Soft Force Sensor

Abstract

A soft sensor mechanism for measuring force is presented. The soft sensor mechanism includes a sensor, a deformable element configured to be deformable by the force, and an element (sensor reaction element) that reacts to the sensor to measure the force by the deformation of the deformable element. At least a part of the deformable element extends between the sensor and the sensor reaction element. During operation, when the deformable element (130) of which at least a part extends between the sensor and the sensor reaction element is deformed by the force, the soft sensor mechanism receives a signal from the sensor and estimates the strength 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. Further, a gripping device including at least two robot fingers is also disclosed. At least one of the at least two robot fingers of the gripping device includes the soft sensor mechanism according to the present invention. The operation of the gripping device is performed by: widening the distance between the at least two robot fingers until the object to be gripped fits within the distance between the at least two robot fingers; gripping the object by narrowing the distance between the at least two robot fingers, thereby applying a force to the object; measuring the force applied to the object by the at least two robot fingers by the reaction of the sensor to the sensor reaction element; and controlling the movement of the at least two robot fingers based on the measured value of the force.

Description

Technical Field

[0001] The present invention relates to a soft force sensing mechanism and a method for measuring force using the same.

Background Art

[0002] A force sensing sensor returns an electronic signal proportional to the mechanical force applied to the sensor. In other words, a force sensing sensor can be said to convert the magnitude of the applied force into an electronic signal correlated therewith. The forces measured by a force sensing sensor can be mechanical quantities such as tension, pressure, mass, torque, strain, and internal stress. Nowadays, force sensing sensors have become essential core components for power equipment, engineering machinery, various machine tools, and industrial automation systems.

[0003] For example, by using an existing force sensing sensor, it is possible to measure in real time the force applied to a workpiece during an automatic manufacturing process and control the force applied to the workpiece. Using this method, the force load applied to the workpiece during the manufacturing process can be controlled and potentially limited. This is particularly important when the workpiece is delicate. Today, force sensing sensors are also used in scenarios where goods are automatically sorted, stored, and packaged.

[0004] Force sensors are used in all fields to control the force load applied to an object. Force sensors are often used together with multi-axis robotic devices to move an object, position an object, or hold an object at a desired position for a desired period of time. Examples of multi-axis robotic devices include gripping devices. A gripping device is a mechatronics device that holds an object by applying a force and a corresponding reaction force to the object. By applying the force and the reaction force, the object is pressed against each part of the gripping device, and the object comes into contact with each part of the gripping device. Due to this contact, friction proportional to the applied force and reaction force is generated between each part of the gripping device and the object. And if this frictional force is greater than the gravity of the object being gripped, the object will be stably held by the gripping device.

[0005] Regarding the above-mentioned type of gripping device, for example, it is described in Patent Document 1. The gripping device described in Patent Document 1 includes a gripping base, a sensor plate attached to the gripping base, at least two gripper jaws, and a one-dimensional force sensor disposed between a gripping plate carrier that holds the gripper jaws and the sensor plate. Thereby, the one-dimensional force sensor can measure the compressive force applied between the sensor plate and the gripping device plate carrier.

[0006] However, the sensors described in the prior art documents, and thus the gripping devices, had the problem that they could not measure the force applied to an object with sufficient accuracy. Therefore, there was a risk that the applied force was too strong or too weak and the grip was lost, resulting in damage to the object being gripped.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, since it is necessary to prevent the applied force from becoming too strong or too weak, there is a need to measure force with high precision. In addition, since sensors used for very high-precision measurements are also very fragile sensors, it is also important to protect each sensor mechanism from damage.

Means for Solving the Problems

[0009] The above object can be solved by the soft sensor mechanism according to the present invention. The soft sensor mechanism according to the present invention includes a sensor, a deformable element, and a sensor reaction element. The sensor reaction element may be composed of a single element or a plurality of elements. The deformable element can be configured to be deformable, and at least a part of the deformable element can extend between the sensor and the sensor reaction element. That an element is "deformable" means that when an external force acts, the shape and volume of the element change. Therefore, "deformable" also means that when the external force acting on the element disappears, the element returns to its original shape and volume.

[0010] During operation, a force acts on the sensor mechanism from an object. As a result, either the sensor reaction element or the deformable element comes into contact with the object. This contact may be direct or indirect. Therefore, the sensor reaction element or the deformable element can contact the object directly or indirectly. In the case of direct contact, at least one surface of the sensor reaction element or the deformable element touches at least one surface of the object. In the case of indirect contact, at least some other part is interposed between the two contact surfaces. The intervening substance for the sensor reaction element may be a deformable element. In that case, the sensor reaction element contacts the object indirectly, but the deformable element contacts the object directly. In this case, it can also be said that the sensor reaction element is embedded in the deformable element. Therefore, the sensor reaction element can be partially or completely embedded in the deformable element. When the sensor reaction element is completely embedded in the deformable element, all surfaces of the sensor reaction element are in contact with the deformable element. It can also be said that the material of the deformable element surrounds the sensor reaction element. Conversely, when the deformable element is in indirect contact with the object, the sensor reaction element may be in direct contact with the object. However, this also includes the case where the sensor reaction element and the deformable element only contact the object indirectly, but some other part is in direct contact with the object. For example, there may be a case where the sensor reaction element is embedded in a plastic piece and this plastic piece is in contact with the deformable element. In another example, it is the same in that the plastic piece is made to contact the deformable element and the object, but the sensor reaction element can be embedded in the deformable element or the sensor reaction element can be made to contact the deformable element and the plastic piece. In these three cases, the object is in direct contact with the plastic piece but not in direct contact with the sensor reaction element or the deformable element.

[0011] The deformable element has at least a part thereof extending between the sensor and the sensor reaction element, or since the deformable element surrounds the sensor reaction element, the sensor reaction element is held in a specific relative position with respect to the sensor by the deformable element. This position can be defined as the first position of the sensor reaction element with respect to the sensor. In other words, it can also be said that the sensor reaction element is held at a specific distance from the sensor by the deformable element. When the deformable element deforms, in conjunction therewith, the sensor reaction element also moves in the direction in which the deformable element deforms. If this deformation is compression, the distance from the sensor reaction element to the sensor becomes shorter, and conversely if this deformation is elongation, the distance from the sensor reaction element to the sensor becomes longer.

[0012] That the deformable element "deforms" means that at least one spatial extent of the deformable element in at least one spatial dimension changes. Therefore, the deformable element of the sensor mechanism can have "softness" in the sense of being deformable. Such deformability, specifically, how much the deformable element can deform 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 when an external force is removed. Thus, when the external force is removed, the deformable element can return to its initial shape. Therefore, the deformable element can also be called a flexible element or an elastic element. In another example, the deformable element can be an elastomer. Usually, an elastomer is formed by monomers being bonded by weak intermolecular forces. Since the intermolecular forces of the chemical elements of the elastomer are weak, the structure of the compound can be changed without causing breakage of covalent bonds or by breaking only a part of the covalent bonds. And this property makes the elastomer a material having both viscosity and elasticity. Therefore, the elastomer can be deformed by an external force.

[0013] When the deformable element deforms, the sensor reaction element moves to a second position different from the first position. When the deformable element is compressed, the second position of the sensor reaction element is closer to the sensor than the first position of the sensor reaction element. On the other hand, when a tensile force is applied, the second position of the sensor reaction element is farther from the sensor than the first position. Then, the sensor of the sensor mechanism can detect such a change in position by reacting to the sensor reaction element. When the sensor reaction element reacts to the sensor, the measured value of the sensor is affected by the sensor reaction element. In other words, a coupling occurs between the sensor reaction element and the sensor due to a physical action peculiar to the sensor and the sensor reaction element. This coupling between the sensor reaction element and the sensor changes depending on the relative position of the sensor reaction element with respect to the sensor. Also, since such a coupling changes depending on the position, it can be said that the measured value of the sensor is a unique function of the relative position of the sensor reaction element with respect to the sensor. In this sense, the sensor used in the sensor mechanism can be said to be a distance measuring sensor. Such a sensor returns an electronic signal proportional to the relative position of the sensor reaction element with respect to the sensor.

[0014] In a state where no external force is applied to the sensor mechanism, the deformable element does not deform, and the sensor reaction element is located at a first position relative to the sensor. Therefore, the sensor can return a first signal corresponding to a measurement value indicating that the force is zero. On the other hand, when a finite external force is applied to the sensor reaction element, the deformable element deforms, and the sensor reaction element moves to a second position different from the first position. Due to the relative position of the sensor reaction element with respect to the sensor becoming the second position, the signal of the sensor also becomes a second signal corresponding to the applied external force. And since the first signal and the second signal are uniquely associated with the applied external force respectively by mapping, the applied external force can be specified from the measured distance. In other words, the force applied to the sensor mechanism can be measured by the amount of displacement of the sensor reaction element that occurs when the deformable element is deformed by the force applied to the sensor mechanism. Since the change in the interaction between the sensor reaction element and the sensor can be measured with high precision, it becomes possible to reliably perform high-precision measurement of the applied force. In other words, it becomes possible to infer the external stimulus that caused the variation, that is, the applied external force, from the variation in the influence exerted by the sensor reaction element on the sensor. For example, as described above, the displacement of the sensor reaction element with respect to the sensor can be sensed by the sensor.

[0015] In this way, the soft sensor mechanism according to the present invention realizes accurate force measurement for the first time through measurement of the deformation amount of the deformable element. Also, in this indirect force measurement, since the applied force is measured by applying the applied force to the deformable element to change the stimulus from the sensor reaction element to the sensor, it becomes possible to measure the applied force with a high granularity.

[0016] In a preferred embodiment of the present invention, another deformable element is brought into contact with the deformable element, the sensor reaction element, or both. And at least a part of the other deformable element can be extended between the deformable element and the object. In this case, the deformable element can be rephrased as the first deformable element, and the other deformable element as the second deformable element. When the object moves toward the second deformable element, the second deformable element may come into contact with the object. When the object exerts a force on the second deformable element during such contact, the second deformable element exerts a force on the first deformable element, the sensor reaction element, or both, and the first deformable element undergoes the deformation as described above. Also, thereby, deformation may occur in the second deformable element as well. However, the second deformable element can be configured to be less deformable than the first deformable element, and in some cases, the second deformable element may not deform at all. In a state where no force is applied, the thickness of the second deformable element in a direction perpendicular to the surface of the sensor can be configured to be smaller than the thickness of the first deformable element. The bulk modulus and / or shear modulus of the second deformable element can be different from those of the first deformable element. Specifically, the bulk modulus of the second deformable element can be set to a bulk modulus higher than that of the first deformable element. In that case, it might be said that the second deformable element is stiffer and / or less flexible than the first deformable element. Therefore, since the second deformable element is stiffer than the first deformable element, the possibility of being damaged by contact with the object is lower than that of the first deformable element. Also, it can be rephrased that by the second deformable element serving as a protective layer for the first deformable element, direct contact between the first deformable element and the object is prevented, thereby preventing damage to the first deformable element. That is, the second deformable element protects the deformation characteristics of the first deformable element. Furthermore, the second deformable element can also function as a converter for the force applied by the object to the second deformable element. This can also be rephrased as the second deformable element evenly and uniformly dispersing the force applied from the object and transmitting it to the first deformable element.For example, if the surface where the object contacts the second deformable element is defined as the first contact surface, and the surface where the sensor reaction element, the first deformable element, or both contact the second deformable element is defined as the second contact surface, then the second deformable element disperses and transmits the force received at the first contact surface to the second contact surface. Note that depending on the shape of the object, the first contact surface may be smaller than the second contact surface. In this case, compared to the situation where the object directly contacts the first deformable element, the sensor reaction element, or both, the second deformable element reduces the force or pressure applied to the first deformable element and the sensor reaction element. As a result, the risk of damaging the first deformable element is reduced. In other words, the second deformable element can prevent the stress of the object from being applied pointwise to the first deformable element, the sensor reaction element, or both. In addition to or instead of this, the second deformable element can have a specific friction coefficient adapted to the object. In this case, the surface roughness of the second deformable element can be adjusted according to the surface roughness of the object in contact with the second deformable element. For example, when the friction coefficient of the object surface is low, the friction coefficient of the second deformable element can be increased to maintain a stable contact state between the object and the second deformable element. On the other hand, when the friction coefficient of the object surface is high, even if the friction coefficient of the second deformable element is decreased, a stable contact state between the object and the second deformable element can be maintained. In this way, even when the type of the object changes, the grip between the object and the second deformable element can be stabilized. Therefore, according to the type of the object, the second deformable element can be adjusted without changing the first deformable element. This enables the present soft sensor mechanism to be versatile for a wide variety of objects while using the same deformable element. This also includes the fact that the second deformable element can be reversibly attached to the first deformable element. In other words, the second deformable element can be made replaceable. In this way, different second deformable elements can be selected according to the application and the object.

[0017] In a further preferred embodiment of the present invention, the characteristics of the deformable element can be indicated by the shape, bulk modulus, shear modulus, or any combination thereof that the deformable element has. The shape of the deformable element in the undeformed state can be at least one of a cylinder, a cube, a cone, and a dome shape. The shape of the deformable element and other selected characteristics can be adapted to the implementation conditions.

[0018] In a further preferred embodiment of the present invention, the deformable element can be attached to the sensor. For example, the deformable element can be adhered to the sensor. In this case, a single layer of adhesive layer (such as tape, etc.) can be used. Also, instead of stably attaching the deformable element to the sensor, the deformable element can be in a state where it merely contacts the sensor. In a further example, the deformable element can be in a state where it does not contact the sensor at all. In this case, there is a free space between the deformable element and the sensor, and holding means can be provided to hold the deformable element in a state separated from the sensor. Although several examples have been given above, these examples should not be understood as being intended to be limiting.

[0019] In a further preferred embodiment of the present invention, the soft sensor mechanism can further include a mechanical stopper that restricts the deformation of the deformable element. Thus, the mechanical stopper functions as a physical barrier that restricts the amount of deformation, that is, a physical barrier that restricts the amount of force acting on the deformable element. Thus, the mechanical stopper generates a reaction force against the force applied to the deformable element. As a result, the force and the reaction force at least partially cancel each other out. It can also be said that the mechanical stopper functions as a force absorber that absorbs at least a part of the force applied to the deformable element. The mechanical stopper can be a rigid element that occupies a shorter range with respect to the sensor than the range occupied by the non-deformed deformable element with respect to the sensor. Thereby, the deformable element can be at least partially deformed by an amount equal to the difference between the range occupied by the mechanical stopper and the range occupied by the non-deformed deformable element. Note that the mechanical stopper can be an element made of a material having lower elasticity than the deformable element itself instead of a rigid element. In this case, the mechanical stopper functions not as an emergency stop stopper but as a damper that suppresses the deformation of the deformable element. This is because a greater force needs to be applied to compress both the deformable element and the mechanical stopper. The mechanical stopper can also be configured not to restrict the deformation of the deformable element in at least one direction parallel to the surface of the sensor. This can also be said to mean that the mechanical stopper is designed such that the deformable element can freely move in at least one direction parallel to the surface of the sensor.

[0020] The mechanical stopper may be made of a single material or a plurality of materials. The mechanical stopper can be constructed so as to surround at least a part of the deformable element. Thereby, the mechanical stopper can also be configured to hold the deformable element at a certain position from the sensor.

[0021] For a mechanical stopper, at least a part of the deformable element can be provided with an extendable gap. This gap can also be referred to as an opening or a recess in the mechanical stopper where at least a part of the deformable element can extend.

[0022] The volume of the recess can be made larger than the volume that the undeformed deformable element extends into the recess. When the shear modulus of elasticity of the deformable element is not zero, when an external force is applied to the deformable element in a first direction, the deformable element deforms in at least one direction orthogonal to the first direction. This situation can also be rephrased as the deformable element undergoing not only linear compression but also quenching. If the volume of the recess is larger than the volume that the undeformed deformable element extends into the recess, the recess can easily accommodate the deformable element that has undergone quenching. Specifically, the recess can be adapted such that the deformable element is constrained only in one of the directions orthogonal to the applied external force and is not constrained in the remaining directions orthogonal to the applied external force, allowing the deformable element to freely deform in the remaining directions orthogonal to the applied external force.

[0023] At least one edge of the mechanical stopper of the soft sensor mechanism that faces the deformable element can be provided with an inclination or a rounding. An edge is a sharp part in a geometrically shaped object. Also, an edge can be rephrased as a part having one or more sharp corners. A sharp corner has a risk of biting into the deformable element. Therefore, by shaving the edge facing the object from the mechanical stopper, damage to the deformable element can be prevented. Furthermore, by shaving the edge facing the object from the mechanical stopper, a specific volume is formed within the mechanical stopper, and this volume can be the volume that the deformable element that has undergone quenching can occupy.

[0024] The distance from the mechanical stopper to the sensor can define a space into which a deformable element deformed by an external force can enter. The location where the deformable element touches the sensor is the location where the sensor places a limit so that the deformable element does not expand further. Therefore, at that location, the deformable element is at risk of receiving the strongest quench. It can also be said that the sensor defines a mechanical barrier that the deformable element cannot exceed. Therefore, a space extending from the sensor to the mechanical stopper can be defined. It can also be said that a pocket can be defined inside the mechanical stopper depending on the distance from the sensor. It may also be said that a space is provided between the sensor and the mechanical stopper. When the deformable element is not deformed, this space can be regarded as an empty space. However, even when the deformable element is not deformed, at least a part of this space may be occupied by the deformable element. This space serves to accommodate at least a part of the deformable element after deformation. This space contributes to suppressing the strain acting on the deformable element by providing a volume for the deformable element during expansion.

[0025] The mechanical stopper surely prevents a situation in which an excessively large force is applied to the sensor by the compressed deformable element and damages the sensor. If an excessive force load is applied to the sensor, there is a risk of cracking or breakage of the sensor. Further, the mechanical stopper also prevents the sensor reaction element from approaching the sensor too closely. If the sensor reaction element approaches the sensor too closely, not only can it cause physical damage to the sensor, but there is also a possibility that the sensor reaction element reacts to the sensor and reduces the sensitivity of the sensor.

[0026] In another preferred embodiment of the present invention, the sensor of the soft sensor mechanism can be a passive magnetic sensor, and the sensor reaction element can be an element that generates a magnetic field (for example, a permanent magnet). The magnetic sensor is a sensor that measures at least one characteristic of the magnetic field generated from the sensor reaction element. A passive magnetic sensor means a sensor that detects at least one characteristic of the magnetic field generated by the sensor reaction element but does not generate the measured magnetic field itself. Generally, a magnetic field is a vector field. That is, the characteristics of the magnetic field at each point in space can be represented by a three-dimensional vector representing the magnetic field strength. The passive magnetic sensor can measure one or more magnetic fluxes obtained by projecting the magnetic vector field onto one or more surfaces associated with the passive magnetic sensor. Thus, in this case, it can be said that at least one characteristic to be measured is the magnetic flux passing through each surface. The measured magnetic flux is proportional to the density of the magnetic field lines passing through each surface at an angle perpendicular to each surface. And when the magnetic flux passes through each surface, the passive magnetic sensor outputs a signal (for example, a current signal or a corresponding voltage signal) corresponding to each magnetic flux. Specifically, the output signal can be proportional to the distance from the sensor reaction element to the sensor. When the position of the sensor reaction element changes, the position of the magnetic field lines also changes. Thus, the change in the position of the sensor reaction element is directly related to the change in the magnetic flux measured by the passive magnetic sensor. The output signal can directly indicate how the position of the sensor reaction element has changed, and by further processing and synthesizing the output signal, it can also be configured to identify the relative position of the sensor reaction element with respect to the sensor. Therefore, an algorithm for identifying the position of the sensor reaction element from the magnetic flux measurement value signal can be configured to rely on the difference value between the signals. In addition to or instead of this, based on the signal measured for the displaced sensor reaction element after the deformable element has deformed and the signal measured for the sensor reaction element in the initial position before the deformable element deforms, it can be configured to calculate the gradient. And another algorithm can be used to estimate the applied external force from the position identified by the above algorithm.However, it is also possible to directly estimate the applied external force from the magnetic flux measurement value signal without obtaining the position of the sensor reaction element as an intermediate value. That is, generally speaking, a change in the interaction between the sensor reaction element and the passive magnetic sensor causes a change in at least one characteristic of the magnetic field, which is measured by the passive magnetic sensor, and then, using an algorithm, the external force that caused the change in such interaction can be estimated from at least one characteristic of the measured magnetic field.

[0027] In addition to or instead of this, the magnetic flux gradient can also be directly measured using a transducer that senses the magnetic field gradient. When the measurement signals are subtracted from each other, the influence of the static levitation magnetic field is canceled out. Therefore, by using the difference value or the gradient, it becomes possible to identify the position without being affected by the levitation magnetic field. Also, the passive magnetic sensor can measure the direction of the magnetic field intensity vector in addition to or instead of the magnetic flux. By measuring the direction of the magnetic field intensity vector, one or more angles representing the direction of the magnetic field in space can be obtained. Based on this direction, the force applied to the deformable element can be derived. Also, by utilizing the change in the direction of the sensor reaction element with respect to the sensor, it becomes possible to derive at what angle the object deformed the deformable element. That is, it becomes possible to identify whether the applied force was a uniform force or a non-uniform force.

[0028] The passive magnetic sensor can include at least one sensor element that measures at least one physical characteristic of the magnetic field. The at least one sensor element can be any of all devices suitable for measuring at least one characteristic of the magnetic field generated from the sensor reaction element, such as a magnetoresistive sensor, a Hall sensor, etc.

[0029] In another preferred embodiment of the present invention, the sensor of the soft sensor mechanism can be an active magnetic sensor, and the sensor reaction element can be targeted. An active magnetic sensor measures at least one physical property of a magnetic field. However, unlike the passive magnetic sensor described above, in the case of an active magnetic sensor, it generates at least one magnetic field by itself. In other words, an active magnetic sensor is a sensor that generates a magnetic field by itself. An active magnetic sensor observes the magnetic interaction between the magnetic field generated by the sensor itself and the target. An active magnetic sensor can be composed of one sensor element configured to perform both the generation of a magnetic field and the measurement of magnetic field fluctuations caused by a target. For example, the one sensor element can be adapted to operate as a magnetic field generator during a first period and as a detector of magnetic field fluctuations caused by a target during a second period. Alternatively, the active magnetic sensor can also be composed of at least two sensor elements. In that case, at least one of the at least two sensor elements can be configured to generate a magnetic field, and at least one other sensor element of the at least two sensor elements can be configured to measure magnetic field fluctuations caused by a target. Note that the sensor element configured to measure at least one physical property can be the same as the sensor element of the passive magnetic sensor described above.

[0030] The generated magnetic field is affected by the target, and at least one physical property of the magnetic field affected in this way is measured by a sensor element configured to measure at least one physical property. The shape of the target can be a shape that is not rotationally invariant. Specifically, the target can be planar or substantially planar. Thereby, the target can have a shape that preferentially affects the magnetic field in a preferred direction. Such a direction can be substantially the same direction throughout the target. For example, by making the target have a structure in which induced current tends to preferentially flow in a specific linear direction, the influence that the target exerts on the generated magnetic field can also be made directional. To have such a structure, the target can include at least one slit extending from one end of the target to the other end. However, different target designs are equally possible as well.

[0031] Alternatively, it can also be said that the target affects the magnetic flux coupling between the magnetic field generator and the detector that measures at least one physical property of the generated magnetic field. The target can include a soft magnetic material or a non-magnetic conductive material. Here, the soft magnetic material means that the magnetic material constituting the target is a material that is easily magnetized and easily loses magnetization. Also, the soft magnetic material can be rephrased as a material characterized by rapidly losing magnetization when the external magnetic field is removed. The soft magnetic material is a material with a high relative permeability and / or a low coercive force. Coercivity (coercive field) may sometimes also be called magnetic coercivity or coercive force, and it is a measure indicating how well a ferromagnetic material can maintain magnetization without demagnetizing against an external magnetic field. A ferromagnetic material with a high coercive force is called a hard magnetic material and is used, for example, as a material for permanent magnets. On the other hand, a material with a low coercive force can be called a soft magnetic material. Also, the soft magnetic material can be rephrased as a material with a small residual magnetization. Although not limited, generally, a magnetic material with a coercive force below 1000 A / m is called a soft magnetic material. However, this is only an example and should not be understood as an intended limitation.

[0032] When the target is made of a soft magnetic material, the target can affect magnetic flux coupling by concentrating the magnetic field lines of the generated magnetic field. The soft magnetic material can be made of an isotropic material having no preferred direction. On the other hand, when the target is made of a nonmagnetic conductive material, energy can be dissipated by the induced current flowing in the conductive material of the target. The induced current can flow as an eddy current. In this case, the target affects magnetic flux coupling by causing losses in the generated magnetic field due to the dissipation of energy. Optionally, the target can be shaped to align the magnetic field lines of the generated magnetic field in a preferred direction. Also, in addition to or instead of this, it can be said that the target functions as a magnetic field line rectifier that aligns the magnetic field lines in a preferred direction. When setting the position and orientation of the target such that the preferred direction of the magnetic field lines becomes the direction of the sensor element that measures at least one physical property, the measured value of at least one physical property takes a maximum value.

[0033] In another preferred embodiment of the present invention, the sensor of the soft sensor mechanism can include a photoreceiver that detects light, and the detected light can be light emitted, reflected, or scattered back from the sensor reaction element. The photoreceiver outputs an electronic signal according to the amount of received light. The physical property to be measured can be, for example, light intensity. The sensor reaction element is characterized by not absorbing at least a part of the light incident on the sensor reaction element. That is, when light is guided to the sensor reaction element, it can be said that the sensor reaction element responds with the light that is not absorbed out of the guided light. This response can be performed by reflection, scattering, or emission of light. For example, when the sensor reaction element responds by reflection of light, the sensor reaction element returns the light that is not absorbed out of the incident light at a reflection angle having the same magnitude as the angle at which the light is incident on the sensor reaction element (Snell's law of reflection). On the other hand, when the sensor reaction element responds by scattering or emission of light, the sensor reaction element can return the light that is not absorbed out of the incident light at an angle that may deviate from the reflection angle predicted by the law of reflection. Also, when the sensor reaction element responds by emission of light, the wavelength of the returned light may be different from the wavelength of the light incident on the sensor reaction element. Therefore, regardless of whether the response is by reflection, scattering, or emission of light, the sensor reaction element can return a part of the light incident on the sensor reaction element at the same solid angle as the solid angle of the light incident on the sensor reaction element. In addition to the above-described configuration, the sensor reaction element itself can also be adapted to generate light and emit this light toward the sensor.

[0034] When the sensor reaction element moves and the distance from the photoreceiver increases, the returning light spreads over a larger solid angle, so the light intensity measured by the photoreceiver decreases. On the other hand, when the sensor reaction element approaches the photoreceiver, most of the solid angle of the light returning from the sensor reaction element is covered by the photoreceiver, so the measured light intensity increases. Also, when the distance between the sensor reaction element and the photoreceiver varies, the angle of the sensor reaction element as seen from the photoreceiver also changes. Similarly, when the orientation of the sensor reaction element changes, the angle of the sensor reaction element as seen from the photoreceiver also changes, so the intensity of the detected light changes. Thus, due to the change in the angle of the sensor reaction element captured by the photoreceiver, an effect is obtained in which the ratio of the returning light that enters the detection area of the photoreceiver changes. Therefore, the measured light intensity becomes a physical characteristic that enables the unambiguous estimation of the position and orientation of the target.

[0035] Those skilled in the art will recognize that it is also possible to estimate the position and orientation of the sensor reaction element by utilizing other physical properties of light (for example, the polarization state of the returning light).

[0036] The photoreceiver can be an extended non-point-like detection element similar to those used in avalanche photodiodes, spot photodetectors, photogrammetric devices, or CMOS cameras. However, any other type of device that outputs an electronic signal corresponding to the amount of received light can be used as the photoreceiver.

[0037] Optionally, the original emission source of the light returning from the sensor reaction element can also be the optical transmitter provided in the sensor or an external light source separate from the sensor. The optical transmitter or the external light source can be a light-emitting device of a type such as a laser diode or a light-emitting diode (LED). However, the light returning from the sensor reaction element can also be derived from ambient illumination.

[0038] In a further preferred embodiment of the present invention, the sensor can include a semiconductor package in which an integrated circuit (IC) is embedded. In other words, the sensor can be constructed as an integrated circuit (IC) that is part of a semiconductor structure. Generally, an integrated circuit (IC) is understood to be a very small electronic circuit composed of a plurality of functional units attached or integrated to a semiconducting substrate. These functional units can include, for example, transistors, diodes, Hall sensors, coils, laser diodes, photodetectors, and electrical connection parts or waveguides. "The integrated circuit (IC) is embedded in the semiconductor package" means that the semiconductor package surrounds at least a part of the integrated circuit (IC). In many cases, it is advantageous to place the control device that processes the signal output from the sensor and transmits commands to the sensor in a location not too far from the sensor. This is because such an arrangement can avoid signal loss due to the electrical resistance of the wiring between the sensor and the control device. Therefore, such a control device or processing means can also be embedded in the semiconductor package together with the sensor. A person skilled in the art will recognize that the sensor or a part of the sensor can be integrated with the control device on the same semiconductor substrate to form a complex integrated circuit.

[0039] Even when the integrated circuit (IC) implementing the sensor is embedded in a semiconductor package, it is still necessary to avoid damaging or applying stress to the semiconductor package. This is because if the semiconductor package is damaged, the embedded integrated circuit (IC) may also be damaged, and if stress is applied to the semiconductor package, it may be converted into stress on the integrated circuit (IC), which may result in a decrease in the performance of the IC.

[0040] In a further preferred example of an embodiment, the sensor reaction element may be composed of a single element or a plurality of elements. That is, the sensor reaction element may be made of one material or a set of materials composed of a plurality of materials. When the sensor reaction element is formed from a set of materials composed of a plurality of materials, the respective materials can be in contact with each other. However, at least one of such a set of materials can also be in a state of being isolated from all the other materials forming the sensor reaction element. For example, when the sensor is a magnetic sensor, the sensor reaction element can include one or more magnets, one or more conductors, or both. On the other hand, when the sensor is an optical sensor, the sensor reaction element can include one or more reflectors, scatterers, or absorbers. The sensor reaction element can also be composed of powder. In that case, the sensor reaction element can be composed of a substance consisting of a large number of loose grains. For example, in the case of a magnetic sensor, the sensor reaction element can be composed of powder of a magnetic compound, powder of a conductive compound, or both. On the other hand, when the sensor is an optical sensor, the sensor reaction element can be composed of powder of a reflector, scatterer, or absorber. The powder can also be powder of nanoparticles. Nanoparticles are particles that cannot be seen by the human eye. For example, in the case of a magnetic sensor, the sensor reaction element can be composed of powder of magnetic nanoparticles, powder of conductive nanoparticles, or both, and in the case of an optical sensor, the sensor reaction element can be composed of powder of reflective nanoparticles, scattering nanoparticles, or absorptive nanoparticles.

[0041] The above object can also be solved by a method for measuring force using the soft sensor mechanism according to the present invention. The method includes receiving a signal from a sensor when a deformable element, at least a part of which extends between the sensor and the sensor reaction element, is deformed by the force to be measured, and estimating the strength 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.

[0042] The sensor response element is adapted to generate a physical signal in the sensor that varies according to the relative position and orientation of the sensor response element with respect to the sensor. The physical signal may be a one-dimensional signal or a multi-dimensional signal. Further, the physical signal may be a single one-dimensional or multi-dimensional signal, or a multivariate signal sequence of one-dimensional or multi-dimensional signals (e.g., a temporal trajectory of one-dimensional or multi-dimensional signals). When the position and orientation of the sensor response element change, the physical signal detected by the sensor also undergoes a corresponding signal change.

[0043] Before an external force is applied to the sensor mechanism, the sensor reaction element is located at a first position relative to the sensor. This first position is defined by the extent to which the deformable element extends between the sensor and the sensor reaction element. This first position is where the measurement of the first signal is taken. When the deformable element is deformed by an external force, the sensor reaction element moves to a second position. When the deformable element is compressed, the second position is closer to the sensor than the first position. Due to such a change in the position of the sensor reaction element, the reaction between the sensor reaction element and the sensor changes, and the measured value by the sensor also changes. Then, when the external force is removed from the deformable element (for example, by releasing an object pressing against the deformable element), the deformable element returns to its initial shape, and due to the associated movement, the sensor reaction element also returns to the first position, and the sensor comes to determine the corresponding initial physical signal again. On the other hand, when the deformable element is stretched without being compressed, the second position is farther from the sensor than the first position. Due to such a change in the position of the sensor reaction element, again, the reaction between the sensor reaction element and the sensor changes, and the measured value by the sensor also changes. Then, when the external force is removed from the deformable element (for example, by releasing an object pulling on the deformable element), the deformable element returns to its initial shape, and due to the associated movement, the sensor reaction element also returns to the first position, and the sensor comes to determine the corresponding initial physical signal again. In either case, as described above, the applied external force can be estimated from the physical signal using a look-up table or an algorithm. Therefore, there is no need to find an explicit analytical formula or mathematical model representing the relationship between the physical signal and the applied external force. Instead, by using a machine learning (ML) approach, the non-linear stress-strain curve of the deformable element can be sampled. Accordingly, by applying machine learning (ML) to estimate the correlation between the force value and the sensor signal value, if a sensor signal is given, the force can be estimated using this correlation.

[0044] The above object can also be solved by a gripping device having at least two robotic fingers according to the present invention. At least one of the at least two robotic fingers of the present gripping device is provided with a soft sensor mechanism according to the present invention. The robotic finger can be a mechanical device adapted to apply a force to an object. When the gripping device includes two robotic fingers facing each other, the two robotic fingers facing each other may be called jaws. The two robotic fingers facing each other of the jaws can have complementarity with each other in the sense that there is at least one symmetry axis common to the two robotic fingers constituting the jaws. It should be noted that those skilled in the art will understand that any number of robotic fingers can be used.

[0045] In the gripping device according to the present invention, at least one of the at least two robotic fingers of the gripping device can be configured to include one soft sensor mechanism, and the other robotic finger of the at least two robotic fingers can be configured not to include a soft sensor mechanism. In this case, a gripping force is applied to the gripped object from both robotic fingers, but the measurement of the gripping force is performed using only one robotic finger. Also, by providing the soft sensor mechanism according to the present invention on each of two or more of the at least two robotic fingers, redundancy can be provided in the measurement of the gripping force. For example, when two of the at least two robotic fingers each include a soft sensor mechanism and the gripping forces applied by the two robotic fingers are on the same line of action, that is, when the object is gripped at the same angle from both sides, the absolute values of the measured gripping forces of the two soft sensor mechanisms are equal. Therefore, by using two or more soft sensor mechanisms, advantages such as improving the accuracy by taking the average of the measured values when identifying the force, and avoiding a situation where the force cannot be identified even if a problem occurs in one soft sensor mechanism can be obtained.

[0046] In another preferred embodiment of the present invention, at least one soft sensor mechanism of the gripping device can be detachably attached to at least one robot finger. Here, "detachable" means that the soft sensor mechanism can be removed from the robot finger without damaging the soft sensor mechanism or the robot finger. When at least one soft sensor mechanism is detachably attached to each robot finger, the soft sensor mechanism can be replaced with little effort and cost. For example, at least one soft sensor mechanism can be attached to each robot finger using one or more screws, adhesives, or tapes. Also, the soft sensor mechanism can be fixed to each robot finger with a clamp. In this case, the soft sensor mechanism and the corresponding robot finger can be provided with bearings, and the soft sensor mechanism can be attached to each robot finger by pressing or attracting these bearings to each other.

[0047] In another preferred embodiment of the present invention, at least one soft sensor mechanism of the gripping device can be monolithically integrated with at least one robot finger. In this case, the soft sensor mechanism and the corresponding robot finger of the gripping device can be manufactured integrally, for example. That is, the soft sensor mechanism and each robot finger can be manufactured in a monoblock structure. For example, some parts of the soft sensor mechanism can be made as one part integrally with some parts of the robot finger. Also, the soft sensor mechanism and the corresponding robot finger can be first manufactured as two separate parts and then integrated by overmolding into one part. During overmolding, the two parts can be heated to connect the two molten regions of the two separate parts, and after cooling, this connection portion constitutes a rigid link between the soft sensor mechanism and the corresponding robot finger.

[0048] The above object can also be solved by a method of operating a gripping device mechanism for gripping an object by a gripping device according to the present invention. The gripping device includes at least two robotic fingers, and at least one of the at least two robotic fingers is provided with a soft sensor mechanism. The method includes the step of expanding the distance between at least two robotic fingers of the gripping device until the object to be gripped fits within the distance between the at least two robotic fingers. The method further includes gripping the object by reducing the distance between at least two robotic fingers, thereby applying a force to the object to deform a deformable element of the soft sensor mechanism, and measuring the force applied to the object by at least two robotic fingers by a reaction of the sensor to a sensor reaction element, wherein at least a part of the deformable element extends between the sensor and the sensor reaction element, and further includes the step of controlling the movement of at least two robotic fingers based on the measurement value. Thereby, a feedback loop can be formed between the force measurement value and the force applied to the object by at least two robotic fingers.

Brief Description of the Drawings

[0049] In the following description and the accompanying drawings, specific exemplary embodiments of the above-described soft sensor mechanism, gripping device, and two methods will be described in detail. However, these embodiments merely illustrate some of the various ways of using the principles of the various embodiments, and the embodiments described herein are intended to include all such embodiments and their equivalents.

[0050] Throughout the plurality of drawings, like parts are denoted by like reference numerals. Note that the drawings are not necessarily drawn to scale. Rather, they generally focus on explaining the general principles of the present invention.

[0051] In the following description, various embodiments of the present invention will be described with reference to the following drawings.

Figure 1

Figure 2a

Figure 2b

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0052] Hereinafter, a detailed description will be given with reference to the accompanying drawings. The accompanying drawings exemplarily show specific details and embodiments in which the present invention can be implemented

[0053] In this specification, the term "exemplary" means "given as an example or illustration". Therefore, embodiments or designs described as "exemplary" in this specification should not necessarily be construed as being more preferable or advantageous than others

[0054] FIG. 1 is a cross-sectional view showing a soft sensor mechanism 100 according to an exemplary embodiment of the present invention. The soft sensor mechanism 100 includes a sensor 110, a deformable element 120, and an element 130 (a "sensor reaction element") that reacts to the sensor 110. The deformable element 120 can include, for example, at least one of an elastomer, a polymer, a rubber, and a vulcanizate. Further, the deformable element 120 can be constituted by a flexible element, an elastic element, or a flexible structure. The flexible element or the flexible structure can be made of metal. For example, the flexible element or the flexible structure can be constituted by a flexible metal beam. In the illustrated exemplary embodiment, the element 130 is completely embedded in the deformable element 120. "Completely embedded" means a state in which the deformable element 120 completely surrounds the element 130 and all surfaces of the element 130 are in contact with the deformable element 120. It can also be said that the element 130 is wrapped in the material of the deformable element 120. The deformable element 120 is configured to be deformable by applying an external force. When an external force is applied, the deformable element 120 may be compressed, whereby the distance between the element 130 and the sensor 110 changes. The sensor 110 can detect this change in distance. For example, when the element 130 is a magnet and the sensor 110 is a magnetic sensor, as the distance between the element 130 and the sensor 110 decreases, the sensor detects a magnetic field (e.g., a different magnetic field strength, magnetic field orientation, or both) different from that before deformation. Therefore, it is possible to estimate how much the deformable element 120 has deformed from the change in the value of the physical unit used for the measurement. However, those skilled in the art will recognize that it is also possible to measure the compression distance of the deformable element 120 using other combinations of types of sensors 110 and elements 130.

[0055] Since the deformation that occurs in the deformable element 120 varies depending on the applied external force, conversely, it means that the applied external force is related to the physical measurement value obtained from the sensor 110. Therefore, there is a correlation between the value of the applied external force and the measurement value of the sensor 110 corresponding thereto. Such a correlation can be specified at the time of initial calibration of the sensor 110, and can also be obtained in advance if the bulk modulus or shear modulus of the deformable element 120 is known. Further, the correlation can be defined, for example, in the form of a look-up table including a plurality of external force values and sensor indication values associated therewith. The correlation between the applied external force value and the measurement value of the sensor 110 corresponding thereto can be clarified using a model trained by machine learning. Those skilled in the art will recognize other methods for clarifying individual correlations, but all such other methods are also included in this specification. Once the measured value of the sensor 110 is obtained, the external force can be estimated using the look-up table. When the bulk modulus, shear modulus, or both of the deformable element 120 are known, it is also possible to use an algorithm to output the actually applied force from the amount of deformation by simple calculation. The algorithm can be a non-linear model that defines the actual force as a non-linear function of the measurement value of the sensor 110. The algorithm or correlation can be implemented either inside the integrated circuit (IC) in which the sensor 110 is incorporated, outside the integrated circuit in which the sensor 110 is incorporated, or a part thereof (for example, the part that calculates the position of the element 130 from the sensor signal) is implemented inside the integrated circuit in which the sensor 110 is incorporated, and a part thereof (for example, the part that estimates the force from the displacement of the element 130) is implemented outside the integrated circuit in which the sensor 110 is incorporated. The sensor 110 can also be configured to perform dual sensing capable of detecting linear force and shear force. For example, it can be configured to sense a linear force that travels straight in the direction of the external force and a shear force in one direction in the plane perpendicular to the direction of the external force or two directions perpendicular to each other. The value of the applied external force and the measurement value of the sensor 110 can be directly associated by the correlation or algorithm.Optionally, the displacement amount of the element 130 can also be calculated as an intermediate step based on a correlation or an algorithm. In that case, the position of the element 130 is identified from the measurement value of the sensor 110 according to a first correlation or a first algorithm, and the value of the external force applied from the position of the element 130 is identified according to a second correlation or a second algorithm. Therefore, in this case, as an intermediate step, a step of determining the position of the element 130 is performed.

[0056] In the illustrated example, the soft sensor mechanism 100 further includes a mechanical stopper 140 that restricts the deformation of the deformable element 120. By thus restricting the maximum deformation amount of the deformable element 120, it is possible to avoid damage to the sensor 110 and the deformable element 120 due to the deformation of the deformable element 120. In the illustrated embodiment, the mechanical stopper 140 surrounds at least a part of the sensor 110. The sensor 110 is held at a specific position within the mechanical stopper 140 by a gap 150 formed in the mechanical stopper 140. The sensor 110 can be fixed to the mechanical stopper 140, or can be fixed to the mechanical stopper 140 in a replaceable manner. By adopting the latter configuration, it becomes possible to use the same mechanical stopper 140 in different sensor mechanisms. Such a situation may include, for example, a case where it is necessary to change the sensor 110 to a more appropriate type due to a change in environmental conditions or for repair and maintenance management.

[0057] In the illustrated embodiment, the deformable element 120 is disposed in a gap (opening) 150 within the mechanical stopper 140. Thereby, a first end portion of the deformable element 120 contacts the sensor 110, and a second end portion of the deformable element 120 on the side opposite to the first end portion extends from the gap (opening) 150 of the mechanical stopper 140. When a force is applied to the second end portion, the second end portion approaches the sensor 110 (as shown in FIGS. 2a and 2b). The element 130 embedded in the deformable element 120 is, in the illustrated embodiment, at a position at a distance d from the sensor 110. 1 The distance d from the sensor 110 to the element 130 1is the distance d from the sensor 110 to the second end of the deformable element 120 2 is smaller than the distance d from the sensor 110 to the end face of the mechanical stopper 140 3 and larger.

[0058] Although not intended to be limiting, the distance d from the sensor 110 to the element 130 1 can be 3 mm, and the distance d from the sensor to the second end of the deformable element 120 2 can be 4 mm, and the distance d from the sensor 110 to the end face of the mechanical stopper 140 3 can be 2.8 mm. Therefore, in this case, the action of the mechanical stopper 140 can limit the deformation amount of the deformable element to 1.2 mm. However, configurations that generally limit such deformation to less than 20%, or less than 30%, or less than 40% of the extension range of the deformable element 120 in the force application direction are also included in this specification. Also, the distance d from the sensor 110 to the element 130 in a state where no external force is applied 1 can be a distance smaller than the distance d from the sensor 110 to the end face of the mechanical stopper 140 3 It should be recognized by those skilled in the art that the names of the above dimensions are merely defined for the convenience of explanation and should not be understood as being intended to be limiting unless otherwise explicitly stated.

[0059] Figure 2a is a cross-sectional view showing the state where an external force ("pressure" in the figure) is applied to the soft sensor mechanism 100 shown in Figure 1. The external force can be a uniform force, that is, a constant force applied over the force application surface. However, in some cases, a non-uniform force, that is, a force with variations on the force application surface, may be applied as the external force. Such variations in the force on the application surface may be linearly varying variations or non-linearly varying variations. That is, in this case, different values of force can be assigned to each point on the force application surface, but the force value at each point and the force value at the adjacent point may show a linear relationship or a non-linear relationship. In the example of Figure 2a, the external force is a uniform force with respect to the surface of the deformable element 120 and is applied perpendicularly to the surface of the sensor 110. When the external force is applied, the deformable element 120 is compressed. As a result, the distance d from the sensor 110 to the second end of the deformable element 2 becomes a distance d 2 smaller than distance d 2 ’ down to. Also, since the element 130 is embedded in the deformable element 120, the distance d from the element 130 to the sensor 110 1 also becomes a distance d 1 smaller than distance d 1 ’ down to.

[0060] By reacting with the element 130, the sensor 110 changes from d 1 to d 1 ’configured to detect a change in the distance thereto. When the sensor 110 is a magnetic sensor and the element 130 is a magnet, since the magnetic field strength detected by the sensor 110 is proportional to the distance from the sensor 110 to the element 130, the sensor 110 detects a stronger magnetic field strength as the distance from the sensor 110 to the element 130 becomes shorter. By such a change in the magnetic field strength, the force applied to the deformable element 120 can be estimated. In some cases, when the sensor 110 is a magnetic sensor, the sensor 110 can also detect a change in the direction of the magnetic field strength vector, that is, 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 can be arranged offset with respect to the axis of the magnet. Although an example of measuring the distance in only one dimension, and thus an example in which the force is applied perpendicularly, is described, those skilled in the art will recognize that the element 130 may also be tilted at an angle as shown in FIG. 2b.

[0061] In FIG. 2b, an external force ("pressure" in the figure) is applied in a direction that is uniform but not perpendicular to the surface of the sensor 110. Therefore, when this external force is applied, the deformable element 120 deforms in a direction that is not perpendicular to the surface of the sensor 110. As a result, the distance d from the element 130 to the sensor 110 1 undergoes a non-uniform change. For example, the upper end of the element 130 moves to a relatively large distance d 1 ’ while the lower end of the element 130 moves to a relatively small distance d 1 ’’ When a non-linear force is applied, d 1 ’ and d 1 ’’Since they are at different distances, element 130 is inclined at an angle α other than zero with respect to sensor 110. Therefore, when an external force is applied in a non - vertical direction, element 130 undergoes not only translational movement but also rotational movement. Sensor 110 is adapted to detect a change in angle α by reacting with element 130. When sensor 110 is a magnetic sensor and element 130 is a magnet, when the angle α between sensor 110 and element 130 changes, the direction of the magnetic field lines of magnet 130 changes with respect to sensor 110, so sensor 110 detects this change in the magnetic field. It can also be said that when element 130 rotates by angle α, sensor 110 senses the rotation of the three - dimensional magnetic field generated by element 130. When rotating, the absolute intensity of the magnetic field does not change, but the direction of the magnetic field vector in space changes. As a result, the projection of the magnetic field vector onto the magnetic flux measurement plane of sensor 110 changes, so sensor 110 senses a magnetic flux different from the state where element 130 is not rotating. From the measured change in magnetic flux, the position change of element 130 can be estimated. The position change of element 130 is uniquely associated with the force acting on deformable element 120. Therefore, when a force non - perpendicular to deformable element 120 is applied, the rotation of element 130 can be used to identify the force applied to deformable element 120.

[0062] Mechanical stopper 140, as shown in FIGS. 1, 2a, and 2b, limits the deformation of deformable element 120 that occurs when an external force is applied to deformable element 120. Thereby, a finite minimum distance d given by the distance from the end of mechanical stopper 140 on the side opposite to sensor 110 to sensor 110 3 Regarding the distance d of the second end of deformable element 120 2 ’An effect of never falling below this value can be obtained. Further, since the movement of the element 130 is linked to the movement of compressing the deformable element 120, by restricting the deformation of the deformable element 120, the minimum distance between the element 130 and the sensor 110 is also defined. As a result, an advantage is obtained in that it is possible to avoid the element 130 approaching the sensor 110 too closely and damaging the sensor 110 or impairing the sensitivity of the sensor 110. For example, it is possible to avoid the influence of an excessive load being applied to the sensor 110.

[0063] Furthermore, if the deformable element 120 is deformed without limit, there is also a risk that the deformable element 120 itself will be damaged. For example, if the deformable element 120 is deformed too strongly, the internal bond of the deformable element may be broken and the deformable element may tear. This risk becomes particularly high when the element 130 is made of a material with higher rigidity than the deformable element 120. As a result, although the deformable element 120 may be damaged, this can be prevented by restricting the deformation of the deformable element 120.

[0064] In the exemplary embodiments shown in FIGS. 1, 2a, and 2b, the gap (opening or recess) 150 has a dimension that can accommodate the compressed deformable element 120 and the element 130.

[0065] Note that the dimension of the recess 150 can also be set such 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 a large external force exceeding the critical external force is applied, the element 130 does not enter the recess 150. Rather, the excess force of the external force exceeding the critical external force is directly conducted to the mechanical stopper 140. In this case, it can also be said that the mechanical stopper 140 and the element 130 cooperate to prevent the element 130 from contacting the sensor 110 or the deformable element 120 from being pressed too strongly against the sensor 110.

[0066] Optionally, the dimensions of the recess 150 of the soft sensor mechanism 100 can also be set to dimensions that accommodate at least a part of the element 130. In that case, by applying an external force to the element 130, at least a part of the element 130 can enter into the recess 150. Further, when at least a part of the deformable element 120 exists between the object pressed against the deformable element 120 and the element 130, this part of the deformable element 120 will also have a part compressed and enter into the recess 150. Then, when a critical force is applied to the object, the object comes into contact with the mechanical stopper 140. At this time, even if an external force exceeding the critical force is applied, the portion of the external force exceeding the critical force is conducted to the mechanical stopper 140. In this way, the recess 150 limits not only the strain of the portion of the deformable element 120 located between the sensor 110 and the element 130, that is, the portion of the deformable element 120 facing the sensor 110, but also potentially the strain exerted on the portion of the deformable element 120 located between the element 130 and the object, that is, the portion of the deformable element 120 facing the object. In other words, the mechanical stopper 140 can define the minimum distance of the element 130 from the sensor 110 and the minimum volume that the deformed portion of the deformable element 120 can occupy.

[0067] FIG. 3 is a cross-sectional view showing a soft sensor mechanism according to another embodiment of the present invention, characterized in that the two edges 345a, 345b of the mechanical stopper 140 are rounded. When the shear modulus of the deformable element 120 is not zero, when an external force is applied, the deformable element 120 deforms in at least one direction orthogonal to the direction of the applied external force. In other words, when the deformable element 120 is quenched, the volume occupied by the deformable element 120 in at least one direction orthogonal to the external force is larger than in the state where the deformable element 120 is not deformed (relaxed state). At this time, if the edge facing the deformable element 120 of the mechanical stopper 140 is sharp, there is a high possibility that the deformed deformable element 120, particularly the portion occupying the portion where the volume of the deformed deformable element 120 has increased, will be damaged. As a countermeasure against this, by rounding or inclining the edge 345 facing the deformable element 120 of the mechanical stopper 140, a volume suitable for accommodating at least the portion where the volume of the deformable element 120 has increased due to the shear deformation of the deformable element 120 is formed inside the mechanical stopper 140.

[0068] FIG. 4 is a cross-sectional view showing a soft sensor mechanism according to another embodiment of the present invention, characterized in that two spaces 445a, 445b for accommodating the material of the deformed portion of the deformable element 120 are provided. In the illustrated example, the two spaces 445 have a cubic shape, but in principle, they can take any other geometric shape suitable for accommodating the portion where the volume of the deformable element 120 has increased (not shown). The two spaces 445 shown are at one or more distances d from the starting surface of the mechanical stopper 140 to the sensor 110 4 and at one or more distances d from the axial surface of the mechanical stopper 140 to the surface of the undeformed deformable element 120 adjacent thereto 5can be defined by one or both of them. The axial surface of the mechanical stopper 140 is the surface of the mechanical stopper 140 perpendicular to the surface of the sensor 110, and the starting surface of the mechanical stopper 140 is the surface of the mechanical stopper 140 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 stopper 140 form the boundary surfaces of the space 445 shown in FIG. 4 (four boundary surfaces in the example of the cube shown in the cross-sectional view of FIG. 4). Also, when viewed from the side of the sensor 110, it can be said that the space 445 terminates at the starting surface of the mechanical stopper 140 and that one of the left and right boundaries is in contact with the axial surface of the mechanical stopper 140. Also, one or more edges of one or more spaces 445 can be rounded or inclined. In one example, at least one space 445 can extend over the entire height of the deformable element 120 measured in a direction perpendicular to the surface of the sensor 110 (not shown). In this case, it can be said that at least one space 445 forms a buffer volume between the non-deformed deformable element 120 and the soft sensor mechanism. In that case, the deformable element 120 can be made movable in the direction of the buffer volume formed by the at least one space 445. Thus, at least one space 445 can be formed so that the deformable element 120 is movable in at least one direction parallel to the surface of the sensor 110. Specifically, at least one space 445 can be formed so that the deformable element 120 is movable in all directions parallel to the surface of the sensor 110, or so that the deformable element 120 is movable only in one direction parallel to the surface of the sensor 110. Also, in order for the deformable element 120 to be movable in at least one direction parallel to the surface of the sensor 110, the mechanical stopper 140 can be configured not to limit the movement of the deformable element 120 in at least one direction parallel to the surface of the sensor 110. When the deformable element 120 is made movable only in one direction parallel to the surface of the sensor 110, this direction can be made to coincide with the direction of gravity. Thereby, a technical advantage is obtained in that, in addition to the force exerted by the object on the deformable element 120, the gravity acting on the object in contact with the deformable element 120 can also be measured.In this way, using the same sensor 110, the gripping force acting on the object and the mass of the object can be specified.

[0069] FIG. 5 shows a soft sensor mechanism in which the sensor 110 is a passive magnetic sensor 515 and the element 130 is an element that generates a magnetic field, or a soft sensor mechanism in which the sensor 110 is an active magnetic sensor and the element 130 is a target. In FIG. 5, the magnetization direction of the element 130 is parallel to the surface of the sensor 110. However, those skilled in the art will recognize that the magnetization direction of the element 130 with respect to the sensor 110 can be arbitrarily selected.

[0070] A passive magnetic sensor is a sensor that reacts to an external magnetic field. This external magnetic field can be the magnetic field generated from element 130. Thus, element 130 can be a permanent magnet, or a coil and / or wire through which an electric current flows. The electric current can be a direct current or an alternating current, whereby the wire and / or coil can generate a constant electromagnetic field or an electromagnetic field that changes with time. The passive magnetic sensor can include at least one sensor element capable of measuring at least one characteristic of the magnetic field generated from element 130. At least one characteristic measured by the sensor element can be, for example, the magnetic field strength. The at least one sensor element can be a Hall plate or a magnetoresistive sensor. Also, the at least one sensor element can include a fluxgate sensor, a magneto-impedance (MI) sensor. The Hall plate can be a lateral Hall plate with a maximum sensitivity axis perpendicular to the substrate, or a longitudinal Hall plate with a maximum sensitivity axis parallel to the substrate. The Hall plate can be made of silicon and can be integrated with, for example, a CMOS substrate. Also, the Hall plate can be made of a semiconductor compound (e.g., a group III-V semiconductor material such as GaAs) to improve the sensitivity compared to that made of silicon. By measuring at least one characteristic of the magnetic field generated from element 130, it becomes possible to identify the change in the distance from element 130 to sensor 110 that occurs when the deformable element 120 is deformed, and thereby it becomes possible to identify the force applied to the deformable element 120.

[0071] As an example, the passive magnetic sensor can include three sensor elements arranged at angular positions spaced at multiples of 120°. And each of the three sensor elements measures a B x magnetic field component parallel to the sensor plane and a B z magnetic field component perpendicular to the sensor plane. Thus, in such a passive magnetic sensor, six magnetic field components of the magnetic field generated from element 130 can be measured. Among these six magnetic field components, the magnetic field components at the first sensor position are (B x1 ,B z1) The magnetic field components at the second sensor position are (B x2 , B z2 ), and the magnetic field components at the third sensor position may be referred to as (B x3 , B z3 ). Element 130 is preferably disposed substantially above the common center of the three sensor elements. With these sensor elements, not only can the distance from element 130 to sensor 110 be specified, but the rotation for measuring a non-vertical force can also be easily specified.

[0072] Also, as another example, the passive magnetic sensor can include four sensor elements arranged at different angular positions. These angular positions can be angular positions that are multiples of 90°, or can be individually selected for each of the four sensor elements. And each of the four sensor elements measures the B x magnetic field component parallel to the sensor plane and the B z magnetic field component perpendicular to the sensor plane. Therefore, with such a passive magnetic sensor, eight magnetic field components of the magnetic field generated from element 130 can be measured. Among these eight magnetic field components, the magnetic field components at the first sensor position are B x1 , B z1 , the magnetic field components at the second sensor position are B x2 , B z2 , the magnetic field components at the third sensor position are B x3 , B z3 , and the magnetic field components at the fourth sensor position may be referred to as B x4 , B z4 .

[0073] In a more general embodiment of the present invention, the passive magnetic sensor can include N (N is a variable) sensor elements arranged at angular intervals, and an individual angular position can be associated with each of the N sensor elements. And each sensor element measures the B x magnetic field component parallel to the sensor plane and the B zmeasures the magnetic field component. Therefore, the passive magnetic sensor can measure 2*N magnetic field components of the magnetic field generated from the element 130, where N is the total number of sensor elements. Among these 2*N magnetic field components, the magnetic field component at the i-th sensor position may be referred to as B xi , B zi . Similar to the embodiment having N = 3 sensor elements described above, in any case of N, the element 130 is preferably disposed substantially above the center common to the N sensor elements. With these N sensor elements, not only the distance from the element 130 to the sensor 110 can be specified, but also the rotation in the case of measuring a non-vertical force can be easily specified.

[0074] On the other hand, an active magnetic sensor is a sensor configured such that the sensor itself generates and changes a magnetic field, and this magnetic field is fluctuated or affected by a target. Therefore, the active magnetic sensor can include at least one sensor element that generates a magnetic field and at least one sensor element that measures the fluctuation of the magnetic field generated by the sensor element. However, the active magnetic sensor can also be composed of at least one sensor element that performs both the generation of the magnetic field and the measurement of the magnetic field fluctuation. In this case, the sensor element can be adapted to operate as a sensor element that generates a magnetic field during a first period and as a sensor element that measures the magnetic field fluctuation during a second period. For example, the active magnetic sensor can include an electromagnetic wave having a magnetic field component that changes with time during a first period and a coil or wire that captures the electromagnetic wave during a second period. The magnetic field generated in this way can be fluctuated, for example, by induction by a target. Therefore, in this case, the target itself can be a non-magnetic material. For example, the target can be designed as a planar structure metal characterized by forming a conductive path in a certain preferred direction in space. Due to such a target, at least one characteristic of the magnetic field generated from the active magnetic sensor fluctuates, and the fluctuation generated in at least one characteristic of the generated magnetic field can be measured. And since the fluctuation generated in at least one characteristic of the generated magnetic field is proportional to the distance between the element 130 and the sensor 110, it becomes possible to specify the change in the distance between the target and the sensor 110 that occurs when the deformable element 120 is deformed due to such a magnetic field fluctuation.

[0075] In addition, when the spatial dimension of the element 130 (for example, a magnet or a target) is smaller than the spatial dimension of the sensor 110 (for example, a passive or active magnetic sensor), particularly when the spatial dimensions of the sensor 110 and the element 130 are in a ratio of 1.5 or more, for example, in the range of 1.5 to 3, the advantage of being able to measure the shear stress with high precision is obtained.

[0076] FIG. 6 is a cross-sectional view showing a soft sensor mechanism in which the sensor 110 is an optical sensor 610. The optical sensor 610 measures at least one physical property of an optical beam and outputs at least one physical signal proportional to the at least one measured physical property. In the illustrated embodiment, at least a part of the incident light 630 incident on the element 130 is reflected by the element 130, and the return light 640 returned from the element 130 can be measured by the optical sensor 610. In FIG. 6, the angles of the incident light 630 and the return light 640 have a relationship that follows the law of reflection (Snell's law). In the illustrated example, the incident light 630 is the light emitted by the optical transmitter 620 included in the sensor 110. However, the incident light 630 can also be external light or light generated by an external light source separate from the sensor 110 (not shown). Those skilled in the art will be able to conceive of various methods for creating the light incident on the element 130.

[0077] The physical property measured by the optical sensor 610 can be, for example, the intensity of the return light 640 from the element 130. The intensity of the return light 640 measured by the optical sensor 610 changes according to the relative position of the element 130 with respect to the sensor 110. For example, when the element 130 is at a position far from the sensor 110, the intensity recorded by the optical sensor 610 is relatively low. This is because the return light 640 spreads over a relatively large solid angle, so the proportion of the return light 640 hitting the surface of the optical sensor 610 is relatively small. On the other hand, when the element 130 is at a position close to the sensor 110, the return light 640 spreads over a smaller solid angle, so the proportion of the return light 640 hitting the surface of the optical sensor 610 is higher. Therefore, in this case, the intensity recorded by the optical sensor 610 is high. Thus, by recording such light intensity, it becomes possible to estimate the position of the element 130, and as described above, this position can be uniquely associated with the external force applied to the deformable element 120.

[0078] FIG. 7 is a cross-sectional view showing a gripping device 700. FIG. 7 shows an exemplary embodiment in which two sensor mechanisms are attached to the gripping device 700. The gripping device is a mechatronics device that applies a force and a corresponding reaction force to an object in order to manipulate the position and orientation of the object. Therefore, the gripping device 700 shown in FIG. 7 includes two robot fingers 710a and 710b. The robot fingers 710a and 710b are adapted to transmit a desired force and reaction force to the object. Although not limited, in the illustrated example, the gripping device 700 includes two robot fingers 710a and 710b, and each robot finger 710a and 710b includes one soft sensor mechanism. However, it is also possible to configure only one of the two robot fingers to include a soft sensor mechanism, or to configure the gripping device to include three or more robot fingers, and each of these robot fingers may or may not include a soft sensor mechanism (not shown). The two soft sensor mechanisms shown in the figure are detachably attached to the robot fingers 710a and 710b with screws (indicated by marks in FIG. 7). However, each soft sensor mechanism can also be monolithically integrated with the respective robot fingers 710a and 710b (not shown). A person skilled in the art will know which of the above options to use and when. As described above, "detachably attached" means attaching by some means that does not damage the soft sensor mechanism or the corresponding robot finger 710 when removing it. Such means include attachments such as screws (shown), adhesives, or adhesive tapes. Also, "monolithically integrated" means manufacturing the mechanical stopper 140a and the corresponding robot finger 710a as a single part, or manufacturing them as one or more separate parts and then molding them by overmolding to form the illustrated part of the gripping device 700. Note that a person skilled in the art will understand that in a special-purpose gripping device, there may be a case where the gripping device 700 needs to include three or more robot fingers 710, and in a simple force sensing application where only one of the force or reaction force applied by the gripping device 700 is measured, it is sufficient to incorporate one soft sensor mechanism into the gripping device 700 (not shown).

[0079] FIG. 8 is a cross-sectional view showing a gripping device 700 that holds an object 810 but does not deform a deformable element 120. The object 810 shown in FIG. 8 is positioned between a first soft sensor mechanism attached to a first robot finger 710a of the gripping device 700 and a second soft sensor mechanism attached to a second robot finger 710b of the gripping device 700. In the illustrated embodiment of FIG. 8, the space between the robot finger 710a and the robot finger 710b is reduced until the surfaces of the deformable elements 120a, 120b of the two soft sensor mechanisms contact the surface of the object 810. However, in the illustrated embodiment of FIG. 8, no force or reaction force has yet acted on the object 810 from the robot fingers 710a, 710b. Therefore, in FIG. 8, the deformable elements 120a, 120b of the soft sensor mechanism remain undeformed, and the physical values measured by the sensors 110a, 110b of the soft sensor mechanism are respectively physical values corresponding to the initial positions and / or orientations of the elements 130a, 130b embedded in the deformable elements 120a, 120b. Also, in the illustrated embodiment of FIG. 8, since no friction has yet occurred between the outer surfaces of the deformable elements 120a, 120b facing the object 810 and the corresponding surfaces of the object 810, it can be said that FIG. 8 shows the situation immediately before the gripping device 700 exerts a gripping action on the object 810.

[0080] FIG. 9 is a cross-sectional view showing the gripping device 700 while holding the object 810 while deforming the deformable element 120. In the embodiment shown in FIG. 9, the space between the robot finger 710a and the robot finger 710b of the gripping device 700 is further reduced compared to FIG. 8. Therefore, a first force is applied to the object 810 from the first robot finger 710a, and a second force is applied to the object 810 from the second robot finger 710b. In the example shown in FIG. 9, the first force and the second force are forces in opposite directions on the same straight line. As a result, the deformable elements 120a and 120b of the two soft sensor mechanisms 100 are deformed, and the positions and / or orientations of the elements 130a and 130b are changed from the positions and / or orientations corresponding to the undeformed initial shapes of the deformable elements 120a and 120b shown in FIG. 8. Therefore, the physical values measured by both sensors 110a and 110b are different from the physical values corresponding to the initial positions and / or orientations of the elements 130a and 130b as shown in FIG. 8.

[0081] The measured physical values can be mapped to the estimated values of the applied external forces using the method described above. More specifically, the physical value measured by the first sensor 110a can be mapped to the first force estimated value for the first force, and the physical value measured by the second sensor 110b can be mapped to the second force estimated value for the second force. Since the first force estimated value and the second force estimated value are redundant values with respect to each other, they can be averaged to obtain a more accurate resultant force estimated value. Also, when one of the sensors 110a and 110b fails, the value corresponding to the failed sensor among the first force estimated value and the second force estimated value can be substituted with the other value.

[0082] Specifically, the force estimation value can be the value of the multi-axis force. Therefore, the force estimation value can include not only the force exerted by the robot fingers 710a and 710b on the object 810, but also the gravity of the object 810. Thereby, the first force exerted by the robot finger 710a on the object 810 and the second force exerted by the robot finger 710b on the object 810 can be controlled as a function of the force estimation value. Specifically, the first force applied by the robot finger 710a and the second force applied by the robot finger 710b can be changed according to the gravity of the object 810 included in the force estimation value. For example, the greater the gravity of the object 810, that is, the greater the mass of the object 810, the first force exerted by the robot finger 710a on the object 810 and the second force exerted by the robot finger 710b on the object 810 can be set to be greater. Conversely, the smaller the mass of the object 810, the first force exerted by the robot finger 710a on the object 810 and the second force exerted by the robot finger 710b on the object 810 can be set to be smaller. Thus, a feedback loop can be formed between the first force applied by the robot finger 710a and the second force applied by the robot finger 710b and the gravity measurement value of the object 810. Furthermore, the first force exerted by the robot finger 710a on the object 810 and the second force exerted by the robot finger 710b on the object 810 can be limited so as not to grip the object 810 too strongly.

[0083] Therefore, the gripping device 700 including at least one soft sensor mechanism 100 according to the present invention can dynamically adapt the gripping force to the mass of the gripped object, and can surely and firmly grip the object 810 without applying excessive deformation to the object 810. Thereby, it is possible to surely grip the object without damaging or dropping it.

[0084] While the description has been given by way of examples of multiple embodiments of one or more embodiments, it is of course impossible to describe all possible combinations of components or methods in the description of the above embodiments. However, those skilled in the art will recognize that many more various embodiments with different combinations and orders are possible. Therefore, the embodiments described herein are intended to encompass all such variations, modifications, and alterations that fall within the spirit and scope of the appended claims.

Explanation of Reference Numerals

[0085] 100 Soft sensor mechanism 110 Sensor 120 Deformable element 130 Element (sensor reaction element) 140 Mechanical stopper 150 Gap 345 Edge 445 Space 515 Passive magnetic sensor 610 Optical receiver (optical sensor) 620 Optical transmitter 700 Gripping device 710 Robot finger 810 Object

Claims

1. A soft sensor mechanism (100) for measuring force, wherein the soft sensor mechanism (100) is Sensor (110) and A deformable element (120) configured to be deformable by the aforementioned force, In order to measure the force by the deformation of the deformable element (120), an element (130) that reacts to the sensor (110) and Equipped with, A soft sensor mechanism (100) in which at least a portion of the deformable element (120) extends between the sensor (110) and the element (130).

2. The soft sensor mechanism (100) according to claim 1, further comprising a mechanical stopper (140) that limits the deformation of the deformable element (120).

3. The soft sensor mechanism (100) according to claim 2, wherein the mechanical stopper (140) includes a gap (150) through which at least a portion of the deformable element (120) extends.

4. The soft sensor mechanism (100) according to claim 3, wherein the gap (150) has dimensions that allow it to accommodate at least a portion of the element (130).

5. The soft sensor mechanism (100) according to claim 2, wherein at least one edge (345a, 345b) of the mechanical stopper (140) facing the deformable element (120) is beveled and / or rounded.

6. The soft sensor mechanism (100) according to claim 2, wherein the distance from the mechanical stopper (140) to the sensor (110) defines a space (445a, 445b) into which the deformable element (120), which has been deformed by the applied force, can enter.

7. The soft sensor mechanism (100) according to claim 1, wherein the sensor (110) is a passive magnetic sensor (515), and the element (130) is an element that generates a magnetic field, for example, a permanent magnet.

8. The soft sensor mechanism (100) according to claim 1, wherein the sensor (110) is an active magnetic sensor and the element (130) is a target.

9. The sensor (110) includes an optical receiver (610) that detects light (640), The soft sensor mechanism (100) according to claim 1, wherein the detected light (640) is light that has been emitted, reflected, or scattered from the element (130) and returned.

10. The soft sensor mechanism (100) according to claim 1, wherein the element (130) is embedded in the deformable element (120).

11. The soft sensor mechanism (100) according to any one of claims 1 to 10, wherein the sensor (110) includes a semiconductor package in which an integrated circuit (IC) is embedded.

12. A method for measuring force using a soft sensor mechanism (100), The steps include receiving a signal from the sensor (110) when a deformable element (120), which extends at least a portion between the sensor (110) and an element (130) that responds to the sensor (110), is deformed by the force, The steps include: estimating the strength of the force from the received signal based on a predefined correlation between the force value and the signal value of the sensor (110); A method that includes this.

13. A gripping device (700) comprising at least two robotic fingers (710a, 710b), wherein at least one of the at least two robotic fingers (710a, 710b) is equipped with a soft sensor mechanism (100) according to any one of claims 1 to 10.

14. The gripping device (700) according to claim 13, wherein at least one of the soft sensor mechanisms (100) is detachably attached to each of the at least one robotic finger (710a, 710b), or at least one of the soft sensor mechanisms (100) is monolithically integrated with the at least one robotic finger (710a, 710b).

15. A method for operating a gripping device (700) to grasp an object (810), The gripping device (700) comprises at least two robotic fingers (710a, 710b), At least one of the two robot fingers (710a, 710b) is equipped with a soft sensor mechanism (100), and the method is as follows: The steps include: widening the distance between the at least two robot fingers (710a, 710b) of the gripping device (700) until the object (810) to be gripped fits within that distance; The steps include: grasping the object (810) by reducing the distance between the at least two robot fingers (710a, 710b), thereby applying force to the object (810) and deforming the deformable element (120) of the soft sensor mechanism (100); A step of measuring the force applied to the object (810) by the at least two robot fingers (710a, 710b) by the response of a sensor (110) to an element (130), wherein at least a portion of the deformable element (120) extends between the sensor (110) and the element (130); A step of controlling the movement of the at least two robot fingers (710a, 710b) based on the measured force; A method that includes this.

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