Device for detecting a force and / or pressure

Abstract

The device for detecting a force and / or pressure comprises a first element (2) having magnetic characteristics; a second element (3) for detecting a force and / or pressure applied to said first element (2), spaced apart from said first element (2), said second element (3) comprising a casing (4) containing a liquid magnetoelectric material (5).

Description

[0001] Description

[0002] DEVICE FOR DETECTING A FORCE AND / OR PRESSURE

[0003] Technical field

[0004]

[0001] The present invention relates to a device for detecting force and / or pressure, in particular for application in the field of robotics and joint prostheses.

[0005] Prior art

[0006]

[0002] For several decades, there has been a recognized need to improve the interaction of robots, for example industrial or medical robots, with the external environment and, specifically, to improve the ability of such robots to manipulate objects. This need is also felt in the field of joint prostheses, where one branch of research is aimed at developing active prostheses, i.e. , prostheses equipped with sensory feedback, which can replace the limb in a manner as close as possible to the native limb.

[0007]

[0003] The ability of robots or active joint prostheses to interact with the external environment is linked to tactile sensitivity. Therefore, an aspect related to part of this sensitivity, namely the measurement of forces, has been extensively investigated. In particular, different types of devices have been developed to detect forces or pressures.

[0008]

[0004] International application WO2019033159 describes a type of force detection device comprising a series of protrusions that extend from a base surface and have different lengths, each protrusion having an elongated pillar shape. When compression is applied to the protrusions, compressing them to the same height, the normal force measured on protrusions of different lengths is different. Assuming that the protrusions do not bend, when a tangential force is applied to the protrusions, the same tangential force is detected on protrusions of different lengths. Therefore, the ratio between the tangential force and the normal force for each protrusion is different. Preferably, each protrusion forms an internal cavity that extends from the base surface to an end, suitably spaced from the base surface, at which a reflector is mounted. A light source is associated with the base surface, and a light sensor is mounted at a predetermined distance from the base surface, on the opposite side from the reflector. A small opening is made on the base surface to allow the light reflected by the reflector to pass through to the light sensor. The device allows the force applied to each protrusion to be measured in three dimensions by analyzing the movement of the light spot detected by the light sensor.

[0009]

[0005] One problem with this device is that it is structurally complex and not easy to manufacture.

[0010]

[0006] A different type of force detection device is illustrated in US Patent 7,658,119. The device comprises a substantially rigid inner core surrounded by a layer of a deformable and / or elastic material that is associated with the core by means of a seal, wherein a predetermined volume of a deformable material is present between the deformable layer and the core. A plurality of electrodes are arranged on an outer surface of the core and are connected to a detection circuit. The material inserted between the deformable layer and the core may be a liquid or a gel having a sufficiently low electrical conductivity such that a change in the resistance measured between two or more electrodes in contact with the material occurs if the outer layer is mechanically deformed. The detection circuit is configured to detect changes in electrical resistance in the material between the electrodes as a result of the application of a force to the outer surface of the deformable layer.

[0011]

[0007] This type of sensor has mechanical characteristics that are advantageous for manipulating objects, as the texture reproduced is similar to that of human fingers. However, the sensor has a robustness problem because the outer layer is easily damaged, for example by contact with sharp objects, which can cause the liquid or gel filling material to leak out, resulting in a loss of sensor functionality.

[0012]

[0008] Another problem reported in the industry is that commercially available force detection devices are not easily usable in confined spaces, for example, when used as sensors on the fingertips of joint prostheses or robots.

[0013]

[0009] One type of commercially available sensor for detecting forces / torques in three spatial dimensions is based on strain-gage technology. These sensors are often used in applications where there is limited space to mount the sensors themselves, due to their size, but they generally require large acquisition electronics. As a result, these sensors are not convenient to use. Furthermore, a problem with these sensors is that they detect a resultant of the forces applied in a defined region and cannot detect forces applied at nearby points independently.

[0014]

[0010] Therefore, there is a need to develop devices for detecting forces or pressures that solve the above problems.

[0015] Disclosure

[0016]

[0011] The task of the present invention is to solve the aforementioned problems by devising a device for detecting a force and / or pressure that is easily adaptable to spaces of different sizes and shapes.

[0017]

[0012] Within the scope of this task, a further purpose of the present invention is to provide a device that can be installed in spaces of limited size.

[0018]

[0013] Another purpose of the invention is to provide a device that allows different ranges of force and / or pressure values to be measured.

[0019]

[0014] Another purpose of the invention is to provide a device for detecting force and / or pressure that has a long service life.

[0015] A further purpose of the invention is to provide a device for detecting force and / or pressure that is simple in design and function, with reliable operation, versatile use, and relatively low cost.

[0020]

[0016] The aforementioned purposes are achieved, according to the present invention, by the device for detecting a force and / or pressure according to claim 1.

[0021]

[0017] The device for detecting a force and / or pressure comprises a first element having magnetic characteristics; a second element for detecting a force and / or pressure applied to said first element, spaced apart from said first element, said second element comprising a casing containing a liquid magnetoelectric material, said liquid magnetoelectric material exhibiting a variation in electrical characteristics as an applied magnetic field varies.

[0022]

[0018] In particular, said casing contains a predetermined quantity of said liquid magnetoelectric material.

[0023]

[0019] Preferably, said second element also comprises at least one pair of electrodes, arranged on at least one surface of said casing, configured to detect said variation in the electrical characteristics of said liquid magnetoelectric material following a variation in the magnetic field generated by said first element upon application of a force on said first element.

[0024]

[0020] The device according to the present invention is adaptable to spaces of different sizes and shapes thanks to the provision of a second element comprising a magnetoelectric material in the liquid state because the liquid magnetoelectric material allows the casing to be given the shape most suitable for the application of the device. In particular, the provision of a liquid magnetoelectric material allows the device to be easily used in spaces of limited size due to the possibility of easily modifying the shape of the casing.

[0025]

[0021] A further advantage of the device is that it allows different ranges of force or pressure values to be measured, as it is sufficient to modify the stiffness of the first magnetic element. In fact, if the first element has greater stiffness, the force required to achieve a certain displacement or deformation of the first element will be greater. Therefore, to establish the ranges of force values to be measured, it is possible to simply modify the stiffness of the first element, for example by choosing a suitable material and / or modifying the geometry and / or thickness of the first element.

[0026]

[0022] Preferably, said second element comprises a plurality of electrodes.

[0027]

[0023] Preferably, said first element is a permanent magnet or an electromagnet.

[0028]

[0024] Alternatively, said first element comprises magnetic components, for example magnetic particles or nanoplatelets.

[0029]

[0025] Preferably, said first element is made of a composite material comprising a phase having magnetic characteristics and a phase having no magnetic characteristics.

[0030]

[0026] Advantageously, said first element has a first configuration, in which it generates a first magnetic field distribution in the absence of an applied force, and a second configuration, in which it generates, upon application of a force, a second magnetic field distribution, said variation in magnetic field between said first configuration and said second configuration causing a variation in the electrical characteristics of said liquid magnetoelectric material.

[0031]

[0027] Preferably, in said second configuration, said first element is brought closer to said second element or is spaced apart from said second element upon application of a force, and / or said first element is deformed as a result of the application of a force. It is observed that the deformation of the first element causes a variation in density, in particular with reference to the magnetic component, and this results in a different distribution of the magnetic field generated by the first element compared to the undeformed configuration.

[0032]

[0028] Both the variation in the distance of the first element from the second element and the variation in the density of the first element result in a variation in the distribution of the magnetic field generated by the first element.

[0033]

[0029] According to one aspect of the invention, the first element is deformable.

[0034]

[0030] Preferably, said first element is a magnetic elastomer.

[0035]

[0031] Preferably, said first element is a magnetic elastomer comprising a plurality of magnetic components, such as magnetic particles or nanoplatelets.

[0036]

[0032] Preferably, said magnetoelectric material comprises magnetoelectric particles or crystals.

[0037]

[0033] Advantageously, said device comprises an electrical circuit connected to said electrodes, said electrical circuit being configured to process electrical signals of the magnetoelectric force of said liquid magnetoelectric material detected by said electrodes and to derive information about the force and / or pressure applied to said first element.

[0038]

[0034] Preferably, the electrical signals comprise the voltage across at least one pair of electrodes.

[0039]

[0035] Advantageously, the electrodes are distributed on said at least one surface of said casing adjacent to each other to allow the detection of forces at a plurality of points independently. It should be noted that the ability to measure forces applied at points close to each other is due to the arrangement of the electrodes, which allow measurement at nearby points, and to the fact that the magnetoelectric material distributed inside the casing provides a fairly large sensitive surface and responds locally to changes in the magnetic field. In essence, the "map" of the electric field of the magnetoelectric material of the second element follows the "map" of the magnetic field generated by the first element.

[0040]

[0036] According to one aspect of the invention, said electrodes are distributed over said casing so as to form at least one matrix.

[0041]

[0037] Advantageously, said liquid magnetoelectric material also exhibits a variation in magnetic characteristics as an applied electric field varies. Therefore, the magnetization of the liquid magnetoelectric material can be controlled by an electric field.

[0042]

[0038] In light of this, the device can also be used as a transducer of electrical energy into mechanical energy, exploiting the fact that the magnetization of the liquid magnetoelectric material can be controlled by an electric field.

[0043]

[0039] According to this aspect, the first element is deformable and, following the application of a potential difference across the second element, at the ends of at least one pair of said electrodes, the first element is deformed. The above-mentioned advantages are also applicable to the device according to this aspect, for example, the fact that it is adaptable to spaces of different sizes and shapes.

[0044]

[0040] In particular, the application of a potential difference to the ends of the electrodes of the second element causes a variation in the magnetic field generated by the second element. The magnetic field generated by the second element interacts with the first magnetic element, causing deformation of the first element.

[0045]

[0041] The first element, which is deformed by interaction with the magnetic field generated by the second element, can perform the function of an actuator.

[0046]

[0042] The first element can be used to generate acoustic waves. The generation of acoustic waves occurs thanks to the vibration of the first element due to the application of a voltage to the ends of the electrodes of the second element that varies rapidly over time.

[0047]

[0043] Preferably, said voltage applied to said electrodes of said second element has a high frequency, preferably between 1 and 20 MHz, said first element generating acoustic waves upon application of said voltage.

[0048]

[0044] The device can therefore be used to generate acoustic waves, as already mentioned, for example ultrasonic waves. This aspect can be exploited in various fields of technology, such as, for example, the field of ultrasound imaging diagnostics, where the device can be used in an ultrasound probe.

[0049] Brief description of the drawings

[0050]

[0045] The details of the invention will be more evident from the detailed description of a preferred embodiment of the device for detecting a force and / or pressure, illustrated for illustrative purposes in the accompanying drawings, in which: Figure 1 shows the device for detecting a force and / or pressure according to the present invention in a first configuration;

[0051] Figure 2 shows the device in a second configuration;

[0052] Figure 3 shows a graph illustrating the variation in the electric field measured in a detection element of the device as a function of the distance between said detection element and a magnetic element of the device;

[0053] Figure 4 shows the device according to the present invention in the first configuration associated with a robot finger;

[0054] Figure 5 shows the device according to the present invention in the second configuration associated with a robot finger;

[0055] Figure 6 shows the device associated with an ultrasonic probe;

[0056] Figure 7 shows the device in the second configuration;

[0057] Figure 8 shows a different embodiment of the device.

[0058] Description of embodiments of the invention

[0059]

[0046] With particular reference to these figures, the device for detecting a force and / or pressure is indicated as a whole with 1 , which will be referred to as the device in the following description for simplicity.

[0060]

[0047] Device 1 comprises a first element 2 with magnetic characteristics. The first element 2 is in fact capable of generating a magnetic field.

[0061]

[0048] The first element 2 may be a permanent magnet or an electromagnet.

[0062]

[0049] Alternatively, the first element 2 may comprise magnetic components, such as magnetic particles or nanoplatelets.

[0063]

[0050] According to a preferred embodiment, the first element 2 is deformable and is preferably a magnetic elastomer.

[0064]

[0051] The magnetic elastomer may comprise magnetic particles or nanoplatelets.

[0065]

[0052] The first element 2 is configured to be mounted in a region that is generally subjected to forces during use, for example, on a finger of a robot 100 or the tip of a finger of a robot 100, as shown in Figures 4 and 5, or on an ultrasound probe 101 , as shown in Figure 6.

[0066]

[0053] The device 1 also comprises a second element 3 for detecting a force and / or pressure applied to the first element 2, which is spaced apart from the first element 2.

[0067]

[0054] The second element 3 comprises a casing 4 containing a liquid magnetoelectric material 5.

[0068]

[0055] In particular, the casing 4 contains a predetermined amount of liquid magnetoelectric material, which is determined based on the size and configuration of the casing.

[0069]

[0056] The casing 4 can be made of a rigid or deformable material. The casing 4 has a flattened shape. Alternatively, the casing 4 can have any shape suitable for association with the application site.

[0070]

[0057] Liquid magnetoelectric material 5 refers to a liquid material that exhibits a change in electrical characteristics when an applied magnetic field varies. The polarization of the liquid material can therefore be controlled by a magnetic field.

[0071]

[0058] Preferably, the liquid magnetoelectric material 5 also exhibits a variation in magnetic characteristics when an electric field is applied, i.e., the magnetization can be controlled by an electric field. Therefore, the liquid material exhibits both the direct magnetoelectric effect and the inverse magnetoelectric effect.

[0072]

[0059] The liquid magnetoelectric material 5 may comprise a plurality of magnetoelectric particles or crystals.

[0073]

[0060] A plurality of electrodes 6 are mounted on at least one surface of the casing 4 to detect a variation in the electrical characteristics of the liquid magnetoelectric material 5 following a variation in the magnetic field generated by the first element 2 when a force is applied to the first element 2.

[0074]

[0061] More specifically, the first element 2 has a first configuration (see Figures 1 and 4) in which it generates a first magnetic field distribution in the absence of an applied force, and a second configuration (see Figures 2 and 5) in which it generates a second magnetic field distribution. The variation in the magnetic field following the application of a force causes a variation in the electrical characteristics of the liquid magnetoelectric material 5 contained in the casing 4 of the second element 3, as shown in the graph in Figure 3.

[0075]

[0062] In the second configuration, the first element 2 is brought closer to or moved away from the second element 3. In particular, the first element 2 can be translated or rotated by the force applied to it and, as a result, the distance from the second element 3 is changed.

[0076]

[0063] Alternatively, or in conjunction with the change in distance from the second element 3, the first element 2 is deformed by the force applied. In the case of a deformable first element 2, when a force is applied, a change in shape occurs and, as a result, the density relative to the magnetic component of the first element 2 is modified.

[0077]

[0064] The deformed first element 2 generates a different magnetic field distribution than the magnetic field generated in the configuration where no force is applied. Both the change in distance between the first element 2 and the second element 3 and the change in density of the first element 2 result in a change in the magnetic field distribution.

[0078]

[0065] The first element 2 can be mobile and deformable, therefore, following the application of a force, it is moved closer to or further away from the second element 3 and is also deformed. Alternatively, the second element 2 can be deformable but fixed with respect to the second element 3, therefore, the applied force changes its shape. The second element 2 can be non-deformable but mobile upon application of a force.

[0079]

[0066] The graph shown in Figure 3 shows an electric field value measured at a point in the liquid magnetoelectric material 5 when the first element 2 is in the first configuration, at a predetermined distance d from the second element 3. The graph also shows an electric field value at a point in the liquid magnetoelectric material 5 when the first element 2 is in the second configuration, at a close distance di from the second element 3. The measured electric field value is different because the electrical characteristics of the liquid magnetoelectric material are modified when the first element 2 changes from the first configuration to the second configuration.

[0080]

[0067] The electrodes 6 are arranged on at least one surface of the casing 4 adjacent to each other to allow the detection of forces applied at a multiplicity of points independently. In essence, arranging the electrodes 6 adjacent to each other allows, by measuring the potential difference across the electrodes 6, the forces applied at points that are quite close to each other to be distinguished.

[0081]

[0068] According to one embodiment, the electrodes 6 are arranged to form at least one matrix.

[0082]

[0069] The electrodes 6 are made of a material with good electrical conductivity, such as gold or ITO (indium tin oxide).

[0083]

[0070] The electrodes 6 are connected to an electrical circuit, not shown in the figures, configured to process electrical signals detected by the electrodes 6 and obtain information about the force and / or pressure applied to the first element 2.

[0084]

[0071] The electrical signals include the voltage measured across at least one pair of electrodes 6.

[0085]

[0072] According to an advantageous aspect of the invention, the device 1 is also used as a transducer of electrical energy into mechanical energy by exploiting the inverse magnetoelectric effect of the magnetoelectric liquid material (see Figure 8).

[0086]

[0073] Device 1 has the same characteristics as the device described above, but the device is used as an actuator and / or as an acoustic wave generator.

[0087]

[0074] The application of a potential difference to the ends of the electrodes 6 of the second element 3 causes a variation in the magnetic field generated by the second element 3. The magnetic field generated by the second element 3 interacts with the first magnetic element 2, causing a deformation of the first element 2.

[0088]

[0075] The first element 2, by deforming, can be used as an actuator.

[0089]

[0076] The first element 2 can vibrate if a voltage that varies rapidly over time, i.e. , at a high frequency, is applied to the ends of the electrodes 6 of the second element 3. The first element 2, vibrating, generates acoustic waves. The frequency can have values in the range between 1 and 20 MHz.

[0090]

[0077] This aspect can be used, for example, in the field of diagnostic imaging. More specifically, the device according to this aspect can be used, for example, in ultrasound probes for sending acoustic waves as well as for receiving waves.

[0091]

[0078] The operation of the device for detecting a force and / or pressure is easily understood from the above description.

[0092]

[0079] When a force is applied to the first element 2 (see Figures 2 and 5), for example by an object coming into contact with the first element 2 or by an acoustic wave affecting the first element 2, the first element 2 is deformed and / or moved closer to or further away from the second element 3, and a change in the generated magnetic field occurs. The variation in the magnetic field causes a change in the electrical characteristics of the liquid magnetoelectric material 5, which is detected by the electrodes 6. The electrical circuit allows the value of the applied force to be obtained from the processed electrical signals.

[0093]

[0080] If device 1 is used as a transducer of electrical energy into mechanical energy, a potential difference is applied to the ends of electrodes 6, resulting in a change in the magnetic characteristics of the second element 3. The interaction of the magnetic field generated by the second element 3 with the first magnetic element 2 causes a deformation of the first element 2. If the interaction between the magnetic fields causes the first element 2 to vibrate, this element 2, vibrating, sends acoustic waves.

[0094]

[0081] The device according to the present invention achieves the purpose of being easily adaptable to spaces of different sizes and shapes thanks to the provision of an element comprising a magnetoelectric material in the liquid state. The liquid magnetoelectric material allows the casing to be given the shape most suitable for the application of the device. In particular, the provision of a liquid magnetoelectric material allows the device to be easily used in spaces of limited size, not only because the shape of the casing can be easily modified, but also because the variation in the electric field of the material following a variation in the magnetic field is detected by a simple circuit that can be miniaturized.

[0095]

[0082] A further advantage of the device is that it allows different ranges of force and / or pressure values to be measured, as it is sufficient to modify the stiffness of the first magnetic element. In this regard, it should be noted that the device is based on the ability of a force to generate a displacement of the first magnetic element and / or a deformation with a consequent variation in the distance from the second element and / or the density of the first element, and if the first element has greater stiffness, the force required to achieve a given displacement or deformation will be greater. Therefore, to establish the ranges of force values to be measured, it is possible to simply modify the stiffness of the first element. To modify the stiffness of the first element, a material with a different stiffness can be selected, or its thickness or geometry can be varied.

[0096]

[0083] It should also be noted that the electrodes distributed adjacent to each other on one or more surfaces of the casing of the second element allow forces at points close to each other to be measured independently, thus also discriminating local effects of the magnetic field.

[0097]

[0084] Finally, the device is durable because the first magnetic element, on which the forces act or which is capable of generating waves or which is used as an actuator, has a rather robust structure.

[0098]

[0085] The device described by way of example is susceptible to numerous modifications and variations depending on different requirements.

[0099]

[0086] In the practical implementation of the invention, the materials used, as well as the shape and dimensions, can be anything depending on the requirements.

[0100]

[0087] Where the technical characteristics mentioned in each claim are followed by reference marks, these reference marks have been included for the sole purpose of increasing the understanding of the claims and, consequently, they have no limiting value on the purpose of each element identified by way of example by these reference marks.

Claims

1. A device for detecting a force and / or pressure comprising a first element (2) having magnetic characteristics; a second element (3) for detecting a force and / or pressure applied to said first element (2), spaced apart from said first element (2), said second element (3) comprising a casing (4) containing a liquid magnetoelectric material (5) therein, said liquid magnetoelectric material (5) exhibiting a variation in electrical characteristics when an applied magnetic field varies, said second element (3) also comprising a plurality of electrodes (6), arranged on at least one surface of said casing (4), configured to detect said variation in the electrical characteristics of said liquid magnetoelectric material (5) following a variation in the magnetic field generated by said first element (2) upon application of a force to said first element (2).

2. The device of claim 1 , wherein said first element (2) has a first configuration, in which it generates a first magnetic field distribution in the absence of an applied force, and a second configuration, in which it generates a second magnetic field distribution, upon application of a force, said variation in magnetic field between said first configuration and said second configuration causing a variation in the electrical characteristics of said liquid magnetoelectric material (5).

3. The device of claim 2, wherein said first element (2), in said second configuration, is brought closer to said second element (3) or is spaced apart from said second element (3) upon application of said force, and / or is deformed as a result of the application of said force.

4. The device of claim 1 , 2 or 3, wherein it comprises an electrical circuit connected to said electrodes (6), said electrical circuit being configured to process electrical signals of said liquid magnetoelectric material (5) detected by said electrodes (6) and to derive information on the force and / or pressure applied to said first element (2).

5. The device of claim 4, wherein said electrical signals comprise the voltage across at least one pair of electrodes (6).

6. The device of any one of claims 1-5, wherein said plurality of electrodes (6) are distributed on said at least one surface of said casing (4) adjacent to each other so as to allow the detection of forces at a multiplicity of points independently.

7. The device of any one of the preceding claims, wherein said first element (2) is deformable.

8. The device of any one of the preceding claims, wherein said first element (2) is a magnetic elastomer.

9. The device of claim 8, wherein said magnetic elastomer comprises a plurality of magnetic components, preferably magnetic particles or nanoplatelets.

10. The device of any one of the preceding claims, wherein said liquid magnetoelectric material (5) comprises magnetoelectric particles or crystals.

11. The device of any one of the preceding claims, wherein said liquid magnetoelectric material (5) exhibits a variation in magnetic characteristics when an electric field is applied.

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