Control method for improving safety and stability of airship

Abstract

The invention discloses a control method for improving safety and stability of an airship, and belongs to the technical field of airship control. The control method for improving the safety and stability of the airship comprises the following steps that environment information and the state of the airship are collected through a sensor; whether disturbance is too large or a deflation valve and an air blower break down is judged; if yes, starting an online reconstruction method to update a planning result; if not, executing the next step; the online reconstruction method comprises a horizontal track reconstruction method when the airship flies in the air and an execution mechanism redistribution method in the airship lifting process. And tracking the planning result. According to the control method for improving the safety and stability of the airship, the flight state error and the state of the executing mechanism are detected in the operation process of the airship, airship task reconstruction is conducted on the level of horizontal track replanning and executing mechanism redistribution online, and the flight stability and safety of the airship are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of airship control, and in particular to a control method for improving the safety and stability of an airship. Background Art

[0002] An airship is a lighter-than-air aircraft that relies on solar panels for power supply. It is equipped with several independent air bags inside, each of which is equipped with several deflation valves and blowers for adjusting the internal air pressure of the air bags. The main mission space of an airship is about 20 km above the ground, which belongs to the category of near-space. Unlike other aircraft or spacecraft that require thrust or aerodynamics to generate lift, airships rely mainly on their own buoyancy to balance gravity, allowing them to stay in the working space for a long time without additional fuel supply. In addition, due to the special structural materials and working space of airships, their reflection of electromagnetic wave detection is not strong, making them difficult to be detected by radar, and there are currently few effective means of attacking near-space aircraft, so airships often have better survivability. For commonly used payloads such as sensor detection equipment, compared with heavier-than-air aircraft, airships have a higher working altitude and better ground observation vision; compared with artificial satellites in orbit, airships can achieve higher image resolution and sensor sensitivity without significantly reducing the detection coverage area. Therefore, airships currently have broad application prospects in the fields of territorial security surveillance, high-altitude intelligence reconnaissance, meteorology, disaster and resource monitoring, and long-distance communication relay.

[0003] However, these characteristics of airships also bring difficulties to the design of corresponding trajectory planning and control algorithms. The airship is large in size and can only move by electric propellers powered by solar panels, which results in very limited lateral maneuverability. If it is disturbed to a large extent during flight, it is difficult to cope with the disturbance by relying solely on the trajectory tracking control algorithm, which makes the offline trajectory planning results from the ground partially invalid. At this time, mission reconstruction is required. Although the current state of the airship can be transmitted to the ground command and control platform through information transmission for offline mission reconstruction, considering the complex network denial environment, the communication link between the airship and the ground platform is disturbed, resulting in unsmooth data transmission, making it difficult to reconstruct the airship in real time through the ground platform. In view of the disturbance and fault conditions that the airship may encounter during operation, it is urgent to study the corresponding task online reconstruction method to improve its working stability and mission success rate. Summary of the invention

[0004] The purpose of the present invention is to provide a control method for improving the safety and stability of an airship. The task online reconstruction method is divided into two parts. The first part is: when it is detected that the current flight state of the airship is too far away from the pre-planned state due to environmental disturbance, a horizontal trajectory rapid replanning method based on a simplified thermodynamic model is used; the second part is, when it is detected that some of the air valves or blowers of the airship are faulty, an actuator online redistribution strategy is used to ensure the front and rear weight balance of the airship, thereby improving the stability and safety of the airship flight.

[0005] To achieve the above object, the present invention provides a control method for improving the safety and stability of an airship, comprising the following steps: S1, collect environmental information and airship status through sensors; S2, judging whether the disturbance is too large or the bleed valve or blower fails; if it is judged to be yes, starting the online reconstruction method to update the planning result; if it is judged to be no, executing S3; The online reconstruction method includes a horizontal trajectory reconstruction method when the airship is stationary and a method for reallocating the actuators during the lifting process of the airship; S3. Track planning results.

[0006] Preferably, in S2, the horizontal trajectory reconstruction method specifically includes the following steps: S211. Establish the state equation of the airship in the horizontal direction; S212, introducing heat into the gas chamber and propeller power , design objective function; S213. Incorporating force majeure factors into the objective function, circular obstacle constraints are introduced, and control quantity constraints are introduced; S214: Obtain a horizontal trajectory replanning model.

[0007] Preferably, in S211, the state equation of the airship in the horizontal direction is: ; In the formula, The airship is in the ground coordinate system Axis coordinates, The airship is in the ground coordinate system Axis coordinates, is the speed of the airship in the horizontal plane, is the airship track deflection angle, is the wind speed at the lower edge of the ground coordinate system The size of the axis, is the wind speed at the lower edge of the ground coordinate system The size of the axis, is the total thrust of the airship, is the lower edge of the airship in the hull coordinate system The air resistance in the axial direction is is the lower edge of the airship in the hull coordinate system The additional mass coefficient in the axial direction, is the total mass of the airship, is the rate of change of the airship track deflection angle.

[0008] Preferably, in S212, the objective function is: ; In the formula, , is the objective function preference coefficient, is the amount of heat absorbed by the gas in the airship per unit time; For thrust With speed The product of represents the power of the electric propeller.

[0009] Preferably, in S213, the circular obstacle constraint is: ; In the formula, is the coordinate of the center of the circular obstacle in the ground coordinate system, is the radius of the circular obstacle; The control quantity constraint is: ; ; In the formula, is the absolute value operator, is the upper limit of thrust, is the upper limit of the yaw angle change rate.

[0010] Preferably, in S214, the horizontal trajectory replanning model is: ; In the formula, is the initial state constraint, is the terminal state constraint, is the initial moment, is the terminal moment, is the expected initial state, is the expected terminal state; is the abbreviation of the state equation of the airship in the horizontal direction, the state vector , control amount .

[0011] Preferably, the actuator reallocation method comprises the following steps: S221, input the current deflation valve of the airship, the blower fault status, the current status of the airship and the planning result; S222, detecting the current status of all air bags; if there is an air bag overpressure, opening all non-faulty deflation valves, closing all non-faulty blowers, and executing S7; otherwise, executing S223; S223. Calculate the mass regulation capability of a single blower , calculate the mass regulation capability of a single bleed valve ; The air bag mass change when all non-faulty deflation valves are closed and all non-faulty blowers are opened. n The number of deflation valves on each air bag, The air bag mass change when all non-faulty deflation valves are open and all non-faulty blowers are closed. l The number of blowers for each air bag; S224. Obtain the mass of the front airbag according to the current state of the airship The mass of the rear airbag , according to the planning results, obtain the current expected quality of the airship ;if , execute S225; otherwise, execute S226; S225, turn on the blower, close the air release valve, and Adjust the airship mass; if , turn on the normal blowers in the front half in sequence until , is the mass of the front airbag after adjustment; if , turn on the normal blowers in the second half in sequence until , is the adjusted mass of the rear air bag; after the allocation is completed, execute S227; S226, turn off the blower, open the air valve, and Adjust the airship mass; if , open the normal air release valves in the second half in sequence until ;if , open the normal air release valves in the front half in sequence until ; Allocation is completed, execute S227; S227, output the current allocation strategy of the air release valve and the blower.

[0012] Preferably, in S223, , For the The added mass of an air bag, j is the number of air bags; , For the The reduced mass of each air bag.

[0013] The advantages and positive effects of the control method for improving the safety and stability of airships described in the present invention are: 1. Compared with offline mission planning performed by a ground control station, the online mission reconstruction method proposed in the present invention has lower requirements on the stability of the communication link and better real-time performance.

[0014] 2. The task online reconstruction method proposed in the present invention responds to environmental disturbances and airship system failures from two aspects: rapid replanning of horizontal trajectories and reallocation of actuators, thereby enhancing the safety and stability of the airship system.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of an embodiment of the present invention; Figure 2 Schematic diagram of airship instability according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0018] Example like Figure 1 A control method for improving the safety and stability of an airship comprises the following steps: S1. Collect environmental information and airship status through sensors.

[0019] S2. Determine whether the disturbance is too large or whether the bleed valve or blower fails through the airship's own control system; if it is, start the online reconstruction method to update the planning result; if it is not, execute S3.

[0020] The online reconstruction method includes a horizontal trajectory reconstruction method when the airship is stationary and a actuator reallocation method during the airship's ascent and descent.

[0021] When the airship detects that the current flight state of the airship is too far away from the pre-planned state due to environmental disturbance, a horizontal trajectory rapid replanning method based on a simplified thermodynamic model is proposed.

[0022] The horizontal trajectory reconstruction method specifically includes the following steps: S211. Establish the state equation of the airship in the horizontal direction.

[0023] Considering that the airship is in the stationary phase, the altitude of the airship remains basically unchanged, and the airship mainly performs small maneuvers in the horizontal plane through the electric propeller powered by the solar panels. In order to meet the real-time requirements of the online replanning of the horizontal trajectory, the following assumptions are made: 1. Only the horizontal movement of the airship is considered, and the vertical movement, roll, pitch and other attitude changes are ignored.

[0024] 2. The gas pressure inside the capsule depends on the heating of the gas. Taking the heating of the gas as the optimization objective function can simplify the thermodynamic characteristics of the airship and reduce the complexity of the model.

[0025] According to the above assumptions, the state vector , control amount , the state equation of the airship in the horizontal direction is obtained as: ; In the formula, The airship is in the ground coordinate system Axis coordinates, The airship is in the ground coordinate system Axis coordinates, is the speed of the airship in the horizontal plane, is the airship track deflection angle, is the wind speed at the lower edge of the ground coordinate system The size of the axis, is the wind speed at the lower edge of the ground coordinate system The size of the axis, is the total thrust of the airship, is the lower edge of the airship in the hull coordinate system The air resistance in the axial direction is is the lower edge of the airship in the hull coordinate system The additional mass coefficient in the axial direction, is the total mass of the airship, is the rate of change of the airship track deflection angle.

[0026] To facilitate the description of the optimization problem later, the above state equation is abbreviated as .

[0027] Since the present invention mainly studies the trajectory planning of the airship rather than the control problem, the airship track angle change rate is used as a control variable in the optimization problem instead of the rudder angle, thereby further reducing the complexity of the model.

[0028] S212, introducing heat into the gas chamber and propeller power , design the objective function.

[0029] The design of the objective function needs to take into account the motion characteristics of the airship. When the airship is in the hovering phase, the altitude remains basically unchanged, and usually no air intake or exhaust operations are performed. The pressure difference between the inside and outside of the capsule mainly depends on the gas pressure inside the capsule, and the key factor affecting the gas pressure inside the capsule is the heating of the gas. Since Assumption 2 no longer considers the thermodynamic model of the airship, in order to ensure the safety of the airship, it is necessary to introduce the heat of the gas inside the capsule into the objective function design. In addition, the electric propellers of the airship are powered by solar panels, so the propeller power needs to be introduced into the objective function. In summary, when performing online replanning of the horizontal trajectory, in order to minimize the heat of the airship's airbag gas and the energy consumed by the electric propeller, the objective function of the optimization problem is designed as follows: ; In the formula, , is the objective function preference coefficient, is the amount of heat absorbed by the gas in the airship per unit time; For thrust With speed The product of represents the power of the electric propeller.

[0030] S213. In combination with force majeure factors, circular obstacle constraints are introduced into the objective function, and control quantity constraints are introduced.

[0031] Due to force majeure factors, airships are sometimes not allowed to enter certain areas when performing missions. For this reason, circular obstacle constraints are introduced into the optimization problem.

[0032] The circular obstacle constraints are: ; In the formula, is the coordinate of the center of the circular obstacle in the ground coordinate system, is the radius of the circular obstacle.

[0033] At the same time, considering the limited thrust of the electric propeller and the limited rate of change of the yaw angle, control quantity constraints are introduced.

[0034] The control quantity constraint is: ; ; In the formula, is the absolute value operator, is the upper limit of thrust, is the upper limit of the yaw angle change rate.

[0035] S214: Obtain a horizontal trajectory replanning model.

[0036] The horizontal trajectory replanning method based on the simplified model of level flight can be described as the following nonlinear optimization problem: ; In the formula, is the initial state constraint, is the terminal state constraint, is the initial moment, is the terminal moment, is the expected initial state, is the expected terminal state.

[0037] S3. Track planning results.

[0038] When it is detected that the current state of the airship deviates too much from the pre-planned flight state or force majeure causes the offline trajectory planning result to become invalid, the onboard computing resources can be used to solve the above nonlinear optimization problem online and perform trajectory replanning.

[0039] like Figure 2 As shown. When the airship is in the ascending or descending stage, it is often necessary to adjust the height of the airship by regulating the bleed valve and the blower to inhale and exhaust. However, once the airship encounters an emergency of partial bleed valve or blower failure during flight, maintaining the original control logic may cause the front and rear mass of the airship to be unbalanced, thereby causing serious instability of the airship's attitude. Therefore, it is necessary to design an online reallocation strategy of the actuator that takes into account the fault information, and ensure the front and rear mass balance of the airship as much as possible under the premise of meeting the safety constraint of the internal and external safety pressure difference, thereby enhancing the attitude stability of the airship.

[0040] The actuator reallocation method comprises the following steps: S221, input the current air vent valve of the airship, the blower fault status, the current status of the airship and the planning result.

[0041] S222, check the current status of all air bags. If any air bag is over-pressurized, open all non-faulty deflation valves, close all non-faulty blowers, and execute S7. Otherwise, execute S223.

[0042] S223. Calculate the mass regulation capability of a single blower , calculate the mass regulation capability of a single bleed valve ; The air bag mass change when all non-faulty deflation valves are closed and all non-faulty blowers are opened. n The number of deflation valves on each air bag, The air bag mass change when all non-faulty deflation valves are open and all non-faulty blowers are closed. The number of blowers for each air bag.

[0043] , For the The added mass of an air bag, j is the number of air bags. , For the The reduced mass of each air bag.

[0044] In this embodiment, five air bags are provided, and each air bag is provided with two deflation valves and two blowers. , The mass adjustment capabilities of a single blower and a single bleed valve are and .

[0045] S224. Obtain the mass of the front airbag according to the current state of the airship The mass of the rear airbag The front and rear halves of the airship are divided by the center of gravity of the airship. The front half is the front half, and the rear half is the rear half. Get the current expected mass of the airship based on the planning results Expected quality It is the airship quality planning based on the current ascent or descent requirements of the airship.

[0046] if , execute S225; otherwise, execute S226; S225, now you need to increase the mass of the airship. Turn on the blower, close the air release valve, and Adjust the mass of the airship. Increase the mass of the airship while ensuring the balance of the airship, and adopt the following blower allocation strategy: If , combined with the blower fault status, turn on the first half of the normal blowers in sequence until , is the mass of the front airbag after adjustment. , turn on the normal blowers in the second half in sequence until , The mass of the rear air bag after adjustment is completed, and S227 is executed.

[0047] S226, now it is necessary to reduce the mass of the airship. Turn off the blower, open the air valve, and Adjust the mass of the airship. If , combined with the bleed valve failure state, open the normal bleed valves in the second half in sequence until .if , open the normal air release valves in the front half in sequence until . Allocation is completed, and S227 is executed.

[0048] S227, the program ends and the current allocation strategy of the air release valve and the blower is output.

[0049] Therefore, the control method for improving the safety and stability of the airship according to the present invention is adopted to detect the flight state error and the actuator state during the operation of the airship, and to perform the airship mission reconstruction online at the level of horizontal trajectory replanning and actuator reallocation, so as to improve the flight stability and safety of the airship.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A control method for improving the safety and stability of an airship, characterized in that: The following steps are involved: S1, collect environmental information and airship status through sensors; S2, judging whether the disturbance is too large or the bleed valve or blower fails; if it is judged to be yes, starting the online reconstruction method to update the planning result; if it is judged to be no, executing S3; The online reconstruction method includes a horizontal trajectory reconstruction method when the airship is stationary and a method for reallocating the actuators during the lifting process of the airship; S3. Track planning results.

2. A control method for improving the safety and stability of an airship according to claim 1, characterized in that: In S2, the horizontal trajectory reconstruction method specifically includes the following steps: S211. Establish the state equation of the airship in the horizontal direction; S212, introducing heat into the gas chamber and propeller power , design objective function; S213. Incorporating force majeure factors into the objective function, circular obstacle constraints are introduced, and control quantity constraints are introduced; S214: Obtain a horizontal trajectory replanning model.

3. A control method for improving the safety and stability of an airship according to claim 2, characterized in that: In S211, the state equation of the airship in the horizontal direction is: ； In the formula, The airship is in the ground coordinate system Axis coordinates, The airship is in the ground coordinate system Axis coordinates, is the speed of the airship in the horizontal plane, is the airship track deflection angle, is the wind speed at the lower edge of the ground coordinate system The size of the axis, is the wind speed at the lower edge of the ground coordinate system The size of the axis, is the total thrust of the airship, is the lower edge of the airship in the hull coordinate system The air resistance in the axial direction is is the lower edge of the airship in the hull coordinate system The additional mass coefficient in the axial direction, is the total mass of the airship, is the rate of change of the airship track deflection angle.

4. A control method for improving the safety and stability of an airship according to claim 3, characterized in that: In S212, the objective function is: ； In the formula, , is the objective function preference coefficient, is the amount of heat absorbed by the gas in the airship per unit time; For thrust With speed The product of represents the power of the electric propeller.

5. A control method for improving the safety and stability of an airship according to claim 4, characterized in that: In S213, the circular obstacle constraint is: ； In the formula, is the coordinate of the center of the circular obstacle in the ground coordinate system, is the radius of the circular obstacle; The control quantity constraint is: ； ； In the formula, is the absolute value operator, is the upper limit of thrust, is the upper limit of the yaw angle change rate.

6. A control method for improving the safety and stability of an airship according to claim 5, characterized in that: In S214, the horizontal trajectory replanning model is: ； In the formula, is the initial state constraint, is the terminal state constraint, is the initial moment, is the terminal moment, is the expected initial state, is the expected terminal state; is the abbreviation of the state equation of the airship in the horizontal direction, the state vector , control amount .

7. A control method for improving the safety and stability of an airship according to claim 6, characterized in that: The actuator reallocation method comprises the following steps: S221, input the current air release valve of the airship, the blower fault status, the current status of the airship and the planning result; S222, detecting the current status of all air bags; if there is an air bag overpressure, opening all non-faulty deflation valves, closing all non-faulty blowers, and executing S7; otherwise, executing S223; S223. Calculate the mass regulation capability of a single blower , calculate the mass regulation capability of a single bleed valve ; The air bag mass change when all non-faulty deflation valves are closed and all non-faulty blowers are opened. n The number of deflation valves on each air bag, The air bag mass change when all non-faulty deflation valves are open and all non-faulty blowers are closed. The number of blowers for each air bag; S224. Obtain the mass of the front airbag according to the current state of the airship The mass of the rear airbag , according to the planning results, obtain the current expected quality of the airship ;if , execute S225; otherwise, execute S226; S225, turn on the blower, close the air release valve, and Adjust the airship mass; if , turn on the normal blowers in the front half in sequence until , is the mass of the front airbag after adjustment; if , turn on the normal blowers in the second half in sequence until , is the adjusted mass of the rear air bag; after the allocation is completed, execute S227; S226, turn off the blower, open the air valve, and Adjust the airship mass; if , open the normal air release valves in the second half in sequence until ;if , open the normal air release valves in the front half in sequence until ; Allocation is completed, execute S227; S227, output the current allocation strategy of the air release valve and the blower.

8. A control method for improving the safety and stability of an airship according to claim 7, characterized in that: In the S223, , For the The added mass of an air bag, j is the number of air bags; , For the The reduced mass of each air bag.

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