Swash-plate-free variable pitch method and system for high-precision and low-energy-consumption miniature unmanned helicopter

Abstract

The invention discloses a high-precision and low-energy-consumption micro unmanned helicopter swash-plate-free variable pitch method and system, and relates to the field of unmanned aerial vehicle control, and the method comprises the steps: outputting a q-axis current reference value and a d-axis current reference value according to a d-q-axis current component and the real-time speed of motor operation; decoupling the output of the d-axis current controller and the output of the q-axis current controller based on the motor parameters to generate a decoupling voltage reference value; a variable pitch reference voltage amplitude and a phase are calculated through a pitch-voltage resolving unit according to a variable pitch instruction, and a sine injection voltage during variable pitch is calculated; superposing the decoupling voltage reference value and the sine injection voltage with the sine injection voltage to obtain a reference voltage of a d-q axis; based on the reference voltage of the d-q axis, an alpha-beta axis voltage is obtained through inverse Park conversion, and a three-phase PWM wave is generated through an SVPWM module. According to the invention, the control precision of the cyclic change of the motor speed required by variable pitch and the operation efficiency of the driving motor can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of unmanned aerial vehicle (UAV) control technology, and in particular to a high-precision, low-energy-consumption micro unmanned helicopter pitch control method and system without swashplate. Background Technology

[0002] With the rapid development of drone technology, micro unmanned helicopters have shown great potential in complex application scenarios due to their vertical takeoff and landing and hovering capabilities. However, the attitude adjustment of traditional micro unmanned helicopters often relies on complex swashplate structures, which limits their performance improvement and miniaturization. In recent years, swashplate-less underactuated rotor structures have gradually become a research hotspot. By using the cyclic acceleration and deceleration of the rotor drive motor within the mechanical cycle, the thrust direction can be controlled, thereby simplifying the mechanical structure and improving maneuverability. However, current main drive motors mostly use square wave control methods, which is inconsistent with the current trend of motor applications dominated by sinusoidal back EMF waveforms. This leads to increased torque ripple and reduced efficiency, which has an adverse effect on energy-sensitive micro unmanned helicopters. Summary of the Invention

[0003] The purpose of this application is to provide a high-precision, low-energy-consumption method and system for swashplate-free pitch control of a micro unmanned helicopter, which can effectively improve the control accuracy of the cyclic change of motor speed required for pitch control and the operating efficiency of the drive motor.

[0004] To achieve the above objectives, this application provides the following solution: Firstly, this application provides a high-precision, low-energy-consumption method for swashplate-free pitch control of a micro unmanned helicopter, including: Collect the three-phase stator current and real-time position of the motor; Based on the three-phase stator current of the motor, the Clarke-Park transformation is used to obtain the dq-axis current components; Based on the real-time position of the motor, the real-time speed of the motor is calculated through position differentiation and low-pass filtering. Based on the dq axis current components and the real-time speed of the motor, the q axis current reference value is output using the FOC speed outer loop controller, and the d axis current reference value is generated using the MTPA strategy. The outputs of the d-axis current controller and the q-axis current controller are decoupled based on motor parameters to generate a decoupling voltage reference value; the input of the d-axis current controller is the difference between the d-axis current reference value and the d-axis current component; the input of the q-axis current controller is the difference between the q-axis current reference value and the q-axis current component. When pitch adjustment is required, the pitch command is used to calculate the pitch reference voltage amplitude and phase through the pitch-voltage calculation unit. Based on the current motor rotation position and the amplitude and phase of the pitch reference voltage, the sinusoidal injection voltage during pitch adjustment is calculated. The reference voltage for the decoupling voltage is superimposed on the sinusoidal injection voltage to obtain the reference voltage for the dq axis; Based on the reference voltage of the dq axis, the α-β axis voltages are obtained by inverse Park transformation, and a three-phase PWM wave is generated by the SVPWM module. The three-phase PWM wave is used to control the torque and speed of the drive motor. The drive motor is used to drive the swashplate-less rotor structure to perform lead-lag motion, thereby changing the rotor surface tilt angle.

[0005] Optionally, the FOC speed outer loop controller includes: a speed PI controller and a current PI controller; the input of the speed PI controller is the difference between the real-time speed of the motor and a given reference speed signal; the output of the speed PI controller is a q-axis current reference value; the input of the current PI controller is the difference between the q-axis current reference value and the q-axis current component in the dq-axis current component.

[0006] Optionally, based on the reference voltage of the dq axis, the α-β axis voltages are obtained using the inverse Park transform, and a three-phase PWM wave is generated through the SVPWM module, specifically including: When pitch control is not required, the reference voltage of the dq axis is inversely Park-transformed and then input to the SVPWM module. The SVPWM module outputs a PWM control signal to control the three-phase two-level inverter circuit and drive the motor to rotate at a constant speed, generating a smoothly rotating blade to achieve vertical upward thrust.

[0007] Optionally, based on the reference voltage of the dq axis, the α-β axis voltages are obtained using the inverse Park transform, and a three-phase PWM wave is generated through the SVPWM module, specifically including: Based on the current motor rotation position and the amplitude and phase of the pitch reference voltage, the sinusoidal injection voltage of the q-axis during pitch is calculated; The q-axis voltage reference value is obtained by superimposing the sinusoidal injection voltage on the q-axis and the output value of the decoupled current PI controller. Based on the reference voltage along the dq axis, the inverse Park transformation is used to obtain the voltage reference value in the stationary coordinate system α-β. Based on the voltage reference value of the stationary coordinate system α-β, the SVPWM module calculates the PWM drive motor to cyclically change speed within one mechanical rotation cycle, driving the swashplate-less rotor structure to produce lead-lag motion, thus completing the change of the rotor surface tilt angle.

[0008] Optionally, the formula for calculating the sinusoidal injection voltage is: ; In the formula, U m U is the amplitude of the sinusoidal injection voltage. mThe magnitude of θ is directly proportional to the angle δ of the paddle surface tilt. m ψ represents the real-time position of the motor, and ψ represents the phase of the sinusoidal injected voltage.

[0009] Secondly, this application provides a high-precision, low-energy-consumption micro unmanned helicopter swashplate-free pitch control system, comprising: The data acquisition module is used to acquire the three-phase stator current of the motor and the real-time position of the motor. The conversion module is used to obtain the dq-axis current components based on the three-phase stator current of the motor using Clarke-Park transformation; The speed calculation module is used to calculate the real-time speed of the motor based on its real-time position, through position differentiation and low-pass filtering. The current calculation module is used to output the q-axis current reference value based on the dq-axis current components and the real-time speed of the motor, and to generate the d-axis current reference value using the MTPA strategy. The voltage calculation module is used to decouple the outputs of the d-axis current controller and the q-axis current controller based on motor parameters, and generate a decoupled voltage reference value; the input of the d-axis current controller is the difference between the d-axis current reference value and the d-axis current component; the input of the q-axis current controller is the difference between the q-axis current reference value and the q-axis current component. The pitch-voltage calculation module is used to calculate the pitch reference voltage amplitude and phase when pitch adjustment is required. The sinusoidal voltage calculation module is used to calculate the sinusoidal injection voltage during pitch control based on the current motor rotation position and the amplitude and phase of the pitch reference voltage. The superposition module is used to superimpose the decoupling voltage reference value and the sinusoidal injection voltage to obtain the dq axis reference voltage; The drive module is used to obtain the α-β axis voltages based on the dq axis reference voltage using inverse Park transformation, and generates a three-phase PWM wave through the SVPWM module. The three-phase PWM wave is used to control the torque and speed of the drive motor. The drive motor is used to drive the swashplate-less rotor structure to perform lead-lag motion, thereby changing the rotor surface tilt angle.

[0010] Optionally, the FOC speed outer loop controller includes: a speed PI controller and a current PI controller; the input of the speed PI controller is the difference between the real-time speed of the motor and a given reference speed signal; the output of the speed PI controller is a q-axis current reference value; the input of the current PI controller is the difference between the q-axis current reference value and the q-axis current component in the dq-axis current component.

[0011] Optionally, the driving module specifically includes: The first transformation unit is used to perform an inverse Park transformation on the reference voltage of the dq axis and input it to the SVPWM module when pitch is not required. The constant speed rotation unit is used to output PWM control signals based on the SVPWM module to control the three-phase two-level inverter circuit and drive the motor to rotate at a constant speed, generating a smoothly rotating blade surface to achieve vertical upward thrust.

[0012] Optionally, the driving module specifically includes: The sinusoidal injection voltage unit is used to calculate the sinusoidal injection voltage of the q-axis during pitch control based on the current rotational position of the motor and the amplitude and phase of the pitch reference voltage. The reference voltage calculation unit is used to superimpose the sinusoidal injection voltage based on the q-axis and the output value of the decoupled current PI controller to obtain the q-axis voltage reference value; The second transformation unit is used for the reference voltage based on the dq axis. It uses the inverse Park transformation to obtain the voltage reference value in the stationary coordinate system α-β. The rotating unit, based on the voltage reference value of the stationary coordinate system α-β, calculates the PWM drive motor through the SVPWM module to cyclically change speed within one mechanical rotation cycle, driving the swashplate-less rotor structure to produce lead-lag motion, thus completing the change of the rotor surface tilt angle.

[0013] Optionally, the formula for calculating the sinusoidal injection voltage is: ; In the formula, U m U is the amplitude of the sinusoidal injection voltage. m The magnitude of θ is directly proportional to the angle δ of the paddle surface tilt. m ψ represents the real-time position of the motor, and ψ represents the phase of the sinusoidal injected voltage.

[0014] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides a high-precision, low-energy-consumption method and system for swashplate-free pitch control of a micro unmanned helicopter. First, it employs Clarke-Park transformation to convert the three-phase stator current of the motor into dq-axis current components, realizing the conversion of current from a three-phase stationary coordinate system to a two-phase rotating coordinate system, facilitating precise motor control. Second, based on the motor's real-time position, the real-time speed of the motor is calculated through position differentiation and low-pass filtering, ensuring the accuracy and real-time nature of the speed information. Then, based on the dq-axis current components and the motor's real-time speed, the FOC speed outer loop controller outputs a q-axis current reference value, and an MTPA strategy is used to generate a d-axis current reference value. This minimizes current consumption while ensuring output torque, thereby improving the motor's drive efficiency. Finally, by decoupling the outputs of the d-axis current controller and the q-axis current controller, a decoupling voltage reference value is generated. This eliminates the mutual influence between the d-axis and q-axis currents, improving the accuracy and stability of current control. When pitch adjustment is required, this application calculates the amplitude and phase of the pitch reference voltage using a pitch-voltage calculation unit. Based on the current motor rotation position and the amplitude and phase of the pitch reference voltage, a sinusoidal injection voltage is calculated for pitch adjustment. The introduction of the sinusoidal injection voltage enables fine-tuning of motor torque and speed, thereby improving the accuracy of pitch control. Finally, the decoupling voltage reference value is superimposed with the sinusoidal injection voltage to obtain the dq-axis reference voltage. The α-β-axis voltages are then obtained through inverse Park transform, and a three-phase PWM wave is generated using the SVPWM module to control the torque and speed of the drive motor. This achieves precise generation and control of the motor drive signal, thereby improving the motor's drive efficiency and response speed. By combining the dq-axis sinusoidal injection voltage drive with pitch speed regulation, this application achieves precise control of motor torque and speed, improving the control accuracy and drive efficiency of cyclic motor speed changes. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating a high-precision, low-energy micro unmanned helicopter pitch-shifting method without swashplate, provided as an embodiment of this application.

[0017] Figure 2 This application provides a reference example of an electric drive system for a micro unmanned aerial vehicle (UAV) according to one embodiment.

[0018] Figure 3The diagram illustrates some pitch definition features provided for one embodiment of this application.

[0019] Figure 4 A control strategy diagram provided for an embodiment of this application.

[0020] Figure 5 The transfer function block diagram is provided for a pitching method according to an embodiment of this application.

[0021] Figure 6 The closed-loop spectrum Bode plot of the transfer function of the swashplate-free pitch method provided in one embodiment of this application.

[0022] Figure label: Blade—1; Lead-lag hinge—2; Paddle tilt hinge—3; Paddle hub—4; Brushless DC motor—5; Motor position acquisition circuit board—6; Motor coordinate system—7; Stable paddle surface—8; Tilted paddle surface—9. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] Unmanned aerial vehicles (UAVs), also known as drones, have seen rapid advancements in microprocessor, sensor, and navigation technologies, along with improvements in equipment performance and reductions in size and weight. These advancements have significantly driven the miniaturization and micro-miniaturization of UAVs. Micro unmanned helicopters, a branch of micro UAVs, possess vertical takeoff and landing capabilities and the ability to hover at designated locations, demonstrating excellent performance even in relatively complex application scenarios.

[0025] The widespread application of micro unmanned helicopters has also placed higher demands on their performance. Attitude adjustment and drive systems, as crucial components of micro unmanned helicopter systems, significantly impact the stability, maneuverability, and reliability of micro unmanned aerial vehicles (UAVs). Traditional attitude adjustment structures for micro UAVs often require complex swashplate structures. Paulos from the University of Pennsylvania published a paper titled "Flight performance of a swashplateless microair vehicle" at the 2015 IEEE International Conference on Robotics and Automation (ICRA), proposing a special swashplate-less underactuated rotor structure. This structure utilizes the cyclic acceleration and deceleration of the rotor's drive motor at a designated mechanical position within one mechanical cycle, causing the rotor blades to advance and lag, thereby changing the tilt angle of the rotating blade surface, altering the thrust direction, and ultimately achieving attitude adjustment. However, the control of the main drive motor still employs a relatively simple square wave control method. Given the current trend of UAV motors primarily using sinusoidal back-EMF waveforms, square wave control introduces torque ripple, affecting pitch performance. In addition, its efficiency is not as good as Magnetic Field Oriented Control (FOC), which has a significant impact on energy-sensitive micro unmanned helicopters.

[0026] The purpose of this application is to provide a high-precision, low-energy-consumption method and system for swashplate-free pitch control of a micro unmanned helicopter, which can effectively improve the control accuracy of the cyclic change of motor speed required for pitch control and the operating efficiency of the drive motor.

[0027] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1 like Figure 1 As shown, this embodiment provides a high-precision, low-energy micro unmanned helicopter pitch control method without swashplate, including: Step 101: Collect the three-phase stator current of the motor and the real-time position of the motor; Step 102: Based on the three-phase stator current of the motor, the Clarke-Park transformation is used to obtain the dq-axis current components; Step 103: Based on the real-time position of the motor, calculate the real-time speed of the motor through position differentiation and low-pass filtering; Step 104: Based on the dq axis current components and the real-time speed of the motor, output the q axis current reference value based on the FOC speed outer loop controller, and generate the d axis current reference value using the MTPA strategy. Step 105: Decouple the outputs of the d-axis current controller and the q-axis current controller based on the motor parameters to generate a decoupling voltage reference value; the input of the d-axis current controller is the difference between the d-axis current reference value and the d-axis current component; the input of the q-axis current controller is the difference between the q-axis current reference value and the q-axis current component. Step 106: When pitch adjustment is required, the pitch command calculates the pitch reference voltage amplitude and phase through the pitch-voltage calculation unit; Step 107: Calculate the sinusoidal injection voltage during pitch control based on the current motor rotation position and the amplitude and phase of the pitch reference voltage; Step 108: Superimpose the decoupling voltage reference value with the sinusoidal injection voltage to obtain the dq axis reference voltage; Step 109: Based on the reference voltage of the dq axis, the α-β axis voltage is obtained by inverse Park transformation, and a three-phase PWM wave is generated by the SVPWM module; the three-phase PWM wave is used to control the torque and speed of the drive motor; the drive motor is used to drive the swashplate-less rotor structure to perform lead-lag motion, thereby changing the rotor surface tilt angle.

[0029] In some embodiments, when performing steps 101-109, such as Figure 4 The overall control strategy diagram can be shown as follows: Through current sensor and Figure 2 The motor position acquisition circuit board 6 collects the stator current and real-time position of the brushless motor and the swashplate-less pitch rotor, and sends them to the microprocessor. The acquired mechanical angles are converted into electrical angles according to the number of pole pairs of the drive motor, and the stator currents are sequentially subjected to Clarke and Park transformations to obtain the components of the three-phase stator currents in the dq rotating coordinate system.

[0030] The real-time speed of the motor is obtained by calculating the differential angle obtained from the magnetic encoder and performing a simple low-pass filter. The difference between this speed and the given reference speed signal is used to obtain the error signal, which is then used as the input to the speed PI controller in the FOC speed outer loop controller.

[0031] The output of the controller is subtracted from the acquired and transformed q-axis feedback current to obtain the input of the q-axis motor controller. The d-axis current reference value is calculated using the maximum torque per ampere (MTPA) strategy, and the difference between this value and the d-axis current is obtained to obtain the input of the d-axis current PI controller.

[0032] Specifically, the rotational speed reference value of the FOC algorithm speed-current dual loop used in this application should be obtained from the expected average thrust of the UAV. The difference between the calculated real-time speed and the speed reference value is used as the input of the speed PI controller for outer loop control calculation to obtain the expected q-axis current reference value. The corresponding d-axis current reference value is obtained through the MTPA strategy and the difference between the current reference value and the acquired and transformed current is used as the input of the current PI controller.

[0033] By decoupling the dq-axis voltage reference value from the output dq-axis current controller in step two using the motor parameters (resistance, inductance, flux linkage) and the real-time electrical speed of the drive motor, the reference value of the dq-axis voltage is obtained. After performing an inverse Park transformation, the voltage reference value of the stationary coordinate system α-β is obtained.

[0034] The calculated voltage reference values ​​of α-β are used as input to the SVPWM space vector modulation module. The conduction time of the three-phase PWM is sent to the microprocessor (MCU) to obtain three complementary drive PWM waves, which drive the three-phase bridge drive circuit on the UAV's electronic speed controller to generate the required rotating voltage vector, thereby controlling the torque and speed of the drive motor. This drives the swashplate-less rotor structure to operate smoothly and generate vertical thrust.

[0035] Specifically, when pitch control is not required, the inverse Park transform is directly fed into the SVPWM unit (SVPWM space vector modulation unit), and the microprocessor outputs the corresponding PWM control signal to control it. Figure 2 The three-phase two-level inverter circuit drives the motor to achieve constant speed rotation, generating a smoothly rotating blade surface to achieve vertical upward thrust.

[0036] During pitch control, the pitch command calculates the pitch reference voltage amplitude through the pitch-voltage calculation unit. Based on the current motor rotation position of the encoder, the real-time q-axis sinusoidal injection voltage is calculated. This voltage is then superimposed on the decoupled q-axis voltage reference value output by the medium current PI controller. After inverse Park transformation, the voltage reference value of the stationary coordinate system α-β is obtained. The SVPWM space voltage vector modulation module calculates the PWM drive motor to cyclically change speed within one mechanical rotation cycle, driving the swashplate-less rotor structure to produce lead-lag motion, ultimately achieving a change in the pitch angle of the rotor surface.

[0037] Specifically, when pitch control is required, the pitch position should be adjusted according to the desired pitch of the blades. The voltage injected along the q-axis is calculated in real time based on the tilt angle δ. The expression for the sinusoidal injection voltage is: ; In the formula, U m Let θ be the amplitude of the sinusoidal injected voltage, which is proportional to the magnitude of the propeller tilt angle δ.m Let ψ be the real-time position of the motor, and ψ be the phase of the sinusoidal injected voltage. Due to the system's delay effect, the desired blade tilt position is... The phase of the sinusoidal injection voltage is not consistent with that of the voltage; ψ is the result after compensation.

[0038] θ m It can be done Figure 2 The motor position acquisition circuit board 6 in the middle is used to acquire the position, U m The calculation method for ψ is to test the speed, voltage and phase of multiple motors in the entire drive system, record and fit the experimental data and store it in the microprocessor to realize the calculation of the voltage amplitude and phase required for the desired tilt angle and position of the propeller surface.

[0039] All real-time voltage calculations and injections required for pitch control should be performed in the high-frequency control task (current loop) of the microprocessor to ensure the high control resolution required for high-precision pitch control.

[0040] To further demonstrate the advantages of the method proposed in this invention, Figure 5 The block diagram of the motor q-axis transfer function after neglecting the delay term in the control system is shown. In the figure, KIC, KPC and KIS, KPS are the control parameters of the PI controllers of the q-axis current inner loop and speed outer loop, respectively. R and L are the resistance and inductance parameters of the motor, Km is the torque constant of the motor, J is the moment of inertia of the entire rotation system, B is the viscosity coefficient, and s is the Laplace operator.

[0041] The transfer function from the injected disturbance voltage to the motor speed can be obtained from the transfer function block diagram, and the Bode plot of the closed loop can be drawn accordingly. Figure 6 An example of a closed-loop Bode plot of the tuned control parameters was presented. The plot shows that, while ensuring good dynamics and stability of the entire control system, by appropriately adjusting the control parameters, a high closed-loop gain and a low hysteresis angle can be achieved at the frequency corresponding to the motor's rated speed. This reduces other power consumption caused by the sinusoidal injection voltage and achieves higher control precision.

[0042] Specifically, such as Figure 2 As shown, it mainly consists of three parts: 1. a microprocessor; 2. a three-phase bridge drive circuit; and 3. a drive motor and pitch control structure. The acquired position and current signals are fed into the microprocessor for control algorithm calculation, generating drive signals to control the three-phase two-level inverter circuit to control the brushless motor and rotor pitch control.

[0043] in, Figure 3 This demonstrates the process of pitch control without swashplate. A brief introduction to its pitch control principle is provided, along with explanations of the relevant parameters defined during the process: Figure 3In the motor coordinate system 7, its Z-axis points to the motor's rotation axis. When the drive motor rotates at a constant speed, the stable blade surface 8 (the plane of propeller blade rotation) is as follows: Figure 3 As shown, the thrust it generates is vertically upward; when the drive motor accelerates and decelerates cyclically, it is affected by inertia. Figure 2 The lead-lag hinge 2 in the middle undergoes lead-lag motion, changing the pitch of the two blades 1 and generating a thrust difference on the two blades, through... Figure 2 The tilting hinge 3 of the propeller surface realizes the tilting of the propeller disk; the lead-lag hinge 2 is connected to the propeller hub 4, and the propeller hub 4 is set on the brushless DC motor 5. Figure 3 The tilted propeller surface 9 is the tilted propeller surface, and the thrust direction is perpendicular to the propeller surface. After the thrust is decomposed, a horizontal component force is generated, which realizes the adjustment of the UAV's attitude. Figure 3 In this context, δ represents the angle of inclination of the paddle surface. The rotational position at which the blade tilt is desired.

[0044] Example 2 This embodiment provides a high-precision, low-energy-consumption micro unmanned helicopter swashplate-free pitch control system, including: The data acquisition module is used to acquire the three-phase stator current of the motor and the real-time position of the motor. The conversion module is used to obtain the dq-axis current components based on the three-phase stator current of the motor using Clarke-Park transformation; The speed calculation module is used to calculate the real-time speed of the motor based on its real-time position, through position differentiation and low-pass filtering. The current calculation module is used to output the q-axis current reference value based on the dq-axis current components and the real-time speed of the motor, and to generate the d-axis current reference value using the MTPA strategy. The voltage calculation module is used to decouple the outputs of the d-axis current controller and the q-axis current controller based on motor parameters, and generate a decoupled voltage reference value; the input of the d-axis current controller is the difference between the d-axis current reference value and the d-axis current component; the input of the q-axis current controller is the difference between the q-axis current reference value and the q-axis current component. The pitch-voltage calculation module is used to calculate the pitch reference voltage amplitude and phase when pitch adjustment is required. The sinusoidal voltage calculation module is used to calculate the sinusoidal injection voltage during pitch control based on the current motor rotation position and the amplitude and phase of the pitch reference voltage. The superposition module is used to superimpose the decoupling voltage reference value and the sinusoidal injection voltage to obtain the dq axis reference voltage; The drive module is used to obtain the α-β axis voltages based on the dq axis reference voltage using inverse Park transformation, and generates a three-phase PWM wave through the SVPWM module. The three-phase PWM wave is used to control the torque and speed of the drive motor. The drive motor is used to drive the swashplate-less rotor structure to perform lead-lag motion, thereby changing the rotor surface tilt angle.

[0045] The FOC speed outer loop controller includes a speed PI controller and a current PI controller. The input of the speed PI controller is the difference between the real-time speed of the motor and a given reference speed signal. The output of the speed PI controller is a q-axis current reference value. The input of the current PI controller is the difference between the q-axis current reference value and the q-axis current component in the dq-axis current component. The output of the speed PI controller is a d-axis current reference value.

[0046] The driving module specifically includes: The first transformation unit is used to perform an inverse Park transformation on the reference voltage of the dq axis and input it to the SVPWM module when pitch is not required. The constant speed rotation unit is used to output PWM control signals based on the SVPWM module to control the three-phase two-level inverter circuit and drive the motor to rotate at a constant speed, generating a smoothly rotating blade surface to achieve vertical upward thrust.

[0047] The driving module specifically includes: The sinusoidal injection voltage unit is used to calculate the sinusoidal injection voltage of the q-axis during pitch control based on the current rotational position of the motor and the amplitude and phase of the pitch reference voltage. The reference voltage calculation unit is used to superimpose the sinusoidal injection voltage based on the q-axis and the output value of the decoupled current PI controller to obtain the q-axis voltage reference value; The second transformation unit is used for the reference voltage based on the dq axis. It uses the inverse Park transformation to obtain the voltage reference value in the stationary coordinate system α-β. The rotating unit, based on the voltage reference value of the stationary coordinate system α-β, calculates the PWM drive motor through the SVPWM module to cyclically change speed within one mechanical rotation cycle, driving the swashplate-less rotor structure to produce lead-lag motion, thus completing the change of the rotor surface tilt angle.

[0048] The formula for calculating the sinusoidal injection voltage is as follows: ; In the formula, U m U is the amplitude of the sinusoidal injection voltage. m The magnitude of θ is directly proportional to the angle δ of the paddle surface tilt. m ψ represents the real-time position of the motor, and ψ represents the phase of the sinusoidal injected voltage.

[0049] In summary, this application has the following technical effects: This application is implemented based on the basic strategy of field-oriented control (FOC), which can effectively improve efficiency and reduce torque ripple for motors with sinusoidal back EMF that are increasingly common in the current UAV motor market. The sinusoidal voltage injection required for pitch control is achieved in a current loop with a high control frequency. Given the small inductance characteristics of motors used in micro UAVs, their current loop control frequency is often in the tens of kHz. Therefore, the pitch voltage can achieve high control resolution and thus high pitch control accuracy.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A high-precision, low-energy-consumption method for swashplate-free pitch control in a micro unmanned helicopter, characterized in that, include: Collect the three-phase stator current and real-time position of the motor; Based on the three-phase stator current of the motor, the Clarke-Park transformation is used to obtain the dq-axis current components; Based on the real-time position of the motor, the real-time speed of the motor is calculated through position differentiation and low-pass filtering. Based on the dq axis current components and the real-time speed of the motor, the q axis current reference value is output using the FOC speed outer loop controller, and the d axis current reference value is generated using the MTPA strategy. The outputs of the d-axis current controller and the q-axis current controller are decoupled based on motor parameters to generate a decoupling voltage reference value; the input of the d-axis current controller is the difference between the d-axis current reference value and the d-axis current component; the input of the q-axis current controller is the difference between the q-axis current reference value and the q-axis current component. When pitch adjustment is required, the pitch command is used to calculate the pitch reference voltage amplitude and phase through the pitch-voltage calculation unit. Based on the current motor rotation position and the amplitude and phase of the pitch reference voltage, the sinusoidal injection voltage during pitch adjustment is calculated. The reference voltage for the decoupling voltage is superimposed on the sinusoidal injection voltage to obtain the reference voltage for the dq axis; Based on the reference voltage of the dq axis, the α-β axis voltages are obtained by inverse Park transformation, and a three-phase PWM wave is generated by the SVPWM module. The three-phase PWM wave is used to control the torque and speed of the drive motor. The drive motor is used to drive the swashplate-less rotor structure to perform lead-lag motion, thereby changing the rotor surface tilt angle.

2. The method for high-precision, low-energy micro unmanned helicopter pitch control without swashplate according to claim 1, characterized in that, The FOC speed outer loop controller includes a speed PI controller and a current PI controller; the input of the speed PI controller is the difference between the real-time speed of the motor and a given reference speed signal; the output of the speed PI controller is the q-axis current reference value; the input of the current PI controller is the difference between the q-axis current reference value and the q-axis current component in the dq-axis current component.

3. The method for high-precision, low-energy micro unmanned helicopter pitch control without swashplate according to claim 1, characterized in that, Based on the reference voltage along the dq axis, the α-β axis voltages are obtained using the inverse Park transform. A three-phase PWM wave is then generated via the SVPWM module, specifically including: When pitch control is not required, the reference voltage of the dq axis is inversely Park-transformed and then input to the SVPWM module. The SVPWM module outputs a PWM control signal to control the three-phase two-level inverter circuit and drive the motor to rotate at a constant speed, generating a smoothly rotating blade to achieve vertical upward thrust.

4. The method for high-precision, low-energy micro unmanned helicopter pitch control without swashplate according to claim 3, characterized in that, Based on the reference voltage along the dq axis, the α-β axis voltages are obtained using the inverse Park transform. A three-phase PWM wave is then generated via the SVPWM module, specifically including: Based on the current motor rotation position and the amplitude and phase of the pitch reference voltage, the sinusoidal injection voltage of the q-axis during pitch is calculated; The q-axis voltage reference value is obtained by superimposing the sinusoidal injection voltage on the q-axis and the output value of the decoupled current PI controller. Based on the reference voltage along the dq axis, the inverse Park transformation is used to obtain the voltage reference value in the stationary coordinate system α-β. Based on the voltage reference value of the stationary coordinate system α-β, the SVPWM module calculates the PWM drive motor to cyclically change speed within one mechanical rotation cycle, driving the swashplate-less rotor structure to produce lead-lag motion, thus completing the change of the rotor surface tilt angle.

5. The method for high-precision, low-energy micro unmanned helicopter pitch control without swashplate according to claim 1, characterized in that, The formula for calculating the sinusoidal injection voltage is: ； In the formula, U m U is the amplitude of the sinusoidal injection voltage. m The magnitude of θ is directly proportional to the angle δ of the paddle surface tilt. m ψ represents the real-time position of the motor, and ψ represents the phase of the sinusoidal injected voltage.

6. A high-precision, low-energy-consumption micro unmanned helicopter swashplate-free pitch control system, characterized in that, include: The data acquisition module is used to acquire the three-phase stator current of the motor and the real-time position of the motor. The conversion module is used to obtain the dq-axis current components based on the three-phase stator current of the motor using Clarke-Park transformation; The speed calculation module is used to calculate the real-time speed of the motor based on its real-time position, through position differentiation and low-pass filtering. The current calculation module is used to output the q-axis current reference value based on the dq-axis current components and the real-time speed of the motor, and to generate the d-axis current reference value using the MTPA strategy. The voltage calculation module is used to decouple the outputs of the d-axis current controller and the q-axis current controller based on motor parameters, and generate a decoupled voltage reference value; the input of the d-axis current controller is the difference between the d-axis current reference value and the d-axis current component; the input of the q-axis current controller is the difference between the q-axis current reference value and the q-axis current component. The pitch-voltage calculation module is used to calculate the pitch reference voltage amplitude and phase when pitch adjustment is required. The sinusoidal voltage calculation module is used to calculate the sinusoidal injection voltage during pitch control based on the current motor rotation position and the amplitude and phase of the pitch reference voltage. The superposition module is used to superimpose the decoupling voltage reference value and the sinusoidal injection voltage to obtain the dq axis reference voltage; The drive module is used to obtain the α-β axis voltages based on the dq axis reference voltage using inverse Park transformation, and generates a three-phase PWM wave through the SVPWM module. The three-phase PWM wave is used to control the torque and speed of the drive motor. The drive motor is used to drive the swashplate-less rotor structure to perform lead-lag motion, thereby changing the rotor surface tilt angle.

7. The high-precision, low-energy micro unmanned helicopter swashplate-free pitch control system according to claim 6, characterized in that, The FOC speed outer loop controller includes a speed PI controller and a current PI controller; the input of the speed PI controller is the difference between the real-time speed of the motor and a given reference speed signal; the output of the speed PI controller is the q-axis current reference value; the input of the current PI controller is the difference between the q-axis current reference value and the q-axis current component in the dq-axis current component.

8. The high-precision, low-energy micro unmanned helicopter swashplate-free pitch control system according to claim 6, characterized in that, The driving module specifically includes: The first transformation unit is used to perform an inverse Park transformation on the reference voltage of the dq axis and input it to the SVPWM module when pitch is not required. The constant speed rotation unit is used to output PWM control signals based on the SVPWM module to control the three-phase two-level inverter circuit and drive the motor to rotate at a constant speed, generating a smoothly rotating blade surface to achieve vertical upward thrust.

9. A high-precision, low-energy micro unmanned helicopter swashplate-free pitch control system according to claim 6, characterized in that, The driving module specifically includes: The sinusoidal injection voltage unit is used to calculate the sinusoidal injection voltage of the q-axis during pitch control based on the current rotational position of the motor and the amplitude and phase of the pitch reference voltage. The reference voltage calculation unit is used to superimpose the sinusoidal injection voltage based on the q-axis and the output value of the decoupled current PI controller to obtain the q-axis voltage reference value; The second transformation unit is used for the reference voltage based on the dq axis. It uses the inverse Park transformation to obtain the voltage reference value in the stationary coordinate system α-β. The rotating unit, based on the voltage reference value of the stationary coordinate system α-β, calculates the PWM drive motor through the SVPWM module to cyclically change speed within one mechanical rotation cycle, driving the swashplate-less rotor structure to produce lead-lag motion, thus completing the change of the rotor surface tilt angle.

10. A high-precision, low-energy micro unmanned helicopter swashplate-free pitch control system according to claim 6, characterized in that, The formula for calculating the sinusoidal injection voltage is as follows: ； In the formula, U m U is the amplitude of the sinusoidal injection voltage. m The magnitude of θ is directly proportional to the angle δ of the paddle surface tilt. m ψ represents the real-time position of the motor, and ψ represents the phase of the sinusoidal injected voltage.

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