Fault diagnosis method for asynchronous motor speed sensor

Abstract

The invention provides an asynchronous motor speed sensor fault diagnosis method, which comprises the following steps of: acquiring a rotating speed signal analog quantity, analyzing the acquired rotating speed signal analog quantity, and realizing asynchronous motor speed sensor fault diagnosis according to different rotating speed signal analog quantity analysis results. Analysis of the analog quantity of the collected rotating speed signals comprises a logic sequence of level conversion, the duty ratio of signals of the same channel, the period deviation ratio of signals of different channels, edge signal time prediction of different channels and high and low level voltage values. According to the method, the fault of the speed sensor can be effectively diagnosed by comprehensively analyzing the analog quantity of the collected rotating speed signal from different angles, and the method is simple to implement, small in calculated amount and high in practicability.

Description

Technical Field

[0001] The present invention relates to the technical field of fault diagnosis, and in particular to a method for diagnosing faults of an asynchronous motor speed sensor. Background Art

[0002] Asynchronous motors are widely used in various transmission fields due to their simple structure, low price, and reliable operation. Speed ​​sensors are used to detect the running direction and speed of the motor in real time. The speed signal is fed back to the control system for speed closed-loop control to achieve high-performance control of the electric transmission system. The speed sensor usually feeds back two signals with a phase difference of 90°. The rotation direction of the motor can be judged based on this. Each sensor signal is a pulse signal with a duty cycle of 50%. As the speed increases, the frequency increases, such as Figure 1 The electromagnetic environment in which the motor works is complex. The speed sensor is usually installed at the end of the motor shaft, which is relatively fragile and has a high probability of failure. Once a failure occurs, it will lead to inaccurate or lost speed information measurement, which will affect the overall performance of the control system at the least and cause the entire control system to stop running at the worst.

[0003] In the prior art, whether the motor speed signal is faulty is usually evaluated by estimating the asynchronous motor speed. However, the estimation of the motor speed signal can be used for motor control without a speed sensor, but it cannot be used as a criterion for judging whether the speed sensor is faulty. First, the estimation accuracy of the speed signal is limited. The speed estimation only needs to meet the control requirements, and the higher the speed, the better. Second, the estimation of the speed signal requires the collection of other variables, such as the collection of the motor input current and the reconstruction of the motor input voltage, which have a great influence on the estimated speed. Once there is a problem with the estimated speed, it is difficult to determine whether it is a speed sensor problem. Third, the estimation of the speed signal requires modeling and is implemented through complex calculations, which takes up a lot of computing power of the control system.

[0004] In the prior art, another method is to achieve fault diagnosis through feature learning of typical faults of speed sensors. However, learning the features of typical faults through machine learning artificial intelligence methods requires, firstly, extracting the features of each fault, and the features must be obvious and can be diagnosed. Diagnosis has probability, so for features that are specious or have fuzzy boundaries, diagnosis cannot be achieved or there may be missed diagnosis; secondly, a large amount of data is required to learn and train the features, especially fault data, and it is difficult to obtain data samples from the database; thirdly, the diagnostic algorithm is complex and requires a large amount of computing power of the control system. Summary of the invention

[0005] According to the technical problems mentioned in the above background technology, a method for diagnosing the fault of an asynchronous motor speed sensor is provided. The present invention realizes the fault diagnosis of the speed sensor by analyzing the collected speed signal analog quantity, including: the logic sequence of level conversion, the duty cycle of the same channel signal, the cycle deviation rate of different channel signals, the edge signal time prediction of different channels, and the high and low level voltage values.

[0006] The technical means adopted by the present invention are as follows:

[0007] A method for diagnosing a fault of an asynchronous motor speed sensor comprises the following steps:

[0008] Collect the analog quantity of the speed signal, analyze the collected analog quantity of the speed signal, and realize the fault diagnosis of the asynchronous motor speed sensor according to the analysis result;

[0009] The analysis angles of the collected speed signal analog quantity include: the logical sequence of level conversion, the duty cycle of the signal in the same channel, the period deviation rate of the signal in different channels, the edge signal time prediction of different channels, and the high and low level voltage values.

[0010] Furthermore, since the speed signal collected by the speed sensor includes two channels, namely, channel A and channel B, and the phase difference between channel A and channel B is 90°, the duty cycle of the high and low levels of channel A or channel B is 50%; when analyzing the logic sequence of the level conversion of the collected speed signal analog quantity, the logic level of the current state is obtained, that is, the level state of channel A and channel B is obtained, and then the logic level of the next state is predicted; if the logic level of the next state is an unpredicted state, it is a state error, which indicates that the speed sensor is faulty.

[0011] Furthermore, when analyzing the duty cycle of the same channel signal of the collected speed signal analog quantity, if the high-level duty cycle is greater than the predetermined allowable deviation, it indicates that the speed sensor is faulty. The signal duty cycle diagnosis formula of the speed sensor A and B is:

[0012]

[0013] Among them, x represents the speed signal analog quantity A or B, δ xt Indicates the degree of imbalance, δ t,MAX Indicates the maximum imbalance; δ t,MAX Determined by the maximum acceleration of the electric drive system.

[0014] Furthermore, when analyzing the signal period deviation rates of different channels of the collected speed signal analog quantity, the sensor open circuit fault diagnosis is realized by calculating the signal period deviation rates of the speed sensor A channel and B channel;

[0015] The period of the A and B signals is calculated as:

[0016]

[0017] The period deviation rate of the A-channel and B-channel signals is greater than the maximum allowable deviation δ p，MAX , it means that a circuit breaker fault occurs, and the diagnostic formula is:

[0018]

[0019] Among them, δ p Denotes the degree of deviation, δ p，MAX Indicates the maximum deviation, t A represents the cycle of path A, t B Indicates the B-path cycle.

[0020] Furthermore, since the signals of the speed sensor A and B channels change periodically, when the edge signal time prediction of different channels of the collected speed signal analog quantity is analyzed, the maximum change time of adjacent cycles is determined by the maximum acceleration of the electric transmission system;

[0021] That is, if the time when the next edge of path A and path B appears is within the predicted range, the speed sensor works normally; if it exceeds or is less than the predicted range, the speed sensor is diagnosed to be faulty;

[0022] The signal edge diagnosis formula of speed sensor A and B is:

[0023]

[0024] Among them, t A(n+1)MIN Indicates the minimum time for n+1 edges of signal A to appear; Indicates the maximum time for n+1 edges of signal A to appear; t B(n+1)MIN Indicates the minimum time for n+1 edges of the B-channel signal to appear; Indicates the maximum time for n+1 edges of signal B to appear; t An Indicates the nth cycle time of the A-channel signal; t Bn Indicates the nth cycle time of the B-channel signal; Δt indicates the maximum difference allowed between the n and n+1 cycles.

[0025] Furthermore, since the speed sensor is usually powered by the control system, the power supply voltage is +15V, the high level of the speed sensor A and B signals collected by the control system is usually 15V, and the low level is oV. When the high and low level voltage values ​​of the speed signal of the collected speed signal analog quantity are analyzed, the speed sensor fault is diagnosed by judging whether it is within the limited range;

[0026] The speed sensor A and B signal level voltage diagnosis formula is:

[0027] U Hmin ≤U H -15≤U Hmax , U Lmin ≤U L ≤U Lmax ;

[0028] Among them, ΔU H =U Hmax -U Hmin , ΔU L =U Lmax -U Lmin ; UH represents the high level voltage of the speed sensor A and B signals, U L Indicates the low level voltage of the speed sensor A and B signals, U Hmax Indicates U H Maximum allowed voltage, U Hmin Indicates U H The minimum allowable voltage, U Lmax Indicates U L Maximum allowed voltage, U Lmin Indicates U L The lowest voltage allowed.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] The present invention can effectively diagnose the fault of the speed sensor by comprehensively analyzing the collected analog quantity of the speed signal, including the logic sequence of level conversion, the duty cycle of the signal in the same channel, the period ratio of the signal in different channels, the prediction of the edge signals in different channels and the high and low level voltage values ​​of the speed signal. The implementation is simple, the calculation amount is small and the practicability is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 It is the speed sensor speed signal.

[0033] Figure 2a This is a schematic diagram of the speed sensor signal A leading B according to the present invention.

[0034] Figure 2b This is a schematic diagram of the speed sensor signal B leading A in the present invention.

[0035] Figure 3It is a schematic diagram of the logic change state machine of the A and B paths of the speed sensor of the present invention.

[0036] Figure 4 It is a schematic diagram of the signal waveforms of the A and B paths of the speed sensor of the present invention.

[0037] Figure 5 It is a schematic diagram of the signal waveforms of the A and B paths of the speed sensor of the present invention.

[0038] Figure 6 It is a schematic diagram of the edge diagnosis of the A and B signal of the speed sensor of the present invention.

[0039] Figure 7 It is a schematic diagram of the voltage diagnosis waveform of the signal level of the A and B paths of the speed sensor of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0041] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0042] like Figure 1-7 As shown, the present invention provides a method for diagnosing a fault of an asynchronous motor speed sensor, comprising the following steps:

[0043] Collect the analog quantity of the speed signal, analyze the collected analog quantity of the speed signal, and realize the fault diagnosis of the asynchronous motor speed sensor according to the analysis result;

[0044] The analysis angles of the collected speed signal analog quantity include: the logical sequence of level conversion, the duty cycle of the signal in the same channel, the period deviation rate of the signal in different channels, the edge signal time prediction of different channels, and the high and low level voltage values.

[0045] As a preferred implementation, since the speed signal collected by the speed sensor usually includes two channels A and B, the difference between A and B is 90°, and the duty cycle of the high and low levels of A or B is 50%, therefore, when analyzing the logic sequence of the level conversion of the collected speed signal analog quantity, the changes of the high and low levels of A and B must conform to certain rules, such as Figure 2a A is ahead of B. Figure 2b B is ahead of A. It can be understood that the present application obtains the logic level of the current state, that is, obtains the level state of A and B, and then predicts the logic level of the next state; if the logic level of the next state is a non-predicted state, it is a state error, which means that the speed sensor is faulty.

[0046] according to Figure 2a and Figure 2b The starting state can be in any state, according to the current state of A and B and the logic level of the next state. For example, the current state is S0o, which means A is low and B is low. Figure 3 , the next state may be Soo or S01 or S10; if the next state is S11, it is an error; the control system can be reset at any time and return to the starting state after reset. Therefore, the above changes can be represented by the state machine as, once entering the 'ERRoR' state, it means that the speed sensor is faulty.

[0047] As a preferred implementation, when analyzing the duty cycle of the same channel signal of the collected speed signal analog quantity, the signal waveforms of the speed sensor A and B channels are shown in FIG. Figure 4 , the high and low level duty ratio of A and B is 50%. Once the deviation is exceeded (if the high level duty ratio is greater than the predetermined allowable deviation), it indicates that the speed sensor or detection circuit is faulty. The speed sensor A and B signal duty ratio diagnosis formula is shown in the following formula:

[0048]

[0049] Among them, x represents the speed signal analog quantity A or B, δ xt Indicates the degree of imbalance, δ t,MAX Indicates the maximum imbalance; δ t,MAX It is determined by the maximum acceleration of the electric drive system, and can also be given directly according to the needs of engineering applications.

[0050] As a preferred implementation, when analyzing the periodic deviation rate of the signals of different channels of the collected speed signal analog quantity, the diagnosis of the sensor circuit breaker fault is realized by calculating the periodic deviation rate of the signals of the speed sensor A and B. The waveforms of the signals of the speed sensor A and B are as follows: Figure 5 As shown:

[0051] The calculation formula for the period of A and B signals is as follows:

[0052]

[0053]

[0054] The period deviation rate of the A-channel and B-channel signals must be within a certain range (less than or equal to the maximum allowable deviation δ p,MAX ), once it exceeds the range, it means a circuit breaker fault occurs. The diagnostic formula is shown below.

[0055]

[0056] Among them, δ p Denotes the degree of deviation, δ p,MAX Indicates the maximum deviation, t A represents the cycle of path A, t B Indicates the B-path cycle.

[0057] As a preferred implementation, since the speed sensor A and B signals change periodically, when the edge signal time prediction of different channels of the collected speed signal analog quantity is analyzed, the maximum change time of adjacent cycles is determined by the maximum acceleration of the electric drive system. Therefore, at the current edge, the next edge can be predicted. If it is within the prediction range, the speed sensor works normally. If it exceeds or is less than the prediction range, it can be diagnosed that the speed sensor is faulty. The edge diagnosis waveform of the speed sensor A and B signals is shown in FIG. Figure 6 The signal edge diagnosis formulas for speed sensor A and B are as follows:

[0058] t AMIN =t B (1-Δt), t BMIN =t A (1-Δt);

[0059] t AMAX =t B (1+Δt), t BMAX =t A (1+Δt);

[0060] Among them, t A(n+1)MIN Indicates the minimum time for n+1 edges of signal A to appear; Indicates the maximum time for n+1 edges of signal A to appear; t B(n+1)MIN Indicates the minimum time for n+1 edges of the B-channel signal to appear; Indicates the maximum time for n+1 edges of signal B to appear; t An Indicates the nth cycle time of the A-channel signal; t BnIndicates the nth cycle time of the B-channel signal; Δt indicates the maximum change cycle.

[0061] The speed sensor is usually powered by the control system, and the power supply voltage is +15V. The high level of the speed sensor A and B signals collected by the control system is usually 15V, and the low level is 0V. When analyzing the high and low level voltage values ​​of the speed signal analog quantity collected, the high and low levels of the A and B signals can be collected to determine whether they are within the specified range, such as Figure 7 As shown, determine whether the sensor power supply is faulty or whether the A and B signals are poorly connected.

[0062] The speed sensor A and B signal level voltage diagnosis formula is as follows:

[0063] |U H -15|≤ΔU H ,|U L |≤ΔU H

[0064] Among them, ΔU H =U Hmax -U Hmin , ΔU L =U Lmax -U Lmin UH represents the high level voltage of the speed sensor A and B signals, U L Indicates the low level voltage of the speed sensor A and B signals, U Hmax Indicates U H Maximum allowed voltage, U Hmin Indicates U H The minimum allowable voltage, U Lmax Indicates U L Maximum allowed voltage, U Lmin Indicates U L The lowest voltage allowed.

[0065] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0066] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0067] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0068] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0069] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0070] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for diagnosing a fault of an asynchronous motor speed sensor, characterized in that: The following steps are involved: Collect the analog quantity of the speed signal, analyze the collected analog quantity of the speed signal, and realize the fault diagnosis of the asynchronous motor speed sensor according to the analysis result; The analysis angles of the collected speed signal analog quantity include: the logical sequence of level conversion, the duty cycle of the signal in the same channel, the period deviation rate of the signal in different channels, the edge signal time prediction of different channels, and the high and low level voltage values.

2. The method for diagnosing a fault of an asynchronous motor speed sensor according to claim 1, characterized in that: Since the speed signal collected by the speed sensor includes two channels, namely, channel A and channel B, and the phase difference between channel A and channel B is 90°, the duty cycle of the high and low levels of channel A or channel B is 50%; when analyzing the logic sequence of the level conversion of the collected speed signal analog quantity, by obtaining the logic level of the current state, that is, obtaining the level state of channel A and channel B, the logic level of the next state is predicted; If the logic level of the next state is an unexpected state, it is a state error, which means that the speed sensor is faulty.

3. The method for diagnosing a fault of an asynchronous motor speed sensor according to claim 1, characterized in that: When analyzing the duty cycle of the same channel signal of the collected speed signal analog quantity, if the high-level duty cycle is greater than the predetermined allowable deviation, it indicates that the speed sensor is faulty. The signal duty cycle diagnosis formula of speed sensor A and B is: Among them, x represents the speed signal analog quantity A or B, δ xt Indicates the degree of imbalance, δ t,MAX Indicates the maximum imbalance; δ t,MAX Determined by the maximum acceleration of the electric drive system.

4. The method for diagnosing a fault of an asynchronous motor speed sensor according to claim 1, characterized in that: When analyzing the signal period deviation rates of different channels of the collected speed signal analog quantity, the sensor open circuit fault diagnosis is realized by calculating the signal period deviation rates of the speed sensor A and B channels; The period of the A and B signals is calculated as: The period deviation rate of the A-channel and B-channel signals is greater than the maximum allowable deviation δ p,MAX , it means that a circuit breaker fault occurs, and the diagnostic formula is: Among them, δ p Denotes the degree of deviation, δ p,MAX Indicates the maximum deviation, t A represents the cycle of path A, t B Indicates the B-path cycle.

5. The method for diagnosing a fault of an asynchronous motor speed sensor according to claim 1, characterized in that: Since the signals of the speed sensor A and B channels change periodically, when analyzing the edge signal time prediction of different channels of the collected speed signal analog quantity, the maximum change time of adjacent cycles is determined by the maximum acceleration of the electric drive system; That is, if the time when the next edge of path A and path B appears is within the predicted range, the speed sensor works normally; if it exceeds or is less than the predicted range, the speed sensor is diagnosed to be faulty; The signal edge diagnosis formula of speed sensor A and B is: Among them, t A(n+1)MIN Indicates the minimum time for n+1 edges of signal A to appear; Indicates the maximum time for n+1 edges of signal A to appear; t B(n+1)MIN Indicates the minimum time for n+1 edges of the B-channel signal to appear; Indicates the maximum time for n+1 edges of signal B to appear; t An Indicates the nth cycle time of the A-channel signal; t Bn Indicates the nth cycle time of the B-channel signal; Δt indicates the maximum difference allowed between the n and n+1 cycles.

6. The method for diagnosing a fault of an asynchronous motor speed sensor according to claim 1, characterized in that: Since the speed sensor is usually powered by the control system with a power supply voltage of +15V, the high level of the speed sensor A and B signals collected by the control system is usually 15V, and the low level is 0V. When analyzing the high and low level voltage values ​​of the speed signal analog quantity collected, the speed sensor fault is diagnosed by judging whether it is within the limited range; The speed sensor A and B signal level voltage diagnosis formula is: IN Hmin ≤U H -15≤U Hmax ,IN Lmin ≤U L ≤U Lmax ; Among them, ΔU H =U Hmax -U Hmin , ΔU L =U Lmax -U Lmin ; UH represents the high level voltage of the speed sensor A and B signals, U L Indicates the low level voltage of the speed sensor A and B signals, U Hmax Indicates U H Maximum allowed voltage, U Hmin Indicates U H The minimum allowable voltage, U Lmax Indicates U L Maximum allowed voltage, U Lmin Indicates U L The lowest voltage allowed.

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