Encoder system of integrated MEMS vibration sensor for motor monitoring

Abstract

The invention provides an encoder system of an integrated MEMS vibration sensor for motor monitoring. The MEMS vibration sensor is characterized by comprising an encoder module (1), an MEMS vibration sensing module (2) (which can comprise a triaxial accelerometer (21) and an acoustic sensor (22)), a signal processing unit (3), a compensation module (4), an output interface (5) and a Z signal compensation module (6). Through deep coupling of vibration sensing and signal compensation, the position detection precision is improved from the source, the fault diagnosis and predictive maintenance functions are achieved, and the method can be widely applied to a high-precision servo control system.

Description

(I) Technical Field

[0001] This invention relates to an encoder system with an integrated MEMS vibration sensor for motor monitoring, belonging to the field of motor control and condition monitoring technology, and in particular to an encoder system with an integrated MEMS vibration sensor for motor monitoring. (II) Background Technology

[0002] Encoders are key components in servo systems used to detect motor position and speed. In actual operation, vibrations caused by factors such as load changes and mechanical wear can interfere with the normal output of the encoder, leading to position detection errors and affecting the system's control accuracy and stability.

[0003] In January 2025, Zhang Penghao et al. from the Beijing Great Wall Institute of Metrology and Testing Technology of China Aviation Industry Corporation disclosed a miniaturized triaxial high-temperature resistant fiber optic MEMS vibration sensor (patent number: CN202411629858.4), without mentioning an encoder module with compensation and correction functions; in March 2025, Wang Zuosong et al. from Yunnan Electric Power Research Institute (Group) Co., Ltd. provided an improved method for improving the frequency accuracy of electromagnetic MEMS vibration sensors (patent number: CN202411829418.3), the design structure of which also places the implementation of the method in the computer part, still belonging to a separate system.

[0004] As the current research shows, in existing technologies, vibration monitoring and position detection are mostly separate systems, resulting in complex data fusion and making it difficult to achieve real-time compensation for vibration-induced encoder signal effects. Furthermore, the mechanisms by which vibration affects the signal formats output by different encoders (sine / cosine analog signals or digital square wave signals) differ, and existing solutions lack targeted, differentiated compensation strategies. For example, the impact of vibration on sine / cosine signals mainly manifests in the quality of analog quantities, such as amplitude and phase; while its impact on digital square wave signals manifests in digital timing, such as edge jitter. Therefore, there is an urgent need for an integrated intelligent encoder system capable of deeply sensing vibration and performing precise compensation for different signal formats.

[0005] This invention discloses an encoder system with an integrated MEMS vibration sensor for motor monitoring. The MEMS vibration sensing module detects vibration signals during motor operation in real time. The signal processing unit performs spectral analysis on the vibration signals to diagnose the motor status, including rotor imbalance, bearing wear, and gear faults. The compensation module performs differentiated compensation based on the diagnostic results and the signal form output by the encoder module. The Z-signal compensation module handles the impact of vibration on the Z-phase index signal. This is an integrated intelligent encoder system that improves position detection accuracy from the source through deep coupling of vibration sensing and signal compensation, and has fault diagnosis and predictive maintenance functions. (III) Summary of the Invention

[0006] The purpose of this invention is to provide an encoder system with an integrated MEMS vibration sensor for motor monitoring: an encoder system with high integration that can perform intelligent vibration diagnosis and differential signal compensation, overcoming the shortcomings of the prior art.

[0007] The objective of this invention is achieved as follows:

[0008] The encoder system for motor monitoring using an integrated MEMS vibration sensor consists of an encoder module (1), a MEMS vibration sensing module (2) (which may include a triaxial accelerometer (21) and an acoustic sensor (22)), a signal processing unit (3), a compensation module (4), an output interface (5), and a Z-signal compensation module (6). In this system, the MEMS vibration sensing module (2) is fixed inside the motor housing or the encoder and is used to detect vibration signals during motor operation in real time. The signal processing unit (3) connects the encoder module (1) and the MEMS vibration sensing module (2). The compensation module (4) performs differential compensation based on the diagnostic results and the form of the AB signal output by the encoder module (1) – sine / cosine analog signal or digital square wave signal: it compensates for the amplitude fluctuation, orthogonality deviation and DC bias of the sine / cosine signal, and compensates for the edge jitter and duty cycle distortion of the digital square wave signal; then it outputs the compensated ABZ signal and vibration status data through the output interface (5), and the Z signal compensation module (6) processes the influence of vibration on the Z phase index signal.

[0009] The core of the system is: 1. Deep state perception: The system comprehensively collects motor vibration data through the MEMS vibration sensing module (2) (which may include a triaxial accelerometer (21) and an acoustic sensor (22)); 2. Intelligent fault diagnosis: The signal processing unit (3) accurately associates vibration characteristics with specific mechanical faults (such as rotor imbalance and bearing wear) through spectrum analysis and maps them to the specific error modes of the AB signal; 3. Differentiated and precise compensation: The compensation module (4) executes completely different compensation strategies according to the output signal form of the encoder module (1). For sine and cosine signals, it strives to restore the quality of their analog waveforms; for digital square wave signals, it strives to ensure the accuracy of their digital timing; 4. Multifunctional output: The system outputs high-precision position information and rich state monitoring data simultaneously through a multi-protocol interface (5).

[0010] The beneficial effects of this invention are: by deeply coupling vibration sensing and signal compensation, the output quality of the encoder under complex working conditions is fundamentally improved, while early fault diagnosis and predictive maintenance of the equipment are realized, significantly enhancing the performance, reliability and intelligence level of the entire motion control system. (iv) Description of the attached drawings

[0011] Figure 1 This is a schematic diagram of the overall structure of the encoder system for motor monitoring using an integrated MEMS vibration sensor. It consists of an encoder module (1), a MEMS vibration sensing module (2) (which may include a triaxial accelerometer (21) and an acoustic sensor (22)), a signal processing unit (3), a compensation module (4), an output interface (5), and a Z-signal compensation module (6).

[0012] Figure 2 This is a detailed flowchart of the signal processing and differential compensation algorithms in the system.

[0013] Figure 3 This is a schematic diagram illustrating the effect of vibration on sine and cosine analog signals and the compensation effect.

[0014] Figure 4 This is a schematic diagram illustrating the effect of vibration on digital square wave signals and the compensation effect.

[0015] Figure 5 This is a correlation diagram between fault diagnosis based on vibration spectrum and AB signal error mode.

[0016] Figure 6 This is a schematic diagram of an embodiment of the system installation in a servo motor. (V) Detailed Implementation

[0017] The present invention will be further illustrated below with reference to specific embodiments.

[0018] like Figure 1 As shown, this system mainly includes an encoder module (1), a MEMS vibration sensing module (2), a signal processing unit (3), a compensation module (4), an output interface (5), and a Z-signal compensation module (6). The encoder module (1) can be photoelectric or magnetoelectric, and outputs sine, cosine, or square wave signals. The MEMS vibration sensing module (2) preferably integrates an ADXL355 triaxial accelerometer (21) and a MEMS acoustic sensor (22), which are soldered together on the encoder PCB.

[0019] like Figure 2 The algorithm flowchart is shown. After the system is powered on, vibration data and the original ABZ signal are acquired in parallel. The signal processing unit (3) performs FFT analysis on the vibration data and, according to... Figure 5The correlations shown are used for fault diagnosis. For example, if a vibration peak is found at the frequency through which the bearing outer ring passes, it is diagnosed as a bearing defect, and random spikes are expected in the AB signal.

[0020] After defect diagnosis, the compensation module (4) performs differentiated compensation according to the output mode of the encoder (1): sine and cosine signal paths: such as Figure 3 As shown, if rotor imbalance is diagnosed as causing amplitude fluctuations, dynamic gain compensation is activated to adjust the PGA gain in real time and output stable sine and cosine waveforms; digital square wave path: as shown Figure 4 As shown, if gear wear is diagnosed as causing edge jitter, the digital phase-locked loop is started to re-time the original jitter square wave and output a pulse with clear edges and accurate timing. In addition, the Z signal compensation submodule (6) will stabilize the index pulse.

[0021] like Figure 6 As shown, this system is installed on the spindle motor of a CNC machine tool. When the spindle is running in the high-speed zone, the acoustic sensor (22) detects a high-frequency acoustic emission signal, which is diagnosed as insufficient early lubrication of the bearing. At the same time, the sine and cosine encoder signals show slight noise. The system compensates for the signal through a filtering algorithm on the one hand, and sends a bearing lubrication warning to the host computer through the output interface (5) on the other hand, thereby completing maintenance before the fault expands and avoiding unplanned downtime. Finally, the compensated and accurate ABZ signal and vibration health status information are output to the motor controller through the multi-protocol interface (5) to realize closed-loop control and status monitoring.

Claims

1. An encoder system with an integrated MEMS vibration sensor for motor monitoring. Its features are: It consists of an encoder module (1), a MEMS vibration sensing module (2), a signal processing unit (3), a compensation module (4), an output interface (5), and a Z-signal compensation module (6). In this system, the MEMS vibration sensing module (2) is fixed inside the motor housing or encoder and is used to detect the vibration signal during motor operation in real time. The signal processing unit (3) connects the encoder module (1) and the MEMS vibration sensing module (2) (which may include a triaxial accelerometer (21) and an acoustic sensor (22)) and is used to perform spectral analysis on the vibration signal. The analysis is used to diagnose the motor condition, including rotor imbalance, bearing wear and gear failure; the compensation module (4) performs differential compensation based on the diagnostic results and the AB signal form output by the encoder module (1) - sine and cosine analog signal or digital square wave signal: it compensates for the amplitude fluctuation, orthogonality deviation and DC bias of the sine and cosine signal, and compensates for the edge jitter and duty cycle distortion of the digital square wave signal; then it outputs the compensated ABZ signal and vibration status data through the output interface (5), and the Z signal compensation module (6) processes the influence of vibration on the Z phase index signal.

2. The system according to claim 1, characterized in that: When the encoder module (1) outputs a sine and cosine analog AB signal, the compensation module (4) performs the following compensation measures: dynamic gain compensation or digital amplitude normalization for amplitude fluctuations caused by vibration; digital domain orthogonal reconstruction or hardware phase shift correction for orthogonality deviations caused by vibration; and dynamic bias correction for DC bias drift caused by vibration or impact.

3. The system according to claim 1, characterized in that: When the encoder module (1) outputs a digital square wave AB signal, the compensation module (4) performs the following compensation measures: for edge jitter caused by vibration, a digital phase-locked loop is used for retiming to smooth the edge; for duty cycle distortion caused by vibration, dynamic threshold compensation or digital pulse width shaping is performed.

4. The system according to claim 1, characterized in that: The signal processing unit (3) analyzes the spectral characteristics of the vibration signal and associates specific physical faults with specific error patterns of the AB signal. The correlations include: rotor imbalance corresponds to periodic amplitude fluctuations or duty cycle oscillations of the AB signal; gear wear or misalignment corresponds to high-frequency distortion and severe edge jitter of the AB signal; and bearing defects correspond to random glitch and broadband noise of the AB signal.

5. The system according to claim 1, characterized in that: The compensation module (4) includes a configurable signal processing path that can automatically switch or merge between a compensation algorithm for sine and cosine analog signals and a compensation algorithm for digital square wave signals, depending on the output signal form of the encoder module (1).

6. The system according to claim 1, characterized in that: The MEMS vibration sensing module (2) includes a triaxial accelerometer (21) and an acoustic vibration sensor (22); the triaxial accelerometer (21) is used to detect low- to mid-frequency mechanical vibrations, and the acoustic vibration sensor (22) is used to detect high-frequency acoustic emission signals generated by early bearing defects or slight friction.

7. The system according to claim 1, characterized in that: The system also includes a Z signal compensation submodule (6) specifically for handling the influence of vibration on the Z phase index signal; the submodule (6) calibrates the generation time of the Z pulse or stabilizes the pulse width through a prediction algorithm or a hysteresis confirmation method.

8. The system according to claim 1, characterized in that: The output interface (5) is a multi-protocol compatible interface, which can output compensated sine and cosine analog AB signals, compensated digital square wave ABZ signals, or encoded absolute position digital messages according to the configuration; at the same time, the interface (5) will also output vibration characteristic values ​​and system health status information as extended data channels.

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