A flapping / gliding control method for a flapping-wing aircraft based on the PX4 flight control system

Abstract

The present invention discloses a flapping / gliding control method for a flapping-wing aircraft based on a PX4 flight control system, belonging to the field of flapping-wing aircraft flight control technology. The method comprises the following steps: a. setting a flapping / gliding switching altitude threshold X and a flapping / gliding switching altitude threshold Y for the flapping-wing aircraft; b. detecting whether an updraft exists in the flapping-wing aircraft's flight area; a) obtaining the flapping-wing aircraft's potential energy and kinetic energy; b) calculating the aircraft's specific energy change rate; c) determining whether an updraft exists in the flight area; and c) during the flight of the flapping-wing aircraft, when an updraft is detected in the flight area, the flight control system controls the flapping-wing aircraft to enter a flapping / gliding cyclic flight state. The method has the advantages of low energy consumption and long flight time.

Description

Technical Field

[0001] The present invention relates to the technical field of flapping-wing aircraft flight control. Background Art

[0002] Birds in nature soar by leveraging updrafts, reducing the number of wing flaps required to conserve energy. Bird-like flapping-wing aircraft mimicking bird flight have limited energy capacity and therefore need to conserve energy as much as possible during mission execution. If a bird-like flapping-wing aircraft could detect updrafts in the mission area and utilize them to maintain altitude and glide, reducing flapping frequency, it would significantly reduce energy consumption and extend flight time.

[0003] Currently, bird-like flapping-wing aircraft that can switch between flapping mode and gliding mode are all operated by operators through remote control. Their flight control systems cannot automatically complete the switch between flapping mode and gliding mode, and therefore cannot effectively utilize rising air currents to improve flight efficiency. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a flapping / sliding control method for a flapping-wing aircraft based on a PX4 flight control system, which has the characteristics of low energy consumption and long flight time.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A flapping / sliding control method for a flapping-wing aircraft based on a PX4 flight control system, the method being based on support for the PX4 flight control system and comprising the following steps:

[0007] a. Setting a flapping-wing aircraft sliding / flapping switching height threshold X and a flapping / sliding switching height threshold Y, the sliding / flapping switching height threshold X is determined according to the performance of the flapping-wing aircraft, which is a safe height for the flapping-wing aircraft to switch from a gliding state to a flapping state, so as to avoid a crash of the flapping-wing aircraft due to a gliding altitude that is too low; the flapping / sliding switching height threshold Y is determined according to the performance of the flapping-wing aircraft, which is the height at which the flapping-wing aircraft switches from a flapping state to a gliding state; the height difference between the flapping / sliding switching height threshold Y and the sliding / flapping switching height threshold X causes the flapping-wing aircraft to have potential energy on the basis of its kinetic energy of flight, so that the flapping-wing aircraft glides in the space region between the flapping / sliding switching height threshold Y and the sliding / flapping switching height threshold X;

[0008] b. Detect whether there is an updraft in the flapping-wing aircraft's flight area. The updraft detection steps are as follows:

[0009] a) Obtain the potential energy and kinetic energy of the flapping-wing aircraft. Collect the signal detection output values of the altitude sensor and airspeed sensor, and obtain the potential energy and kinetic energy of the aircraft according to the following formula:

[0010] E p =mgh (1)

[0011]

[0012] The total energy can be expressed as:

[0013] E t =E p +E k (3)

[0014] The total energy is normalized by weight, and the specific energy can be expressed as:

[0015]

[0016] Where: E p is the current gravitational potential energy of the aircraft, in J; E k is the current kinetic energy of the aircraft, in J; E t E is the current total energy of the aircraft, in J; ts is the specific energy of the aircraft, in m; m is the mass of the aircraft, in kg; g is the acceleration due to gravity, in m / s 2 ;h is the current flight altitude of the aircraft, in meters; v t The current true airspeed of the aircraft, in m / s;

[0017] b) Calculate the specific energy change rate of the aircraft itself (in m / s) and derive formula (3):

[0018]

[0019] Where: P s is the specific energy change rate, unit is m / s; is the rate of change of altitude, in m / s; is the true airspeed change rate, in m / s 2 ;

[0020] c) Determine whether there is an updraft in the flight area:

[0021] The energy change rate of the aircraft itself can be expressed by external factors:

[0022] P s =P s,drag +P s,propulsive +p s,updraft (6)

[0023] Where: P s,dragIt is the specific power consumed by the aircraft to overcome the resistance during flight, which is approximately equivalent to the aircraft's sinking rate, in m / s; P s,propulsive The specific power contributed by the aircraft's own power system, in m / s; P s,updraft It is the specific power contributed by the updraft to the change of the aircraft's energy state, which can be equivalent to the updraft wind speed, in m / s;

[0024] Then, the contribution of updraft to the change of aircraft energy state can be expressed as:

[0025]

[0026] When P s,updraft When P > 0, there is an updraft in the aircraft's flight area; s,updraft When ≤0, there is no updraft in the aircraft's flight area;

[0027] c. During the flight of the flapping-wing aircraft, when it is detected that there is an updraft in the flight area, the flight control system controls the flapping-wing aircraft to enter a flapping / gliding cyclic flight state: the flight control system controls the flapping-wing aircraft to flap upward at a certain angle of attack; when the altitude sensor detects that the flight altitude reaches the flapping / gliding switching altitude threshold Y, the flight control system controls the flapping-wing aircraft to be converted into a gliding state; after the flapping-wing aircraft glides forward for a distance, when the altitude sensor detects that the flight altitude drops to the gliding / flapping switching altitude threshold X, the flight control system controls the flapping-wing aircraft to enter a flapping flight state, causing the flapping-wing aircraft to flap upward at a certain angle of attack; when the altitude sensor detects that the flight altitude reaches the flapping / gliding switching altitude threshold Y, the flight control system controls the flapping-wing aircraft to be converted into a gliding state, and the above-mentioned actions are repeated in a cycle so that the flapping-wing aircraft operates in the flapping and gliding cyclic flight state; when a stop flapping / gliding cyclic flight state signal sent by the ground station is received or when it is detected that there is no updraft in the flight area of the flapping-wing aircraft, the flapping-wing aircraft stops the flapping / gliding cyclic flight state.

[0028] The present invention is further improved in that:

[0029] In the formula Medium, high change rate The method of building a first-in-first-out queue is adopted to call the altitude data measured by the flight control. By building a first-in-first-out queue, the altitude data within a fixed time window is stored. The altitude values at the head and tail of the queue are selected to obtain the difference and divide it by the time length corresponding to the queue length to obtain the rate of change of specific potential energy.

[0030] When the flapping-wing aircraft enters the flapping / gliding cycle flight state, the flight control system controls the flapping-wing aircraft to fly to the flapping / gliding switching height threshold Y with an angle of attack of 18 degrees to 23 degrees;

[0031] The throttle curve of the flight control system when the flapping-wing aircraft switches from the flapping state to the gliding state is y = 60-t 2 ;

[0032] Where: y is the throttle value; t is the time;

[0033] The throttle curve of the flapping-wing aircraft when the flight control system switches from the gliding state to the flapping state is y=11t 2 ;

[0034] Where: y is the throttle value; t is time.

[0035] The airspeed sensor uses the SPD31 digital differential pressure sensor; the altitude sensor uses the MS5611 air pressure sensor.

[0036] The beneficial effects of adopting the above technical solution are:

[0037] The present invention enables a flapping-wing aircraft to automatically detect whether there is an updraft in the flight area during flight. When an updraft is detected in the flight area, the flapping-wing aircraft is switched to a flapping / gliding cycle flight state to fully utilize the energy contained in the updraft, thereby reducing energy consumption and increasing flight time.

[0038] It has the characteristics of low energy consumption and long battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A curve of power consumption for a flapping-wing aircraft flying in a flapping / gliding cycle mode to complete a flight;

[0040] Figure 2 The power curve of a flapping-wing aircraft flying in flapping mode to complete the flight distance is shown;

[0041] Figure 3 It is a curve graph of the updraft intensity within the flight area. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] A flapping / gliding control method for a flapping-wing aircraft based on the PX4 flight control system is disclosed. The control system hardware uses a miniaturized Pixracer R15 flight controller. The accompanying battery, airspeed recorder, GPS module, power module, remote controller receiver, and data transmission are all connected to the flight controller in a conventional manner. The method is secondary developed based on the PX4 flight control architecture, integrating a flapping / gliding control module into its operating system process queue. The method includes the following steps:

[0044] a. Setting a flapping-wing aircraft sliding / flapping switching height threshold X and a flapping / sliding switching height threshold Y, the sliding / flapping switching height threshold X is determined according to the performance of the flapping-wing aircraft, which is a safe height for the flapping-wing aircraft to switch from a gliding state to a flapping state, so as to avoid a crash of the flapping-wing aircraft due to a gliding altitude that is too low; the flapping / sliding switching height threshold Y is determined according to the performance of the flapping-wing aircraft, which is the height at which the flapping-wing aircraft switches from a flapping state to a gliding state; the height difference between the flapping / sliding switching height threshold Y and the sliding / flapping switching height threshold X causes the flapping-wing aircraft to have potential energy on the basis of its kinetic energy of flight, so that the flapping-wing aircraft glides in the space region between the flapping / sliding switching height threshold Y and the sliding / flapping switching height threshold X;

[0045] b. Detect whether there is an updraft in the flapping-wing aircraft's flight area. The updraft detection steps are as follows:

[0046] a) Obtain the potential energy and kinetic energy of the flapping-wing aircraft. Collect the signal detection output values of the altitude sensor and airspeed sensor, and obtain the potential energy and kinetic energy of the aircraft according to the following formula:

[0047] E p =mgh (1)

[0048]

[0049] The total energy can be expressed as:

[0050] E t =E p +E k (3)

[0051] The total energy is normalized by weight, and the specific energy can be expressed as:

[0052]

[0053] Where: E p is the current gravitational potential energy of the aircraft, in J; E k is the current kinetic energy of the aircraft, in J; E t E is the current total energy of the aircraft, in J; ts is the specific energy of the aircraft, in m; m is the mass of the aircraft, in kg; g is the acceleration due to gravity, in m / s 2 ;h is the current flight altitude of the aircraft, in meters; v t The current true airspeed of the aircraft, in m / s;

[0054] b) Calculate the specific energy change rate of the aircraft itself (in m / s) and derive formula (3):

[0055]

[0056] Where: P s is the specific energy change rate, unit is m / s; is the rate of change of altitude, in m / s; is the true airspeed change rate, in m / s 2 ;

[0057] c) Determine whether there is an updraft in the flight area:

[0058] The energy change rate of the aircraft itself can be expressed by external factors:

[0059] P s =P s,drag +P s,propulsive +p s,updraft (6)

[0060] Where: P s,drag It is the specific power consumed by the aircraft to overcome the resistance during flight, which is approximately equivalent to the aircraft's sinking rate, in m / s; P s,propulsive The specific power contributed by the aircraft's own power system, in m / s; P s,updraft It is the specific power contributed by the updraft to the change of the aircraft's energy state, which can be equivalent to the updraft wind speed, in m / s;

[0061] Then, the contribution of updraft to the change of aircraft energy state can be expressed as:

[0062]

[0063] When P s,updraft When P > 0, there is an updraft in the aircraft's flight area; s,updraft When ≤0, there is no updraft in the aircraft's flight area;

[0064] When the flapping-wing aircraft is in cruise flight, the specific energy rate is only related to It is related to the vertical speed of the aircraft. Therefore, when the rate of change of the aircraft's specific energy increases, it indicates that an updraft has been generated.

[0065] c. During the flight of a flapping-wing aircraft, when an updraft is detected in the flight area, the flight control system controls the flapping-wing aircraft to enter a flapping / gliding cycle flight state: the flight control system controls the flapping-wing aircraft to flap upward at a certain angle of attack. When the altitude sensor detects that the flight altitude reaches the flapping / gliding switching altitude threshold Y, the flapping / gliding control module controls the motor according to the designed throttle curve to gradually reduce the flapping frequency of the aircraft. When the flapping frequency is reduced to the set value, the flight control system sends a PWM signal to drive the gear locking servo to lock the flapping wings (according to the existing technology). The aircraft enters the gliding state from the flapping state. When the flapping-wing aircraft slides forward, the aircraft enters the gliding state. After soaring for a certain distance, when the altitude sensor detects that the flight altitude has dropped to the gliding / flapping switching altitude threshold X, the flight control system controls the flapping-wing aircraft to enter the flapping flight state, causing the flapping-wing aircraft to flap upward at a certain angle of attack. When the altitude sensor detects that the flight altitude has reached the flapping / gliding switching altitude threshold Y, the flight control system controls the flapping-wing aircraft to switch to the gliding state. The above actions are repeated in a cycle, so that the flapping-wing aircraft operates in a flapping and gliding cycle state. When the flapping-wing aircraft receives a signal from the ground station to stop the flapping / gliding cycle flight state or detects that there is no updraft in the flight area of the flapping-wing aircraft, the flapping-wing aircraft stops the flapping / gliding cycle flight state.

[0066] In the formula Medium, high change rate The method of building a first-in-first-out queue is adopted. The altitude data measured by the flight control is called. By building a first-in-first-out queue, the altitude data within a fixed time window is stored. The altitude values at the head and tail of the queue are selected to obtain the difference and divide it by the time length corresponding to the queue length to obtain the rate of change of the potential energy. This method obtains smoother results.

[0067] When the flapping-wing aircraft enters the flapping / gliding cycle flight state, the flight control system controls the flapping-wing aircraft to fly to the flapping / gliding switching height threshold Y with an angle of attack of 20 degrees;

[0068] The throttle curve of the flight control system when the flapping-wing aircraft switches from the flapping state to the gliding state is y = 60-t 2 ;

[0069] Where: y is the throttle value; t is the time;

[0070] The throttle curve of the flapping-wing aircraft when the flight control system switches from the gliding state to the flapping state is y=11t 2 ;

[0071] Where: y is the throttle value; t is time.

[0072] The airspeed sensor uses the SPD31 digital differential pressure sensor, which has a pressure measurement range of ±500Pa and a maximum measurable airspeed of approximately 25m / s. The maximum flight speed of a flapping-wing aircraft is generally 15m / s, which meets the speed requirements of a flapping-wing aircraft and provides more accurate measurements. The altitude sensor uses the MS5611 air pressure sensor.

[0073] Comparative test

[0074] See also Figures 1 to 3 The experimental site temperature was 30°C, the weather was clear, and there was an updraft in the flight area. Two identical flapping-wing aircraft were used for the comparative test. Each aircraft had a takeoff weight of 200g, a wingspan of 0.2m, and a cruising speed of 11m / s. Flapping-wing aircraft A flew in a flapping / gliding cycle, while flapping-wing aircraft B flew in a flapping mode.

[0075] Both flapping-wing aircraft took off using hand-throw remote control. Flapping-wing aircraft A and flapping-wing aircraft B took off simultaneously. The two flapping-wing aircraft climbed to a target altitude of 50 meters, with a total route distance of 3800 meters. When the two aircraft climbed to 15 meters, they switched to mission (automatic flight) mode and flew automatically according to the planned mission.

[0076] Figure 1 The power consumption curve of flapping-wing aircraft A after completing the flight is shown in Figure 2. The flapping-wing aircraft A adopts a flapping / gliding cycle mode. The flapping / gliding switching height threshold Y is set to 50m, and the gliding / flapping switching height threshold X is set to 30m. Figure 1 It can be seen that when flapping-wing aircraft A climbs to the flapping / gliding switching threshold Y, it switches from the flapping state to the gliding state; when gliding to the gliding / flapping switching threshold X, it switches from the gliding state to the flapping state. Flapping-wing aircraft A takes 412 seconds to complete the flight and consumes 8860.5 J of energy.

[0077] Figure 2 The power curve of flapping-wing aircraft B after completing the flight is shown in Figure 2. The flapping-wing aircraft B adopts flapping mode to fly. Figure 2 It can be seen that the flapping-wing aircraft B took 362 seconds to complete the flight and consumed 9576J of energy.

[0078] Figure 3 FIG. 1 is a curve diagram of the updraft intensity within the flight area of the two flapping-wing aircraft detected by flapping-wing aircraft A. FIG.

[0079] From this experiment, it can be concluded that the energy consumed by flapping-wing aircraft A is 7.472% less than that consumed by flapping-wing aircraft B.

[0080] This proves that when there is an updraft in the flight area, the flapping-wing aircraft adopts a flapping / gliding cycle flight state, which can fully utilize the energy contained in the updraft, thereby reducing energy consumption and increasing flight time.

Claims

1. A flapping / sliding control method for a flapping-wing aircraft based on a PX4 flight control system, characterized by: The method is based on the PX4 flight control system and includes the following steps: a. Setting a flapping / gliding switching altitude threshold X and a flapping / gliding switching altitude threshold Y for a flapping-wing aircraft, wherein the flapping / gliding switching altitude threshold X is determined based on the performance of the flapping-wing aircraft and is a safe altitude for the flapping-wing aircraft to transition from a gliding state to a flapping state, thereby preventing the flapping-wing aircraft from crashing due to a gliding altitude that is too low; the flapping / gliding switching altitude threshold Y is determined based on the performance of the flapping-wing aircraft and is the altitude at which the flapping-wing aircraft transitions from a flapping state to a gliding state; the height difference between the flapping / gliding switching altitude threshold Y and the flapping / gliding switching altitude threshold X provides the flapping-wing aircraft with potential energy in addition to its kinetic energy for flight, thereby allowing the flapping-wing aircraft to glide in the spatial region between the flapping / gliding switching altitude threshold Y and the flapping / gliding switching altitude threshold X; b. Detecting whether there is an updraft in the flapping-wing aircraft flight area, the updraft detection steps are as follows: a) Obtain the potential energy and kinetic energy of the flapping-wing aircraft. Collect the signal detection output values of the altitude sensor and airspeed sensor, and obtain the potential energy and kinetic energy of the aircraft according to the following formula: E p =mgh (1) The total energy can be expressed as: AND t =And p +E k (3) The total energy is normalized by weight, and the specific energy is expressed as: Where: E p is the current gravitational potential energy of the aircraft, in J; E k is the current kinetic energy of the aircraft, in J; E t E is the current total energy of the aircraft, in J; ts is the specific energy of the aircraft, in m; m is the mass of the aircraft, in kg; g is the acceleration due to gravity, in m / s 2 ;h is the current flight altitude of the aircraft, in meters; v t The current true airspeed of the aircraft, in m / s; b) Calculate the specific energy change rate of the aircraft itself in m / s and derive formula (3): Where: P s is the specific energy change rate, unit is m / s; is the rate of change of altitude, in m / s; is the true airspeed change rate, in m / s 2 ; c) Determine whether there is an updraft in the flight area: The energy change rate of the aircraft itself is expressed by external factors: Where: P s,drag It is the specific power consumed by the aircraft to overcome the resistance during flight, which is approximately equivalent to the aircraft's sinking rate, in m / s; P s,propulsive The specific power contributed by the aircraft's own power system, in m / s; P s,updraft It is the specific power contributed by the updraft to the change of the aircraft's energy state, which can be equivalent to the updraft wind speed, in m / s; Then, the contribution of the updraft to the change in the energy state of the aircraft is expressed as: When P s,updraft When P > 0, there is an updraft in the aircraft's flight area; s,updraft When ≤0, there is no updraft in the aircraft's flight area; c. During the flight of the flapping-wing aircraft, when it is detected that there is an updraft in the flight area, the flight control system controls the flapping-wing aircraft to enter a flapping / gliding cyclic flight state: the flight control system controls the flapping-wing aircraft to flap upwards at a certain angle of attack; when the altitude sensor detects that the flight altitude reaches the flapping / gliding switching altitude threshold Y, the control flapping-wing aircraft is converted into a gliding state; after the flapping-wing aircraft glides forward for a distance, when the altitude sensor detects that the flight altitude drops to the described gliding / flapping switching altitude threshold X, the flight control system controls the flapping-wing aircraft to enter a flapping flight state, so that the flapping-wing aircraft flaps upwards at a certain angle of attack; when the altitude sensor detects that the flight altitude reaches the flapping / gliding switching altitude threshold Y, the control flapping-wing aircraft is converted into a gliding state, and the above-mentioned actions are repeated in a cycle so that the flapping-wing aircraft works under the flapping and gliding cyclic flight state; when the flapping-wing aircraft receives a stop flapping / gliding cyclic flight state signal sent by the ground station or detects that there is no updraft in the flight area of the flapping-wing aircraft, the flapping-wing aircraft stops the flapping / gliding cyclic flight state.

2. The flapping / sliding control method for a flapping-wing aircraft based on a PX4 flight control system according to claim 1, characterized in that: In the formula Medium, high change rate The method of building a first-in-first-out queue is adopted to call the altitude data measured by the flight control. By building a first-in-first-out queue, the altitude data within a fixed time window is stored. The altitude values at the head and tail of the queue are selected to obtain the difference and divide it by the time length corresponding to the queue length to obtain the rate of change of specific potential energy.

3. The flapping / sliding control method for a flapping-wing aircraft based on a PX4 flight control system according to claim 2, characterized in that: When the flapping-wing aircraft enters a flapping / gliding cyclic flight state, the flight control system controls the flapping-wing aircraft to fly to a flapping / gliding switching height threshold Y with an angle of attack of 18 degrees to 23 degrees; The throttle curve of the flight control system when the flapping-wing aircraft switches from the flapping state to the gliding state is y = 60-t 2 ; Where: y is the throttle value; t is the time; The throttle curve of the flapping-wing aircraft when the flight control system switches from the gliding state to the flapping state is y=11t 2 ; Where: y is the throttle value; t is time.

4. The flapping / sliding control method for a flapping-wing aircraft based on a PX4 flight control system according to claim 2 or 3, characterized in that: The airspeed sensor adopts the SPD31 digital differential pressure sensor; the altitude sensor adopts the MS5611 air pressure sensor.

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