Unmanned aerial vehicle based on magnetic field orientation and motor driving method and system thereof

Abstract

The invention is suitable for the field of motors, and provides an unmanned aerial vehicle based on magnetic field orientation and a motor driving method and system thereof. The method comprises the following steps that: a controller performs Clarke conversion on three-phase current of a motor acquired by a sampling circuit to convert the three-phase current into current in a two-phase static coordinate system; the controller performs Park conversion on the current under the two-phase static coordinate system to convert the current into current under a two-phase rotating coordinate system; the controller performs PI adjustment on the current under the two-phase rotating coordinate system to obtain a target current, and calculates the voltage of the motor under the two-phase rotating coordinate system according to the target current; the controller performs inverse Park conversion on the voltage of the motor under the two-phase rotating coordinate system to convert the voltage into the voltage under the two-phase static coordinate system; the controller carries out feedforward decoupling on the voltage of the motor under the two-phase rotating coordinate system; the controller generates an SPWM signal based on mean zero sequence injection to drive the power driver. The unmanned aerial vehicle based on magnetic field orientation is suitable for serving as a fire-fighting unmanned aerial vehicle, flight stability, efficiency and low-speed performance can be improved, and noise and vibration are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of motors, and in particular relates to a magnetic field orientation-based unmanned aerial vehicle and a motor driving method and system thereof. Background Art

[0002] Sensorless square-wave drive is a sensorless control technology primarily used for brushless DC motors (BLDCs). Its core principle is to estimate the rotor position and speed by detecting the motor's back electromotive force (EMF), thereby controlling the motor's commutation. Key technical features include back-EMF detection, six-step commutation, and zero-crossing detection. The advantages of sensorless square-wave drive include: low cost, requiring no additional position sensor, reducing hardware costs; and simple structure, resulting in a simple control algorithm that is easy to implement.

[0003] Existing firefighting drones mostly use square wave drive or sensorless control technology, which has the following problems:

[0004] 1. Low control accuracy: Square wave drive causes large fluctuations in motor torque, affecting flight stability.

[0005] 2. Low efficiency: The current waveform of the square wave drive is discontinuous and the motor efficiency is low.

[0006] 3. Large noise and vibration: The square wave driven commutation strategy causes large noise and vibration, affecting the working environment of the drone.

[0007] 4. Poor low-speed performance: At low speed or hovering state, the control performance is poor and it is difficult to meet the needs of firefighting tasks. Summary of the Invention

[0008] The purpose of the present invention is to provide a UAV based on magnetic field orientation and its motor driving method and system, aiming to solve the problems of low control accuracy, low efficiency, high noise and vibration, and poor low-speed performance.

[0009] In a first aspect, the present invention provides a motor driving method for a UAV based on magnetic field orientation, comprising the following steps:

[0010] The controller converts the three-phase current of the motor collected by the sampling circuit into the current in the two-phase stationary coordinate system through Clarke transformation;

[0011] The controller converts the current in the two-phase stationary coordinate system into the current in the two-phase rotating coordinate system through Park transformation;

[0012] The controller performs PI regulation on the current in the two-phase rotating coordinate system to obtain the target current, and calculates the voltage in the two-phase rotating coordinate system of the motor based on the target current.

[0013] The controller performs an inverse Park transform on the voltage of the motor in the two-phase rotating coordinate system and converts it back to the voltage in the two-phase stationary coordinate system;

[0014] The controller performs feedforward decoupling on the voltage in the two-phase rotating coordinate system of the motor;

[0015] The controller generates an SPWM signal based on mean-value zero-sequence injection to drive the power driver.

[0016] In the second aspect, the present invention provides a motor drive system for a UAV based on magnetic field orientation, including a controller, a motor, and a power driver and a sampling circuit electrically connected to the controller respectively. The power driver is also electrically connected to the motor and the sampling circuit respectively. The controller controls the motor using the motor drive method for a UAV based on magnetic field orientation as described above. After the mean zero-sequence injection SPWM calculation, the controller controls three complementary PWM signals through the power driver to control the voltage saddle waves at the output ends of three pairs of MOS tubes to be given to the motor.

[0017] In a third aspect, the present invention provides a UAV based on magnetic field orientation, including a motor drive system of the UAV based on magnetic field orientation.

[0018] In an embodiment of the present invention, a UAV based on magnetic field orientation is suitable for use as a firefighting UAV, which can improve flight stability, efficiency and low-speed performance, and reduce noise and vibration. In addition, because feedforward decoupling is used on the basis of the original current loop, the mutual coupling of the d-axis voltage and the q-axis voltage generated by mutual inductance is avoided, thereby improving the control efficiency. In addition, the present application optimizes the modulation effect of SPWM by injecting a zero-sequence voltage component (i.e., a mean component), improves the utilization rate of the DC bus voltage, and maintains the symmetry of the three-phase voltage. The same zero-sequence voltage component is added to the original three-phase sinusoidal modulation wave to reduce the peak value of the modulation wave, thereby outputting a higher equivalent voltage without over-modulation. The SPWM based on mean zero-sequence injection achieves the same waveform as the SVPWM achieved by the traditional sector judgment method, but the SPWM using mean zero-sequence injection has less harmonic content, greatly reduces the amount of calculation, and takes less time to calculate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a motor driving method for a UAV based on magnetic field orientation provided by an embodiment of the present invention.

[0020] Figure 2 This is a block diagram of the effect of mean zero-sequence injection.

[0021] Figure 3 Schematic diagram of a motor drive system for a UAV based on magnetic field orientation provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and beneficial effects of the present invention more clearly understood, the present invention will be further described in detail below with reference to 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 intended to limit the present invention.

[0023] In order to illustrate the technical solution of the present invention, specific embodiments are provided below.

[0024] See also Figure 1 The motor driving method of a UAV based on magnetic field orientation provided by an embodiment of the present invention includes the following steps:

[0025] S101, the controller performs Clarke transformation on the three-phase current of the motor collected by the sampling circuit to convert it into the current in a two-phase stationary coordinate system;

[0026] The Clarke transformation formula is: Among them, I a , I b , I c They represent the three-phase currents of the motor collected by the sampling circuit in the three-phase stationary coordinate system, i.e., the α-β coordinate system, I α , I β They represent the α-axis and β-axis currents of the motor in the two-phase stationary coordinate system respectively.

[0027] S102, the controller performs Park transformation on the current in the two-phase stationary coordinate system to convert it into the current in the two-phase rotating coordinate system;

[0028] The Park transformation formula is: Among them, I d , I q They represent the d-axis and q-axis currents of the motor in the two-phase rotating coordinate system, namely the dq coordinate system. θ represents the angle between the d-axis and the α-axis, which is the electrical angle of the motor.

[0029] S103 , the controller performs PI regulation on the current in the two-phase rotating coordinate system to obtain a target current, and calculates the voltage in the two-phase rotating coordinate system of the motor based on the target current.

[0030] In an embodiment of the present invention, the controller performs PI regulation on the current in the two-phase rotating coordinate system to obtain the target current, which can be specifically:

[0031] The controller performs a proportional-integral operation on the error between the actual value of the current and the expected value, and the PI regulator calculates the target current based on the error.

[0032] i d =K p_d *ΔI d +K i_d*∫ΔI d dt

[0033] i q =K p_q *ΔI q +K i_q *∫ΔI q dt

[0034] Among them, K p_d and K p_q Used to determine the dynamic response speed, it is necessary to match the inductance and bandwidth, K i_d and K i_q To eliminate steady-state errors, matching resistance and inductance is required, ΔI d and ΔI q They represent the actual value of the d-axis current I in the two-phase rotating coordinate system of the motor. d The error from the expected value and the actual value of the q-axis current I q The error from the expected value reflects the deviation of the control target and is the input signal of the PI regulator, ∫ΔI d dt and ∫ΔI q dt represents the accumulation of historical errors, i d and i q They represent the d-axis current and q-axis current generated after PI regulation.

[0035] According to the motor's voltage equation, to control the current, the voltage must be adjusted so that the current follows the desired trajectory. In steady-state operation, the inductance term is omitted, meaning that the derivative of the current is directly related to the voltage, meaning that the voltage determines the rate of change of the current. To achieve precise current tracking, the voltage must be adjusted to control the current's dynamic response.

[0036] The voltage of the motor in the two-phase rotating coordinate system calculated according to the target current can be specifically:

[0037]

[0038] Among them, u d 、u q They represent the d-axis and q-axis voltages of the motor in the two-phase rotating coordinate system, namely the dq coordinate system, Rs represents the stator resistance of the motor, and L d , L q They represent the d-axis inductance and q-axis inductance respectively, Represents the time derivative, the physical essence is to reveal the instantaneous characteristics of the quantity changing with time, w e Indicates the motor speed. Indicates the motor flux constant.

[0039] S104, the controller performs an inverse Park transform on the voltage of the two-phase rotating coordinate system of the motor and converts it back to the voltage of the two-phase stationary coordinate system;

[0040] The inverse Park transform formula is: Among them, U α 、U β They represent the α-axis and β-axis voltages of the motor in the two-phase stationary coordinate system respectively.

[0041] S105 , the controller performs feedforward decoupling on the voltage of the motor in the two-phase rotating coordinate system.

[0042] S105 may specifically be: subtracting the voltage term caused by the q-axis current mutual inductance from the d-axis voltage, and subtracting the voltage term caused by the d-axis current mutual inductance from the q-axis voltage.

[0043] according to It can be seen that due to U d Contains the voltage term caused by the q-axis current mutual inductance, U q Including the voltage term caused by the d-axis current mutual inductance, so the U output of the PI control d and U q Based on this, the corresponding coupling terms are subtracted.

[0044] Since feedforward decoupling is used on the basis of the original current loop, the mutual coupling between the d-axis voltage and the q-axis voltage generated by the mutual inductance is avoided, thereby improving the control efficiency.

[0045] S106 : The controller generates an SPWM signal based on mean-value zero-sequence injection to drive the power driver.

[0046] The controller generates the SPWM signal based on mean value zero sequence injection specifically as follows:

[0047] Injecting the zero-sequence voltage component into the modulation wave signal, the modulation wave expression is:

[0048] V com =0.5*(V max +V min )

[0049] V am =V a_pu -V com

[0050] V bm =V b_pu -V com

[0051] V cm =V c_pu -V com

[0052] Among them, |Vam 、V bm 、V cm They are saddle waves obtained by modulating the original three-phase voltage as a carrier; |V a_pu 、V b_pu 、V c_pu They are three-phase reference voltage, V com The zero-sequence voltage component is the average of the three-phase voltages. After adding it, the amplitude of the modulated wave can be symmetrically distributed within the carrier range.

[0053] By injecting a zero-sequence voltage component (i.e., mean value component), the SPWM modulation effect is optimized, the DC bus voltage utilization rate is increased, and the three-phase voltage symmetry is maintained. Adding the same zero-sequence voltage component to the original three-phase sinusoidal modulation wave reduces the peak value of the modulation wave, thereby outputting a higher equivalent voltage without overmodulation.

[0054] The SPWM based on mean zero-sequence injection achieves the same waveform as the SVPWM achieved by the traditional sector judgment method, but the SPWM using mean zero-sequence injection has less harmonic content, greatly reduces the amount of calculation, and shortens the calculation time.

[0055] Figure 2 This diagram shows the effects of mean zero-sequence injection. A saddle wave can be formed by superimposing a sawtooth signal on a sine wave signal. This improves voltage utilization while meeting the inverter's maximum phase voltage peak.

[0056] See also Figure 3 The motor drive system for a UAV based on magnetic field orientation provided by an embodiment of the present invention includes a controller 11, a motor 12, and a power driver 13 and a sampling circuit 14 electrically connected to the controller 11 respectively. The power driver 13 is also electrically connected to the motor 12 and the sampling circuit 14 respectively. The controller 11 uses the motor drive method for a UAV based on magnetic field orientation provided by an embodiment of the present invention to control the motor. After the mean zero-sequence injection SPWM calculation is performed, the controller 11 controls the three complementary PWM signals through the power driver 13 to control the voltage saddle waves at the output ends of the three pairs of MOS tubes to be supplied to the motor.

[0057] In the embodiment of the present invention, the controller 11 may be a digital signal processor (DSP) or a microcontroller unit (MCU).

[0058] An embodiment of the present invention further provides a UAV based on magnetic field orientation, including a motor drive system for the UAV based on magnetic field orientation provided by an embodiment of the present invention.

[0059] In the embodiment of the present invention, since feedforward decoupling is used on the basis of the original current loop, the mutual coupling of the d-axis voltage and the q-axis voltage generated by the mutual inductance is avoided, thereby improving the control efficiency. In addition, since the present application optimizes the modulation effect of SPWM by injecting a zero-sequence voltage component (i.e., a mean component), the utilization rate of the DC bus voltage is improved, and the symmetry of the three-phase voltage is maintained. The same zero-sequence voltage component is added to the original three-phase sinusoidal modulation wave to reduce the peak value of the modulation wave, thereby outputting a higher equivalent voltage without over-modulation. The SPWM based on mean zero-sequence injection realizes the same waveform as the SVPWM realized by the traditional sector judgment method, but the SPWM using mean zero-sequence injection has less harmonic content, greatly reduces the amount of calculation, and shortens the calculation time.

[0060] The magnetic field orientation-based drone provided by the embodiments of the present invention is suitable for use as a firefighting drone, improving flight stability, efficiency, and low-speed performance, while reducing noise and vibration. Specifically, the following effects can be achieved:

[0061] High-precision control: The magnetic field orientation algorithm achieves precise control of motor torque and magnetic flux, improving flight stability and ensuring accurate operation of the firefighting drone in complex environments.

[0062] High-efficiency operation: The current waveform of the magnetic field-oriented drive is continuous, and the motor efficiency is significantly improved, which extends the UAV's flight time and meets the needs of long-term firefighting missions.

[0063] Low noise and vibration: SPWM signal based on mean zero-sequence injection reduces noise and vibration, improves the working environment, and is particularly suitable for performing tasks in residential or sensitive areas.

[0064] Strong low-speed performance: Excellent control performance at low speed or in hovering state, ensuring the stability and flexibility of the drone in firefighting or rescue missions.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A motor driving method for a UAV based on magnetic field orientation, characterized in that: The following steps are involved: The controller converts the three-phase current of the motor collected by the sampling circuit into the current in the two-phase stationary coordinate system through Clarke transformation; The controller converts the current in the two-phase stationary coordinate system into the current in the two-phase rotating coordinate system through Park transformation; The controller performs PI regulation on the current in the two-phase rotating coordinate system to obtain the target current, and calculates the voltage in the two-phase rotating coordinate system of the motor based on the target current; The controller performs an inverse Park transform on the voltage of the motor in the two-phase rotating coordinate system and converts it back to the voltage in the two-phase stationary coordinate system; The controller performs feedforward decoupling on the voltage in the two-phase rotating coordinate system of the motor; The controller generates an SPWM signal based on mean-value zero-sequence injection to drive the power driver.

2. The method according to claim 1, wherein The Clarke transformation formula is: Among them, I a , I b , I c They represent the three-phase currents of the motor collected by the sampling circuit in the three-phase stationary coordinate system, i.e., the α-β coordinate system, I α , I β They represent the α-axis and β-axis currents of the motor in the two-phase stationary coordinate system respectively.

3. The method according to claim 2, wherein The Park transformation formula is: Among them, I d , I q They represent the d-axis and q-axis currents of the motor in the two-phase rotating coordinate system, namely the dq coordinate system. θ represents the angle between the d-axis and the α-axis, which is the electrical angle of the motor.

4. The method according to claim 3, wherein The controller performs PI regulation on the current in the two-phase rotating coordinate system to obtain the target current: The controller performs a proportional-integral operation on the error between the actual value of the current and the expected value, and the PI regulator calculates the target current based on the error. i d =K p_d *ΔI d +K i_d *∫ΔI d dt i q =K p_q *ΔI q +K i_q *∫ΔI q dt Among them, K p_d and K p_q Used to determine the dynamic response speed, it is necessary to match the inductance and bandwidth, K i_d and K i_q To eliminate steady-state errors, matching resistance and inductance is required, ΔI d and ΔI q They represent the actual value of the d-axis current I in the two-phase rotating coordinate system of the motor. d The error from the expected value and the actual value of the q-axis current I q The error from the expected value reflects the deviation of the control target and is the input signal of the PI regulator, ∫ΔI d dt and ∫ΔI q dt represents the accumulation of historical errors, i d and i q They represent the d-axis current and q-axis current generated after PI regulation.

5. The method according to claim 4, wherein The voltage of the motor in the two-phase rotating coordinate system is calculated based on the target current as follows: Among them, u d 、u q They represent the d-axis and q-axis voltages of the motor in the two-phase rotating coordinate system, namely the dq coordinate system, R s Indicates the motor stator resistance, L d , L q They represent the d-axis inductance and q-axis inductance respectively, represents the time derivative, w e Indicates the motor speed. Indicates the motor flux constant.

6. The method according to claim 5, wherein The inverse Park transform formula is: Among them, U α 、U β They represent the α-axis and β-axis voltages of the motor in the two-phase stationary coordinate system respectively.

7. The method according to claim 5, wherein The controller performs feedforward decoupling on the voltage in the two-phase rotating coordinate system of the motor by subtracting the voltage term caused by the q-axis current mutual inductance from the d-axis voltage and subtracting the voltage term caused by the d-axis current mutual inductance from the q-axis voltage.

8. The method according to claim 1, wherein The controller generates the SPWM signal based on mean value zero sequence injection specifically as follows: Injecting the zero-sequence voltage component into the modulation wave signal, the modulation wave expression is: V com =0.5*(V max+ V min ) V am =V a_pu -V com V bm =V b_pu -V com V cm =V c_pu -V com Among them, V am 、V bm 、V cm They are saddle waves modulated with the original three-phase voltage as the carrier; V a_pu 、V b_pu 、V c_pu They are the three-phase reference voltage, the zero-sequence voltage component is the mean of the three-phase voltage.

9. A motor drive system for a UAV based on magnetic field orientation, characterized in that: The invention comprises a controller, a motor, and a power driver and a sampling circuit electrically connected to the controller respectively. The power driver is also electrically connected to the motor and the sampling circuit respectively. The controller controls the motor by adopting the motor driving method of the UAV based on magnetic field orientation as described in any one of claims 1 to 8. After the mean zero-sequence injection SPWM calculation, the controller controls the three complementary PWM signals through the power driver to control the voltage saddle waves at the output ends of the three pairs of MOS tubes to be given to the motor.

10. A UAV based on magnetic field orientation, characterized in that: The motor drive system of the UAV based on magnetic field orientation is included as claimed in claim 9.

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