A hybrid sensor-driven array capacitive micro-force sensor and closed loop detection circuit

Abstract

A kind of hybrid sensing-drive array's capacitive micro force sensor and closed loop detection circuit, sensor includes mass fixed on frame by support beam, mass block extends an elongated probe at front end, more than two variable spacing type and variable area type composite capacitor array are arranged in mass block middle part;More than two variable area type drive comb array are arranged at mass block end;Closed loop detection circuit detects the position and speed information of mass block by the capacitance change of variable spacing type comb array and variable area type comb array, corresponding electrostatic force is generated by variable area type drive comb array by controller, and the closed loop detection of micro force signal of sub nN-μN order is completed;The application can greatly improve the dynamic detection performance and detection precision of capacitive micro force sensor, and reduce the interference of sensor internal noise and circuit noise to micro force signal detection.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of micro force sensors, and particularly relates to a capacitive micro force sensor of a hybrid sensing-driving array and a closed loop detection circuit. BACKGROUND

[0002] Micro-electro-mechanical system (MEMS) is an advanced system that combines micro mechanical structure and electronic and electrical elements into one based on micro processing technology and micro electronic technology. With the rapid development of MEMS technology and the continuous maturity of application, the performance of MEMS sensors has far exceeded that of traditional sensors, and has additional advantages such as small size, batch manufacturing, low cost, low power consumption and easy integration. The MEMS capacitive micro force sensor can realize high-precision measurement of micrometer or nanometer scale object on the order of pico-newton, and is widely used in the fields of micro-nano material mechanics property detection, topography measurement, automatic micro-nano manipulation and the like.

[0003] The capacitive sensor of the traditional comb array structure usually adopts a single type of variable area type or variable gap type comb array. The variable area type comb array structure has good linearity, but its sensitivity is poor, and it is not suitable for the measurement of small deformation and micro force in the biological measurement scene (El Mansouri B, Middelburg L M, Poelma R H, et al. High-resolution MEMS inertial sensor combining large-displacement buckling behaviour with integrated capacitive readout [J]. Microsystems & nanoengineering, 2019, 5(1): 60; Zhang H, Wei X, Ding Y, et al. A low noise capacitive MEMS accelerometer with anti-spring structure [J]. Sensors and Actuators A: Physical, 2019, 296: 79-86.). The variable gap type comb array structure has high sensitivity, but the linearity of its output capacitance and gap is usually not ideal (Li R, Mohammed Z, Rasras M, et al. Design, modelling and characterization of comb drive MEMS gap-changeable differential capacitive accelerometer [J]. Measurement, 2021, 169: 108377; Sun Y, Fry S N, Potasek D P, et al. Characterizing fruit fly flight behavior using a microforce sensor with a new comb-drive configuration [J]. Journal of microelectromechanical systems, 2005, 14(1): 4-11.); at the same time, the variable gap type capacitive micro force sensor is easily affected by electrostatic attraction, resulting in the reduction of linearity, range and measurement accuracy.

[0004] In characterizing fine samples, the relative stiffness of the micro-force sensor and the sample plays a crucial role. When the stiffness of the micro-force sensor itself far exceeds that of the sample being measured, the sensor can cause large deformation to the sample while the sensor itself cannot produce measurable deformation, resulting in reduced measurement accuracy and increased risk of damaging the sample. The stiffness of the sensor is determined by the size of the internal support structure of the device, which is usually increased by increasing the length and reducing the width of the support structure to increase the flexibility of the structure. However, due to the limitations of micro-nano fabrication processes and structural strength, the size of the movable structure has certain limits and cannot be arbitrarily changed.

[0005] The performance of the capacitive detection circuit as a bridge between the sensor and the processor directly affects the performance of the sensor. Traditional detection methods use capacitive voltage conversion circuits (Zhang H, Wei X, Jiang Z. Comparison study of three readout methods for a capacitive MEMS accelerometer [C] / / 2018 IEEE SENSORS. IEEE, 2018: 1-4.), capacitive phase conversion circuits (Aslam M Z, Tang T B. A high resolution capacitive sensing system for the measurement of water content in crude oil [J]. Sensors, 2014, 14(7): 11351-11361.), Sigma-Delta modulation circuits (Li Z, Xiong X, Liu X, et al. Design of a high precision digital interface circuit for capacitive MEMS accelerometers with floating point ADC [J]. Integration, 2017, 59: 247-254.) to read the change in capacitance caused by the load, and calculate the movement information of the movable structure of the sensor through the capacitance value. However, such methods have the disadvantages of slow dynamic response and susceptibility to noise interference. SUMMARY

[0006] In order to overcome the above-mentioned prior art defects, the application proposes a capacitive micro-force sensor and a closed-loop detection circuit of a mixed sensing-driving array, through the mixed use and optimal design of a variable-pitch comb array and a variable-area comb array, the sensitivity, linearity and measurement range of the capacitive micro-force sensor are synergistically improved; at the same time, a variable-area driving array is arranged inside the sensor, by adjusting the initial position of the movable structure, the values of the electrostatic force and the electrostatic stiffness of the variable-pitch comb inside the device are changed, so as to adjust the effective stiffness of the device and match the sample stiffness; in combination with a new type of closed-loop detection circuit for the capacitive micro-force sensor of the mixed sensing-driving array, the motion state signal of the movable structure of the sensor after being loaded is detected by the sensing array and is fed back, the optimal driving force is generated in the variable-area driving array, so as to drive the movable structure to quickly and stably return to the initial position, the driving voltage in the stable state is used for output, the dynamic detection performance and detection accuracy of the capacitive micro-force sensor can be greatly improved, and the interference of the sensor internal noise and the circuit noise on the micro-force signal detection is reduced.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is:

[0008] A capacitive micro-force sensor of a mixed sensing-driving array, comprising a movable mass suspended in the front part of the sensor through a support beam, the other end of the support beam being fixed on a frame; the mass block extends an elongated probe at the front end, when a force signal is applied on the probe, the probe can drive the mass block and the support beam to move in the working sensitive direction, the shape and size of the probe are determined according to application requirements; two or more variable-pitch comb arrays and two or more variable-area comb arrays are arranged in the middle part of the sensor, the movable comb array is arranged on the movable comb cantilever at the end of the mass block, the corresponding fixed comb array is fixed on the frame, the size, number, arrangement position and combination mode of the variable-pitch comb array and the variable-area comb array are determined according to application requirements; two or more variable-area driving comb arrays are arranged at the end of the sensor, the movable comb array is arranged on the driving cantilever, the corresponding fixed comb array is fixed on the frame, the size, number and arrangement mode of the variable-area driving comb array are determined according to application requirements.

[0009] The variable interval comb array is composed of a moving comb array and a fixed comb array, two adjacent variable interval comb arrays form a variable interval differential comb array, in each variable interval differential comb array, the electrode plate of the moving comb deviates from the center of the electrode plate of the adjacent two fixed combs, the interval between the electrode plate of one of the moving combs and the electrode plates of the adjacent two fixed combs is d1 and d2, the interval between the electrode plate of one of the moving combs and the electrode plates of the adjacent two fixed combs which form a differential capacitor is d3 and d4, in the initial state, d1=d3≠d2=d4, the electrode plates of the two adjacent variable interval differential comb arrays have a center-symmetrical structure; when the sensor is loaded in the working sensitive direction, the intervals d1, d2, d3 and d4 of the moving combs and the fixed combs change, thereby causing the total capacitance of each variable interval differential comb array to change.

[0010] The variable area comb array is composed of a moving comb array and a fixed comb array, two adjacent variable area comb arrays form a variable area differential comb array, in each variable area differential comb array, the electrode plate of the moving comb is located at the center of the electrode plate of the adjacent two fixed combs, the interval is d0, the length of the overlapping area is equal, the length is l0, and the electrode plates of the two adjacent variable area differential comb arrays have a center-symmetrical structure; when the sensor is loaded in the y direction, the length l0 of the overlapping area of each moving comb and fixed comb changes, thereby changing the facing area of the moving comb and the fixed comb, and causing the total capacitance of each differential variable area comb array to change.

[0011] The variable area driving comb array has the same structure as the variable area comb array, a direct current voltage is applied to the fixed comb array, an electrostatic force is generated on the comb array, the electrostatic force drives the mass to move in the working sensitive direction, changes the effective stiffness of the sensor, and simultaneously realizes closed-loop in-situ measurement of the micro force.

[0012] A closed-loop detection circuit of a capacitive micro-force sensor of a hybrid sensing-driving array, during detection, a voltage V1 is applied on the mass, so that all the movable comb teeth have equal potentials; the fixed comb teeth array with the same interval change trend in the variable interval comb teeth array is connected through a wire and is connected to two groups of pre-stage charge amplification circuits composed of operational amplifiers, so that the capacitance value is converted into a voltage signal; the voltage signal and the excitation voltage V1 are demodulated through a lock-in amplifier; the two demodulation signals are differentially processed through an instrument amplifier; the differential signal is filtered through a low-pass filter to reduce the influence of sensor noise and circuit noise; and the filtered signal is input into a controller to calculate the position information; the fixed comb teeth array with the same area change trend in the variable area comb teeth array is connected through a wire; after the variable area comb teeth array is charged under the excitation voltage V1, the facing area of the movable comb teeth and the fixed comb teeth changes again, so that an induced current proportional to the area change speed is generated; the current signal is converted into a voltage signal through a current-voltage conversion circuit; the two voltage signals are sampled through a sampling oscilloscope to obtain the signal range of the variable capacitance area comb teeth array under the full-capacitance condition; the two sampled signals are differentially processed; the differential signal is input into a controller to calculate the speed information; the controller comprehensively utilizes the position information and the speed information to give an output signal of a control quantity; and a digital adjustable power supply applies a voltage V2\V3 on the fixed comb teeth array with the same area change trend in the variable area driving comb teeth array according to the output signal of the controller, so that a corresponding driving electrostatic force is generated, and high-dynamic and low-noise closed-loop measurement of the micro-force signal is realized.

[0013] A closed-loop detection circuit of a capacitive micro-force sensor of a hybrid sensing-driving array, by arranging variable interval comb teeth arrays, variable area comb teeth arrays, variable area driving comb teeth arrays and signal detection circuits with different intervals, thicknesses, lengths and numbers on the sensor and by using different controllers in the signal detection circuits, micro-force signal closed-loop detection with different ranges, different sensitivities and different response speeds is realized.

[0014] Compared with the prior art, the micro-force sensor has the following beneficial effects:

[0015] 1) Compared with the capacitive sensor with the common array comb tooth structure, the micro-force sensor adopts the variable interval and variable area composite array, the number and arrangement of the two arrays are designed, the measurement circuit is combined, and the speed and displacement comprehensive detection method of the capacitive electrode plate is innovatively proposed.

[0016] 2) The micro-force sensor innovatively proposes a sensing-driving integrated structure, the variable area driving comb teeth array is designed in the sensor, compared with the traditional capacitive sensor, the electrostatic stiffness of the sensor can be flexibly adjusted within a certain range, the effective stiffness of the sensor is matched with the stiffness of different samples, and the micro-force sensor is suitable for various micro-force measurement scenes.

[0017] 3)The application proposes a new type of closed-loop detection circuit for a new type of MEMS capacitive micro-force sensor with sensing and driving array integrated, which detects the movement state signal of the movable structure of the sensor after being loaded and feeds back, so that the driving array generates the optimal driving force, thereby driving the movable structure to quickly and smoothly return to the initial position, using the stable state driving voltage for output, completing the closed-loop measurement of micro-force, breaking through the sensitivity and nonlinearity limitations of traditional capacitive devices, reducing the interference of sensor noise and circuit noise, and improving the dynamic response speed and detection accuracy of the MEMS capacitive micro-force sensor. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1(a) is a top view of the MEMS micro-force sensor structure of the variable pitch and variable area composite capacitive array of the application; Figure 1(b) is a schematic diagram of the arrangement of the movable comb array, the fixed comb array and the metal pad of the variable pitch comb array in Figure 1(a); Figure 1(c) is a schematic diagram of the arrangement of the movable comb array, the fixed comb array and the metal pad of the variable area comb array in Figure 1(a); Figure 1(d) is a schematic diagram of the arrangement of the movable comb array, the fixed comb array and the metal pad of the variable area driving comb array in Figure 1(a); Figure 1(e) is a partial schematic diagram of the movable comb array, the fixed comb array and the differential comb array formed thereby of the variable pitch comb array in Figure 1(b); Figure 1(f) is a partial schematic diagram of the movable comb array, the fixed comb array and the differential comb array formed thereby of the variable area comb array in Figure 1(c); and Figure 1(g) is a partial schematic diagram of the movable comb array, the fixed comb array and the differential comb array formed thereby of the variable area driving comb array in Figure 1(d).

[0019] Figure 2(a) is a schematic diagram of the high dynamic low noise micro-force signal detection circuit of the MEMS micro-force sensor based on the variable pitch and variable area composite capacitive array of the application; Figure 2(b) is a specific circuit diagram of the differential capacitive detection circuit in Figure 2(a); Figure 2(c) is a specific circuit diagram of the differential current detection circuit in Figure 2(a); Figure 2(d) is an electrical connection schematic diagram of the variable area differential comb array in Figure 2(a); Figure 2(e) is an electrical connection schematic diagram of the variable pitch differential comb array in Figure 2(a); and Figure 2(f) is an electrical connection schematic diagram of the variable area driving comb array in Figure 2(a). DETAILED DESCRIPTION

[0020] The application will be described in detail below with reference to the embodiments and the accompanying drawings.

[0021] REFERENCE Figures 1(a)-1(g)A capacitive micro-force sensor of hybrid sensor-actuator array, comprising a movable mass 100 suspended in front of the sensor by six support beams 101, the other end of the support beams 101 being fixed on a frame 102, the mass 100 being electrically connected to external circuit through mass metal pads 103; the mass 100 extends an elongated probe 104 at the front end, when a force signal is applied on the probe 104, the probe 104 can drive the mass 100 and the support beams 101 to move in the working sensitive direction; three dynamic comb fingers cantilevers 105 are arranged in the middle of the sensor, connected to the end of the mass 100, used to arrange variable pitch and variable area comb array; the end of the sensor is arranged with a driving cantilever 111, connected to the end of the middle dynamic comb finger cantilever 105 and orthogonal in direction, used to arrange variable area driving array; the area around the mass 100 is the frame 102 of the chip movable structure material layer, used to fix various fixed comb array, the frame 102 and each fixed comb array are not conductive.

[0022] The variable pitch dynamic comb array 1061, 1062, 1063, 1064, 1065, 1066 is arranged from left to right in the left and right of the three dynamic comb finger cantilevers 105, and in the middle of the three dynamic comb finger cantilevers 105; the variable pitch fixed comb array 1071, 1072, 1073, 1074, 1075, 1076 is arranged around the corresponding variable pitch dynamic comb array, the variable pitch fixed comb array one 1071 and the variable pitch fixed comb array six 1076 are directly fixed in the middle of the frame 102, and are electrically connected to the external circuit through the variable pitch comb metal pad one 1081 and the variable pitch comb metal pad four 1084 respectively; the variable pitch fixed comb array 1072, 1073, 1074, 1075 is arranged around the two fixed comb finger cantilevers 109, and is electrically connected to the external circuit through the variable pitch comb metal pad two 1082 and the variable pitch comb metal pad three 1083 respectively.

[0023] The variable-pitch moving comb tooth array 1061, 1062, 1063, 1064, 1065, 1066 cooperates with the variable-pitch fixed comb tooth array 1071, 1072, 1073, 1074, 1075, 1076 to form a variable-pitch comb tooth array 1101, 1102, 1103, 1104, 1105, 1106, and each adjacent two variable-pitch comb tooth arrays form a differential comb tooth array; the electrode plates of the moving comb teeth in the variable-pitch comb tooth arrays 1101, 1104, 1105 and the electrode plates of the adjacent two fixed comb teeth have a pitch d1, d2, the electrode plates of the moving comb teeth in the variable-pitch comb tooth arrays 1102, 1103, 1106 and the electrode plates of the adjacent two fixed comb teeth have a pitch d3, d4, and in the initial state, d1 = d3 ≠ d2 = d4, and the electrode plates of the two adjacent variable-pitch differential comb tooth arrays have a center-symmetrical structure; when the sensor is loaded, the comb teeth in the variable-pitch comb tooth arrays 1101, 1104, 1105 have the same positive distance change, and the comb teeth in the variable-pitch comb tooth arrays 1102, 1103, 1106 have the same reverse distance change.

[0024] The variable-area moving and fixed comb tooth array groups are arranged on the upper and lower parts of the three moving comb tooth cantilevers 105 and the two fixed comb tooth cantilevers 109; the variable-area moving comb tooth arrays 1121, 1122, 1123, 1124, 1125, 1126 are arranged from left to right on the left and right of the three moving comb tooth cantilevers 105 and on the upper parts of the three moving comb tooth cantilevers 105; the variable-area fixed comb tooth arrays 1131, 1132, 1133, 1134, 1135, 1136 are arranged around the corresponding variable-area moving comb tooth arrays, the first variable-area fixed comb tooth array 1131 and the sixth variable-area fixed comb tooth array 1136 are directly fixed in the middle part of the frame 102 and are electrically connected to the external circuit through the first variable-area comb tooth metal pad 1141 and the fourth variable-area comb tooth metal pad 1144; the variable-area fixed comb tooth arrays 1132, 1133, 1134, 1135 are arranged on the left and right of the two fixed comb tooth cantilevers 109 and are electrically connected to the external circuit through the second variable-area comb tooth metal pad 1142 and the third variable-area comb tooth metal pad 1143.

[0025] The variable-area moving comb tooth arrays 1121, 1122, 1123, 1124, 1125, 1126 are respectively matched with the variable-area fixed comb tooth arrays 1131, 1132, 1133, 1134, 1135, 1136 to form variable-area comb tooth arrays 1151, 1152, 1153, 1154, 1155, 1156, and each adjacent two groups of variable-area comb tooth arrays form a differential comb tooth array; in each differential variable-area comb tooth array, the electrode plates of one moving comb tooth and the electrode plates of two adjacent fixed comb teeth have an equal spacing d0, and the overlapping regions have an equal length l0, and the electrode plates of the two adjacent differential variable-area comb tooth arrays have a center-symmetrical structure; when the sensor is loaded, the comb teeth in the variable-area comb tooth arrays 1151, 1154, 1155 have a positive same-area change, and the comb teeth in the variable-area comb tooth arrays 1152, 1153, 1156 have a reverse same-area change.

[0026] The variable-area comb tooth arrays 1161, 1162, 1163, 1164, 1165, 1166 are arranged below the variable-spacing comb tooth arrays 1101, 1102, 1103, 1104, 1105, 1106, and have the same number, size, arrangement mode, anchoring mode and working principle as the variable-area comb tooth arrays 1151, 1152, 1153, 1154, 1155, 1156.

[0027] The variable-area driving moving comb tooth arrays 1171, 1172, 1173, 1174 are arranged on the driving cantilever 111 from left to right and from top to bottom, the driving fixed comb tooth arrays 1181, 1182, 1183, 1184 are arranged around the corresponding driving moving comb tooth arrays, and the corresponding metal pads are 1191, 1192, 1193, 1194; the driving moving comb tooth arrays 1171, 1172, 1173, 1174 are matched with the driving fixed comb tooth arrays 1181, 1182, 1183, 1184 to form variable-area driving comb tooth arrays 1201, 1202, 1203, 1204; when a voltage is applied to the driving fixed comb tooth arrays 1181, 1182, a positive electrostatic force in the y direction can be generated, and when a voltage is applied to the driving fixed comb tooth arrays 1183, 1184, a reverse electrostatic force in the y direction can be generated, and the electrostatic force can drive the mass to produce positive and reverse displacements in the working sensitive direction.

[0028] Reference Figures 2(a)-2(f)The closed-loop detection circuit of the capacitive micro-force sensor of the hybrid sensor-driving array comprises a variable-pitch differential comb array 21, a variable-area differential comb array 22, a differential capacitance detection circuit 23, a differential current detection circuit 24, a controller 25, a digitally adjustable power supply 26, and a variable-area driving comb array 27. During detection, a voltage V1 is applied to the mass block through the mass block metal pad, and all the fixed comb arrays have the same electric potential through the mass block. In the variable-pitch differential comb array 21, the variable-pitch comb metal pad one 1081 and the variable-pitch comb metal pad three 1083 are electrically connected to each other, and the variable-pitch comb metal pad two 1082 and the variable-pitch comb metal pad four 1084 are electrically connected to each other, and are respectively connected to the differential capacitance detection circuit 23. In the variable-area differential comb array 22, the variable-area comb metal pad one 1141, the variable-area comb metal pad three 1143, the variable-area comb metal pad five 1145, and the variable-area comb metal pad seven 1147 are electrically connected to each other, and the variable-area comb metal pad two 1142, the variable-area comb metal pad four 1144, the variable-area comb metal pad six 1146, and the variable-area comb metal pad eight 1148 are electrically connected to each other, and are respectively connected to the differential current detection circuit. In the variable-area driving comb array 27, the variable-area driving comb metal pad one 1191 and the variable-area driving comb metal pad two 1192 are electrically connected to each other to apply the same voltage potential V2, and the variable-area driving comb metal pad three 1193 and the variable-area driving comb metal pad four 1194 are electrically connected to each other to apply the same voltage potential V3.

[0029] The differential capacitance detection circuit 23 converts two-way capacitance signals into two-way voltage signals through the same two front-stage charge conversion circuits 231, demodulates the two-way voltage signals and the excitation voltage V1 through a lock-in amplifier 232, compares the output of the two-way demodulation signals through an instrument amplifier 233 to output a differential voltage signal proportional to the differential capacitance value, and reduces the aliasing of sensor noise and circuit noise through a low-pass filter 234.

[0030] The differential current detection circuit 24 converts two-way current signals generated by the variable-area differential capacitance due to charging into two-way voltage signals through the same two current-voltage conversion circuits 241, samples the current signals generated by the capacitance value change under the full charging condition of the variable-area capacitance through a sampling oscilloscope 242, and outputs a voltage signal proportional to the speed of the sensor mass block 100 through a subtracter 243.

[0031] The controller 25 obtains the position and speed information of the mass 100 by calculating the output signals of the differential capacitance detection circuit 23 and the differential current detection circuit 24, and outputs a control signal by using a plurality of types of control algorithms according to the position and speed information.

[0032] The output end of the digital adjustable power supply 26 is connected to the variable-area driving comb tooth metal pad one 1191, the variable-area driving comb tooth metal pad three 1193, the variable-area driving comb tooth metal pad two 1192 and the variable-area driving comb tooth metal pad four 1194, respectively, and according to the control signal of the controller 25, voltage V2 is applied to the variable-area driving comb tooth metal pad one 1191 and the variable-area driving comb tooth metal pad three 1193 or voltage V3 is applied to the variable-area driving comb tooth metal pad two 1192 and the variable-area driving comb tooth metal pad four 1194.

[0033] The working principle of the application is as follows:

[0034] When the sensor is subjected to a y-direction force, the spacing d1, d2, d3 and d4 between the movable comb tooth electrode plate and the fixed comb tooth electrode plate in the variable-spacing comb tooth array changes, thereby changing the differential capacitance value of the array output; the overlapping area of the movable comb tooth electrode plate and the fixed comb tooth electrode plate in the variable-area comb tooth array changes, thereby changing the differential current of the array output; when a 180° square wave voltage V1 is applied to the mass 100, the differential capacitance value of the variable-spacing differential comb tooth array 21 is measured by the differential capacitance detection circuit 23, and the induced current of the variable-area differential comb tooth array 22 is measured by the differential current detection circuit 24; the position and speed information of the mass 100 is obtained by the controller 25 by calculating the two measurement signals, and the controller 25 outputs a control signal by using a plurality of types of control algorithms according to the speed and displacement information; the digital adjustable power supply 26 applies corresponding voltage V2 / V3 to the variable-area driving comb tooth array 27 according to the control signal, and the variable-area driving comb tooth array 27 generates an electrostatic force to push the mass 100 to generate a positive and negative displacement in the working sensitive direction to resist the influence of the load force, thereby completing the closed-loop measurement of the micro-force signal; the voltage V2 / V3 applied by the digital adjustable power supply 26 can be used as a measure of the size of the load force, and the effective stiffness of the sensor can be changed within a certain range.

[0035] The closed-loop detection circuit of the capacitive micro-force sensor with a hybrid sensor-driving array can realize high-dynamic and low-noise micro-force signal detection with different ranges, different sensitivities and different response speeds by arranging variable-spacing comb tooth arrays, variable-area comb tooth arrays, variable-area driving comb tooth arrays with different spacings, thicknesses, lengths and numbers on the sensor and using different controllers in the signal detection circuit.

[0036] The above merely describes one embodiment of the present application, which is not all or only one, and any equivalent transformation of the technical scheme of the present application by a person of ordinary skill in the art through reading the present application description is covered by the claims of the present application.

Claims

1. A capacitive micro-force sensor of a hybrid sensor-actuated array, characterized by: The movable mass is suspended in front of the sensor by a support beam, the other end of the support beam is fixed on the frame; the mass extends an elongated probe at the front end, when a force signal is applied on the probe, the probe can drive the mass and the support beam to move in the working sensitive direction, the shape and size of the probe are determined according to the application requirements; the middle part of the sensor is arranged with two or more variable spacing comb arrays and two or more variable area comb arrays, wherein the variable area comb arrays are located at both ends of the arrangement area and are used to sense the speed information of the mass, the variable spacing comb arrays are located in the middle area between the two variable area comb arrays and are used to sense the position information of the mass, the size, number, arrangement position and combination mode of the variable spacing comb arrays and the variable area comb arrays are determined according to the application requirements; the end of the sensor is connected with a driving cantilever through a central movable comb cantilever, the driving cantilever is symmetrically arranged with two or more variable area driving comb arrays on the upper and lower sides, the size, number and arrangement mode of the variable area driving comb array are determined according to the application requirements.

2. The sensor of claim 1, wherein: The variable spacing comb array is composed of a movable comb array and a fixed comb array, two adjacent variable spacing comb arrays form a variable spacing differential comb array, in each variable spacing differential comb array, the electrode plate of the movable comb deviates from the centers of the electrode plates of the two adjacent fixed combs, the spacing between the electrode plate of one movable comb and the electrode plates of the two adjacent fixed combs is d1 and d2, the spacing between the electrode plate of one movable comb and the electrode plates of the two adjacent fixed combs which form a differential capacitor is d3 and d4, in the initial state, d1=d3≠d2=d4, the electrode plates of the two adjacent variable spacing differential comb arrays have a center-symmetric structure; when the sensor is loaded in the working sensitive direction, the spacings d1, d2, d3 and d4 of the movable combs and the fixed combs change, thereby causing the total capacitance of each variable spacing differential comb array to change.

3. The sensor of claim 1, wherein: The variable area comb array is composed of a movable comb array and a fixed comb array, two adjacent variable area comb arrays form a variable area differential comb array, in each variable area differential comb array, the electrode plate of the movable comb is located at the center of the electrode plates of the two adjacent fixed combs, the spacing is d0, the lengths of the overlapping areas are equal, the length is l0, the electrode plates of the two adjacent variable area differential comb arrays have a center-symmetric structure; when the sensor is loaded in the y direction, the length l0 of the overlapping area of each movable comb and fixed comb changes, thereby changing the facing area of the movable comb and the fixed comb, causing the total capacitance of each differential variable area comb array to change.

4. The sensor of claim 1, wherein: The variable area driving comb array has the same structure as the variable area comb array, a direct current voltage is applied to the fixed comb array to generate an electrostatic force on the comb array, the electrostatic force drives the mass to produce a positive or negative displacement in the working sensitive direction, changes the effective stiffness of the sensor, and simultaneously realizes closed-loop in-situ measurement of the micro force.

5. The closed loop detection circuit for a capacitive micro-force sensor of a hybrid sensor-actuated array of claim 1, wherein: A voltage V1 is applied to the mass to make all movable combs have equal potentials; The fixed comb arrays with the same spacing change trend in the variable spacing comb array are connected by wires and connected to a differential capacitance detection circuit to measure the differential capacitance value; The variable-area comb array is connected with the fixed comb array through a wire, and is connected to a differential current detection circuit to measure the current; the controller uses the two measured values to calculate the position and speed information, and outputs a control signal; and the digital adjustable power supply applies a voltage V2 / V3 to the fixed comb array with the same area change trend as the variable-area driving comb array, to generate a corresponding driving electrostatic force, thereby realizing closed-loop measurement of the micro-force signal.

6. The circuit of claim 5, wherein: The differential capacitance detection circuit is connected with the fixed comb array, and is connected to two groups of pre-charge amplification circuits composed of operational amplifiers, to convert the capacitance value into a voltage signal; the voltage signal and the excitation voltage V1 are demodulated by a lock-in amplifier; the two demodulated signals are differentially processed by an instrument amplifier; the differential signal is filtered by a low-pass filter to reduce the influence of sensor noise and circuit noise; and the filtered signal is input into the controller to calculate the position information.

7. The circuit of claim 5, wherein: The differential current detection circuit detects the change in the area of the fixed comb array opposite the moving comb after the variable-area comb array is charged under the excitation voltage V1, to generate an induced current proportional to the area change speed; the current signal is converted into a voltage signal by a current-voltage conversion circuit; the two voltage signals are sampled by a sampling oscilloscope to obtain the signal range of the variable-capacitance area comb array under the full-capacitance condition; the two sampled signals are differentially processed; and the differential signal is input into the controller to calculate the speed information.

8. The circuit of claim 5, wherein: The controller uses the output signals of the differential capacitance detection circuit and the differential current detection circuit to calculate the position information and speed information of the sensor mass, and uses various types of controllers according to the use mode of the sensor to output a control signal; and the digital adjustable power supply applies a voltage V2 / V3 to the fixed comb array with the same area change trend as the variable-area driving comb array, to generate a corresponding driving electrostatic force, thereby realizing closed-loop measurement of the micro-force signal.

9. The circuit of claim 5, wherein: By arranging variable-pitch comb arrays, variable-area comb arrays, and variable-area driving comb arrays with different pitches, thicknesses, lengths, and quantities on the sensor, and using different controllers in the signal detection circuit, micro-force signal closed-loop detection with different ranges, sensitivities, and response speeds can be realized.

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