Multi-bit micro-electro-mechanical accelerometer
By using a multi-bit quantizer and adding a feedback electrode at the sensitive structure in the microelectromechanical accelerometer, the problems of limited range and signal-to-noise ratio were solved, resulting in a larger range and lower power consumption, and improving the stability and control accuracy of the system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-04-14
AI Technical Summary
Existing microelectromechanical accelerometers are limited in terms of range and signal-to-noise ratio performance by single-bit quantizers, and replacing them with multi-bit quantizers may introduce problems such as nonlinearity, increased power consumption, and increased complexity.
By employing a multi-bit quantizer and adding a feedback electrode at the sensitive structure to replace the DAC module, electrostatic feedback closed-loop control is achieved, avoiding the nonlinearity and power consumption loss caused by the multi-bit quantizer.
The accelerometer's range and signal-to-noise ratio were increased, while circuit power consumption and nonlinearity were reduced, thus improving system stability and control accuracy.
Smart Images
Figure CN121856590A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of performance improvement technology of microelectromechanical accelerometers, and provides a multi-bit microelectromechanical accelerometer. Background Technology
[0002] A capacitive microelectromechanical accelerometer (MEMS) is an inertial sensor used to measure external acceleration information. Its sensing structure mainly consists of fixed electrodes, a movable mass, and an elastic cantilever beam, which can be equivalent to a second-order "spring-mass-damped" system. It converts the external acceleration signal into capacitive comb-tooth displacement. A differential capacitor is formed between the movable mass and the upper and lower fixed electrodes. The comb-tooth displacement causes a change in the capacitance difference. The CV circuit converts this change in capacitance difference into a voltage signal and transmits it to the controller. The controller generates a corresponding feedback voltage based on the voltage information and inputs it to the feedback electrode of the sensing structure, generating an electrostatic feedback force that balances the inertial force generated by the acceleration signal, achieving closed-loop control. At this point, the magnitude of the feedback voltage is proportional to the acceleration information, thus realizing the measurement of acceleration information.
[0003] Modulation techniques, through oversampling and noise shaping, shape the quantization noise generated by the low-bit quantizer to the high-frequency range, and then filter it out through a low-pass filter, thereby significantly improving the effective resolution of the system. Because Modulation technology is highly compatible with integrated circuit processes and has been widely used in microelectromechanical devices (MEMS). In capacitive MEMS accelerometers, the sensing structure can be equivalent to a second-order integrator. By cascading an electrical integrator after the sensing structure and the CV circuit, a complete circuit can be formed. Microelectromechanical accelerometer. In this case, the sensitive structure not only converts external acceleration information into capacitive comb displacement, but also acts as an integrator in the noise shaping process.
[0004] Currently, both domestically and internationally Single-bit quantizers are often used in the design of microelectromechanical accelerometers, which are constrained in terms of range and signal-to-noise ratio performance. Summary of the Invention
[0005] Purpose of the invention: A multi-bit microelectromechanical accelerometer is provided. By using a multi-bit quantizer, the range and signal-to-noise ratio of the accelerometer are improved. A feedback electrode is added at the sensitive structure to avoid the performance loss such as nonlinearity and power consumption caused by the addition of a DAC when using a multi-bit quantizer.
[0006] Technical solution: A multi-bit microelectromechanical accelerometer includes: a sensor structure, a CV conversion circuit, and a first-order... Control circuit, multi-bit quantizer, torque converter coefficient module, and acceleration conversion module. The difference between the input acceleration and the feedback acceleration signal is input to the meter's sensitive structure; the output of the meter's sensitive structure is connected to the input of the CV conversion circuit. The output of the CV conversion circuit is connected to the first-order... The feedforward input of the control circuit is connected in order 1. The output of the control circuit is connected to the input of the multi-bit quantizer; the output of the multi-bit quantizer is connected to the first-order quantizer. The feedback input terminal of the control circuit is connected to the input terminal of the torque coefficient module; the output terminal of the torque coefficient module is connected to the input terminal of the acceleration conversion module, and the acceleration conversion module outputs a feedback acceleration signal. The front end of the meter's sensitive structure has multiple pairs of feedback electrodes corresponding to multiple bits.
[0007] Furthermore, by adjusting the static voltage of different feedback electrodes in the sensitive structure of the accelerometer head, the torque coefficient of the accelerometer head can be changed.
[0008] Furthermore, the direction of the electrostatic force generated by the feedback electrode of the meter's sensitive structure is opposite to the direction of motion of the movable mass block, and the magnitude of the electrostatic force is related to the feedback voltage. It is directly proportional.
[0009] Furthermore, when the mass of the movable mass block is much smaller than the static gap of the capacitor comb teeth, the electrostatic force generated by the feedback electrode pair of the meter head sensing structure is: ,in, It is the static voltage of the feedback electrode. It is the voltage of the movable mass block. It is the feedback voltage output from the circuit to the feedback electrode. It is the number of capacitor comb teeth. Where is the dielectric constant. This represents the area of the capacitor plates facing each other.
[0010] Furthermore, the torque coefficient of the feedback electrode generating electrostatic force for: ,in, It is the static gap of the capacitor comb teeth.
[0011] Furthermore, the total torque coefficient of the electrostatic force on the meter's sensitive structure is: .
[0012] Furthermore, the meter's sensitive structure employs a differential comb capacitor.
[0013] Furthermore, the equivalent gain of the multi-bit quantizer It is more accurate than the equivalent gain of a single-bit quantizer.
[0014] Furthermore, the equivalent gain of the multi-bit quantizer The threshold interval is determined based on the width of the quantization step.
[0015] Beneficial effects: (1) By replacing the single-bit quantizer with a multi-bit quantizer, the microelectromechanical accelerometer can obtain a larger range and signal-to-noise ratio; (2) By adding a feedback electrode at the sensitive structure, the DAC function can be replaced, reducing circuit power consumption and nonlinearity; (3) The control architecture is universal and can be adapted to both accelerometers and gyroscopes. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 For the multi-bit of the present invention Microelectromechanical accelerometer control block diagram; Figure 2 This is a schematic diagram of the transmission curves and linear model of the multi-bit quantizer and single-bit quantizer of the present invention; Figure 3 This is a schematic diagram of the multi-pair feedback electrode meter head sensing structure of the present invention; Figure 4 This is a schematic diagram of the electrostatic force of the feedback electrode of the meter head sensitive structure of the present invention. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.
[0020] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.
[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.
[0022] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0023] This invention provides a multi-bit quantizer The control architecture for a capacitive microelectromechanical accelerometer includes the following steps: S1, implementing single bit Design of a control architecture for a capacitive microelectromechanical accelerometer to achieve closed-loop control; S2 uses a multi-bit quantizer instead of a single-bit quantizer in the control architecture to improve the system range and signal-to-noise ratio; S3 improves the design of the meter's sensitive structure, adds a pair of feedback electrodes, and uses multi-electrode feedback to realize the DAC function; S4, based on the obtained multi-bit The control architecture of the capacitive microelectromechanical accelerometer is adjusted to achieve closed-loop control.
[0024] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.
[0025] Figure 1 This is the multi-bit of the present invention. Block diagram of microelectromechanical accelerometer control.
[0026] like Figure 1 As shown, this invention implements multi-bit... A capacitive microelectromechanical accelerometer control architecture may include the following steps: Step 1: Build a single bit The control architecture of a capacitive microelectromechanical accelerometer mainly includes the meter sensing structure, CV conversion circuit, and first-order... Control circuit, single-bit quantizer, torque coefficient, and mass of the movable mass block of the sensitive structure, etc.; Step 2: Replace the single-bit quantizer in the original control architecture with a multi-bit quantizer; Step 3: Replace the original single-pair feedback electrode meter sensing structure with a meter sensing structure consisting of multiple pairs of feedback electrodes. Step 4: Replace the torque coefficient of the single pair of feedback electrodes in the original control architecture with the torque coefficient of multiple pairs of feedback electrodes.
[0027] Figure 2 This is a schematic diagram of the transmission curves and linear model of the multi-bit quantizer and single-bit quantizer of the present invention.
[0028] like Figure 2 As shown, a single-bit quantizer contains only one quantization threshold, which models the equivalent gain. Since the output only switches between two levels, its gain behavior exhibits strong nonlinear characteristics, making it difficult to accurately model and uniformly define the gain. This nonlinearity poses a significant challenge to the stability of the closed-loop system, thus limiting the application of single-bit quantizers in high-precision closed-loop systems.
[0029] In comparison, the multi-bit quantizer used in this invention has multiple quantization steps, better linearity in the input-output mapping relationship, and higher equivalent gain. Precise modeling can be performed based on the width of the quantization step and the threshold interval. This characteristic enables multi-bit quantizers to exhibit higher linearity, lower quantization error, and more stable control performance in system feedback control.
[0030] for Capacitive microelectromechanical accelerometers using single-bit quantizers suffer from low system stability margins, significantly limiting closed-loop accelerometer range design. Replacing the quantizer with a multi-bit quantizer allows the accelerometer to achieve a more accurate quantizer equivalent gain. This improves the robustness of the system and allows for greater range design margin.
[0031] Furthermore, within the same input signal range, single-bit quantizers have limited dynamic range and are prone to overload, leading to output distortion. In contrast, multi-bit quantizers significantly reduce the quantization step size and lower the background quantization noise by increasing the number of quantization bits, thereby effectively extending the dynamic range.
[0032] Therefore, after replacing the multi-bit quantizer, Capacitive microelectromechanical accelerometers can achieve a larger range and higher signal-to-noise ratio.
[0033] However, when introducing a multi-bit quantizer into a practical system, it is usually necessary to add an additional DAC module to convert the digital code stream output by the multi-bit quantizer into an analog voltage signal. This will bring additional nonlinear errors, increased power consumption and increased complexity, thus offsetting the performance advantages brought by the multi-bit quantizer to some extent.
[0034] Figure 3 This is a schematic diagram of the multi-pair feedback electrode meter head sensitive structure of the present invention.
[0035] like Figure 3 As shown, to address the performance losses such as nonlinearity and power consumption caused by adding a DAC module when replacing a multi-bit quantizer, this paper proposes a new control architecture that preserves the equivalent gain of the multi-bit quantizer. With advantages such as ease of modeling, small quantization error, and high control precision, the interface between the meter and the sensitive structure has been optimized. A new feedback electrode pair has been added to the sensitive structure, avoiding dependence on the traditional DAC module and realizing closed-loop control of the system.
[0036] The voltage signal output by a single-bit quantizer can be directly transmitted to the feedback electrode of the meter, realizing a closed-loop electrostatic force feedback. The output signal of a multi-bit quantizer is a digital code stream, which needs to be converted into a voltage signal by a DAC module before electrostatic force feedback can be achieved. Therefore, after replacing the control architecture with a multi-bit quantizer, a DAC module needs to be added to the feedback loop to achieve closed-loop functionality. Adding a DAC module will lead to increased system power consumption, deteriorated nonlinearity, and increased complexity.
[0037] By adding a pair of feedback electrodes to the sensitive structure of the meter head, and responding one by one to the digital code stream signal generated by the multi-bit quantizer, the feedback response to the output signal of the multi-bit quantizer can be directly realized without adding a DAC module to the system.
[0038] Therefore, adding a new pair of feedback electrodes to the sensitive structure of the meter head can replace the DAC function and solve the performance loss problems such as nonlinearity and power consumption caused by replacing the multi-bit quantizer.
[0039] Theoretical basis: for Figure 2 The schematic diagram of the transmission curves and linear model of the multi-bit quantizer and single-bit quantizer of the present invention shown has the following principle formula.
[0040] When the input signal passes through the multi-bit quantizer, let the quantization interval be... , It is the full-scale voltage. The quantizer bit depth is [value], and the error of uniform quantization is [value]. The noise is uniformly distributed within the interior, therefore the noise power is: (1) For a single-bit quantizer, its noise power is: (2) For a multi-bit quantizer, its noise power is: (3) If quantization bits are taken hour: (4) The dynamic range of a quantizer is usually expressed in terms of signal-to-noise ratio. To approximate it, its expression is: (5) Equation (5) shows that as the number of bits in the quantizer increases... As the input signal increases, the dynamic range of the system grows linearly, enabling it to adapt to a wider range of input signal variations while maintaining its signal resolution capability.
[0041] for Figure 4 The schematic diagram of the electrostatic force of the feedback electrode of the meter-sensing structure of the present invention shown has the following principle formula.
[0042] When the movable mass block moves upward under the action of external acceleration, the capacitance gap between it and the upper plate of the feedback electrode decreases to The capacitance gap between the electrode and the lower electrode of the feedback electrode increases to ,in It is the static gap of the capacitor comb teeth. It is the displacement of the movable mass block.
[0043] To servo-motorize the movable mass to its equilibrium position, different feedback voltages need to be applied to the upper and lower plates of the feedback electrode. This ensures that the direction of the electrostatic force on the movable mass is opposite to the displacement, thus completing closed-loop control. The electrostatic force generated by the feedback electrode is: (6) in It is the static voltage of the feedback electrode. It is the voltage of the movable mass block. It is the feedback voltage output from the circuit to the feedback electrode. It is the number of capacitor comb teeth. Where is the dielectric constant. This represents the area of the capacitor plates facing each other.
[0044] Due to the displacement of the movable mass block Relatively small, meets Equation (6) can be simplified to: (7) As shown in equation (7), the direction of the electrostatic force is opposite to the direction of motion of the movable mass, and the magnitude of the electrostatic force is related to the feedback voltage. It is directly proportional; the proportionality coefficient is the torque coefficient. The torque coefficient for the electrostatic force generated by a pair of feedback electrodes. The expression is: (8) Combination Figure 3 It can be seen that this invention achieves its purpose by adding multiple pairs of feedback electrodes to replace the DAC function, thus solving the performance loss problems such as nonlinearity and power consumption caused by replacing the multi-bit quantizer. At this time, the total torque coefficient of the electrostatic force on the meter's sensitive structure is: (9) in It is the number of feedback electrode pairs in the meter's sensitive structure. It is the first The static voltage of the feedback electrode, It is the first The number of capacitor comb groups corresponding to the feedback electrode.
[0045] As can be seen from equation (9), after adding multiple pairs of feedback electrodes to the sensitive structure of the meter head, the torque coefficient of the accelerometer meter head can be changed by adjusting the static voltage of different feedback electrodes, thereby achieving more refined electrostatic force feedback control and a better closed-loop servo effect.
[0046] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A multi-bit microelectromechanical accelerometer, characterized in that, include: Meter head sensitive structure, CV conversion circuit, first-order Control circuit, multi-bit quantizer, torque converter coefficient module, and acceleration conversion module. The difference between the input acceleration signal and the feedback acceleration signal is input to the meter's sensitive structure; the output of the meter's sensitive structure is connected to the input of the CV conversion circuit. The output of the CV conversion circuit is connected to the feedforward input of the first-order control circuit. The output of the control circuit is connected to the input of the multi-bit quantizer; the output of the multi-bit quantizer is connected to the first-order quantizer. The feedback input terminal of the control circuit is connected to the input terminal of the torque coefficient module; the output terminal of the torque coefficient module is connected to the input terminal of the acceleration conversion module, and the acceleration conversion module outputs a feedback acceleration signal. The front end of the meter's sensitive structure has multiple pairs of feedback electrodes corresponding to multiple bits.
2. The multi-bit microelectromechanical accelerometer according to claim 1, characterized in that, The torque coefficient of the accelerometer head can be changed by adjusting the static voltage of different feedback electrodes in the sensitive structure of the meter head.
3. The multi-bit microelectromechanical accelerometer according to claim 2, characterized in that, The direction of the electrostatic force generated by the feedback electrode of the meter's sensitive structure is opposite to the direction of motion of the movable mass. The magnitude of the electrostatic force is related to the feedback voltage. It is directly proportional.
4. The multi-bit microelectromechanical accelerometer according to claim 3, characterized in that, When the mass of the movable mass block is much smaller than the static gap of the capacitor comb teeth, the electrostatic force generated by the feedback electrode pair of the meter head sensitive structure is: ,in, It is the static voltage of the feedback electrode. It is the voltage of the movable mass block. It is the feedback voltage output from the circuit to the feedback electrode. It is the number of capacitor comb teeth. Where is the dielectric constant. This represents the area of the capacitor plates facing each other.
5. The multi-bit microelectromechanical accelerometer according to claim 4, characterized in that, Torque coefficient of the feedback electrode generating electrostatic force for: ,in, It is the static gap of the capacitor comb teeth.
6. The multi-bit microelectromechanical accelerometer according to claim 5, characterized in that, The total torque coefficient of the electrostatic force on the sensitive structure of the meter head is: 。 7. The multi-bit according to claim 1 Microelectromechanical accelerometer, characterized in that, The sensitive structure of the meter head uses a differential comb capacitor.
8. The multi-bit microelectromechanical accelerometer according to claim 1, characterized in that, Equivalent gain of multi-bit quantizer It is more accurate than the equivalent gain of a single-bit quantizer.
9. The multi-bit microelectromechanical accelerometer according to claim 1, characterized in that, Equivalent gain of multi-bit quantizer The threshold interval is determined based on the width of the quantization step.