High-sensitivity array type underwater three-dimensional force sensor

Abstract

The invention discloses a high-sensitivity array type underwater three-dimensional force sensor. The array type underwater three-dimensional force sensor comprises a plurality of three-dimensional force sensing units which are arranged in an array mode. Each three-dimensional force sensing unit comprises a flexible sensing layer, a supporting layer and a flexible electrode which are arranged in a stacked mode in the thickness direction. The flexible sensing layer is mainly formed by connecting a conducting layer and a sensitive layer through a connecting layer; the conducting layer is hemispherical, the elastic modulus of the conducting layer is greater than that of the connecting layer and the sensitive layer, and the sensitive layer comprises four rectangular pyramid sensing elements arranged in a matrix; the supporting layer is provided with a flow channel which is used for enabling an external ion carrier to enter the three-dimensional force sensing unit. One side, close to the flexible sensing layer, of the flexible electrode is provided with a front electrode, and the front electrode is electrically connected with the ion carrier; a through hole is formed in the center of the supporting layer, so that the tip of the rectangular pyramid sensing element can be in contact with the front electrode. According to the invention, the gradient modulus flexible sensing unit and the low pre-pressing design are utilized, so that the sensor has an underwater high-sensitivity three-dimensional force detection function.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underwater robots, and particularly relates to a high-sensitivity array type underwater three-dimensional force sensor. BACKGROUND

[0002] With the exhaustion of land resources and the increase of mining difficulty, the focus of resource development is shifted to the ocean, which is the trend of future development. The development of underwater robot technology makes it possible to replace divers with robots to carry out underwater facility operation and inspection, which is a high-efficiency and low-cost solution.

[0003] The underwater robot needs information of the end effector to perform the operation. However, the sensitivity of the general underwater sensor is insufficient, and in the process of the operator controlling the underwater robot, there is often a lack of force feedback sensitivity and small force signal, which may lead to the operator's misjudgment of the operation strength, and further lead to operation failure. Therefore, integrating a high-sensitivity sensing system in the end effector of the underwater robot helps the operator to obtain small information, which can effectively improve the success rate of underwater operation.

[0004] The existing off-electric underwater three-dimensional force sensor adopts a high-modulus elastic block, and the pre-pressing occupies part of the range during the operation, so the minimum force detection sensitivity is low, and it is difficult to perceive small information in the actual underwater scene. SUMMARY

[0005] To solve the above problems, the application provides a high-sensitivity underwater three-dimensional force sensing array, which solves the problem of insufficient sensitivity of most underwater sensors and has important significance for obtaining small information during underwater robot operation.

[0006] The technical scheme adopted by the application is as follows:

[0007] One, a high-sensitivity array type underwater three-dimensional force sensor

[0008] The array type underwater three-dimensional force sensor comprises a plurality of three-dimensional force sensing units arranged in an array, each three-dimensional force sensing unit comprising a flexible sensing layer, a support layer and a flexible electrode arranged in a thickness direction; the flexible sensing layer is mainly connected by a connecting layer and a sensitive layer; the conductive layer is semispherical, and the elastic modulus is greater than that of the connecting layer and the sensitive layer, the sensitive layer mainly comprises four pyramid sensing elements arranged according to a 2*2 matrix; the support layer is provided with a flow channel for allowing external ion carriers to enter the three-dimensional force sensing unit; a through hole is formed in the center of the support layer; a front electrode is arranged on the surface of the flexible electrode close to the flexible sensing layer, and the front electrode is electrically connected with the ion carrier; the tip of the pyramid sensing element in the sensitive layer penetrates through the through hole of the support layer and contacts the front electrode.

[0009] Specifically, the front electrode is mainly composed of four front independent electrodes and a front common electrode arranged around the four front independent electrodes; the front independent electrode corresponds to a four-pyramid sensing element in the sensitive layer one by one, the center of each front independent electrode is aligned with the axis of the corresponding four-pyramid sensing element in the thickness direction, and contacts the tip of the four-pyramid sensing element.

[0010] Specifically, in the initial state, the difference between the distance from the bottom surface of the connecting layer to the front independent electrode and the height of the four-pyramid sensing element in the sensitive layer is 0.005-0.02 mm, preferably 0.01 mm.

[0011] Preferably, the elastic modulus of the conductive layer is at least 3 times that of the connecting layer and the sensitive layer.

[0012] Specifically, in each three-dimensional force sensing unit, the front common electrode serves as a negative electrode, and each front independent electrode serves as a positive electrode, the front common electrode is electrically connected to the input channel of the measurement circuit, and each front independent electrode is also electrically connected to a different independent input channel of the measurement circuit.

[0013] Further, the three-dimensional force sensing unit further comprises an upper shell and a lower shell; the upper shell is provided with a central hole as a limiting frame, and the conductive layer is arranged in the limiting frame.

[0014] Preferably, in the array-type underwater three-dimensional force sensor, the lower shells of all three-dimensional force sensing units are connected by integral molding, the flexible substrates of the flexible electrodes are connected by integral molding, and the front common electrodes are electrically connected by patterning wiring. The back electrode of the flexible electrode comprises a plurality of back independent electrodes and a back common electrode, the back common electrode is electrically connected to the front common electrode through a common electrode via hole; the number of back independent electrodes, independent electrode via holes and front independent electrodes is the same and one-to-one correspondence, and the back independent electrode is electrically connected to the corresponding front independent electrode through the corresponding independent electrode via hole.

[0015] Preferably, the cross section of the flow channel is stepped, and the side close to the flexible sensing layer has a smaller cross-sectional area; one end (radially outer end) of the flow channel is connected to the external environment, and the other end (radially inner end) is connected to the gap between the connecting layer and the flexible electrode. The flow direction of the ion carrier in the flow channel is perpendicular to the thickness direction.

[0016] Preferably, a rectangular groove is arranged on each of the four sides of the connecting layer, and a boss is provided on each of the four sides of the supporting layer. The cavity inside the boss forms the protrusion of the flow channel (i.e., the part with a smaller cross-sectional area). The boss and the rectangular groove correspond one-to-one and are aligned in the thickness direction. The boss is fitted into the corresponding rectangular groove.

[0017] II. An underwater three-dimensional force sensing method employing the above-mentioned highly sensitive array-type underwater three-dimensional force sensor

[0018] The underwater three-dimensional force sensing method includes: measuring the capacitance values ​​of four pyramidal sensing elements through a measurement circuit; using a pre-calibrated mapping relationship, calculating the force on each pyramidal sensing element based on its capacitance value; and finally, using a three-dimensional force decoupling method to decouple and calculate the forces on the four pyramidal sensing elements to obtain the magnitude and direction of the external force.

[0019] The beneficial effects of this invention are:

[0020] 1) The conductive layer has a higher modulus, while the connecting layer and the sensitive layer have lower modulus. When the conductive layer is subjected to force, the deformation of the flexible sensing layer is concentrated in the sensitive layer, while the deformation of the conductive layer is smaller. Compared with the flexible sensing layer with the same overall modulus, the contact area between the sensitive layer and the independent electrode changes more, resulting in higher sensitivity.

[0021] 2) The sensor has an open structure and is minimally affected by water pressure in water.

[0022] 3) The sensing layer is an array of square pyramidal structures. Compared with hemispherical and conical structures, the square pyramidal structure has a larger change in the contact area with the independent front electrode when subjected to pressure, resulting in higher sensor sensitivity.

[0023] 4) The distance between the support layer and the lower housing and the height difference of the square pyramid are extremely small. The pre-compression of the flexible sensing layer when no load is applied is extremely small, and it hardly occupies the range. The sensor can detect force changes as low as 50 Pa. Attached Figure Description

[0024] Figure 1 This is an overall structural diagram of the sensor array of the present invention.

[0025] Figure 2 This is a schematic diagram of the flexible sensing layer of the sensing array of the present invention.

[0026] Figure 3 This is a breakdown diagram of the sensing unit of the sensing array of the present invention.

[0027] Figure 4 This is a schematic diagram of the flexible electrodes of the sensor array of the present invention.

[0028] Figure 5 This is a schematic diagram illustrating the high-sensitivity principle of the sensor array of the present invention.

[0029] Figure 6 This is the equivalent circuit diagram of the sensor array of the present invention.

[0030] Figure 7 This is a schematic diagram of the three-dimensional force detection principle of the sensor array of the present invention.

[0031] Figure 8 This is a schematic diagram of the manufacturing process of the flexible sensing layer of the sensing array of the present invention.

[0032] In the diagram: 1. Upper housing, 2. Flexible sensing layer, 3. Support layer, 4. Flexible electrode, 5. Lower housing, 6. Sensing layer, 7. Conductive layer, 8. Flexible sensing layer positioning hole, 9. Upper housing positioning hole, 10. Limiting frame, 11. Connecting layer, 12. Support layer positioning hole, 13. Flow channel, 14. Flexible electrode positioning hole, 15. Flexible substrate, 16. Front common electrode, 17. Front independent electrode, 18. Threaded positioning hole, 19. Independent electrode through hole, 20. Back electrode, 21. Common electrode through hole. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are provided to provide those skilled in the art with a description of how to implement, prepare, and evaluate the compositions and methods claimed herein, and are intended purely as examples of the invention and not to limit the scope of what the inventors consider to be their invention.

[0034] This invention provides a highly sensitive array-type underwater three-dimensional force sensor.

[0035] like Figure 1 As shown, the array-type underwater three-dimensional force sensor of the present invention includes several three-dimensional force sensing units arranged in an array. Each three-dimensional force sensing unit includes components along its own thickness direction ( Figure 1 The flexible sensing layer 2, the support layer 3, and the flexible electrode 4 are arranged in a vertically stacked manner.

[0036] like Figure 2As shown, the flexible sensing layer 2 is mainly composed of a conductive layer 7 and a sensitive layer 6 connected by a connecting layer 11. The conductive layer 7 is hemispherical in shape, and its elastic modulus is greater than that of the connecting layer 11 and the sensitive layer 6. The sensitive layer 6 is mainly composed of four quadrangular pyramid sensing elements arranged in a 2×2 matrix. The center of the elastic hemisphere of the conductive layer 7 and the center of the quadrangular pyramid array of the sensitive layer 6 are on the same vertical axis. The connecting layer 11 between the conductive layer 7 and the sensitive layer 6 is an elastic film, and the connecting layer 11 is in contact with the support layer 3. A flow channel 13 is arranged on the support layer 3 to allow external ion carriers to enter the three-dimensional force sensing unit. A front electrode is arranged on the surface of the flexible electrode 4 near the flexible sensing layer 2. After the front electrode contacts the ion carrier, an ion-electron interface is formed, making the front electrode electrically connected to the ion carrier. A through hole is opened in the middle of the support layer 3, and the conical tip of the quadrangular pyramid sensing element passes through the through hole and contacts the front electrode.

[0037] Preferably, the elastic modulus of the conductive layer 7 is three times or more than three times the elastic modulus of the connecting layer 11 and the sensitive layer 6.

[0038] like Figure 3 As shown, the front electrode mainly consists of four independent front electrodes 17 and a common front electrode 16 spaced around the four independent front electrodes 17. The spaced arrangement means that there is no electrical connection between the independent front electrodes 17 and the common front electrode 16. The number of independent front electrodes 17 corresponds one-to-one with the number of pyramidal sensing elements in the sensitive layer 6. The center of each independent front electrode 17 is aligned along the thickness direction with the axis of its corresponding pyramidal sensing element and contacts the conical tip of the pyramidal sensing element. In the initial state and under stress, the portions of each independent front electrode 17 not in contact with the corresponding pyramidal sensing element, as well as the common front electrode 16, can contact the ion carrier flowing into the three-dimensional force sensing unit.

[0039] In the initial state, the distance from the bottom surface of the connecting layer 11 to the front independent electrode 17 is 0.005~0.02mm, preferably 0.01mm, compared to the height of the pyramidal sensing element before assembly. This results in minimal pre-compression between the flexible sensing layer 2 and the flexible electrode 4 when no force is applied.

[0040] like Figure 3 As shown, the flexible electrode 4 also includes a flexible substrate 15 and a back electrode 20. A front electrode is arranged on one side surface of the flexible substrate 15 near the flexible sensing layer 2, and a back electrode 20 is arranged on the other side surface. The back electrode 20 is connected to the front electrode through a via.

[0041] Optionally, the front common electrode 16 and the front independent electrode 17 are arranged on the surface of the flexible substrate 15 as follows: a hollow area is provided in the center of the front common electrode 16, and four front independent electrodes 17 are arranged in a 2×2 matrix in the hollow area of ​​the front common electrode 16.

[0042] Optionally, the back electrode 20 being connected to the front electrode via a via means that the back electrode 20 includes several independent back electrodes and several common back electrodes. Each independent back electrode is arranged below its corresponding independent front electrode 17 and is connected to the independent front electrode 17 above it through an independent electrode via 19. The common back electrode is arranged below the common front electrode 16 and is connected to the common front electrode 16 through a common electrode via 21.

[0043] like Figure 3 As shown, the support layer 3 adopts a rigid sheet structure with a central hollow core. The support layer 3 is in close contact with part of the edge area of ​​the flexible electrode 4 to achieve the connection and positioning of the structure. In the remaining edge areas, a certain gap is maintained between the two to form a flow channel 13. One radially outer end of the flow channel 13 is connected to the external environment, and the radially inner end is connected to the gap between the connecting layer 11 and the flexible electrode 4.

[0044] Preferably, the bottom surface at the edge of the support layer 3 is stepped, making the cross-section of the flow channel 13 stepped. The flow channel 13 on the side closer to the flexible sensing layer 2 has a smaller cross-sectional area. The convex-shaped flow channel 13 helps to expel the internal gas of the array-type underwater three-dimensional force sensor after it is submerged in the ion carrier, thereby avoiding the adverse effects of residual gas bubbles inside the sensing unit on the sensor performance.

[0045] In the preferred embodiment described above, a rectangular groove is arranged on each of the four sides of the connecting layer 11, and a boss is arranged around the top surface of the support layer 3. The cavity inside the boss forms the protrusion of the flow channel 13. The boss and the rectangular groove correspond one-to-one and are aligned in the thickness direction. The boss is fitted into the corresponding rectangular groove.

[0046] Furthermore, the three-dimensional force sensing unit also includes an upper housing 1 and a lower housing 5; the upper housing 1 has a central hole as a limiting frame 10, and the hemispherical conductive layer 7 passes through the limiting frame 10 to achieve its own positioning.

[0047] Optionally, the upper housing 1, the flexible sensing layer 2, the support layer 3, the flexible electrode 4, and the lower housing 5 are connected by threads.

[0048] In the above optional embodiments, the upper housing 1, flexible sensing layer 2, support layer 3, flexible electrode 4, and lower housing 5 are respectively provided with upper housing positioning holes 9, flexible sensing layer positioning holes 8, support layer positioning holes 12, flexible electrode positioning holes 14, and threaded positioning holes 18 at their corners. The number of upper housing positioning holes 9, flexible sensing layer positioning holes 8, support layer positioning holes 12, flexible electrode positioning holes 14, and threaded positioning holes 18 are the same and are arranged in a one-to-one correspondence in the thickness direction, and are connected by bolts.

[0049] Preferably, in the array-type underwater three-dimensional force sensor, the lower housings 5 ​​of all three-dimensional force sensing units are connected by integral molding, the flexible substrates 15 of the flexible electrodes 4 of all three-dimensional force sensing units are connected by integral molding, and the front common electrode 16 of all three-dimensional force sensing units is electrically connected through patterned wiring. The back electrode 20 includes multiple independent back electrodes and one back common electrode, which is electrically connected to the front common electrode 16 of all three-dimensional force sensing units through a common electrode via 21. The number of independent back electrodes, independent electrode vias 19, and independent front electrodes 17 are the same and correspond one-to-one, and the independent back electrodes are electrically connected to the corresponding independent front electrodes 17 through the corresponding independent electrode vias 19.

[0050] Specifically, in each three-dimensional force sensing unit, the front common electrode 16 serves as the negative electrode, and each front independent electrode 17 serves as the positive electrode. Both are electrically connected to different independent input channels of the measurement circuit.

[0051] like Figure 6 As shown, the circuit between the flexible electrode 4 and the external ion carrier is equivalent to the following circuit: including a 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 front common electrode 16 and the ion carrier is equivalent to a fixed capacitance C. dA The capacitance formed between the front independent electrode 17 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 independent electrode 17 on the front side, as well as the resistance between it and the measurement circuit, are equivalent to the electrode resistance R. A The resistance of the front common electrode 16 itself and the resistance between it and the measurement circuit are both equivalent to the electrode resistance R. B The resistance of the ion carrier between the front common electrode 16 and the front independent electrode 17 is equivalent to resistance R.L The Faraday impedance generated by the electrochemical reaction at the 16th common electrode on the front side is equivalent to impedance Z. fA The Faraday impedance generated by the electrochemical reaction at the 17 independent electrodes on the front side is equivalent to impedance Z. fB 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 .

[0052] Preferably, the capacitance values ​​of the four pyramidal sensing elements are measured by a measuring circuit. Using a pre-calibrated mapping relationship, the force on each pyramidal sensing element is calculated based on its capacitance value. Finally, the force on the four pyramidal sensing elements is decoupled and calculated using a three-dimensional force decoupling method to obtain the magnitude and direction of the external force.

[0053] Preferably, the conductive layer material of the flexible sensing layer 2 is a PDMS elastomer obtained by mixing PDMS substrate, PDMS curing agent and silicone oil in a ratio of 5:1:1 and heating and curing at 80°C for 2 hours. It has a high modulus and a low surface lubrication friction coefficient. The materials of the connecting layer 11 and the sensitive layer 6 are PDMS elastomers obtained by mixing PDMS substrate and PDMS curing agent in a ratio of 15:1 and heating and curing at 80°C for 2 hours. They have a low modulus.

[0054] Preferably, the upper shell 1, the support layer 3, and the lower shell 5 are made of anodized 6061 aluminum alloy.

[0055] Preferably, the conductive metal portion of the flexible electrode 4 (front electrode, back electrode 20, inner wall of via, etc.) is gold-plated copper, and the flexible substrate 16 is made of polyimide (PI).

[0056] Optionally, the above-mentioned ion carrier is water.

[0057] The present invention also provides an underwater three-dimensional force sensing method using the above-mentioned highly sensitive array-type underwater three-dimensional force sensor, comprising: measuring the capacitance values ​​of four pyramidal sensing elements through a measurement circuit; using a pre-calibrated mapping relationship, calculating the force on each pyramidal sensing element based on the capacitance value of each pyramidal sensing element; and finally, decoupling the force on the four pyramidal sensing elements through a three-dimensional force decoupling method to obtain the magnitude and direction of the external force.

[0058] Specific embodiments of the present invention are as follows:

[0059] Example 1

[0060] like Figure 1 As shown, the array-type underwater three-dimensional force sensor is generally square in shape with a height of 3.52 mm. Each three-dimensional force sensing unit includes an upper shell 1, a flexible sensing layer 2, a support layer 3, a flexible electrode 4, and a lower shell 5. The upper shell 1, flexible sensing layer 2, support layer 3, flexible electrode 4, and lower shell 5 are stacked from top to bottom and then clamped together with bolts.

[0061] The upper housing 1 has a limiting frame 10 at its center. The limiting frame 10 is a circular hole with a diameter of 6mm. It is positioned in conjunction with the hemisphere of the conductive layer 7 of the flexible sensing layer 2. The upper housing 1 has a thickness of 1mm. The upper housing has positioning holes 9 with a diameter of 1mm at its four corners. The radius of the rounded corners of the upper housing 1 is 1mm.

[0062] The flexible sensing layer 2 consists of a conductive layer 7, a connecting layer 11, and a sensitive layer 6. The conductive layer 7 is a hemispherical elastomer with a diameter of 6 mm. The connecting layer 11 is an elastomer film with flexible sensing layer positioning holes 8 at the four corners. The connecting layer 11 has a thickness of 0.4 mm and a corner radius of 1 mm. The sensitive layer 6 is a 2*2 distributed quadrangular pyramid array.

[0063] The support layer 3 has convex-shaped flow channels 13 arranged around its perimeter, and support layer positioning holes 12 are opened at its four corners. For example... Figure 3 As shown, the outer edge of the support layer 3 is provided with an upward-facing boss, and the cavity inside the boss forms the protrusion of the flow channel 13. The height of the boss is 0.4 mm, and it fits into the connecting layer 11 of the flexible sensing layer 2, with a corner radius of 1 mm.

[0064] The lower housing 5 has threaded positioning holes 18 at its four corners. The specification of the threaded positioning holes 18 is M1, and the radius of the rounded corners of the lower housing 5 is 1mm.

[0065] The upper housing positioning hole 9, the flexible sensing layer positioning hole 8, the support layer positioning hole 12, the flexible electrode positioning hole 14, and the threaded positioning hole 18 are all 2×2 arrays with a spacing of 8mm, stacked from top to bottom, with corresponding hole positions concentrically distributed. The individual three-dimensional force sensing unit in the array-type underwater three-dimensional force sensor is clamped by an M1 screw.

[0066] Among them, the conductive layer 7 of the flexible sensing layer 2 is a hemisphere with a diameter of 6mm. The conductive layer 7 has the same diameter as the limiting frame 10 of the upper shell 1, and the two are in line contact, so there is no friction.

[0067] During use, the array-type underwater three-dimensional force sensor is placed in water. Water enters the interior of the underwater three-dimensional force sensor through the flow channel 13 of the support layer 3 and is electrically connected to the flexible electrode 4.

[0068] Among them, the distance between the bottom surface of the connecting layer 11 and the front independent electrode 17 is 0.01mm lower than the height of the square pyramid sensing element of the sensitive layer 6. When no external force is applied, the pre-pressure between the flexible sensing layer 2 and the flexible electrode 4 is minimal.

[0069] The front common electrode 16 is distributed on the upper surface of the flexible substrate 15 and has multiple hollowed-out portions. The front independent electrode 17 is distributed on the upper surface of the flexible substrate 15 in a 2*2 array and is located in the hollowed-out portions of the front common electrode 16. The quadrangular pyramid sensing element of the sensitive layer 6 and its corresponding front independent electrode 17 are arranged coaxially. The front independent electrode 17 and the front common electrode 16 are not connected. The front independent electrode 17 and the front common electrode 16 are electrically connected to the external measurement circuit through external leads. The sensitive layer 6 does not contact the front common electrode 16.

[0070] The front electrode and the back electrode 20 are connected and conductive through an independent electrode via 19 and a common electrode via 21, with a via diameter of 0.1 mm. The flexible sensing layer 2 is in direct contact with the front independent electrode 17, but not with the front common electrode 16. Both the front common electrode 16 and the front independent electrode 17 are in direct contact with water. The back electrode 20 is insulated and sealed except for the wiring part, and does not come into contact with the external environment.

[0071] In this example, both the upper housing 1 and the lower housing 4 are made of anodized 6061 aluminum alloy, which has good corrosion resistance underwater. When the conductive layer 7 is subjected to external force, it can transmit the force to the sensitive layer 6, causing a change in the contact area between the pyramidal sensing element of the sensitive layer 6 and the corresponding front independent electrode 17, while the contact area between the front common electrode 16 and the water remains unchanged.

[0072] In this example, the flexible sensing layer 2 is made of polydimethylsiloxane, which has good elasticity, can recover quickly after unloading, and is not prone to plastic deformation.

[0073] In this example, the flexible substrate 15 is an insulating polyimide film, and both the front electrode and the back electrode 20 are gold-plated electrodes, which have good corrosion resistance underwater.

[0074] like Figure 6As shown, the circuit between the flexible electrode 4 and the ion carrier is equivalent to the following circuit:

[0075] The equivalent circuit includes a 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 front common electrode 16 and the ion carrier is equivalent to a fixed capacitance C. dA The capacitance formed between the front independent electrode 17 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 independent electrode 17 on the front side, as well as the resistance between it and the measurement circuit, are equivalent to the electrode resistance R. A The resistance of the front common electrode 16 itself and the resistance between it and the measurement circuit are both equivalent to the electrode resistance R. B The resistance of the ion carrier between the front common electrode 16 and the front independent electrode 17 is equivalent to resistance R. L The Faraday impedance generated by the electrochemical reaction at the 16th common electrode on the front side is equivalent to impedance Z. fA The Faraday impedance generated by the electrochemical reaction at the 17 independent electrodes on the front side is equivalent to impedance Z. fB 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 .

[0076] The sensor's detection process is as follows:

[0077] Since the sensor does not contain ionic materials, it must be immersed in water to introduce water as an ion carrier into the sensor. Figure 7As shown, each square pyramid and its corresponding independent electrode form a normal force unit, resulting in four normal force units. When the conductive layer 7 is subjected to an external force F, reaction forces F1, F2, F3, and F4 are generated in the four normal force units along the positive Z-axis 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 4 and points towards the upper shell 1. Due to the principle of torque balance, the reaction forces F1, F2, F3, and F4 will not be equal. The square pyramid elastic body of each normal force unit is pressed down after being subjected to the external force F. The contact area between the square pyramid elastic body and the independent electrode of the normal force unit with the larger force is larger than that of the other normal force units with smaller forces. Therefore, the contact area between the independent electrode and the water at that location is smaller. Thus, the equivalent variable capacitance C between the water and the independent electrode is measured. dB The capacitance value is relatively small.

[0078] By measuring the capacitance values ​​of four normal force elements, the force on each normal force element is calculated based on the pre-calibrated mapping relationship obtained according to the capacitance value of each normal force element. Finally, the magnitude and direction of the external force F are obtained by decoupling calculation through the three-dimensional force decoupling model using a self-distributed three-dimensional force decoupling method.

[0079] Based on the designed dimensions, after the sensing unit is assembled, the flexible sensing layer is subjected to extremely low pre-pressure in the initial stage. The introduction of pre-pressure is beneficial to the stability of the sensing signal in the initial stage. The extremely low pre-pressure has minimal impact on the sensor range, which is conducive to making full use of the high sensitivity of the sensing unit in the initial stage. Since the density of the flexible sensing layer 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.

[0080] The stress deformation process of the flexible sensing layer is as follows Figure 5 As shown, the flexible sensing layer adopts a gradient modulus design. When subjected to pressure, the deformation of the conductive layer is small, while the deformation of the sensitive layer is large. The contact area with the bottom flexible electrode is large, resulting in a large change in capacitance, which can detect forces as low as 50 Pa.

[0081] 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 dBThe 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 and the water remains constant, while the contact area between the independent electrode and the water changes with the force applied to the flexible sensing layer 2. 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 is made much smaller than that of the common electrode, which effectively improves the sensor sensitivity.

[0082] Example 2

[0083] This embodiment provides the manufacturing process of the sensor in Embodiment 1, mainly including the preparation of the flexible sensing layer 2 and its overall stacking and assembly. The specific implementation process is as follows: Figure 8 As shown, it includes the following steps:

[0084] Step S1: Use CNC technology to complete the fabrication of the conductive layer mold and the sensing layer mold. The sensing layer mold includes the connecting layer part. Then wipe the connector, conductive layer mold and connecting layer mold with alcohol.

[0085] Step S2: Dimethylsiloxane main agent, curing agent, and silicone oil are uniformly mixed at a mass ratio of 5:1:1 to obtain type A polydimethylsiloxane PDMS. Dimethylsiloxane main agent and curing agent are uniformly mixed at a mass ratio of 15:1 to obtain type B polydimethylsiloxane PDMS. A portion of type A polydimethylsiloxane PDMS is poured into a conductive layer mold, and the excess is removed. Another portion of type B polydimethylsiloxane PDMS is poured into a sensing layer mold, and the excess is removed. Both are heated at 80℃ for 2 hours to cure and then demolded to obtain the conductive layer, connecting layer, and sensing layer.

[0086] Step S3: Place the sensitive layer 6 and the connecting layer 11 in the sensing layer mold, and cover the sensing layer mold with the connector. Spin-coat a layer of Class B PDMS on the upper surface of the connecting layer 11 with a thickness of 0.1 mm. Place the hemispherical conductive layer 7 in the hollow of the connector, press it tightly, and then heat the whole thing at 80°C for 0.5 h to cure it, so that the two are connected.

[0087] Step S4: Stack the upper shell 1, flexible sensing layer 2, support layer 3, flexible electrode 4, and lower shell 5 from top to bottom, and use screws to position and clamp them to assemble them into an array-type underwater three-dimensional force sensor.

[0088] In summary, the sensor of this invention can operate in an underwater environment and can detect three-dimensional force changes as low as 50 Pa, which is of great significance for underwater robots to acquire minute information, operate dexterously, and improve the success rate of underwater operations.

[0089] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

[0090] The above description is only a preferred embodiment of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of this patent application are included in the scope of this patent application.

Claims

1. A high-sensitivity arrayed underwater three-dimensional force sensor, comprising a plurality of three-dimensional force sensing units arranged in an array, characterized in that: Each three-dimensional force sensing unit comprises a flexible sensing layer (2), a support layer (3) and a flexible electrode (4) arranged in a laminated manner along the thickness direction; The flexible sensing layer (2) is mainly composed of a conductive layer (7) and a sensitive layer (6) connected by a connecting layer (11); the conductive layer (7) is semispherical and has an elastic modulus greater than that of the connecting layer (11) and the sensitive layer (6); the sensitive layer (6) is mainly composed of four four-pyramid sensing elements arranged in a 2x2 matrix; The support layer (3) is provided with a flow channel (13) for allowing an external ion carrier to enter the three-dimensional force sensing unit; a through hole is formed in the center of the support layer (3); The flexible electrode (4) is provided with a front electrode on the surface of the side close to the flexible sensing layer (2); the front electrode is electrically connected with the ion carrier; the tips of the four-pyramid sensing elements in the sensitive layer (6) pass through the through hole of the support layer (3) and are in contact with the front electrode.

2. The high sensitive arrayed underwater three-dimensional force sensor according to claim 1, characterized in that: The front electrode is mainly composed of four front independent electrodes (17) and a front common electrode (16) arranged around the front independent electrodes (17); the front independent electrodes (17) correspond one-to-one to the four-pyramid sensing elements in the sensitive layer (6); the center of each front independent electrode (17) is aligned with the axis of the corresponding four-pyramid sensing element along the thickness direction and is in contact with the tip of the four-pyramid sensing element.

3. The high sensitive arrayed underwater three-dimensional force sensor according to claim 2, characterized in that: In the initial state, the difference between the distance from the bottom surface of the connecting layer (11) to the front independent electrode (17) and the height of the four-pyramid sensing element in the sensitive layer (6) is 0.005-0.02 mm.

4. The highly sensitive array-type underwater three-dimensional force sensor according to claim 2, characterized in that: The elastic modulus of the conductive layer (7) is at least 3 times that of the connecting layer (11) and the sensitive layer (6).

5. The high sensitive arrayed underwater three-dimensional force sensor according to claim 2, characterized in that: The three-dimensional force sensing unit further comprises an upper shell (1) and a lower shell (5); the upper shell (1) is provided with a central hole as a limiting frame (10); the conductive layer (7) is arranged in the limiting frame (10).

6. The high sensitive arrayed underwater three-dimensional force sensor according to claim 5, characterized in that: In the array type underwater three-dimensional force sensor, the lower shells (5) of all the three-dimensional force sensing units are connected by integral molding; the flexible substrates (15) of the flexible electrodes (4) are connected by integral molding; and the front common electrodes (16) are electrically connected by patterning.

7. The high sensitive arrayed underwater three-dimensional force sensor according to claim 2, characterized in that: In each three-dimensional force sensing unit, the front common electrode (16) serves as a negative electrode, and each front independent electrode (17) serves as a positive electrode; the front common electrode (16) and each front independent electrode (17) are electrically connected with different independent input channels of a measurement circuit, respectively.

8. The high sensitive arrayed underwater three-dimensional force sensor according to claim 1, characterized in that: The cross section of the flow channel (13) is ladder-shaped, and the side close to the flexible sensing layer (2) has a smaller cross-sectional area; one end of the flow channel (13) is connected to the external environment, and the other end is connected to the gap between the connecting layer (11) and the flexible electrode (4).

9. The high sensitive arrayed underwater three-dimensional force sensor according to claim 8, characterized in that: Each of the four sides of the connecting layer (11) is provided with a rectangular groove; each of the four sides of the support layer (3) is provided with a boss; the cavity inside the boss forms a convex part of the flow channel (13); the boss and the rectangular groove are one-to-one corresponding and arranged in alignment in the thickness direction; and the boss is embedded in the corresponding rectangular groove.

10. A method for sensing three-dimensional force underwater using the high-sensitivity array-type three-dimensional force sensor according to any one of claims 1 to 9, characterized by, The application relates to a four-prism sensor element and a force measurement method. The force of each four-prism sensor element is calculated according to the mapping relationship obtained through pre-calibration and the capacitance value of each four-prism sensor element by measuring the capacitance value of the four four-prism sensor elements through a measuring circuit. Finally, the force of the four four-prism sensor elements is decoupled and calculated through a three-dimensional force decoupling method to obtain the size and direction of the external force.

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