TW202022335A - Multi-axis force sensor - Google Patents

Abstract

A multi-axis force sensor includes at least one capacitive force measuring unit and at least one magnetic field type force measuring unit. The capacitive force measuring unit comprises at least one pair of upper and lower electrode plates made of a flexible circuit board, and a silicone dielectric layer is disposed between the pair of electrode plates, and a capacitance reading IC; The magnetic field type force measuring unit comprises a magnet placed on the upper layer, a spacer rubber placed in the middle layer, and a magnetic field sensing IC disposed in the lower layer; the capacitive force measuring unit and the magnetic field type force measuring unit are stacked on each other to form a composite multi-axis force sensor.

Description

Multi-axis force sensor

The present invention relates to a multi-axis force sensor, in particular to a compressive shear force sensing device, which can be distinguished as a human body, a magnetically conductive object, or a non-magnetically conductive object by being close to the object to be measured, and it has Regarding a compression-shear force sensor that combines capacitive force measurement and magnetic field force measurement.

The increasing maturity of electronic component manufacturing technology has made wearable devices a topic of concern, and most of them have been developed into cross-field products integrating biomedical and electromechanical products. In recent years, the development of soft electronic technology has been changing rapidly, and related products have also come out one after another. Many of these designs use flexible pressure sensors to be used in different places. By wearing them at any time, continuous monitoring can be achieved without the limitation of space. Compared with pressure plate technology, it is more convenient and acceptable to general users. The degree is also higher. In this paper, the invention aims at the design and application of the combined use of magnetic sensing and capacitive sensors, and develops a multi-purpose sensor with pressure and shear stress sensing at the same time. The pressure sensor is mainly capacitive. The axial stress is based on magnetic sensing technology, and a multi-axis force sensor that can be applied to various situations is designed.

In TPTomo, WKWong, A. Schmitz, H. Kristanto, A. Sarazin, L. Jamone, S. Somlor, and S. Sugano, "A modular, distributed, soft, 3-axis sensor system for robot hands," 2016 IEEE-RAS Humanoids, pp.454-460.

T.P. Tomo, M. Regoli, A. Schmitz, L. Natale, H. Kristanto, S. Somlor, L. Jamone, G. Metta and S. Sugano "A New Silicone Structure for uSkin- a Soft, Distributed, Digital 3-axis Skin Sensor-and its Integration on the Humanoid Robot iCub” IEEE ROBOTICS AND AUTOMATION LETTERS, 2018.

TPTomo,A.Schmitz,WKWong,H.Kristanto,S.Somlor,J.Hwang,L.Jamone,and S.Sugano,"Covering a Robot Fingertip With uSkin: A Soft Electronic Skin With Distributed 3-Axis Force Sensitive Elements for Robot Hands,"IEEE ROBOTICS AND AUTOMATION,2018.

The electronic artificial skin-uSkin in the above study, an artificial human skin designed based on Melexis' MLX90393 chip, demonstrated a small 3-axis Hall-effect force sensor. The sensor is 3 x 3 x 1mm in size and has a digital output, which can be directly connected to the microcontroller via an I2C connection. The size of the 16 sensors is 26 x 27 x 6.05mm. High density is the advantage of this method, but once the sensor approaches a ferromagnetic metal object, it will completely lose its sensing ability.

The present invention improves the above-mentioned conventional design and overcomes the inductive interference of metal objects. It adds a soft sensor with capacitive sensing technology to design a capacitive and magnetic induction composite multi-axis force sensor, which combines two sensors. The advantages of the device achieve the desired effect in a complementary manner.

The invention also utilizes the human body capacitance to have a great influence on the capacitive sensor. There will be obvious changes in capacitance before the sensor is touched. After the capacitive sensor is placed on the magnetic sensor, the pressure and At the same time of shear stress, it detects whether the approach and contact are human or animal bodies. In addition, in the present invention, before the magnetic conductor touches the sensor, the magnetic induction value will change greatly due to the interference of the magnetic field, so it can be judged whether the approaching object is a magnetic conductor.

The invention provides a sensor with three-axis detection of pressure and shear at the same time, It has high resolution, high measurement range and waterproof capability.

The pressure shear force sensor of the present invention includes a double-layer flexible circuit board, a capacitance sensing IC, a magnetic field sensing IC, a cylindrical magnet, and a silicone rubber with a special mechanism design guide post. The double-layer flexible circuit board includes an upper layer capacitor electrode, a lower layer capacitor electrode, a magnetic field sensing peripheral circuit, a capacitive sensing peripheral circuit, a magnetic field sensing IC, and a capacitance sensing IC. After the upper capacitor electrode is bent 180 degrees, it is pasted on the upper layer of silicon gel of the special mechanism design guide post, and the silicon gel of the special structure design guide post is pasted on the lower capacitor electrode flexible circuit board. The cylindrical magnet is pasted on the back of the upper capacitor electrode flexible circuit board. Both the magnetic field sensing and capacitance sensing ICs are connected in parallel in the I2C transmission mode, and the communication address is used as the partition for data transmission. The sensor signal cable output terminal has four poles, from left to right are GND, VCC, SCL, SDA. The peripheral circuit of capacitive sensing has four passive components with a thickness higher than that of the capacitor and inductance ICs, which are respectively arranged in the four corners to protect the IC from external forces.

Through the magnetic field sensor, it has the ability to distinguish the strength of the three-axis magnetic force, analyze the variables that the magnet moves in space when subjected to pressure or shear force, and calculate the corresponding force value.

By calibrating the fixed control variable factors of the machine, measure the shear value of different directions and different forces at a fixed pressure value, record and find the corresponding relationship curve; then change the pressure value by fixing the shear value and record And find out the corresponding relationship curve; after finally consolidating multiple pressure and shear force corresponding curves, they can be integrated into the pressure and shear force corresponding curved surface. That is, the pressure and shear force comparison table of the sensor is completed, and then when measuring, the corresponding position of the current measurement value in the curve is obtained by interpolation to obtain the current strength and direction of the pressure and shear force.

The pressure sensor needs to be calibrated after manufacturing. The pressure value is converted into capacitance reading value through pressure calibration. Each calibrated pressure sensor is built into the look-up calibration table, and the capacitance value generated by the pressure when the sensor is used can be calculated to obtain the pressure value.

The sensor is coated with silicone resin to protect the IC from damage when external force is repeatedly applied during use.

The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the drawings are exemplary, and are intended to explain the present invention, and should not be construed as limiting the present invention.

100‧‧‧Cylindrical Magnet

110‧‧‧Spacer silicone with microstructure

120‧‧‧Sensor soft circuit board

120a‧‧‧Double-layer sensor flexible circuit board, the upper layer is the capacitor lower layer board, and the lower layer is the IC circuit wiring

120b‧‧‧Transmission capacitance value flexible circuit board circuit

120c‧‧‧Capacitor upper board

120d‧‧‧Sensor signal cable output terminal

130‧‧‧Magnetic field and capacitance sensing IC

Figure 1 is a perspective view of a compressive shear force sensor according to an embodiment of the present invention.

Figure 2 is an exploded perspective view of the components of the compressive shear force sensor of Figure 1.

Figure 3 is a three-dimensional view of the spacer silicone containing microstructures in Figure 2.

Figure 4 is a three-dimensional view of the batch test design before the calibration is completed.

Figure 5 is a flow chart of the method of measuring pressure shear force of the present invention.

Figure 6 is the bluetooth calibration machine design flow chart.

Figure 7 is the experimental data when the finger is close to the sensor and has not yet touched it.

Figure 8 is the experimental data when a finger applies pressure to the sensor.

Figure 9 is the experimental data when the magnetic conductor is close to the sensor and not in contact.

Figure 10 is the experimental data when a non-magnetic conductor applies a negative X-axis shear force to the sensor.

Figure 11 is the experimental data when a non-magnetic conductor applies a negative Y-axis shear force to the sensor.

Figure 12 is the experimental data when a non-magnetic conductor applies a positive X-axis shear force to the sensor.

Figure 13 is the experimental data when a non-magnetic conductor applies a positive Y-axis shear force to the sensor.

Figure 14 is when the finger is close to the sensor without touching the sensor, moving from the first quadrant to the fourth quadrant in sequence The experimental data.

Figure 15 shows the calibration of a sensor in the three-axis direction, and then the relationship is created as a table.

In order to better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the drawings show exemplary embodiments of the present invention, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

Figure 1 shows the complete appearance of the sensor of the present invention. When the sensor is pressed by the Z axis, the cylindrical magnet 100 and the upper layer 120c of the capacitor electrode are squeezed and move downward; by the silicone dielectric with high resilience The layer 110 (can be regarded as a spring) controls the distance between the cylindrical magnet 100 and the magnetic field sensing IC 130 and the distance between the lower layer 120a of the capacitor electrode after the force is applied, and changes the reading value of the capacitor and the magnetic field sensing IC to calculate the pressure received . In addition, when the sensor is subjected to X-axis and Y-axis shear forces, the cylindrical magnet 100 and the upper layer 120c of the capacitor electrode will be horizontally displaced, so that the distance relationship between the cylindrical magnet 100 and the magnetic field sensing IC 130 changes, changing the magnetic sensor The reading value of X-axis, Y-axis and Z-axis can be converted into shear force.

Figure 2 shows the sensor combination method of the present invention, the double-layer sensor flexible circuit board 120a (the upper layer is the lower capacitor board, and the lower layer is the IC circuit wiring), the transmission capacitance value flexible circuit board 120b, and the capacitor upper board 120c It is an integrated flexible circuit board, and the upper and lower capacitor circuits are connected by the transmission capacitance value flexible circuit board circuit 120b. The combination method is to attach the silicon dielectric layer 110 to the double-layer sensor flexible circuit board 120a, and then reflex the upper capacitor electrode 120c by 180 degrees and stick it on the silicon dielectric layer 110, and then fix the cylindrical magnet 100 on the On the upper capacitor electrode 120c.

Figure 3 shows the microstructure on the spacer silicon (dielectric layer) 110 designed by the present invention. The silicon dielectric layer has cylindrical particles or cylindrical and cone-shaped particles on the plane. This design can increase The sensitivity of the multi-axis force sensor of the present invention and a large dynamic range (dynamic range), whether for a capacitive force sensing unit or a three-axis magnetic field type force sensing unit, can adjust its spring constant as required .

Fig. 4 shows that the present invention gathers eight sensors into a panel before calibration, concentrates the signals in one cable, and then cuts them separately after calibration. In the design of the present invention, an I2C multiplexer is set in the IC circuit, and 8 or more sensors are calibrated at a time through address jump. The multiplexer receives 8 sets of sensor data at the same time and transmits it to the calibration via the Bluetooth module machine. This method can overcome the problem of insufficient sensor production capacity. In order to use the I2C connection method, a commercial capacitance-to-digital converter IC with I2C channels was also selected.

Figure 5 shows the process of the sensor sensing method of the present invention. The sensor is subjected to pressure to change the capacitance value of the variable capacitor. The capacitance value is read through the capacitance sensing IC, and the current value is obtained after querying the calibration pressure capacitance relationship table and interpolation. The pressure value. The sensor is subjected to shear force to change the relative position of the magnet and the magnetic field sensing IC. The three-axis magnetic field strength is read through the magnetic field sensing IC, and the pressure value obtained by the capacitor is used as a reference. The current is obtained by querying the correction shear magnetic field relationship table after interpolation The value of shear force.

Figure 6 shows the flow chart of the design of the calibration machine of the present invention. After placing the sensor to be calibrated into the calibration machine, it is connected with Bluetooth, and through automatic programming, the received pressure and shear force are different. The bluetooth readings are recorded as a table and stored after the calibration is completed.

When the sensor of this invention is not affected by external forces, the readings are stable within 0.03% of the error.

As shown in Figure 7, when the human body (the finger in this experiment) slowly approaches the sensor When the distance is close to 1 mm and then left, the value of the capacitive sensor increases significantly by 30%, and the three axes of the magnetic field sensor IC remain unchanged. The reason is that the capacitance of the human body will interfere with the capacitance sensor.

As shown in Figure 8, the finger continues to apply pressure to the sensor, and the value of the magnetic sensor also responds significantly; when the part of the finger that is not touching the sensor is enlarged, the effect of capacitance close to the human body can be clearly distinguished.

The distance between the non-magnetic object and the sensor is about 1mm, and the reading values of capacitance and magnetic induction remain unchanged. Non-permeable objects continue to apply pressure to the sensor, and capacitance and magnetic sensing values also have significant responses. Figure 9 shows that when a magnetically conductive object approaches the sensor by about 1 mm, the magnetic sensor is significantly affected by the magnetic field, while the capacitive sensor has a lower response. Through the above experiments, this sensor can distinguish between the human body, magnetic or non-magnetic conductors by approaching objects.

As shown in Figure 10, a non-magnetic object is subjected to shear stress in the negative X-axis direction, and it can be seen that the X-axis magnetic sensing value increases, the Y-axis magnetic sensing value decreases, and the Z-axis magnetic sensing value decreases . As shown in Figure 11, when a non-magnetic object is subjected to shear stress in the negative direction of the Y axis, the X-axis magnetic sensing value does not change significantly, the Y-axis magnetic sensing value rises, and the Z-axis magnetic sensing value rises. As shown in Figure 12, a non-magnetic object is subjected to shear stress in the positive X-axis direction, the X-axis magnetic sensing value decreases, the Y-axis magnetic sensing value increases, and the Z-axis magnetic sensing value increases. As shown in Figure 13, when a non-magnetic object is subjected to shear stress in the positive direction of the Y axis, the X-axis magnetic sensing value drops, the Y-axis magnetic sensing value drops, and the Z-axis magnetic sensing value drops. From the above two experiments, the direction of the shear force can be identified by the trend change of the triaxial value.

As shown in Figure 14, as the finger moves in the four quadrants, it can be seen that the four corresponding channel values change accordingly.

Three results were obtained from such experiments: 1. When the magnetic induction did not change, the permittivity first changed, and it was judged as a human touch. 2. When the capacitance does not change, the permittivity first changes, And judge whether the magnetic conductor is in contact. 3. When the capacitance and magnetic induction change at the same time, it is judged that the non-magnetic conductor is in contact.

The sensor of the present invention is calibrated in a way that a connecting board with 8 sensors can be placed in the shear force calibration machine at a time, and 8 sensors of 7 channels are connected in Bluetooth mode at the same time ( Capacitance sensing value has 4 channels and magnetic induction value). Perform three-axis calibration on a sensor. Apply a positive pressure of 0~0.4bar to the sensor, and at the same time apply a shear force of 0~0.4bar to the sensor, and record the readings of the capacitance and magnetic sensor, each time interval of 0.02bar, create a table, As shown in Figure 15. The current pressure will be measured by the capacitive sensor, the shear correction will be uncoupled from the three-axis readings of the magnetic sensor, and the corresponding shear force will be calculated. When using the sensor in the future, you can query this table and perform interpolation to convert the pressure applied to the sensor.

The embodiment of the present invention describes the design of a composite multi-axis force sensor with four capacitive effect sensors and a set of three-axis magnetic effect sensors, which use the change of the electrode gap to detect the positive force it receives . Apply hard silicone on the IC surface of the sensor to prevent external damage during operation. By bringing the human body or object into contact with the proposed sensor, the contact is the human body, a magnetic conductor or a non-magnetic conductor. Tests show that when the human body is in contact, the capacitive sensor first detects the change in capacitance; when the magnetic conductor is in contact, the triaxial magnetic effect sensor first detects the change in the magnetic field; when the non-magnetic conductor is in contact, the capacitive sensor and The three-axis magnetic effect sensor simultaneously senses the detected changes.

Although the foregoing embodiment describes the design of a multi-axis force sensor with four capacitive effect force sensors and a set of three-axis magnetic effect sensors, it can also be changed to a capacitive effect force sensor and The design of a composite multi-axis force sensor with a set of three-axis magnetic effect sensors.

To sum up, in the present invention, the distance between the magnet and the magnetic sensor is changed based on the plate capacitor, and the structure of the dielectric material is changed to produce a sensor with good performance, which is characterized by low cost. The process is simple and easy to customize. Generated as described above for It measures the forward pressure of the artificial skin, and can also measure the shear stress by the horizontal movement of the magnet. All the above-mentioned sensors can be calibrated by a self-made calibration machine and their characteristics can be measured. After performing the calibration, measure the shear force through the self-made machine and equipment, and measure the magnitude and direction of the shear force by calibrating the built-in meter, and display the pressure information on the mobile phone instantly, which increases the versatility and applicability.

The present invention is described with reference to flowcharts and/or block diagrams of methods, equipment (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and/or block in the flowchart and/or block diagram, and the combination of processes and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, dedicated computers, embedded processors, or other programmable data processing equipment to generate a machine that can be executed by the processor of the computer or other programmable data processing equipment A device for realizing the functions specified in one flow or multiple flows in the flowchart and/or one block or multiple blocks in the block diagram is generated.

It should be noted that in the claims, any reference signs located between parentheses should not be constructed to limit the claims. The word "comprising" does not exclude the presence of parts or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of multiple such components. The present invention can be realized by means of hardware including a number of different components and by means of a suitably programmed computer. In the unit claims enumerating several devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third does not indicate any order. These words can be interpreted as names.

Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. change. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

In the present invention, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection , Or integrated; it can be a mechanical connection, or it can be an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

In the present invention, unless otherwise clearly defined and defined, the "on" or "under" of the first feature on the second feature may be in direct contact with the first and second features, or the first and second features may be indirectly through an intermediary. contact. Moreover, the "above", "above" and "above" of the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the level of the first feature is higher than the second feature. The “below”, “below” and “below” of the second feature of the first feature may mean that the first feature is directly below or obliquely below the second feature, or it simply means that the level of the first feature is smaller than the second feature.

In the description of this specification, descriptions with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean specific features described in conjunction with the embodiment or example , Structure, materials or characteristics are included in this In at least one embodiment or example. In this specification, the schematic representations of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. In addition, without contradicting each other, those skilled in the art may combine and combine different embodiments or examples and features of the different embodiments or examples described in this specification.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be construed as limitations to the present invention, and those of ordinary skill in the art can understand the above within the scope of the present invention. The embodiments are changed, modified, replaced, and modified.

100‧‧‧Cylindrical Magnet

110‧‧‧Spacer silicone with microstructure

120‧‧‧Sensor soft circuit board

120a‧‧‧Double-layer sensor flexible circuit board, the upper layer is the capacitor lower layer board, and the lower layer is the IC circuit wiring

120b‧‧‧Transmission capacitance value flexible circuit board circuit

120c‧‧‧Capacitor upper board

120d‧‧‧Sensor signal cable output terminal

130‧‧‧Magnetic field and capacitance sensing IC

Claims (11)

A multi-axis force sensor includes at least one capacitive force measuring unit, including at least a pair of upper and lower electrode plates made of flexible circuit boards, and a variable capacitor composed of spacer silicone is placed between the pair of electrode plates; A capacitive reading IC electrically connected to the upper and lower electrode plates; and at least one magnetic field type force measuring unit, including a magnet placed on the upper layer, a spacer silicone placed on the middle layer, and a magnetic field sensing IC placed on the lower layer; Among them, the spacing silicone of the capacitive force measuring unit is used as the dielectric layer and the elastic layer, and the spacing silicone of the magnetic field type force measuring unit is used as the elastic layer; wherein, the capacitive force measuring unit and the magnetic field type force measuring unit are stacked to form a composite The force sensor is a multi-axis force sensor that can be combined with the pressure of the capacitive force measuring unit at the same time. The multi-axis force sensor according to item 1 of the scope of patent application is characterized in that the capacitive force measuring unit is mainly used to measure pressure. The multi-axis force sensor according to item 1 of the scope of patent application is characterized in that the magnetic field type force measuring unit is mainly used to simultaneously measure pressure and shear force. The multi-axis force sensor according to item 1 of the scope of patent application is characterized in that the spacer silicone is shared by the capacitive force measuring unit and the magnetic field type force measuring unit. The multi-axis force sensor according to item 1 of the scope of patent application is characterized in that the capacitive force measuring unit and the magnetic field force measuring unit are superimposed in a way that (1) a magnet is from top to bottom , (2) Upper electrode plate, (3) Spacer silicon gel, (4) Lower electrode plate, (5) Substrate containing magnetic field sensing IC and capacitance reading IC. The multi-axis force sensor according to item 1 of the scope of patent application, wherein the capacitance reading IC and the magnetic field sensing IC are further electrically connected to a microcontroller or a wireless communication module with a microcontroller connection. The multi-axis force sensor according to item 1 of the scope of patent application, characterized in that the sensor can further detect whether the object approaching or in contact is a human or animal body; The multi-axis force sensor according to item 1 of the scope of patent application is characterized in that the sensor can further detect whether the contacted object is a magnetic conductor or a ferromagnetic material. The multi-axis force sensor according to items 1 and 5 of the scope of patent application is characterized in that the spacer silicone has a microstructure design on the plane, which can increase the force measurement sensitivity and the dynamic range (dynamic range). A multi-axis force sensor includes at least one capacitive force measuring unit, including at least a pair of upper and lower electrode plates made of flexible circuit boards, and a variable capacitor composed of spacer silicone is placed between the pair of electrode plates; A capacitive reading IC is electrically connected to the upper and lower electrode plates; the spacer silicon is used as the dielectric layer and the elastic layer, and has a microstructure design on the plane, which can increase the force measurement sensitivity and dynamic range (dynamic range). A multi-axis force sensor includes at least one magnetic field force measuring unit, including a magnet placed on the upper layer, a spacer silicone placed on the middle layer, and a magnetic field sensing IC placed on the lower layer; wherein the spacer silicone serves as an elastic layer, It has a micro-structure design on the plane, which can increase the force measurement sensitivity and dynamic range.

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