A back electromotive force detection and processing method and its acquisition wiring circuit

Abstract

The present invention is applicable to the field of power electronics technology and provides a method for detecting and processing back electromotive force, including the following steps: First, an observer is used to judge the forward and reverse rotation states of the motor at medium and high speeds; one of the three-phase outputs is selected and connected to a low-voltage voltage division circuit; a voltage division resistor collects the voltage value of this phase to restore the back electromotive force of the motor; the micro-control unit receives an external start signal and enters the forward and reverse wind states to judge the current state of the motor; if it is judged that the motor is stationary, the micro-control unit enters the lower bridge arm braking state and outputs a fixed duty cycle to short-circuit the three phases; when the duty cycle is at a low level, the back electromotive force voltage value is collected, and it is judged whether the motor is truly stationary through the voltage value; the back electromotive force signal is processed by using the sampling integration method, the collected back electromotive force voltage values are accumulated and then divided by a certain value; it is not limited by the number of chip pins, has strong versatility, can well avoid the signal interference problem in the acquisition process, speeds up the judgment of the current state of the motor, has a fast response, and improves the user experience.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and particularly relates to a method for detecting and processing back electromotive force and its acquisition wiring circuit. Background Art

[0002] In products such as ceiling fans and blowers, during operation, the fan blades will rotate as the motor starts. In such products, during the process of the motor driving the fan blades to rotate at high speed, after the controller receives a stop signal, it shuts down the output, and the motor gradually decelerates from the high-speed operation state to a stop. The fan blades on the motor will continue to rotate for a short period of time under the action of inertia. If the controller receives an instruction to continue running or reverse, it is necessary to re-judge the motor state for different processing.

[0003] In order to meet the detection and identification of the working position and speed of a three-phase motor, generally a single-resistor or multi-resistor method is commonly used in the market for detection. Among them, the circuit configuration required for the method of using a single-resistor circuit board to detect the motor position is the simplest, and thus the most cost-effective. Currently, for the method of judging whether a motor is stationary on a single-resistor circuit board in the market, there are two common detection methods. One is to use a three-phase back electromotive force detection circuit to detect whether the motor is currently in a stationary state, forward rotation, or reverse rotation. The second is to use the observer itself for estimation. The common methods have the following problems:

[0004] 1. Three-way back electromotive force detection: This method for judging stationarity has a rigid requirement for the number of chip pins. At least three ADC pins are required. In many cases, the chip pins are insufficient, so this method has great limitations and poor versatility. At the same time, when the motor is running at a low speed, affected by the accuracy of the ADC itself, the value of the ADC is very small, making it difficult to perform accurate detection, with low accuracy, and some special algorithm processing is required.

[0005] 2. Using the observer itself for estimation: Since the accuracy of the observer's low-speed estimation is poor and it cannot observe very low-speed situations, the reliability cannot be guaranteed. When simply sampling the observer for processing, only a fixed time can be used to wait for shutdown and then start. There may be a situation where the motor takes too long to start after being stationary, or it takes a long time to start after receiving a start instruction, which is unstable, time-consuming, and has a poor experience.

[0006] At the same time, during the process of collecting the back electromotive force voltage value by the ADC acquisition circuit, there may be clutter interference in the circuit or environment. Under normal circumstances, the back electromotive force voltage value collected by the ADC acquisition circuit as time progresses can be drawn into a regular and smooth curve, which has a stable fluctuation, and its peak and trough values ​​are fixed or constant within a certain numerical range. When clutter interference occurs, the current level is too large due to the clutter interference, so a sudden rise and fall will appear at the curve, forming a sharp waveform, which is the glitch voltage. If the ADC acquisition circuit happens to take a value at the glitch voltage, the voltage value at this point will be judged as the motor is not in a static state, resulting in a misjudgment. In the prior art, the voltage value at a certain moment is generally taken by the ADC acquisition circuit, so clutter interference will seriously interfere with the circuit board's judgment of the working state of the motor.

[0007] Therefore, the prior art has defects. Summary of the invention

[0008] The purpose of the present invention is to overcome the shortcomings of poor versatility and bad user experience in the above-mentioned prior art, and to provide a back-electromotive force detection and processing method and its acquisition wiring circuit, which are not limited by the number of chip pins, have strong versatility, and can well avoid the signal interference problem in the acquisition process, speed up the judgment of the current state of the motor, respond quickly, and improve the user experience.

[0009] The present invention is implemented as follows: a back electromotive force detection and processing method comprises the following steps:

[0010] S01, first use the observer to determine the forward and reverse rotation state of the motor at medium and high speed;

[0011] S02, select one phase of the three-phase output and connect it to the low voltage divider circuit;

[0012] S03, collecting the voltage value of the phase through the voltage-dividing resistor to restore the back electromotive force of the motor;

[0013] S04, the micro control unit receives a start signal sent from the outside, enters the forward and reverse state judgment, and judges the current state of the motor;

[0014] S05, if it is determined that the motor is stationary, the microcontroller unit enters the lower bridge arm braking state and outputs a fixed duty cycle to short-circuit the three phases;

[0015] S06, when the duty cycle is at a low level, the back electromotive force voltage value is collected through the ADC module, and the collected back electromotive force voltage value is fed back to the micro control unit;

[0016] S07. Process the back electromotive force signal using the sampling integration method. Accumulate the acquired back electromotive force voltage values within a certain period of time, and then divide by a certain value to obtain the average back electromotive force voltage value, so as to determine whether the motor is stationary.

[0017] Furthermore, the sampling integration method includes the following steps:

[0018] S071. Set an integration time window;

[0019] S072. Accumulate the acquired back electromotive force voltage values within the integration time window;

[0020] S073. Divide the accumulated result by the set dividend threshold to obtain the average back electromotive force voltage value;

[0021] S074. Determine whether the motor is stationary according to the magnitude of the average back electromotive force voltage value.

[0022] Furthermore, the step of determining whether the motor is stationary includes: setting a judgment threshold. When the average back electromotive force voltage value is less than or equal to the judgment threshold, it is determined that the motor is in a stationary state and the motor starts; otherwise, it will re-enter step S05 for judgment.

[0023] Furthermore, the dividend threshold takes a definite value or a range value from the numerical range of the length of the integration time window.

[0024] Furthermore, the value range of the dividend threshold within the integration time window is: select a definite value within the length of the integration time window, and respectively select several values within ±0.3 s of this definite value as the dividend threshold for calculation, and then select a suitable value from the obtained values for calculation to obtain the average back electromotive force voltage value.

[0025] The present invention also discloses a back electromotive force acquisition wiring circuit for implementing the above-mentioned back electromotive force detection and processing method, including:

[0026] A microcontroller unit for executing the judgment and control steps in the above-mentioned back electromotive force detection and processing method;

[0027] An ADC module for acquiring the back electromotive force signal;

[0028] An integration module for implementing the above-mentioned sampling integration processing method;

[0029] The microcontroller unit is respectively connected and communicates with the ADC module and the integration module.

[0030] Furthermore, the integration module includes:

[0031] An accumulator for accumulating the acquired back electromotive force voltage values;

[0032] A divider for dividing the accumulated result by a set dividend threshold.

[0033] A method for detecting and processing back electromotive force provided by the present invention processes the back electromotive force signal through a single-channel sampling integration method, without being limited by the number of chip pins, applicable to most chips, with strong versatility. Moreover, the sampling integration method can well avoid signal interference problems during the acquisition process, quickly judge the current state of the motor, with fast response. When actually using the product, it can avoid the phenomenon that the motor starts after a too long static time, improving the user experience effect.

[0034] Adopting the present method for detecting and processing back electromotive force has the following advantages:

[0035] 1. Improve the motor control accuracy: The present back electromotive force detection technology allows the system to monitor the state of the motor in real time during the operation of the motor, including key parameters such as position and speed.

[0036] 2. Enhance the robustness of the system: The back electromotive force detection and processing method enhances the resistance of the motor control system to external interference and internal faults by identifying and eliminating abnormal signals.

[0037] 3. Achieve sensorless control: By adopting the back electromotive force detection and processing method, it is possible to accurately monitor and control the state of the motor without relying on external sensors. This method reduces the system cost and complexity, while improving the system reliability.

[0038] 4. Optimize the motor starting and control efficiency: The back electromotive force detection technology can adjust the control strategy in real time during the starting and operation of the motor to optimize the control efficiency of the motor.

[0039] 5. Improve the intelligence level of the motor system: The back electromotive force detection technology combined with modern intelligent algorithms can improve the intelligence level of the motor system.

[0040] 6. Reduce the system cost: Since the back electromotive force detection technology can reduce the dependence on external sensors, the hardware cost is reduced. At the same time, by optimizing the control strategy and reducing unnecessary hardware, the system cost can be further reduced.

[0041] 7. Improve the flexibility of motor control: The back electromotive force detection technology can adapt to different motor types and operating conditions, providing flexible control options.

[0042] 8. Enhance the self-diagnosis ability of the motor system: By continuously monitoring the change of the back electromotive force voltage value, the system can self-diagnose the state of the motor and timely discover and handle potential problems. Description of the Drawings

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0044] The following accompanying drawings are only intended to illustrate and explain the present invention schematically, and do not limit the scope of the present invention.

[0045] Figure 1 It is a flowchart of the steps of a back electromotive force detection and processing method provided by the present invention.

[0046] Figure 2 It is a framework schematic diagram of a back electromotive force acquisition wiring circuit provided by the present invention.

[0047] Figure 3 It is a wiring diagram of a back electromotive force acquisition wiring circuit provided by the present invention. Specific Embodiments

[0048] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further details the present invention in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0049] Please refer to Figures 1 - 3 , a back electromotive force detection and processing method disclosed in the invention, which is specifically implemented by using a back electromotive force acquisition wiring circuit. The circuit includes: a micro control unit, an ADC module, and an integration module. Both the ADC module and the integration module are connected to the micro control unit. The integration module includes: an accumulator and a divider. When the ADC module continuously acquires the back electromotive force voltage value within a set time and feeds the acquired data back to the micro control unit, after the micro control unit receives the back electromotive force voltage value detected by the ADC module, it sends the back electromotive force voltage value to the integration module. The integration module sets an integration time window in the accumulator, accumulates the back electromotive force voltage values acquired within the integration time window, and divides the accumulated back electromotive force voltage value by a set dividend threshold through the divider to calculate a suitable average value, thereby judging the current state of the motor.

[0050] And the back electromotive force detection and processing method includes the following steps:

[0051] S01. First, use an observer to determine the forward and reverse rotation states of the motor when it is running at medium and high speeds. When the motor speed is relatively low or even close to stationary, the observer cannot determine whether the current motor is in a very low-speed state (1 - 3 rpm / min) or completely stationary. Therefore, select one path for back electromotive force detection instead of three paths to quickly determine whether the motor is currently stationary. By using an observer to judge the forward and reverse rotation states of the motor, there is no need to add extra chip pins to detect and identify the forward and reverse rotation states of the motor.

[0052] The specific method for the observer to judge the forward and reverse rotation of the motor when it is running at medium and high speeds is as follows: Adopt a phase-locked loop (PLL) estimation algorithm to quickly follow the state of the motor. By setting the given current to 0, estimate the current motor speed without bringing a braking effect to the motor. Because the PLL estimation has a good following effect, if the motor is rotating, the speed and direction of the motor can be judged within one or two electrical cycles, greatly avoiding the situation of rising bus voltage.

[0053] S02. Select one of the three-phase outputs and connect it to a low-voltage divider circuit.

[0054] S03. Collect the voltage value of this phase through a voltage-dividing resistor to restore the back electromotive force of the motor.

[0055] S04. The microcontroller unit receives the start signal sent externally, enters the forward and reverse rotation state judgment, and judges the current state of the motor.

[0056] S05. If it is judged that the motor is stationary, the microcontroller unit enters the lower-bridge arm braking state and outputs a fixed duty cycle to short-circuit the three phases.

[0057] S06. When the duty cycle is at a low level, the back electromotive force voltage value is collected through the ADC module, and the collected back electromotive force voltage value is fed back to the microcontroller unit.

[0058] S07. Use an integration module to process the back electromotive force signal by sampling integration. Transmit the collected back electromotive force voltage value to an accumulator, and accumulate the back electromotive force voltage value in the accumulator within a certain time. Transmit the total back electromotive force voltage value accumulated within a certain time to a divider, and divide the total back electromotive force voltage value by a certain value in the divider to obtain the average back electromotive force voltage value to judge whether the motor is stationary.

[0059] Specifically, in step S07, the method of sampling integration includes the following steps:

[0060] S071. Set an integration time window in the accumulator;

[0061] S072. Within the integration time window, accumulate the collected back electromotive force voltage values.

[0062] S073. Divide the accumulated result by a set dividend threshold to obtain an average back electromotive force voltage value;

[0063] S074. Determine whether the motor is stationary according to the magnitude of the average back electromotive force voltage value.

[0064] Among them, the step of determining whether the motor is stationary includes: setting a judgment threshold, which is a fixed value preset according to the motor characteristics and ADC resolution and is not limited in this embodiment. When the average back electromotive force voltage value is less than or equal to the judgment threshold, it is determined that the motor is in a stationary state and the motor starts; otherwise, it will re-enter step S05 for judgment.

[0065] The dividend threshold takes a definite value or a range value from the numerical range of the length of the integration time window.

[0066] The value range of the dividend threshold within the integration time window is: select a definite value within the length of the integration time window, and respectively select several values within ±0.3 s of this definite value as the dividend threshold for calculation, and then take a suitable value from the obtained values for calculation to obtain the average back electromotive force voltage value.

[0067] In traditional ADC sampling calculation, generally, by selecting several sampling time points, the back electromotive force voltage values corresponding to the sampling time points are obtained to judge whether the working state of the motor is in a stationary state. Under normal conditions, the back electromotive force voltage value of the motor is generally in a smooth curve state within a certain period of time due to certain fluctuations. According to the peak and valley values on the curve, the working state of the motor can be judged as starting or stationary. However, due to the problem of interfering electric waves in the circuit and the surrounding environment. When interfering electric waves appear, it will cause abnormal sudden rises and falls in the detected curve graph. If the ADC samples exactly at the interfering electric wave, misjudgment will occur, that is, when the motor is in a stationary state, due to the appearance of interfering electric waves, an abnormal peak appears in the curve graph and is collected by the ADC, and then it is judged that the motor is currently in a non-stationary state, so misjudgment occurs, which has a greater impact on the actual work.

[0068] The back electromotive force detection and processing method provided by the present invention accumulates the collected back electromotive force voltage values within the integration time window and then divides by the set dividend threshold. Since the peaks caused by clutter are accidental, through the sampling integration method, the obtained average value can be close to the normal size, so as to ensure that when judging this value, the clutter interference is excluded and the detection and judgment result is more accurate.

[0069] In a specific embodiment, taking a ceiling fan as an example, when the microcontroller unit receives a control signal from the outside, it starts the motor and drives the fan blades connected to the motor to rotate. At the same time, the microcontroller unit enters the forward and reverse state judgment and continuously judges the current state of the motor. When the motor is stationary, the microcontroller unit judges the stationary state of the motor and then enters the lower bridge arm braking state. At this time, the lower bridge arm outputs a low-duty cycle to short-circuit the three phases, causing the fan blades to stop swinging. While the lower bridge arm outputs a low-duty cycle, the ADC module collects the back electromotive force voltage value and feeds the collected back electromotive force voltage value back to the microcontroller unit. Generally, the back electromotive force voltage value collected by the ADC module is in a curve shape within the integration time window. This curve is a smooth curve with a regular and stable waveform, and the peak and valley values are relatively stable. When there is clutter interference, abnormal sudden rises and falls will appear in the waveform, that is, there is a spike voltage, which means abnormal ADC acquisition. The microcontroller unit receives and processes the back electromotive force voltage value collected by the ADC module and feeds it into the accumulator for cumulative integration calculation to obtain the total cumulative back electromotive force voltage value. By using a divider to calculate the waveform, the total cumulative back electromotive force voltage value is divided by the set dividend threshold range to obtain multiple values, and a stable and appropriate value is selected from the obtained values as the average back electromotive force voltage value. The average back electromotive force voltage value is judged to determine whether the motor is truly in a stationary state. Through the sampling integration method, the obtained average value can be made close to the normal size, so as to ensure that when judging this value, clutter interference is excluded and the detection and judgment result is more accurate. By the above steps, it is judged whether the motor is truly in a stationary state, so as to avoid misjudgment of the motor state caused by the incomplete stop of the fan blades, and at the same time exclude clutter interference in the detection process, effectively improving the accuracy of the detection and judgment result of the working state of the ceiling fan motor.

[0070] According to the simulation data and calculation results, if the average back electromotive force voltage value of the motor within the given integration time window is greater than the set judgment threshold, it is judged that the motor is not in a stationary state. If the average back electromotive force voltage value of the motor within the given integration time window is less than the set judgment threshold, it is judged that the motor is in a stationary state. This result can help the microcontroller unit make further control decisions, such as maintaining the current state or performing a commutation operation.

[0071] This embodiment demonstrates the application of the back electromotive force detection and processing method in the judgment of the motor stationary state through the calculation of simulation data. By sampling and accumulating within the integration time window and calculating the average value, and comparing with the judgment threshold, clutter interference can be effectively excluded and the judgment accuracy can be improved. The application of this method helps to improve the performance and reliability of the motor control system.

[0072] Adopting this back electromotive force detection and processing method has the following advantages:

[0073] 1. Improve the motor control accuracy: This back electromotive force detection technology allows the system to monitor the state of the motor in real time during operation, including key parameters such as position and speed. This real-time monitoring ability, combined with advanced control algorithms, enables more precise motor control. For example, in the motor control of electric vehicles, by detecting the zero-crossing position of the back electromotive force through the zero-crossing detection method, the influence of the back electromotive force can be effectively reduced, improving the driving performance and safety of the vehicle.

[0074] 2. Enhance the robustness of the system: The back electromotive force detection and processing method enhances the resistance of the motor control system to external interference and internal faults by identifying and eliminating abnormal signals. For example, by optimizing the control through software algorithms to reduce the influence of the back electromotive force, the system can maintain stable operation in the face of input errors, disk failures, etc.

[0075] 3. Achieve sensorless control: By adopting the back electromotive force detection and processing method, precise monitoring and control of the motor state can be achieved without relying on external sensors. This method reduces the system cost and complexity while improving the system reliability. For example, sensorless vector control technology can enhance the performance of the motor system, reduce power consumption, and meet the requirements of new regulations for improving energy efficiency.

[0076] 4. Optimize the motor startup and control efficiency: The back electromotive force detection technology can adjust the control strategy in real time during motor startup and operation to optimize the control of motor efficiency. For example, by improving the efficiency control to promote the optimization analysis of the motor, the maximization of motor control efficiency can be achieved under different working conditions.

[0077] 5. Improve the intelligent level of the motor system: The combination of the back electromotive force detection technology and modern intelligent algorithms can improve the intelligent level of the motor system. For example, by adopting various speed drop compensation algorithms based on radial basis neural networks, Gaussian processes, and normal distribution inner loop mapping, the safety and stability of eVTOL can be improved.

[0078] 6. Reduce the system cost: Since the back electromotive force detection technology can reduce the dependence on external sensors, the hardware cost is reduced. At the same time, by optimizing the control strategy and reducing unnecessary hardware, the system cost can be further reduced.

[0079] 7. Increase the flexibility of motor control: The back electromotive force detection technology can adapt to different motor types and operating conditions, providing flexible control options. For example, sensorless vector control technology can implement precise control according to the real-time changes in system behavior in different applications.

[0080] 8. Enhance the self-diagnosis ability of the motor system: By continuously monitoring the change of the back electromotive force voltage value, the system can self-diagnose the state of the motor and promptly detect and handle potential problems. For example, in the research on mechanical fault diagnosis based on self-sensing of the motor drive system, the motor driver can be used as a sensor to achieve mechanical fault diagnosis without additional sensing devices.

[0081] This method for detecting and processing the back electromotive force mainly collects the back electromotive force through a single-channel ADC and processes it with an integration algorithm. It is not limited by the number of chip pins, is applicable to most chips, has strong versatility, and the sampling integration method can well avoid signal interference problems during the acquisition process, quickly judge the current state of the motor, has a fast response, and when actually using the product, the user will not feel that the motor takes a long time to start rotating after power-on. It optimizes the user experience effect.

[0082] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A back electromotive force detection and processing method, characterized in that: The steps include: S01, first use the observer to determine the forward and reverse rotation state of the motor at medium and high speed; S02, select one phase of the three-phase output and connect it to the low voltage divider circuit; S03, collecting the voltage value of the phase through the voltage-dividing resistor to restore the back electromotive force of the motor; S04, the micro control unit receives a start signal sent from the outside, enters the forward and reverse state judgment, and judges the current state of the motor; S05, if it is determined that the motor is stationary, the microcontroller unit enters the lower bridge arm braking state and outputs a fixed duty cycle to short-circuit the three phases; S06, when the duty cycle is at a low level, the back electromotive force voltage value is collected through the ADC module, and the collected back electromotive force voltage value is fed back to the micro control unit; S07. Process the back electromotive force signal using a sampling integration method, accumulate the collected back electromotive force voltage values ​​within a certain period of time, and then divide them by a certain value to obtain an average back electromotive force voltage value to determine whether the motor is stationary.

2. A back electromotive force detection and processing method according to claim 1, characterized in that: The sampling integration method comprises the following steps: S071. Set an integration time window; S072, within the integration time window, accumulating the collected back electromotive force voltage values; S073, dividing the accumulated result by the set dividend threshold to obtain an average back electromotive force voltage value; S074. Determine whether the motor is stationary based on the average back electromotive force voltage value.

3. A back electromotive force detection and processing method according to claim 1, characterized in that: The step of judging whether the motor is stationary includes: setting a judgment threshold, and when the average back electromotive force voltage value is less than or equal to the judgment threshold, judging that the motor is stationary, and starting the motor; otherwise, re-entering step S05 for judgment.

4. A back electromotive force detection and processing method according to claim 2, characterized in that: The dividend threshold takes a fixed value or a range value from the numerical range of the length of the integration time window.

5. A back electromotive force detection and processing method according to claim 4, characterized in that: The value range of the dividend threshold in the integration time window is: select a certain value within the length of the integration time window, and select several values ​​within ±0.3s of the certain value as the dividend threshold for calculation, and then take a suitable value from the obtained value to calculate the average back electromotive force voltage value.

6. A back electromotive force acquisition wiring circuit, used to implement a back electromotive force detection and processing method and acquisition wiring circuit thereof according to any one of claims 1 to 5, characterized in that: include: A micro control unit, used for executing the judgment and control steps in the back electromotive force detection and processing method and its acquisition wiring circuit; ADC module, used to collect back electromotive force signals; An integration module, used to implement the sampling integration processing method; The micro control unit is connected and communicated with the ADC module and the integration module respectively.

7. A back electromotive force collection wiring circuit according to claim 6, characterized in that: The integration module comprises: An accumulator, used to accumulate the collected back electromotive force voltage value; The divider is used to divide the accumulated result by the set dividend threshold.

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