG. 1.

[0158] FIG. 2 to FIG. 6 are cross-sectional views of other illustrative examples of force sensor device according to embodiments of the present invention.

[0159] FIG. 7A shows a top view, and FIG. 7B shows a cross-sectional view of another illustrative example of a force sensor device according to an embodiment of the present invention.

[0160] FIG. 7A and FIG. 7B may be jointly referred to as FIG. 7.

[0161] FIG. 8 shows a graph with a first illustrative curve (in arbitrary units) showing one component of a first set of force components (Fix, Fly, Flz) derivable from the signals obtained from the magnetic sensors, and with a second illustrative curve showing one component of a second set of force components (F2x, F2y, F2z) derivable from the signals obtained from the pressure / stress sensors.

[0162] FIG. 9 show the graph of FIG. 8 with an indication of certain threshold values and regions.

[0163] FIG. 10A, FIG. 10B and FIG. IOC shows flow-charts of a method of measuring a force according to an embodiment of the present invention, e.g. using a sensor device as illustrated in any of FIG. 1 to FIG. 7B, or using a sensor device as illustrated in FIG. 14 to FIG. 19.

[0164] FIG. 10A, FIG. 10B and FIG. IOC may be jointly referred to as FIG. 10.

[0165] FIG. 11 shows an illustrative example of a high-level block diagram of a sensor device comprising one or more magnetic sensor and one or more pressure / stress sensors (e.g. arranged as illustrated in FIG. 1 to FIG. 7B), and a processing circuit, and optionally a temperature sensor, and optionally a nonvolatile memory.

[0166] FIG. 12 shows another illustrative example of a high-level block diagram of a sensor device comprising a first processing circuit connected to one or more magnetic sensors, and comprising a second processor circuit connected to the first processing circuit and to one or more pressure / stress sensors.

[0167] FIG. 13 shows an illustrative example of a force sensor device or a force sensor system comprising a first sensor device comprising one or more magnetic sensor(s), and a second sensor device comprising one or more pressure / stress sensors, and a combiner circuit connected to the first and to the second sensor device.

[0168] FIG. 14 shows a substrate (e.g. a semiconductor substrate or a PCB) comprising four magnetic sensors and one or more pressure / stress sensors, and a elastomer comprising a magnet on top of the substrate, as may be used in embodiments of the present invention.

[0169] FIG. 15 shows a semiconductor substrate comprising four magnetic sensors in the form of four 3D magnetic pixels, and one pressure / stress sensor, as may be used in embodiments of the present invention.

[0170] FIG. 16 to FIG. 19 are cross-sectional views of other illustrative examples of force sensor device according to embodiments of the present invention.

[0171] FIG. 20 shows measurement results obtained from an experiment wherein a normal force is applied and released, showing strong hysteresis.

[0172] FIG. 21A shows measurement results obtained from an experiment wherein a normal force is repeatedly applied and released, showing strong hysteresis.

[0173] FIG. 21B shows a normal force component determined as a combination of the first and second force component Flz and F2z, showing a highly linear behaviour with a strongly reduced hysteresis.

[0174] FIG. 21A and FIG. 21B may be jointly referred to as FIG. 21.

[0175] FIG. 22 is a data flow diagram illustrating how the signals from the one or more magnetic sensors and from the one or more pressure / stress sensor can be used to calculate one or more force components, e.g. a normal force component Fn and / or shear force components Fx, Fy and / or a shear force Fsh.

[0176] The drawings are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Any reference signs in the claims shall not be construed as limiting the scope. In the different drawings, the same reference signs refer to the same or analogous elements.

[0177] Detailed description of illustrative embodiments

[0178] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims.

[0179] The terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0180] The terms top, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

[0181] It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

[0182] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

[0183] Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

[0184] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0185] Furthermore, the terms "approximately", "substantially", or "about" indicate a range of tolerance which the skilled person in the field in question considers to be normal. In particular, the afore- mentioned terms are to be understood as encompassing a tolerance range of the referred quantity of up to a maximum of ±20 %, preferably up to a maximum of ±10 %, unless explicitly mentioned otherwise, or unless clear from the context otherwise.

[0186] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0187] In this document, the expression "pressure sensor or stress sensor" or "pressure or stress sensor" or "pressure / stress sensor" mean the same.

[0188] In this document, the term "magnetic sensor element" may refer to a single vertical Hall element or a single horizontal Hall element or a single magneto-resistive element (e.g. an AMR element, a GMR element, a TRM element or an XMR element).

[0189] In this document, the term "magnetic sensor" or "magnetic sensor structure" can refer to a group of components or a sub-circuit or a structure capable of measuring a magnetic quantity, such as for example a group of at least two magnetic sensor elements, or a Wheatstone-bridge containing four MR elements.

[0190] In certain embodiments of the present invention, the term "magnetic sensor" or "magnetic sensor structure" may refer to an arrangement comprising one or more integrated magnetic concentrators (IMC), also known as integrated magnetic flux concentrators, and two or four or eight horizontal Hall elements arranged near the periphery of the IMC.

[0191] In this document, the expression "in-plane component of a vector" and "orthogonal projection of the vector in the sensor plane" mean the same. If the sensor device is or comprises a substrate (e.g. a semiconductor substrate or a printed circuit board), this also means " components parallel to that substrate".

[0192] In this document, the expression "out-of-plane component of a vector" and "Z component of the vector" and " orthogonal projection of the vector on an axis perpendicular to the sensor plane" mean the same.

[0193] Embodiments of the present invention are typically described using an orthogonal coordinate system which is fixed to the sensor device, and having three axes X, Y, Z, where the X and Y axis are parallel to the substrate, and the Z-axis is perpendicular to the substrate. In the context of the present invention, "the substrate" typically refers to the first substrate comprising a plurality of magnetic sensors, unless clear from the context that something else is meant.

[0194] In this document, the expression "spatial derivative" or "derivative" or "spatial gradient" or "gradient" are used as synonyms. In the context of the present invention, a gradient is typically determined as a difference between two values measured at two different locations spaced apart by a predefined distance. In theory the gradient is calculated as the difference between two values divided by the distance, e.g. "dx" between the sensor locations, but in practice the division by "dx" is often omitted, because the measured signals need to be scaled anyway.

[0195] In this document, horizontal Hall plates are typically referred to by Hl, H2, etc., signals from these horizontal Hall plates are typically referred to by hl, h2, etc.; vertical Hall plates are typically referred to by VI, V2, etc., and signals from these vertical Hall plates are typically referred to by vl, v2, etc.; magnetic sensors are typically referred to by Ml, M2, etc., signals from these magnetic sensors are typically referred to by ml, m2, etc.; pressure or stress sensors are typically referred to by Pl, P2, etc., and signals from these sensors are typically referred to by pl, p2, etc.

[0196] The present invention relates in general to methods and devices for measuring a force, e.g. to force sensors or tactile sensors, and more specifically to force sensors or tactile sensors as may be used in industrial or robotic applications for gripping and lifting objects. They may be mounted to robotic fingers and be used for clamping objects between such fingers.

[0197] The present invention will be mainly explained referring to a sensor device comprising at least three magnetic sensors and at least one pressure / stress sensor, and being configured for determining two force components (e.g. a normal force component Fn, and a shear force component Fsh) or three force components (e.g. Fx, Fy, Fz), for ease of the description. But the present invention is not limited thereto, and also works for determining at least one force component, e.g. a single force component Fz using a sensor device having less than three magnetic sensors and / or less than three pressure or stress sensors.

[0198] Referring to the Figures.

[0199] FIG. 1A is a cross-sectional view of an illustrative example of a force sensor device or tactile sensor device 100. The force sensor device 100 of FIG. 1 comprises an integrated circuit (or "chip") 107 having a plastic moulded package 102, and on top of that package an elastomer 110. The device 100 further comprises a permanent magnet 104 embedded in the elastomer 110. The magnet 104 generates a magnetic field. The integrated circuit 107 of FIG. 1A comprises a semiconductor substrate (e.g. a CMOS substrate) comprising at least three magnetic sensors (only one is visible in FIG. 1A), and at least three pressure or stress sensors (only one is visible in FIG. 1A).

[0200] FIG. IB shows an example of a semiconductor substrate 101 comprising three magnetic sensors Ml, M2, M3 (schematically indicated by a square for illustrative purposes) and three pressure sensors Pl, P2, P3 (also schematically indicated by a square for illustrative purposes) embedded in the semiconductor substrate 101, and arranged in a particular manner, but the present invention is not limited hereto. In the example of FIG. IB, the three magnetic sensors Ml, M2, M3 (e.g. horizontal Hall elements) are located on a first virtual circle having a first radius Rl, and are angularly spaced by multiples of 120°; and the three stress sensors Pl, P2, P3 (e.g. piezo-resistive, piezo-capacitive, piezoelectric or barometric sensing elements) are located on a second virtual circle having a second radius R2, and are also angularly spaced by multiples of 120°. In the example of FIG. IB, the second virtual circle is concentric with the first virtual circle, and the second radius R2 is larger than the first radius Rl, the present invention not being limited thereto.

[0201] Referring to FIG. 1A, the elastomer 110 is in mechanical contact with the plastic moulded package 102 at a first surface area 111. When no external force is exerted upon a second surface area 112 of the elastomer, the magnet 104 is in its "rest position" or "default position", and the magnetic sensors measure a first set of signals, and the pressure sensors measure a second set of signals, corresponding to this "default magnet position" corresponding to "no external force applied".

[0202] When an external force F is exerted upon the second surface area 112 of the elastomer 110, (in the example of FIG. 1A the second surface area 112 is located at the top) the elastomer 110 will elastically deform, and the magnet 104 will slightly move (e.g. in the example shown in FIG. 1A, the magnet will move slightly downwards and to the right). The magnetic sensors will measure a different magnetic field, and will provide a different first set of signals corresponding to the new position of the magnet, and thus corresponding to the external force that is applied. Techniques for converting such magnetic signals into three magnetic field components (Fix, Fly, Flz) are known in the art, and may involve for example a trained artificial neural network (ANN), but the present invention is not limited hereto, and other processing circuits or processing techniques may also be used, for example as described in W02023036900(A1), incorporated herein by reference in its entirety, in particular FIG. 22(a) and FIG. 22(b) thereof, and the corresponding algorithms.

[0203] The force F applied to the elastomer 110, or a portion thereof, will also be sensed by the pressure or stress sensors Pl, P2, P3, which will provide another set of second signals, corresponding to the external force that is applied. For example, when a normal force (i.e. a force oriented in the negative Z-direction, perpendicular to the semiconductor substrate 101) is applied, the three pressure sensors will sense a same pressure value. As another example, when the force has a component in the negative Z-direction and in the positive X-direction, the pressure sensors Pl and P3 will sense a same value, but the sensor P2 will sense a higher value. It is known in the art how the second set of signals can be converted into a set of orthogonal force components (F2x, F2y, F2z). Since such algorithm is known, and is not the main focus of the present invention, it does not have to be explained in more detail here. It suffices to say that in certain embodiments, the force component values (F2x, F2y, F2z) may be calculated using a matrix multiplication between a matrix comprising predefined coefficients, which may be determined during a calibration procedure, and a matrix comprising the sensor signals. From the above, it can be understood that one or more force components, e.g. a first set of three orthogonal force components (Fix, Fly, Flz) can be derived from the signals obtained from the magnetic sensors Ml, M2, M3, and one or more force components, e.g. a second set of three orthogonal force components (F2x, F2y, F2z) can be derived from the signals obtained from the pressure or stress sensors.

[0204] The force sensor device 100 of FIG. 1A and FIG. IB may further comprise one or more processing circuits for determining one or more, e.g. three force component values (Fx, Fy, Fz) of the force being applied to the elastomer 110, based on the first set and the second set of three orthogonal force component values, as will be explained further in FIG. 8 to FIG. 10.

[0205] In the example of FIG. 1A, the elastomer 110 has a dome-shaped upper surface, but that is not absolutely required, and other geometries can also be used, e.g. a planar surface.

[0206] In the example of FIG. 1A, the integrated semiconductor device 107 has a lead frame with leads or pins 103 extending sideways from the package 102, but that is not required, and other packages can also be used.

[0207] In another or a further variant, the sensor device may comprise more than three magnetic sensor elements, e.g. four magnetic sensors, and / or more than three pressure or stress sensors, or less than three pressure / stress sensors, e.g. only one pressure / stress sensor.

[0208] In the example shown in FIG. 1A, the magnet 104 is a solid permanent magnet having for example a cylindrical shape with a diameter D and a height H, but that is not absolutely required, and solid magnets with another shape can also be used. In other variants (not shown), instead of a solid object or in addition to the solid object, the sensor device 100 may comprise a magnetic powder or magnetic particles which are distributed inside the elastomer 110.

[0209] In some embodiments, some or all of the "magnetic sensors" or "magnetic sensor units" may be one-dimensional (ID) magnetic pixels, e.g. horizontal Hall-elements, or vertical Hall-elements, each configured for measuring a single magnetic field component at the respective location, e.g. Bz in case of horizontal Hall elements.

[0210] Alternatively or additionally, some or all of the magnetic sensors or "magnetic sensor units" may be two-dimensional (2D) magnetic pixels. Each such magnetic sensor unit may e.g. comprise two vertical Hall elements, e.g. one for measuring a Bx-component and one for measuring a By-component. Or each such magnetic sensor unit may e.g. comprise an integrated magnetic concentrator (IMC) and two Horizontal Hall elements spaced apart by 180°.

[0211] Alternatively or additionally, some or all of the magnetic sensors or "magnetic sensor units" are three-dimensional (3D) magnetic pixels. Each such magnetic sensor unit may e.g. comprise a horizontal Hall element and two or four vertical Hall elements located adjacent or around the horizontal Hall element. Or each such magnetic sensor unit may e.g. comprise a circular IMC and four horizontal Hall elements arranged near a periphery of the IMC, angularly spaced apart by multiples of 90°. In certain embodiments of the present invention, the first force component (e.g. Flz) or the first set of force components (Fix, Fly, Flz) is not merely derived from magnetic sensor signals as can be provided by horizontal Hall elements or vertical Hall elements or magneto-resistive (MR)-elements, but are derived from differences between parallel field components or from magnetic field gradient signals. This offers the advantage that the first force component or the first set of force components thus determined have an improved robustness against an external disturbance field.

[0212] The permanent magnet 104 may be an axially magnetized two-pole magnet, e.g. having a cylindrical shape or disk shape. This cylinder may have a diameter D, and a height H. A ratio D / Rl may be a value in the range from 0.50 to 2.0, but the present invention is not limited thereto.

[0213] In a variant of FIG. IB (not shown), the radius R1 of the circle where the magnetic sensors are located is larger than the radius R2 of the circle where the one or more pressure sensors are located.

[0214] In a variant of FIG. 1A and FIG. IB, not shown, the substrate 101 comprises three or four magnetic sensors (e.g. 2D magnetic pixels or 3D magnetic pixels), located on a virtual circle with radius Rl, and comprises one or more pressure sensors or stress sensors located inside said virtual circle, but not necessarily located on a second circle, e.g. only one pressure sensor or stress sensor located substantially in the centre of the virtual circle.

[0215] FIG. 2 is a cross-sectional view of an illustrative example of another force sensor device or tactile sensor device 200, which can be seen as a variant of the force sensor device 100 of FIG. 1. Apart from the shape of the upper surface 212 of the elastomer 210, the main difference between the sensor device 200 of FIG. 2 and the sensor device 100 of FIG. 1 is that the moulded package 202 of the integrated sensor device 207 (before the elastomer 210 is applied) has a cavity or a recess 205 for receiving a bottom portion of the elastomer 210.

[0216] In this way, the thickness of the upper layer of the mould compound 202 can be reduced, and the risk of the elastomer 210 being detached from the moulded package due to shear forces can be reduced. In addition, the magnet 204 can also be positioned closer to the substrate 201, thus the magnetic field measured by the magnetic sensors Ml, M2, M3 can be stronger, which improves the signal-to-noise ratio (SNR), and thus the accuracy.

[0217] Everything else described above for FIG. 1A and FIG. IB and its variants, is also applicable here, mutatis mutandis. For example, the semiconductor substrate 201 may comprise more than three magnetic sensors, and / or may comprise more than three or less than three pressure / stress sensors, and / or the sensors may be arranged in the same way as illustrated in FIG. IB, or differently (e.g. as described in variants of FIG. IB).

[0218] In a variant (not shown) of FIG. 2, a cavity would be formed between the upper surface of the semiconductor substrate 201 and the elastomer 210, and this cavity would be filled with air or with a gas, and this air or gas would transfer a portion of the force exerted upon the elastomer. Thus, the elastomer 210 does not have to be in direct physical contact with the pressure or stress sensors, but it may.

[0219] In a variant of FIG. 2 (not shown), the elastomer 210 has a dome shaped upper surface.

[0220] FIG. 3 shows a cross-section of another illustrative sensor device 300, which can be seen as a variant of the sensor device 100 of FIG. 1, or as a further variant of the sensor device 200 of FIG. 2, wherein the moulded package 302 of the semiconductor device 307 has an opening 308 that exposes an upper surface of the semiconductor substrate 301, before the elastomer 310 is applied for allowing a direct physical contact between the elastomer 310 and the upper surface of the substrate, without a moulding compound in between. In this way, the sensitivity of the pressure / stress sensors can be further increased. Everything else described above for FIG. 2 and its variants is also applicable here, mutatis mutandis.

[0221] By comparing FIG. 2 and FIG. 3, the skilled reader having the benefit of the present disclosure once it is published, will understand that, for a given elastomer, the sensitivity of the force measurement using the magnetic sensors can be increased by mounting the magnet 204 closer to the substrate 201, and that the sensitivity of the force measurements using the pressure / stress sensors can be increased by reducing the thickness Tc of the compound layer between the substrate 201 and the elastomer 210.

[0222] FIG. 3 also shows another aspect, namely that instead of using three pressure sensors arranged as illustrated in FIG. IB, the semiconductor device may use stress sensors arranged in close vicinity of the magnetic sensors. Depending on the implementation, each stress sensor may be situated adjacent a magnetic sensor, or may surround the magnetic sensor (e.g. a horizontal Hall plate). This aspect is unrelated to the presence of an opening 308, and can also be used in the device of FIG. 1A or the device of FIG. 2, but no separate drawing is provided.

[0223] FIG. 4 shows a cross-section of a further variant of FIG. 3, wherein an orthogonal projection of the elastomer 410 on a plane containing the substrate 401 is smaller than the size of the substrate 401, and thus is also smaller than an outline of the moulded package 402. In contrast, in the devices illustrated in FIG. 1A, FIG. 2 and FIG. 3 an orthogonal projection of the elastomer on a plane containing the semiconductor substrate is larger than the semiconductor substrate, but smaller than the outline of the moulded package. But the present invention is not limited to either of the above, and a projection or a footprint of the elastomer may also be larger than the outline of the moulded package, as will be described further.

[0224] FIG. 5 shows a cross-section of another illustrative sensor device 500, which can be seen as another variant of the sensor device 100 of FIG. 1. The main differences between the device 500 of FIG. 5 and the device 100 of FIG. 1 are: (i) that the at least three pressure / stress sensors Pl, P2, P3 are not integrated in the semiconductor substrate 501 in which the magnetic sensors Ml, M2, M3 are integrated. In the embodiment shown in FIG. 5, the pressure / stress sensors Pl, P2, etc. are discrete sensors situated outside of the packaged device 507, mounted on a printed circuit board 506. As can be seen, the packaged sensor device 507 may also be mounted on this printed circuit board 506;

[0225] (ii) that the elastomer 510 is not only situated above the substrate 501 containing the magnetic sensors, but is also situated above the pressure sensors Pl, P2, etc. Also here, the elastomer 510 has a second contact area 512 for receiving the external force F that is applied, and has one or more first contact area(s) 511, 511' for guiding or transferring this force, or portions thereof to the pressure / stress sensors Pl, P2, etc.

[0226] In the embodiment shown in FIG. 5, the upper surface of the elastomer 510 is substantially planar, but that is not absolutely required for the invention to work, and preferably the upper surface has a dome shape (not shown).

[0227] In the example shown in FIG. 5, the semiconductor substrate 501 comprises three magnetic sensors (only Ml is shown), which may be arranged on a first virtual circle and may be angularly spaced apart by multiples of 120°, but another arrangement of at least three magnetic sensor elements can also be used, e.g. four magnetic sensors angularly spaced apart by 90°, each being a ID magnetic pixel or a 2D magnetic pixel or a 3D magnetic pixel.

[0228] In the example shown in FIG. 5, the printed circuit board 506 comprises three pressure / stress sensors (only Pl, P2 are shown), which may be arranged on a second virtual circle and may be angularly spaced apart by multiples of 120°, but another arrangement of at least three pressure / stress sensors can also be used, or an arrangement with fewer than three pressure / stress sensors.

[0229] In a variant (not shown) of FIG. 5, the moulded package of the integrated semiconductor device 507 has a cavity (not shown), e.g. similar to the one illustrated in FIG. 2. Optionally the semiconductor substrate 501 may further comprise a plurality of stress sensors integrated in the semiconductor substrate.

[0230] FIG. 6 shows a cross-section of another illustrative sensor device 600, which can be seen as a further variant of the sensor device 500 of FIG. 5, the main difference being that the moulded package of the integrated semiconductor device 607 has an opening, e.g. similar to the sensor device 300 of FIG. 3. Everything else described for FIG. 5 and its variants is also applicable here. FIG. 6 also shows one or more optional stress sensors P4 integrated in the semiconductor substrate 601. If present, they may provide further pressure (or stress) signals.

[0231] FIG. 7A shows a top view, and FIG. 7B shows a cross-sectional view of another illustrative example of a force sensor device 700. 1

[0232] This sensor device 700 comprises a substrate 706, for example a printed circuit board (PCB).

[0233] The PCB 706 may have a circular shape, or a square shape or a rectangular shape, but that is not absolutely required for the invention to work.

[0234] The sensor device 700 further comprises a plurality of magnetic sensors Ml to M4 and a plurality of pressure / stress sensors Pl to P3, mounted on said PCB 706. In the example shown, the PCB 706 comprises four magnetic sensors (or magnetic sensor units) Ml to M4 arranged on a first virtual circle with a first radius and angularly spaced apart by multiples of 90°; and comprises three pressure sensors Pl to P3 arranged on a second virtual circle with a second radius and angularly spaced apart by multiples of 120°, but another number or arrangement of magnetic sensors and pressure sensors can also be used.

[0235] The sensor device 700 further comprises an elastomer 710 having a cavity 713. The cavity may be filled with air or a gas (e.g. Nitrogen gas). The magnetic sensors may be located inside said cavity 713. The pressure / stress sensors may also be located inside said cavity. When a mechanical force is exerted upon the second surface area of the elastomer, the elastomer may transfer this force to the pressure or stress sensors (e.g. if the elastomer is in mechanical contact with these sensors), or may cause an increase of the pressure of the air or gas, which in turn can be sensed by the pressure or stress sensors. In the example of FIG. 7B, the pressure or stress sensors are in direct contact with the elastomer via one or more first contact areas 711, 711'. The elastomer has a second contact area 712 for receiving the force to be measured.

[0236] The sensor device 700 further comprises magnetic material, e.g. a permanent magnet 704, or magnetic powder or magnetic particles, located in the elastomer 710, such that the magnetic material will be displaced when an external force F is exerted upon the second contact surface 712.

[0237] As can be appreciated from FIG. 7B, when a downward oriented force F is exerted upon the second surface 712 of the elastomer 710, the magnet 704 will be moved in the negative Z-direction, but thanks to the cavity 713, the displacement will be larger than would be the case without the cavity 713. Thus, the cavity 713 can help to increase the sensitivity of the measurement done by the magnetic sensors. For relatively small forces, the displacement behaves substantially linearly with the magnitude of the force, but above a certain threshold, i.e. for relatively strong forces, the relationship between the displacement and the amplitude of the force may become highly non-linear, and may even clip to a maximum displacement. From the above, it can be understood that the relationship between the magnitude of the force and the displacement of the magnetic material, e.g. of the magnet 704 depends on the orientation of the applied force.

[0238] In some embodiments only a single force component is to be measured, namely a force component Fz oriented in a direction perpendicular to the substrate 706. In other embodiments three force components (Fx, Fy, Fz) are to be measured. As explained above, a first value of this one or more force component(s) can be calculated based on the signals obtained from the magnetic sensors, and a second value of this one or more force component(s) can be calculated based on the signals obtained from the pressure / stress sensors. A final value of the force to be determined can then be determined based on this first and second force component, or based on this first set and second set of force component values, as will be explained further.

[0239] In a variant (not shown) of FIG. 7A and FIG. 7B, the pressure or stress sensors Pl to P3 are also located inside said cavity 713.

[0240] FIG. 8 shows a graph with an illustrative example of signals obtainable from the magnetic sensors and signals obtainable from the pressure / force sensors, as a function of the applied force oriented in a particular direction. Only one magnetic signal and only one pressure signal is shown, but the reader will understand that there may be as many signals as there are sensors or sensor units.

[0241] It is noted that the curves shown in FIG. 8 are only intended for illustrative purposes, and that the exact curves for a particular device can deviate from the curves shown in FIG. 8, but the following discussion remains valid. The inventors made the following observations: i) for relatively small forces, the signals obtained from the magnetic sensors are typically more accurate (e.g. in terms of signal-over-noise, SNR) than the signals obtained from the pressure / stress sensors; hence, for relatively small forces, the accuracy of the one or more first force component(s) is better than the accuracy of the one or more second force component(s); ii) for relatively high forces, the signals obtained from the magnetic sensors typically have a strong non-linearity or may even clip or saturate, whereas the signals obtained from the pressure / stress sensors continue to behave in a highly linear manner over a larger measurement range; hence, for relatively large forces, the accuracy of the one or more second force component(s) is better than the accuracy of the one or more first force component(s).

[0242] Based on these observations, several measurement principles for determining the one or more force components of the applied force, were developed.

[0243] FIG. 9 shows that one ore more force components, e.g. a set of three force components (Fx, Fy, Fz) can be derived from the signals obtained from the magnetic sensors and / orfrom the signals obtained from the pressure / stress sensors.

[0244] The most simple approach is to only use the signals from the pressure / stress sensors, and convert them into force signals, e.g. using a matrix multiplication with a matrix having predefined coefficients, which may be determined during a calibration procedure, but such approach does not provide a good accuracy or a good resolution for relatively small forces. FIG. 1OA shows a flowchart of a method 1000a for determining at least three force component (e.g. Fx, Fy, Fz) of a force (e.g. F) using a sensor device as described above, e.g. in any of FIG. 1A to FIG. 7B, or e.g. in any of FIG. 14 to FIG. 19, or variants thereof. The method comprises the steps of: a) receiving 1002 a first set of signals (e.g. ml, m2, m3) from the at least three magnetic sensors (e.g. Ml, M2, M3), and determining one or more first force components (e.g. a first force component Flz or a first set of three orthogonal force components Fix, Fly, Flz) based on this first set of signals; b) receiving 1003 a second set of signals (e.g. si, s2, s3) from the at least three pressure or stress sensors (e.g. Pl, P2, P3), and determining one or more second force components (e.g. a second force component F2z or a second set of three orthogonal force components F2x, F2y, F2z) based on this second set of signals; c) determining 1004 said one or more force components (e.g. Fz; Fx, Fy, Fz) of the force (e.g. F) based on said one or more first force components (Fix, Fly, Flz) and / or based on said one or more second force components (F2x, F2y, F2z).

[0245] The method may further comprise step d) of performing 1005 a consistency check between the first and the second set of sensor signals, or between the first and second force component(s), or between the first set and the second set of force components, and providing a result of the consistency check (e.g. an error signal).

[0246] Several variants are contemplated, for example:

[0247] In an embodiment, step a) comprises: determining said one or more first force components based on pairwise differences between the first set of signals (ml, m2, m3). These signals may be less sensitive to an external disturbance field.

[0248] In an embodiment, the sensor device contains two magnetic sensors, each configured for measuring an in-plane magnetic field component (e.g. Bx), and the magnitude of the force Fz is calculated as a function of a pairwise difference between these two signals, e.g. as a polynomial function, or as a linear function.

[0249] In an embodiment, step a) comprises; determining a first force component (Flz) oriented in a direction perpendicular to the substrate; and step b) comprises: determining a second force component (F2z) oriented in said direction perpendicular to the substrate; and step c) comprises: determining a component of the force (F) to be measured as the first force component (Flz) if this value is smaller than a first predefined threshold value (e.g. if Flz<Tlz), otherwise determining said component (Fz) of the force to be measured as the second force component (F2z).

[0250] In an embodiment, step a) comprises; determining a first force component (Flz) oriented in a direction perpendicular to the substrate; and step b) comprises: determining a second force component (F2z) oriented in said direction perpendicular to the substrate; and step c) comprises: determining a component of the force (F) to be measured as the second force component (F2z) if this value is larger than a second predefined threshold value (e.g. if F2z>T2z), otherwise determining said component (Fz) of the force to be measured as the first force component (Flz).

[0251] In an embodiment, step a) comprises; determining a first force component (Flz) oriented in a direction perpendicular to the substrate; and step b) comprises: determining a second force component (F2z) oriented in said direction perpendicular to the substrate; and step c) comprises: determining a component of the force to be measured as a linear combination of the first force component (Flz) and the second force component (F2z). The weighting factors may be determined in function of the first and / or second force vector, e.g. to cause a smooth transition between being 100% derived from the magnetic signals for weak forces, and 100% derived from the pressure / stress sensors for strong forces. The weighting factors may be predefined constant values, which may be hard-coded, and / or may be stored in a non-volatile memory (e.g. as described in FIG. 20 to FIG. 22). The weighting factors may be temperature dependent values.

[0252] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force (e.g. force vector Fx, Fy, Fz) to be measured as the first set of force components if each of the values of the first set of force components is smaller than a first predefined threshold value, and determining the force to be measured as the second set of force components otherwise.

[0253] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force (e.g. force vector Fx, Fy, Fz) to be measured as the first set of force components if at least one of the values of the first set of force components is smaller than a first predefined threshold value (Tl), and determining the force to be measured as the second set of force components otherwise.

[0254] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force (e.g. force vector Fx, Fy, Fz) to be measured as the second set of force components if each of the values of the second set of force components is larger than a second predefined threshold value (T2), and determining the force to be measured as the first set of force components otherwise.

[0255] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force (e.g. force vector Fx, Fy, Fz) to be measured as the second set of force components if at least one of the values of the second set of force components is larger than a second predefined threshold value (T2), and determining the force to be measured as the first set of force components otherwise. In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining each component (Fx, Fy, Fz) of the force to be measured as the corresponding component from the first set if this value (e.g. Fix) is smaller than a first predefined threshold value (Tl), and as the corresponding component from the second set (e.g. F2y) otherwise.

[0256] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining each component (Fx, Fy, Fz) of the force to be measured as the corresponding component from the second set if this value (e.g. F2x) is larger than a second predefined threshold value (T2), and as the corresponding component from the first set (e.g. Fly) otherwise.

[0257] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and determining a first magnitude of this first force vector (e.g. as the sum of squares of the values Fix, Fly, Flz, or as the square root of this sum); and step b) comprises: determining a second set of three force components (F2x, F2y, F2z) and determining a second magnitude of this second force vector (e.g. by calculating a sum of squares of the values F2x, F2y, F2z, or as the square root of this sum); and step c) comprises: determining the force to be measured as the first force vector if the first magnitude is smaller than a first predefined threshold (e.g. T3), and determining the force to be measured as the second force vector otherwise.

[0258] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and determining a first magnitude of this first force vector (e.g. as the sum of squares of the values Fix, Fly, Flz, or as the square root of this sum); and step b) comprises: determining a second set of three force components (F2x, F2y, F2z) and determining a second magnitude of this second force vector (e.g. by calculating a sum of squares of the values F2x, F2y, F2z, or as the square root of this sum); and step c) comprises: determining the force to be measured as the second force vector if the second magnitude is larger than a second predefined threshold (e.g. T4), and determining the force to be measured as the first force vector otherwise.

[0259] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force as a set of three force components (Fx, Fy, Fz) wherein each component (e.g. Fx) is calculated as a linear combination, e.g. an average or weighted average between the corresponding component (e.g. Fix) of the first set and a corresponding component (e.g. F2x) of the second set. The weighting factors may be determined in function of the magnitude of the first and / or second force vector, e.g. to cause a smooth transition between being 100% derived from the magnetic signals for weak forces, and 100% derived from the pressure / stress sensors for strong forces. The weighting factors may be predefined constant values, which may be hard-coded, and / or may be stored in a non-volatile memory (e.g. as described in FIG. 20 to FIG. 23). The weighting factors may be temperature dependent values.

[0260] In an embodiment, step a) comprises; determining a first set of three force components (Fix, Fly, Flz); and step b) comprises: determining a force component F2z (e.g. oriented perpendicular to the substrate comprising the pressure / stress sensor); and step c) comprises: determining a normal force component (Fz) of the force based on a weighted average of Flz and F2z, e.g. using predefined constants, or using temperature dependent constants; and determining a shear force component (Fx, Fy or Fsh) based solely on the first force components (Fix, Fly, Fz).

[0261] In an embodiment, the method further comprises a step of performing a consistency check between the first and the second set of sensor signals, and / or between the first (Flz) and second (F2z) force component, or between the first set (Fix, Fly, Flz) and second set (F2x, F2y, F2z) of force components, and providing a result of the consistency check (e.g. an error signal). The consistency test may for example be based on an absolute or relative difference between Fix and F2x, or between Fly and F2y, or between Flz and F2z, or between said first amplitude and said second amplitude of the force vector. If an inconsistency is detected, this may be caused by a magnetic disturbance field. The inconsistency may be output or transmitted as an error signal.

[0262] In an embodiment, the method further comprises a step of measuring or estimating a temperature of the elastomer; and step a) comprises determining said one or more first components (Fix, Fly, Flz) taking into account said measured or estimated temperature, e.g. taking into account a temperature dependent flexibility of the elastomer.

[0263] FIG. 10B shows a flow-chart of a method 1000b of determining one or more force components, which can be seen as a variant of the method of FIG. 10A, comprising the steps of: i) providing a sensor arrangement comprising one or more magnetic sensors (e.g. Ml, M2, M3), and one or more pressure or stress sensor (e.g. P1,P2,P3), and an elastomer in contact with the pressure sensors, and magnet material arranged in the elastomer; a) receiving 1002b one or more first sensor signal from one or more magnetic sensors, and determining one or more first force components (e.g. Fix, Fly, Flz) based on this one or more first sensor signal; b) receiving 1003b one or more second sensor signal from one or more pressure / stress sensors, and determining one or more second force components (e.g. F2z) based on this one or more second sensor signal; c) determining 1004b one or more force component based on said one or more first force components (e.g. Fix, Fly, Flz) and / or based on said one or more second force component (e.g. F2z).

[0264] The same variants as described above (in relation to the method of FIG. 10A) are contemplated, mutatis mutandis. In all of these variants, the one or more first force components (Fix, Fly, Flz) may be determined based on magnetic field component signals, or may be determined based on magnetic field difference signals. The latter is less sensitive to an external disturbance field.

[0265] FIG. IOC shows a flow-chart of a method 1000c of determining one or more force components (Fx,Fy,Fz), which can be seen as a variant of the method of FIG. 10A or a variant of FIG. 10C, wherein step i) comprises: providing a sensor arrangement comprising a first substrate with at least three magnetic sensors (e.g. at least three 2D pixels, or at least three 3D pixels, or at least four 2D pixels, or at least four 3D pixels, e.g. arranged as illustrated in FIG. 15), and a second substrate with one or more pressure / stress sensors, and an elastomer in contact with the one or more pressure sensors, and magnetic material (e.g. a magnet) arranged in the elastomer. The steps a) to d) are identical to those of FIG. 10B, but take into account that there may be only one second force component, namely F2z.

[0266] In this method, the one or more first force components (Fix, Fly, Flz) may be determined based on magnetic field component signals, or may be determined based on magnetic field difference signals. The latter is less sensitive to an external disturbance field.

[0267] In this method, the Fx and Fy component (i.e. shear components) of the force may be determined based on the first force components (e.g. by setting Fx=Flx, and Fy=Fly), and the Fz component (i.e. normal component) of the force can be determined in any of the ways described above (in particular in relation to FIG. 10A), e.g. as a weighted average of Flz and F2z, or as Flz (e.g. If Flz is smaller than a predefined threshold value), or as F2z (e.g. if F2z is larger than a predefined threshold value). Apart from this, the same variants as described above (in relation to the method of FIG. 10A) are contemplated, mutatis mutandis.

[0268] FIG. 11 shows an illustrative example of a high-level block diagram of a sensor device 1100 comprising one or more, e.g. at least three magnetic sensors Ml, M2, M3 and one or more pressure / stress sensors, e.g. a plurality of at least three pressure / stress sensors Pl, P2, P3. The magnetic sensor(s) and the one or more pressure sensor may be arranged as described and illustrated in FIG. 1 to FIG. 7B, or as illustrated in FIG. 14 to FIG. 19, or variants thereof, but other arrangements within the scope of the claims are also contemplated.

[0269] The sensor device 1100 may further comprise a temperature sensor TS. This temperature sensor may be configured for measuring or estimating a temperature of the elastomer.

[0270] The sensor device 1100 typically also comprises a biasing and readout circuit (not shown) for biasing the sensors (e.g. with a constant voltage or a constant current), and / or for reading out the signals from the sensors, and for optionally amplifying and digitizing these signals using at least one analog-to- digital convertor (ADC), but such circuits are well known in the art, and not the main focus of the present invention, and hence do not need to be described in detail. If the sensor device comprises at least one reception coil and at least one excitation coil, the sensor device 1100 may also comprise an excitation circuit for exciting the at least one excitation coil with an alternating voltage or current signal, and may also comprise a demodulation circuit for demodulating at least one signal obtained from the at least one reception coil.

[0271] The sensor device 1100 of FIG. 11 further comprises a processing circuit 1130, preferably comprising a programmable processor, e.g. a microprocessor or a DSP (digital signal processor) with an arithmetic unit, configured for performing the algorithm described in FIG. 10A or FIG. 10B described above, and / or any of the variants thereof, described above. The processing circuit 1130 may further comprise, or be connected to a non-volatile memory 1131, which may store for example one or more threshold values, one or more matrix coefficients, one or more weighting factors, a table with weighting factors as a function of temperature, one or more coefficients of a polynomial describing the first and second weighting factor as a function of temperature, etc.

[0272] Depending on the implementation, the sensor device 1100 may be configured for outputting one or more of: the one or more first force components (e.g. Flz), the one or more second force components (e.g. F2z), the one or more components of the determined force (e.g. Fz, or Fx, Fy, Fz).

[0273] The sensor device 1100 may optionally also provide an error signal, e.g. when an inconsistency is detected as described in step d) of FIG. 10, or e.g. if a magnetic disturbance field is detected.

[0274] The sensor device 1100 may be implemented in a single packaged semiconductor device, for example as illustrated in FIG. 1A to FIG. 4 or FIG. 15, where the one or more magnetic sensor elements and the one or more pressure / stress sensor(s) are preferably implemented on a single semiconductor substrate, or on two separate semiconductor substrates embedded in a single package (see e.g. FIG. 16 or FIG. 17), but the present invention is not limited thereto, and the device 1100 may for example comprise a printed circuit board with one or two packaged devices (or "chips") and optionally discrete components (see e.g. FIG. 5, FIG. 6, FIG. 7B, FIG. 18, FIG. 19).

[0275] In an embodiment, the sensor device 1100 contains only one magnetic sensor and only one pressure or stress sensor, and is configured for outputting only a single force component, e.g. Fz.

[0276] In an embodiment, the sensor device 1100 contains at least three, or at least four magnetic sensors but only one pressure or stress sensor, and is configured for outputting only a single force component, e.g. Fz.

[0277] FIG. 12 shows an illustrative example of another high-level block diagram of a sensor device 1200 which can be seen as a variant of the sensor device of FIG. 11, comprising a first processing circuit 1230 connected to one or more, e.g. at least three magnetic sensors Ml to M3, and optionally also connected to a temperature sensor TS, and configured for determining the one or more first force components e.g. Flz or (Fix, Fly, Flz); and comprising a second processing circuit 1240 connected to at least one, or at least three pressure / stress sensors Pl to P3, and configured for determining the one or more second force components e.g. F2z or (F2x,F2y,F2z). For the same reasons as mentioned above, biasing and readout circuitry is not shown. While not shown, each of the first and second processing circuit may comprise a non-volatile memory, or be connected thereto.

[0278] In the example of FIG. 12, the first processing circuit 1230 provides the one or more first force component (e.g. Flz or Flx,Fly,Flz) to the second processor circuit 1240, and the second processing circuit provides the result of the force measurement. In other words, in this embodiment, the first processing circuit 1230 is configured to perform step a) of FIG. 10, and the second processing circuit 1240 is configured to perform step b) and step c) of the method FIG. 10, and optionally also step d).

[0279] In a variant (not shown), the second processing circuit 1240 is configured to perform step b) and provide its output to the first processing circuit 1230, and the first processing circuit 1230 is configured to perform step a) and step c), and optionally also step d) of the method of FIG. 10.

[0280] FIG. 13 shows an illustrative example of yet another high-level block diagram of a sensor device 1300 which can be seen as another variant of the sensor device of FIG. 11 or FIG. 12, wherein the first processing circuit 1330 is configured to perform step a), the second processing circuit 1340 is configured to perform step b), and another processor 1350, for example an ECU, is configured for performing step c) of the method of FIG. 10, and may be referred to as "combiner circuit". In the example shown, each of the first and second processing circuit is connected to the combiner circuit via a separate communication line, but in a variant both the first and second processing circuit are communicatively connected to the combiner circuit 1350 via a communication bus (not explicitly shown).

[0281] FIG. 14 shows a substrate 1401 (e.g. a semiconductor substrate or a printed circuit board) comprising four magnetic sensors Ml, M2, M3, M4 (e.g. four horizontal Hall elements, or four 2D magnetic pixels, or four 3D magnetic pixels) and one or more pressure / stress sensors Pl, and an elastomer 1410 comprising a magnet 1404, as may be used in embodiments of the present invention. The elastomer may be in direct contact with the substrate 1401 (e.g. similar to FIG. 3) or may be applied above the packaged substrate (e.g. similar to FIG. 1 or FIG. 2). The magnet 1404 may be an axially magnetized two-pole cylindrical or disk-shaped magnet. The main purpose of FIG. 14 is to provide an example of a pressure sensor arrangement having four magnetic sensors, and less than three pressure sensors.

[0282] FIG. 15 shows a semiconductor substrate 1501 comprising four magnetic sensors in the form of four 3D magnetic pixels Ml, M2, M3, M4, and one pressure / stress sensor Pl. In this example, each 3D magnetic pixel comprises an integrated magnetic concentrator (IMC) and four horizontal Hall elements arranged near a periphery of the IMC disk, angularly spaced by multiples of 90°. Formulas for determining magnetic field components, magnetic field differences are provided. In the example shown in FIG. 15, the four magnetic sensors are arranged on a virtual circle, and are angularly spaced by 90°, but they could also be located on a virtual ellipse.

[0283] In the example shown in FIG. 15, the pressure sensor is arranged inside the circle, more specifically at the centre of the virtual circle, but that is not absolutely required.

[0284] In a variant (not shown), each 3D magnetic pixel comprises a horizontal Hall element and two or four vertical Hall elements, arranged near the sides of the horizontal Hall element.

[0285] FIG. 16 shows a cross-sectional view of a force sensor device 1600 comprising a first semiconductor substrate 1601a comprising one or more, e.g. at least three, or at least four magnetic sensors Ml, M2, M3, M4, and a second semiconductor substrate 1601b comprising one or more, e.g. at least three pressure or stress sensors (only one pressure sensor Pl is shown).

[0286] In the example of FIG. 16, the first semiconductor substrate 1601a is mounted on top of a lead frame, and the second semiconductor substrate is mounted on top of the first semiconductor substrate. The two semiconductor substrates have a fixed position relative to each other. The two semiconductor substrate may be wire-bonded to the lead frame using bond-wires. The two substrates and the bond wires (if present) are encapsulated by a moulding compound 1602 to form a single packaged device 1600. The package has an opening for receiving a bottom portion of an elastomer 1610. The elastomer comprises a magnet 1604.

[0287] The sensor device 1600 of FIG. 16 can be seen as a variant of the sensor device 400 of FIG. 4. The main difference being that the device 1600 comprises two separate semiconductor substrates, mounted on top of each other, and that the first semiconductor substrate 1601a preferably comprises four 3D magnetic pixels located on a virtual circle or virtual ellipse, and that the second semiconductor substrate 1601b preferably comprises less than three pressure sensors. Preferably an orthogonal projection of the pressure sensor(s) onto the first semiconductor substrate is located inside the virtual circle or the virtual ellipse. While not shown, the elastomer 1610 may have a dome shaped upper surface.

[0288] FIG. 17 shows a cross-sectional view of a force sensor device 1700, which can be seen as a variant of the sensor device 1600 of FIG. 17. The main difference being that the first semiconductor substrate 1701a (comprising the magnetic sensors) is mounted to a bottom side of a lead frame, while the second semiconductor substrate 1701b (comprising at least one pressure sensor) is mounted to a top side of the lead frame. This device offers the advantage that no mechanical stress is exerted upon the magnetic sensors, caused by the force is applied on the elastomer. Everything else described for the sensor device 1600 is also applicable here, mutatis mutandis. FIG. 18 shows a cross-sectional view of a force sensor device 1800 comprising: a first semiconductor substrate 1801a comprising at least one magnetic sensor, e.g. at least three or at least four magnetic sensors, e.g. four 3D magnetic pixels arranged as illustrated in FIG. 15; and a second semiconductor substrate 1801b comprising at least one pressure or stress sensor (only one pressure sensor Pl is shown). The first semiconductor substrate 1801a is incorporated in a first package device (or "chip") 1802a which is mounted at a bottom side of a third substrate 1806, e.g. a printed circuit board (PCB). The second semiconductor substrate 1801b is incorporated in a second package device (or "chip") 1802b which is mounted at a top side of the third substrate 1806, preferably at a position opposite the first packaged device.

[0289] Preferably the first substrate comprises four 3D magnetic pixels located on a virtual circle or a virtual ellipse, and preferably the second chip 1802b is mounted such that an orthogonal projection of the at least one pressure sensor upon the first semiconductor substrate 1801a is located inside said virtual circle or said virtual ellipse.

[0290] In the example shown in FIG. 18, the elastomer 1810 is applied in a similar manner as shown in FIG. 6, but that is not absolutely required, and in a variant the elastomer 1810 is applied as illustrated in FIG. 1 (on top of the package, not extending beyond the package, and the package has to recess), or as illustrated in FIG. 2 (on top of the package, not extending beyond the package, but the package has a recess), or as illustrated in FIG. 3 or FIG. 4 (above the package, the package having a recess, the elastomer being in direct contact with the substrate that contains the at least one sensor element).

[0291] FIG. 19 shows an example of such a variant.

[0292] While not explicitly shown, the elastomer of the devices of FIG. 16 to FIG. 19 may have a dome shaped upper surface.

[0293] FIG. 20 shows measurement results of an experiment wherein a normal force is applied to a sensor device as described above. More specifically, FIG. 20 shows a graph with many measurement points, illustrating values of the normal force component Flz derived from the magnetic sensor signals (indicated by a black circle), and values of the normal force component F2z derived from the pressure or stress sensor signals (indicated by a letter x), while increasing the force (i.e. while compressing) or while decreasing the force (i.e. while releasing).

[0294] The inventors surprisingly found that the second force component F2z showed a little hysteresis, but that the first force components Flz showed a lot of hysteresis. But even more surprisingly found that the hysteresis worked in opposite ways for the magnetic sensor signals and the pressure sensor signals. Indeed, the value of Flz derived from the magnetic sensor signals when releasing is larger than the value of Flz when compressing, but the value of F2z derived from the pressure / stress sensor signals when releasing is smaller than the value of F2z when compressing. They surprisingly found that by combining the value Flz and F2z, the hysteresis of the elastomer can be strongly reduced. In an embodiment, the normal force component Fn is determined as a linear combination, or as a weighted average of Flz and F2z, e.g. in accordance with the formula: Fn=wl*Flz+w2*F2z, where wl and w2 are weighting factors. The weighting factors may be predefined constants, or may be dependent on temperature. In the latter case, the formula can be written as: Fn=wl(T)*Flz+w2(T)*F2z.

[0295] FIG. 21A shows a graph with many measurement values of Flz and F2z obtained from an experiment wherein a normal force of various amplitudes is repeatedly applied and released, showing a behaviour with strong hysteresis.

[0296] FIG. 21B shows a graph with the normal force Fn determined as a weighted average of the first and second force component Flz and F2z using predefined constant weighting factors, showing a highly linear behaviour with a strongly reduced hysteresis.

[0297] FIG. 22 shows a data flow diagram illustrating how the first sensor signals obtained from the at least three magnetic sensors, and the second sensor signal(s) obtained from the at least one pressure or stress sensor, can be processed.

[0298] In block 2220 the first sensor signals are converted into one or more first force components, e.g. Flz, Fix, Fly, e.g. using known techniques, or using linear regression techniques, or using an artificial neural network, e.g. based on magnetic field component signals, or based on magnetic field difference signals, optionally further taking into account a temperature signal.

[0299] In block 2221 the second sensor signal(s) is / are converted into one or more second force components, e.g. F2z, using known techniques, e.g. using a linearization function, or a piecewise linear approximation function, or a lookup-table optionally with interpolation.

[0300] In block 2222 a a direction-independent magnitude of the shear force Fsh may be calculated. In an embodiment, the value of Fsh is derived from Fix and Fly, e.g. in accordance with the formula: Fsh = sqrt(sqr(Flx)+sqr(sqr(Fly)).

[0301] In block 2223 a value of the normal force component Fn can be calculated as a linear combination of Flz and F2z, for example as a weighted average of Flz and F2z, e.g. in accordance with the formula: Fn=wl*Flz+w2*F2z, where wl and w2 are predefined constants, or in accordance with the formula: Fn=wl(T)*Flz+w2(T)*F2z, where wl(T) and w2(T) are predefined functions of temperature.

[0302] Finally, while most embodiments are described using magnetic sensing elements such as Hall sensors for sensing or detecting one or more characteristics of a static magnetic field generated by a permanent magnet, the present invention is not limited thereto, and the magnetic sensor can also be implemented using one or more detection coils or inductors, e.g. planar coils, e.g. implemented in a printed circuit board or in the "interconnection stack" of a semiconductor substrate, for sensing one or more characteristics of an alternating magnetic field. In this case, the magnetic material may be an electrically conductive magnetic material, for example an electrically conductive soft magnetic material, or an electrically conductive ferromagnetic material. The electrically conductive magnetic material may be arranged for indirectly generating a secondary magnetic field in response to a primary magnetic field generated by one or more excitation coils, which may also be implemented in said printed circuit board or in said "interconnection stack" of the semiconductor substrate, for example using a coil arrangement as described in EP3961926(A1), in particular in FIG. 8(a) to FIG. 9(d), or FIG. 17(a) to FIG. 19 thereof, but not limited hereto, and without requiring that at least one component or bond pad is located inside said inner periphery. The one or more excitation coils may be located in the vicinity of the detection coil. It is an advantage of embodiments using detection coils and conductive magnetic material that a permanent magnet may not be required.

[0303] REFERENCE NUMBERS:

[0304] (modulo 100):

[0305] -00 force sensor device or tactile sensor device

[0306] -01 substrate (e.g. semiconductor substrate)

[0307] -02 (e.g. plastic) mould compound

[0308] -03 leads (or pins) of a leadframe

[0309] -04 magnet (e.g. solid magnet or bulk magnet) or magnetic particles

[0310] -05 cavity or recess (in the moulded package)

[0311] -06 substrate (e.g. PCB)

[0312] -07 integrated circuit, (e.g. chip, packaged semiconductor device)

[0313] -08 opening

[0314] -10 elastomer

[0315] -11 first surface area (in direct or indirect contact with pressure / stress sensors)

[0316] -12 second surface area (for sensing the force to be measured)

[0317] -13 cavity (e.g. air cavity)

[0318] Mi magnetic sensors mi signals from magnetic sensors

[0319] Pi pressure / stress sensor pi signals from pressure / stress sensors

[0320] TS temperature sensor ts signal from temperature sensor

Claims

Claims1. A sensor device (100; 200; 300; 400; 500; 600; 700; 1100; 1200; 1300; 1400; 1500; 1600; 1700; 1800; 1900) for sensing a mechanical force (F), the sensor device comprising:- a substrate (101; 201; 301; 401; 501; 601; 706; 1401; 1501; 1601a; 1701a; 1801a; 1901a) comprising one or more magnetic sensor (Ml, M2, M3) for sensing one or more characteristics of a magnetic field, and for providing one or more first sensor signals (ml, m2, m3);- an elastomer (110) having a first surface area (111) fixedly arranged relative to the substrate, and having a second surface area (112) for receiving said force (F) to be measured;- magnetic material (104) for generating said magnetic field, the magnetic material being arranged or embedded inside the elastomer (110) such that the magnetic material will move when said force (F) is exerted upon the second surface area (112);- one or more pressure or stress sensors (Pl, P2, P3) arranged for directly or indirectly sensing a pressure or stress induced by said force (F), and configured for providing one or more second sensor signals (pl, p2, p3);- a processing circuit (1130; 1230,1240; 1330, 1340, 1350) configured for determining one or more force components (Fz; Fx, Fy, Fz) of the force (F) exerted upon the second surface area (112), based on the one or more first sensor signals (ml, m2, m3) and the one or more second sensor signals (pl, p2, p3); wherein the one or more magnetic sensor and the one or more pressure or stress sensor have a fixed position relative to each other.

2. A sensor device according to claim 1, wherein the second surface area (112) has a dome shape.

3. A sensor device according to claim 1 or 2, wherein the substrate comprises said one or more magnetic sensors and said one or more pressure or stress sensors; or wherein the substrate comprising said one or more magnetic sensors is a first substrate, and the sensor device further comprises a second substrate, and the second substrate comprises said one or more pressure or stress sensors.

4. A sensor device (500; 600) according to any of the claims 1 to 3, wherein the substrate comprising the one or more magnetic sensors is a semiconductor substrate, and the one or more magnetic sensors are embedded in the semiconductor substrate (501; 601), and the semiconductor substrate is incorporated in a packaged device (507; 607), and the one or more pressure or stress sensors are discrete components surrounding said packaged device (507; 607).

5. A sensor device according to any of the claims 1 to 3, wherein the substrate comprising the one or more magnetic sensors is a first substrate, and the sensor device further comprises a second substrate, and the second substrate is a semiconductor substrate comprising the one or more pressure or stress sensors, and the second substrate is incorporated in a packaged device, and the one or more magnetic sensors are discrete components surrounding said packaged device.

6. A sensor device (700) according to any of the claims 1 to 3, wherein the substrate (706) is a printed circuit board; and wherein the one or more magnetic sensors (Ml, M2, M3) and the one or more pressure or stress sensors (Pl, P2, P3) are discrete components mounted on the printed circuit board.

7. A sensor device (700) according to any of the previous claims; wherein the elastomer (710a; 710b) has an overarching or bridge-like shape with a hollow cavity (713) and a supporting rim or supporting legs; and one of the following arrangements: i) wherein the one or more magnetic sensors (Ml, M2, M3) are arranged under or inside said cavity (713) and the one or more pressure or stress sensors (Pl, P2, P3) are arranged under said supporting rim or supporting legs; ii) wherein the one or more magnetic sensors (Ml, M2, M3) and the one or more pressure or stress sensors (Pl, P2, P3) are arranged under or inside said cavity (713).

8. A sensor device (700) according to any of the previous claims, wherein the substrate comprises at least three magnetic sensors (Ml, M2, M3) arranged on a first virtual circle; and wherein the sensor device comprises at least three pressure or stress sensors (Pl, P2, P3) arranged on a second virtual circle; wherein the second virtual circle is concentric with the first virtual circle, or wherein an orthogonal projection of the second virtual circle upon the substrate comprising the first virtual circle, is concentric with the first virtual circle.

9. A sensor device (1500; 1600; 1700; 1800; 1900) according to any of the previous claims, wherein the substrate comprises at least three magnetic sensors (Ml, M2, M3) arranged on a virtual circle or a virtual ellipse;and wherein orthogonal projection of the one or more pressure or stress sensors onto the substrate are located inside said virtual circle or said virtual ellipse.

10. A sensor device according to any of the previous claims, wherein the processing circuit is configured for determining one or more first force components based on the one or more first sensor signals obtained from the one or more magnetic sensors (Ml, M2, M3); and wherein the processing circuit is configured for determining one or more second force components based on the one or more second sensor signals obtained from the one or more pressure or stress sensors (Pl, P2, P3); and wherein the processing circuit is further configured for determining one or more force components of the force (F) exerted upon said second surface (112) based on the one or more first force components and the one or more second force components.

11. A sensor device according to claim 10, comprising at least two magnetic sensors; and wherein the processing circuit is configured for determining the one or more first force components based on one or more pairwise differences between first sensor signals obtained from the at least two magnetic sensors.

12. A sensor device according to claim 10 or 11, comprising four magnetic sensors (Ml, M2, M3, M4), each capable of measuring three orthogonal magnetic field components (Bxl,Byl,Bzl; Bx2,By2,Bz2; Bx3,By3,Bz3; Bx4,By4,Bz4); and wherein the processing circuit is configured for determining at least two magnetic field differences (dBxdx, dBydx, dBzdx, dBxdy, dBydy, dBzdy) between parallel magnetic field components; and wherein the processing circuit is further configured for determining the one or more first force components (Fix, Fly; Flz) based on said magnetic field differences.

13. A sensor device according to claim 10 or 11, comprising four magnetic sensors (Ml, M2, M3, M4), each capable of measuring at least two orthogonal magnetic field components (Bxl,Bzl; By2,Bz2; Bx3,Bz3; By4,Bz4); and wherein the processing circuit is configured for determining at least two magnetic field differences (dBxdx, dBzdx, dBydy, dBzdy); and wherein the processing circuit is configured for determining the one or more first force components (Fix, Fly, Flz) based on said magnetic field differences.

14. A sensor device according to any of the claims 10 to 13, wherein the processing circuit is configured for determining the value or values of the one or more components (Fx, Fy, Fz) of the force (F) exerted upon said second surface (112) as this one or more first force component (Fix, Fly, Flz) if this first component value is smaller than a first threshold value, or as the one or more second force component (F2x, F2y, F2z) otherwise; or wherein the processing circuit is configured for determining a first amplitude of a first vector corresponding with the one or more first force components (Fix, Fly, Flz), and for testing if this first amplitude is smaller than a first predefined threshold value, and if an outcome of this test is true, to determine the one or more force components (Fx, Fy, Fz) of the force to be measured based solely on the one or more first force components; and if an outcome of this test is false, to determine the one or more force components of the force to be measured based solely on the one or more second force components (F2x, F2y, F2z).

15. A sensor device according to any of the claims 10 to 14, wherein the sensor device is configured for determining and outputting three orthogonal force components (Fx, Fy, Fz) comprising a normal force component (Flz, F2z, Fn) and two shear force components (Fx, Fy); or wherein the sensor device is configured for determining and outputting two shear force components (Fx, Fy); or wherein the sensor device is configured for determining and outputting a normal force component (Flz, F2z, Fn) and a single shear force component (Fsh); or wherein the sensor device is configured for determining and outputting a single shear force component (Fsh).

16. A sensor device according to claim 15, wherein the single shear force component (Fsh) or the two shear force components (Fx, Fy) are derived from signals obtained from the one or more magnetic sensor, optionally taking into account a measured temperature value.

17. A sensor device according to claim 15 or 16, wherein the normal force component is determined based on signals obtained from both the one or more magnetic sensor and from the one or more pressure of stress sensor, optionally taking into account a measured temperature value; or wherein the normal force component (Fn) is determined as a weighted average of a first force component (Flz) and a second force component (F2z), using predefined weighting factors, or using temperature dependent weighting factors.

18. A sensor device according to any of the previous claims, wherein the processing circuit is configured or further configured for performing a consistency test between the one or more first sensor signal(s) and the one or more second sensor signal(s), or between the one or more first force components (Fix, Fly, Flz) and the one or more second force components (F2x, F2y, F2z); and if an inconsistency is detected, to determine the one or more force components of the force to be measured based solely on the one or more second force components (F2x, F2y, F2z).

19. A robotic gripper comprising two or more movable elements, each movable element comprising at least one sensor device according to any of the previous claims.

20. A method (1000) of determining one or more force component (Fz; Fx, Fy, Fz) of a force (F) using a sensor device according to any of the previous claims, the method comprising the steps of: a) receiving (1002) one or more first sensor signals (ml, m2, m3) from the one or more magnetic sensors (Ml, M2, M3), and determining one or more first force components (Flz; Fix, Fly, Flz) based on this one or more first sensor signal (ml, m2, m3); b) receiving (1003) one or more second sensor signals (si, s2, s3) from the one or more pressure or stress sensors (Pl, P2, P3), and determining one or more second force components (F2z; F2x, F2y, F2z) based on this one or more second sensor signal (si, s2, s3); c) determining (1004) one or more force components (Fz; Fx, Fy, Fz) of the force (F) to be measured based on said one or more first force components (Fix, Fly, Flz) and based on said one or more second force components (F2x, F2y, F2z); and optionally wherein the method further comprises a step of performing a consistency check between the one or more first sensor signal and the one or more second sensor signals, and / or between one or more first force components (Flz; Fix, Fly, Flz) and the one or more second force components (F2z; F2x, F2y, F2z); and optionally wherein the method further comprises a step of measuring or estimating a temperature of the elastomer, and wherein step a) comprises determining said one or more first force components (Flz; Fix, Fly, Flz) taking into account said measured or estimated temperature.

21. A method according to claim 20, wherein step a) comprises: determining said one or more first force components (Flz; Fix, Fly, Flz) based on pairwise differences between the first set of signals (ml, m2, m3); or wherein step a) comprises; determining a first force component (Flz) oriented in a direction perpendicular to the substrate; and step b) comprises: determining a second force component (F2z)oriented in said direction perpendicular to the substrate; and step c) comprises: determining the force (F) to be measured as the first force component (Flz) if this value is smaller than a first predefined threshold value, otherwise determining the force (Fz) to be measured as the second force component (F2z); or wherein step a) comprises: determining a first force component (Flz) oriented in a direction perpendicular to the substrate; and step b) comprises: determining a second force component (F2z) oriented in said direction perpendicular to the substrate; and step c) comprises: determining the force to be measured as the second force component (F2z) if this value is larger than a second predefined threshold value, otherwise determining the force (Fz) to be measured as the first force component (F2z); or wherein step a) comprises; determining a first force component (Flz) oriented in a direction perpendicular to the substrate; and step b) comprises: determining a second force component (F2z) oriented in said direction perpendicular to the substrate; and step c) comprises: determining the force (F) to be measured as a linear combination of the first force component (Flz) and the second force component (F2z); or wherein step a) comprises: determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force (e.g. force vector Fx, Fy, Fz) to be measured as the first set of force components if each of the values of the first set of force components is smaller than a first predefined threshold value (Tl), and determining the force to be measured as the second set of force components otherwise; or wherein step a) comprises: determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force (e.g. force vector Fx, Fy, Fz) to be measured as the first set of force components if at least one of the values of the first set of force components is smaller than a first predefined threshold value (Tl), and determining the force to be measured as the second set of force components otherwise; or wherein step a) comprises: determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force (e.g. force vector Fx, Fy, Fz) to be measured as the second set of force components if each of the values of the second set of force components is larger than a second predefined threshold value (T2), and determining the force to be measured as the first set of force components otherwise; or wherein step a) comprises: determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force (e.g. force vector Fx, Fy, Fz) to be measured as the second set of force components if at least one of the values of the second set of force components is larger than a secondpredefined threshold value (T2), and determining the force to be measured as the first set of force components otherwise; or wherein step a) comprises: determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining each component (Fx, Fy, Fz) of the force to be measured as the corresponding component from the first set if this value is smaller than a first predefined threshold value (Tl), and as the corresponding component from the second set otherwise; or wherein step a) comprises: determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining each component (Fx, Fy, Fz) of the force to be measured as the corresponding component from the second set if this value is larger than a second predefined threshold value (T2), and as the corresponding component from the first set otherwise; or wherein step a) comprises: determining a first set of three force components (Fix, Fly, Flz) and determining a first magnitude of this first force vector; and step b) comprises: determining a second set of three force components (F2x, F2y, F2z) and determining a second magnitude of this second force vector; and step c) comprises: determining the force to be measured as the first force vector if the first magnitude is smaller than a predefined threshold, and determining the force to be measured as the second force vector otherwise; or wherein step a) comprises; determining a first set of three force components (Fix, Fly, Flz) and determining a first magnitude of this first force vector; and step b) comprises: determining a second set of three force components (F2x, F2y, F2z) and determining a second magnitude of this second force vector; and step c) comprises: determining the force to be measured as the second force vector if the second magnitude is larger than a predefined threshold, and determining the force to be measured as the first force vector otherwise; or wherein step a) comprises: determining a first set of three force components (Fix, Fly, Flz) and step b) comprises: determining a second set of three force components (F2x, F2y, F2z); and step c) comprises: determining the force as a set of three force components (Fx, Fy, Fz) wherein each component is calculated as a linear combination of the corresponding components from the first set and the second set.

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