Unmanned aerial vehicle electrical speed measurement system

Abstract

The invention discloses an unmanned aerial vehicle electrical speed measurement system, and the system comprises a photoelectric encoder which is used for collecting first speed data of an unmanned aerial vehicle; the Hall sensor is used for collecting second speed data of the unmanned aerial vehicle; the inertial measurement unit is used for collecting third speed data of the unmanned aerial vehicle; the data fusion module is used for receiving the first speed data, the second speed data and the third speed data acquired by the photoelectric encoder, the Hall sensor and the inertial measurement unit, and performing data fusion on the first speed data, the second speed data and the third speed data to obtain a fusion speed; and the controller is used for receiving the fusion speed and controlling the unmanned aerial vehicle based on the fusion speed. According to the electrical speed measurement system for the unmanned aerial vehicle, speed data of the photoelectric encoder, the Hall sensor and the inertial measurement unit are fused, measurement errors can be greatly reduced, and more accurate speed information can be provided.

Description

Technical Field

[0001] The present invention specifically relates to an electrical speed measuring system for an unmanned aerial vehicle. Background Art

[0002] At present, the following common solutions are mainly used for drone speed measurement:

[0003] 1. Speed ​​measurement based on satellite positioning system (such as GPS): relies on receiving satellite signals to calculate the speed of the drone. The principle is to infer the speed of the drone relative to the satellite through information such as the Doppler frequency shift of the satellite signal.

[0004] 2. Speed ​​measurement based on aerodynamic principles: mainly uses sensors to measure airflow pressure, wind speed and other parameters, and then calculates the flight speed of the drone based on aerodynamic formulas.

[0005] 3. Speed ​​measurement based on optical sensors (such as cameras): Use optical devices such as cameras to collect images, and estimate the speed of the drone by analyzing the moving distance and time relationship between continuous frames of specific objects (such as ground textures, landmarks, etc.) in the image.

[0006] However, the satellite positioning system is susceptible to signal obstruction and interference, and its accuracy decreases in environments with tall buildings and mountainous areas. Aerodynamic speed measurement has high requirements for environmental conditions, and airflow changes will affect the accuracy of the measurement results. Optical sensor speed measurement has limited performance in poor light (such as at night and in backlight), and the image processing calculation is large.

[0007] Some existing technologies also use encoders to measure speed, but encoders are easily affected by environmental factors and their accuracy may be reduced in complex environments. Summary of the invention

[0008] The present invention provides a UAV electrical speed measurement system to solve the above-mentioned technical problems, and specifically adopts the following technical solutions:

[0009] An unmanned aerial vehicle electrical speed measurement system, comprising:

[0010] Photoelectric encoder, used to collect the first speed data of the drone;

[0011] Hall sensor, used to collect the second speed data of the drone;

[0012] An inertial measurement unit, used to collect the third speed data of the drone;

[0013] a data fusion module, configured to receive the first speed data, the second speed data and the third speed data collected by the photoelectric encoder, the Hall sensor and the inertial measurement unit, and perform data fusion on the first speed data, the second speed data and the third speed data to obtain a fused speed;

[0014] The controller is used to receive the fusion speed and control the drone based on the fusion speed.

[0015] Furthermore, the data fusion module performs data fusion on the first speed data, the second speed data and the third speed data by using the following formula:

[0016] V=aV1+bV2+cV3,a+b+c=1,a,b,c>0

[0017] Among them, V is the fusion speed, V1 is the first speed data, V2 is the second speed data, V3 is the third speed data, a, b, c are the calculation weights of the first speed data, the second speed data and the third speed data respectively.

[0018] Furthermore, a is greater than b and c.

[0019] Furthermore, the UAV electrical speed measurement system further comprises:

[0020] A fault detection module, used for detecting the state of the photoelectric encoder;

[0021] When the photoelectric encoder is in a normal state, the data fusion module performs data fusion on the first speed data, the second speed data and the third speed data to obtain the fused speed;

[0022] When the photoelectric encoder is in an abnormal state, the data fusion module performs data fusion on the second speed data and the third speed data to obtain the fused speed.

[0023] Furthermore, the fault detection module detects the signal strength of the photoelectric encoder and the fluctuation range of the first speed data, and determines that the state of the photoelectric encoder is abnormal when the signal strength is lower than a preset strength and / or the fluctuation range of the first speed data exceeds a preset value.

[0024] Furthermore, the data fusion module performs data fusion on the second speed data and the third speed data by using the following formula:

[0025] V=dV2+eV3, d+e=1, d,e>0

[0026] Wherein, V is the fusion speed, V2 is the second speed data, V3 is the third speed data, d and e are the calculation weights of the second speed data and the third speed data respectively.

[0027] Furthermore, the UAV electrical speed measurement system further comprises:

[0028] The adaptive adjustment module is used to adjust the data fusion mode of the data fusion module according to the environmental status of the UAV.

[0029] Furthermore, the adaptive adjustment module adjusts the calculation weights of the second speed data and the third speed data according to the drone environment state.

[0030] Furthermore, the UAV electrical speed measurement system further comprises:

[0031] The data processing module is used to filter and correct the first speed data, the second speed data and the third speed data, and send the processed first speed data, the second speed data and the third speed data to the data fusion module.

[0032] Furthermore, the data processing module dynamically adjusts correction parameters for correcting the first speed data, the second speed data, and the third speed data according to the flight state and environmental state of the UAV.

[0033] The benefit of the present invention lies in that the provided UAV electrical speed measurement system integrates the speed data of the photoelectric encoder, the Hall sensor and the inertial measurement unit, which can greatly reduce the measurement error and provide more accurate speed information.

[0034] The present invention is also beneficial in that the provided UAV electrical speed measurement system has a mode switching function, which can discard the detection data of the photoelectric encoder when the photoelectric encoder is abnormal, thereby reducing environmental interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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 only 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.

[0036] Figure 1 Schematic diagram of the UAV electrical speed measurement system of the present application. DETAILED DESCRIPTION

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0040] like Figure 1 The figure shows an electrical speed measurement system for a UAV of the present application, which includes: a photoelectric encoder, a Hall sensor, an inertial measurement unit (IMU), a data fusion module and a controller.

[0041] The photoelectric encoder is connected to the moving parts of the drone to collect the first speed data of the drone. Specifically, the photoelectric encoder generates a pulse signal by detecting the change in the rotation angle of the rotating shaft, which can directly measure the rotation speed of the moving parts of the drone and convert it into a linear speed. Under ideal conditions, the measurement accuracy of the photoelectric encoder can be as high as ±0.1%, but it is easily affected by environmental factors (such as dust, vibration, electromagnetic interference, etc.), and the accuracy may be reduced in complex environments.

[0042] The Hall sensor is used to collect the second speed data of the drone. The Hall sensor can generate a corresponding voltage signal according to the change of the magnetic field. The Hall sensor has good anti-interference performance, especially insensitive to electromagnetic interference. It is used as a backup and supplement when the photoelectric encoder is interfered or fails. Although its measurement accuracy is slightly lower than that of the photoelectric encoder, it can still meet the basic speed measurement requirements, which is about ±0.5%.

[0043] The inertial measurement unit is used to collect the third speed data of the drone. The data it outputs contains digital signals of acceleration and attitude (roll angle, pitch angle, yaw angle) information.

[0044] The data fusion module is used to receive the first speed data, the second speed data and the third speed data collected by the photoelectric encoder, the Hall sensor and the inertial measurement unit, and perform data fusion on the first speed data, the second speed data and the third speed data to obtain the fusion speed. The controller is used to receive the fusion speed and control the UAV based on the fusion speed. Here, the controller is the flight control system of the UAV.

[0045] In an embodiment of the present application, the UAV electrical speed measurement system further includes: a data processing module.

[0046] The data processing module is used to perform data processing on the first speed data, the second speed data and the third speed data, and send the processed first speed data, the second speed data and the third speed data to the data fusion module.

[0047] In the implementation manner of the present application, the data processing module performs filtering and correction processing on the first speed data, the second speed data and the third speed data. Specifically, as follows:

[0048] Adaptive filtering: adjusts filter parameters in real time according to the characteristics of the input signal to remove noise of different frequencies, such as enhancing the filtering effect of high-frequency electromagnetic interference noise (above 1kHz).

[0049] Kalman filter: Fusion of predicted values ​​and measured values ​​to make optimal estimates of sensor data. For example, using IMU acceleration information through Kalman filtering to more accurately estimate the speed change trend.

[0050] Error correction processing: Error correction is performed on the detection data of different sensors, such as the scale error of the photoelectric encoder, the zero bias error of the Hall sensor, etc. The error range is controlled through pre-calibration and real-time monitoring.

[0051] In the implementation mode of the present application, the data processing module dynamically adjusts the correction parameters for correcting the first speed data, the second speed data and the third speed data according to the flight state and environmental state of the drone. Specifically, according to the flight state information of the drone, such as the flight altitude, speed, acceleration, and environmental change factors such as ambient temperature, humidity, and air pressure, and taking into account the performance drift of the sensor (such as the decrease in the accuracy of the photoelectric encoder after long-term operation, the zero bias change of the IMU, etc.), the calibration parameters are adjusted in real time. For example, in high-altitude areas (air pressure is lower than 70% of the standard atmospheric pressure), since changes in air density will affect the performance of the photoelectric encoder and the Hall sensor, the system will automatically adjust the calibration coefficient; when the drone accelerates or decelerates, the calibration parameters of the IMU will also change accordingly to ensure high-precision speed measurement. The details are as follows.

[0052] 1. Adjust based on flight status

[0053] Flight altitude: When flying at different altitudes, factors such as air density will change. For example, when the drone rises to a high altitude (air pressure is less than 70% of the standard atmospheric pressure), the reduced air density will affect the performance of the photoelectric encoder and Hall sensor. At this time, the data processing module will monitor the air pressure change and automatically increase the calibration coefficient of the photoelectric encoder and Hall sensor according to the pre-set altitude-calibration parameter correspondence, which may be adjusted from the original coefficient value of 1.0 to 1.2 to compensate for the measurement error caused by the reduced air density.

[0054] Flight speed and acceleration: When the drone accelerates or decelerates, the IMU zero bias will change. When the acceleration increases from 0 to 5m / s 2 The data processing module will adjust the IMU calibration parameters according to the change of acceleration value. Assuming that the acceleration increases by 1m / s 2 , the zero bias correction value in the IMU calibration parameters needs to be increased by 0.05, then the zero bias correction value will be increased accordingly to ensure the accuracy of speed measurement.

[0055] 2. Adjust based on environmental changes

[0056] Temperature: Temperature has a significant impact on sensor performance. For example, when the ambient temperature rises from 25°C to 40°C, the internal parts of the photoelectric encoder may undergo slight dimensional changes due to thermal expansion and contraction, affecting the measurement accuracy. The data processing module will adjust the calibration parameters of the photoelectric encoder according to the temperature change detected by the temperature sensor and the relationship curve between temperature and calibration coefficient. For example, for every 5°C increase in temperature, the calibration coefficient will decrease by 0.02 to correct the error caused by temperature.

[0057] Humidity: A high humidity environment may cause changes in the electrical characteristics of the sensor's internal circuit, such as resistance and capacitance. When the humidity rises from 50% to 80%, the output signal of the Hall sensor may drift. The data processing module will adjust the calibration parameters of the Hall sensor according to the change in humidity. Assuming that for every 10% increase in humidity, the gain calibration parameters of the Hall sensor need to be adjusted by 0.03 to ensure measurement accuracy.

[0058] Air pressure: In addition to being related to altitude, changes in air pressure also affect physical parameters such as the dielectric constant of the air, which in turn affects sensor performance. For example, when the air pressure drops from standard atmospheric pressure to 80kPa, the measurement accuracy of the IMU may decrease. The data processing module will adjust the calibration parameters of the IMU in real time according to the changes in air pressure. For example, for every 5kPa drop in air pressure, the calibration coefficient of the IMU will be adjusted by 0.01.

[0059] In the implementation manner of the present application, the data fusion module performs data fusion on the first speed data, the second speed data and the third speed data by using the following formula:

[0060] V=aV1+bV2+cV3,a+b+c=1,a,b,c>0

[0061] Wherein, V is the fusion speed, V1 is the first speed data, V2 is the second speed data, V3 is the third speed data, and a, b, and c are the calculation weights of the first speed data, the second speed data, and the third speed data, respectively. It can be understood that in the data fusion process, different weights are assigned according to the accuracy and reliability of each sensor. For example, the photoelectric encoder has a higher accuracy and can be assigned a higher weight. In an embodiment of the present application, a is greater than b and c. For example, the weight of the photoelectric encoder is 0.5, the weight of the Hall sensor is 0.3, and the weight of the inertial measurement unit is 0.2.

[0062] In an embodiment of the present application, the UAV electrical speed measurement system further includes: a fault detection module.

[0063] The fault detection module is used to detect the state of the photoelectric encoder. In an embodiment of the present application, the fault detection module detects the signal strength of the photoelectric encoder and the fluctuation range of the first speed data. When the signal strength is lower than a preset strength and / or the fluctuation range of the first speed data exceeds a preset value, the state of the photoelectric encoder is determined to be an abnormal state. For example, when the signal strength of the photoelectric encoder suddenly decreases by more than 50% or the data fluctuation exceeds 20% of the normal range, the switching mechanism is triggered. At the same time, the state of the photoelectric encoder is continuously monitored, and once it returns to normal (the signal strength returns to more than 90% of the normal level, and the data fluctuation is within the normal range), it is switched back.

[0064] When the photoelectric encoder is in a normal state, the data fusion module performs data fusion on the first speed data, the second speed data and the third speed data to obtain a fusion speed.

[0065] When the photoelectric encoder is in an abnormal state, the data fusion module fuses the second speed data and the third speed data to obtain a fused speed. When the photoelectric encoder is in an abnormal state, the first speed data collected by the photoelectric encoder is discarded, and the fused speed is calculated only through the second speed data and the third speed data.

[0066] In an embodiment of the present application, the data fusion module performs data fusion on the second speed data and the third speed data by using the following formula:

[0067] V=dV2+eV3, d+e=1, d,e>0

[0068] Wherein, V is the fusion speed, V2 is the second speed data, V3 is the third speed data, d and e are the calculation weights of the second speed data and the third speed data respectively.

[0069] In the data fusion process, the weights of the Hall sensor and IMU can be determined from the following aspects:

[0070] 1. Based on sensor accuracy

[0071] The Hall sensor and IMU are tested for accuracy under different environmental conditions and different measurement ranges. For example, the speed measurement errors of the Hall sensor and IMU are recorded in a variety of typical flight scenarios (such as stable flight, acceleration, deceleration, flight at different altitudes, etc.).

[0072] Assign weights based on the accuracy data obtained from the test. If the average measurement error of the Hall sensor in most scenarios is ±2%, and the average measurement error of the IMU is ±3%, the weights can be initially assigned in inverse proportion to the errors. Assuming the total weight is 1, the weight of the Hall sensor may be 3÷(2+3)=0.6, and the weight of the IMU may be 2÷(2+3)=0.4.

[0073] 2. Based on sensor stability

[0074] Analyze the data stability of the Hall sensor and IMU during long-term operation. Observe the fluctuation of the data, for example, record the measurement data at regular intervals (such as 1 minute) over a continuous period of time (such as 1 hour), and calculate the standard deviation of the data.

[0075] Sensors with better stability are given higher weights. If the standard deviation of the Hall sensor data is 0.5 and the standard deviation of the IMU data is 0.8, the weights are assigned in inverse proportion to the stability. The weight of the Hall sensor may be 0.8÷(0.5+0.8)≈0.62, and the weight of the IMU may be about 0.5÷(0.5+0.8)≈0.38.

[0076] 3. Based on environmental adaptability

[0077] Consider the impact of different flight environments on sensors. For example, in a strong magnetic field environment, the Hall sensor may be greatly disturbed, reducing its reliability; and in an environment with high acceleration changes, the IMU measurement may have a large error accumulation.

[0078] The weights are adjusted according to the probability of different environments and the degree of impact on the sensor. Assume that in the current flight mission, the probability of a strong magnetic field environment is 30%, and the probability of a high acceleration change environment is 20%. In a non-strong magnetic field environment, the weight of the Hall sensor is set to 0.7 and the weight of the IMU is 0.3; in a strong magnetic field environment, the weight of the Hall sensor is reduced to 0.4 and the weight of the IMU is increased to 0.6.

[0079] In an embodiment of the present application, the UAV electrical speed measurement system further includes an adaptive adjustment module. The adaptive adjustment module is used to adjust the data fusion mode of the data fusion module according to the flight state and environmental state of the UAV. Specifically, in an embodiment of the present application, the adaptive adjustment module adjusts the calculation weights of the first speed data, the second speed data, and the third speed data according to the flight state and environmental state of the UAV.

[0080] The UAV electrical speed measurement system of the present application adopts high-speed serial communication technology, such as CAN bus or SPI communication protocol. CAN bus has high reliability and real-time performance, and the communication rate can reach 1Mbps, which can meet the requirements of speed data transmission when the UAV is flying at high speed. SPI communication protocol is simple and efficient, and the data transmission rate can be adjusted according to actual needs.

[0081] By optimizing the parameter settings and data frame format of the communication protocol, data delay and loss can be reduced. For example, by setting a reasonable communication baud rate, data verification method, etc., it is ensured that the speed data can be transmitted to the flight control system in a timely and accurate manner, and the data transmission delay can be controlled within 10ms.

[0082] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. An electrical speed measurement system for a drone, characterized in that: Include: Photoelectric encoder, used to collect the first speed data of the drone; Hall sensor, used to collect the second speed data of the drone; An inertial measurement unit, used to collect the third speed data of the drone; a data fusion module, configured to receive the first speed data, the second speed data and the third speed data collected by the photoelectric encoder, the Hall sensor and the inertial measurement unit, and perform data fusion on the first speed data, the second speed data and the third speed data to obtain a fused speed; The controller is used to receive the fusion speed and control the drone based on the fusion speed.

2. The UAV electrical speed measurement system according to claim 1, characterized in that: The data fusion module performs data fusion on the first speed data, the second speed data and the third speed data by using the following formula: V=aV1+bV2+cV3,a+b+c=1,a,b,c>0 Among them, V is the fusion speed, V1 is the first speed data, V2 is the second speed data, V3 is the third speed data, a, b, c are the calculation weights of the first speed data, the second speed data and the third speed data respectively.

3. The UAV electrical speed measurement system according to claim 2, characterized in that: a is greater than b and c.

4. The UAV electrical speed measurement system according to claim 1, characterized in that: The UAV electrical speed measurement system also includes: A fault detection module, used for detecting the state of the photoelectric encoder; When the photoelectric encoder is in a normal state, the data fusion module performs data fusion on the first speed data, the second speed data and the third speed data to obtain the fused speed; When the photoelectric encoder is in an abnormal state, the data fusion module performs data fusion on the second speed data and the third speed data to obtain the fused speed.

5. The UAV electrical speed measurement system according to claim 4, characterized in that: The fault detection module detects the signal strength of the photoelectric encoder and the fluctuation range of the first speed data, and determines that the state of the photoelectric encoder is an abnormal state when the signal strength is lower than a preset strength and / or the fluctuation range of the first speed data exceeds a preset value.

6. The UAV electrical speed measurement system according to claim 4, characterized in that: The data fusion module performs data fusion on the second speed data and the third speed data by using the following formula: V=dV2+eV3, d+e=1, d,e>0 Wherein, V is the fusion speed, V2 is the second speed data, V3 is the third speed data, d and e are the calculation weights of the second speed data and the third speed data respectively.

7. The UAV electrical speed measurement system according to any one of claims 1 to 6, characterized in that: The UAV electrical speed measurement system also includes: The adaptive adjustment module is used to adjust the data fusion mode of the data fusion module according to the environmental status of the UAV.

8. The UAV electrical speed measurement system according to claim 7, characterized in that: The adaptive adjustment module adjusts the calculation weights of the second speed data and the third speed data according to the environmental state of the drone.

9. The UAV electrical speed measurement system according to claim 1, characterized in that: The UAV electrical speed measurement system also includes: The data processing module is used to filter and correct the first speed data, the second speed data and the third speed data, and send the processed first speed data, the second speed data and the third speed data to the data fusion module.

10. The UAV electrical speed measurement system according to claim 9, characterized in that: The data processing module dynamically adjusts correction parameters for correcting the first speed data, the second speed data, and the third speed data according to the flight state and environmental state of the drone.

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