CN106873606B - A Fast Altitude Command Tracking Method Based on Nonlinear Hysteresis - Google Patents

Abstract

The invention belongs to the height control technology of an unmanned aerial vehicle, and in particular relates to a fast height command tracking method based on a nonlinear hysteresis loop. The invention includes a fast height command tracking method based on nonlinear hysteresis. The present invention calculates the height control command by integrating the information such as the flight height and flight state of the current UAV, and the height command received by the UAV, and through the non-linear hysteresis-based height mode switching logic and command resolution, and the control The flying height of the UAV is quickly tracked to the target height, so that the UAV has the ability to respond to height commands and quickly track to the command height in real time under different flight states.

Description

A Fast Altitude Command Tracking Method Based on Nonlinear Hysteresis

technical field

The invention belongs to the height control technology of an unmanned aerial vehicle, and in particular relates to a fast height command tracking method based on a nonlinear hysteresis loop and its realization.

Background technique

The working mode of the UAV at high altitude is height control, that is, tracking the height command. When the current flying height of the UAV is far from the height command, it takes a long time for the UAV to track the height command in the height control mode. . Generally, the height control of UAVs has a lifting speed capability of 6m/s. When the height difference is 60m, it takes 10s to adjust. The adjustment ability in the direction of lifting speed is greater than or equal to 15m/s, and the height difference of 60m only takes 4s. However, the UAV can only fly at a fixed altitude by means of altitude control, so when the current flying altitude of the UAV is close to the altitude command, it needs to switch to the altitude control mode to fine-tune the altitude command.

Contents of the invention

The invention proposes a fast height command tracking method based on a nonlinear hysteresis loop and a software implementation flow of the method. By switching the control mode of the UAV under different height differences, the technical problem of the UAV's rapid response to the height command is solved.

The present invention provides a fast height command tracking method based on nonlinear hysteresis, and the specific steps are as follows:

Step 1: The altitude command tracking module receives the altitude measurement value, the altitude command, and the flight status information; the flight status information includes: level flight, descent, and climb;

Step 2: Altitude command tracking initialization, judging whether it is the first shot to enter the height control mode, if it is the first shot, perform height command tracking initialization; if not, execute the height control mode switching logic, and generate the control mode word;

Step 3: Execute the corresponding height command calculation according to the control mode word;

Step 4: Output the altitude command to the elevator.

The specific steps of altitude command tracking initialization described in step 2 above are as follows:

A: Calculate the height difference DH of the first shot, DH refers to the difference between the height command and the actual height;

B: If the altitude difference DH of the first beat is greater than DH0, then set the altitude control modal word to pitch angle gauge speed control; otherwise, execute the third step. DH0 represents the absolute value of the maximum height difference;

C: If the height difference DH of the first beat is less than -DH0, then set the height control modal word as pitch angle gauge speed control; otherwise, execute D;

D: If the height difference DH of the first beat is greater than -DH0, then set the height control modal word as height control.

The height control mode switching logic described in step 2, the specific steps are as follows:

A: Calculate the height difference DH of four consecutive beats;

B: If the altitude difference DH is less than -DH0m for 4 consecutive beats, then schedule the pitch angle gauge speed control;

C: If the altitude difference DH is greater than DH0m for 4 consecutive beats, then schedule the pitch angle gauge speed control;

D: If the altitude difference DH is greater than -DH0m and less than -DH1m for 4 consecutive beats, it needs to be handled separately according to the flight status of the drone at this time: if the flight status of the drone is level flight at this time, then schedule height control; otherwise , to schedule the pitch angle gauge speed control. The DH1 represents the minimum absolute value of height difference, DH1<DH0;

E: If the altitude difference DH is greater than –DH1m and less than DH1m for 4 consecutive beats, dispatch altitude control;

F: If the altitude difference DH is greater than DH1m and less than DH0m for 4 consecutive shots, it needs to be handled separately according to the flight status of the drone at this time: if the flight status of the drone is level flight at this time, then schedule height control; otherwise, schedule Pitch angle gauge speed control.

Beneficial effects: the present invention automatically calculates the height control command of the drone by integrating information such as the current flying height and flight state of the drone, and the height command sent to the drone, and controls the drone to automatically and quickly track to the target height. When the height difference is large, the invention can control the UAV to quickly reach the target height; when the height difference is small, the height control command can be fine-tuned to control the UAV to fly at a fixed height. It has important engineering application value.

Description of drawings

Figure 1---Interface diagram of altitude command fast tracking module.

Figure 2 --- The flow chart of fast altitude command tracking based on nonlinear hysteresis.

Figure 3 --- Altitude command tracking initialization flow chart.

Figure 4 --- Altitude control mode switching logic flow chart.

Detailed ways

The method of fast altitude command tracking based on nonlinear hysteresis, the specific implementation steps are as follows:

(1) As shown in Figure 2, realize the total scheduling function based on the fast height command tracking of nonlinear hysteresis;

(2) Realize the interface function for obtaining the flying height and altitude command of the drone;

(3) As shown in Figure 3, realize the execution function of height instruction tracking initialization;

(4) As shown in Figure 4, realize the executive function of height control mode switching logic;

(5) Realize the height command calculation function.

Taking the input flight state and the altitude difference of four consecutive shots as an example, the specific implementation steps of this method will be described in detail in conjunction with Figure 2:

Assumptions:

(1) The execution cycle is 20ms;

(2) DH0=50m; DH1=25m.

The implementation steps are:

(1) Periodically dispatch the altitude command tracking program;

(2) If the height difference DH of the first beat is greater than DH0 or less than -DH0, then set the height control mode word as the pitch angle table speed control mode, and set it as the height control mode in other cases. This step is performed only once;

(3) Execute the height control mode switching logic, the height control mode word result of this step output is listed as shown in table 1;

(4) According to the altitude control modal word obtained in step (3), execute the corresponding altitude command calculation.

Table 1

Claims (2)

1. A fast height command tracking method based on nonlinear hysteresis, characterized in that, the concrete steps are as follows: Step 1: The altitude command tracking module receives the altitude measurement value, the altitude command, and the flight status information; the flight status information includes: level flight, descent, and climb; Step 2: Altitude command tracking initialization, judge whether it is the first shot to enter the altitude control mode, if it is the first shot, perform height command tracking initialization; if not, execute the altitude control mode switching logic, including: A: Calculate the height difference DH of four consecutive beats; B: If the altitude difference DH is less than -DH0 for 4 consecutive beats, then schedule the pitch angle gauge speed control; C: If the altitude difference DH is greater than DH0 for 4 consecutive beats, then schedule the pitch angle gauge speed control; D: If the height difference DH is greater than -DH0 and less than -DH1 for 4 consecutive beats, it needs to be handled separately according to the flight status of the drone at this time: if the flight status of the drone is level flight at this time, then schedule height control; otherwise , scheduling pitch angle gauge speed control, the DH1 represents the absolute value of the minimum altitude difference, DH1<DH0; E: If the altitude difference DH is greater than –DH1 and less than DH1 for 4 consecutive beats, dispatch altitude control; F: If the altitude difference DH is greater than DH1 and less than DH0 for 4 consecutive beats, it needs to be handled separately according to the flight status of the drone at this time: if the flight status of the drone is level flight at this time, then schedule height control; otherwise, schedule Pitch angle gauge speed control; Generate control modal words; Step 3: Execute the corresponding height command calculation according to the control mode word; Step 4: Output the altitude command to the elevator. 2. a kind of fast height command tracking method based on nonlinear hysteresis according to claim 1, is characterized in that, the height command tracking initialization concrete steps described in step 2 are as follows: A: Calculate the height difference DH of the first shot, DH refers to the difference between the height command and the actual height; B: If the height difference DH of the first beat is greater than DH0, then set the height control modal word as pitch angle gauge speed control; otherwise, execute C; DH0 represents the absolute value of the maximum height difference; C: If the height difference DH of the first beat is less than -DH0, then set the height control modal word as pitch angle gauge speed control; otherwise, execute D; D: If the height difference DH of the first beat is greater than -DH0, then set the height control modal word as height control.