Control method for power system of parallel type oil-electric hybrid aircraft

Abstract

The invention provides a power system control method for a parallel type oil-electric hybrid aircraft, and relates to the technical field of aircraft power system control. The method is suitable for a power system composed of a high-power-to-weight-ratio piston engine, a bidirectional output motor, a bidirectional generator and a high-energy-density battery pack. The operation state of the aircraft, the working state of a power system and the charge state of a battery pack are obtained through an airborne sensor, and a unified required power calculation and power mode judgment mechanism is constructed in a flight management computer. According to the method, the efficient output interval of the engine is determined based on the universal characteristic curve of the engine, the optimal mode is autonomously selected from pure electric, direct drive, hybrid power, power generation and kinetic energy recovery modes and power distribution is implemented by combining the flight mission, the battery pack charge state and the required power relation, and the engine is kept running in the efficient interval as much as possible; therefore, the efficiency of a power system is improved, fuel consumption is reduced, and safe, efficient and economic cooperative control under all working conditions is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aircraft power system control, in particular to a parallel oil-electric hybrid aircraft power system control method. BACKGROUND

[0002] With the wide application of unmanned aerial vehicles and light aviation aircraft in low-altitude reconnaissance, environmental monitoring, logistics transportation and emergency rescue fields, hybrid power technology gradually becomes an important development direction of aircraft power systems due to its advantages of high energy density of fuel and high efficiency and fast response of electric motor. At present, parallel oil-electric hybrid architecture has high power output efficiency and high safety redundancy of dual power sources, and is more applied to small aviation piston engine power systems. However, the existing parallel oil-electric hybrid aircraft power system lacks a suitable control method for the engine, and mostly borrows the control logic of traditional engines, which is not fully adapted to the complex flight conditions of aircraft, and has significant shortcomings in global optimization of system efficiency, dynamic switching of power mode and battery balancing control, and is difficult to achieve the collaborative goal of high efficiency and low fuel consumption.

[0003] The core advantage of hybrid power aircraft lies in the collaborative control of engine and electric motor. The design of dual power sources makes the output torque of engine and electric motor complementary, so that the engine always operates in the high-efficiency output interval, thereby improving the output efficiency of engine and reducing the fuel consumption rate of engine.

[0004] Most of the existing parallel oil-electric hybrid control methods are single control for engine or electric motor. Even if the control method of dual power is considered, there is still a problem of local optimization rather than global optimization: most systems prefer to pursue the efficiency optimization of engine or electric motor, but ignore the collaborative influence of engine state, high energy density battery SOC and other conditions. In summary, the existing parallel oil-electric hybrid aircraft power system control method is difficult to meet the demand of aircraft for overall high efficiency due to the lack of global efficiency optimization thinking, poor working condition adaptability and insufficient SOC dynamic adaptation. Therefore, a control method that can accurately define the high-efficiency direct-drive interval and dynamically adapt the system global and flight conditions is needed to solve the above technical problems. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a parallel oil-electric hybrid aircraft power system control method, which introduces the engine high-efficiency output interval and battery state of charge into the power mode determination together, so as to realize more efficient, safer and more economical power coordination control of oil-electric hybrid aircraft in all working conditions.

[0006] To achieve the above purpose, the present application provides the following solutions: A parallel oil-electric hybrid aircraft power system control method is applied to a power system of an aircraft including a high power-to-weight ratio piston engine, a bidirectional output motor, a bidirectional generator and a high energy density battery pack, comprising: Collecting the operating state of the aircraft, the working state of the power system and the state of charge of the high energy density battery pack through on-board sensors, and inputting the operating state, the working state and the state of charge into the flight management computer as basic data for control calculation; According to the universal characteristic curve of the high power-to-weight ratio piston engine, the efficient output interval of the engine is determined in the flight management computer, the lowest driving curve and the highest driving curve of the engine are determined in the efficient output interval, and the efficient output interval and the lowest driving curve and the highest driving curve are used as basis parameters for power mode determination; Based on the basic data, the current flight task and flight condition of the aircraft are combined to calculate the demand power of the aircraft at the current time in the flight management computer, and the demand power is compared with the power range corresponding to the lowest driving curve and the highest driving curve of the engine to obtain the relationship data between the demand power and the efficient output interval of the engine; According to the state of charge of the high energy density battery pack and the relationship data between the demand power and the efficient output interval of the engine, at least one power mode is selected from the pure electric driving mode, the engine direct driving mode, the oil-electric hybrid driving mode, the power generation mode and the kinetic energy recovery mode, and the corresponding power mode decision instruction is generated; According to the power mode decision instruction, power distribution instructions are generated in the flight management computer and sent to the high power-to-weight ratio piston engine, the bidirectional output motor and the bidirectional generator to adjust the output power of the high power-to-weight ratio piston engine, the output power of the bidirectional output motor and the power generation power of the bidirectional generator, so that the high power-to-weight ratio piston engine works in the efficient output interval under the premise of meeting the demand power of the aircraft and the state of charge constraint of the high energy density battery pack.

[0007] Preferably, the on-board sensors include: an aircraft state sensor and a power system sensor; the aircraft state sensor is used to collect aircraft state data and input the collected aircraft state data into the flight management computer; the aircraft state data includes: flight speed, altitude, surface pressure, and ambient temperature and humidity; the power system sensor is used to collect power system state data and input the collected power system state data into the flight management computer as one of the basic data sources for control calculation; the power system state data includes: high power-to-weight ratio piston engine speed, engine fuel consumption, engine output power, bidirectional output motor speed, bidirectional output motor torque, power system key part temperature, and high energy density battery pack voltage.

[0008] Preferably, the aircraft demand power at the current time is calculated in the flight management computer, including: Based on the aircraft operating state in the basic data, parameters related to flight power are extracted; the parameters related to flight power include aircraft load, air density, altitude, atmospheric conditions, and wing angle of attack; Based on the parameters related to flight power, the power demand required to overcome aerodynamic resistance and maintain flight during flight is calculated according to the aerodynamic relationship to obtain initial power demand data during flight; The initial power demand data is corrected according to an empirical correction model and compared with the power range corresponding to the current flight profile for verification, and in the case of verification passing, the corrected power demand is taken as the aircraft demand power.

[0009] Preferably, the efficient output interval of the engine is determined in the flight management computer, and the minimum driving curve of the engine and the maximum driving curve of the engine are determined within the efficient output interval, including: Based on the universal characteristic curve provided by the engine manufacturer, the effective fuel consumption rate of the high power-to-weight ratio piston engine under different speed and torque combinations is analyzed, and the area with low effective fuel consumption rate and high efficiency is determined as the efficient output interval of the engine; Within the efficient output interval of the engine, a continuous power trajectory corresponding to the lower limit of the output power along the engine speed change direction is taken as the minimum driving curve of the engine, and a continuous power trajectory corresponding to the upper limit of the output power along the engine speed change direction is taken as the maximum driving curve of the engine, and the working power range of the high power-to-weight ratio piston engine is defined by the minimum driving curve of the engine and the maximum driving curve of the engine.

[0010] Preferably, in the process of power mode determination, the setting method of the state of charge interval of the high energy density battery pack and the engine output power interval includes: The state of charge of the high-energy-density battery pack is divided into a low charge interval, an intermediate charge interval, and a high charge interval, the high-energy-density battery pack is considered to be in the low charge interval when the state of charge of the high-energy-density battery pack is less than 15% of the rated capacity of the high-energy-density battery pack, the high-energy-density battery pack is considered to be in the intermediate charge interval when the state of charge of the high-energy-density battery pack is greater than or equal to 15% and less than 60% of the rated capacity of the high-energy-density battery pack, and the high-energy-density battery pack is considered to be in the high charge interval when the state of charge of the high-energy-density battery pack is greater than or equal to 60% of the rated capacity of the high-energy-density battery pack. The output power corresponding to the engine minimum driving curve is defined as the engine minimum driving power, and the output power corresponding to the engine maximum driving curve is defined as the engine maximum driving power, and the engine minimum driving power and the engine maximum driving power are used to segmentally compare the aircraft demand power when the power mode is determined.

[0011] Preferably, the bottom-layer control logic of the aircraft comprises: In the pure electric driving mode, the high-power-to-weight ratio piston engine does not output power, the high-energy-density battery pack supplies power to the bidirectional output motor, the bidirectional output motor outputs power and drives the propeller through the transmission mechanism to meet the aircraft demand power. In the engine direct drive mode, the bidirectional output motor does not output power, fuel supplies power to the high-power-to-weight ratio piston engine, the high-power-to-weight ratio piston engine outputs power and drives the propeller through the transmission mechanism. In the oil-electric hybrid driving mode, the high-power-to-weight ratio piston engine and the bidirectional output motor simultaneously output power to jointly drive the propeller, the high-power-to-weight ratio piston engine provides basic power, and the bidirectional output motor provides power compensation. In the power generation mode, part of the power output by the high-power-to-weight ratio piston engine is used to drive the propeller, and the other part is converted into electrical energy through the bidirectional generator and stored in the high-energy-density battery pack, for improving the state of charge of the high-energy-density battery pack. In the kinetic energy recovery mode, when the aircraft demand power is less than zero, the bidirectional output motor switches to the power generation state, recovers the excess kinetic energy in the flight process through the propeller and the transmission system, converts the recovered mechanical energy into electrical energy and stores it in the high-energy-density battery pack.

[0012] Preferably, the upper-layer control logic of the aircraft at least comprises: When the aircraft is in gliding or working condition that does not require propulsion power, resulting in the power system being in a non-output state, the power system is set to kinetic energy recovery mode, and the bidirectional output motor is used for kinetic energy recovery to improve the state of charge of the high-energy-density battery pack; When the power system is in an output state and the high-power-to-weight ratio piston engine is in an inappropriate output state or the high-power-to-weight ratio piston engine cannot output power, the power system is set to pure electric drive mode, and the high-energy-density battery pack supplies power to the bidirectional output motor, and the bidirectional output motor independently drives the propeller to meet the demand power of the aircraft.

[0013] Preferably, when the state of charge of the high-energy-density battery pack is in the low charge interval, the upper-layer control logic includes: When the demand power of the aircraft is less than the minimum driving power of the engine, the power system is set to a combination of the engine direct drive mode and the power generation mode, so that the high-power-to-weight ratio piston engine works in the high-efficiency output interval of the engine, and the high-energy-density battery pack is charged through the bidirectional generator to preferentially restore the state of charge of the high-energy-density battery pack; When the demand power of the aircraft is between the minimum driving power of the engine and the maximum driving power of the engine, the power system is set to the engine direct drive mode, so that the high-power-to-weight ratio piston engine independently drives the propeller in the high-efficiency output interval of the engine; When the demand power of the aircraft is greater than the maximum driving power of the engine, the power system is set to the engine acceleration direct drive mode, so that the high-power-to-weight ratio piston engine outputs power at the upper boundary of the high-efficiency output interval of the engine to meet the demand for propulsion power in high-power flight working conditions.

[0014] Preferably, when the state of charge of the high-energy-density battery pack is in the intermediate charge interval, the upper-layer control logic includes: When the demand power of the aircraft is less than the minimum driving power of the engine, the power system is set to a combination of the engine direct drive mode and the power generation mode, so that the high-power-to-weight ratio piston engine works in the high-efficiency output interval of the engine, and the high-energy-density battery pack is charged through the bidirectional generator; When the demand power of the aircraft is between the minimum driving power of the engine and the maximum driving power of the engine, the power system is set to the engine direct drive mode, so that the high-power-to-weight ratio piston engine independently drives the propeller in the high-efficiency output interval of the engine; When the aircraft demand power is greater than the maximum driving power of the engine and the aircraft demand power minus the maximum output power of the bidirectional output motor is still greater than the minimum driving power of the engine, the power system is set to the oil-electric hybrid driving mode, the output power of the high-power-to-weight-ratio piston engine is controlled within the high-efficiency output interval of the engine, and the remaining power is provided by the bidirectional output motor; When the aircraft demand power is greater than the maximum driving power of the engine and the aircraft demand power minus the maximum output power of the bidirectional output motor is less than or equal to the minimum driving power of the engine, the power system is set to the oil-electric hybrid driving mode, the output power of the high-power-to-weight-ratio piston engine is controlled to the minimum driving power of the engine, and the remaining power is provided by the bidirectional output motor, so as to balance the high-efficiency operation of the high-power-to-weight-ratio piston engine and the matching of the aircraft demand power.

[0015] Preferably, when the state of charge of the high-energy-density battery pack is in the high-charge interval, the upper-layer control logic comprises: When the aircraft demand power is less than or equal to the maximum output power of the bidirectional output motor, the power system is set to the pure-electric driving mode, the high-energy-density battery pack supplies power to the bidirectional output motor, and the bidirectional output motor independently drives the propeller, so as to reduce the start-stop times and fuel consumption of the high-power-to-weight-ratio piston engine; When the aircraft demand power is greater than the maximum output power of the bidirectional output motor and the aircraft demand power minus the maximum output power of the bidirectional output motor is greater than the minimum driving power of the engine, the power system is set to the oil-electric hybrid driving mode, the output power of the high-power-to-weight-ratio piston engine is controlled within the high-efficiency output interval of the engine, and the difference power is provided by the bidirectional output motor; When the aircraft demand power is greater than the maximum output power of the bidirectional output motor and the aircraft demand power minus the maximum output power of the bidirectional output motor is less than or equal to the minimum driving power of the engine, the power system is set to the oil-electric hybrid driving mode, the output power of the high-power-to-weight-ratio piston engine is controlled to the minimum driving power of the engine, and the remaining power is provided by the bidirectional output motor, so as to ensure the aircraft power demand and further improve the working economy of the high-power-to-weight-ratio piston engine.

[0016] The present application discloses the following technical effects: The present application introduces the engine characteristic curve and the determination of the engine high-efficiency output interval in the flight management computer, and always takes the engine high-efficiency output interval as a constraint in power mode selection and power distribution, so that the high-power-to-weight ratio piston engine works around the high-efficiency output interval in most flight conditions. Compared with the method of rough control of the engine according to the instantaneous power demand or simple speed interval in the background technology, the present application compares and calculates the engine minimum driving curve and the engine maximum driving curve as the explicit power boundary, so that the engine avoids staying in the poor fuel economy area for a long time, reduces the fuel consumption per unit propulsion power from the system level, and improves the endurance of the oil-electric hybrid aircraft.

[0017] The present application cooperates with the airborne sensor and the flight management computer, first uniformly collects and sorts the aircraft operating state and the power system working state, and then calculates the aircraft demand power combined with the flight task and the flight condition, so as to serve as the input quantity of power mode determination. Unlike the rough control in the background technology which only uses a small number of condition parameters or fixed condition assumptions, the demand power calculation of the present application comes from the comprehensive data under the actual flight state, which can accurately reflect the resistance, load and control demand of the current flight profile, so as to realize fine matching between the pure electric drive mode, the engine direct drive mode, the oil-electric hybrid drive mode, the power generation mode and the kinetic energy recovery mode according to the working condition, and improve the responsiveness and adaptability of power output.

[0018] The present application explicitly includes the state of charge of the high-energy-density battery pack in the decision basis when selecting the power mode, so that the power mode is no longer determined by a single factor of engine condition or demand power, but is comprehensively determined by the combined relationship of "aircraft demand power-engine high-efficiency output interval-battery state of charge". Compared with the strategy of simply prohibiting pure electric mode when the power is too low, or arbitrarily using the motor when the power is sufficient in the background technology, the present application can reasonably arrange the power use and power supplement time under the premise of ensuring the safety and life of the high-energy-density battery pack, take into account the fuel consumption, battery state of charge and redundant power reserve in long-haul tasks, and improve the energy utilization efficiency and reliability of the entire oil-electric hybrid power system.

[0019] The application implements collaborative control on high power-to-weight ratio piston engines, bidirectional output motors and bidirectional generators by generating unified power mode decision instructions and power distribution instructions in a flight management computer, and realizes orderly switching and linkage between various working modes such as pure electric driving, engine direct driving, oil-electric hybrid driving, power generation and kinetic energy recovery. Compared with the scheme in the background art in which each subcomponent is controlled by an independent controller and mode switching relies on manual or simple threshold logic, the application can make mode judgment and power distribution according to the same set of basic data in one control framework, avoids hysteresis and conflicts in the mode switching process, reduces the impact caused by torque mutation and repeated energy flow switching, and thus improves the smoothness and comfort of the power system operation.

[0020] The application makes high power-to-weight ratio piston engines preferentially work in the high-efficiency output interval under the premise of meeting the aircraft demand power and high energy density battery pack state of charge constraints, not only improves fuel economy, but also reduces thermal load and mechanical stress of the engine under long-term high load or low efficiency working conditions, which is conducive to prolonging the service life and maintenance period of the engine. At the same time, the application retains the participation ability of the motor and generator under each working condition, provides additional power redundancy and energy regulation means for the aircraft, is more suitable for complex flight tasks and multi-segment flight profiles of low-altitude aircraft than the single power source or simple superposition scheme in the background art, and helps to improve the safety and reliability of task completion. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0022] Figure 1 The method flowchart provided for the embodiments of the application; Figure 2 The technical route schematic diagram provided for the embodiments of the application; Figure 3 The engine upper layer control method judgment flowchart provided for the embodiments of the application; Figure 4 The parallel oil-electric hybrid power system structure schematic diagram provided for the embodiments of the application. DETAILED DESCRIPTION

[0023] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0024] The purpose of the present application is to provide a parallel oil-electric hybrid aircraft power system control method, which coordinates the scheduling of the engine, motor and battery pack through a unified flight management calculation framework, realizes multi-mode smooth switching and optimal energy distribution, and significantly improves the comprehensive power performance and mission adaptability of the aircraft.

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 The method flowchart provided by the embodiments of the present application is shown in Figure 1 The present application provides a parallel oil-electric hybrid aircraft power system control method, which is applied to the power system of an aircraft including a high power-to-weight ratio piston engine, a bidirectional output motor, a bidirectional generator and a high energy density battery pack, and includes: The operating state of the aircraft, the working state of the power system and the state of charge of the high energy density battery pack are collected by an airborne sensor, and the operating state, the working state and the state of charge are input into a flight management computer as basic data for control calculation; According to the universal characteristic curve of the high power-to-weight ratio piston engine, the efficient output interval of the engine is determined in the flight management computer, the lowest driving curve and the highest driving curve of the engine are determined within the efficient output interval, and the efficient output interval and the lowest driving curve and the highest driving curve are used as basis parameters for power mode determination; Based on the basic data, in combination with the current flight task and flight condition of the aircraft, the aircraft demand power at the current time is calculated in the flight management computer, and the demand power is compared with the power range corresponding to the lowest driving curve and the highest driving curve of the engine, to obtain the relationship data between the demand power and the efficient output interval of the engine; According to the state of charge of the high energy density battery pack and the relationship data between the demand power and the efficient output interval of the engine, at least one power mode is selected from the pure electric driving mode, the engine direct drive mode, the oil-electric hybrid driving mode, the power generation mode and the kinetic energy recovery mode, and the corresponding power mode decision instruction is generated; According to the power mode decision instruction, a power distribution instruction is generated in the flight management computer and is sent to the high-power-to-weight ratio piston engine, the bidirectional output motor and the bidirectional generator to adjust the output power of the high-power-to-weight ratio piston engine, the output power of the bidirectional output motor and the power generation power of the bidirectional generator, so that the high-power-to-weight ratio piston engine works in the high-efficiency output interval under the premise of meeting the aircraft demand power and the high-energy-density battery pack state of charge constraint.

[0027] In the present application, the driving curve of the engine and the high-efficiency output interval are determined, and the high-efficiency output interval and the driving curve of the engine are defined by analyzing key parameters such as the engine effective fuel consumption rate, the speed, the torque and the like based on the universal characteristic curve provided by the engine manufacturer. The high-efficiency output interval corresponds to a low fuel consumption and high efficiency region, the minimum driving curve of the engine corresponds to the minimum output power curve of the engine in the high-efficiency output interval, the maximum driving curve of the engine corresponds to the maximum output power curve of the engine in the high-efficiency output interval, and the high-efficiency and stable working interval of the engine in the output state is framed by the two driving curves.

[0028] As shown in Figures 2 to 4 , the present embodiment comprises the following steps: S1, collecting the real-time state and working mode of the aircraft and the power system through the onboard sensor; S2, the flight management computer FMC identifies the current operating environment and state of the engine according to the key operating state parameters (flight speed, altitude, aerodynamic resistance and load, etc.) of the aircraft collected in real time, and calculates the demand power of the aircraft; S3, establishing the engine driving curve and the system optimal output mode varying with the actual situation; S4, the FMC judges the power mode required by the power system according to the current operating state and the whole machine control model, outputs the pre-set power mode decision, and guarantees the optimal output efficiency; S5, building the upper control logic and the bottom control logic of the parallel oil-electric hybrid aircraft.

[0029] Among them, the onboard sensor in S1 includes: aircraft sensors including flight speed measurement unit, altitude measurement unit, surface pressure measurement unit, environmental condition (temperature, humidity, etc.) collection unit, etc.; power system sensors including engine speed measurement unit, engine fuel consumption rate measurement unit, engine output power measurement unit, motor speed measurement unit, motor torque measurement unit, temperature monitoring unit, power voltage monitoring unit.

[0030] As shown in Figure 3 , the upper control logic of the parallel oil-electric hybrid aircraft in S5 includes: S500, when the aircraft power system is in non-output mode, the M1 motor enters kinetic energy recovery mode; S501, when the aircraft power system is in output state, but in engine unsuitable output state or engine unable to output, enter pure electric mode. When the aircraft power system is in output state and in engine suitable output state, including the following judgment conditions: S502, when the SOC is less than the minimum SOC limit value, and the actual demand power of the aircraft is less than the minimum driving curve of the engine, enter direct drive mode and power generation mode; S503, when the SOC is less than the minimum SOC limit value, and the actual demand power of the aircraft is greater than the minimum driving curve of the engine and less than the maximum driving curve of the engine, enter engine direct drive mode; S504, when the SOC is less than the minimum SOC limit value, and the actual demand power of the aircraft is greater than the maximum driving curve of the engine, enter engine acceleration direct drive mode; S505, when the SOC is greater than the minimum SOC limit value and less than the intermediate SOC reference value, and the actual demand power of the aircraft is less than the minimum driving curve of the engine, enter engine direct drive mode and power generation mode; S506, when the SOC is greater than the minimum SOC limit value and less than the intermediate SOC reference value, and the actual demand power of the aircraft is greater than the minimum driving curve of the engine and less than the maximum driving curve of the engine, enter engine direct drive mode; S507, when the SOC is greater than the minimum SOC limit value and less than the intermediate SOC reference value, and the actual demand power of the aircraft is greater than the maximum driving curve of the engine, if the actual demand power of the aircraft minus the maximum output power of the output motor is greater than the minimum driving power of the engine, enter hybrid mode, wherein the output power of the engine is in the optimal output interval; S508, when the SOC is greater than the minimum SOC limit value and less than the intermediate SOC reference value, and the actual demand power of the aircraft is greater than the maximum driving curve of the engine, if the actual demand power of the aircraft minus the maximum output power of the output motor is less than the minimum driving power of the engine, enter hybrid mode, wherein the output power of the engine is the minimum driving power of the engine; S509, when the SOC is greater than the intermediate SOC reference value, if the actual demand power of the aircraft is greater than the maximum output power of the motor, if the actual demand power of the aircraft minus the maximum output power of the motor is greater than the minimum driving power of the engine, enter hybrid mode, wherein the output power of the engine is in the optimal output interval; S510, when the SOC is greater than the intermediate SOC reference value, if the actual demand power of the aircraft minus the maximum output power of the motor is less than the minimum driving power of the engine, enter hybrid mode, wherein the output power of the engine is the minimum driving power of the engine.

[0031] The SOC reference value of the power supply (high-energy-density battery pack) and the engine output power in the upper-layer control of the parallel oil-electric hybrid aircraft in S5 are as follows: S521, SOClow is equal to 15% of the rated value of the power supply; S522, SOCmid is equal to 60% of the rated value of the power supply; S523, Gmin is the power corresponding to the minimum driving curve of the engine; S524, Gmax is the power corresponding to the maximum driving curve of the engine. This part can be adjusted according to the actual situation of the aircraft.

[0032] The bottom-layer control logic of the power system of the parallel oil-electric hybrid aircraft in S5 includes: S520, pure electric mode: in this mode, the engine output is 0, and only the power supply provides energy for the output motor, and the output motor outputs and drives the propeller; S521, direct drive mode: in this mode, the output motor output is 0, and only fuel is used to provide energy for the engine, and the engine output drives the propeller; S522, hybrid mode: in this mode, the engine and the output motor jointly output to drive the propeller; S523, power generation mode: this mode is only for the generator. In this mode, part of the engine output power is distributed to the generator for power generation, and the generator converts mechanical energy into electrical energy and stores it in the power supply; S524, kinetic energy recovery mode: in this mode, the demand power of the aircraft is less than 0, the output motor M1 is converted into a generator, and energy is recovered and generated, and stored in the power supply.

[0033] The method for calculating the demand power of the aircraft in S2: S21, first, the FMC receives various sensor information, including aircraft load, air density, altitude, atmospheric conditions, wing angle of attack, etc.; S22, the specific formula for calculating the power demand during flight is: In the formula: is the takeoff total mass; is the wing area; is the fuel mass consumption coefficient, i.e., the ratio of the current fuel mass to the initial fuel mass; is the flight dynamic pressure; is the zero-lift drag coefficient; is the lift-induced drag coefficient, where is the wing aspect ratio, is the Oswald factor; is the flight altitude, is the climb rate; For the flight speed; For the propeller efficiency; For the gravity acceleration; S23, according to the corresponding experience formula, the demand power size calculated in the previous step is corrected, and the power size under the current flight profile is compared to ensure the reliability of the calculation.

[0034] The engine optimal output mode selected in S3 is as follows: S331, when the engine output power is lower than the minimum driving curve of the engine, the direct drive efficiency of the engine is low, the engine should increase the output power, but the actual selection is constrained by the SOC value of the power supply and the maximum output power of the output motor (M1), if the SOC value of the power supply is lower than the intermediate reference value, the engine output state is adjusted in the optimal output interval, part of the power is used to drive the propeller, and part of the power is used to generate electricity, and the generated power B=Gmin-R, at this time the system is in direct drive mode + power generation mode; if the SOC value of the power supply is higher than the intermediate reference value, the specific output state of the generator is constrained by the rated power of the output motor, if the demand power of the aircraft is less than the rated power of the output motor, the generator is stopped, the output is 0, the motor is driven by the power supply, at this time the system is in pure electric mode; if the demand power of the aircraft is higher than the rated power of the output motor, the engine output state is adjusted in the optimal output interval, the engine output is used to drive the propeller, at this time the system is in hybrid mode.

[0035] S332, when the engine output efficiency is higher than the maximum driving curve of the engine, the fuel consumption of the engine is higher at this time, the output efficiency decreases, the engine should reduce the output power, and select a more efficient output mode, but the actual selection is constrained by the SOC value of the power supply, if the SOC value of the power supply is less than the minimum reference value, the engine still maintains the low-efficiency output state, and the system mode remains in direct drive mode, at this time the system is in direct drive mode; if the SOC value of the power supply is greater than the minimum reference value, the engine output state is adjusted in the optimal output interval, and the remaining demand power is supplemented by the output motor, at this time the system is in hybrid mode.

[0036] The power mode judgment and output decision in S4 are as follows: the airborne FMC judges the power mode required by the power system according to the current operation state of the aircraft and the whole machine control model, and makes the power mode output decision according to the pre-set power mode.

[0037] The advantages of the parallel oil-electric hybrid aircraft power system control method are: the high-efficiency output interval of the engine is determined according to the universal characteristic curve of the engine, and the minimum driving curve and the maximum driving curve are defined, the optimal mode of the power system is judged according to the engine output state and the SOC value of the power supply, so that the engine is always in the optimal output state under various working conditions, the output efficiency of the engine is improved, and the fuel consumption rate is reduced.

[0038] The various embodiments described in this specification are presented for the purpose of illustrating the principles of the present application and its best mode of operation. Each of the embodiments described in this specification has been provided for the purpose of illustration and is not intended to limit the application.

[0039] The principles and operation of the present application have been explained so far with the aid of specific examples, but it is apparent for those skilled in the art that the present application is not limited to the above examples, but can be practiced with modifications and alterations all within the scope employed. Therefore, the above description should not be interpreted as a limitation on the present application.

Claims

1. A parallel hybrid electric aircraft power system control method, applied to a power system of an aircraft comprising a high power-to-weight ratio piston engine, a bidirectional output motor, a bidirectional generator and a high energy density battery pack, characterized in that, The method comprises the following steps: Collecting the operating state of the aircraft, the working state of the power system and the state of charge of the high-energy-density battery pack through on-board sensors, and inputting the operating state, the working state and the state of charge into a flight management computer as basic data for control calculation; According to the characteristic curve of the high-power-to-weight ratio piston engine, determining the high-efficiency output interval of the engine in the flight management computer, determining the minimum driving curve and the maximum driving curve of the engine within the high-efficiency output interval, and taking the high-efficiency output interval and the minimum driving curve and the maximum driving curve as the basis parameters for power mode determination; Based on the basic data, combining the current flight task and flight condition of the aircraft, calculating the demand power of the aircraft at the current time in the flight management computer, and comparing the demand power with the power range corresponding to the minimum driving curve and the maximum driving curve of the engine to obtain the relationship data between the demand power and the high-efficiency output interval of the engine; According to the state of charge of the high-energy-density battery pack and the relationship data between the demand power and the high-efficiency output interval of the engine, selecting at least one power mode from the pure electric driving mode, the engine direct driving mode, the oil-electric hybrid driving mode, the power generation mode and the kinetic energy recovery mode, and generating corresponding power mode decision instructions; According to the power mode decision instructions, generating power distribution instructions in the flight management computer, and issuing the power distribution instructions to the high-power-to-weight ratio piston engine, the bidirectional output motor and the bidirectional generator to adjust the output power of the high-power-to-weight ratio piston engine, the output power of the bidirectional output motor and the power generation power of the bidirectional generator, so that the high-power-to-weight ratio piston engine works within the high-efficiency output interval on the premise of meeting the demand power of the aircraft and the state of charge constraint of the high-energy-density battery pack.

2. The parallel hybrid-electric aircraft power system control method of claim 1, wherein, The on-board sensors comprise aircraft state sensors and power system sensors; the aircraft state sensors are used to collect aircraft state data and input the collected aircraft state data into the flight management computer; the aircraft state data comprises flight speed, altitude, surface pressure, and environmental temperature and humidity; the power system sensors are used to collect power system state data and input the collected power system state data into the flight management computer as one of the sources of basic data for control calculation; the power system state data comprises high-power-to-weight ratio piston engine speed, engine fuel consumption, engine output power, bidirectional output motor speed, bidirectional output motor torque, power system key part temperature and high-energy-density battery pack voltage.

3. The parallel hybrid-electric aircraft power system control method of claim 1, wherein, The method for calculating the demand power of the aircraft at the current time in the flight management computer comprises the following steps: Based on the aircraft operating state in the basic data, extracting parameters related to flight power therefrom; the parameters related to flight power include aircraft load, air density, altitude, atmospheric conditions and wing angle of attack; Based on the parameter related to flight power, the power required to overcome aerodynamic drag and maintain flight during flight is calculated according to an aerodynamic relationship, and initial power requirement data during flight is obtained; The initial power requirement data is corrected according to an empirical correction model, and compared with the power range corresponding to the current flight profile. If the comparison is passed, the corrected power requirement is taken as the aircraft demand power.

4. The control method of claim 1, wherein, Determine the high-efficiency output interval of the engine in the flight management computer, and determine the engine minimum driving curve and the engine maximum driving curve in the high-efficiency output interval, comprising: Based on the universal characteristic curve provided by the engine manufacturer, analyze the effective fuel consumption rate of the high-power-to-weight ratio piston engine under different speed and torque combinations, and determine the area with low effective fuel consumption rate and high efficiency as the high-efficiency output interval of the engine; In the high-efficiency output interval of the engine, a continuous power trajectory corresponding to the lower limit of the output power along the engine speed change direction is taken as the engine minimum driving curve, and a continuous power trajectory corresponding to the upper limit of the output power along the engine speed change direction is taken as the engine maximum driving curve, and the working power range of the high-power-to-weight ratio piston engine is defined by the engine minimum driving curve and the engine maximum driving curve.

5. The control method of claim 1, wherein, In the process of power mode determination, the setting method of the state of charge interval of the high-energy-density battery pack and the engine output power interval includes: The state of charge of the high-energy-density battery pack is divided into a low charge interval, an intermediate charge interval and a high charge interval. When the state of charge of the high-energy-density battery pack is less than 15% of the rated capacity of the high-energy-density battery pack, it is considered to be in the low charge interval; when the state of charge of the high-energy-density battery pack is greater than or equal to 15% and less than 60% of the rated capacity of the high-energy-density battery pack, it is considered to be in the intermediate charge interval; when the state of charge of the high-energy-density battery pack is greater than or equal to 60% of the rated capacity of the high-energy-density battery pack, it is considered to be in the high charge interval; The output power corresponding to the engine minimum driving curve is defined as the engine minimum driving power, and the output power corresponding to the engine maximum driving curve is defined as the engine maximum driving power. The engine minimum driving power and the engine maximum driving power are used to segmentally compare the aircraft demand power in power mode determination.

6. The parallel hybrid-electric aircraft power system control method of claim 1, wherein, The bottom-layer control logic of the aircraft includes: In the pure electric drive mode, the high-power-to-weight ratio piston engine does not output power, the high-energy-density battery pack supplies power to the bidirectional output motor, the bidirectional output motor outputs power and drives the propeller through the transmission mechanism to meet the aircraft demand power; In the engine direct drive mode, the bidirectional output motor does not output power, fuel supplies power to the high-power-to-weight ratio piston engine, and the high-power-to-weight ratio piston engine outputs power and drives the propeller through the transmission mechanism. In the oil-electric hybrid driving mode, the high power-to-weight ratio piston engine and the bidirectional output motor output power simultaneously to drive the propeller, the high power-to-weight ratio piston engine provides basic power, and the bidirectional output motor provides power compensation; In the power generation mode, part of the output power of the high power-to-weight ratio piston engine is used to drive the propeller, and the other part is converted into electrical energy by the bidirectional generator and stored in the high energy density battery pack to improve the state of charge of the high energy density battery pack; In the kinetic energy recovery mode, when the demand power of the aircraft is less than zero, the bidirectional output motor is switched to the power generation state, the excess kinetic energy in the flight process is recovered through the propeller and the transmission system, the recovered mechanical energy is converted into electrical energy and stored in the high energy density battery pack.

7. The control method of claim 1, wherein, The upper layer control logic of the aircraft at least includes: When the aircraft is in gliding or working condition without the need for propulsion power, causing the power system to be in a non-output state, the power system is set to the kinetic energy recovery mode, and the bidirectional output motor recovers kinetic energy to improve the state of charge of the high energy density battery pack; When the power system is in an output state and the high power-to-weight ratio piston engine is in an unsuitable output state or the high power-to-weight ratio piston engine cannot output power, the power system is set to the pure electric driving mode, the high energy density battery pack supplies power to the bidirectional output motor, and the bidirectional output motor independently drives the propeller to meet the demand power of the aircraft.

8. The control method of claim 5, wherein, When the state of charge of the high energy density battery pack is in the low charge interval, the upper layer control logic includes: When the demand power of the aircraft is less than the minimum driving power of the engine, the power system is set to the combination of the engine direct drive mode and the power generation mode, the high power-to-weight ratio piston engine works in the high efficient output interval of the engine, and the bidirectional generator charges the high energy density battery pack to preferentially restore the state of charge of the high energy density battery pack; When the demand power of the aircraft is between the minimum driving power of the engine and the maximum driving power of the engine, the power system is set to the engine direct drive mode, and the high power-to-weight ratio piston engine independently drives the propeller in the high efficient output interval of the engine; When the demand power of the aircraft is greater than the maximum driving power of the engine, the power system is set to the engine acceleration direct drive mode, and the high power-to-weight ratio piston engine outputs power at the upper boundary of the high efficient output interval of the engine to meet the demand of high power flight working condition for propulsion power.

9. The parallel hybrid-electric aircraft power system control method of claim 5, wherein, When the state of charge of the high energy density battery pack is in the intermediate charge interval, the upper layer control logic includes: When the demand power of the aircraft is less than the minimum driving power of the engine, the power system is set to the combination of the engine direct drive mode and the power generation mode, the high power-to-weight ratio piston engine works in the high efficient output interval of the engine, and the bidirectional generator charges the high energy density battery pack; When the aircraft demand power is between the engine minimum driving power and the engine maximum driving power, the power system is set to the engine direct drive mode, and the high power-to-weight ratio piston engine independently drives the propeller in the high efficient output range of the engine; When the aircraft demand power is greater than the engine maximum driving power and the aircraft demand power minus the maximum output power of the bidirectional output motor is still greater than the engine minimum driving power, the power system is set to the hybrid drive mode, and the output power of the high power-to-weight ratio piston engine is controlled in the high efficient output range of the engine, and the bidirectional output motor provides the remaining power compensation; When the aircraft demand power is greater than the engine maximum driving power and the aircraft demand power minus the maximum output power of the bidirectional output motor is less than or equal to the engine minimum driving power, the power system is set to the hybrid drive mode, and the output power of the high power-to-weight ratio piston engine is controlled to the engine minimum driving power, and the bidirectional output motor provides the remaining power, so as to balance the high efficient operation of the high power-to-weight ratio piston engine and the matching of the aircraft demand power.

10. The control method of claim 5, wherein, When the state of charge of the high energy density battery pack is in the high state of charge range, the upper layer control logic comprises: When the aircraft demand power is less than or equal to the maximum output power of the bidirectional output motor, the power system is set to the pure electric drive mode, the high energy density battery pack supplies power to the bidirectional output motor, and the bidirectional output motor independently drives the propeller, so as to reduce the start-stop times and fuel consumption of the high power-to-weight ratio piston engine; When the aircraft demand power is greater than the maximum output power of the bidirectional output motor and the aircraft demand power minus the maximum output power of the bidirectional output motor is greater than the engine minimum driving power, the power system is set to the hybrid drive mode, and the output power of the high power-to-weight ratio piston engine is controlled in the high efficient output range of the engine, and the bidirectional output motor provides the differential power; When the aircraft demand power is greater than the maximum output power of the bidirectional output motor and the aircraft demand power minus the maximum output power of the bidirectional output motor is less than or equal to the engine minimum driving power, the power system is set to the hybrid drive mode, and the output power of the high power-to-weight ratio piston engine is controlled to the engine minimum driving power, and the bidirectional output motor provides the remaining power compensation, so as to ensure the aircraft power demand while further improving the working economy of the high power-to-weight ratio piston engine.

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