An electrostatic underwater three-dimensional force sensor and a tactile detection method

Abstract

The application discloses a kind of electrically isolated underwater three-dimensional force sensors and tactile detection methods.The device includes: upper protective shell and lower protective shell are positioned by shell positioning groove and positioning block clamping positioning, elastic pressing block top surface is equipped with force transmission protrusion, elastic pressing block bottom surface is equipped with contact protrusion, and flexible electrode is arranged below elastic pressing block.The method includes: contact protrusion in elastic pressing block and independent electrode in flexible electrode constitute a normal force detection unit, four distributed normal force units form a three-dimensional force unit, and the size and direction of three-dimensional force can be decoupled by comparing the size of normal force in four directions.The application increases the area ratio of common electrode and independent electrode to improve sensitivity, and the underwater three-dimensional force sensor has good packaging, can be used in underwater environment with high water pressure and water pressure change, realizes underwater three-dimensional force detection while having high sensitivity.

Description

Technical Field

[0001] This invention relates to a sensor in the field of underwater robot technology, and in particular to an ionized underwater three-dimensional force sensor and a tactile detection method. Background Technology

[0002] With the depletion of land resources and the increasing difficulty of extraction, shifting the focus of resource development to the ocean will be a future trend. The development of underwater robotics technology has made using robots to replace divers for underwater facility operations and inspections a highly efficient and low-cost solution. However, in the actual operation of underwater robots, there is often insufficient or even missing force feedback information, which may lead to misjudgment of the operating force by the operator, resulting in operational failure. Therefore, integrating a tactile sensing system into the end effector of an underwater robot helps the operator obtain tactile information from the scene, effectively improving the success rate of underwater operations.

[0003] Tactile sensors are the source of tactile information from the outside world and the core of tactile sensing systems. Currently, most tactile sensors are used in air environments, with few suitable for underwater applications. Underwater applications of tactile sensors face numerous challenges, such as waterproofing and water pressure. Most sensing principles fail or experience a significant performance degradation in a water environment. Sealing to isolate the sensor from the water's influence is difficult to address the issues of high water pressure and pressure variations at different depths. This presents a dilemma in underwater tactile sensor research.

[0004] Chinese National Invention Patent (Publication No. CN112729662B) discloses an underwater tactile sensor and its fabrication method. This sensor also uses the ionization principle as its sensing principle, but its electrode design employs an interdigitated electrode structure with similar electrode areas, which is detrimental to improving the sensitivity of ionization sensing. Furthermore, this sensor can only detect normal force signals and cannot achieve three-dimensional force detection. It also lacks effective packaging, making it difficult to apply in practical scenarios. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention provides an ionized underwater three-dimensional force sensor and a tactile detection method. This invention solves the problems of most sensors failing or experiencing significant performance degradation in aquatic environments, and the difficulty in addressing high water pressure and water pressure variations at different depths when sealing is used to isolate the sensor from the influence of the aquatic environment.

[0006] The technical solution adopted in this invention is:

[0007] I. An ionized underwater three-dimensional force sensor:

[0008] It includes an upper protective shell, an elastic pressure block, a flexible electrode, and a lower protective shell;

[0009] The upper protective shell has a positioning groove at the bottom of its outer circumference, and the lower protective shell has a positioning block on its inner wall. The upper and lower protective shells are locked in place by the positioning groove and the positioning block. A limiting frame is provided in the middle of the upper protective shell. The elastic pressure block has a limiting block on its outer circumference. The elastic pressure block is fixed by being embedded in the limiting frame by the limiting block. The top surface of the elastic pressure block has a force-transmitting protrusion, and the bottom surface of the elastic pressure block has four hemispherical contact protrusions. A flexible electrode is horizontally arranged below the elastic pressure block and is fixed on the lower protective shell.

[0010] The underwater three-dimensional force sensor is placed in an ion carrier. The ion carrier enters the underwater three-dimensional force sensor through an exhaust hole on the top surface of the upper protective shell and then connects to the flexible electrode.

[0011] The exhaust port is strip-shaped, which helps to expel internal gas when the underwater three-dimensional force sensor is submerged in the ion carrier. Residual gas inside the sensor can adversely affect its performance.

[0012] The ion carrier is water.

[0013] The flexible electrode includes a flexible substrate, a front electrode, and a back electrode; the front electrode is distributed on the upper surface of the flexible substrate near the contact protrusion, and the back electrode is distributed on the lower surface of the flexible substrate away from the contact protrusion.

[0014] The flexible electrode has an electrode positioning groove on its outer peripheral surface, and the flexible electrode and the lower protective shell are clamped and positioned by the electrode positioning groove and the positioning block.

[0015] The front electrode includes a common electrode and individual electrodes;

[0016] The common electrode is distributed on the upper surface of the flexible substrate and has multiple annular hollow portions. The independent electrodes are distributed in a 2*2 array on the upper surface of the flexible substrate and located in the hollow portions of the common electrode. Each contact protrusion and its corresponding independent electrode are arranged coaxially. The independent electrodes and the common electrode are not connected. Both the independent electrodes and the common electrode are electrically connected to an external measurement circuit through external leads. The contact protrusions do not contact the common electrode. The front electrode is in contact with the ion carrier. The back electrode is insulated and sealed except for the external leads. The front electrode and the back electrode are connected and conductive through a through hole opened at the end of the back electrode.

[0017] The circuit between the flexible electrode and the external ion carrier is equivalent to the following circuit:

[0018] Including fixed capacitor C dA Variable capacitor C dB Capacitor C AB Electrode resistance RA Electrode resistance R B Resistance R L impedance Z fA and impedance Z fB ;

[0019] The capacitance formed between the common electrode and the ion carrier is equivalent to a fixed capacitance C. dA The capacitance formed between the independent electrode and the ion carrier is equivalent to a variable capacitance C. dB The inter-plate capacitance between the common electrode and the independent electrode is equivalent to capacitance C. AB The resistance of the individual electrode itself and the resistance between the individual electrode and the measuring circuit are both equivalent to the electrode resistance R. A The resistance of the common electrode itself and the resistance between the common electrode and the measuring circuit are both equivalent to the electrode resistance R. B The resistance of the ion carrier between the common electrode and the independent electrode is equivalent to the resistance R. L The Faraday impedance generated by the electrochemical reaction at the common electrode is equivalent to impedance Z. fA The Faraday impedance generated by the electrochemical reaction at the independent electrode is equivalent to impedance Z. fB ;

[0020] The electrode resistance R A Measurement circuit, electrode resistance R B and capacitor C AB The fixed capacitor C is connected in series. dA Resistance R L and variable capacitor C dB After being connected in series with capacitor C AB Parallel connection, the impedance Z fA Connected in parallel to the fixed capacitor C dA The impedance Z fB Connected in parallel to the variable capacitor C dB .

[0021] The outer circumferential surface of the upper protective shell is provided with a fixing threaded hole, and the outer circumferential surface of the lower protective shell is provided with a fixing through hole. The upper and lower protective shells are fixedly connected by screws passing through the fixing threaded hole and the fixing through hole respectively. The diameter of the fixing through hole is slightly larger than the outer diameter of the screw to facilitate the screw to enter and cooperate with the fixing threaded hole. The vent holes are circumferentially spaced on the top surface of the upper protective shell, and a handle is fixedly installed on the outer wall of the upper protective shell.

[0022] Both the upper and lower protective shells are made of stainless steel, which has good corrosion resistance underwater. The elastic pressure block is made of polydimethylsiloxane, which has good elasticity, can quickly recover after unloading, and is not prone to plastic deformation. When the force transmission protrusion is subjected to external force, it can transmit the force to the contact protrusion, causing a change in the contact area between the contact protrusion and the independent electrode. The flexible substrate is an insulating polyimide film, and both the front and back electrodes are gold-plated electrodes, which have good corrosion resistance underwater.

[0023] II. Tactile Detection Methods of Three-Dimensional Force Sensors:

[0024] 1) A three-dimensional force sensor is placed in an ion carrier. The ion carrier enters the underwater three-dimensional force sensor through an exhaust port and is then electrically connected to the front electrode. Each contact protrusion and its corresponding independent electrode form a normal force unit. When an external force F is applied to a force-transmitting protrusion, the force F is transmitted to the contact protrusions of each normal force unit. After being subjected to the external force F, the contact protrusions of each normal force unit are pressed down, increasing the contact area between the contact protrusion and the independent electrode. This reduces the contact area between the ion carrier and the independent electrode, thereby affecting the equivalent variable capacitance C between the ion carrier and the independent electrode. dB The capacitance value ultimately changes the capacitance value of the normal force element;

[0025] 2) By measuring the capacitance values ​​of the four normal force units, the force on the contact protrusion of each normal force unit is calculated based on the pre-calibrated mapping relationship obtained by the capacitance value of each normal force unit. Finally, the magnitude and direction of the external force F are obtained by decoupling calculation through a three-dimensional force decoupling model.

[0026] Since the sensor does not contain ionic materials, it must first be immersed in water to introduce water as an ion carrier into the sensor for it to function properly. Based on the designed dimensions, after the sensor is assembled, the limiting frame compresses the limiting block, subjecting the elastic block to pre-pressure in the initial stage. This pre-pressure helps stabilize the sensing signal in the initial stage. Because the density of the elastic block's material, polydimethylsiloxane, is close to that of water, its gravity and buoyancy can be considered to cancel each other out, and the sensing signal is only related to the external load.

[0027] Because of C AB Much smaller than C dA C dB Furthermore, the electrochemical reaction is weak, and the Faraday impedance can be ignored. In practice, the measured impedance can be equivalent to R. A C dA R L C dB R B The series connection. C dA C dBThe value of C is mainly positively correlated with the contact area between the electrode and the ion carrier. In this invention, the contact area between the common electrode and the ion carrier remains constant, while the contact area between the independent electrode and the ion carrier changes with the force applied to the elastic block. Therefore, C dA For a fixed capacitor, C dB For a variable capacitor, the measured impedance signal is given by C. dB The decision is made. In a circuit with two capacitors connected in series, the equivalent series capacitance is more significantly affected by the smaller capacitor, therefore C... dB The smaller the value, the greater the impact on the measurement results when it changes, which means that the sensor is more sensitive. Therefore, in this invention, the area of ​​the independent electrode is much smaller than that of the common electrode, while the contact area between the common electrode and the ion carrier remains unchanged.

[0028] This invention uses fixed and variable capacitors as sensing signals. The contact area between the electrode and the ion carrier is positively correlated. By correlating this contact area with the external load, tactile information can be detected. An open sensor structure is adopted to balance the water pressure inside and outside the sensor, avoiding the influence of high water pressure and water pressure changes on the sensing. By incorporating the water environment into the sensor's structural design and using the measurement results of four normal force units to reflect the magnitude and direction of the external three-dimensional force, this invention solves the problem that most sensors fail or their performance deteriorates significantly in a water environment. Sealing to isolate the influence of the water environment is difficult to solve the problem of high water pressure and water pressure changes at different depths.

[0029] The beneficial effects of this invention are:

[0030] 1) This invention uses the principle of ionization to design an underwater three-dimensional force sensor, incorporating the water environment into the sensor's structural design. The sensor is unsealed, and the water pressure is balanced inside and outside, which can avoid the impact of high water pressure and water pressure changes on the sensing performance.

[0031] 2) The present invention adopts a design of common electrode and independent electrode in the design of flexible circuit, which has good anti-interference ability, and improves the sensitivity of sensor by the large area ratio of common electrode to independent electrode.

[0032] 3) This invention utilizes the measurement results of four normal force units to reflect the magnitude and direction of the external three-dimensional force through the structural design of the elastic pressure block. The detection of three-dimensional force can be achieved through decoupling.

[0033] 4) The sensor of this invention has good packaging, which can protect the sensor from external interference when working in harsh water environments, and has good underwater stability and practicality. Attached Figure Description

[0034] Figure 1 This is a schematic diagram showing the disassembled structure of the sensor of the present invention.

[0035] Figure 2 This is a schematic diagram of the structure of the protective shell on the sensor of the present invention.

[0036] Figure 3 These are side and bottom views of the sensor elastic pressure block of the present invention.

[0037] Figure 4 These are the front and back sides of the flexible electrode of the sensor of this invention.

[0038] Figure 5 This is a schematic diagram of the structure of the lower protective shell of the sensor of the present invention.

[0039] Figure 6 This is the equivalent circuit diagram of the sensor normal force unit of the present invention.

[0040] Figure 7 This is a schematic diagram of the three-dimensional force detection principle of the sensor of the present invention.

[0041] In the diagram: 1. Upper protective shell, 2. Elastic pressure block, 3. Flexible electrode, 4. Lower protective shell, 11. Fixed threaded hole, 12. Shell positioning groove, 13. Vent hole, 14. Limiting frame, 15. Handle, 21. Force transmission protrusion, 22. Limiting block, 23. Contact protrusion, 31. Flexible substrate, 321. Common electrode, 322. Independent electrode, 33. Back electrode, 34. Electrode positioning groove, 35. Through hole, 41. Positioning block, 42. Fixed through hole. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 1 , Figure 2 As shown, the sensor is cylindrical with a maximum diameter of 10.5 mm and a height of 3 mm. The sensor includes an upper protective shell 1, an elastic pressure block 2, a flexible electrode 3, and a lower protective shell 4. A shell positioning groove 12 is provided at the bottom of the outer circumference of the upper protective shell 1, and a positioning block 41 is provided on the inner wall of the lower protective shell 4. The upper and lower protective shells 1 and 4 are locked in place by the shell positioning groove 12 and the positioning block 41. A limit frame 14 is provided in the middle of the upper protective shell 1. Figure 3 As shown, a limiting block 22 is provided on the outer periphery of the elastic pressure block 2. The limiting block 22 is a thin cylinder with a size larger than the limiting frame 14 and a diameter of 7mm. It is used to prevent the elastic pressure block 2 from falling out of the sensor. The elastic pressure block 2 can be embedded in the limiting frame 14. The shape of the limiting frame 14 is designed as a truncated circle rather than a complete circle, with a diameter of 6mm. The purpose is to prevent the elastic pressure block 2 from rotating around the axis during the force process, which would cause the relative position of the contact protrusion 23 and the independent electrode 322 to shift, resulting in a change in sensor performance.

[0044] The outer circumferential surface of the upper protective shell 1 is provided with a fixing threaded hole 11, such as Figure 5 As shown, a fixing through hole 42 is provided on the outer peripheral surface of the lower protective shell 4. The upper protective shell 1 and the lower protective shell 4 are fixedly connected by screws passing through the fixing threaded hole 11 and the fixing through hole 42 respectively. The diameter of the fixing through hole 42 is slightly larger than the outer diameter of the screw, which facilitates the screw to enter and cooperate with the fixing threaded hole 11. The top surface of the upper protective shell 1 is provided with vent holes 13 spaced apart in the circumferential direction. The vent holes 13 are strip-shaped, which helps to expel the internal gas when the sensor is submerged in water. The gas remaining inside the sensor will have an adverse effect on the sensor performance. A handle 15 is fixedly installed on the outer wall of the upper protective shell 1. A flexible electrode 3 is horizontally arranged below the elastic pressure block 2. The flexible electrode 3 is horizontally fixed on the lower protective shell 4. An electrode positioning groove 34 is provided on the outer peripheral surface of the flexible electrode 3. The flexible electrode 3 and the lower protective shell 4 are clamped and positioned by the electrode positioning groove 34 and the positioning block 41.

[0045] The three-dimensional force sensor is placed in an ion carrier, i.e., in water. Water enters the underwater three-dimensional force sensor through the vent 13 and then connects to the flexible electrode 3.

[0046] like Figure 3 As shown, the top surface of the elastic block 2 is provided with a force transmission protrusion 21, and the bottom surface of the elastic block 2 is provided with four hemispherical contact protrusions 23. The force transmission protrusion 21 is used to introduce external load into the sensor, with a diameter of 6mm and a height of 2mm for the protrusion exposed from the sensor.

[0047] The elastic block 2 has four contact protrusions 23, which are symmetrically distributed in four directions below the elastic block 2. After the sensor is assembled, each contact protrusion 23 is located directly above the independent electrode 322, and the two are coaxial. The contact protrusion 23 is hemispherical in shape and has a diameter of 2mm.

[0048] like Figure 4 As shown, the flexible electrode 3 includes a flexible substrate 31, a front electrode and a back electrode 33; the flexible electrode 3 is a double-sided flexible circuit board, with the front electrode distributed on the upper surface of the flexible substrate 31 near the contact protrusion 23, and the back electrode 33 distributed on the lower surface of the flexible substrate 31 away from the contact protrusion 23.

[0049] The front electrode includes a common electrode 321 and independent electrodes 322. The common electrode 321 is a large-area circular electrode with an internal hollow structure, with a diameter of 8.5 mm. The independent electrodes 322 are small-area circular electrodes with a diameter of 2 mm, distributed in a 2*2 array within the hollow area of ​​the common electrode 321. The independent electrodes 322 and the common electrode 321 are not connected. Both the common electrode 321 and the independent electrodes 322 have leads for connection to the measurement circuit. Each contact protrusion 23 and its corresponding independent electrode 322 are arranged coaxially. The front electrode and the back electrode 33 are connected and conductive through a through hole 35 with a diameter of 0.1 mm at the end of the back electrode 33. The contact protrusion 23 is in direct contact with the independent electrode 322, but not with the common electrode 321. The contact area between the common electrode 321 and the water remains unchanged, while the independent electrode 322 is in direct contact with the water.

[0050] Both the upper protective shell 1 and the lower protective shell 4 are made of 304 stainless steel, which has good corrosion resistance underwater. The elastic pressure block 2 is made of polydimethylsiloxane, which has good elasticity, can quickly recover after unloading, and is not prone to plastic deformation. When the force transmission protrusion 21 is subjected to external force, it can transmit the force to the contact protrusion, causing a change in the contact area between the contact protrusion 23 and the independent electrode 322. The front electrode is in direct contact with water, while the back electrode 33 is insulated and sealed except for the wiring part, and does not come into contact with the external environment.

[0051] The flexible substrate 31 is an insulating polyimide film, and both the front electrode and the back electrode 33 are gold-plated electrodes, which have good corrosion resistance underwater.

[0052] like Figure 6 As shown, the left electrode represents the common electrode 321, and the right electrode represents the independent electrode 322; the circuit between the flexible electrode 3 and the water is equivalent to the following circuit:

[0053] Including fixed capacitor C dA Variable capacitor C dB Capacitor C AB Electrode resistance R A Electrode resistance R B Resistance R L impedance Z fA and impedance Z fB ;

[0054] The capacitance formed between the common electrode 321 and the water is equivalent to a fixed capacitance C. dA The capacitance formed between the independent electrode 322 and the water is equivalent to a variable capacitance C. dB The interplate capacitance between the common electrode 321 and the independent electrode 322 is equivalent to capacitance C. ABThe resistance of the independent electrode 322 itself and the resistance between the independent electrode 322 and the measuring circuit are both equivalent to the electrode resistance R. A The resistance of the common electrode 321 itself and the resistance between the common electrode 321 and the measuring circuit are both equivalent to the electrode resistance R. B The resistance of the water between the common electrode 321 and the independent electrode 322 is equivalent to the resistance R. L The Faraday impedance generated by the electrochemical reaction at the common electrode 321 is equivalent to impedance Z. fA The Faraday impedance generated by the electrochemical reaction at the independent electrode 322 is equivalent to impedance Z. fB ;

[0055] Electrode resistance R A Measurement circuit, electrode resistance R B and capacitor C AB Series connection, fixed capacitor C dA Resistance R L and variable capacitor C dB After being connected in series with capacitor C AB Parallel connection, impedance Z fA Connected in parallel to the fixed capacitor C dA impedance Z fB Connected in parallel to the variable capacitor C dB .

[0056] The tactile detection method of the ionized underwater three-dimensional force sensor of the present invention includes the following steps:

[0057] 1) Since the sensor does not contain ionic materials, it must first be immersed in water to introduce water as an ion carrier into the sensor, such as... Figure 7 As shown, each contact protrusion 23 and its corresponding independent electrode 322 form a normal force unit, resulting in four normal force units. When the force transmission protrusion 21 is subjected to an external force F, reaction forces F1, F2, F3, and F4 along the positive Z-axis are generated on the four normal force units to balance the component of the external force F in the positive Z-axis direction. The positive Z-axis is perpendicular to the flexible electrode 3 and points towards the upper protective shell 1. Due to the principle of torque balance, the reaction forces F1, F2, F3, and F4 will not be equal. After the contact protrusion 23 of each normal force unit is pressed down by the external force F, the contact area between the contact protrusion 23 and the independent electrode 322 of the normal force unit with a larger force is larger than that of other normal force units with smaller forces. Therefore, the contact area between the independent electrode 322 and the water at that location is smaller, and the equivalent variable capacitance C between the water and the independent electrode 322 is measured. dB The capacitance value is relatively small;

[0058] 2) By measuring the capacitance values ​​of the four normal force units, the force on the contact protrusion of each normal force unit is calculated based on the pre-calibrated mapping relationship obtained by the capacitance value of each normal force unit. Finally, the magnitude and direction of the external force F are obtained by decoupling calculation through a three-dimensional force decoupling model.

[0059] Based on the designed dimensions, after the sensor is assembled, the limiting frame 14 squeezes the limiting block 22, so that the elastic block 2 is subjected to pre-pressure in the initial stage. The introduction of pre-pressure is beneficial to the stability of the sensing signal in the initial stage. Since the density of the material of the elastic block 2, polydimethylsiloxane, is close to that of water, it can be considered that its gravity and buoyancy cancel each other out, and the sensing signal is only related to the external load.

[0060] Because of C AB Much smaller than C dA C dB Furthermore, the electrochemical reaction is weak, and the Faraday impedance can be ignored. In practice, the measured impedance can be equivalent to R. A C dA R L C dB R B Serial connection; C dA C dB The value of C is mainly positively correlated with the contact area between the electrode and the water. In this invention, the contact area between the common electrode 321 and the water remains constant, while the contact area between the independent electrode 322 and the water changes with the force applied to the elastic block. Therefore, C dA For a fixed capacitor, C dB For a variable capacitor, the measured impedance signal is given by C. dB The decision is made. In a circuit with two capacitors connected in series, the equivalent series capacitance is more significantly affected by the smaller capacitor, therefore C... dB The smaller the value, the greater the impact on the measurement results when it changes, resulting in higher sensor sensitivity. Therefore, in this invention, the area of ​​the independent electrode 322 is much smaller than that of the common electrode 321, which effectively improves the sensor sensitivity.

Claims

1. An ionized underwater three-dimensional force sensor, characterized in that: It includes an upper protective shell (1), an elastic pressure block (2), a flexible electrode (3), and a lower protective shell (4); The upper protective shell (1) has a shell positioning groove (12) at the bottom of its outer periphery, and the lower protective shell (4) has a positioning block (41) on its inner wall. The upper protective shell (1) and the lower protective shell (4) are clamped and positioned by the shell positioning groove (12) and the positioning block (41). A limit frame (14) is opened in the middle of the upper protective shell (1). A limit block (22) is provided on the outer periphery of the elastic pressure block (2). The elastic pressure block (2) is fixed by being embedded in the limit frame (14) through the limit block (22). A force transmission protrusion (21) is provided on the top surface of the elastic pressure block (2). Four hemispherical contact protrusions (23) are provided on the bottom surface of the elastic pressure block (2). A flexible electrode (3) is arranged horizontally below the elastic pressure block (2). The flexible electrode (3) is fixed on the lower protective shell (4). The underwater three-dimensional force sensor is placed in an ion carrier. The ion carrier enters the underwater three-dimensional force sensor through the exhaust hole (13) on the top surface of the upper protective shell (1) and then connects to the flexible electrode (3). The flexible electrode (3) includes a flexible substrate (31), a front electrode and a back electrode (33); the front electrode is distributed on the upper surface of the flexible substrate (31) near the contact protrusion (23), and the back electrode (33) is distributed on the lower surface of the flexible substrate (31) away from the contact protrusion (23). The flexible electrode (3) has an electrode positioning groove (34) on its outer peripheral surface. The flexible electrode (3) and the lower protective shell (4) are clamped and positioned by the electrode positioning groove (34) and the positioning block (41). The front electrode includes a common electrode (321) and an independent electrode (322). The common electrode (321) is distributed on the upper surface of the flexible substrate (31) and has multiple annular hollow portions. The independent electrodes (322) are distributed in a 2*2 array on the upper surface of the flexible substrate (31) and located in the hollow portions of the common electrode (321). Each contact protrusion (23) and its corresponding independent electrode (322) are arranged coaxially. The independent electrodes (322) and the common electrode (321) are not connected. The independent electrodes (322) and the common electrode (321) are electrically connected to the external measurement circuit through external leads. The contact protrusion (23) does not contact the common electrode (321). The front electrode is in contact with the ion carrier. The back electrode (33) is insulated and sealed except for the external leads. The front electrode and the back electrode (33) are connected and conductive through a through hole (35) opened at the end of the back electrode (33).

2. The ionized underwater three-dimensional force sensor according to claim 1, characterized in that: The circuit between the flexible electrode (3) and the external ion carrier is equivalent to the following circuit: Including fixed capacitor C dA Variable capacitor C dB Capacitor C AB Electrode resistance R A Electrode resistance R B Resistance R L impedance Z fA and impedance Z fB ; The capacitance formed between the common electrode (321) and the ion carrier is equivalent to a fixed capacitance C. dA The capacitance formed between the independent electrode (322) and the ion carrier is equivalent to a variable capacitance C. dB The interplate capacitance between the common electrode (321) and the independent electrode (322) is equivalent to capacitance C. AB The resistance of the independent electrode (322) itself and the resistance between the independent electrode (322) and the measuring circuit are both equivalent to the electrode resistance R. A The resistance of the common electrode (321) itself and the resistance between the common electrode (321) and the measuring circuit are both equivalent to the electrode resistance R. B The resistance of the ion carrier between the common electrode (321) and the independent electrode (322) is equivalent to the resistance R. L The Faraday impedance generated by the electrochemical reaction at the common electrode (321) is equivalent to impedance Z. fA The Faraday impedance generated by the electrochemical reaction at the independent electrode (322) is equivalent to impedance Z. fB ; The electrode resistance R A Measurement circuit, electrode resistance R B and capacitor C AB The fixed capacitor C is connected in series. dA Resistance R L and variable capacitor C dB After being connected in series with capacitor C AB Parallel connection, the impedance Z fA Connected in parallel to the fixed capacitor C dA The impedance Z fB Connected in parallel to the variable capacitor C dB .

3. The ionized underwater three-dimensional force sensor according to claim 1, characterized in that: The outer peripheral surface of the upper protective shell (1) is provided with a fixed threaded hole (11), and the outer peripheral surface of the lower protective shell (4) is provided with a fixed through hole (42). The upper protective shell (1) and the lower protective shell (4) are fixedly connected by screws passing through the fixed threaded hole (11) and the fixed through hole (42) respectively. The exhaust hole (13) is circumferentially spaced on the top surface of the upper protective shell (1), and a handle (15) is fixedly installed on the outer wall of the upper protective shell (1).

4. The ionized underwater three-dimensional force sensor according to claim 1, characterized in that: The upper protective shell (1) and the lower protective shell (4) are both made of stainless steel, the elastic pressure block (2) is made of polydimethylsiloxane, and the front electrode and the back electrode (33) are both gold-plated electrodes.

5. A tactile detection method applied to a three-dimensional force sensor according to any one of claims 1-4, characterized in that: The method includes the following steps: 1) An underwater three-dimensional force sensor is placed in an ion carrier. Each contact protrusion (23) and its corresponding independent electrode (322) form a normal force unit. When the force transmission protrusion (21) is subjected to an external force F, the external force F is transmitted to the contact protrusion (23) of each normal force unit. After being subjected to the external force F, the contact protrusion (23) of each normal force unit is pressed down, and the contact area between the contact protrusion (23) and the independent electrode (322) increases, which reduces the contact area between the ion carrier and the independent electrode (322), thereby affecting the equivalent variable capacitance C between the ion carrier and the independent electrode (322). dB The capacitance value ultimately changes the capacitance value of the normal force element; 2) By measuring the capacitance values ​​of the four normal force units, the force on the contact protrusion (23) of each normal force unit is calculated based on the capacitance value of each normal force unit using the pre-calibrated mapping relationship. Finally, the magnitude and direction of the external force F are obtained by decoupling calculation through the three-dimensional force decoupling model.

6. The tactile detection method of the three-dimensional force sensor according to claim 5, characterized in that: The area of ​​the independent electrode (322) is smaller than that of the common electrode (321), and the contact area between the common electrode (321) and the ion carrier remains unchanged.

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