A method and system for realizing autonomous obstacle avoidance of a UAV rotorcraft

Abstract

A method and system for realizing autonomous obstacle avoidance of a rotorcraft at an unmanned airport, comprising the following steps: arranging a plurality of obstacle avoidance sensors on the unmanned aircraft to measure the distance to obstacles; setting the obstacle avoidance distance of the rotorcraft through the aircraft flight control system; calculating the expected speed of the unmanned aircraft based on the detection distance and obstacle avoidance distance of the obstacle avoidance sensor; obtaining the expected acceleration through the expected speed, and then obtaining the expected attitude inclination angle through the small disturbance assumption, and then the attitude controller realizes the control of the rotorcraft. The present invention proposes a safety strategy for 4-way obstacle avoidance, which can effectively realize the stable hovering of the unmanned aircraft after the obstacle avoidance sensor detects the obstacle in front, and avoid the unmanned aircraft from colliding with the obstacle, thereby improving the safety of the unmanned aircraft.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle applications, and in particular relates to a method and system for realizing autonomous obstacle avoidance for a rotorcraft in an unmanned aerial vehicle airport. Background Art

[0002] With the development of science and technology, rotary wing unmanned aerial vehicles have been increasingly developed. In the military field, such as battlefield situation reconnaissance, target tracking, small target strike, etc., they have a lot of applications. In the civilian field, drones are widely used in fields such as aerial photography, security, oil and gas pipeline inspection, bridge inspection, power inspection, etc. Due to the wide application of drones, there are very high requirements for the safety, reliability and stability of drones. Drones often work in harsh environments. During the flight, the drones often encounter obstacles in front of them. If they cannot avoid obstacles in time or hover in front of obstacles, the drones will crash, which seriously threatens the flight safety of drones. Summary of the invention

[0003] The object of the present invention is to provide a method and system for realizing autonomous obstacle avoidance of a UAV rotorcraft in order to solve the above-mentioned problems.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for realizing autonomous obstacle avoidance of a UAV rotorcraft at an airport, comprising the following steps:

[0006] Several obstacle avoidance sensors are installed on the drone to measure the distance to obstacles;

[0007] Setting the obstacle avoidance distance of the rotorcraft through the aircraft flight control system;

[0008] Calculate the expected speed of the drone based on the detection distance and obstacle avoidance distance of the obstacle avoidance sensor;

[0009] The expected acceleration is obtained through the expected velocity, and the expected attitude angle is obtained through the small disturbance assumption, and then the attitude controller realizes the control of the rotorcraft.

[0010] Furthermore, the obstacle avoidance sensors include obstacle avoidance sensors in four directions: front, rear, left, and right.

[0011] Furthermore, the obstacle avoidance sensor interacts with the aircraft flight control system via the CAN bus.

[0012] Furthermore, the obstacle avoidance distance is set to satisfy: the obstacle avoidance distance of the drone set by the ground station software is d, d≤max_detect_dist

[0013] Where max_detect_dist represents the maximum distance that the obstacle avoidance sensor can detect.

[0014] Furthermore, the distance to the obstacle detected by the obstacle avoidance sensor in real time is d rt , perform the following steps:

[0015] Calculate the distance d detected by the current obstacle avoidance sensor rt The difference δd between the obstacle avoidance distance d set by the ground station software; that is

[0016] δd=d rt -d Calculate the maximum expected speed of the rotorcraft through δd:

[0017] The maximum expected speed is calculated by the nonlinear error control rate.

[0018] Furthermore, the following three parameters are required to calculate the maximum expected speed:

[0019] The distance d detected by the current obstacle avoidance sensor rt The difference δd between the obstacle avoidance distance d set by the ground station software;

[0020] Proportional coefficient K p ;

[0021] Rotorcraft acceleration a, a≤a max ,a max It represents the maximum acceleration that a rotorcraft can achieve;

[0022] As shown above, the expected distance is d, v t Indicates vertical speed, current distance is d rt , the distance error is δd:

[0023] δd=d rt -d 1-1

[0024] Differential of error for:

[0025]

[0026] Define the expected speed calculation as follows:

[0027]

[0028] By being continuous and differentiable at the connection, the following equation holds:

[0029]

[0030] Furthermore, after obtaining the desired speed based on the obstacle avoidance sensor, the desired acceleration is obtained by designing the velocity loop controller, and then the desired attitude inclination angle is obtained by the small disturbance assumption:

[0031] Let the expected acceleration be a t ,v t To get the desired speed, v is the current speed, Δv is the speed error, and the speed loop control rate is obtained by using the PID controller:

[0032]

[0033] In the above formula, k pv is the proportional term coefficient, k iv is the integral term coefficient, k dv is the differential term coefficient, is the integral operator, and s is the differential operator;

[0034] In obtaining the expected acceleration a t After that, the desired attitude inclination angle can be obtained by the small disturbance assumption.

[0035] Furthermore, a system for realizing autonomous obstacle avoidance of a UAV rotorcraft at an airport includes:

[0036] A sensor module is used to set up several obstacle avoidance sensors on the drone to measure the distance to obstacles;

[0037] The obstacle avoidance distance setting module is used to set the obstacle avoidance distance of the rotorcraft through the aircraft flight control system;

[0038] The expected speed calculation module is used to calculate the expected speed of the drone based on the detection distance and obstacle avoidance distance of the obstacle avoidance sensor;

[0039] The attitude control module is used to obtain the expected acceleration through the expected speed, and then obtain the expected attitude inclination angle through the small disturbance assumption, so that the attitude controller can control the rotorcraft.

[0040] Compared with the prior art, the present invention has the following technical effects:

[0041] The present invention obtains the desired acceleration through a velocity loop controller, and then obtains the desired attitude inclination angle through a small disturbance assumption. According to the inner and outer loop control architecture adopted by the UAV, the outer loop is position\speed control, and the inner loop is attitude control, and then the attitude controller can be designed to realize the control of the rotorcraft and achieve obstacle avoidance.

[0042] The present invention proposes a safety strategy of four-way obstacle avoidance, which, combined with an obstacle avoidance algorithm, can effectively enable the obstacle avoidance sensor to achieve stable hovering of the UAV after detecting an obstacle ahead, thereby preventing the UAV from colliding with the obstacle, thereby improving the safety of the UAV. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is the expected speed nonlinear curve of the present invention;

[0044] Figure 2 This is the speed loop control structure diagram of the present invention. DETAILED DESCRIPTION

[0045] This section describes and explains the present invention and patent in detail with the accompanying drawings and detailed implementation steps. The present invention and patent include the following steps:

[0046] Layout of obstacle avoidance sensors;

[0047] Set obstacle avoidance distance;

[0048] Extreme speed is the expected speed of the drone;

[0049] Speed ​​loop control rate design.

[0050] Step 1: Obstacle Avoidance Sensor Layout

[0051] In actual use, the author deployed 4 obstacle avoidance sensors on the drone:

[0052] forward obstacle avoidance sensor;

[0053] Rear obstacle avoidance sensor;

[0054] Left obstacle avoidance sensor;

[0055] Rear obstacle avoidance sensor.

[0056] The obstacle avoidance sensor can measure the distance to the obstacle in front in real time, with a maximum detection distance of 40m, and return the distance values ​​of the three obstacles closest to the current drone. The obstacle avoidance sensor interacts with the flight control system through the CAN bus.

[0057] Step 2: Setting the flight control system obstacle avoidance distance

[0058] In order to avoid obstacles in real time, the flight control system needs to set the obstacle avoidance distance of the rotorcraft in advance, so that the rotorcraft can stop at the maximum obstacle avoidance distance set in advance even if it is flying at the maximum flight speed. Usually, the obstacle avoidance distance is set by the ground station software. Assume that the obstacle avoidance distance of the drone set by the ground station software is d. Usually the following relationship is satisfied

[0059] d≤max_detect_dist

[0060] Where max_detect_dist represents the maximum distance that the obstacle avoidance sensor can detect.

[0061] Step 3: Calculate the expected speed of the drone

[0062] Assume that the distance to the obstacle detected by the obstacle avoidance sensor in real time is d rt Then follow these steps:

[0063] ① Calculate the distance d detected by the current obstacle avoidance sensor rt The difference δd between the obstacle avoidance distance d set by the ground station software.

[0064] δd=d rt -d 1-1

[0065] ②Calculate the maximum expected speed of the rotorcraft

[0066] The maximum expected speed is calculated by the nonlinear error control rate. The following three parameters are required to calculate the maximum expected speed:

[0067] The distance d detected by the current obstacle avoidance sensor rt The difference δd between the obstacle avoidance distance d set by the ground station software;

[0068] Proportional coefficient K p ;

[0069] Rotorcraft acceleration a, a≤a max ,a max Indicates the maximum acceleration that a rotorcraft can achieve.

[0070] As shown above, the expected distance is d, v t Indicates vertical speed, current distance is d rt , the distance error is δd:

[0071] δd=d rt -d

[0072] Differential of error for:

[0073]

[0074] Define the expected speed calculation as follows:

[0075]

[0076] The curve of formula 1-5 is as follows Figure 1 As shown:

[0077] By being continuous and differentiable at the connection, the following equation holds:

[0078]

[0079] Step 4: Speed ​​loop control rate design

[0080] After obtaining the desired speed based on the obstacle avoidance sensor through step 3, the desired acceleration can be obtained by designing a speed loop controller, and then the desired attitude angle can be obtained through the small disturbance assumption. Since rotorcraft adopts an inner and outer loop control architecture, the outer loop is position\speed control, and the inner loop is attitude control, after obtaining the desired attitude angle, the attitude controller can be designed to control the rotorcraft. The control structure is as follows: Figure 2 As shown in Figure 2, this article does not describe the attitude control structure in detail. Interested readers can refer to relevant literature.

[0081] Let the expected acceleration be a t ,v t The desired speed is calculated for step 3, v is the current speed, Δv is the speed error, then the speed loop control rate can be obtained by using a traditional PID controller:

[0082]

[0083] In the above formula, k pv is the proportional term coefficient, k iv is the integral term coefficient, k dv is the differential term coefficient, is the integral operator, and s is the differential operator.

[0084] In obtaining the expected acceleration a t After that, the desired attitude inclination angle can be obtained by the small disturbance assumption.

Claims

1. A method for realizing autonomous obstacle avoidance of a rotorcraft at an unmanned airport, characterized in that: The following steps are involved: Several obstacle avoidance sensors are installed on the drone to measure the distance to obstacles; Setting the obstacle avoidance distance of the rotorcraft through the aircraft flight control system; Calculate the expected speed of the drone based on the detection distance and obstacle avoidance distance of the obstacle avoidance sensor; The desired acceleration is obtained through the desired velocity, and the desired attitude angle is obtained through the small disturbance assumption, and then the attitude controller realizes the control of the rotorcraft; Assume that the distance to the obstacle detected by the obstacle avoidance sensor in real time is d rt , perform the following steps: Calculate the distance d detected by the current obstacle avoidance sensor rt The difference δd between the obstacle avoidance distance d set by the ground station software; that is δd=d rt -d Calculate the maximum expected speed of the rotorcraft through δd: Calculate the maximum expected speed through the nonlinear error control rate; The following three parameters are required to calculate the maximum expected speed: The distance d detected by the current obstacle avoidance sensor rt The difference δd between the obstacle avoidance distance d set by the ground station software; Proportional coefficient K p ; Rotorcraft acceleration a, a≤a max ,a max It represents the maximum acceleration that a rotorcraft can achieve; As shown above, the expected distance is d, v t Indicates vertical speed, current distance is d rt , the distance error is δd: δd=d rt -d1-1 Differential of error for: Define the expected speed calculation as follows: By being continuous and differentiable at the connection, the following equation holds: After obtaining the desired speed based on the obstacle avoidance sensor, the desired acceleration is obtained by designing the speed loop controller, and then the desired attitude inclination angle is obtained through the small disturbance assumption: Let the expected acceleration be a t ,v t To get the desired speed, v is the current speed, Δv is the speed error, and the speed loop control rate is obtained by using the PID controller: In the above formula, k pv is the proportional term coefficient, k iv is the integral term coefficient, k dv is the differential term coefficient, is the integral operator, and s is the differential operator; In obtaining the expected acceleration a t After that, the desired attitude inclination angle can be obtained by the small disturbance assumption.

2. The method for realizing autonomous obstacle avoidance of a UAV rotorcraft at an unmanned airport according to claim 1, characterized in that: The obstacle avoidance sensors include obstacle avoidance sensors in four directions: front, rear, left and right.

3. The method for realizing autonomous obstacle avoidance of a UAV rotorcraft at an unmanned airfield according to claim 1, characterized in that: The obstacle avoidance sensor interacts with the aircraft flight control system via the CAN bus.

4. The method for realizing autonomous obstacle avoidance of a UAV rotorcraft at an unmanned airfield according to claim 1, characterized in that: Setting the obstacle avoidance distance satisfies: The obstacle avoidance distance of the drone set by the ground station software is d, d≤max_detect_dist; Where max_detect_dist represents the maximum distance that the obstacle avoidance sensor can detect.

5. A system for realizing autonomous obstacle avoidance of a rotorcraft at an unmanned airport, characterized in that: include: A sensor module is used to set up several obstacle avoidance sensors on the drone to measure the distance to obstacles; The obstacle avoidance distance setting module is used to set the obstacle avoidance distance of the rotorcraft through the aircraft flight control system; The expected speed calculation module is used to calculate the expected speed of the drone based on the detection distance and obstacle avoidance distance of the obstacle avoidance sensor; The attitude control module is used to obtain the expected acceleration through the expected speed, and then obtain the expected attitude angle through the small disturbance assumption, so that the attitude controller can control the rotorcraft; Assume that the distance to the obstacle detected by the obstacle avoidance sensor in real time is d rt , perform the following steps: Calculate the distance d detected by the current obstacle avoidance sensor rt The difference δd between the obstacle avoidance distance d set by the ground station software; that is δd=d rt -d Calculate the maximum expected speed of the rotorcraft through δd: Calculate the maximum expected speed through the nonlinear error control rate; The following three parameters are required to calculate the maximum expected speed: The distance d detected by the current obstacle avoidance sensor rt The difference δd between the obstacle avoidance distance d set by the ground station software; Proportional coefficient K p ; Rotorcraft acceleration a, a≤a max ,a max It represents the maximum acceleration that a rotorcraft can achieve; As shown above, the expected distance is d, v t Indicates vertical speed, current distance is d rt , the distance error is δd: δd=d rt -d 1-1 Differential of error for: Define the expected speed calculation as follows: By being continuous and differentiable at the connection, the following equation holds: After obtaining the desired speed based on the obstacle avoidance sensor, the desired acceleration is obtained by designing the speed loop controller, and then the desired attitude inclination angle is obtained through the small disturbance assumption: Let the expected acceleration be a t ,v t To get the desired speed, v is the current speed, Δv is the speed error, and the speed loop control rate is obtained by using the PID controller: In the above formula, k pv is the proportional term coefficient, k iv is the integral term coefficient, k dv is the differential term coefficient, is the integral operator, and s is the differential operator; In obtaining the expected acceleration a t After that, the desired attitude inclination angle can be obtained by the small disturbance assumption.

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