An electrostatic accelerometer with decoupled degrees of freedom

Abstract

The application provides a free degree decoupling electrostatic accelerometer, belonging to the field of acceleration sensing test, comprising: a sensitive probe, a capacitive displacement sensing circuit, a feedback electrostatic actuator, a PID controller, a DAC circuit and a bias voltage driver; the surface of a proof mass is separated into several independent parts, the DAC circuit applies positive and negative amplitude analog bias voltage to the proof mass respectively; the bias voltage applied on the opposite surfaces of the proof mass is equal in size and opposite in sign; the capacitive displacement sensing circuit tests the position of the proof mass in the sensitive probe; the PID controller calculates a feedback voltage to control the capacitive plate; and the feedback electrostatic actuator applies the feedback voltage to the capacitive plate to generate a feedback force. The conventional electrostatic accelerometer needs to use a plus-minus combination circuit to obtain the free degree information, and the electrostatic accelerometer has the ability of free degree decoupling.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of acceleration sensor test, and more particularly relates to a degree-of-freedom decoupled electrostatic accelerometer. BACKGROUND

[0002] An accelerometer is an inertial instrument for measuring acceleration of an object. The measurement principle of the accelerometer is based on Newton's second law, i.e. a force F acting on an object with mass m will cause the object to have an acceleration a = F / m.

[0003] To ensure sufficient measurement bandwidth, the accelerometer is usually designed to have a servo control function. The working principle of the electrostatic feedback accelerometer is that the position of a proof mass is tested by a fixed capacitive plate of a spacecraft, and a suitable electrostatic force (torque) is generated by an electrostatic actuator to stabilize the proof mass at the balance position in the middle of the plate. The proof mass and the external carrier are relatively stationary, i.e. the acceleration generated by the electrostatic actuator is consistent with the acceleration of the spacecraft, and finally the acceleration information can be obtained through the relevant data (voltage or current, etc.) of the electrostatic actuator. The electrostatic feedback force is generated by the bias voltage applied to the proof mass and the feedback voltage on the plate.

[0004] As the core device of an inertial system, different service purposes have different requirements for the performance of the accelerometer. (1) Reducing the power consumption of the accelerometer; (2) Having the function of automatically optimizing the resolution of the acceleration. Based on the above goals, on the one hand, higher requirements are put forward for the selection and quantity of the device; on the other hand, the sensitive unit in the accelerometer is considered to be changed, so as to optimize the design of the electronic system. As the core link of keeping the proof mass in the balance position in the inertial sensor, the bias voltage of the accelerometer is usually fixed or set to a specific gear for range switching, and the bias voltage is applied to the proof mass by a conductive gold wire, so that the range of the six axes of the accelerometer is changed at the same time. Under this method, the ranges of the six axes of the accelerometer cannot be independent of each other. SUMMARY

[0005] In view of the defects of the prior art, the present application provides a degree-of-freedom decoupled electrostatic accelerometer, which aims to solve the problem that the ranges of the six axes of the accelerometer cannot be independent of each other. Based on this, the degree-of-freedom decoupled electrostatic accelerometer provided by the present application also has the advantages of automatically optimizing the resolution and reducing the power consumption of the acceleration.

[0006] To achieve the above-mentioned purpose, the present application provides a degree-of-freedom decoupled electrostatic accelerometer, which comprises a sensitive probe, a capacitive displacement sensing circuit, a feedback electrostatic actuator, a PID controller, a DAC circuit, a bias voltage driver, a data acquisition unit and a bias voltage calculation and control unit.

[0007] The sensitive probe comprises a capacitor plate and a test mass. Two capacitor plates are arranged in parallel on each side of the test mass. The input end of the capacitor displacement sensing circuit is connected to the capacitor plate, and the output end is connected to the PID controller. The output end of the PID controller is connected to the feedback electrostatic actuator. The output of the feedback electrostatic actuator is connected to the capacitor plate. The output end of the bias voltage driver is connected to the test mass. The data acquisition unit is connected to the capacitor plate and the feedback electrostatic actuator. The output end of the data acquisition unit is connected to the bias voltage calculation control unit. The output end of the bias voltage calculation control unit is connected to the bias voltage driver. The six sides of the test mass are insulated from each other.

[0008] The bias voltage driver is used to output three groups of bias voltages, which are bias voltages in x, y and z directions respectively. The DAC circuit is used to convert the bias voltages into analog signals, and to apply the positive and negative amplitude voltages of the analog bias voltages to the test mass, so as to generate electrostatic stiffness to adjust the position of the test mass. The bias voltages applied to the opposite sides of the test mass are equal in size and opposite in sign, so that the feedback voltages applied to the opposite capacitor plates are the same, and the bias voltages in x, y and z directions are independently adjusted. The capacitor displacement sensing circuit is used to test the position of the test mass in the sensitive probe. The PID controller is used to calculate the feedback voltage according to the position of the test mass, and to control the capacitor plate. The feedback electrostatic actuator is used to apply the feedback voltage to the capacitor plate to generate feedback forces in six degrees of freedom, so that the test mass is in a balanced position. The bias voltage calculation control unit is used to calculate the bias voltages in x, y and z directions according to the current working state of the test mass and the external input acceleration.

[0009] Further preferably, the material of the test mass is microcrystalline glass bottom lining, and the surface is plated with gold.

[0010] Further preferably, within the preset range of the balance point, the feedback forces in six degrees of freedom are:

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017] wherein d is the balance distance between the capacitor plate and the mass, C0 is the capacitance between the capacitor plate and the mass when the test mass is in the balanced position, V bVbias is the bias voltage; V f1 Vfbz1 is the feedback voltage applied to the z1 pair of plates, V f2 Vfbz2 is the feedback voltage applied to the z2 pair of plates, V f3 Vfbx1 is the feedback voltage applied to the x1 pair of plates, V f4 Vfbx2 is the feedback voltage applied to the x2 pair of plates, V f5 Vfby1 is the feedback voltage applied to the y1 pair of plates, V f6 Vfby2 is the feedback voltage applied to the y2 pair of plates, V z-translation Fz is the translational force on the proof mass in the z direction, F x-translation Fx is the translational force on the proof mass in the x direction, F y-translation Fy is the translational force on the proof mass in the y direction, T Rx-rotation Tz is the rotational force on the proof mass in the Rz direction, T Ry-rotation Ty is the rotational force on the proof mass in the Ry direction, T Rz-rotation Tx is the rotational force on the proof mass in the Rx direction; F z1+ Fz+ is the translational feedback force applied to the z1+ plate, F z1- Fz- is the translational feedback force applied to the z1- plate, F z2+ Fz2+ is the translational feedback force applied to the z2+ plate, F z2- Fz2- is the translational feedback force applied to the z2- plate; F x1+ Fx1+ is the translational feedback force applied to the x1+ plate, F x1- Fx1- is the translational feedback force applied to the x1- plate, F x2+ Fx2+ is the translational feedback force applied to the x2+ plate, F x2- Fx2- is the translational feedback force applied to the x2- plate; F y1+ Fy1+ is the translational feedback force applied to the y1+ plate, F y1- Fy1- is the translational feedback force applied to the y1- plate, F y2+ Fy2+ is the translational feedback force applied to the y2+ plate, F y2- Fy2- is the translational feedback force applied to the y2- plate; T z1+ Tz1+ is the rotational feedback force applied to the z1+ plate, T z1- Tz1- is the rotational feedback force applied to the z1- plate, T z2+ Tz2+ is the rotational feedback force applied to the z2+ plate, T z2- Tz2- is the rotational feedback force applied to the z2- plate; T x1+ Tx1+ is the rotational feedback force applied to the x1+ plate, T x1- Tx1- is the rotational feedback force applied to the x1- plate, T x2+ Tx2+ is the rotational feedback force applied to the x2+ plate, T x2- Tx2- is the rotational feedback force applied to the x2- plate; Ty1+ T is the rotational feedback force applied on the y1+ plate y1- T is the rotational feedback force applied on the y1- plate y2+ T is the rotational feedback force applied on the y2+ plate y2- T is the rotational feedback force applied on the y2- plate.

[0018] In another aspect, the present application provides a degree-of-freedom decoupled electrostatic accelerometer, comprising: a sensitive probe, a capacitive displacement sensing circuit, a feedback electrostatic actuator, a PID controller, a DAC circuit and a bias voltage driver;

[0019] The sensitive probe comprises capacitive plates and a proof mass. Each face of the proof mass is provided with two capacitive plates in parallel. The input end of the capacitive displacement sensing circuit is connected to the capacitive plates, and the output end thereof is connected to the PID controller. The output end of the PID controller is connected to the feedback electrostatic actuator. The output of the feedback electrostatic actuator is connected to the capacitive plates. The output end of the bias voltage driver is connected to the proof mass.

[0020] Three of the six faces of the proof mass sharing a common vertex are used as a first group of faces, and the other three are used as a second group of faces. The first group of faces and the second group of faces are insulated from each other.

[0021] The bias voltage driver is used to output a set of bias voltages. The DAC circuit is used to convert the bias voltages into analog signals and apply the positive and negative amplitude voltages of the analog bias voltages to the proof mass to generate electrostatic stiffness to adjust the position of the proof mass. The bias voltages applied to each pair of opposite faces of the proof mass are equal in magnitude and opposite in sign, so that the feedback voltages applied to the opposite capacitive plates are the same. The capacitive displacement sensing circuit is used to test the position of the proof mass in the sensitive probe. The PID controller is used to calculate the feedback voltage to control the capacitive plates according to the position of the proof mass. The feedback electrostatic actuator is used to apply the feedback voltage to the capacitive plates to generate translational feedback force and rotational feedback force, so that the proof mass is in a balanced position.

[0022] Further preferably, the electrostatic accelerometer further comprises a data acquisition unit connected to the capacitive plates and the feedback electrostatic actuator, which is used to acquire the voltage signals applied to the capacitive plates by the feedback electrostatic actuator to obtain the translational feedback force and rotational feedback force information.

[0023] Further preferably, the proof mass is made of microcrystalline glass with a gold-plated surface.

[0024] Further preferably, within the preset range of the equilibrium point, the translational feedback force and the rotational feedback force are:

[0025]

[0026]

[0027] wherein d is the equilibrium spacing between the capacitor plates and the proof mass, C0 is the capacitance between the capacitor plates and the proof mass when the proof mass is in the equilibrium position, V b is the bias voltage, V f1 is the feedback voltage applied to the z1+ plate, V f2 is the feedback voltage applied to the z2+ plate, F translation is the translational resultant force on the proof mass, F z1+ is the translational feedback force applied to the z1+ plate, F z1- is the translational feedback force applied to the z1- plate, F z2+ is the translational feedback force applied to the z2+ plate, F z2- is the translational feedback force applied to the z2- plate, T rotation is the rotational resultant force on the proof mass, T z1+ is the rotational feedback force applied to the z1+ plate, T z1- is the rotational feedback force applied to the z1- plate, T z2+ is the rotational feedback force applied to the z2+ plate, T z2- is the rotational feedback force applied to the z2- plate.

[0028] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following

[0029] Advantages:

[0030] The present application provides a degree-of-freedom decoupled electrostatic accelerometer, and a degree-of-freedom decoupled method, wherein the six faces of the proof mass are divided into six insulating parts, different bias voltages are applied to each face, and the bias voltages applied to the two faces of the proof mass in the same direction are equal in magnitude but opposite in sign. In this way, the same feedback voltage is applied to the positive and negative capacitor plates in the same direction, and the common-mode part of the feedback voltage applied to the adjacent two plates represents the translational information of the proof mass, and the differential-mode part represents the rotational information of the proof mass. Based on this, the purpose of degree-of-freedom decoupling is achieved. In this design, the accelerometer will have decoupling capability. At the same time, because different bias voltages are applied to the six faces of the proof mass, and the optimal bias voltage can be calculated by the bias voltage controller, the purpose of changing the acceleration range and automatically optimizing the resolution is achieved. In the present application, there is a special case. When the sizes of the bias voltages applied to the proof mass are all equal, the same decoupling capability is also achieved. Compared with the six-face insulation scheme, this special case has the advantage of reducing the overall power consumption of the accelerometer, which has an extraordinary effect on controlling the power consumption of the accelerometer in interstellar travel. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a method for completely decoupling the degree of freedom of the electrode plate pair provided by the embodiment of the application;

[0032] Figure 2 is a method for partially decoupling the degree of freedom of the electrode plate pair provided by the embodiment of the application;

[0033] Figure 3 is a method for completely decoupling the degree of freedom of the mass block and the electrode plate provided by the embodiment of the application;

[0034] Figure 4 is a method for partially decoupling the degree of freedom of the mass block and the electrode plate provided by the embodiment of the application;

[0035] Label description:

[0036] 1 - test mass block; 2 - electrode plate; 3 - capacitive displacement sensor; 4 - controller; 5 - actuator; 6 - data acquisition unit; 7 - bias voltage driver; 8 - bias voltage calculation control unit. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the application clearer, the application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0038] The application provides a degree of freedom decoupled electrostatic accelerometer, including two schemes, one is to provide a free range method of automatically adjusting the actuator, which meets the requirement that only one feedback circuit is needed to control the positive and negative electrode plates when different external acceleration inputs are input, so that the degrees of freedom are completely decoupled. At the same time, the resolution of the accelerometer can be automatically optimized according to different external acceleration inputs, which is called a method for completely decoupling the degree of freedom; the other is a design for reducing the number of electrostatic actuator devices and power consumption, which is a special case of complete decoupling, removes the addition and subtraction combination circuit in the circuit, reduces the overall power consumption of the electrostatic actuator, and is called a method for partially decoupling the degree of freedom.

[0039] More specifically, both methods change the design of the test mass block of the sensitive probe in the accelerometer, so that the feedback circuits of the positive and negative electrode plates of the electrostatic actuator share one circuit, and the desired performance is achieved; the accelerometer includes: a sensitive probe, a capacitive displacement sensing circuit 3, a PID controller 4, a feedback electrostatic actuator 5, a bias voltage calculation control unit 8 and a DAC circuit (digital-to-analog conversion circuit);

[0040] The sensitive probe comprises a capacitor plate 2 and a test mass 1; a capacitor displacement sensing circuit 3 is used to test the position of the test mass 1 in the sensitive probe; a PID controller 4 is used to calculate a suitable feedback voltage to control the capacitor plate 2; a feedback electrostatic actuator 5 is used to apply the feedback voltage obtained by the controller to the capacitor plate 2 to generate an electrostatic force; a bias voltage controller 8 and a DAC circuit are used to adjust the working state of the accelerometer to achieve performance optimization.

[0041] The bias voltage calculation control unit 8 is used to estimate a suitable bias voltage through the current working state and the tested external input acceleration; the DAC circuit is used to convert the bias voltage into an analog signal, and then apply the positive and negative amplitude voltages of the voltage to the two separated parts of the test mass 1 to generate a suitable electrostatic stiffness, so that the test mass 1 is in a balanced position.

[0042] Compared with the traditional electrostatic feedback accelerometer, the core of the present application lies in the design of the test mass in the two schemes; in the design, the material of the test mass is microcrystalline glass bottom lining, and the surface is plated with gold; the six surfaces or parts of the test mass are insulated or completely insulated, so as to achieve the purpose of decoupling of the degrees of freedom; in the method of complete decoupling of the degrees of freedom, as shown in Figure 1 , the six surfaces of the test mass are insulated from each other, and the bias voltages applied on each two opposite surfaces are equal in size and opposite in sign; the feedback voltages applied on the opposite plates can be the same, that is, the bias voltages in X, Y and Z directions can be independently adjusted, compared with the traditional accelerometer, the range of the different degrees of freedom of the feedback actuator can be independently adjusted, so as to optimize the resolution; in the method of partial decoupling of the degrees of freedom, as shown in Figure 2 , three of the six surfaces of the test mass share a vertex and are conductive, and the other three surfaces are conductive, and the two parts are insulated from each other; the bias voltages applied on each two opposite surfaces are equal in size and opposite in sign, which can make the feedback voltages applied on the opposite plates the same, that is, the purpose of reducing the power consumption of the circuit can be achieved; at the same time, in the two schemes, because the two surfaces of the test mass are insulated in the partial decoupling method, the advantage of partial decoupling of the degrees of freedom of the actuator is achieved; similarly, in the complete decoupling method, the six surfaces of the test mass are insulated, so as to achieve the advantage of complete decoupling of the degrees of freedom of the actuator. The two methods introduced above can be applied to all types of accelerometers.

[0043] The method of complete decoupling of the degrees of freedom is introduced as follows:

[0044] The voltage injection of the sensitive probe of the accelerometer is shown in Figure 3 , that is, the feedback force between each plate and the test mass is:

[0045]

[0046] Then at the equilibrium position, X, Y, Z, θ, η and The electrostatic control formula of six degrees of freedom is:

[0047]

[0048] Wherein, d is the equilibrium spacing between the capacitor plate and the mass, C0 is the capacitance between the capacitor plate and the mass when the test mass is in the equilibrium position, V b is the bias voltage; V f1 is the feedback voltage applied to the z1 two plates, V f2 is the feedback voltage applied to the z2 two plates, V f3 is the feedback voltage applied to the x1 two plates, V f4 is the feedback voltage applied to the x2 two plates, V f5 is the feedback voltage applied to the y1 two plates, V f6 is the feedback voltage applied to the y2 two plates; F z-translation is the translational resultant force on the test mass in the z direction, F x-translation is the translational resultant force on the test mass in the x direction, F y-translation is the translational resultant force on the test mass in the y direction, T Rx-rotation is the rotational resultant force on the test mass in the Rx direction, T Ry-rotation is the rotational resultant force on the test mass in the Ry direction, T Rz-rotation is the rotational resultant force on the test mass in the Rz direction; F z1+ is the translational feedback force applied to the z1+ plate, F z1- is the translational feedback force applied to the z1- plate, F z2+ is the translational feedback force applied to the z2+ plate, F z2- is the translational feedback force applied to the z2- plate; F x1+ is the translational feedback force applied to the x1+ plate, F x1- is the translational feedback force applied to the x1- plate, F x2+ is the translational feedback force applied to the x2+ plate, F x2- is the translational feedback force applied to the x2- plate; F y1+ is the translational feedback force applied to the y1+ plate, F y1- is the translational feedback force applied to the y1- plate, F y2+ is the translational feedback force applied to the y2+ plate, F y2- is the translational feedback force applied to the y2- plate; T z1+ is the rotational feedback force applied to the z1+ plate, T z1- is the rotational feedback force applied to the z1- plate, Tz2+ T is the rotational feedback force applied to the z2+ plate. z2- T is the rotational feedback force applied to the z2 plate; x1+ T is the rotational feedback force applied to the x1+ plate. x1- T is the rotational feedback force applied to the x1-plate. x2+ T is the rotational feedback force applied to the x2+ plate. x2- The rotational feedback force applied to the x2 plate; T y1+ T is the rotational feedback force applied to the y1+ plate. y1- T is the rotational feedback force applied to the y1-plate. y2+ T is the rotational feedback force applied to the y2+ plate. y2- The rotational feedback force applied to the y2-plate. The z1+ and z2+ plates are placed parallel to the same surface of the inspection mass block in the z-direction; the z1- and z2- plates are placed parallel to the other same surface of the inspection mass block in the z-direction; the z1+ and z1- plates are directly opposite each other; the z2+ and z2- plates are directly opposite each other; the y1+ and y2+ plates are placed parallel to the same surface of the inspection mass block in the y-direction; the y1- and y2- plates are placed parallel to the other same surface of the inspection mass block in the y-direction; the y1+ and y1- plates are directly opposite each other; the y2+ and y2- plates are directly opposite each other; the x1+ and x2+ plates are placed parallel to the same surface of the inspection mass block in the x-direction; the x1- and x2- plates are placed parallel to the other same surface of the inspection mass block in the x-direction; the x1+ and x1- plates are directly opposite each other; the x2+ and x2- plates are directly opposite each other; the xyz coordinate system is a three-dimensional Cartesian coordinate system;

[0049] As can be seen from formula (2), this method simplifies the feedback circuit and achieves the purpose of adjusting different degrees of freedom by changing the design of the inspection mass block and providing different bias voltages in the X, Y and Z directions, while ensuring that the opposing plates have the same feedback voltage. Furthermore, after the data is read, the bias voltage V on different degrees of freedom is calculated based on the read data. b The magnitude is then converted into an analog signal and applied to the inspection quality, thereby achieving automatic adjustment of the range of different degrees of freedom, i.e., the resolution of the automated accelerometer;

[0050] The following describes a method for decoupling degrees of freedom:

[0051] Depend on Figure 4 It can be seen that, regarding electrostatic control, since single-degree-of-freedom control is accomplished by the electrostatic force between the four plates on that degree of freedom and the inspection mass, the control theories of complete decoupling and partial decoupling are completely identical. That is, the translational feedback force and the rotational feedback force are:

[0052]

[0053] where ε is the dielectric constant, S is the area of the plate, m is the mass of the mass, d is the equilibrium spacing between the plate and the mass, V b is the bias voltage, V f is the feedback voltage, z is the distance of the mass from the equilibrium position; d is the equilibrium spacing between the plate and the mass, C0is the capacitance between the plate and the mass when the mass is in the equilibrium position, V b is the bias voltage, V f1 is the feedback voltage applied to the z1 plate, V f2 is the feedback voltage applied to the z2 plate, F translation is the translational resultant force on the proof mass, F z1+ is the translational feedback force applied to the z1+ plate, F z1- is the translational feedback force applied to the z1- plate, F z2+ is the translational feedback force applied to the z2+ plate, F z2- is the translational feedback force applied to the z2- plate, T rotation is the rotational resultant force on the proof mass, T z1+ is the rotational feedback force applied to the z1+ plate, T z1- is the rotational feedback force applied to the z1- plate, T z2+ is the rotational feedback force applied to the z2+ plate, T z2- is the rotational feedback force applied to the z2- plate. The z1+ plate and the z2+ plate are placed in parallel on the same surface in the z direction of the proof mass; the z1- plate and the z2- plate are placed in parallel on the other same surface in the z direction of the proof mass; the z1+ plate and the z1- plate are opposite to each other and serve as the two plates of z1; the z2+ plate and the z2- plate are opposite to each other and serve as the two plates of z2; the xyz coordinate system is a three-dimensional Cartesian coordinate system;

[0054] The first term in formula (3) is the electrostatic control term, and by determining V b , the V f is adjusted so that the mass is in the equilibrium position; it can be seen that when V b of equal amplitude and opposite signs is applied to the proof mass, the feedback voltage applied to the plates is completely the same, and in this case, the opposite positive and negative plates can share one feedback circuit to achieve control; the common mode part of the feedback voltage applied to the adjacent two plates represents the translational information of the proof mass, and the differential mode part represents the rotational information of the proof mass. Based on this, the purpose of decoupling the degrees of freedom is achieved. This method achieves the purpose of feedback control by changing the design of the mass and providing the same feedback voltage to the plates, completes the decoupling of the degrees of freedom, reduces the components of the circuit, and reduces the overall power consumption;

[0055] In summary, in the method of decoupling degrees of freedom, the six faces of the proof mass are divided into six insulating parts or two parts. The bias voltage applied on the two faces of the proof mass in the same direction is equal in magnitude and opposite in sign, and at this time the same feedback voltage is applied on the positive and negative capacitive plates in the same direction, thereby achieving the purpose of feedback control. In the scheme of dividing the proof mass into six parts, because the bias voltages applied on the six directions of the proof mass are not all the same, the ranges of the accelerometer are not the same, and the accelerometer has the purposes of complete decoupling and automatic optimization of resolution; in the scheme of dividing the proof mass into two parts, the bias voltages applied on the proof mass are all equal in magnitude, and the scheme also has the advantage of reducing the overall power consumption of the accelerometer.

[0056] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A degree of freedom decoupled electrostatic accelerometer characterized by, The application relates to a sensitive probe, a capacitive displacement sensing circuit, a feedback electrostatic actuator, a PID controller, a DAC circuit, a bias voltage driver, a data acquisition unit and a bias voltage calculation control unit. The sensitive probe comprises capacitive plates and a test mass. Two capacitive plates are arranged on each side of the test mass. The input end of the capacitive displacement sensing circuit is connected with the capacitive plates, and the output end is connected with the PID controller. The output end of the PID controller is connected with the feedback electrostatic actuator. The output of the feedback electrostatic actuator is connected with the capacitive plates. The output end of the bias voltage driver is connected with the test mass. The data acquisition unit is connected with the capacitive plates and the feedback electrostatic actuator. The output end of the data acquisition unit is connected with the bias voltage calculation control unit. The output end of the bias voltage calculation control unit is connected with the bias voltage driver. The six sides of the test mass are insulated from each other. The bias voltage driver is used for outputting three groups of bias voltages, i.e. bias voltages in x, y and z directions. The DAC circuit is used for converting the bias voltages into analog signals, and the positive and negative amplitude voltages of the analog bias voltages are applied to the test mass to generate electrostatic stiffness to adjust the position of the test mass. The bias voltages applied to the opposite sides of the test mass are equal in size and opposite in sign, so that the feedback voltages applied to the opposite capacitive plates are the same, and the bias voltages in x, y and z directions are independently adjusted. The capacitive displacement sensing circuit is used for testing the position of the test mass in the sensitive probe. The PID controller is used for calculating the feedback voltage according to the position of the test mass to control the capacitive plates. The feedback electrostatic actuator is used for applying the feedback voltage to the capacitive plates to generate feedback forces in six degrees of freedom, so that the test mass is in a balanced position. The bias voltage calculation control unit is used for calculating the bias voltages in x, y and z directions according to the working state of the test mass and the external input acceleration. In the preset range of the balanced point, the feedback forces in six degrees of freedom are: The material of the test mass is microcrystalline glass, and the surface is plated with gold. wherein d is the equilibrium spacing between the capacitor plate and the mass, is the capacitance between the capacitor plate and the mass when the mass is in the equilibrium position, is the bias voltage; , , , , and are the feedback voltages applied to the z1, z2, x1, x2, y1, and y2 plates, respectively; , and are the translational forces on the mass in the z, x, and y directions, respectively; , and are the rotational forces on the mass in the Rx, Ry, and Rz directions, respectively; , , , , , , , , , , and are the translational feedback forces applied to the z1+, z1-, z2+, z2-, x1+, x1-, x2+, x2-, y1+, y1-, y2+, and y2- plates, respectively; , , , , , , , , , and are the rotational feedback forces applied to the z1+, z1-, z2+, z2-, x1+, x1-, x2+, x2-, y1+, y1-, y2+, and y2- plates, respectively.

2. The electrostatic accelerometer of claim 1, wherein, ​

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