Cross-shaped three-dimensional force tactile sensor

Abstract

The utility model relates to a cross-shaped three-dimensional force touch sensor. The sensor comprises a contact, a base and four sensing units, the square base comprises a platform and a PCB (Printed Circuit Board); wherein a square groove is formed in the middle of the upper surface of the platform; the PCB is in a frame shape and covers the outer edge of the square groove. The structure of each sensing unit is composed of a TMR element, a vertical plate, a square permanent magnet and an iron gallium wire; the vertical plate is fixed in the middle of the inner wall of the square groove, and the TMR element is attached to the outer wall of the vertical plate; one end of the iron gallium wire passes through the through hole and is connected with the TMR element, and the other end is inserted into a circular hole of a pillar 4 of the contact. The four iron gallium wires of the four sensing units are jointly inserted into the four round holes of the contact pillar 4 to form a cross structure. The sensor provided by the utility model has the advantages of small overall size, high sensitivity and strong stability, and also shows good dynamic performance, and has short response time and recovery time.

Description

Technical Field

[0001] The utility model belongs to a three-dimensional force tactile sensor, in particular to a cross-shaped three-dimensional force tactile sensor based on an iron-gallium alloy. Background Art

[0002] Sensors are one of the important technologies that provide robots with external information. Compared with visual sensors, tactile sensors have significant advantages in human-computer interaction. With the advent of a variety of tactile sensors for measuring single-direction forces, the current research on tactile sensors has tended to obtain three-dimensional force information. The core components of the existing iron-gallium alloy three-dimensional force sensor (patent number "CN114136526A" a three-dimensional force tactile sensor based on the inverse effect of magnetostriction) are composed of iron-gallium wire and Hall elements. Four internal Hall elements and four external Hall elements are required to complete the magnetic field detection, realizing the simultaneous measurement of the direction and size of the three-dimensional force. However, due to the poor anti-interference ability of the Hall element, and the coupling between too many Hall elements and each unit, the performance of the sensor is affected, and the minimum size of the sensor is limited to a certain extent. Utility Model Content

[0003] In order to solve the problems of existing three-dimensional force tactile sensors with large size, low sensitivity and stability, the utility model provides a cross-shaped three-dimensional force tactile sensor based on iron-gallium alloy. In the sensor structure, only four sensing elements are needed, and the four sensing units are distributed crosswise around the contact. In the sensing unit, the TMR element is placed at the end of the iron-gallium wire to detect the magnitude and direction of the force of the sensing unit. Through the magnitude and difference of the output of the four sensing units, the three-dimensional force is decomposed on the X, Y, and Z axes to determine the magnitude and direction of the three-dimensional force. While having the advantages of small overall size, high sensitivity, and strong stability, the sensor of the utility model also exhibits good dynamic performance, with short response time and recovery time.

[0004] The technical solution of the utility model is:

[0005] A cross-shaped three-dimensional force tactile sensor, the sensor comprising a contact, a base and four sensing units;

[0006] The base comprises a platform and a PCB board; wherein a square groove is opened in the middle of the upper surface of the platform; the PCB board is frame-shaped and covers the outer edge of the square groove;

[0007] The contact comprises a support and a hemisphere; wherein the hemisphere is fixed on the support; the support is a cylinder, and four circular holes of equal height and evenly distributed on the circumference are opened on the side surface; the distance between the lower surface of the support and the upper surface of the square groove of the base is 1.5-2mm; the vertex of the hemisphere is 1.5-2mm higher than the highest point of the vertical plate;

[0008] The structure of each sensor unit consists of a TMR element, a vertical plate, a square permanent magnet, and an iron-gallium wire; the vertical plate is fixed to the middle of an inner wall of a square groove of the base, and the TMR element is attached to the outer wall of the vertical plate and fixed to the surface of the PCB board;

[0009] A first rectangular groove is formed in the middle and lower part of the inner side of the vertical plate; at the same time, a second rectangular groove is formed at the intersection of the upper surface of the vertical plate and the inner top, the first groove and the second groove have the same size and the same projection; a square permanent magnet is embedded in each of the first groove and the second groove; the square permanent magnet is embedded therein, and the N pole direction of the upper permanent magnet points to the contact, and the N pole direction of the lower permanent magnet is away from the contact;

[0010] A through hole is opened on the vertical plate at the midpoint of the two rectangular grooves; one end of the iron-gallium wire passes through the through hole and is connected to the TMR element, and the other end is inserted into the circular hole of the contact support; the four iron-gallium wires of the four sensor units are inserted into the four circular holes of the contact support together to form a horizontal, symmetrical cross structure.

[0011] The iron gallium wire composition is Fe 83 Ga 17 , diameter is 0.4~0.6mm;

[0012] The pillar is cylindrical, with a bottom diameter of 4 to 6 mm and a height of 3 to 5 mm;

[0013] The diameter of the hemisphere is consistent with the diameter of the bottom surface of the pillar;

[0014] The platform is a cube with a height of 3 to 5 mm and a side length of 24 to 26 mm;

[0015] The vertical plate is a rectangular parallelepiped with a height of 6 to 7 mm, a length equal to the height, and a width of 1.5 to 2 mm;

[0016] The platform, pillars, hemisphere and vertical plate are all made of epoxy resin;

[0017] The utility model has the following beneficial effects:

[0018] 1. The utility model is based on the magnetostrictive inverse effect of the iron-gallium alloy wire. The sensor can convert the force signal acting on the contact into an electrical signal. Based on the cross-shaped symmetrical distribution of the sensing unit, the hemispherical contact transmits the three-dimensional force signal to the sensing units at four different positions. By analyzing the output of the sensing units in different directions, the decoupling problem of the three-dimensional force can be intuitively solved, and the normal force and the tangential force can be distinguished;

[0019] 2. The utility model adopts TMR as the magnetic field measuring element, which is more stable than the traditional Hall element, and the sensing units are far apart, the number of TMRs is small, the coupling between elements is avoided, the structure is simple, and the measurement accuracy is improved.

[0020] 3. The three-dimensional force tactile sensor has excellent static force and dynamic force test performance. It can effectively measure the normal force of 0-6N and the tangential force of 0-3N. The sensor's normal force sensitivity is as high as 41.365mV / N, and the tangential force sensitivity is as high as 49.636mV / N. It has a short response time to dynamic excitation, with a response time of only 28ms and a recovery time of 30ms, which is less than the response time of human skin.

[0021] 4. The overall size of the sensor is only 25mm*25mm*8mm, which is small in size and easy to manufacture. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a structural diagram of a cross-shaped three-dimensional force tactile sensor based on an iron-gallium alloy;

[0023] Among them, 1-platform, 2-PCB board, 3-TMR element, 4-pillar, 5-hemisphere, 6-vertical plate, 7-square permanent magnet, 8-Fe-G wire;

[0024] Figure 2 This is a structural disassembly diagram of a cross-shaped three-dimensional force tactile sensor based on iron-gallium alloy;

[0025] Figure 3 It is a structural diagram of the sensing unit of a cross-shaped three-dimensional force tactile sensor based on an iron-gallium alloy;

[0026] Figure 4 It is the static force test output curve of the tactile sensor sensing unit;

[0027] Figure 5 It is the static normal force test output curve of the cross-shaped three-dimensional force tactile sensor;

[0028] Figure 6 It is the output curve of the static tangential force test in the x-axis direction of the cross-shaped three-dimensional force tactile sensor;

[0029] Figure 7 It is the static tangential force test output curve of the cross-shaped three-dimensional force tactile sensor in the y-axis direction;

[0030] Figure 8 It is the dynamic force test output curve of the cross-shaped three-dimensional force tactile sensor.

[0031] Fig. 9 This is the output curve of the dynamic force response time test of the cross-shaped three-dimensional force tactile sensor DETAILED DESCRIPTION

[0032] The present invention will be further explained in detail below in conjunction with the accompanying drawings.

[0033] The sensor of the utility model comprises a contact, a base and four sensing units; the four sensing units are opposite to each other in pairs, at right angles to each other, and are distributed on the base in a cross shape as a whole, and surround the contact;

[0034] The square base includes a platform 1 and a PCB board 2; wherein a square groove with a side length of 19 mm and a height of 2 mm is opened in the middle of the upper surface of the platform 1; the PCB board 2 is frame-shaped and completely overlaps with the remaining part of the upper surface of the platform 1;

[0035] The base has a height of 4 mm and a length of 25 mm.

[0036] The contact comprises a support 4 and a hemispherical body 5; wherein the upper surface of the support 4 is fixedly connected to the lower surface of the hemispherical body 5, and the two completely overlap; the hemispherical body 5 is used to receive pressure; the support 4 is a cylinder, and four circular holes of equal height and evenly distributed on the circumference are opened on the side (adjacent holes are at 90 degrees). To ensure that the contact transmits signals only through the iron-gallium wire after being stressed, and will not collide with other parts due to tilt or displacement, after the sensor is assembled, the distance between the lower surface of the support and the upper surface of the square groove of the base is 2mm, and at the same time, the vertex of the hemispherical body 5 is 2mm higher than the highest point of the vertical plate;

[0037] The structure of each sensor unit is as follows Figure 3 As shown, they are composed of a TMR element 3, a vertical plate 6, a square permanent magnet 7, and an iron-gallium wire 8; the vertical plate 6 is fixed to the middle of an inner wall of a square groove of the base, and the TMR element 3 is attached to the outer wall of the vertical plate 6 and fixed to the surface of the PCB board 2;

[0038] A first rectangular groove is formed in the middle and lower part of the inner side of the vertical plate 6; at the same time, a second rectangular groove is formed at the intersection of the upper surface and the inner top of the vertical plate 6, and the first groove and the second groove have the same size and the same projection; a square permanent magnet 7 is embedded in each of the first groove and the second groove;

[0039] A through hole is opened on the vertical plate 6 at the midpoint of the two rectangular grooves; one end of the iron gallium wire 8 passes through the through hole and is connected to the TMR element 3, and the other end is inserted into the circular hole of the contact support 4 to improve the sensitivity and stability of the sensor; the four iron gallium wires 8 of the four sensing units are inserted into the four circular holes of the contact support 4 together to form a horizontal, symmetrical cross structure.

[0040] The iron gallium wire 8 is composed of Fe 83 Ga 17, with a diameter of 0.5 mm and a length of 9 mm, arranged horizontally, with one end fixed to the through hole of the vertical plate 6 and the other end fixed to the circular hole on the side of the pillar 4;

[0041] The TMR element 3 is fixed on the PCB board 2, located at the rear side of the vertical board, and keeps contact with the end of the Fe-Ga wire 8, and its magnetic sensitivity direction points to the contact;

[0042] The square permanent magnet 7 is a cube with a length of 4 mm, a width of 1.1 mm, and a height of 0.6 mm, fixed in the groove of the vertical plate 6. There are two square permanent magnets on each vertical plate, and they are symmetrically placed on the upper and lower sides of the iron-gallium wire to provide a bias magnetic field; the N pole direction of the upper permanent magnet points to the contact, and the N pole direction of the lower permanent magnet is away from the contact;

[0043] The pillar has a diameter of 5 mm and a height of 4 mm;

[0044] The platform, pillars, hemisphere and vertical plate are all made of epoxy resin.

[0045] The working principle of the three-dimensional force tactile sensor of this embodiment is as follows:

[0046] When the contact is pushed by an unknown three-dimensional force, the lower support 4 tilts and drives one end of the Fe-G wire 8 to displace, causing the four Fe-G wires in four directions to deform to different degrees. Due to the inverse magnetostrictive effect, the magnetic field in the Fe-G wire changes, and the TMR element 3 outputs a corresponding electrical signal. The voltage output comparison of the TMR elements at four different positions represents the direction of the force, and the voltage value represents the magnitude of the force.

[0047] The output voltage signal is collected by a data acquisition card, and the size and direction of the three-dimensional force on the contact are solved by the corresponding algorithm.

[0048] Embodiment 1:

[0049] The static force characteristic test is performed on the cross-shaped three-dimensional force sensor unit. The main purpose of this embodiment is to determine the force measurement range, input-output relationship and static force sensitivity of the sensor unit.

[0050] Test platform construction: Assemble and fix the sensor unit with the help of a small PCB board and a rectangular platform, align the transmission rod of the digital push-pull dynamometer with the end of the iron-gallium wire of the sensor unit, apply normal force through the push-pull dynamometer, use a DC regulated power supply to power the TMR element, and connect the element output to the data acquisition card.

[0051] Experimental process and results: The step length is set to 0.25N, and a digital push-pull meter is used to apply vertical downward and vertical upward forces with a magnitude of 0-1.5N. Each time the external force is applied, the external force is maintained for a few seconds and then removed. The output voltage of the sensor unit is as follows: Figure 4 As shown, assuming that the vertical downward force is positive and the vertical upward force is negative, it can be seen from the figure that the output voltage of the sensor unit in the range of -1.5N to 1.5N shows a good linear relationship with the pressure, and the output voltages of the sensor unit for forces of equal magnitude and in different directions are opposite in positive and negative, and the absolute values ​​are roughly the same. The output voltage can remain stable under constant pressure and quickly returns to 0 after the external force is removed. The sensor unit has good static characteristics. When the pressure is 1.5N, the output voltage is 247mV, and the sensitivity of the sensor unit is 164.63mV / N.

[0052] Embodiment 2:

[0053] Test the output of the cross-shaped tactile sensor when a static three-dimensional force is applied. The main purpose of this embodiment is to test the sensor's recognition of the tangential force direction and the tangential force sensitivity, and to determine the relationship between the output voltage and the force.

[0054] Test platform construction: Assemble the three-dimensional force sensor and fix it on the angle table, place it on the base of the push-pull force gauge, align the transmission rod of the digital push-pull force gauge with the sensor contact, use a DC regulated power supply to power the TMR element, and connect the element output to the data acquisition.

[0055] Experimental process and results: Change the angle of the angle table to place the sensor horizontally, set the step length to 0.5N, use a digital push-pull gauge to apply a normal force of 0-6N, and the contact will apply force to the four sensor units. The output voltage is as follows: Figure 5 As shown in the figure, the output voltages of the four sensing units are basically the same, and the normal force and the output voltage have a good linear relationship within 0-6N. The normal force sensitivity of the sensor is 41.365mV / N. The angle of the angle table is changed to place the sensor vertically, and the step size is set to 0.5N. A tangential force of 0-3N is applied using a digital push-pull gauge. The direction of the tangential force is set from unit 3 to unit 1, and the direction is set to the X-axis direction. The contact applies force to the four sensing units. The iron-gallium wires of units 2 and 4 do not produce vertical deformation as torque, the iron-gallium wire of unit 1 produces downward deformation, and the iron-gallium wire of unit 3 produces upward deformation. The output voltage is as follows: Figure 6 As shown in the figure, the output voltage of unit 1 is positive, the output voltage of unit 3 is negative, and the outputs of unit 2 and unit 4 are basically 0; without changing the angle of the angle table, the sensor is rotated 90°, and the direction of the digital push-pull meter is directed from unit 4 to unit 2, with a tangential force of 0-3N, and this direction is set as the Y-axis direction. The contact applies force to the four sensor units, and the iron-gallium wires of units 1 and 3 do not produce vertical deformation as torque, the iron-gallium wire of unit 2 produces downward deformation, and the iron-gallium wire of unit 4 produces upward deformation. The output voltage is as follows Figure 6As shown, the output voltage of unit 2 is positive, and the output voltage of unit 4 is negative; the outputs of unit 1 and unit 3 are basically 0, and the tangential force sensitivity of the sensor is 49.636mV / N.

[0056] Embodiment 3:

[0057] Testing the dynamic force performance of the cross-shaped tactile sensor. The main purpose of this embodiment is to verify the dynamic performance of the sensor and preliminarily test the sensor response time and recovery time.

[0058] Test platform construction: The signal generator model is AFG2021-SC, the power amplifier model is MB500VI, and the exciter model is MODAL50. The signal output by the signal generator is transmitted to the exciter through the power amplifier and acts on the sensor contact through the driving rod. A DC regulated power supply is used to power the TMR element. The output voltage of the four TMR elements is collected through a data acquisition card with a sampling frequency of 1kHz and a sampling time of 1s, and the waveform is output to the computer.

[0059] Experimental process and results: A signal generator is used to output a 4Hz sine wave signal, which is transmitted to the exciter through a power amplifier and acts on the sensor contact through a driving rod. The output voltage of the four TMR elements is collected through a data acquisition card. The output voltage of the four units of the sensor is as follows: Figure 8 As shown, it can be seen that the output voltage of each unit is close to a sine wave, without obvious hysteresis, and changes synchronously, which verifies that the sensor has good dynamic performance; a signal generator is used to output a 6Hz square wave force signal, and a square wave force with a frequency of 6Hz and an amplitude of 3N is applied to the sensor contact through a signal amplifier. The output voltages of the four units are processed to obtain an average output voltage waveform. The waveform of one cycle is intercepted as shown in Fig. 9 As shown, it can be seen that the response time is 28ms and the recovery time is 30ms.

[0060] Matters not covered in this utility model are known technologies.

Claims

1. A cross-shaped three-dimensional force tactile sensor, Its characteristics are The sensor includes a contact, a base and four sensing units; The base comprises a platform and a PCB board; wherein a square groove is opened in the middle of the upper surface of the platform; the PCB board is frame-shaped and covers the outer edge of the square groove; The contact comprises a support and a hemisphere; wherein the hemisphere is fixed on the support; the support is a cylinder, and four circular holes of equal height and evenly distributed on the circumference are opened on the side surface; the distance between the lower surface of the support and the upper surface of the square groove of the base is 1.5-2mm; the vertex of the hemisphere is 1.5-2mm higher than the highest point of the vertical plate; The structure of each sensor unit consists of a TMR element, a vertical plate, a square permanent magnet, and an iron-gallium wire; the vertical plate is fixed to the middle of an inner wall of a square groove of the base, and the TMR element is attached to the outer wall of the vertical plate and fixed to the surface of the PCB board; A first rectangular groove is formed in the middle and lower part of the inner side of the vertical plate; at the same time, a second rectangular groove is formed at the intersection of the upper surface of the vertical plate and the inner top, the first groove and the second groove have the same size and the same projection; a square permanent magnet is embedded in each of the first groove and the second groove; the square permanent magnet is embedded therein, and the N pole direction of the upper permanent magnet points to the contact, and the N pole direction of the lower permanent magnet is away from the contact; A through hole is opened on the vertical plate at the midpoint of the two rectangular grooves; one end of the iron-gallium wire passes through the through hole and is connected to the TMR element, and the other end is inserted into the circular hole of the contact support; the four iron-gallium wires of the four sensor units are inserted into the four circular holes of the contact support together to form a horizontal, symmetrical cross structure.

2. The cross-shaped three-dimensional force tactile sensor according to claim 1, Its characteristics are The iron gallium wire composition is Fe 83 Ga 17 , diameter is 0.4~0.6mm; The pillar is cylindrical, with a bottom diameter of 4 to 6 mm and a height of 3 to 5 mm; The diameter of the hemisphere is consistent with the diameter of the bottom surface of the pillar; The platform is a cube with a height of 3 to 5 mm and a side length of 24 to 26 mm; The vertical plate is a rectangular parallelepiped with a height of 6 to 7 mm, a length equal to the height, and a width of 1.5 to 2 mm.

3. The cross-shaped three-dimensional force tactile sensor according to claim 1, Its characteristics are The platform, pillars, hemisphere and vertical plate are all made of epoxy resin.

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