Longitudinal track control method for unmanned aerial vehicle with high aspect ratio

Abstract

The invention relates to the technical field of unmanned aerial vehicle control, in particular to a longitudinal track control method for a high-aspect-ratio unmanned aerial vehicle. The method comprises the steps that an elevator control channel of the unmanned aerial vehicle adopts a pitch angle control strategy to adjust an elevator to control the pitch angle of the unmanned aerial vehicle, so that the flight speed of the unmanned aerial vehicle is controlled; a power channel of the unmanned aerial vehicle controls the rotating speed of a propeller of the unmanned aerial vehicle through an energy control strategy, so that the flight height is controlled; the unmanned aerial vehicle decouples an elevator control channel and a power channel by adopting a longitudinal control strategy, so that longitudinal cooperative control of the unmanned aerial vehicle is completed; the longitudinal control strategy specifically comprises the steps that a speed instruction in an elevator control channel and a lifting speed instruction in a power channel serve as balancing points, and a pitch angle feed-forward value is obtained through force and moment balance and used for adjusting the pitch angle of the unmanned aerial vehicle; according to the invention, speed control and height control are mutually independent and accurate, and the overall reliability of longitudinal track cooperative control is ensured.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) control technology, specifically to a longitudinal trajectory control method for a high aspect ratio UAV. Background Technology

[0002] Currently, fixed-wing UAVs are widely used in surveying, inspection, and reconnaissance, and long-endurance flight capability has become a key performance indicator. High aspect ratio UAVs have the performance advantages of long flight time and long range, but they also have problems such as large fluctuations in battery output power, narrow flight speed envelope, and difficulty in controlling altitude trajectory. Smooth speed control will greatly affect the endurance of UAVs. In existing technologies, traditional longitudinal control laws are often used for control, but traditional longitudinal control laws cannot fully meet the energy allocation and attitude control requirements of UAVs in long-endurance flight.

[0003] Furthermore, traditional longitudinal control laws mostly control air propulsion through throttle, with control surfaces only used for attitude maintenance, making it difficult to respond quickly to changes in flight status. Therefore, there is an urgent need to establish a longitudinal control law model and integrate power system control with control surface coordinated control strategies to solve the problem of poor robustness and unstable thrust performance of UAVs during flight, which makes it difficult to control flight speed and altitude trajectory, improve the control performance and safety of UAVs, enhance the endurance of UAVs, and achieve high-quality flight and control within the entire flight envelope of UAVs.

[0004] For example, a Chinese patent, publication number CN120255571A, publication date July 4, 2025, entitled "Control Method, System, and UAV for High-Precision Tracking of Landing Glide Path for Unmanned Aerial Vehicles," describes a specific technical solution: This invention relates to the field of aircraft flight control, providing a control method, system, and UAV for high-precision tracking of landing glide path for unmanned aerial vehicles (UAVs). The control method includes: S1, a control structure for determining the elevator control altitude: employing a dual-loop cascade PID control structure, with the pitch loop and altitude loop both using PID control; a hysteresis network is introduced between the pitch and altitude loops; S2, a throttle channel using a throttle-controlled airspeed control structure; S3, obtaining landing altitude and airspeed commands, and using the elevator-controlled altitude control structure and the throttle-controlled airspeed control structure to control the UAV to land along the designed glide path. The control system includes an elevator-controlled altitude control module, a throttle control module, and a landing glide path control module.

[0005] The elevator control structure of the aforementioned patent improves the accuracy of tracking the landing glide trajectory altitude of some UAVs by using a two-ring cascade. However, the aforementioned patent only uses an elevator control strategy, which has limitations in UAV control, resulting in insufficient control accuracy of the UAV. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a longitudinal trajectory control method for high aspect ratio UAVs that can coordinate elevator control channel and power channel control, thereby solving the problem of poor robustness and unstable thrust performance of UAVs during flight, which makes it difficult to control flight speed and altitude trajectory.

[0007] A longitudinal trajectory control method for a high aspect ratio unmanned aerial vehicle (UAV) includes the following specific steps: Step S1: The elevator control channel of the UAV uses a pitch angle control strategy to adjust the elevator to control the pitch angle of the UAV, thereby controlling the flight speed of the UAV. Step S2: The power channel of the UAV is controlled by adopting an energy control strategy to control the propeller speed of the UAV, thereby controlling the flight altitude of the UAV; Step S3: The UAV adopts a longitudinal control strategy to decouple the elevator control channel from the power channel, thereby completing the longitudinal coordinated control of the UAV. The longitudinal control strategy is specifically as follows: the speed command in the elevator control channel and the elevator speed command in the power channel are used as the balancing points, and the pitch angle feedforward value is obtained by using force and torque balance, which is used to adjust the pitch angle of the UAV in step S1.

[0008] Furthermore, the pitch angle control strategy in step S1 is as follows: a speed control loop is added to the outer loop of the elevator control channel to convert the speed deviation into a pitch angle command, and then the pitch angle command is fed back to the inner loop of the elevator control channel; the inner loop of the elevator control channel adopts a robust servo control strategy to control the pitch angle.

[0009] Furthermore, a speed control loop is added to the outer loop to convert the speed deviation into a pitch angle command, and then the pitch angle command is fed back to the inner loop using the following specific formula: ; In the formula, The meaning is pitch angle command; The meaning is the pitch angle feedforward value; The meaning is flight speed. The meaning is flight speed command; K The number 4 represents the gain of the speed control proportional term; K The value 5 represents the speed control integral term gain.

[0010] Furthermore, the specific formula for calculating the pitch angle using the robust servo control strategy in the inner loop is as follows: ; ; In the formula, For the damping term gain; To control the integral term gain for pitch rate; For pitch angle control term gain; The meaning is elevator command; The meaning is pitch rate; The meaning is pitch rate command; The meaning is pitch angle; The meaning is pitch angle command.

[0011] Furthermore, the energy control strategy in step S2 is as follows: using the acceleration and deceleration speed as the control variable, the altitude is tracked through the outer ring of the power channel, and the acceleration and deceleration speed is adjusted through the inner ring of the power channel.

[0012] Furthermore, the specific method for the outer ring of the power channel to perform height tracking is as follows: the error between the height command and the actual height is converted into a lift / recline speed command.

[0013] Furthermore, the specific formula for converting the error between the altitude command and the actual altitude into the elevation / climb rate command is as follows: ; In the formula, The meaning is that the gain of the proportional term is highly controlled; The meaning is altitude command; The meaning is acceleration / deceleration speed command; The meaning is height.

[0014] Furthermore, the specific method for adjusting the lifting speed of the inner ring of the power channel is as follows: the error between the lifting speed command and the actual lifting speed is converted into a propeller speed command, thereby controlling the power output of the UAV's fuel cell.

[0015] Furthermore, the specific formula for converting the error between the lift / climb command and the actual lift / climb command into the propeller speed command is as follows: ; In the formula, The meaning is the propeller speed command; The meaning is the gain of the proportional term for acceleration / deceleration control. The meaning is the integral term gain of the acceleration / deceleration speed control; The meaning is acceleration / deceleration speed command; The meaning is the speed of acceleration and deceleration.

[0016] Furthermore, using the speed command in the elevator control and the elevator speed command in the power channel as the trim points, and utilizing force and torque balance, the pitch angle feedforward value is obtained. The specific formula is as follows: ; ; In the formula, Meaning: The fundamental quantity of aircraft pitch moment. The meaning is the torque generated by the elevator. The meaning is thrust. The meaning is lift; The meaning is resistance. The meaning is the weight of the drone. g The meaning is gravitational acceleration. The meaning is the pitch angle feedforward value. The meaning is flight speed command. The meaning is altitude command.

[0017] Based on the above technical solution, the beneficial effects of this application are as follows: 1. In longitudinal coordinated control, the method of the present invention achieves decoupling of elevator channel and power channel by obtaining pitch angle feedforward value, avoids interference of propeller speed change on flight speed, makes speed and altitude control independent and precise, and ensures the overall reliability of longitudinal trajectory coordinated control.

[0018] 2. The method of the present invention employs an inner and outer loop of the elevator control channel. The inner loop enhances anti-interference capability through robust control of pitch rate, while the outer loop utilizes the speed of pitch control to achieve speed stability, ensuring sufficient stability reserves within the entire envelope, thus achieving the technical effect of effectively suppressing external disturbances.

[0019] 3. The method of the present invention directly links the power output of the fuel cell stack with the power demand during flight by using the inner and outer rings of the power channel, thereby avoiding performance degradation caused by power response lag or overload, improving the utilization efficiency of the fuel cell stack, and ensuring endurance.

[0020] 4. The method of the present invention achieves rapid suppression of high-frequency disturbances in pitch rate through the inner loop of the elevator control channel, reducing unnecessary attitude adjustments and ensuring the stability of UAV flight.

[0021] 5. In the method of the present invention, the longitudinal collaborative control compensation pre-balance torque avoids mutual interference between the power channel and the elevator control channel, reduces the continuous stress on the UAV's wings and other structures, and extends the service life of the UAV.

[0022] 6. The method of the present invention can quickly respond to the lift-down speed error through the inner ring of the power channel, which can reduce the excessive power compensation caused by power adjustment lag, protect the core components of the UAV power channel, and reduce the risk of UAV failure.

[0023] 7. In the method of the present invention, the outer ring of the power channel aims at altitude tracking, while the inner ring of the power channel precisely controls the ascent and descent speed to avoid repeated ascent or descent of the drone due to unreasonable altitude control, thereby reducing the drone's ineffective energy consumption.

[0024] 8. In the method of the present invention, compared with the power channel of traditional UAVs, the present invention adjusts the motor speed by changing the lift speed. As the largest load on the aircraft, the motor can ensure the stability of the output power by maintaining the stable operation of the propeller driven by the motor, avoiding energy waste, significantly improving energy utilization efficiency, and effectively extending the flight time of the UAV.

[0025] 9. The method of the present invention introduces pitch angle feedforward compensation values ​​obtained by using speed commands and elevator speed commands as trim points in the elevator control channel, thereby decoupling the speed control of the elevator channel from the power channel, reducing conflicts and interference between channels, and thus achieving deep collaborative optimization. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the longitudinal control scheme of the present invention; Figure 2 This is a schematic diagram of the elevator channel control structure of the present invention; Figure 3 This is the power channel control structure described in this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0028] Example 1 A longitudinal trajectory control method for a high aspect ratio unmanned aerial vehicle (UAV) includes the following specific steps: Step S1: The elevator control channel of the UAV uses a pitch angle control strategy to adjust the elevator to control the pitch angle of the UAV, thereby controlling the flight speed of the UAV. Step S2: The power channel of the UAV is controlled by adopting an energy control strategy to control the propeller speed of the UAV, thereby controlling the flight altitude of the UAV; Step S3: The UAV adopts a longitudinal control strategy to decouple the elevator control channel from the power channel, thereby completing the longitudinal coordinated control of the UAV. The longitudinal control strategy is as follows: the speed command in the elevator control channel and the elevator speed command in the power channel are used as the trim points, and the pitch angle feedforward value is obtained by using force and torque balance, which is used to adjust the pitch angle of the UAV in step S1.

[0029] Example 2 The pitch angle control strategy in step S1 is as follows: a speed control loop is added to the outer loop of the elevator control channel to convert the speed deviation into a pitch angle command, which is then fed back to the inner loop of the elevator control channel; the inner loop of the elevator control channel uses a robust servo control strategy to control the pitch angle; for example... Figure 2 As shown, the inner loop introduces a pitch rate integral term, which improves the system type and better suppresses the influence of external disturbances on the system. The proportional term in the inner loop ensures fast and accurate response to tracking control commands without overshoot. The outer loop adds a speed control loop, using the speed command and elevator command as trim points to obtain the pitch angle feedforward value. The design of this pitch angle feedforward compensation value realizes the decoupling between the elevator channel speed control and the power channel, avoiding changes in propeller speed that alter the flight speed.

[0030] The outer loop incorporates a speed control loop to convert speed deviations into pitch angle commands, which are then fed back to the inner loop using the following formula: ; In the formula, The meaning is pitch angle command; The meaning is the pitch angle feedforward value; The meaning is flight speed. The meaning is flight speed command; K The number 4 represents the gain of the speed control proportional term; K The value 5 represents the speed control integral term gain.

[0031] The specific formula for calculating the pitch angle using a robust servo control strategy in the inner loop is as follows: ; ; In the formula, For the damping term gain; To control the integral term gain for pitch rate; For pitch angle control term gain; The meaning is elevator command; The meaning is pitch rate; The meaning is pitch rate command; The meaning is pitch angle; The meaning is pitch angle command.

[0032] Example 3 The energy control strategy in step S2 is as follows: using the ascent and descent rate as the control variable, altitude tracking is performed through the outer loop of the power channel, and then the ascent and descent rate is adjusted through the inner loop of the power channel; for example... Figure 1As shown, a control architecture is proposed, in which the elevator channel controls speed and the power channel controls altitude. The speed controller, pitch controller, and pitch rate controller in the elevator channel control law are used to achieve stable speed control, ensuring sufficient stability reserves across the entire flight envelope and effectively suppressing external disturbances. Through the altitude controller and elevator speed controller, the elevator speed is selected as the control variable, taking advantage of the long-period change in altitude. The change in elevator speed adjusts the motor speed, thereby controlling the UAV's propeller speed. This mitigates the frequent power system control issues caused by real-time altitude changes, ensuring stable output power. The elevator speed command is calculated from the altitude deviation, and pitch angle feedforward compensation is obtained based on the speed command, achieving coordinated control between the two channels. This allows the UAV to perform missions in a stable and safe flight state.

[0033] The specific method for height tracking of the outer ring of the power channel is to convert the error between the height command and the actual height into a lift / recline command.

[0034] The specific formula for converting the error between the altitude command and the actual altitude into the elevation / climb rate command is as follows: ; In the formula, The meaning is that the gain of the proportional term is highly controlled; The meaning is altitude command; The meaning is acceleration / deceleration speed command; The meaning is height.

[0035] The specific method for adjusting the lift speed of the inner ring of the power channel is as follows: the error between the lift speed command and the actual lift speed is converted into a propeller speed command, which in turn controls the power output of the UAV's fuel cell.

[0036] The specific formula for converting the error between the lift command and the actual lift into the propeller speed command is as follows: ; In the formula, The meaning is the propeller speed command; The meaning is the gain of the proportional term for acceleration / deceleration control. The meaning is the integral term gain of the acceleration / deceleration speed control; The meaning is acceleration / deceleration speed command; The meaning is the speed of acceleration and deceleration.

[0037] like Figure 3As shown, based on the requirements of flight missions, in order to improve the endurance of the UAV, altitude trajectory tracking control is performed using the power channel. Since the altitude response process is slow, the propeller speed outputs thrust stably during cruise, thereby stabilizing the output power and maximizing the endurance. At the same time, when the UAV is climbing or descending and the altitude deviates significantly from the altitude command, the climb and descent speed commands are limited to ensure that the UAV maintains the same climb or descent speed, thus ensuring stable propeller speed output.

[0038] Using the speed command in the elevator control and the elevator speed command in the power channel as the trim points, and utilizing force and torque balance to obtain the pitch angle feedforward value. The specific formula is as follows: ; ; In the formula, Meaning: The fundamental quantity of aircraft pitch moment. The meaning is the torque generated by the elevator. The meaning is thrust. The meaning is lift; The meaning is resistance. The meaning is the weight of the drone. g The meaning is gravitational acceleration. The meaning is the pitch angle feedforward value. The meaning is flight speed command. The meaning is altitude command.

[0039] As shown in Table 1 below. The pitch angle feedforward value is based on... and Linear interpolation is performed, and values ​​exceeding the interpolation table boundaries are treated as boundary values. The range of these boundary values ​​is related to the performance of the UAV itself.

[0040] Table 1 Pitch Angle Feedforward Values Value

[0041] The above description is a detailed description of the preferred embodiments of this application. However, the embodiments are not intended to limit the scope of the patent application of this application. All equivalent changes or modifications made under the technical spirit of this application should fall within the patent scope covered by this application.

Claims

1. A longitudinal trajectory control method for a high aspect ratio unmanned aerial vehicle (UAV), characterized in that, The specific methods and steps include the following: Step S1: The elevator control channel of the UAV uses a pitch angle control strategy to adjust the elevator to control the pitch angle of the UAV, thereby controlling the flight speed of the UAV. Step S2: The power channel of the UAV is controlled by adopting an energy control strategy to control the propeller speed of the UAV, thereby controlling the flight altitude of the UAV; Step S3: The UAV adopts a longitudinal control strategy to decouple the elevator control channel from the power channel, thereby completing the longitudinal coordinated control of the UAV. The longitudinal control strategy is specifically as follows: the speed command in the elevator control channel and the elevator speed command in the power channel are used as the balancing points, and the pitch angle feedforward value is obtained by using force and torque balance, which is used to adjust the pitch angle of the UAV in step S1.

2. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 1, characterized in that: The pitch angle control strategy in step S1 is as follows: a speed control loop is added to the outer loop of the elevator control channel to convert the speed deviation into a pitch angle command, and then the pitch angle command is fed back to the inner loop of the elevator control channel; the inner loop of the elevator control channel adopts a robust servo control strategy to control the pitch angle.

3. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 2, characterized in that: The outer loop incorporates a speed control loop, which converts the speed deviation into a pitch angle command. The specific formula for feeding the pitch angle command back to the inner loop is as follows: ； In the formula, The meaning is pitch angle command; The meaning is the pitch angle feedforward value; The meaning is flight speed. The meaning is flight speed command; K The number 4 represents the gain of the speed control proportional term; K The value 5 represents the speed control integral term gain.

4. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 2, characterized in that: The specific formula for calculating the pitch angle using the robust servo control strategy in the inner loop is as follows: ； ； In the formula, For the damping term gain; To control the integral term gain for pitch rate; For pitch angle control term gain; The meaning is elevator command; The meaning is pitch rate; The meaning is pitch rate command; The meaning is pitch angle; The meaning is pitch angle command.

5. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 1, characterized in that: The energy control strategy in step S2 is as follows: using the acceleration and deceleration speed as the control variable, the altitude is tracked through the outer ring of the power channel, and the acceleration and deceleration speed is adjusted through the inner ring of the power channel.

6. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 5, characterized in that: The specific method for the outer ring of the power channel to perform height tracking is as follows: the error between the height command and the actual height is converted into a lift / recline speed command.

7. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 6, characterized in that: The specific formula for converting the error between the altitude command and the actual altitude into the elevation / climb rate command is as follows: ； In the formula, The meaning is that the gain of the proportional term is highly controlled; The meaning is altitude command; The meaning is acceleration / deceleration speed command; The meaning is height.

8. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 7, characterized in that: The specific method for adjusting the lift speed of the inner ring of the power channel is as follows: the error between the lift speed command and the actual lift speed is converted into a propeller speed command, thereby controlling the power output of the UAV's fuel cell.

9. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 8, characterized in that: The specific formula for converting the error between the lift command and the actual lift into the propeller speed command is as follows: ； In the formula, The meaning is the propeller speed command; The meaning is the gain of the proportional term for acceleration / deceleration control. The meaning is the integral term gain of the acceleration / deceleration speed control; The meaning is acceleration / deceleration speed command; The meaning is the rate of acceleration or deceleration.

10. The longitudinal trajectory control method for a high aspect ratio UAV according to claim 1, characterized in that: Using the speed command in the elevator control and the elevator speed command in the power channel as the trim points, and utilizing force and torque balance to obtain the pitch angle feedforward value. The specific formula is as follows: ； ； In the formula, Meaning: The fundamental quantity of aircraft pitch moment. The meaning is the torque generated by the elevator. The meaning is thrust. The meaning is lift; The meaning is resistance. The meaning is the weight of the drone. g The meaning is gravitational acceleration. The meaning is the pitch angle feedforward value. The meaning is flight speed command. The meaning is altitude command.

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