Control method of extended-range vertical take-off and landing fixed-wing unmanned aerial vehicle

Abstract

The invention discloses a control method for an extended-range vertical take-off and landing fixed-wing unmanned aerial vehicle based on a fuel cell, and the method comprises the steps: starting self-inspection of the whole vehicle; voltage and electric quantity of the lithium battery and the super capacitor module are collected, pressure of the hydrogen cylinder is collected, and whether a take-off state is met or not is judged by the FCU control system according to the voltage and electric quantity and the pressure of the hydrogen cylinder; if the take-off state is met, an FCU control system starts a fuel cell to charge a super capacitor module through a DC-DC voltage stabilization module, when the charging amount reaches a first preset charging threshold value, the FCU control system controls the DC-DC voltage stabilization module to reduce the output current of the DC-DC voltage stabilization module, and charging is stopped until the charging amount reaches a second preset charging threshold value; and the real-time flight state is sent to the FCU control system, and then the FCU control system dynamically distributes each power supply output proportion according to the power supply demand of the real-time flight state. The contradiction between the high-power requirement in the vertical take-off and landing stage and the slow dynamic response of the fuel cell is solved through the hierarchical power distribution strategy, the lithium battery is effectively prevented from being over-discharged and over-charged, and the service life of the lithium battery is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy UAVs, and in particular to a control method for a hydrogen fuel cell-based extended-range vertical take-off and landing fixed-wing UAV. Background Art

[0002] With the opening of low-altitude economic policies, the application of drones has flourished across various industries, and market demand continues to drive technological innovation. However, the current power system control strategies for extended-range vertical take-off and landing (ERVTOL) fixed-wing drones still have many shortcomings. Fuel cells have a dynamic response delay exceeding one second, making them unable to meet the transient power surges required during ERVTOL, which requires full power output within 0.5 seconds. Furthermore, lithium-ion battery-assisted solutions are prone to over-discharge and over-charging, resulting in a reduction in cycle life. These issues severely limit the performance and application scope of ERVTOL fixed-wing drones. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a control method for an extended-range vertical take-off and landing fixed-wing UAV based on a hydrogen fuel cell. The hierarchical power allocation strategy solves the contradiction between the high power demand in the vertical take-off and landing stage and the slow dynamic response of the fuel cell, and effectively avoids over-discharge and over-charge of the lithium battery, thereby extending the life of the lithium battery.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A control method for a fuel cell-based extended-range vertical take-off and landing fixed-wing UAV, the UAV comprising a hydrogen cylinder for providing hydrogen, a fuel cell for generating electrical energy using the hydrogen provided by the hydrogen cylinder, a DC-DC voltage regulator module for stabilizing and transforming the electrical energy generated by the fuel cell for output, a supercapacitor module for receiving electrical energy from the DC-DC voltage regulator module and then providing electrical energy to the UAV to support take-off and landing of the UAV, a lithium battery for receiving electrical energy from the DC-DC voltage regulator module and then providing electrical energy to the UAV to support level flight or take-off and landing of the UAV, a level flight motor electronic regulator for utilizing the electrical energy of the lithium battery or the DC-DC voltage regulator module and providing the power required for level flight of the UAV, a rotor take-off and landing motor electronic regulator for utilizing the electrical energy of the lithium battery or the supercapacitor module to achieve the power required for take-off and landing of the UAV, an FCU control system for real-time acquisition of operating data of the lithium battery, supercapacitor module, fuel cell, and DC-DC voltage regulator module, and a flight controller for controlling the flight attitude and flight trajectory of the UAV according to instructions of the FCU control system. The control method for the UAV comprises the following steps:

[0006] The drone is powered on and the whole machine starts self-test to check whether all components are working properly;

[0007] The flight control system collects the voltage and power of the lithium battery and supercapacitor module, and the FCU control system collects the pressure of the hydrogen tank. The FCU control system then determines whether the takeoff state is met based on the voltage and power and the hydrogen tank pressure.

[0008] If the takeoff state is met, the FCU control system starts the fuel cell to charge the supercapacitor module through the DC-DC voltage regulator module. When the charge level of the supercapacitor module reaches a first preset charge threshold, the FCU control system controls the DC-DC voltage regulator module to reduce its output current until the charge level of the supercapacitor module reaches a second preset charge threshold, at which point charging stops.

[0009] The flight controller sends the real-time flight status to the FCU control system, which then dynamically allocates the power output ratio of the lithium-ion battery, supercapacitor module and fuel cell according to the power supply requirements of the real-time flight status to meet the different power requirements of the drone under different flight conditions.

[0010] Furthermore, when the UAV is in the take-off and landing state, the flight control sends a command to turn on the power switch of the supercapacitor module. The supercapacitor module and the lithium battery are powered in parallel at the same time. The supercapacitor module provides the instantaneous power requirement when the maximum take-off weight is required. Then the flight control sends a take-off and landing command to the rotor take-off and landing motor electronic controller to realize take-off. When the UAV takes off vertically to the required hovering height, the FCU control system detects the voltage of the lithium battery in real time, and the FCU control system controls the fuel cell voltage and automatically adjusts the charging current according to the set current multiple after stabilizing the voltage, and controls the start and stop charging of the lithium battery.

[0011] Furthermore, when the UAV transitions from a hovering state to a fixed-wing level flight state, the flight control controls the UAV to switch from the rotor take-off and landing motor electronic regulator to the level flight motor electronic regulator working state. At the same time, the flight control sends a command to disconnect the power switch of the supercapacitor module. Then the FCU control system controls the output voltage of the fuel cell regulated power supply to be consistent with the voltage of the lithium battery. The entire circuit of the UAV is in a state of parallel power supply of the fuel cell regulated power supply and the lithium battery.

[0012] Furthermore, when the UAV is in a level flight cruising state, the flight control controls the UAV to switch from the rotor take-off and landing motor electronic regulator to the level flight motor electronic regulator working state. At this time, the UAV's entire circuit is in a parallel power supply state of the fuel cell regulated power supply and the lithium battery, and during the parallel power supply process, the fuel cell bears 95% of the UAV's power consumption.

[0013] Furthermore, when the UAV is in a level flight cruising state, the output power P_fc of the fuel cell is adjusted by the fuzzy controller.

[0014] P_fc=η·(P_load-K·dP_load / dt)

[0015] Where η is the efficiency optimization coefficient, K is the load change rate compensation weight, P_load is the total load power, dP_load is the power change, and dt is the time.

[0016] Furthermore, during cruising, the FCU controls the fuel cell's regulated power supply to charge the lithium battery and supercapacitor module. The fuel cell operates within the voltage range of 0.65 to 0.75 V for a single fuel cell unit and charges the lithium battery at a current of half its rated capacity until the remaining power of the lithium battery reaches more than 80%.

[0017] Furthermore, when the UAV transitions from a fixed-wing level flight state to a hovering state, the flight control controls the UAV to switch from the level flight motor electronic adjustment to the rotor take-off and landing motor electronic adjustment hovering state. At the same time, the FCU control system confirms to disconnect the power switch of the supercapacitor module. Then, the FCU control system controls the output voltage of the fuel cell regulated power supply to be consistent with the voltage of the lithium battery. The entire circuit of the UAV is in a state of parallel power supply of the fuel cell regulated power supply and the lithium battery.

[0018] Furthermore, when the drone is in the return landing state, the flight control sends a command to turn on the power switches at both ends of the supercapacitor module, and then the supercapacitor module and the lithium battery are powered in parallel at the same time. The supercapacitor module provides the instantaneous high power requirement when the maximum take-off weight is required. Then the flight control controls the drone to switch from the level flight motor electronic regulator to the rotor take-off and landing motor electronic regulator working state, and the drone lands vertically to the ground.

[0019] Furthermore, when the UAV triggers the emergency landing state, if the FCU control system detects that the voltage of the fuel cell drops to the preset voltage threshold, and the voltage of the supercapacitor module does not increase or the hydrogen cylinder has no pressure, the FCU control system controls the valve of the hydrogen cylinder to close, disconnects the interface of the fuel cell voltage regulator, and gives priority to using the lithium battery to land safely at the nearest safe landing point with the lowest power.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] The present invention rationally allocates power through a dynamic allocation strategy, ensuring that the UAV achieves full power output within 0.5 seconds, meeting the transient power requirements of vertical take-off and landing, and improving take-off and landing performance and safety; through supercapacitor compensation, the system response time is shortened from >1s to 0.15s; through the dynamic allocation strategy, the lithium battery only operates in the SOC range of 30% to 70%, and the cycle life is increased by 3 times, effectively avoiding overcharging and over-discharging of the lithium battery, extending the cycle life of the lithium battery, reducing replacement costs, and improving system reliability; and when the fuel cell is abnormal, it can seamlessly switch to the extended-range mode to ensure continuous flight capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flowchart of the control method of the present invention.

[0023] Figure 2 1 is an electrical schematic diagram of the control method of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] like Figures 1 to 2 As shown, this embodiment provides a control method for a fuel cell-based extended-range vertical take-off and landing fixed-wing UAV, the UAV including a hydrogen cylinder for providing hydrogen, a fuel cell for generating electricity using the hydrogen provided by the hydrogen cylinder (the fuel cell is equipped with a circulation pump for recovering hydrogen), a DC-DC voltage regulator module for stabilizing and transforming the electricity generated by the fuel cell, a supercapacitor module for receiving electricity from the DC-DC voltage regulator module and then providing electricity to the UAV to support take-off and landing of the UAV, a lithium battery for receiving electricity from the DC-DC voltage regulator module and then providing electricity to the UAV to support level flight or take-off and landing of the UAV, a level flight motor electronic regulator for utilizing the electricity from the lithium battery or DC-DC voltage regulator module and providing the power required for level flight of the UAV, a rotor take-off and landing motor electronic regulator for utilizing the electricity from the lithium battery or supercapacitor module to achieve the power required for take-off and landing of the UAV, an FCU control system for real-time collection of operating data of the lithium battery, supercapacitor module, fuel cell, and DC-DC voltage regulator module, and a flight controller for controlling the flight attitude and flight trajectory of the UAV according to instructions from the FCU control system;

[0026] The control method of the drone includes the steps of:

[0027] S1. The drone is powered on and the whole machine starts self-test to check whether all components are working properly.

[0028] S2. The flight control system collects the voltage and power of the lithium battery and supercapacitor module, and the FCU control system collects the pressure of the hydrogen tank. The FCU control system then determines whether the takeoff state is met based on the voltage and power and the pressure of the hydrogen tank. If the voltage or the pressure of the hydrogen tank is insufficient, the ground station will prompt the drone operator to replace the lithium battery and hydrogen tank.

[0029] S3. If the takeoff state is met, the FCU control system starts the fuel cell to charge the supercapacitor module through the DC-DC voltage regulator module. When the charge level of the supercapacitor module reaches a first preset charge threshold (in this embodiment, the first preset charge threshold is set to 85% of the total capacity of the supercapacitor module), the FCU control system controls the DC-DC voltage regulator module to reduce its output current until the charge level of the supercapacitor module reaches a second preset charge threshold (in this embodiment, the second preset charge threshold is set to 95% of the total capacity of the supercapacitor module), at which point charging stops.

[0030] S4. The flight controller sends the real-time flight status to the FCU control system, which then dynamically allocates the power output ratio of the lithium-ion battery, supercapacitor module, and fuel cell according to the power supply requirements of the real-time flight status to meet the different power requirements of the UAV in different flight states;

[0031] When the drone is in the take-off and landing state, the flight control sends a command to turn on the power switch of the supercapacitor module. The supercapacitor module and the lithium battery are powered in parallel at the same time. At this time, the supercapacitor module provides the instantaneous power requirement when the maximum take-off weight is required. The supercapacitor module bears about 70% of the power, and the lithium battery bears about 30% of the power, saving the power consumption of the lithium battery. Then, the flight control sends a take-off and landing command to the rotor take-off and landing motor electronic controller to realize take-off, with a response time of <0.2s. When the drone takes off vertically to the required hovering height, the FCU control system detects the voltage of the lithium battery in real time, and the FCU control system fuel control fuel cell stabilizes the voltage (set to 50V) and automatically adjusts the charging current according to the set current multiple. In this embodiment, the current multiple is set to 0.5C~1C to control the start and stop charging of the lithium battery.

[0032] When the UAV transitions from a hovering state to a fixed-wing level flight state, the flight control system controls the UAV to switch from the rotor takeoff and landing motor electronic regulator to the level flight motor electronic regulator working state. At the same time, the flight control system sends a command to disconnect the power switch of the supercapacitor module. Then the FCU control system controls the output voltage of the fuel cell regulated power supply to be consistent with the voltage of the lithium battery. The entire circuit of the UAV is in a parallel power supply state of the fuel cell regulated power supply and the lithium battery. Since the voltages are equal, the fuel cell and the lithium battery each bear approximately 50% of the UAV's power.

[0033] When the drone is in a level flight cruise state, the flight control system controls the drone to switch from the rotor takeoff and landing motor electronic control to the level flight motor electronic control working state. At this time, the output power of the fuel cell regulated power supply meets the power demand of the power fuel cell of the level flight motor electronic control, and the drone transitions to the level flight cruise state. The entire circuit of the drone is in a parallel power supply state of the fuel cell regulated power supply and the lithium battery. However, in the level flight cruise state, the FCU control system controls the voltage of the fuel cell regulated power supply to maintain a continuous output of 52V, which is higher than the voltage and power of the lithium battery. Therefore, the high-voltage circuit will be consumed first during the parallel power supply process. At this time, the fuel cell bears 95% of the drone's power consumption, and the lithium battery bears the remaining power consumption. The fuel cell efficiency is >45%; during the cruise process, the FCU controls the fuel cell regulated power supply to slowly charge the lithium battery and supercapacitor module. It takes ≤3 minutes to fully charge the supercapacitor module. The fuel cell operates within the voltage range of 0.65-0.75V for a single fuel cell unit and charges the lithium battery at a current of half the rated capacity of the lithium battery until the remaining power of the lithium battery reaches more than 80%; when the drone is in a level flight cruise state, the fuzzy controller adjusts the output power P_fc of the fuel cell.

[0034] P_fc=η·(P_load-K·dP_load / dt)

[0035] Where η is the efficiency optimization coefficient, K is the load change rate compensation weight, P_load is the total load power, dP_load is the power change, and dt is the time.

[0036] When the UAV transitions from fixed-wing level flight to hovering, the flight control system switches the level flight motor electronic control to the rotor take-off and landing motor electronic control hovering state. At the same time, the FCU control system confirms that the power switch of the supercapacitor module is disconnected. Then, the FCU control system controls the output voltage of the fuel cell regulated power supply to be consistent with the voltage of the lithium battery. The entire circuit of the UAV is in a parallel power supply state of the fuel cell regulated power supply and the lithium battery. Since the voltages are equal, the fuel cell and the lithium battery each bear approximately 50% of the UAV's power.

[0037] When the drone is in the return-to-land state, the flight control sends a command to turn on the power switches at both ends of the supercapacitor module, and then the supercapacitor module and the lithium battery are connected in parallel to supply power. At this time, the supercapacitor has a higher voltage than the lithium battery, and the supercapacitor module provides the instantaneous high power requirement when the maximum take-off weight is required, saving the power consumption of the lithium battery. Then the flight control controls the drone to switch from the level flight motor electronic control to the rotor take-off and landing motor electronic control working state, and the drone lands vertically to the ground.

[0038] After each flight of the drone is completed, the FCU control system detects the lithium battery voltage and the pressure of the hydrogen cylinder in real time, calculates the hydrogen capacity, and provides real-time feedback to the ground station to indicate the remaining mileage and whether the lithium battery and hydrogen cylinder should be replaced.

[0039] When the drone triggers the emergency landing state in an emergency, if the FCU control system detects that the voltage of the fuel cell drops to a preset voltage threshold, which in this embodiment is set to a sudden drop of >30%, and the voltage of the supercapacitor module does not increase or the hydrogen tank quickly disappears, the FCU control system will control the valve of the hydrogen tank to close, disconnect the interface of the fuel cell regulated power supply, and give priority to using the lithium battery to land safely at the nearest safe alternative landing point with the lowest power.

[0040] In this embodiment, the fuel cell stack single-chip voltage can also be monitored in real time. When any single-chip voltage is detected to be <0.4V, the output current slope is reduced to ≤20A / s, triggering the circulation pump to speed up to 120% of the rated speed, thereby achieving protection control of the fuel cell.

[0041] The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solution and invention concept of the present invention within the scope disclosed by the present invention, which falls within the scope of protection of the present invention.

Claims

1. A control method for a fuel cell-based extended-range vertical take-off and landing fixed-wing UAV, characterized in that: The UAV includes a hydrogen cylinder for providing hydrogen, a fuel cell for generating electricity using the hydrogen provided by the hydrogen cylinder, a DC-DC voltage regulator module for stabilizing and transforming the electricity generated by the fuel cell for output, a supercapacitor module for receiving electricity from the DC-DC voltage regulator module and then providing electricity to the UAV to support take-off and landing of the UAV, a lithium battery for receiving electricity from the DC-DC voltage regulator module and then providing electricity to the UAV to support level flight or take-off and landing of the UAV, a level flight motor electronic regulator for utilizing the electricity of the lithium battery or the DC-DC voltage regulator module and providing power required for level flight of the UAV, a rotor take-off and landing motor electronic regulator for utilizing the electricity of the lithium battery or the supercapacitor module to achieve the power required for take-off and landing of the UAV, an FCU control system for real-time collection of operating data of the lithium battery, the supercapacitor module, the fuel cell and the DC-DC voltage regulator module, and a flight controller for controlling the flight attitude and flight trajectory of the UAV according to instructions of the FCU control system; the control method of the UAV includes the steps of: The drone is powered on and the whole machine starts self-test to check whether all components are working properly; The flight control system collects the voltage and power of the lithium battery and supercapacitor module, and the FCU control system collects the pressure of the hydrogen tank. The FCU control system then determines whether the takeoff state is met based on the voltage and power and the hydrogen tank pressure. If the takeoff state is met, the FCU control system starts the fuel cell to charge the supercapacitor module through the DC-DC voltage regulator module. When the charge level of the supercapacitor module reaches a first preset charge threshold, the FCU control system controls the DC-DC voltage regulator module to reduce its output current until the charge level of the supercapacitor module reaches a second preset charge threshold, at which point charging stops. The flight controller sends the real-time flight status to the FCU control system, which then dynamically allocates the power output ratio of the lithium-ion battery, supercapacitor module and fuel cell according to the power supply requirements of the real-time flight status to meet the different power requirements of the drone under different flight conditions.

2. The control method of the fuel cell-based extended-range vertical take-off and landing fixed-wing UAV according to claim 1 is characterized in that: When the UAV is in the take-off and landing state, the flight control sends a command to turn on the power switch of the supercapacitor module. The supercapacitor module and the lithium battery are powered in parallel at the same time. The supercapacitor module provides the instantaneous power requirement when the maximum take-off weight is required. Then the flight control sends a take-off and landing command to the rotor take-off and landing motor electronic controller to realize take-off. When the UAV takes off vertically to the required hovering height, the FCU control system detects the voltage of the lithium battery in real time, and the FCU control system controls the fuel cell voltage and automatically adjusts the charging current according to the set current multiple after stabilizing the voltage, and controls the start and stop charging of the lithium battery.

3. The control method of the fuel cell-based extended-range vertical take-off and landing fixed-wing UAV according to claim 1, characterized in that: When the UAV transitions from a hovering state to a fixed-wing level flight state, the flight control system controls the UAV to switch from the rotor takeoff and landing motor electronic regulator to the level flight motor electronic regulator working state. At the same time, the flight control system sends a command to disconnect the power switch of the supercapacitor module. Then the FCU control system controls the output voltage of the fuel cell regulated power supply to be consistent with the voltage of the lithium battery. The entire circuit of the UAV is in a state of parallel power supply of the fuel cell regulated power supply and the lithium battery.

4. The control method of the fuel cell-based extended-range vertical take-off and landing fixed-wing UAV according to claim 1, characterized in that: When the UAV is in a level flight cruising state, the flight control controls the UAV to switch from the rotor take-off and landing motor electronic regulator to the level flight motor electronic regulator working state. At this time, the UAV's entire circuit is in a parallel power supply state of the fuel cell regulated power supply and the lithium battery, and during the parallel power supply process, the fuel cell bears 95% of the UAV's power consumption.

5. The control method of the fuel cell-based extended-range vertical take-off and landing fixed-wing UAV according to claim 4, characterized in that: When the UAV is in a level flight cruising state, the output power P_fc of the fuel cell is adjusted by the fuzzy controller. P_fc=η·(P_load-K·dP_load / dt) Where η is the efficiency optimization coefficient, K is the load change rate compensation weight, P_load is the total load power, dP_load is the power change, and dt is the time.

6. The control method of the fuel cell-based extended-range vertical take-off and landing fixed-wing UAV according to claim 4, characterized in that: During cruising, the FCU controls the fuel cell's regulated power supply to charge the lithium battery and supercapacitor module. The fuel cell operates within the voltage range of 0.65 to 0.75V for a single fuel cell unit and charges the lithium battery at a current of half its rated capacity until the remaining power of the lithium battery reaches more than 80%.

7. The control method of the fuel cell-based extended-range vertical take-off and landing fixed-wing UAV according to claim 1, characterized in that: When the UAV transitions from fixed-wing level flight to hovering, the flight control system switches the level flight motor electronic control to the rotor take-off and landing motor electronic control hovering state. At the same time, the FCU control system confirms that the power switch of the supercapacitor module is disconnected. Then, the FCU control system controls the output voltage of the fuel cell regulated power supply to be consistent with the voltage of the lithium battery. The entire circuit of the UAV is in a state of parallel power supply of the fuel cell regulated power supply and the lithium battery.

8. The control method of the fuel cell-based extended-range vertical take-off and landing fixed-wing UAV according to claim 1, characterized in that: When the drone is in the return-to-land state, the flight control sends a command to turn on the power switches at both ends of the supercapacitor module, and then the supercapacitor module and the lithium battery are powered in parallel at the same time. The supercapacitor module provides the instantaneous high power requirement when the maximum take-off weight is required. Then the flight control controls the drone to switch from the level flight motor electronic control to the rotor take-off and landing motor electronic control working state, and the drone lands vertically to the ground.

9. The control method of the fuel cell-based extended-range vertical take-off and landing fixed-wing UAV according to claim 1, characterized in that: When the drone triggers an emergency landing state, if the FCU control system detects that the voltage of the fuel cell drops to the preset voltage threshold, and the voltage of the supercapacitor module does not increase or the hydrogen tank has no pressure, the FCU control system will control the valve of the hydrogen tank to close, disconnect the interface of the fuel cell regulated power supply, and give priority to using the lithium battery to land safely at the nearest safe alternative landing point with the lowest power.

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