Soft force sensor

Abstract

A soft sensor arrangement for measuring forces is presented. The soft sensor arrangement includes: a sensor; a deformable element, the deformable element being deformable due to a force; and an element for interacting with the sensor for measuring a force by deformation of the deformable element, the deformable element extending at least partially between the sensor and the element. In operation, when a deformable element extending at least partially between a sensor acting with the element and the element (130) deforms due to a force, the soft sensor arrangement receives a signal from the sensor, and estimates an intensity of the force from the received signal based on a predefined correlation between a value of the force and a value of the signal of the sensor. Furthermore, a clamp having at least two robotic fingers is disclosed wherein at least one of the at least two robotic fingers comprises a soft sensor arrangement according to the invention. The gripper is operated by extending a distance between at least two robotic fingers until the distance between the at least two robotic fingers can accommodate an object to be gripped; clamping an object by reducing a distance between the at least two robot fingers, thereby applying a force to the object; measuring the force applied to the object by the two robot fingers by the action of the sensor on the element; and controlling movement of the at least two robotic fingers based on the measurement of the force.

Description

Technical Field

[0001] The invention of the present application relates to a soft force sensor arrangement, and a corresponding method for measuring forces using the same. Background Art

[0002] Force sensors return an electronic signal that is proportional to the mechanical force applied to the sensor. In other words, force sensors convert the magnitude of the applied force into a related electronic signal. The measured force can be a mechanical quantity such as tension, pressure, weight, torque, strain, and internal stress. Force sensors have become an indispensable core component of power equipment, engineering machinery, various working machines, and industrial automation systems.

[0003] For example, using existing force sensors, the force applied to a workpiece during an automated manufacturing process can be measured in real time to control the force applied to the workpiece. In this way, the force load on the workpiece can be controlled and potentially limited during the manufacturing process. This is especially important when the workpiece is sensitive. Today, force sensors are also used when goods are automatically sorted, stored or packaged in an automated manner.

[0004] In all fields, these force sensors are used to control the force load on the object. Typically, force sensors are used in conjunction with multi-axis robotic devices to move, position and hold objects in a desired position within a desired amount of time. For example, a multi-axis robotic device may include a fixture. A fixture is a mechatronic device that applies a force and a corresponding reaction force to an object so that the object can be held by the fixture. Thus, the force and reaction force press the object against the corresponding part of the fixture so that the object contacts the corresponding fixture part. This contact causes friction between the corresponding fixture part and the object, which is proportional to the applied force and reaction force. If the friction force generated is greater than the gravity of the clamped object, the object is stably held by the fixture.

[0005] For example, DE 10 2019 201169 A1 describes a clamp of the above type, wherein the clamp consists of a clamp base, a sensor plate attached to the clamp base, at least two clamp jaws, and a one-dimensional force sensor located between the sensor plate and a clamp plate carrier, the clamp plate carrier holding the clamp jaws. Thus, the one-dimensional force sensor can measure the compressive force between the sensor plate and the clamp plate carrier.

[0006] However, the sensors described in the prior art, and therefore also the clamps described in the prior art, suffer from the disadvantage that the forces applied to the object are not measured with sufficient accuracy. This may cause damage to the clamped object due to either too much force or too little force leading to a loss of grip. Both need to be prevented, whereby an accurate force measurement is necessary. Since even very fragile sensors are used for very accurate measurements, it is also important to protect the corresponding sensor arrangement from any damage. Summary of the invention

[0007] The soft sensor arrangement according to the present invention solves the above-mentioned objects. The soft sensor arrangement according to the present invention comprises a sensor, a deformable element, and an element for acting with the sensor. The element may consist of a single element or a plurality of elements. The deformable element may be deformable and may extend at least partially between the sensor and the element. An element is deformable when it undergoes a change in shape and / or volume when an external force acts on it. Thus, deformable also means that once the external force no longer acts on the element, the element returns to its original shape and / or volume.

[0008] During operation, the object applies a force to the sensor arrangement. Thus, the element or the deformable element can be in contact with the object. The contact can be direct or indirect. The element or the deformable element can thus be in contact with the object directly or indirectly. In the case of direct contact, at least one surface of the element or the deformable element touches at least one surface of the object. In the case of indirect contact, at least some other parts are between the contact surfaces. For the element, this can be the deformable element itself, so that the element is in indirect contact with the object, but the deformable element is in direct contact. In this case, it can also be said that the element is embedded in the deformable element. Thus, the element can be partially or completely embedded in the deformable element. In the latter case, all surfaces of the element are in contact with the deformable element. It can also be said that the material of the deformable element surrounds the element. Conversely, if the deformable element is in indirect contact with the object, the element may be in direct contact with the object. However, it is also covered that other parts are in direct contact with the object, while the element and the deformable element are only in indirect contact with the object. For example, the element can be embedded in a plastic part that is in contact with the deformable element. In another example, the plastic piece still contacts the deformable element and the object, but the element is embedded in the deformable element, or the element contacts the deformable element and the plastic piece. In all three cases, the object will directly contact the plastic piece, but neither the element nor the deformable element.

[0009] Since the deformable element at least partially extends between the sensor and the element or even surrounds the element, it holds the element in a specific position relative to the sensor. This position can be defined as a first position of the element relative to the sensor. It can also be said that the deformable element holds the element at a specific distance from the sensor. If the deformable element is deformed, the element itself performs a coaligned movement in the deformation direction of the deformable element. If the deformation is compression, the distance from the element to the sensor is reduced; and if the deformation is tension, the distance is increased.

[0010] The deformation of the deformable element means that at least one spatial extension of the deformable element in at least one corresponding spatial dimension is changed. Thus, the deformable element of the sensor arrangement can be soft in the sense that it is deformable. The deformability (and in particular how much the deformable element can be deformed) depends on the material used for the deformable element. For example, the deformable element can be made of a flexible material. A flexible material is a material that returns to its initial shape once an external force is released. Therefore, if any external force is released, the deformable element can return to its initial shape. Therefore, the deformable element can also be referred to as a flexible element or an elastic element. In another example, the deformable element can be an elastomer. Elastomers are typically made of monomers linked by weak intermolecular forces. Due to the weak intermolecular forces of the chemical elements of the elastomer, changes in the conformation of the compound are possible without destroying the covalent bonds or only partially destroying the covalent bonds. This causes the elastomer to be viscous and elastic at the same time. Therefore, the elastomer can be deformed by an external force.

[0011] The deformation of the deformable element causes the element to move to a second position that is different from the first position. If the deformable element is compressed, the second position of the element is closer to the sensor than the first position of the element. If tension is applied, the second position of the element is further away from the sensor than the first position. The change in position can be detected by the sensor of the sensor arrangement acting on the element. When acting on the sensor, the element affects the measurement of the sensor. It can also be said that the element is coupled to the sensor by a physical effect that is a characteristic of the sensor and the element. This coupling of the element to the sensor depends on the position of the element relative to the sensor. It can also be said that by position-dependent coupling, the measurement of the sensor is a unique function of the position of the element relative to the sensor. In this sense, it can be said that the sensor used in the sensor arrangement is a distance measuring sensor. Such a sensor returns an electronic signal that is proportional to the position of the element relative to the sensor.

[0012] If no external force is applied to the sensor arrangement, the deformable element is not deformed and the element is at a first position relative to the sensor. Thus, a first signal can be measured by the sensor, which corresponds to a zero force measurement. If a limited external force is applied to the element, the deformable element is deformed and the element moves to a second position different from the first position. This second position of the element relative to the sensor generates a second signal of the sensor, which corresponds to the applied external force. Since the first signal and the second signal can be uniquely mapped to the respective applied external forces, the distance measurement allows the applied external force to be determined. In other words, when the force applied to the sensor arrangement deforms the deformable element, the force can be measured by the displacement of the element. Since the change in the interaction of the element with the sensor can be measured with high accuracy, the applied force can be measured with high accuracy. In other words, the change in the effect of the element on the sensor allows the external stimulus causing the change, i.e. the applied external force, to be inferred. For example, as described above, the sensor can be sensitive to the displacement of the element relative to the sensor.

[0013] In this way, the soft sensor arrangement according to the invention allows for the first time to perform an accurate measurement of force by measuring the deformation of a deformable element. It is also possible to measure the applied force with high granularity by indirectly measuring the force by causing the force to act on the deformable element and thereby changing the element's stimulation of the sensor.

[0014] In a preferred embodiment of the invention, the further deformable element is in contact with the deformable element and / or with the element. The further deformable element may extend at least partially between the deformable element and the object. It can also be said that in this case the deformable element is a first deformable element and the further deformable element is a second deformable element. The second deformable element may be in contact with the object when the object is moved towards the second deformable element. When the object applies a force to the second deformable element during such contact, the second deformable element applies a force to the first deformable element and / or the element, and the first deformable element deforms, as described above. Thereby, the second deformable element may also be deformed. However, the deformability of the second deformable element may be less than the deformability of the first deformable element, or the second deformable element may not be deformed at all. In the absence of any applied force, the thickness of the second deformable element perpendicular to the sensor surface may be less than the thickness of the first deformable element. The second deformable element may have a different bulk modulus and / or shear modulus compared to the first deformable element. In particular, the bulk modulus of the second deformable element may be higher than the bulk modulus of the first deformable element. It can also be said that the stiffness of the second deformable element can be greater than the stiffness of the first deformable element and / or the flexibility of the second deformable element can be less flexible than the first deformable element. Therefore, due to being more rigid, the second deformable element is less likely to be damaged by contact with the object than the first deformable element. It can also be said that the second deformable element provides a protective layer to the first deformable element, which prevents damage to the first deformable element by avoiding direct contact between the first deformable element and the object. Therefore, by virtue of the second deformable element, the deformation properties of the first deformable element are protected. In addition, the second deformable element can act as a transducer of the force applied by the object to the second deformable element. It can also be said that the second deformable element distributes the force applied by the object to the first deformable element in a homogenous and uniform manner. For example, if the contact of the second deformable element with the object is above a first contact surface, and the contact of the element and / or the first deformable element with the second deformable element is above a second contact surface, the second deformable element distributes the force received above the first contact surface to the second contact surface. Depending on the shape of the object, the first contact surface can be smaller than the second contact surface. In this case, the second deformable element reduces the force or pressure applied to the first deformable element and / or the element compared to the case where the object would directly contact the first deformable element and / or the element itself. Thereby, the risk of damaging the first deformable element is reduced. In other words, the second deformable element avoids point stresses of the object onto the first deformable element and / or the element. In addition, or alternatively, the second deformable element may have a specific friction coefficient adapted to the object. In this way, the surface roughness of the second deformable element may be adjusted to the surface roughness of the object contacting the second deformable element.For example, if the surface of the object has a low coefficient of friction, the coefficient of friction of the second deformable element can be increased so that a stable contact of the object and the second deformable element is maintained. If the surface of the object has a high coefficient of friction, the coefficient of friction of the second deformable element can be reduced while still maintaining the same stable contact. In this way, the clamping between the object and the second deformable element can be stabilized even if the type of object changes. Thus, the second deformable element can be adjusted to the type of object without changing the first deformable element. This makes the soft sensor arrangement universal for a wide range of different objects while still using the same deformable element. It is also contemplated that the second deformable element can be reversibly attached to the first deformable element. In other words, the second deformable element can be replaceable. Thereby, different second deformable elements can be selected for different applications or for different objects.

[0015] In a further preferred embodiment of the invention, the deformable element can be characterized by its shape and / or its bulk modulus and / or its shear modulus. The shape of the deformable element in the undeformed state can be at least one of the following: a cylinder, a cube, a pyramid, or a dome. The shape and other selected properties are thus adapted to the conditions to be achieved.

[0016] In a further preferred embodiment of the invention, the deformable element may be attached to the sensor. For example, the deformable element may be bonded to the sensor. Thereby, for example, an adhesive layer (such as tape) may be used. It is also possible that the deformable element only touches the sensor without being unstably attached to the sensor. As a further example, it is also possible that the deformable element does not touch the sensor at all. In this case, free space may exist between the deformable element and the sensor, and holding means holding the deformable element spaced apart from the sensor. The aforementioned examples should not be understood as limiting.

[0017] In a further preferred embodiment of the present invention, the soft sensor arrangement may further include a mechanical stop, wherein the mechanical stop limits the deformation of the deformable element. The mechanical stop acts as a physical barrier, such as to limit the amount of deformation possible (i.e., the amount of force acting on the deformable element). The mechanical stop thereby applies a reaction force to the force applied to the deformable element. Thus, the force and the reaction force at least partially cancel each other out. It can also be said that the mechanical stop acts as a force absorber, which absorbs at least a portion of the force applied to the deformable element. The mechanical stop may be a rigid element, which is shorter than the range of the undeformed deformable element relative to the sensor than the range of the undeformed deformable element relative to the sensor. This allows the deformable element to be at least partially deformed by an amount equal to the difference in range between the mechanical stop and the deformable element in the undeformed state. The mechanical stop may also be an element composed of a material that is less elastic than the deformable element itself, rather than a rigid element. In this case, the mechanical stop does not act as a hard stop but rather as a damper, which dampens the deformation of the deformable element because a greater force must be applied to compress both the deformable element and the mechanical stop. The mechanical stop may not limit the deformation of the deformable element in at least one direction parallel to the sensor surface. It can also be said that the mechanical stop may be designed to allow the deformable element to move freely in at least one direction parallel to the sensor surface.

[0018] The mechanical stop may be assembled from a single piece of material or from a plurality of pieces of material. The mechanical stop may be constructed in a manner to at least partially surround the deformable element. Thus, the mechanical stop may also be configured to hold the deformable element in a fixed position relative to the sensor.

[0019] The mechanical stop may have a gap through which the deformable element can at least partially extend. The gap may also be referred to as a hole or recess in the mechanical stop through which the deformable element can at least partially extend.

[0020] The volume of the recess may be larger than the volume of the undeformed deformable element extending through the recess. If the shear modulus of the deformable element is not zero, an external force applied to the deformable element in a first direction causes a deformation of the deformable element in at least one direction orthogonal to the first direction. It can also be said that in this case, the deformable element undergoes not only linear compression, but also quenching. If the volume of the recess is larger than the volume of the undeformed deformable element extending through the recess, the recess may easily accommodate the quenched deformable element. In particular, it is possible that the recess is adapted to constrain the deformable element in only one direction orthogonal to the applied external force, but not in the remaining directions orthogonal to the applied external force, so that the deformable element can be freely deformed in the remaining directions orthogonal to the applied external force.

[0021] At least one edge of the mechanical stop of the soft sensor arrangement facing the deformable element may be beveled and / or rounded. An edge is a sharp part of a geometric object. It can also be said that an edge comprises one or more sharp corners. Sharp corners risk cutting into the deformable element. Therefore, removing the edge of the mechanical stop facing the object avoids damage to the deformable element. Furthermore, removing the edge from the mechanical stop creates a specific volume within the mechanical stop, which volume can be occupied by the deformable element if the deformable element is quenched.

[0022] The distance between the mechanical stop and the sensor can define a space into which the deformable element can deform when an external force is applied. Where the deformable element touches the sensor, the deformable element is at risk of experiencing the strongest quenching, because at this point any further expansion of the deformable element is limited by the sensor. It can also be said that the sensor defines a mechanical barrier that the deformable element cannot cross. Therefore, the space extending from the sensor to the mechanical stop can be defined. It can also be said that the distance from the sensor can define a pocket inside the mechanical stop. It can also be said that the space can be located between the sensor and the mechanical stop. If the deformable element is not deformed, the space may be empty. However, if the deformable element is not deformed, at least a portion of the space may also have been occupied by the deformable element. When the deformable element is deformed, the space is used to accommodate at least a portion of the deformable element. By supplying such an expansion volume to the deformable element, the space helps to limit the strain applied to the deformable element.

[0023] The mechanical stop ensures that the sensor is not damaged by excessive forces exerted on the sensor by the compressed deformable element. Overloading the force on the sensor may result in cracking and / or breaking of the sensor. In addition, the mechanical stop prevents the element from being too close to the sensor, which may cause physical damage to the sensor and impair the sensitivity of the sensor due to the element interacting with the sensor.

[0024] In another preferred embodiment of the present invention, the sensor of the soft sensor arrangement can be a passive magnetic sensor, and the element can be a magnetic field emitting element, such as a permanent magnet. A magnetic sensor is a sensor that measures at least one property of a magnetic field emitted by an element. By passive magnetic sensor, it is meant that the sensor detects at least one property of a magnetic field caused by an element, but does not create a magnetic field to be measured by itself. In general, a magnetic field is a vector field. This means that at each point in space, the magnetic field is characterized by a three-dimensional vector of magnetic field strength. A passive magnetic sensor can measure one or more magnetic fluxes obtained by projecting a magnetic field vector onto one or more surfaces associated with the passive magnetic sensor. Therefore, it can be said that at least one property measured is the magnetic flux through the corresponding surface. The measured magnetic flux is proportional to the density of magnetic field lines that pass through the corresponding surface and cut the corresponding surface at an orthogonal angle. Each of the magnetic fluxes passing through the corresponding surface causes the passive magnetic sensor to output a corresponding signal, such as a current or a corresponding voltage signal. Specifically, the output signal can be proportional to the distance from the element to the sensor. If the element changes its position, the magnetic field lines change their position. In this way, a positional change of the element directly leads to a change in the magnetic flux measured at the passive magnetic sensor. The output signal then either gives a direct indication of how the element has changed its position, or can be further processed or combined for determining the position of the element relative to the sensor. Thus, the algorithm for determining the position of the element from the measured flux signal can rely on the difference between the signals and / or calculate the gradient based on the signal measured for the element that has been displaced in the case of a deformed deformable element and the signal measured for the element in its initial position in the case of an undeformed deformable element. Then, another algorithm can be used to infer the externally applied force from the position determined by the algorithm. However, the externally applied force can also be inferred directly from the measured flux signal without calculating the position of the element as an intermediate value. In general, it can be said that a change in the interaction of the element with the passive magnetic sensor causes a change in at least one property of the magnetic field measured by the passive magnetic sensor. The algorithm can then be used to infer the external force responsible for the change in the interaction from the measured at least one property of the magnetic field.

[0025] In addition, or as an alternative, the flux gradient can be measured directly using a transducer that is sensitive to the magnetic field gradient. The use of the difference or the use of the gradient enables a stray field immune position determination because the effects of static stray magnetic fields are eliminated when the measured signal is subtracted. In addition to the magnetic flux, or as an alternative to the magnetic flux, the passive magnetic sensor can also measure the orientation of the vector of the magnetic field strength. The orientation of the vector measuring the magnetic field strength produces one or more angles, thereby describing the orientation of the magnetic field in space. Based on this orientation, the force applied to the deformable element can be derived. It is also possible to derive the angle at which the object deforms the deformable element by using the change in the orientation of the element relative to the sensor. In other words, whether the applied force is uniform or non-uniform.

[0026] A passive magnetic sensor may comprise at least one sensor element which measures at least one physical property of a magnetic field. The at least one sensor element may be a magnetoresistive sensor or a Hall sensor, or any other device suitable for measuring at least one property of a magnetic field emitted by the element.

[0027] In another preferred embodiment of the present invention, the sensor of the soft sensor arrangement may be an active magnetic sensor, and the element may be a target. The active magnetic sensor measures at least one physical property of a magnetic field. Thus, compared to the passive magnetic sensor described above, the active magnetic sensor itself creates at least one magnetic field. In other words, the active magnetic sensor does emit a magnetic field itself. The magnetic interaction of the emitted magnetic field with the target is observed by the active magnetic sensor. The active magnetic sensor may include a sensor element configured to both generate a magnetic field and measure changes in the magnetic field caused by the target. For example, a sensor element may be suitable for acting as a generator of a magnetic field in a first time interval and as a detector of changes in the magnetic field caused by the target in a second time interval. Alternatively, the active magnetic sensor may also include at least two sensor elements. Thus, at least one of the at least two sensor elements may be configured to generate a magnetic field, and at least another of the at least two sensor elements may be configured to measure changes in the magnetic field caused by the target. The sensor element configured to measure at least one physical property may be similar to the sensor element of the passive magnetic sensor described above.

[0028] The generated magnetic field is affected by the target, and at least one physical property of the affected magnetic field is measured by a sensor element configured to measure at least one physical property. The shape of the target may not be rotationally invariant. Specifically, the target may be planar or nearly planar. Thus, the target may have a shape that affects the magnetic field in a preferred direction, which shape may be substantially the same for the entire target. For example, the target may be configured so that the induced current preferably flows in a specific linear direction, so that the effect of the target on the generated magnetic field is also directional. To this end, the target may include at least one slit extending from one end of the target to the other end of the target. However, different target designs are equally possible.

[0029] It can also be said that the target affects the magnetic flux coupling between the generator of the magnetic field and the detector that measures at least one physical property of the magnetic field. The target can include a soft magnetic material or a non-magnetic conductive material. Thus, a soft magnetic material means that the magnetic material of which the target is made can be easily magnetized and demagnetized. It can also be said that a soft magnetic material is characterized by: if the external magnetic field is removed, its magnetization decays rapidly over time. Soft magnetic materials can have higher relative permeability and / or lower coercivity. Coercivity (also known as magnetic coercivity, coercive field or coercive force) is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without demagnetization. Ferromagnetic materials with high coercivity are called hard magnetic and are used, for example, to make permanent magnets. Materials with low coercivity are considered to be soft magnetic. It can also be said that a soft magnetic material may have a lower residual magnetization. Typically, but not limited to, if the coercivity of a magnetic material is less than 1000 A / m, it is called a soft magnetic material. However, the latter should only be used as an example and should not be understood as limiting.

[0030] If the target is made of a soft magnetic material, the target may affect the magnetic flux coupling by concentrating the magnetic field lines of the generated magnetic field. The soft magnetic material may consist of an isotropic material that is not characterized by any preferred direction. If the target is made of a non-magnetic conductive material, the energy may be dissipated by induced currents in the conductive material of the target. The induced currents may be eddy currents. In this case, the target affects the magnetic flux coupling by introducing magnetic field losses generated due to dissipation. Optionally, the form of the target may be such that the magnetic field lines of the generated magnetic field are aligned in a preferred direction. Additionally or alternatively, it can also be said that the target may act as a magnetic field line rectifier, which aligns the magnetic field lines in a preferred direction. If the target is positioned and / or oriented so that the preferred direction of the magnetic field lines is in the direction of the sensor element measuring at least one physical property, the at least one physical property measured will have a maximum value.

[0031] In another preferred embodiment of the present invention, the sensor of the soft sensor arrangement may include an optical receiver that detects light, wherein the detected light may be light emitted, reflected or scattered back from the element. The optical receiver outputs an electronic signal in response to the amount of light received. For example, the measured physical property may be light intensity. The element is characterized in that at least a portion of any light falling on the element is not absorbed by the element. Thus, it can be said that when light is conducted to the element, the element responds with the unabsorbed portion of the light. Such a response may be a reflection, scattering or emission of light. For example, if the element responds by reflection, the element returns the unabsorbed portion of the light at a reflection angle of the same magnitude as the angle at which the light falls on the element (Snell's law of reflection). If the element responds by scattering or by emission, the element may return the unabsorbed portion of the light at an angle that deviates from the reflection angle predicted by the law of reflection. If the element responds by emission, the wavelength of the returned light may be different from the wavelength of the light falling on the element. Thus, whether the element responds by reflection, scattering or emission, the element can return a portion of the light falling on the element to the same half solid angle as the half solid angle from which the light fell on the element. In addition to the foregoing, the element itself can also be adapted to generate light itself and emit it towards the sensor.

[0032] If the element is moved to a greater distance from the optical receiver, the optical receiver measures a lower light intensity because the returned light propagates over a larger solid angle. In contrast, when the element approaches the optical receiver, the measured light intensity increases because the optical receiver covers a larger portion of the solid angle at which the light is returned by the element. In addition, when the element changes its distance relative to the optical receiver, the angle at which the element appears at the optical receiver is also changed. Similarly, if the element changes its orientation, the intensity of the detected light changes due to the change in the angle at which the element appears at the optical receiver. This changed angle at which the element is perceived by the optical receiver has the effect that different portions of the returned light impinge on the detection area of ​​the optical receiver. Therefore, the measured light intensity is a physical property that allows the position and / or orientation of the target to be unambiguously inferred.

[0033] Those skilled in the art are aware of the fact that other physical properties of light can also be used to infer the position and / or orientation of a component (eg, the polarization state of the return light).

[0034] The optical receiver can be an avalanche photodiode, a point photodetector, a photogrammetric device, or an extended non-point detector element similar to an extended non-point detector element of a CMOS camera. However, all other types of devices that output an electronic signal in response to the amount of light received can be used as an optical receiver.

[0035] Alternatively, the light returned by the element may be originally emitted by an optical transmitter included in the sensor or by an external light source not included in the sensor. The optical transmitter or external light source may be a laser diode, a light emitting diode (LED), or any other type of light emitting device. However, the light returned by the element may also be generated by ambient lighting.

[0036] In another preferred embodiment of the present invention, the sensor may include a semiconductor package embedded with an integrated circuit (IC). In other words, the sensor may be constructed as an integrated circuit (IC), which is part of a semiconductor structure. Generally, it should be understood that an integrated circuit (IC) is a very small electronic circuit consisting of a plurality of functional units attached and / or integrated to a semiconductor substrate. For example, a functional unit may include a transistor, a diode, a Hall sensor, a coil, a laser diode, a photodetector, an electrical connection, or a waveguide, etc. The integrated circuit (IC) is embedded in the semiconductor package in the sense that the semiconductor package at least partially surrounds the integrated circuit (IC). Generally, it is advantageous to place a controller that processes a signal output by the sensor or transmits a command to the sensor not too far from the sensor itself, because this avoids signal loss caused by the resistance of the wire between the sensor and the controller. Therefore, such a controller or processing device may also be embedded in a semiconductor package together with the sensor. It is understood by those skilled in the art that the sensor or its components may be integrated with the controller in the same semiconductor substrate to form a composite integrated circuit.

[0037] Even if the integrated circuit (IC) implementing the sensor is embedded in a semiconductor package, any damage to the semiconductor package or stress applied to the semiconductor package should be avoided, because such damage may also damage the embedded integrated circuit (IC), and the stress applied to the semiconductor package may be transformed into stress on the integrated circuit (IC), which may degrade the performance of the IC.

[0038] In a further preferred embodiment example, the element may consist of a single element or a plurality of elements. This means that the element may be assembled from a single piece of material or from a collection of pieces of material. When forming the element, the pieces in the collection of pieces of material may touch each other. However, at least one piece in the collection of pieces of material may also be isolated from all other pieces of material that form the element. For example, in the case where the sensor is a magnetic sensor, the element may include one or more magnets and / or one or more conductors. In the case where the sensor is an optical sensor, the element may include one or more reflectors, scatterers or absorbers. The element may include powder. Therefore, the element may include a substance consisting of a large number of loose particles. For example, for a magnetic sensor, the element may include a powder of a magnetic compound and / or a powder of a conductive compound. In the case where the sensor is an optical sensor, the element may include a powder of a reflector, scatterer or absorber. The powder may also be a powder of nanoparticles. Nanoparticles are particles that are invisible to the human eye. For example, for a magnetic sensor, the element may include a powder of magnetic and / or conductive nanoparticles, and for an optical sensor, the element may include a powder of reflective, scattering or absorbing nanoparticles.

[0039] The above-mentioned objects are also solved by a method for measuring force using a soft sensor arrangement according to the present invention, the method comprising the following steps: receiving a signal from a sensor when a deformable element at least partially extending between the sensor and an element acting on the same element is deformed due to the force to be measured; and estimating the intensity of the force from the received signal based on a predefined correlation between the value of the force and the value of the signal of the sensor.

[0040] The element is adapted to cause a physical signal at the sensor, which physical signal depends on the position and orientation of the element relative to the sensor. The physical signal may be a one-dimensional signal or a multidimensional signal. Furthermore, the physical signal may be a single one-shot, one-dimensional or multidimensional signal, or a multivariate sequence of one-dimensional or multidimensional signals, such as a time trajectory of one-dimensional or multidimensional signals. If the element changes its position and / or its orientation, the physical signal detected by the sensor undergoes a corresponding signal change.

[0041] Before an external force is applied to the sensor arrangement, the element is located at a first position relative to the sensor. The first position is defined by the extent of a deformable element arranged between the sensor and the element. The first position is consistent with a first signal measurement. When the deformable element is deformed by the external force, the element moves to a second position. If the deformable element is compressed, the second position is closer to the sensor than the first position. This positional change of the element changes the interaction of the element with the sensor and causes a change in the measurement taken by the sensor. Once the external force is released from the deformable element (for example, by releasing an object pressing against the deformable element), the deformable element returns to its initial shape, the element performs a joint movement back to the first position, and the sensor again determines the corresponding initial physical signal. If the deformable element is not compressed but expanded, the second position is further away from the sensor than the first position. This positional change of the element again changes the interaction of the element with the sensor and causes a change in the measurement taken by the sensor. Once the external force is released from the deformable element (e.g. by releasing the object pulling on the deformable element), the deformable element returns to its initial shape, the element performs a joint motion back to the first position, and the sensor once again determines the corresponding initial physical signal. In both cases, a lookup table or algorithm can be used to estimate the applied external force from the physical signal, as described above. Thus, there is no need to find an explicit analytical expression or mathematical model to express the relationship between the physical signal and the applied external force. Instead, machine learning (ML) methods can be used to sample the nonlinear stress-strain curve of the deformable element. Thus, machine learning (ML) can be applied to infer a correlation between the value of the force and the value of the signal of the sensor, which correlation is used to estimate the force if the signal of the sensor is given.

[0042] The above mentioned objects are also solved by a gripper according to the invention, comprising at least two robot fingers, wherein at least one of the at least two robot fingers comprises a soft sensor arrangement according to the invention. The robot finger may be a mechanical device, which may be adapted to apply a force to an object. If the gripper comprises two robot fingers opposite to each other, the two opposite robot fingers may also be referred to as a jaw. The two opposite robot fingers of the jaw may be complementary to each other in the sense that there is at least one common axis of symmetry of the two robot fingers constituting the jaw. However, a person skilled in the art understands that any number of robot fingers may be used.

[0043] For a gripper according to the invention, at least one of the at least two robot fingers of the gripper may comprise a single soft sensor arrangement, such that in this case, the other of the at least two robot fingers does not comprise a soft sensor arrangement. In this case, both robot fingers apply a clamping force to the clamped object, but only one robot finger is used to measure the clamping force. Redundancy in measuring the clamping force can be achieved by equipping more than one of the at least two robot fingers with a separate soft sensor arrangement according to the invention. For example, if two of the at least two robot fingers comprise a respective soft sensor arrangement, and if the clamping forces applied by the two robot fingers are collinear (i.e., clamping the object from both sides at a similar angle), the measured clamping forces of the two soft sensor arrangements show the same absolute value. Thus, the use of more than one soft sensor arrangement has the benefit of allowing averaging the measurements to achieve a higher precision when determining the force, or allowing avoiding force determination becoming impossible in the event that one soft sensor arrangement is defective.

[0044] In another preferred embodiment of the present invention, at least one soft sensor arrangement of the fixture can be removably attached to the corresponding at least one robot finger. In this context, removably means that the robot finger and the soft sensor arrangement can be detached from each other without damaging the soft sensor arrangement or the robot finger. If at least one soft sensor arrangement is removably attached to the corresponding robot finger, it is possible to replace the soft sensor arrangement with low effort and low cost. For example, at least one soft sensor arrangement can be attached to the corresponding robot finger by one or more screws, by glue, or using tape. It is also possible that the soft sensor arrangement is clamped to the corresponding robot finger. In this case, the soft sensor arrangement and the corresponding robot finger may include corresponding bearings, which are pushed and / or pulled by each other to attach the soft sensor arrangement to the corresponding robot finger.

[0045] In another preferred embodiment of the present invention, at least one soft sensor arrangement of the fixture can be monolithically integrated into at least one robot finger. In this case, the soft sensor arrangement and the corresponding robot finger of the fixture can, for example, be manufactured integrally. This means that the soft sensor arrangement and the corresponding robot finger can be manufactured as a single piece. For example, some components of the soft sensor arrangement can be assembled in one piece with some components of the robot finger. It is also possible that the soft sensor arrangement and the corresponding robot finger are initially manufactured as two separate pieces, which are then overmolded to be attached together to form a single piece. During overmolding, the two pieces can be heated so that a connection can be established between two molten areas of the two separate pieces, which, after cooling, constitutes a rigid link between the soft sensor arrangement and the corresponding robot finger.

[0046] The above mentioned objects are also solved by a method for operating a gripper arrangement according to the invention for gripping an object by means of a gripper comprising at least two robot fingers, wherein at least one robot finger comprises a soft sensor arrangement according to the invention. The method comprises: extending the distance between at least two robot fingers of the gripper until the distance between the at least two robot fingers is able to accommodate the object to be gripped; gripping the object by reducing the distance between the at least two robot fingers, thereby applying a force to the object, whereby a deformable element of the soft sensor arrangement is deformed; measuring the force applied to the object by the two robot fingers by the action of sensors on the elements, wherein the deformable element extends at least partially between the sensors and the elements; and controlling the movement of the at least two robot fingers based on the measurement. A feedback loop may be created between the measured force and the force applied to the object by the at least two robot fingers. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The following description and accompanying drawings set forth in detail certain illustrative aspects of the soft sensor arrangement, the fixture, and the corresponding two methods described above. However, these aspects are merely indicative of several of the various ways in which the principles of the various embodiments may be employed, and the described embodiments are intended to include all such aspects and their equivalents.

[0048] In the drawings, like reference numerals generally refer to like parts throughout the different drawings. The drawings are not necessarily drawn to scale. Instead, overall emphasis is placed on explaining the general principles of the invention.

[0049] In the following description, various embodiments of the present invention are described with reference to the following drawings:

[0050] Figure 1 shows a cross-sectional view of an embodiment example of a soft sensor arrangement according to the invention without any external force being applied;

[0051] Figure 2a shows the case where a linear external force is applied. Figure 1 A cross-sectional view of a soft sensor arrangement 100;

[0052] Figure 2b shows that when nonlinear external forces are applied, Figure 1 Cross-sectional view of soft sensor arrangement;

[0053] Figure 3 shows a cross-sectional view of another embodiment of a soft sensor arrangement according to the present invention featuring a mechanical stop having rounded edges and / or beveled edges;

[0054] Figure 4shows a cross-sectional view of another embodiment example of a soft sensor arrangement according to the present invention featuring a space for accommodating a deformed deformable element;

[0055] Figure 5 Shows Figure 1 A cross-sectional view of a soft sensor arrangement, wherein the sensor is a magnetic sensor;

[0056] Figure 6 Shows Figure 1 A cross-sectional view of a soft sensor arrangement, wherein the sensor is an optical sensor;

[0057] Figure 7 shows a cross-sectional view of a clamp according to an example of an embodiment of the present invention;

[0058] Figure 8 The deformable element is shown without deforming the object being held. Figure 7 a cross-sectional view of the fixture; and

[0059] Fig. 9 The method of holding an object while deforming the deformable element is shown. Figure 7 A cross-sectional view of the fixture. DETAILED DESCRIPTION

[0060] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced.

[0061] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0062] Figure 1A cross-sectional view of a soft sensor arrangement 100 according to an embodiment of the present invention is depicted. The soft sensor arrangement 100 includes a sensor 110, a deformable element 120, and an element 130 for interacting with the sensor 110. For example, the deformable element 120 may include at least one of the following: an elastomer, a polymer, a rubber, and a vulcanized rubber. The deformable element 120 may also include a flexible element, an elastic element, or a flexible structure. The flexible element or the flexible structure may be made of a metal. For example, the flexible element or the flexible structure may be made of a metal flexible beam. In the embodiment shown here, the element 130 is fully embedded in the deformable element 120. Fully embedded means that the deformable element 120 completely surrounds the element 130, which means that all surfaces of the element 130 are in contact with the deformable element 120. It can also be said that the element 130 is encapsulated by the material of the deformable element 120. The deformable element 120 can be deformed by applying an external force. The applied external force can cause the deformable element 120 to be compressed so that the distance between the element 130 and the sensor 110 changes. This change in distance can be detected by sensor 110. For example, if element 130 is a magnet and sensor 110 is a magnetic sensor, the reduction in the distance between element 130 and sensor 110 causes the sensor to detect a different magnetic field, such as a different magnetic field strength and / or orientation than before the deformation. Thus, based on the change in the measured physical units, it can be inferred how much deformable element 120 has deformed. However, those skilled in the art will note that other types of sensor 110 / element 130 combinations can also be used to measure the amount of distance that deformable element 120 has been compressed.

[0063] Each individual deformation of the deformable element 120 corresponds to a different applied external force, which in turn is associated with a corresponding physical measurement obtained by the sensor 110. Therefore, there is a correlation between the applied external force value and the corresponding measurement value of the sensor 110. This correlation can be determined during an initial calibration step of the sensor 110, or can be predetermined by knowing the bulk modulus and / or shear modulus of the deformable element 120. For example, the correlation itself can be established as a lookup table, including the external force value and its associated sensor reading. A model trained by machine learning can be used to establish the correlation between the applied external force value and the corresponding measurement value of the sensor 110. Those skilled in the art are also aware of other ways to establish the corresponding correlation, all of which are covered herein. Once the actual measurement of the sensor 110 is obtained, the lookup table can be used to infer an estimate for the external force. However, by knowing the bulk modulus and / or shear modulus of the deformable element 120, an algorithm can also be used that outputs the actual force applied relative to the deformation through a simple calculation. The algorithm can be a nonlinear model that defines the actual force as a nonlinear function of the measurement value of the sensor 110. The algorithm or correlation may be implemented inside an integrated circuit (IC) containing sensor 110, or outside an integrated circuit containing sensor 110, or partially inside an integrated circuit containing sensor 120 (e.g., for calculating the position of element 130 based on the sensor signal) and partially outside an integrated circuit containing sensor 110 (e.g., for inferring the force based on the displacement of element 130). Sensor 110 may be configured to provide dual sensing, which allows detection of linear forces as well as shear forces, such as a linear force in the direction of the external force and a shear force in one direction or two orthogonal directions in a plane perpendicular to the direction of the external force. The correlation or algorithm may provide a direct link between the applied external force value and the measured value of sensor 110. Alternatively, the correlation or algorithm may calculate the displacement of element 130 as an intermediate step. In this case, a first correlation or first algorithm determines the position of element 130 based on the measured value of sensor 110, and a second correlation or second algorithm determines the applied external force value based on the position of element 130. Thus, in this case, determining the position of element 130 acts as an intermediate step.

[0064] In the example shown, the soft sensor arrangement 110 further comprises a mechanical stop 140 that limits the deformation of the deformable element 120. Such a limitation of the maximum deformation of the deformable element 120 avoids the sensor 110 and / or the deformable element 120 from being damaged when the deformable element 120 is deformed. In the embodiment example shown here, the mechanical stop 140 at least partially surrounds the sensor 110. The gap 150 formed in the mechanical stop 140 holds the sensor 110 in a specific position within the mechanical stop 140. The sensor 110 can be fixed to the mechanical stop 140, or can be replaceably fixed to the mechanical stop 140. The latter allows the same mechanical stop 140 to be used with different sensor arrangements, for example, when the type of sensor 110 should be changed (for example to better adapt to changing environmental conditions or for repair and maintenance).

[0065] In the embodiment example shown here, the deformable element 120 is arranged in a gap or hole 150 in the mechanical stop 140. Thereby, a first end of the deformable element 120 contacts the sensor 110, while a second end of the deformable element 120, opposite to the first end, extends from the mechanical stop 140 through the gap or hole 150. A force will be applied to this second end, which will bring the second end closer to the sensor 110 (as can be seen in FIG. 2 ). In the embodiment example shown here, the element 130 embedded in the deformable element 120 has a distance d1 from the sensor 110, which is smaller than the distance d2 from the second end of the deformable element 120 to the sensor 110, but larger than the distance d3 from the end face of the mechanical stop 140 to the sensor 110.

[0066] In a non-limiting sense, the distance d1 of the element 130 from the sensor 110 may be 3 mm, the distance d2 of the second end of the deformable element 120 from the sensor may be 4 mm, and the distance d3 of the end face of the mechanical stop 140 from the sensor 110 may be 2.8 mm. Thus, the deformation of the deformable element may be limited to 1.2 mm by the action of the mechanical stop 140. However, it should also be contemplated that such deformation may generally be limited to less than 20%, or less than 30%, or less than 40% of the range of the deformable element 120 in the direction of application of the force. In the absence of an applied external force, the distance d1 of the element 130 from the sensor 110 may also be less than the distance d3 of the end face of the mechanical stop 140 from the sensor 110. Those skilled in the art understand that these dimensions are named for illustrative purposes only and should not be construed as limiting if not explicitly mentioned.

[0067] Figure 2a Shows Figure 1Cross-sectional view of the soft sensor arrangement 100 under application of an external force ("pressure"). The applied external force may be uniform, i.e. constant over the surface to which the force is applied. However, the applied external force may also be non-uniform, i.e. varying over the surface to which the force is applied. This variation of the force over the surface to which the force is applied may be linear or non-linear. In other words, each point on the surface to which the force is applied may be assigned a different force value which is related to adjacent force values ​​according to a linear or non-linear relationship. In the example shown, the external force is uniform over the surface of the deformable element 120 and is applied perpendicularly to the surface of the sensor 110. The applied external force compresses the deformable element 120. This reduces the distance d2 of the second end of the deformable element relative to the sensor 110 to a shorter distance d 2’ Due to the fact that the element 130 is embedded in the deformable element 120, the distance d1 from the element 130 to the sensor 110 is also reduced to a shorter distance d 1’ .

[0068] The sensor 110 is configured to detect the distance d1 to d by interacting with the element 130. 1’ If sensor 110 is a magnetic sensor and element 130 is a magnet, a lower distance between sensor 110 and element 130 causes sensor 110 to detect a higher magnetic field strength, since magnetic field strength is proportional to distance. This change in magnetic field strength allows the force applied to deformable element 120 to be derived. In some cases, if sensor 110 is a magnetic sensor, sensor 110 may detect a change in the orientation of the magnetic field strength vector (i.e., a change in one or more angles assigned to the magnetic field vector) in addition to or instead of the magnetic field strength. In this case, the magnetic sensor may be located at an offset relative to the axis of the magnet. Although only one-dimensional distance measurements, and the resulting vertically applied force, are described herein, those skilled in the art will note that element 130 may also be used as a Figure 2b Tilt at an angle as shown in FIG.

[0069] exist Figure 2b In the embodiment of FIG. 1 , the external force (“pressure”) is applied uniformly but not perpendicularly to the surface of the sensor 110. Thus, the applied external force causes the deformable element 120 to deform in a direction that is not perpendicular to the surface of the sensor 110. This causes the distance d1 of the element 130 from the sensor 110 to be changed in a non-homogeneous manner. For example, the upper end of the element 130 moves to a larger distance d 1’ , but the lower end of element 130 moves to a lower distance d 1” . Since the distance d 1’ and d 1”It is different in the case where a non-linear force is applied, so that the element 130 is tilted by a non-zero angle α relative to the sensor 110. Thus, in the case of a non-vertical external force, the element 130 is not only translated, but also rotated. The sensor 110 is adapted to detect the change of the angle α by acting with the element 130. If the sensor 110 is a magnetic sensor and the element 130 is a magnet, the different angles α between the sensor 110 and the element 130 cause the sensor 110 to detect different magnetic fields, because the orientation of the magnetic field lines of the magnet 130 relative to the sensor 110 has been changed. It can also be said that the rotation of the element 130 by the angle α causes the sensor 110 to sense the three-dimensional magnetic field from the rotation of the element 130. Under rotation, the absolute magnetic field strength does not change, but the orientation of the magnetic field vector in space is changed. Therefore, compared with the non-rotation of the element 130, the sensor 110 senses a different magnetic flux, because the projection of the magnetic field vector to the surface on which the sensor 110 measures the magnetic flux is different. The change in the measured magnetic flux allows the change of the position of the element 130 to be inferred. The positional change of element 130 is uniquely linked to the force applied to deformable element 120. Thus, if a non-perpendicular force is applied to deformable element 120, the rotation of element 130 can be used to determine the force applied to deformable element 120.

[0070] When an external force is applied to the deformable element 120, such as Figure 1 , Figure 2a and Figure 2b The mechanical stop 140 shown in FIG. 1 limits the deformation of the deformable element 120. This has the effect that the distance d of the second end of the deformable element 120 2’ The limited minimum distance d3, which is given by the distance between the end of the mechanical stop 140 facing away from the sensor 110 and the sensor 110, is never impaired. By limiting the deformation of the deformable element 120, a minimum distance between the element 130 and the sensor 110 is also defined, since the movement of the element 130 is coupled to the movement of the compression of the deformable element 120. This has the advantage that the element 130 does not come too close to the sensor 110, which could cause damage to the sensor 110 or could impair the sensitivity of the sensor 110, for example due to an overload of the sensor 110.

[0071] Furthermore, any unrestricted deformation of the deformable element 120 may also risk damaging the deformable element 120 itself. For example, by overdeforming the deformable element 120, the internal joints of the deformable element may be broken, causing the deformable element to tear. This risk is even greater when the element 130 is made of a material that is more rigid than the deformable element itself. This may cause damage to the deformable element 120, which may be prevented by limiting the deformation of the deformable element 120.

[0072] exist Figure 1 , Figure 2a and Figure 3 In the example of embodiment shown in b, the gap, hole or recess 150 is dimensioned in a certain manner to accommodate the deformable element 120 and the element 130 in compression.

[0073] The size of the recess 150 may be designed so that the deformable element 120 can move into the recess 150, but the element 130 cannot move into the recess 150. In this case, when a critical external force is applied to the deformable element 120, the element 130 is pressed against the mechanical stopper 140, but even if the external force is further increased to exceed the critical external force, the element 130 does not enter the recess 150. Instead, any excess force of the external force relative to the critical external force is then directly conducted to the mechanical stopper 140. It can be said that in this case, the mechanical stopper 140 and the element 130 act together to ensure that the element 130 does not contact the sensor 110, or the deformable element 120 is not compressed too strongly relative to the sensor 110.

[0074] Optionally, the size of the recess 150 of the soft sensor arrangement 100 can also be designed to at least partially accommodate the element 130. Therefore, by applying an external force to the element 130, the element 130 can at least partially enter the recess 150. If at least a portion of the deformable element 120 is located between the element 130 and the object pressed against the deformable element 120, this portion of the deformable element 120 can also be at least partially compressed into the recess 150. Once the critical force is applied to the object, the object touches the mechanical stop 140. At this point, any applied external force exceeding the critical force is conducted to the mechanical stop 140. In this way, the recess 150 not only limits the strain on the portion of the deformable element 120 located between the sensor 110 and the element 130 (i.e., facing the sensor 110), but also potentially limits the strain applied on the portion of the deformable element 120 located between the element 130 and the object (i.e., facing the object). In other words, the mechanical stop 140 may define a minimum distance from the element 130 to the sensor 110 and a minimum volume that can be occupied by the deformed deformable element 120 .

[0075] Figure 3A cross-sectional view of a soft sensor arrangement featuring a mechanical stopper 140 having two rounded edges 345a, 345b according to another embodiment example of the present invention is shown. If the shear modulus of the deformable element 120 is non-zero, the applied external force causes deformation of the deformable element 120 in at least one direction orthogonal to the direction of the applied external force. In other words, the deformable element 120 is quenched and occupies excess volume in at least one orthogonal direction compared to the undeformed (relaxed) state of the deformable element 120. In this case, if the mechanical stopper 140 would feature a sharp edge facing the deformable element 120, the deformed deformable element 120 (and in particular the portion of the deformed deformable element 120 that occupies the excess volume) may be easily damaged. As a remedial measure, rounding and / or beveling the edge 345 of the mechanical stop 140 facing the deformable element 120 creates a volume inside the mechanical stop 140 that is suitable for accommodating at least excess volume of the deformable element 120 caused by shear deformation of the deformable element 120.

[0076] Figure 4 A cross-sectional view of a soft sensor arrangement featuring two spaces 445a, 445b for accommodating material of a deformed deformable element 120 according to another example of an embodiment of the present invention is shown. In the example shown here, the two spaces 445 have the form of a cube, but in principle any other geometric shape suitable for accommodating an excess volume (not shown) of the deformable element 120 may also be adopted. The two shown spaces 445 may be defined by one or more distances d4 between the starting surface of the mechanical stop 140 and the sensor 110 and / or by one or more distances d5 between the axial surface of the mechanical stop 140 and the adjacent surface of the undeformed deformable element 120. Thus, the axial surface of the mechanical stop 140 is a surface of the mechanical stop 140 that is perpendicular to the surface of the sensor 110, and the starting surface of the mechanical stop 140 is a surface of the mechanical stop 140 that is parallel to the surface of the sensor 110. The surface of the sensor 110, the adjacent surface of the deformable element 120, the axial surface, and the starting surface of the mechanical stop 140 form Figure 4140 (cross-section, 4 boundaries for the cube example shown). It can also be said that, viewed from the sensor 110, the space 445 ends at the starting surface of the mechanical stop 140 and is bounded either to the left or to the right by the axial surface of the mechanical stop 150. One or more edges of one or more spaces 445 can be rounded and / or beveled. In one example, at least one space 445 can extend to cover the entire height of the deformable element 120, which height is measured in a direction perpendicular to the surface of the sensor 110 (not shown). It can also be said that, in this case, at least one space 445 forms a buffer volume between the undeformed deformable element 120 and the soft sensor arrangement. The deformable element 120 is then free to move in the direction of the buffer volume formed by the at least one space 445. Thereby, at least one space 445 can be formed so that the deformable element 120 is free to move in at least one direction parallel to the surface of the sensor 110. Specifically, at least one space 445 may be formed such that the deformable element 120 is free to move in all directions parallel to the surface of the sensor 110, or is free to move in only one direction parallel to the surface of the sensor. It is also possible that the mechanical stopper 140 does not restrict the movement of the deformable element 120 in at least one direction parallel to the surface of the sensor 110, so that the deformable element 120 is free to move in at least one direction parallel to the surface of the sensor 110. If the deformable element 120 is free to move only in one direction parallel to the surface of the sensor 110, this direction may coincide with the direction of gravity. This has the technical advantage that in addition to the force applied by the object to the deformable element 120, the gravity acting on the object in contact with the deformable element 120 may also be measured. In this way, the clamping force acting on the object and the weight of the object may be determined using the same sensor 110.

[0077] Figure 5 A soft sensor arrangement is shown, wherein the sensor 110 and the element 130 are a passive or active magnetic sensor 515, and a magnetic field emitting element or target, respectively. Figure 5 In FIG. 1 , the magnetization direction of the element 130 is parallel to the surface of the sensor 110. However, a person skilled in the art will appreciate that any orientation of the magnetization direction of the element 130 relative to the sensor 110 may be chosen.

[0078] Passive magnetic sensors respond to external magnetic fields. Such external magnetic fields can be emitted by an element. Thus, the element can be a permanent magnet, or a coil and / or wire through which current flows. The current can be a DC or AC current, so that the wire and / or coil generates a constant electromagnetic field or a time-varying electromagnetic field. The passive magnetic sensor may include at least one sensor element capable of measuring at least one property of a magnetic field emitted from the element 130. The at least one property measured may be, for example, magnetic field intensity. At least one sensor element may be a Hall plate or a magnetoresistive sensor. At least one sensor element may also include a fluxgate sensor, a magnetoresistive (MI) sensor. The Hall plate may be a horizontal Hall plate with a maximum sensitivity axis perpendicular to the substrate, or a vertical Hall plate with a maximum sensitivity axis parallel to the substrate. The Hall plate may be made of silicon, for example, integrated in a CMOS substrate. The Hall plate may also be made of a semiconductor compound (e.g., a III-V semiconductor material such as GaAs), which results in improved sensitivity compared to silicon.

[0079] When deformable element 120 is deformed, at least one measured property of the magnetic field emanating from element 130 allows a change in the distance of element 130 to sensor 110 to be determined, which in turn allows a force applied to deformable element 120 to be determined.

[0080] In an example, the passive magnetic sensor may include three sensor elements spaced apart at angles in multiples of 120°. Each of the three sensor elements measures B parallel to the sensor surface. x The magnetic field component, and the B perpendicular to the sensor surface z Thus, such a passive magnetic sensor can measure six magnetic field components of the magnetic field generated by element 130, which at the first sensor position can be referred to as (B x1 , B z1 ), at the second sensor position it can be called (B x2 , B z2 ), and at the third sensor position can be referred to as (B x3 , B z3 ). Element 130 is preferably located substantially above the common center of the three sensor elements. By means of these sensor elements, not only the distance of element 130 from sensor 110 can be determined, but also its rotation, in order to perform non-vertical force measurements.

[0081] In an example, the passive magnetic sensor may include four sensor elements angularly spaced at different angles. These angles may be multiples of 90°, but may also be selected individually for each of the four sensor elements. Each of the four sensor elements measures B parallel to the sensor surface. x The magnetic field component, and the B perpendicular to the sensor surfacez Thus, such a passive magnetic sensor can measure eight magnetic field components of the magnetic field generated by element 130, which at the first sensor position can be referred to as B x1 and B z1 , at the second sensor location can be referred to as B x2 and B z2 , at the third sensor position can be called B x3 and B z3 , and at the fourth sensor position may be referred to as B x4 and B z4 .

[0082] In a more general embodiment of the claimed invention, a passive magnetic sensor may include a variable number N of angularly spaced sensor elements, wherein each individual angle is associated with a respective sensor element of the N sensor elements. Each of the sensor elements measures B parallel to the sensor surface. x The magnetic field component, and the B perpendicular to the sensor surface z Thus, the passive magnetic sensor can measure 2×N magnetic field components of the magnetic field generated by the element 130, which can be referred to as B at the position of the i-th sensor. xi and B zi , where N is the total number of sensor elements. For the above-mentioned embodiment with N=3 sensor elements, even in the case of any N, the element 130 is preferably located substantially above the common center of the N sensor elements. With these N sensor elements, in the case of non-vertical force measurement, not only the distance of the element 130 from the sensor 110 can be determined, but also its rotation.

[0083] In contrast, an active magnetic sensor creates or changes a magnetic field on its own, which is then changed or influenced by a target. An active magnetic sensor may include at least one sensor element that emits a magnetic field and at least one sensor element that measures the change in the magnetic field generated by the element. However, an active magnetic sensor may also include at least one sensor element that performs both: emitting a magnetic field and measuring the change in the magnetic field. In this case, the sensor element may be adapted to operate as a sensor element that emits a magnetic field during a first time interval and as a sensor element that measures the change in the magnetic field during a second time interval. For example, an active magnetic sensor may include a coil or wire that radiates an electromagnetic wave having a time-varying magnetic field component during a first time interval and captures the electromagnetic wave during a second time interval. Thus, the change in the emitted magnetic field may be caused by the target, for example via induction. Thus, the target itself may be non-magnetic. For example, the target may be designed as a planar structure of a metal, which is characterized by a wire in a preferred direction in space. Such a target will then change at least one property of the magnetic field emitted from the active magnetic sensor, and the change in at least one property of the emitted magnetic field may then be measured. When the deformable element 120 is deformed, a change in at least one property of the emitted magnetic field then allows determining a change in the distance between the target and the sensor 110 , since the modification of the emitted magnetic field is proportional to the distance between the element 130 and the sensor 110 .

[0084] When the spatial dimensions of element 130 (e.g., of a magnet or target) are smaller than the spatial dimensions of sensor 110 (e.g., of a passive magnetic sensor or an active magnetic sensor), in particular when the ratio is equal to or greater than 1.5 (e.g., between 1.5 and 3), shear stress can be advantageously measured with high accuracy.

[0085] Figure 6 A cross-sectional view of a soft sensor arrangement is shown, wherein the sensor 110 is an optical sensor 610. The optical sensor 610 measures at least one physical property of a light beam and outputs at least one physical signal proportional to the at least one physical property. In the embodiment example shown here, the element 130 at least partially reflects incident light 630 falling on the element 130, so that return light 640 emitted from the element 130 can be measured by the optical sensor 610. Figure 6 , the angles at which incident light 630 and returned light 640 appear are related according to the law of reflection (Snell's law). In the example shown, incident light 630 is light emitted by optical transmitter 620 included in sensor 110. However, incident light 630 may also be ambient light, or light generated by an external light source (not shown) that is not part of sensor 110. Various ways of creating light that falls on element 130 may be imagined by those skilled in the art.

[0086] For example, the physical property measured by the optical sensor 610 may be the intensity of the light 640 returned by the element 130. The intensity of the returned light 640 measured by the optical sensor 610 varies depending on the position of the element 130 relative to the sensor 110. For example, if the element 130 is far from the sensor 110, a relatively low intensity is registered by the optical sensor 610 because the returned light 640 propagates over a relatively large solid angle, so that a relatively small portion of the returned light 640 strikes the surface of the optical sensor 610. In contrast, if the element 130 is close to the sensor 110, the returned light 640 propagates over a smaller solid angle and a larger portion of the returned light 640 strikes the surface of the optical sensor 610. Therefore, a higher intensity is registered by the optical sensor 610. Therefore, as described above, the registered light intensity allows conclusions to be drawn about the position of the element 130, which in turn is uniquely linked to the external force applied to the deformable element 120.

[0087] Figure 7 A cross-sectional view of a fixture 700 is shown with an example of an embodiment of two sensor arrangements attached to the fixture 700. A fixture is a mechatronic device for applying a force and a corresponding reaction force to an object in order to manipulate the position and / or orientation of the object. To this end, Figure 7 The fixture 700 shown in the figure comprises two robot fingers 710a, 710b. The robot fingers 710a, 710b are adapted to transmit desired forces and reaction forces to the object. In the non-limiting example shown here, the fixture 700 comprises two robot fingers 710a, 710b, each robot finger comprising a soft sensor arrangement. However, it is also possible that only one of the two robot fingers comprises a soft sensor arrangement, or that the fixture comprises more than two robot fingers, each robot finger having or without a soft sensor arrangement (not shown). The two soft sensor arrangements shown are connected by means of screws ( Figure 7) are removably attached to the corresponding robot finger 710a, 710b. However, each soft sensor arrangement can also be monolithically integrated with the corresponding robot finger 710a, 710b (not shown). Those skilled in the art understand when to use which of the aforementioned alternatives. As described above, removably attached means attached by some means: when the attachment of the soft sensor arrangement or the corresponding robot finger 710 is released, the means does not cause damage to them. This can include attachments containing screws (shown), glue, or adhesive tape. Monolithic integration means that the mechanical stop 140a and the corresponding robot finger 710a are either manufactured as one piece or manufactured from one or more separate pieces that are overmolded to form the shown portion of the fixture 700. Those skilled in the art will appreciate that a particular application for the gripper may require more than two robotic fingers 710 to be included in the gripper 700, or that one soft sensor arrangement included in the gripper 700 may be sufficient for a simple force sensing application that measures only one of the force or reaction force applied by the gripper 700 (not shown).

[0088] Figure 8 A cross-sectional view of a gripper 700 holding an object 810, but without deformation of the deformable elements 130, is shown. The object 810 is shown between a first soft sensor arrangement of a first robot finger 710a attached to the gripper 700 and a second soft sensor arrangement of a second robot finger 710b attached to the gripper 700. In the embodiment shown here, the robot fingers 710a, 710b have been retracted so that the surfaces of the deformable elements 120a, 120b of the two soft sensor arrangements touch the surface of the object 810. However, in the embodiment example shown, the robot fingers 710a, 710b have not yet applied a force or a reaction force to the object 810. Thus, in this figure, the deformable elements 120a, 120b of the soft sensor arrangement are still not deformed, and the respective sensors 110a, 110b of the soft sensor arrangement measure physical values ​​corresponding to the initial position and / or orientation of the elements 130a, 130b embedded in the deformable elements 120a, 120b. It can also be said that the embodiment example shown here shows the situation just before the clamp 700 exerts a clamping effect on the object 810, because friction between the outer surfaces of the deformable elements 120a, 120b facing the object 810 and the corresponding surfaces of the object 810 has not yet occurred.

[0089] Fig. 9 1 shows a cross-sectional view of the clamp 700 holding the object 810 when deforming the deformable element 130. In the embodiment example shown here, Figure 8Compared to the two robot fingers 710a, 710b of the gripper 700, they have been further retracted. Therefore, the first robot finger 710a applies a first force to the object 810, and the second robot finger 710b applies a second force to the object 810. In the example shown, the first force and the second force are collinear, but opposite to each other. As a result, the deformable elements 120a, 120b of the two soft sensor arrangements 100 are deformed and move relative to each other. Figure 8 Compared to the position and / or orientation of the initial shape of the undeformed deformable elements 120a, 120b shown in FIG, the corresponding elements 130a, 130b change their position and / or orientation. Thus, both sensors 110a, 110b measure the same Figure 8 The initial positions and / or orientations of the elements 130a, 130b shown in FIG. 1 correspond to different physical values.

[0090] Using the above method, the measured physical value can be mapped to an estimated value for the applied external force. In more detail, the physical value measured by the first sensor 110a can be mapped to a first estimated force value for the first force, and the physical value measured by the second sensor 110b can be mapped to a second estimated force value for the second force. The first estimated force value and the second estimated force value are redundant and can therefore be averaged to obtain a composite force estimate with higher accuracy. In addition, if the corresponding sensor 110a, 110b fails, one of the first estimated force value and the second estimated force value can replace the other.

[0091] Specifically, the estimated force value may be a multi-axis force value. Therefore, the estimated force value may include not only the force applied to the object 810 by the robot fingers 710a, 710b, but also the gravity of the object 810. Therefore, the first force and the second force applied to the object 810 by the robot fingers 710a, 710b may be controlled as a function of the estimated force value. Specifically, the first force and the second force applied by the robot fingers 710a, 710b may depend on the gravity of the object 810 included in the estimated force value. For example, for a higher gravity of the object 810 (i.e., for an object 810 having a heavier mass), the first force and the second force applied to the object 810 by the robot fingers 710a, 710b may be set higher. Accordingly, for an object 810 having a lighter mass, the first force and the second force applied to the object 810 by the robot fingers 710, 710b may be set lower. Thus, a feedback loop may be created between the first and second forces applied by the robot fingers 710a, 710b and the measured gravity of the object 810. Furthermore, the first and second forces applied by the robot fingers 710a, 710b to the object 810 may be limited to grip the object 810 less strongly.

[0092] Thereby, the clamp 700 comprising at least one soft sensor arrangement 100 according to the present invention is able to dynamically adapt the clamping force to the mass of the clamped object without exposing the object 810 itself to too strong deformations and while still ensuring adequate clamping of the object 810. This results in a safe clamping without damaging the object or letting it fall.

[0093] What has been described above includes examples of one or more embodiments. Of course, for the purpose of describing the aforementioned embodiments, it is not possible to describe every conceivable combination of components or methods, but one of ordinary skill in the art will recognize that many further combinations and permutations of the various embodiments are possible. Therefore, the described embodiments are intended to encompass all such changes, modifications and variations that fall within the spirit and scope of the appended claims.

[0094] abbreviation

[0095] 100 Soft Sensor Arrangement

[0096] 110 Sensors

[0097] 120 Deformable Element

[0098] 130 Components

[0099] 140 Mechanical stop

[0100] 150 Clearance

[0101] 345 Edge

[0102] 445 Space

[0103] 515 Passive Magnetic Sensor

[0104] 610 Optical Receiver

[0105] 620 Optical Transmitter

[0106] 700 clamp

[0107] 710 Robot Finger

[0108] 810 objects

Claims

1. A soft sensor arrangement (100) for measuring force, the soft sensor arrangement (100) comprising: Sensor (110); a deformable element (120), wherein the deformable element (120) is deformable due to the force; and An element (130) for interacting with the sensor (110) for measuring the force by deformation of the deformable element (120), wherein the deformable element (120) extends at least partially between the sensor (110) and the element (130).

2. The soft sensor arrangement (100) according to claim 1, further comprising: A mechanical stop (140), wherein the mechanical stop (140) limits the deformation of the deformable element (120).

3. The soft sensor arrangement (100) according to claim 2, wherein: The mechanical stop (140) includes a gap (150) through which the deformable element (120) at least partially extends.

4. The soft sensor arrangement (100) according to claim 3, wherein: The gap (150) is sized to at least partially accommodate the element (130).

5. The soft sensor arrangement (100) according to any one of claims 2 to 4, wherein: At least one edge (345a, 345b) of the mechanical stop (140) facing the deformable element (120) is beveled and / or rounded.

6. The soft sensor arrangement (100) according to any one of claims 2 to 5, wherein: The distance between the mechanical stop (140) and the sensor (110) defines a space (445a, 445b) into which the deformable element (120) can deform when the force is applied.

7. The soft sensor arrangement (100) according to any one of claims 1 to 6, wherein: The sensor (110) is a passive magnetic sensor (515) and the element (130) is a magnetic field emitting element, such as a permanent magnet.

8. The soft sensor arrangement (100) according to any one of claims 1 to 6, wherein: The sensor (110) is an active magnetic sensor and the element (130) is a target.

9. The soft sensor arrangement (100) according to any one of claims 1 to 6, wherein: The sensor (110) includes an optical receiver (610) that detects light (640), wherein the detected light (640) is light emitted, reflected, or scattered back from the element (130).

10. The soft sensor arrangement (100) according to any one of claims 1 to 9, wherein: The element (130) is embedded in the deformable element (120).

11. The soft sensor arrangement (100) according to any one of claims 1 to 10, wherein: The sensor (110) includes a semiconductor package embedding an integrated circuit (IC).

12. A method of measuring force using a soft sensor arrangement (100), the method comprising: receiving a signal from the sensor (110) when a deformable element (120) extending at least partially between the sensor (110) and the element (130) is deformed by the force; as well as The intensity of the force is estimated from the received signal based on a predefined correlation between the value of the force and the value of the signal of the sensor (110).

13. A gripper (700) having at least two robot fingers (710a, 710b), wherein: At least one of the at least two robot fingers (710a, 710b) comprises a soft sensor arrangement (100) according to any one of claims 1 to 10.

14. The clamp (700) according to claim 13, wherein: At least one sensor arrangement (100) is removably attached to the respective at least one robot finger (710a, 710b), or wherein the at least one sensor arrangement (100) is monolithically integrated into the at least one robot finger (710a, 710b).

15. A method for operating a gripper (700) for gripping an object (810), the gripper (700) comprising at least two robot fingers (710a, 710b), wherein: At least one robot finger (710a, 710b) comprises a soft sensor arrangement (100), the method comprising: Extending the distance between the at least two robot fingers (710a, 710b) of the gripper (700) until the distance between the at least two robot fingers (710a, 710b) can accommodate the object (810) to be gripped; gripping the object (810) by reducing the distance between the at least two robot fingers (710a, 710b), thereby applying a force to the object (810), whereby the deformable element (120) of the soft sensor arrangement (100) is deformed; measuring the force applied by the two robot fingers (710a, 710b) to the object (810) by the action of a sensor on an element (130), wherein the deformable element (120) extends at least partially between the sensor (110) and the element (130); and Movement of the at least two robotic fingers (710a, 710b) is controlled based on the force measurement.

Images