Control Method and System for Hydrogen Fuel UAV Stack Based on Current Step Regulation

Abstract

The present invention relates to the technical field of hydrogen fuel cell stacks, and particularly to a control method and system for a hydrogen fuel unmanned aerial vehicle stack based on current step regulation. The system improves the endurance of the hydrogen fuel unmanned aerial vehicle and extends the service life of the fuel cell stack by optimizing the control strategy and system design of the hydrogen fuel cell, while reducing system complexity and ensuring stable operation. The system mainly consists of the following key components: a main control MCU, a DC / DC converter, a hydrogen fuel cell, a hydrogen cylinder, a backup lithium battery, a flight control system, and a motor. Compared with the prior art, the present invention adopts a current step regulation strategy, effectively avoiding potential instability or too low potential caused by frequent current changes, thereby significantly improving the performance and durability of the fuel cell stack. At the same time, the system optimizes the thermal management mechanism to ensure that the fuel cell stack operates within the optimal temperature range, further extending its service life.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen fuel cell stacks, and particularly to a control method and system for a hydrogen fuel unmanned aerial vehicle stack based on current step regulation. Background Art

[0002] With the continuous development of hydrogen fuel cell technology, its application in the field of unmanned aerial vehicles has gradually attracted attention. Hydrogen fuel cells have advantages such as high energy density and long endurance time, and are considered an important development direction for future unmanned aerial vehicle power systems. However, in the prior art, there are still some problems with the control methods of hydrogen fuel unmanned aerial vehicle stacks. For example, frequent current changes can cause dynamic fluctuations in multiple aspects such as the internal reaction rate of fuel cells, water management, gas supply, polarization effect, and mechanical stability, resulting in unstable potential. Traditional control strategies are difficult to effectively address this potential instability or too low potential phenomenon, which not only affects the performance and durability of the stack, but may also lead to an increase in system complexity.

[0003] To ensure the stability of the potential during the operation of the fuel cell stack, appropriate potential regulation is particularly important. Research shows that during the operation of a proton exchange membrane fuel cell stack, the consistency of the potentials of each single cell is crucial for improving the overall performance. Especially under dynamic conditions of variable load, the uniformity of the single cell potential changes with the change of the current step amplitude and the current change frequency. By precisely adjusting these two parameters, the uniform change of the single cell potential can be effectively maintained, thereby ensuring potential stability. This provides an important theoretical basis and optimization direction for the potential balance of the stack.

[0004] In addition, the efficiency and service life of the hydrogen fuel cell stack are also limited by the thermal management system. High temperature will accelerate the aging of the internal materials of the stack, including catalysts, proton exchange membranes, and electrodes, etc.; while in a low-temperature environment, the overall temperature of the stack is low, and the electro-chemical reaction rate slows down. At the same time, the existing systems have deficiencies in adapting to different models of hydrogen fuel cell stacks, unmanned aerial vehicle flight control systems, and motor operation requirements, which limit the wide application of hydrogen fuel cell unmanned aerial vehicles.

[0005] Based on the above situation, developing a strategy that can not only achieve current step control but also effectively conduct thermal management is crucial for significantly improving the service life of the fuel cell stack. At the same time, designing a general-purpose system that can widely adapt to different models of fuel cell stacks and flight control systems is the key to achieving a technological breakthrough. Summary of the Invention

[0006] The object of the present invention is to address the problems existing in the background technology and propose a control method and system for the fuel cell stack of a hydrogen fuel unmanned aerial vehicle based on current step regulation. The aim is to effectively solve the problems of complexity, compatibility, and stack attenuation in the prior art through innovative control strategies and system architectures, thereby significantly enhancing the comprehensive performance and application value of hydrogen fuel cell unmanned aerial vehicles.

[0007] The technical solution of the present invention, in the first aspect of the present invention, a control method and system for the fuel cell stack of a hydrogen fuel unmanned aerial vehicle based on current step regulation are provided. A control system for the fuel cell stack of a hydrogen fuel unmanned aerial vehicle based on current step regulation includes a main control MCU, a DC / DC converter, a hydrogen fuel cell, a hydrogen cylinder, a backup lithium battery, a flight control system, and a motor.

[0008] The main control MCU is used to collect various data of the system operation in real time and control various parts of the system based on the collected data.

[0009] The DC / DC converter obtains the current output of the hydrogen fuel cell stack in a constant current mode according to the current regulation instruction provided by the main control MCU and delivers it to the flight control system.

[0010] The hydrogen fuel cell and the hydrogen cylinder together constitute the main power source of the system, providing continuous and stable power for the flight control system and the motor.

[0011] The backup lithium battery provides power supplement for the system when the output power of the hydrogen fuel cell is insufficient or at the initial stage of system startup; at the same time, it outputs a stable voltage for the flight control system and the motor.

[0012] Furthermore, the main control MCU controls the hydrogen supply, waste gas emission, and thermal management of the hydrogen fuel cell; at the same time, it controls the current step regulation of the DC / DC converter and the voltage maintenance of the backup lithium battery.

[0013] Furthermore, the data collected by the main control MCU includes temperature, air pressure, Hall current, voltage, external switch state, and fan speed.

[0014] Furthermore, the input-output voltage range of the DC / DC converter is between 10V and 130V.

[0015] In the second aspect of the present invention, a control method for the fuel cell stack of a hydrogen fuel unmanned aerial vehicle based on current step regulation is provided. Using the above system to control the unmanned aerial vehicle, it includes the following specific steps:

[0016] S1. Connect the power supply of the lithium battery, open the valve of the hydrogen cylinder, and trigger the external switch of the main control MCU.

[0017] S2. The main control MCU controls the intake valve and the exhaust valve to open and starts the cooling fan for startup purging to remove the residual gas inside the stack.

[0018] S3. After completing the purging, keep the intake valve open at all times, regularly open the exhaust valve, and collect environmental and stack operation data in real time; the environmental and stack data in step S3 specifically include: environmental temperature, stack temperature, fan speed, stack output current and voltage, charging or discharging current of the lithium battery, lithium battery voltage, hydrogen cylinder pressure, and external switch status;

[0019] S4. When the drone starts, the main control MCU adjusts the fan PWM signal according to the environmental temperature and output current to maintain the stack within the optimal temperature range and dynamically adjust the duty cycle;

[0020] S5. The current required by the drone is evenly distributed to the two stacks, and the current is adjusted step by step through a DC / DC converter;

[0021] S6. After the drone lands and comes to a complete stop, turn off the external switch to trigger the shutdown purging signal, and the main control MCU controls the intake valve and exhaust valve to open, and the cooling fan runs stably to remove the residual gas;

[0022] S7. After the shutdown purging is completed, the main control MCU controls the cooling fan to rotate at full speed to remove the residual moisture in the stack;

[0023] S8. After completing the shutdown purging and drying process, close the hydrogen cylinder valve and the lithium battery switch to end the system operation.

[0024] Further, in step S1, once the external switch is detected to be closed, the pin of the main control MCU is grounded, triggering the startup purging process of the stack.

[0025] Further, in step S2, open the intake valve and exhaust valve of the stack, and output a PWM signal with a duty cycle of 42% to drive the stack cooling fan.

[0026] Further, in step S5, the actual output current of the stack is accurately monitored and adjusted through the dual feedback mechanism of the processor; in the case of increasing current, the first feedback mechanism of the processor is responsible for monitoring and accumulating the amplitude of the current step in real time; when the accumulated step amplitude reaches the set value, the second feedback mechanism is activated, and the system gradually increases the output current of the stack at a set rate through the DC / DC converter.

[0027] Further, when the current needs to be reduced, the system will gradually reduce the output current of the stack at a set rate.

[0028] Further, in step S6, after manually closing the external switch, the pin voltage of the main control MCU is 3.3V, sending out the shutdown purging signal of the hydrogen fuel cell stack; the system executes steps S7 - S8 until the system ends operation.

[0029] Compared with the prior art, the present invention has the following beneficial technical effects:

[0030] (1) The present invention adopts a step - type current regulation strategy and a dual - feedback mechanism, which can effectively suppress the potential fluctuation and too - low phenomenon of the stack caused by frequent current changes, and significantly reduce the poisoning reaction of the catalyst inside the stack and the accumulation of electrochemical stress. After testing, under the condition of a current density of 175 A / cm², when the 2 - kW stack operates for 100 hours simulating the UAV working condition using the method of the present invention, the attenuation degree is significantly reduced by 56.5% compared with the traditional method. This result shows that the present invention has significant advantages in improving the durability and voltage stability of the stack, and can effectively delay the performance decay of the stack.

[0031] (2) Based on the three - dimensional fitting surface of the ambient temperature and the output current, and combined with the PI regulation algorithm, the present invention accurately regulates the duty cycle of the PWM signal of the stack fan to ensure that the stack temperature is always maintained within the optimal reaction temperature range. This dynamic temperature management strategy monitors the deviation between the central point temperature of the stack and the preset optimal reaction temperature in real time, calculates the corresponding PWM duty cycle using the PI algorithm, and dynamically adjusts the fan speed, thereby effectively suppressing temperature fluctuations. This precise temperature control method not only optimizes the operating efficiency of the stack under different working conditions, but also significantly reduces problems such as the decrease in catalyst activity and the aggravation of side reactions inside the stack caused by abnormal temperatures, and thus extends the service life of the stack.

[0032] (3) The input - output voltage range of the high - power DC / DC converter adopted by the present invention is 10 - 130 V, which can adapt to stacks and flight control systems with various voltage configurations. This wide - voltage - range design significantly improves the compatibility and flexibility of the system, enabling it to adapt to different models of hydrogen fuel cell stacks and the diverse requirements of flight control systems. In addition, the system also has good scalability and can be customized according to the actual application scenario, further enhancing its application value in the field of hydrogen fuel cell UAVs.

[0033] (4) The overall system operation process of the present invention is highly simplified and has extremely high user - friendliness. After completing the assembly of the power system package, the user only needs to turn on the lithium - battery power switch, the hydrogen - cylinder valve, and the control - board switch in sequence, and the system can enter the working state to achieve the rapid startup and operation of the UAV. This startup process fully considers the convenience and safety of operation, ensuring that the user can activate the system in the shortest time while avoiding the risks that may be brought by complex operation steps. During the shutdown process, the system also follows the principle of simplicity and efficiency. The user only needs to turn off the control - board switch, the hydrogen - cylinder valve, and the lithium - battery switch in the reverse order to complete the safe shutdown of the system. This shutdown process is not only easy to operate but also, through reasonable sequence design, ensures the stability of the system during shutdown and avoids potential safety hazards caused by sudden power failure or hydrogen - supply interruption.

[0034] (5) During the startup and shutdown processes, the system respectively executes a purging process to remove the residual gas and moisture inside the stack. The startup purge ensures that the stack is in a clean and stable state before startup, while the shutdown purge prevents safety risks and stack damage caused by residual gas and moisture. In addition, the full - speed rotation treatment of the cooling fan after shutdown further ensures the dryness inside the stack, prepares for the next startup, and enhances the safety and reliability of the system. Brief Description of the Drawings

[0035] Figure 1 Schematic diagram of the control method and system structure of a hydrogen - fuel UAV stack based on current - step regulation

[0036] Figure 2 Flowchart of the control method and system of a hydrogen - fuel UAV stack based on current - step regulation

[0037] Figure 3 Shows the variation of the duty cycle of the cooling fan under different ambient temperatures and stack - current conditions. Detailed Embodiments

[0038] Embodiment 1

[0039] As Figure 1 shown, a control system of a hydrogen - fuel UAV stack based on current - step regulation proposed by the present invention includes a main - control MCU, a DC / DC converter, a hydrogen fuel cell, a hydrogen cylinder, a backup lithium battery, a flight - control system, and a motor.

[0040] The main - control MCU, as the central nerve of the system, is responsible for real - time collecting various key data of the system operation and achieving precise control of each component based on these data. Specifically, its control functions cover the hydrogen supply, exhaust gas emission, and thermal - management links of the hydrogen - fuel - cell stack; the current - step regulation of the high - power DC / DC converter; and the voltage maintenance of the backup lithium battery.

[0041] The DC / DC converter plays a crucial role in the system. According to the current regulation instruction provided by the main control MCU, it accurately obtains the current output of the hydrogen fuel cell stack in constant current mode and stably delivers it to the flight control system. Its input and output voltage range is wide, between 10V and 130V, which enables it to effectively connect the hydrogen fuel cell stack and the flight control system, act as a power conversion bridge between them, and has good adaptability, being able to be compatible with various models of hydrogen fuel cell stacks and flight control systems.

[0042] The hydrogen fuel cell and the hydrogen cylinder together constitute the main power source of the system, providing continuous and stable power support for the flight control system and the motor to ensure the efficient operation of the system.

[0043] The backup lithium battery plays a dual role in the system: on the one hand, it provides necessary power supplement for the system in special situations such as when the output power of the hydrogen fuel cell is insufficient or at the initial stage of system startup; on the other hand, it can also output a stable voltage for the flight control system and the motor to ensure the reliable operation of the system under various working conditions.

[0044] The control process of the system, as Figure 2 shown, at startup, first turn on the lithium battery power switch and the hydrogen cylinder valve, then the system enters the operating state and starts to monitor key operating parameters in real time, including but not limited to temperature, air pressure, Hall current, voltage, and the status of external switches. Once the switch is detected to be closed, that is, when the control board processor pin is connected to 3.3V voltage, the system triggers the startup purge process of the fuel cell stack. This process involves opening the intake valve and exhaust valve of the fuel cell stack and outputting a PWM signal with a duty cycle of 42% to drive the fuel cell stack cooling fan.

[0045] After the power-on purge process is completed, the system will start the high-power DC / DC converter, which obtains current from the battery stack in constant current mode and controls the timing of the exhaust valve opening. At the same time, the system will dynamically adjust the duty cycle of the fan PWM signal according to the real-time monitored current and temperature data to optimize the heat dissipation effect. In constant current mode, the current value obtained by the high-power DC / DC converter from the battery stack will be distributed according to the power demand of the drone. Specifically, the required total current will be evenly distributed to the two hydrogen fuel cell stacks. The system adopts a step current regulation strategy and accurately monitors and adjusts the actual output current of the battery stack through the dual feedback mechanism of the processor. In the case of increasing current, the first feedback mechanism of the processor is responsible for real-time monitoring and accumulating the amplitude of the current step. When the accumulated step amplitude reaches 3A, the second feedback mechanism is activated, and the system gradually increases the output current of the battery stack at a rate of 3A / s through the DC / DC converter. On the contrary, when the current needs to be reduced, the system will gradually reduce the output current of the battery stack at a rate of 10A / s. After the drone is used, turn off the switch first. When the switch is detected to be disconnected, that is, the control board processor pin is grounded, the system will execute the shutdown purge process of the battery stack. This process first opens the intake valve and exhaust valve, and sets the duty cycle of the fan PWM signal to 42%. After the purge is completed, the system will close all solenoid valves and make the fan rotate at high speed for 10 seconds, and then end the system operation.

[0046] Example 2

[0047] The present invention proposes a control method for a hydrogen fuel UAV stack based on current step regulation, comprising the following steps:

[0048] (1) Connect the lithium battery power supply, open the hydrogen cylinder valve, and trigger the external switch of the control circuit board to prepare for system startup.

[0049] (2) The STM32H7 microcontroller controls the opening of the intake valve and the exhaust valve, and starts the cooling fan to perform power-on purge to remove residual gas inside the fuel cell stack.

[0050] (3) After the purge is completed, keep the intake valve open, open the exhaust valve regularly, and collect environmental and stack operation data in real time to provide support for subsequent control.

[0051] (4) When the drone starts, the STM32H7 microcontroller adjusts the fan PWM signal according to the ambient temperature and output current, maintains the battery stack in the optimal temperature range, and dynamically adjusts the duty cycle to ensure stable operation.

[0052] (5) The system evenly distributes the current required by the drone to the two battery stacks and adjusts the current in steps through the DC / DC converter to ensure stable output of the battery stack and avoid potential fluctuations.

[0053] (6) After the drone lands and stops, turn off the external switch to trigger the shutdown and purge signal. The STM32H7 microcontroller controls the opening of the intake valve and exhaust valve, and the cooling fan runs steadily to remove residual gas.

[0054] (7) After the shutdown and purge are completed, the STM32H7 microcontroller controls the cooling fan to rotate at full speed to remove residual moisture in the stack and ensure that the inside of the stack is dry.

[0055] (8) After completing the shutdown, purging and drying processes, close the hydrogen cylinder valve and the lithium battery switch to end system operation.

[0056] Furthermore, in step (1), the switching of the level state of the designated pin of the processor (STM32H7 single-chip microcomputer chip) on the circuit board is realized by controlling the closing and opening of the external switch. When the pin level is switched to 3.3V, the signal is defined as the power-on purge instruction of the hydrogen fuel cell stack, thereby triggering the system initialization purge process.

[0057] Furthermore, in step (2), the STM32H7 single-chip microcomputer is the core processor of the control circuit board, which precisely controls the opening of the intake valve and exhaust valve of the hydrogen fuel cell stack by enabling the corresponding driver chip, and drives the cooling fan to start through the PWM signal to perform the power-on purge process. This process is intended to remove the residual gas inside the fuel cell stack to ensure that the fuel cell stack is in a clean and stable state before starting.

[0058] Furthermore, after the stack purge is completed in step (3), the intake valve is kept open and the exhaust valve is opened regularly to maintain the gas circulation inside the stack. The operating data collected by the system in real time include the ambient temperature, the center temperature of the stack, the output current, the output voltage, and the output current and voltage of the lithium battery. At the same time, the current required for the operation of the drone is monitored to provide real-time data support for subsequent operation control.

[0059] Furthermore, in step (4), when the UAV is started and powered by the hydrogen fuel cell stack and the lithium battery, the STM32H7 single-chip microcomputer selects a preset duty cycle as the PWM signal of the stack fan on the three-dimensional fitting surface according to the ambient temperature and the stack output current, so as to accurately control the stack temperature within the optimal reaction temperature range under the current. At the same time, the system uses a proportional-integral (PI) regulator to dynamically adjust the duty cycle of the fan PWM signal according to the deviation between the real-time measured stack center temperature and the preset optimal reaction temperature. When the stack center temperature is higher or lower than the optimal reaction temperature, the system automatically increases or decreases the duty cycle of the fan PWM signal to maintain the stability of the stack temperature.

[0060] Further, in step (5), the system first evenly distributes the total required current to the two hydrogen fuel cell stacks according to the power demand of the drone. This distribution strategy aims to set clear and balanced current demand targets for each stack, ensuring that the two stacks can work together during operation and avoiding performance differences caused by uneven current distribution. Subsequently, the system precisely regulates the output current of each hydrogen fuel cell stack through a DC / DC converter to ensure that the output current of the stack can accurately match the actual power demand of the drone. To achieve this goal, the system adopts a stepwise current regulation strategy, dynamically monitoring and adjusting the actual output current of the stack through a dual feedback mechanism of the processor. Specifically, taking the increase in current as an example, the first feedback mechanism of the processor is responsible for real-time monitoring and accumulating the current change value. When the accumulated change value reaches the step amplitude (e.g., 3 amperes) set by the second feedback mechanism, the second feedback mechanism is triggered, and the accumulated time during this process is the step period (e.g., 1 second). The system gradually increases the output current of the stack at a set rate (3 A / s) through the DC / DC converter. Similarly, when the current needs to be reduced, the system will gradually reduce the output current of the stack at another rate (10 A / s).

[0061] Further, in step (6), after the drone lands and is in a stable state, the operator will turn off the external switch on the control circuit board. The external switch refers to the low switch that gives a low-level signal to the single-chip microcomputer when closed, and closing the switch will trigger the system purge program. This step will trigger the pin of the STM32H7 single-chip microcomputer chip of the processor to be grounded, thereby sending a shutdown purge signal for the hydrogen fuel cell stack. This signal is a key instruction to start the shutdown purge process, aiming to remove the potentially residual hydrogen and water inside the stack, prevent potential safety risks, and prepare for the next start of the stack. In this way, the system can ensure the safety and reliability of the drone and its equipped hydrogen fuel cell stack in the shutdown state.

[0062] Further, after the shutdown purge in step (7) is completed, the STM32H7 single-chip microcomputer chip makes the stack cooling fan run at full speed through the PWM signal to further remove the residual moisture inside the stack, ensure the dryness inside the stack, and prepare for the next start.

[0063] The following uses a specific case to introduce the solution of the present invention in detail:

[0064] Suppose the target demand current value for a single stack during the flight of the drone is , and the function is obtained through the first feedback system. According to the value, the actual output current value of the stack is obtained through the second feedback, where The stepped wave signal satisfies an increase of S1 amperes every T1 seconds or a decrease of S2 amperes every T2 seconds, and the update formula is:

[0065]

[0066] That is, the first-stage feedback The cumulative current change value, when its error with the actual output current value of the stack is greater than S1 or less than -S2, triggers the step of the second-stage feedback function The core processor used in this system is the STM32H7 single-chip microcomputer chip, and its feedback operation time is set to 10 milliseconds. Therefore, The update formula of

[0067]

[0068] In summary, the periods T1 and T2 of the current step are determined by the first-stage feedback function The amplitudes S1 and S2 of the current step are determined by the second-stage feedback function In practical applications, the step sizes S1 and S2, and the time intervals T1 and T2 can be adjusted according to the characteristics of different stacks. Subsequently, through CAN bus communication, the actual output current value of the stack is transmitted to the high-power DC / DC converter. After receiving the CAN signal, the DC / DC converter will obtain the corresponding output current value from the stack accordingly. The specific experimental steps are as follows:

[0069] First, collect the flight power change data of a 25 kg-class unmanned aerial vehicle (UAV) at each stage of takeoff, hover, flight along the route, return, and landing. Analyze the collected power data to clarify the power characteristics and change laws at each flight stage, and accordingly set the working mode of the programmable electronic load meter so that its power change can accurately simulate the actual flight power change of the UAV. Each operation time is 1 hour, and during this process, the power output of the electronic load meter is monitored in real time to ensure that it is consistent with the UAV flight power change to meet the experimental requirements;

[0070] Table 1 compares the voltage attenuation of a 2 kW stack after running for 100 hours between the traditional method and the current step adjustment method at a current density of 175 A / cm². Among them, the traditional method refers to the ordinary control method in which the stack current is not adjusted and the current changes in real time with the load. The comparison results are based on the difference between the voltage of the stack after operation and the initial voltage before operation, and are used to evaluate the influence of the two methods on the stack performance. The results show that the voltage of the traditional method decays by 8.5% after running for 100 hours, while the voltage attenuation of the current step adjustment method is only 3.8%, and the attenuation degree is significantly reduced by 56.5%

[0071] Table 1 Comparison table of attenuation degrees of a 2 kW stack after running for 100 hours

[0072]

[0073] Changes in the fan speed and ambient temperature can lead to significant differences in the operating temperature of the fuel cell stack. In the experiment, by manually adjusting the duty cycle of the PWM control signal of the fan, the fan speed was precisely adjusted to effectively control the operating temperature of the fuel cell stack. At the same time, the operating temperature and voltage data of the fuel cell stack at different fan speeds were recorded in real time to analyze the relationship between the fan speed and the performance of the fuel cell stack. Table 2 lists the output voltage values of a 2kW fuel cell stack at different operating temperatures when the current density is 200A / cm². The results show that there are obvious differences in the output voltage of the fuel cell stack at different temperatures, which fully indicates that the operating temperature has a significant impact on the performance of the fuel cell stack. Therefore, effective thermal management of the fuel cell stack is the key to ensuring its efficient and stable operation.

[0074] Table 2 Output Voltage Table of 2kW Fuel Cell Stack at Different Operating Temperatures

[0075]

[0076] To achieve the optimal operating state of the fuel cell stack, it is necessary to test and determine the duty cycle of the PWM control signal of the cooling fan required to maintain the optimal operating temperature of the fuel cell stack under diverse combinations of ambient temperature and fuel cell stack output current. Under four ambient temperature conditions of 10°C, 20°C, 32°C, and 35°C, by manually adjusting the duty cycle of the PWM (pulse width modulation) control signal of the fan, the fan speed was changed to adjust the operating temperature of the fuel cell stack. At the same time, the potential change of the fuel cell stack was monitored and recorded to determine the operating temperature range at which the potential of the fuel cell stack reaches the highest under each ambient temperature, and the duty cycle value of the fan PWM control signal at this time was accurately recorded to provide key data support for subsequent thermal management. The following table shows the test results for the 2kW fuel cell stack used in the system.

[0077] Table 3 Test Results Table of 2kW Fuel Cell Stack

[0078]

[0079] Based on the data in the table, as shown in Figure 3The three-dimensional surface diagram shown. This diagram clearly depicts the mutual relationship among the ambient temperature, the stack current, and the duty cycle of the cooling fan. The parameters represented by each axis in the diagram are as follows: The X-axis (horizontal axis) indicates the ambient temperature, and the measurement range is set between 0 and 35 degrees Celsius. The Y-axis (front-rear axis) indicates the stack current, and the measurement range is set between 0 and 80 amperes. The Z-axis (vertical axis) indicates the duty cycle of the cooling fan, and the measurement range is set between 40% and 48%. During the operation of the system, by collecting the real-time ambient temperature and stack output current data, the corresponding duty cycle value can be accurately found in this three-dimensional diagram. During the operation of the system, by collecting the real-time ambient temperature and stack output current data, the duty cycle value of the corresponding cooling fan PWM signal can be accurately found based on the pre-constructed three-dimensional diagram. At the same time, the system needs to dynamically adjust the duty cycle of the fan PWM signal according to the deviation between the real-time measured temperature at the center point of the stack and the preset optimal reaction temperature to ensure that the stack always operates within the optimal temperature range, thereby maintaining its efficient and stable operation.

[0080] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those skilled in the art to which the present invention pertains.

Claims

1. A control system for a fuel cell of a hydrogen fuel unmanned aerial vehicle based on current step regulation, characterized in that, Including main control MCU, DC / DC converter, hydrogen fuel cell, hydrogen cylinder, backup lithium battery, flight control system and motor; The main control MCU is used to collect various data of system operation in real time and control various parts of the system based on the collected data; The DC / DC converter obtains the current output of the hydrogen fuel cell stack in constant current mode according to the current regulation instruction provided by the main control MCU, and transmits it to the flight control system; The hydrogen fuel cell and hydrogen tank together constitute the main power source of the system, providing continuous and stable power for the flight control system and motor; The backup lithium battery provides power to the system when the hydrogen fuel cell output power is insufficient or the system is initially started; it also outputs a stable voltage to the flight control system and motor. The control steps of the UAV battery stack are as follows: S1, connect the lithium battery power supply, open the hydrogen cylinder valve, and trigger the external switch of the main control MCU; S2, the main control MCU controls the intake valve and exhaust valve to open, and starts the cooling fan to perform power-on purge to remove the residual gas inside the battery stack; S3. After the purge is completed, the intake valve is kept open, the exhaust valve is opened regularly, and the environment and stack operation data are collected in real time; S4: When the drone starts, the main control MCU adjusts the fan PWM signal according to the ambient temperature and output current, maintains the battery stack in the optimal temperature range, and dynamically adjusts the duty cycle; S5. The current required by the drone is evenly distributed to the two battery stacks, and the current is adjusted in steps through the DC / DC converter; S6. After the drone lands and stops, turn off the external switch to trigger the shutdown and purge signal. The main control MCU controls the air intake valve and exhaust valve to open, and the cooling fan runs steadily to remove residual gas. S7, after the shutdown and purge is completed, the main control MCU controls the cooling fan to rotate at full speed to remove the residual moisture in the stack; S8. After the shutdown, purging and drying process are completed, the hydrogen cylinder valve and the lithium battery switch are closed to terminate the system operation; In step S5, the actual output current of the battery stack is accurately monitored and adjusted through the dual feedback mechanism of the processor; when the current increases, the first feedback mechanism of the processor is responsible for real-time monitoring and accumulating the amplitude of the current step; When the cumulative step amplitude reaches the set value, the second feedback mechanism is activated, and the system gradually increases the output current of the battery stack at a set rate through the DC / DC converter; During the flight of the drone, the target demand current value for a single fuel cell is , and through a first-level feedback system, the function is obtained; according to , the value is used for the second feedback to obtain the actual output current value of the fuel cell , where is a staircase wave signal that increases by S1 amperes every T1 seconds or decreases by S2 amperes every T2 seconds. The update formula is: That is, the first-level feedback accumulates the current change value. When the error between it and the actual output current value of the fuel cell is greater than S1 or less than -S2, it triggers a step of the second-level feedback function ; The feedback operation time of this system is set to 10 milliseconds; The update formula of is: The periods T1 and T2 of the current step are determined by the first-level feedback function .

2. The control system of the hydrogen fuel unmanned aerial vehicle stack based on current step regulation according to claim 1, wherein, The main MCU controls the hydrogen supply, exhaust emissions and thermal management of the hydrogen fuel cell; it also controls the current step regulation of the DC / DC converter and the voltage maintenance of the backup lithium battery.

3. The control system of the fuel cell of the hydrogen fuel unmanned aerial vehicle based on current step regulation according to claim 1, characterized in that, The data collected by the main MCU includes temperature, air pressure, Hall current, voltage, external switch status and fan speed.

4. The control system of the fuel cell of the hydrogen fuel unmanned aerial vehicle based on current step regulation according to claim 1, characterized in that The input and output voltage range of the DC / DC converter is between 10V and 130V.

5. The control system of the hydrogen fuel unmanned aerial vehicle stack based on current step regulation according to claim 1, wherein Once the external switch is detected to be closed in step S1, the main control MCU pin is grounded, which triggers the power-on purge process of the battery stack.

6. The control system of the hydrogen fuel unmanned aerial vehicle stack based on current step regulation according to claim 1, characterized in that, In step S2, the intake valve and exhaust valve of the fuel cell stack are opened, and a PWM signal with a duty cycle of 42% is output to drive the fuel cell stack cooling fan.

7. The control system of the hydrogen fuel unmanned aerial vehicle stack based on current step regulation according to claim 1, characterized in that, When the current needs to be reduced, the system will gradually reduce the output current of the battery stack at a set rate.

8. The control system of the hydrogen fuel cell unmanned aerial vehicle stack based on current step regulation according to claim 1, characterized in that, After manually turning off the external switch in step S6, the pin of the main control MCU is connected to a 3.3V voltage, and a shutdown purge signal for the hydrogen fuel cell stack is sent; the system executes steps S7 - S8 until the system ends its operation.

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