Propeller detection method based on back electromotive force waveform, electronic speed regulator and system

Abstract

This invention discloses a propeller detection method, electronic speed governor, and system based on back electromotive force (EMF) waveform. The method includes: the electronic speed governor receiving commands from the flight control system, entering an installation detection mode, and driving a brushless motor connected to the propeller to rotate at a constant low speed; acquiring the three-phase terminal voltage signals of the brushless motor, filtering them to obtain three-phase back EMF waveforms; performing symmetry analysis on these waveforms to obtain waveform symmetry characteristic quantities; performing harmonic analysis on these waveforms to extract the amplitude of the propeller's mechanical rotation frequency and the amplitude of its second harmonic, and calculating the harmonic ratio; comparing the characteristic quantities with a preset threshold to obtain the detection result; and reporting a status code through a communication interface. This invention also discloses an electronic speed governor implementing this method and a system incorporating the electronic speed governor. This invention utilizes the existing back EMF sampling circuit of the electronic speed governor to achieve automatic pre-flight detection of propeller installation quality and static balance without adding hardware, thereby improving flight safety.

Description

Technical Field

[0001] This invention relates to the field of electronic speed controller technology for unmanned aerial vehicles (UAVs), specifically to a propeller detection method, electronic speed controller, and system based on back electromotive force waveform. Background Technology

[0002] Multi-rotor drones rely on the rotation of propellers to generate lift, and the installation quality and static balance of the propellers directly affect flight safety and efficiency. Common problems include poor installation (such as propeller mount eccentricity, inconsistent blade angles, uneven torque of fixing screws, etc.) and static imbalance (i.e., uneven mass distribution of the propeller blades themselves).

[0003] Currently, detecting these problems mainly relies on manual visual inspection or dedicated dynamic balancing instruments. However, manual inspection is inefficient and prone to oversight, while external balancing instruments cannot perform automatic checks before each takeoff. Existing electronic speed governors (ESGs) in sensorless FOC control must estimate rotor position by sampling back EMF. This data is currently only used for commutation control and has not yet been used to analyze the propeller's mechanical condition. If the ESG's existing back EMF sampling circuit could automatically detect the propeller's installation quality and static balance during the low-speed rotation phase on the ground before takeoff, flight accidents caused by blade problems could be effectively prevented without adding any hardware.

[0004] Therefore, there is an urgent need for a method and device that can automatically detect the propeller installation mass and static balance state before takeoff by utilizing the existing back EMF sampling circuit of the electronic speed governor. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a propeller detection method, electronic speed controller, and system based on back electromotive force waveform. During the low-speed rotation of the UAV on the ground before takeoff, the symmetry and harmonic components of the back electromotive force waveform are automatically analyzed to determine whether the propeller is improperly installed or statically unbalanced, and corresponding prompts or automatic shutdown are given, thereby improving flight safety.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A propeller detection method based on back EMF waveform, executed by an UAV electronic speed controller including a back EMF sampling circuit and a communication interface, the method comprising the following steps: S1. Receive the detection command from the UAV flight control system and enter the installation detection mode; in the installation detection mode, drive the brushless motor connected to the propeller under test to rotate at a constant low speed in an open loop, with the constant low speed being lower than the normal takeoff speed of the propeller. S2. During the rotation of the brushless motor, the three-phase terminal voltage signal of the brushless motor is continuously collected through the back electromotive force sampling circuit, and the three-phase back electromotive force waveform is obtained after filtering. S3. Perform symmetry analysis on the three back electromotive force waveforms to obtain at least one waveform symmetry characteristic quantity; S4. Perform harmonic analysis on the three-phase back electromotive force waveforms to extract the amplitude of the propeller's mechanical rotation frequency. A 1f And the amplitude of twice the mechanical rotation frequency of the propeller A 2f Calculate the harmonic ratio And this harmonic ratio is used as a harmonic characteristic quantity; S5. Compare the feature values ​​obtained in S3 and S4 with the preset threshold to obtain the detection results; S6. Report the status code corresponding to the detection result to the flight control system through the communication interface.

[0007] Furthermore, the constant speed is 100 rpm to 300 rpm.

[0008] Furthermore, the waveform symmetry characteristic quantities include at least one of the following: the phase deviation between the three back EMF waveforms, the asymmetry of each phase waveform in the three back EMF waveforms, and the peak-to-valley ratio of each phase waveform in the three back EMF waveforms.

[0009] Furthermore, the phase deviation between the three back electromotive force waveforms is calculated as follows: The zero-crossing times of the three-phase back EMF waveforms are detected separately, and the phase difference between every two phases in the three-phase back EMF waveforms is calculated and denoted as . i ab , i bc and i ca ;in, i ab The phase difference between phase A and phase B. i bc This represents the phase difference between phase B and phase C. i ca This represents the phase difference between phase C and phase A. Calculate the phase deviation of 120° , .

[0010] Furthermore, the asymmetry of each phase waveform in the three-phase back electromotive force waveform is calculated as follows: For any phase waveform in the three-phase back EMF waveform, detect the peak value of the positive half-cycle of that phase waveform. V+ The absolute value of the negative half-cycle peak | V− | Calculate the degree of asymmetry : .

[0011] Furthermore, the peak-to-valley ratio of each phase waveform in the three-phase back electromotive force is calculated as follows: For any phase waveform in the three-phase back EMF waveform, detect the peak value of the positive half-cycle of that phase waveform. V+ The absolute value of the negative half-cycle peak | V− | Calculate the peak-to-valley ratio K pv : .

[0012] Furthermore, each feature is assigned a set of preset thresholds, and each set of thresholds includes a qualified threshold and a severe threshold. If all characteristic quantities are less than or equal to their respective qualified thresholds, the test result is that the propeller is installed correctly and is balanced. If any characteristic quantity is greater than the corresponding qualified threshold but less than the corresponding severe threshold, the test result is that the propeller is poorly installed or unbalanced and reinstallation is recommended. If any characteristic quantity is greater than or equal to the corresponding severity threshold, a detection result of severe propeller installation abnormality and prohibition of takeoff is obtained, and the electronic speed governor automatically stops rotating and reports an error.

[0013] Furthermore, the sampling rate for acquiring the three-phase terminal voltage signals is 10 kHz per channel, and the continuous acquisition time is 2 seconds.

[0014] An electronic speed controller for implementing the detection method includes a microcontroller unit, a three-phase inverter bridge, a back EMF sampling circuit, and a communication interface. The back EMF sampling circuit includes an ADC (Analog-to-Digital Converter); the microcontroller unit includes: The waveform acquisition module is used to acquire the three-phase terminal voltage signal of the brushless motor through the ADC analog-to-digital converter, and obtain the three-phase back electromotive force waveform after filtering. The symmetry analysis module is used to perform symmetry analysis on the three back electromotive force waveforms to obtain at least one waveform symmetry characteristic quantity. The harmonic analysis module is used to perform harmonic analysis on the three-phase back electromotive force waveform and extract the amplitude of the propeller's mechanical rotation frequency. A 1f And the amplitude of twice the mechanical rotation frequency of the propeller A 2f Calculate the harmonic ratio And this harmonic ratio is used as a harmonic characteristic quantity; The decision module compares the feature quantities obtained by the symmetry analysis module and the harmonic analysis module with the preset threshold to obtain the detection result, and outputs the status code corresponding to the detection result through the communication interface.

[0015] A system comprising the electronic speed controller, and a brushless motor and a propeller electrically connected to the electronic speed controller.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention fully utilizes the back EMF sampling circuit (including an ADC analog-to-digital converter) and microcontroller unit of the UAV's electronic speed controller, requiring no additional hardware. Automatic detection of propeller installation quality and static balance can be achieved simply by upgrading the firmware. Compared to existing technologies that require a dedicated dynamic balancing instrument or manual visual inspection, this invention does not increase hardware weight or cost, making it particularly suitable for weight-sensitive UAV platforms.

[0017] 2. This invention, after receiving the takeoff command but before actual takeoff, enters an installation and inspection mode via a detection command, driving the propeller to rotate at a constant low speed to complete the inspection. Compared to manual inspection, this invention achieves automated inspection before each takeoff, avoiding missed inspections due to negligence or human error, and effectively preventing flight accidents caused by improper propeller installation or static imbalance.

[0018] 3. This invention obtains characteristic quantities such as phase deviation between the three back EMF waveforms, asymmetry of each phase waveform, and peak-to-valley ratio of each phase waveform in the three back EMFs through symmetry analysis. These are used to determine whether there are problems such as propeller mount eccentricity, inconsistent blade angles, or uneven screw torque during propeller installation. Simultaneously, harmonic analysis extracts the harmonic ratio at twice the propeller's mechanical rotation frequency to determine whether the propeller has static imbalance caused by uneven mass distribution. The combination of these two methods enables a comprehensive assessment of the propeller's mechanical condition.

[0019] 4. This invention presets three levels of judgment criteria: a pass threshold, a warning threshold, and a severe threshold. Based on the detection results, it can output different levels of status codes, such as pass, recommended reinstallation, or severe anomaly and prohibition of takeoff, for the flight control system to make decisions. When a severe anomaly is detected, the electronic speed controller automatically stops rotating and reports an error, further ensuring safety.

[0020] 5. This invention completes the test at a speed far below the normal takeoff speed of the propeller, without the need for high-speed propeller rotation. The test process is safe, energy-efficient, and low-noise, and will not pose a danger to personnel or equipment on the ground.

[0021] 6. The detection method of the present invention is based entirely on the existing hardware architecture of electronic speed controllers. Existing products only need to upgrade the firmware modules (waveform acquisition module, symmetry analysis module, harmonic analysis module, and decision module) inside the microcontroller unit to support this function. No hardware design modifications are required, the implementation threshold is low, and it has extremely high industrial promotion value. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method of the present invention.

[0023] Figure 2 This is a modular structure diagram of the electronic speed controller and system of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] like Figure 1 As shown, the present invention provides a propeller detection method based on back EMF waveform, executed by an UAV electronic speed controller including a back EMF sampling circuit and a communication interface (UART, CAN, or PWM). The method includes the following steps: S1. Receive the detection command from the UAV flight control system and enter the installation detection mode; in the installation detection mode, drive the brushless motor connected to the propeller under test to rotate at a constant low speed in an open loop, with the constant low speed being lower than the normal takeoff speed of the propeller. S2. During the rotation of the brushless motor, the three-phase terminal voltage signal of the brushless motor is continuously collected through the back electromotive force sampling circuit, and the three-phase back electromotive force waveform is obtained after filtering. S3. Perform symmetry analysis on the three back electromotive force waveforms to obtain at least one waveform symmetry characteristic quantity; S4. Perform harmonic analysis on the three-phase back electromotive force waveforms to extract the amplitude of the propeller's mechanical rotation frequency. A 1f And the amplitude of twice the mechanical rotation frequency of the propeller A 2f Calculate the harmonic ratio And this harmonic ratio is used as a harmonic characteristic quantity; S5. Compare the feature values ​​obtained in S3 and S4 with the preset threshold to obtain the detection results; S6. Report the status code corresponding to the detection result to the flight control system through the communication interface.

[0026] The workflow of this invention is as follows: The flight control system sends a detection command to the electronic speed controller (ESC) via a communication interface. The ESC enters the installation detection mode, executes the detection method, and then reports the status code corresponding to the detection result to the flight control system via the communication interface. The ESC is electrically connected to the brushless motor and the propeller, driving the motor to rotate and thus rotating the propeller.

[0027] The detection principle of this invention is as follows: Improper propeller installation (such as propeller mount eccentricity, inconsistent blade angles, uneven screw torque) will disrupt the balance of the three-phase load of the motor, resulting in a phase deviation in the back electromotive force waveform. K θ Deviation of 120°), asymmetry in positive and negative half-cycle amplitude ( K a Increased) and abnormal peak-to-trough ratio ( K pv Deviation 1); while propeller static imbalance (uneven mass distribution) will generate a load fluctuation of twice the mechanical rotation frequency per revolution, causing a significant increase in the second harmonic in the back electromotive force spectrum ( R (Increase). By analyzing these four characteristic quantities, the installation quality and static balance of the propeller can be evaluated from the perspectives of time-domain symmetry and frequency-domain harmonic characteristics, respectively.

[0028] In this embodiment, after unlocking and before takeoff, the flight control system sends a detection command, such as "0x01" (i.e., installation detection mode), to the electronic speed controller via the CAN bus. Upon receiving the command, the electronic speed controller enters the detection mode.

[0029] In this embodiment, the harmonic ratio is sensitive to static imbalance and can be used to determine whether the propeller has a static imbalance problem caused by uneven mass distribution. A higher harmonic ratio indicates a more severe static imbalance. Experiments show that under low-speed open-loop drive conditions, propeller static imbalance unexpectedly causes a significant increase in the harmonics at twice the mechanical frequency, and the harmonic ratio... R It is positively correlated with the amount of imbalance. Therefore, the harmonic ratio can be used to determine whether a propeller has a static imbalance problem. The specific calculation of the harmonic ratio is as follows: perform a Fast Fourier Transform (1024 points window) on one phase waveform to extract the amplitude of the propeller's mechanical rotation frequency. A 1f And the amplitude of twice the mechanical rotation frequency of the propeller A 2f Calculate the harmonic ratio The harmonic ratio is used as a harmonic characteristic quantity. When the constant low speed is 200 rpm, the corresponding mechanical rotation frequency is 3.33 Hz, and twice the frequency is 6.66 Hz.

[0030] In one embodiment, the constant speed is 100 rpm to 300 rpm.

[0031] In this embodiment, a constant speed of 200 rpm is taken as an example. At this speed, the electrical frequency of the brushless motor is approximately 133 Hz (the number of pole pairs of the motor is 4), and the back electromotive force amplitude is approximately 0.5V to 1.5V, which can be directly sampled by the back electromotive force sampling circuit inside the electronic speed controller.

[0032] In one embodiment, the waveform symmetry characteristic includes at least one of the following: phase deviation between the three back EMF waveforms, asymmetry of each phase waveform in the three back EMF waveforms, and peak-to-valley ratio of each phase waveform in the three back EMF waveforms.

[0033] The aforementioned characteristic quantities are used to judge the installation quality of the propeller. When the propeller is installed well, the three-phase back electromotive force waveforms should have a standard 120° phase difference, and the positive and negative half-cycles of each phase waveform should be symmetrical.

[0034] In one embodiment, the phase deviation between the three back electromotive force waveforms is calculated as follows: The zero-crossing times of the three-phase back EMF waveforms are detected separately, and the phase difference between every two phases in the three-phase back EMF waveforms is calculated and denoted as . i ab , i bc and i ca ;in, i ab The phase difference between phase A and phase B. i bc This represents the phase difference between phase B and phase C. i ca This represents the phase difference between phase C and phase A. Calculate the phase deviation of 120° , .

[0035] In one embodiment, the asymmetry of each phase waveform in the three-phase back electromotive force waveform is calculated as follows: For any phase waveform in the three-phase back EMF waveform, detect the peak value of the positive half-cycle of that phase waveform. V+ The absolute value of the negative half-cycle peak | V− | Calculate the degree of asymmetry : .

[0036] In one embodiment, the peak-to-valley ratio of the waveform of each phase in the three-phase back electromotive force is calculated as follows: For any phase waveform in the three-phase back EMF waveform, detect the peak value of the positive half-cycle of that phase waveform. V+ The absolute value of the negative half-cycle peak | V− | Calculate the peak-to-valley ratio K pv : .

[0037] In this embodiment, a deviation from the above formula can also be used: .

[0038] K pv The closer it is to 1, the better the symmetry of the positive and negative half-cycles of the waveform; The closer it is to 0, the better the symmetry.

[0039] In one embodiment, each feature is assigned a set of preset thresholds, and each set of thresholds includes a pass threshold and a severity threshold. If all characteristic quantities are less than or equal to their respective qualified thresholds, the test result is that the propeller is installed correctly and is balanced. If any characteristic quantity is greater than the corresponding qualified threshold but less than the corresponding severe threshold, the test result is that the propeller is poorly installed or unbalanced and reinstallation is recommended. If any characteristic quantity is greater than or equal to the corresponding severity threshold, a detection result of severe propeller installation abnormality and prohibition of takeoff is obtained, and the electronic speed governor automatically stops rotating and reports an error.

[0040] In this embodiment, a set of preset thresholds are set for the three characteristic quantities: phase deviation, asymmetry, and harmonic ratio, as follows: Phase deviation K θ The acceptable threshold is 5°, and the severe threshold is 15°; asymmetry K a The acceptable threshold is 0.05, and the severe threshold is 0.15; peak-to-trough ratio K pv The acceptable threshold is 0.05, and the severe threshold is 0.15; harmonic ratio R The acceptable threshold is 0.03, and the severe threshold is 0.10. Each threshold can also be calibrated experimentally.

[0041] In this embodiment, the electronic speed governor sends a status code to the flight control system through the communication interface: "00" indicates that the propeller is installed correctly and is balanced, "01" indicates that the propeller is poorly installed or unbalanced and reinstallation is recommended, and "10" indicates that the propeller installation is seriously abnormal and takeoff is prohibited.

[0042] Based on the received status code, the flight control system displays corresponding prompts on the remote controller ground station or remote controller screen, such as: propeller installation qualified, please check propeller installation, or propeller malfunction, takeoff prohibited. The flight control system then decides whether to allow takeoff.

[0043] In one embodiment, the sampling rate for acquiring the three-phase terminal voltage signal is 10 kHz per channel, and the continuous acquisition time is 2 seconds.

[0044] In this embodiment, the acquired signal is filtered by a digital low-pass filter to remove PWM switching noise, with a cutoff frequency of, for example, 1 kHz, to obtain a smooth back EMF waveform.

[0045] like Figure 2 As shown, the present invention provides an electronic speed controller for implementing the above-described detection method, and a system comprising the electronic speed controller, a brushless motor and a propeller electrically connected to the electronic speed controller.

[0046] This electronic speed controller includes a microcontroller unit (MCU), a three-phase inverter bridge, a back EMF sampling circuit, and a communication interface. The back EMF sampling circuit includes an ADC (analog-to-digital converter). The MCU contains: The waveform acquisition module is used to acquire the three-phase terminal voltage signal of the brushless motor through the ADC analog-to-digital converter, and obtain the three-phase back electromotive force waveform after filtering. The symmetry analysis module is used to perform symmetry analysis on the three back electromotive force waveforms to obtain at least one waveform symmetry characteristic quantity. The harmonic analysis module is used to perform harmonic analysis on the three-phase back electromotive force waveform and extract the amplitude of the propeller's mechanical rotation frequency. A 1f And the amplitude of twice the mechanical rotation frequency of the propeller A 2f Calculate the harmonic ratio And this harmonic ratio is used as a harmonic characteristic quantity; The decision module compares the feature quantities obtained by the symmetry analysis module and the harmonic analysis module with the preset threshold to obtain the detection result, and outputs the status code corresponding to the detection result through the communication interface.

[0047] In this embodiment, the electronic speed controller also includes a power input terminal. The three-phase inverter bridge employs a three-phase driver chip and a MOSFET bridge. The back EMF sampling circuit includes a resistor divider network and an ADC analog-to-digital converter connected to the resistor divider network. Specifically, the back EMF sampling circuit consists of three resistor divider networks and an RC filter circuit, with its output connected to the ADC input pin of the MCU.

[0048] In this embodiment, the communication interface is a UART or CAN bus, used to receive detection commands sent by the flight control system and to report the status codes corresponding to the detection results to the flight control system.

[0049] In this embodiment, the electronic speed controller also includes a current sampling resistor (for other functions, such as current monitoring or overcurrent protection), but it is not an essential component of the detection method of the present invention.

[0050] In this embodiment, the electronic speed controller receives a detection command from the flight control system, drives the brushless motor to rotate, and drives the propeller to rotate. After executing the detection method, the electronic speed controller reports the detection result to the flight control system, which then decides whether takeoff is permitted.

[0051] The flight control system, electronic speed controller, brushless motor and other electronic equipment or components used in this invention are all existing known electrical devices, and can all be purchased and used directly on the market. Their structure, circuit and control principle are all existing known technologies. Therefore, their structure, circuit and control principle will not be described in detail here.

[0052] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions 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. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A propeller detection method based on back electromotive force waveform, characterized in that, Performed by an electronic speed controller for unmanned aerial vehicles (UAVs), including a back EMF sampling circuit and a communication interface, the method includes the following steps: S1. Receive the detection command from the UAV flight control system and enter the installation detection mode; in the installation detection mode, drive the brushless motor connected to the propeller under test to rotate at a constant low speed in an open loop, with the constant low speed being lower than the normal takeoff speed of the propeller. S2. During the rotation of the brushless motor, the three-phase terminal voltage signal of the brushless motor is continuously collected through the back electromotive force sampling circuit, and the three-phase back electromotive force waveform is obtained after filtering. S3. Perform symmetry analysis on the three back electromotive force waveforms to obtain at least one waveform symmetry characteristic quantity; S4. Perform harmonic analysis on the three-phase back electromotive force waveforms to extract the amplitude of the propeller's mechanical rotation frequency. A 1f And the amplitude of twice the mechanical rotation frequency of the propeller A 2f Calculate the harmonic ratio And this harmonic ratio is used as a harmonic characteristic quantity; S5. Compare the feature values ​​obtained in S3 and S4 with the preset threshold to obtain the detection results; S6. Report the status code corresponding to the detection result to the flight control system through the communication interface.

2. The detection method according to claim 1, characterized in that, The constant speed is 100 rpm to 300 rpm.

3. The detection method according to claim 1, characterized in that, The waveform symmetry characteristics include at least one of the following: the phase deviation between the three back EMF waveforms, the asymmetry of each phase waveform in the three back EMF waveforms, and the peak-to-valley ratio of each phase waveform in the three back EMF waveforms.

4. The detection method according to claim 3, characterized in that, The phase deviation between the three back electromotive force waveforms is calculated as follows: The zero-crossing times of the three-phase back EMF waveforms are detected separately, and the phase difference between every two phases in the three-phase back EMF waveforms is calculated and denoted as . θ ab , θ bc and θ ca ; in, θ ab The phase difference between phase A and phase B. θ bc This represents the phase difference between phase B and phase C. θ ca This represents the phase difference between phase C and phase A. Calculate the phase deviation of 120° , .

5. The detection method according to claim 3, characterized in that, The method for calculating the asymmetry of each phase waveform in the three-phase back electromotive force waveform is as follows: For any phase waveform in the three-phase back EMF waveform, detect the peak value of the positive half-cycle of that phase waveform. V+ The absolute value of the negative half-cycle peak | V− | Calculate the degree of asymmetry : 。 6. The detection method according to claim 1, characterized in that, The method for calculating the peak-to-valley ratio of the waveform of each phase in the three-phase back electromotive force is as follows: For any phase waveform in the three-phase back EMF waveform, detect the peak value of the positive half-cycle of that phase waveform. V+ The absolute value of the negative half-cycle peak | V− | Calculate the peak-to-valley ratio K pv : 。 7. The detection method according to claim 1, characterized in that, Each feature is assigned a set of preset thresholds, and each set of thresholds includes a qualified threshold and a severe threshold. If all characteristic quantities are less than or equal to their respective qualified thresholds, the test result is that the propeller is installed correctly and is balanced. If any characteristic quantity is greater than the corresponding qualified threshold but less than the corresponding severe threshold, the test result is that the propeller is poorly installed or unbalanced and reinstallation is recommended. If any characteristic quantity is greater than or equal to the corresponding severity threshold, a detection result of severe propeller installation abnormality and prohibition of takeoff is obtained, and the electronic speed governor automatically stops rotating and reports an error.

8. The propeller detection method according to claim 1, characterized in that, The sampling rate for acquiring the three-phase terminal voltage signal is 10 kHz per channel, and the continuous acquisition time is 2 seconds.

9. An electronic speed controller for implementing the detection method according to any one of claims 1 to 8, comprising a microcontroller unit, a three-phase inverter bridge, a back EMF sampling circuit, and a communication interface, characterized in that, The back EMF sampling circuit includes an ADC analog-to-digital converter; the microcontroller unit contains: The waveform acquisition module is used to acquire the three-phase terminal voltage signal of the brushless motor through the ADC analog-to-digital converter, and obtain the three-phase back electromotive force waveform after filtering. The symmetry analysis module is used to perform symmetry analysis on the three back electromotive force waveforms to obtain at least one waveform symmetry characteristic quantity. The harmonic analysis module is used to perform harmonic analysis on the three-phase back electromotive force waveform and extract the amplitude of the propeller's mechanical rotation frequency. A 1f And the amplitude of twice the mechanical rotation frequency of the propeller A 2f Calculate the harmonic ratio And this harmonic ratio is used as a harmonic characteristic quantity; The decision module compares the feature quantities obtained by the symmetry analysis module and the harmonic analysis module with the preset threshold to obtain the detection result, and outputs the status code corresponding to the detection result through the communication interface.

10. A system comprising the electronic speed controller of claim 9, and a brushless motor and a propeller electrically connected to the electronic speed controller.

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