A rotor collision early warning and automatic stop method, system, product and medium

Abstract

A rotor collision early warning and automatic stop method, system, product and medium, relating to general control or regulation system field, the method comprises: based on the motor parameter mutation characteristics and the obstacle approach tendency determines the touch area and the touch time, realizes the collision risk early prediction. The spatial distribution of the touch area is used to calculate the escape energy, and after the optimal escape direction is obtained, the main rotor in the touch area is stopped in time, and the rotating speed of other rotors is adjusted for compensation control. The implementation of the method can improve the flight stability of the multi-rotor unmanned aerial vehicle in high-speed flight or sudden situation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of general control or regulation systems, in particular to a rotor collision early warning and automatic stop method, system, product and medium. BACKGROUND

[0002] With the rapid development of unmanned aerial vehicle technology, its application scenarios are increasingly rich, especially in urban building-intensive areas, complex mountainous terrain areas and other environments, the operation tasks are increasing. When performing tasks in these complex environments, the unmanned aerial vehicle needs to frequently operate close-range flight, which puts higher requirements on the safety of the unmanned aerial vehicle.

[0003] The current unmanned aerial vehicle collision protection scheme usually adopts a combination of obstacle detection and flight path planning. This scheme obtains obstacle information by installing a distance sensor on the unmanned aerial vehicle, detects the flight state in combination with an inertial measurement unit, and adjusts the flight path to achieve obstacle avoidance when an obstacle is detected. At the same time, when a collision occurs, emergency braking is achieved by cutting off the power supply of the motor.

[0004] However, in high-speed flight or sudden situations, due to the large inertia of the unmanned aerial vehicle, it is difficult to stop the rotor rotation in time by relying only on cutting off the power supply of the motor. At this time, the continuous rotation of the rotor will exacerbate the damage caused by the collision, and the unmanned aerial vehicle is easy to lose control after the collision, causing secondary collision. SUMMARY

[0005] The present application provides a rotor collision early warning and automatic stop method, system, product and medium, which is used to improve the flight stability of a multi-rotor unmanned aerial vehicle in high-speed flight or sudden situations.

[0006] In a first aspect, the application provides a rotor collision early warning and automatic stop method applied to a rotor collision early warning and automatic stop system. The method comprises: obtaining flight state parameters and environment perception data of a target unmanned aerial vehicle, wherein the flight state parameters comprise rotor motor speed, attitude angle and kinetic energy parameters, and the environment perception data comprises target obstacle distance; identifying motor parameter mutation characteristics according to the change trend of the flight state parameters, judging obstacle approaching trend based on the environment perception data, determining a collision area and a collision time based on the motor parameter mutation characteristics and the obstacle approaching trend, wherein the motor parameter mutation characteristics represent the initial state of the collision, and the collision area represents the spatial range of the collision; analyzing the initial stress state of the collision based on the mutation characteristics, calculating the escape energy according to the spatial distribution of the collision area and the kinetic energy parameters, determining the motion range by using the attitude angle, and generating an optimal escape direction in the motion range based on the stress state, wherein the optimal escape direction is the path direction with the minimum energy loss; stopping the main rotor in the collision area, calculating the target speed of the second rotor and the third group of rotors according to the optimal escape direction and the collision time, and controlling the second rotor and the third group of rotors according to the target speed, wherein the main rotor is the rotor that collides, the second rotor is the opposite rotor with an included angle of one hundred and eighty degrees with the main rotor, and the third group of rotors are the other rotors except the main rotor and the second rotor.

[0007] In the above embodiment, the collision risk is predicted in advance by determining the collision area and the collision time based on the motor parameter mutation characteristics and the obstacle approaching trend. After calculating the optimal escape direction by using the spatial distribution of the collision area, the main rotor in the collision area is stopped in time, and the speed of the other rotors is adjusted for compensation control. Thus, in high-speed flight or sudden situations, not only the rotation of the rotor can be stopped in time to reduce the collision damage, but also the stability of the aircraft can be maintained through the cooperative control of the other rotors, effectively preventing the occurrence of secondary collision.

[0008] In combination with some embodiments of the first aspect, in some embodiments, the steps of identifying the motor parameter mutation characteristics according to the change trend of the flight state parameters, judging the obstacle approaching trend based on the environment perception data, and determining the collision area and the collision time based on the motor parameter mutation characteristics and the obstacle approaching trend specifically comprise: obtaining the rotor motor speed change rate and the attitude angle change rate in a preset time window, calculating the speed mutation amplitude based on the rotor motor speed change rate, and calculating the attitude mutation amplitude based on the attitude angle change rate; judging the type of the motor parameter mutation characteristics according to the speed mutation amplitude and the attitude mutation amplitude; obtaining the change rate of the target obstacle distance, and determining the obstacle approaching trend when the change rate of the target obstacle distance is greater than a preset threshold; determining the spatial boundary of the collision area according to the type of the motor parameter mutation characteristics, and calculating the collision time based on the change speed of the obstacle approaching trend and the current time.

[0009] In the above embodiment, the motor speed and attitude angle change rate in the preset time window are acquired, the mutation amplitude is calculated, and the collision feature type is judged. The approaching trend is judged in combination with the obstacle distance change rate, and the specific touch area and touch time are determined based on the spatio-temporal correlation of the collision feature type and the approaching trend. A complete analysis link from parameter monitoring to collision prediction is formed, the accuracy and reliability of the collision warning are improved, and accurate spatio-temporal reference is provided for subsequent protection measures.

[0010] In combination with some embodiments of the first aspect, in some embodiments, the collision initial force state is analyzed based on the mutation feature, the escape energy is calculated according to the spatial distribution of the touch area and the kinetic energy parameter, the motion range is determined based on the attitude angle, and the steps of generating the optimal escape direction in the motion range based on the force state specifically include: determining the collision force direction according to the type of the motor parameter mutation feature, calculating the moment component generated by the collision based on the collision force direction and the attitude angle, and obtaining the collision initial force state by substituting the moment component and the kinetic energy parameter into a preset force model; calculating the collision volume based on the spatial boundary of the touch area, calculating the energy loss in the collision process according to the collision volume and the kinetic energy parameter, and determining the remaining kinetic energy as the escape energy; calculating the three-dimensional space range in which the unmanned aerial vehicle can move according to the attitude angle, and generating the optimal escape direction in the three-dimensional space range based on the collision initial force state by using an energy optimization algorithm.

[0011] In the above embodiment, the force direction is determined according to the collision feature type, the moment component is calculated and substituted into the force model to obtain the initial force state. The collision volume and energy loss are calculated based on the touch area, the escape energy is determined, and the escape direction is generated in the movable space range by using the energy optimization algorithm. A complete mechanical-energy analysis model of the collision process is established, the optimal escape path is automatically planned, and the energy efficiency of the risk avoidance process is ensured.

[0012] In combination with some embodiments of the first aspect, in some embodiments, the steps of stopping the main rotor in the touch area, calculating the target rotating speed of the second rotor and the third group of rotors according to the optimal escape direction and the touch time, and controlling the second rotor and the third group of rotors according to the target rotating speed specifically include: detecting whether the main rotor is located in the touch area, and stopping the main rotor when it is detected that the main rotor is located in the touch area; generating an expected acceleration according to the optimal escape direction, establishing a dynamic equation set based on the expected acceleration and the touch time, and solving the dynamic equation set to obtain the target rotating speed of the second rotor and the third group of rotors; and respectively controlling the rotating speed of the second rotor and the third group of rotors according to the target rotating speed to match the actual rotating speed of the second rotor and the third group of rotors with the target rotating speed.

[0013] In the above embodiment, the position of the main rotor is detected in real time and the stall control is performed, and the expected acceleration is generated according to the optimal escape direction, and a set of dynamic equations is established to solve the target rotating speed of the other rotors. A closed-loop control is adopted to ensure that the rotating speed of each rotor matches the target value, forming a complete execution link from the stall instruction to the compensation control, realizing the accurate adjustment of the rotating speed of the rotors, and ensuring the flight stability of the unmanned aerial vehicle in the emergency state.

[0014] In combination with some embodiments of the first aspect, in some embodiments, after the steps of stopping the main rotor in the touch area, calculating the target rotating speed of the second rotor and the third group of rotors according to the optimal escape direction and the touch time, and controlling the second rotor and the third group of rotors according to the target rotating speed, the method further comprises: obtaining a feature type of the motor parameter mutation feature, and retrieving a corresponding emergency control strategy from a preset escape mode library according to the feature type, the emergency control strategy comprising a stall time sequence of the main rotor and a rotating speed adjustment sequence of the second rotor and the third group of rotors; setting a control priority based on the emergency control strategy, so that the execution priority of the emergency control strategy is higher than that of the real-time control instruction based on the optimal escape direction; calculating the deviation of the preset rotating speed in the emergency control strategy according to the real-time feedback values of the rotating speed of the rotors and the attitude angle, and compensating and adjusting the rotating speed of the second rotor and the third group of rotors based on the deviation; when the execution of the emergency control strategy is completed, judging whether the restart condition of the main rotor is met based on the flight state parameters, and adjusting the rotating speed of the main rotor to the designated working rotating speed according to a preset rotating speed-time curve when the restart condition is met.

[0015] In the above embodiment, the preset emergency control strategy is called based on the collision feature type, and the stall time sequence and the rotating speed adjustment sequence are executed after the control priority is set. The compensation adjustment is performed according to the real-time feedback, and the rotating speed of the main rotor is restored according to the preset curve after the emergency control is completed. A complete emergency disposal and recovery mechanism is established, the systematicness and controllability of the collision disposal are improved, and the smooth transition of the unmanned aerial vehicle from the emergency state to the normal working state is ensured.

[0016] In combination with some embodiments of the first aspect, in some embodiments, after the steps of stopping the main rotor in the touch area, calculating the target rotating speed of the second rotor and the third group of rotors according to the optimal escape direction and the touch time, and controlling the second rotor and the third group of rotors according to the target rotating speed, the method further comprises: obtaining the moment of inertia parameter of the main rotor and the current motor torque value, calculating the minimum braking distance of the main rotor according to the moment of inertia parameter and the current motor torque value; demarcating a collision safety buffer zone based on the minimum braking distance, and taking the boundary position of the collision safety buffer zone as a warning threshold for triggering the stall of the main rotor; when the target obstacle distance is less than the warning threshold, the rotating speed of the main rotor is reduced to a preset safe rotating speed in advance.

[0017] In the above embodiments, the minimum braking distance is calculated according to the moment of inertia of the main rotor and the motor torque, and the boundary position is set as the warning threshold after the safety buffer zone is delimited. The main rotor speed is reduced in advance when the obstacle distance is less than the threshold, a warning mechanism based on the dynamic characteristics is constructed, the collision risk is prevented in advance, and the impact damage caused by the sudden collision to the unmanned aerial vehicle is reduced.

[0018] In combination with some embodiments of the first aspect, in some embodiments, after the main rotor in the touch area is stopped, and the steps of calculating the target rotating speed of the second rotor and the third group of rotors according to the optimal escape direction and the touch moment and controlling the second rotor and the third group of rotors according to the target rotating speed, the method further comprises: obtaining the current spatial orientation of the main rotor, and dividing the main rotor into an obstacle-facing end and a far-obstacle end; controlling the twist angle of the rotors in the obstacle-facing end to increase by a first preset angle, and controlling the twist angle of the rotors in the far-obstacle end to decrease by a second preset angle; calculating the deflection force generated by the main rotor according to the change of the twist angle, and using the deflection force to make the main rotor generate a preset deflection speed around the rotor shaft; detecting the difference between the actual deflection speed of the main rotor and the preset deflection speed, and adjusting the twist angle change rate of the obstacle-facing end and the far-obstacle end when the difference is greater than a preset threshold; recalculating the force distribution of the main rotor according to the twist angle change rate, converting the force distribution into a compensation rotating speed of the second rotor and the third group of rotors, and adjusting the target rotating speed of the second rotor and the third group of rotors through the compensation rotating speed.

[0019] In the above embodiments, the main rotor is divided into an obstacle-facing end and a far-obstacle end, the twist angles of the two ends are adjusted differently, the deflection force is generated to make the main rotor deflect around the shaft, the deflection speed is detected in real time, and the twist angle change rate is dynamically adjusted, and the force distribution is converted into a compensation rotating speed of other rotors. A cooperative control mechanism of active obstacle avoidance and attitude compensation is established, which reduces the collision probability of the main rotor and the obstacle, and ensures the motion stability of the aircraft during obstacle avoidance.

[0020] In the second aspect, the embodiments of the present application provide a rotor collision warning and automatic stopping system, which comprises one or more processors and a memory; the memory is coupled with the one or more processors, the memory is used to store computer program code, the computer program code comprises computer instructions, and the one or more processors invoke the computer instructions to make the rotor collision warning and automatic stopping system execute the method described in the first aspect and any possible implementation manner of the first aspect.

[0021] In the third aspect, the embodiments of the present application provide a computer program product comprising instructions, which, when the above computer program product runs on the rotor collision warning and automatic stopping system, makes the above rotor collision warning and automatic stopping system execute the method described in the first aspect and any possible implementation manner of the first aspect.

[0022] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium, including instructions, when the instructions run on the rotor collision early warning and automatic stop system, causing the rotor collision early warning and automatic stop system to perform the method described in the first aspect and any possible implementation manner of the first aspect.

[0023] It can be understood that the rotor collision early warning and automatic stop system provided by the second aspect, the computer program product provided by the third aspect, and the computer storage medium provided by the fourth aspect are all used to execute the method provided by the embodiments of the present application. Therefore, the beneficial effects that can be achieved are referred to the beneficial effects in the corresponding method, which will not be described here.

[0024] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0025] 1. The present application determines the touch area and touch time based on the parameter mutation characteristics of the motor and the approach trend of the obstacle, realizes the early prediction of the collision risk. After calculating the escape energy using the spatial distribution of the touch area and obtaining the optimal escape direction, the main rotor in the touch area is stopped in time, and the rotation speed of other rotors is adjusted for compensation control. Thus, in high-speed flight or sudden situations, not only can the rotors be stopped in time to reduce collision damage, but also the stability of the aircraft can be maintained through the cooperative control of other rotors, effectively preventing the occurrence of secondary collisions.

[0026] 2. The present application obtains the motor speed and attitude angle change rate within a preset time window, calculates the mutation amplitude to determine the collision feature type. The approach trend is determined by combining the obstacle distance change rate, and the specific touch area and touch time are determined based on the spatio-temporal correlation of the collision feature type and the approach trend. A complete analysis link from parameter monitoring to collision prediction is formed, improving the accuracy and reliability of collision warning and providing accurate spatio-temporal reference for subsequent protection measures.

[0027] 3. The present application determines the force direction according to the collision feature type, calculates the moment component, and then substitutes it into the force model to obtain the initial force state. The collision volume and energy loss are calculated based on the touch area, the escape energy is determined, and the energy optimal algorithm is used to generate the escape direction within the movable space range. A complete mechanical-energy analysis model of the collision process is established, the optimal escape path is automatically planned, and the energy efficiency of the risk avoidance process is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flowchart of the rotor collision early warning and automatic stop method in the embodiments of the present application;

[0029] Figure 2is another flowchart of the rotor collision warning and automatic stop method in the embodiments of the present application;

[0030] Figure 3 is a schematic diagram of an entity device structure of the rotor collision warning and automatic stop system in the embodiments of the present application. DETAILED DESCRIPTION

[0031] The terms used in the following embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "and / or" as used herein refer to any or all possible combinations of one or more of the associated listed items.

[0032] Hereinafter, the terms "first" and "second" are only used for the purpose of description, and cannot be understood as implying or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features, and in the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0033] To facilitate understanding, the application scenarios of the embodiments of the present application are introduced as follows.

[0034] In a city with dense buildings, a multi-rotor unmanned aerial vehicle is performing a building outer wall detection task. Due to the narrow spacing between buildings, the unmanned aerial vehicle needs to frequently fly and turn in close proximity between buildings. During the execution of the task, the unmanned aerial vehicle may encounter sudden airflow disturbance or unexpected obstacles, resulting in collision between the rotor and the building. Since the unmanned aerial vehicle has a large kinetic energy and inertia in high-speed flight state, even if the collision danger is detected and the motor power is cut off, the rotor will continue to rotate at high speed for a period of time. The continuously rotating rotor not only aggravates the damage caused by the collision, but also may cause the unmanned aerial vehicle to lose control and cause secondary collision. Therefore, a method is needed that can quickly identify the collision characteristics when the collision occurs and realize intelligent stop of the rotor, so as to reduce the loss caused by the collision and maintain the controllability of the unmanned aerial vehicle.

[0035] Current UAV collision protection systems usually use distance sensors to detect obstacles and combine with inertial measurement units to monitor flight status. When the distance of the detected obstacle is less than a safety threshold, the system will try to adjust the flight path to avoid obstacles. If a collision occurs, the system will directly cut off the power supply of all motors to achieve emergency braking. For example, in a building detection task, the UAV encounters sudden crosswind and deviates from the planned trajectory. Although the distance sensor detects that the distance to the building is too close and triggers emergency braking, due to the inertia of the rotor, the rotor continues to rotate at high speed for nearly 2 seconds after the power supply is cut off. During this period, the rotor continues to collide with the building and causes serious damage, and the UAV loses the ability to control the attitude and falls. This simple power-off method cannot effectively deal with high-speed collision situations and cannot maintain the controllability of the UAV.

[0036] The UAV collision warning system using the present application can monitor flight status parameters such as rotor motor speed and attitude angle in real time. When a collision occurs, the system can quickly identify the sudden change characteristics of the motor parameters and determine the specific touch area and time in combination with environmental perception data. For example, in the same building detection scenario, when a certain rotor collides with the building, the system immediately analyzes the initial force state and energy distribution of the collision. Then the system only stops the main rotor that collides, and according to the optimal escape direction calculated, accurately adjusts the speed of the other rotors to maintain flight control. By separating the colliding rotor from the building and using other rotors to generate a compensating torque, the UAV can maintain basic attitude stability and move away from the obstacle according to the optimal path. The UAV remains controllable throughout the process, effectively avoiding secondary collisions caused by complete loss of control. This intelligent stopping method based on collision feature recognition not only reduces the damage caused by collisions, but also provides the UAV with the ability to escape after a collision.

[0037] For ease of understanding, the method provided by the present embodiment will be described in the flow below in combination with the above scenario. Please refer to Figure 1 , which is a flowchart of the rotor collision warning and automatic stopping method in the embodiment of the present application.

[0038] S101, obtain the flight status parameters and environmental perception data of the target UAV, the flight status parameters including rotor motor speed, attitude angle and kinetic energy parameters, and the environmental perception data including target obstacle distance.

[0039] The target unmanned aerial vehicle represents a multi-rotor aircraft performing a flight task. The flight state parameter refers to a set of physical quantities describing the motion state of the unmanned aerial vehicle. The rotor motor speed represents the real-time rotating speed of each rotor motor, with units of revolutions per minute. The attitude angle refers to the Euler angle of the unmanned aerial vehicle relative to the earth coordinate system, including the roll angle, pitch angle and yaw angle. The kinetic energy parameter represents the motion energy characteristics of the unmanned aerial vehicle, including linear velocity, angular velocity and mass distribution. The environmental perception data refers to the surrounding environment information obtained through sensors. The target obstacle distance represents the shortest distance from the unmanned aerial vehicle to the obstacle, with units of meters.

[0040] This step is continuously performed during the execution of the flight task by the unmanned aerial vehicle. When the unmanned aerial vehicle is in a flight state, it is necessary to collect and update the flight state and environmental information in real time to provide a data basis for subsequent collision warning. Specifically, the real-time rotating speed data of each rotor is collected through the motor encoder, the attitude angle information of the aircraft is obtained through the inertial measurement unit, the kinetic energy parameter is calculated according to the mass distribution and motion state, and the distance to the surrounding obstacles is measured using laser ranging or ultrasonic sensors. After all data are filtered, they are uniformly stored in the data buffer area of the flight controller for subsequent steps.

[0041] In some embodiments, the acquisition of flight state parameters and environmental perception data can be achieved in various ways: alternatively, data can be collected through a distributed sensing network: sensor nodes are installed at key positions of the unmanned aerial vehicle, including optical flow sensors at the ends of the arms, inertial sensors at the center of the fuselage, Hall speed sensors at the rotor hubs, etc. Each node transmits data to the central processor through the CAN bus to achieve synchronous acquisition of multi-source data; alternatively, data can be collected through an integrated sensing unit: a multifunctional sensor module integrating an accelerometer, a gyroscope, a barometer, an ultrasonic ranging function, etc. is installed at the center of the fuselage to uniformly complete the collection of various types of data, and the data is transmitted directly to the flight control through the SPI interface. It can be understood that other data acquisition methods can also be used to acquire flight state parameters and environmental perception data, which are not limited here.

[0042] S102, a motor parameter mutation feature is identified according to the change trend of the flight state parameter, an obstacle approaching trend is judged based on the environmental perception data, and a touch area and a touch time are determined based on the motor parameter mutation feature and the obstacle approaching trend, the motor parameter mutation feature representing the initial state of the collision, and the touch area representing the spatial range of the collision.

[0043] Wherein, the motor parameter mutation feature represents the data feature of abnormal change of motor operation parameter. The obstacle approaching trend refers to the change law of distance between the target obstacle and the unmanned aerial vehicle. The touch area represents the spatial range in which collision may occur, defined by the spherical center coordinates and radius. The touch time refers to the time point at which collision is expected to occur. The collision initial state represents the kinematic characteristics at the moment of collision occurrence. The spatial range refers to the three-dimensional space area affected by the collision.

[0044] This step is executed after obtaining the flight state parameters and environmental perception data. By analyzing the time series characteristics of these data, potential collision risks are identified and the specific location and time of collision are predicted. Specifically, first, trend analysis is performed on the flight state parameters, focusing on the mutation of parameters such as motor speed, current, and temperature. At the same time, the rate of change of obstacle distance is calculated to determine whether there is a trend of rapid approach. When both motor parameter mutation and obstacle distance decrease are detected, the region range and time point of possible collision are determined according to the spatio-temporal correlation of the two.

[0045] In some embodiments, collision prediction can be achieved in various ways: optionally, a data-driven method is used: a time series model of motor parameters and obstacle distance is established, the rate of change of parameters is calculated using a sliding time window, mutation features are determined by setting threshold values, target tracking algorithms are used to predict obstacle motion trajectories, and finally collision warning results are output; optionally, a model-driven method is used: based on the dynamics model of the unmanned aerial vehicle and the environmental map, a collision risk assessment function is constructed, the collision probability distribution under the current state is calculated in real time, the touch area is determined by setting a probability threshold, and the touch time is calculated using kinematic equations. It can be understood that other methods can also be used to realize collision feature recognition and prediction, which are not limited here.

[0046] In some embodiments, this step specifically includes:

[0047] The rate of change of rotor motor speed and the rate of change of attitude angle within a preset time window are obtained, the rotor motor speed mutation amplitude is calculated based on the rate of change of rotor motor speed, and the attitude mutation amplitude is calculated based on the rate of change of attitude angle.

[0048] In this step, wherein, the preset time window represents a fixed time range for data analysis, usually 100-200 ms. The rate of change of rotor motor speed refers to the change amount of motor speed per unit time, with units of rpm / s. The rate of change of attitude angle represents the change amount of aircraft attitude angle per unit time, with units of degrees / s. The rotor motor speed mutation amplitude refers to the amplitude value of the rate of change of rotor motor speed exceeding the normal range. The attitude mutation amplitude represents the amplitude value of the rate of change of attitude angle exceeding the normal range.

[0049] This step is periodically executed during the continuous operation of the system to monitor abnormal changes in the motion state of the UAV. In the process of normal flight, the change characteristics of the state parameters need to be calculated and updated in real time to provide basic data for collision warning. Specifically, the motor speed and attitude angle data are sampled every 10 ms, and the change rates of these parameters are calculated within a 200 ms time window. By comparing with historical data, it is determined whether the parameter change has a mutation feature. The rotation speed mutation amplitude is calculated by the ratio of the current change rate to the average normal change rate, and the attitude mutation amplitude is calculated in a similar way.

[0050] According to the rotation speed mutation amplitude and the attitude mutation amplitude, the type of motor parameter mutation feature is determined.

[0051] In this step, the type of motor parameter mutation feature includes three basic types: rotation speed drop type, rotation speed fluctuation type and rotation speed block type. Type judgment is based on the joint analysis results of rotation speed and attitude parameters.

[0052] This step is executed immediately after the mutation amplitude is obtained, to determine the specific mode of collision. Different types of collisions will produce different parameter change characteristics, and the collision type needs to be accurately identified to take corresponding disposal measures. Specifically, when the rotation speed mutation amplitude is greater than 200% and the attitude mutation amplitude is less than 50%, it is determined as rotation speed drop type; when the rotation speed mutation amplitude and the attitude mutation amplitude are both greater than 100%, it is determined as rotation speed fluctuation type; when the rotation speed mutation amplitude is less than 50% but the duration exceeds 300 ms, it is determined as rotation speed block type.

[0053] The change rate of the distance of the target obstacle is obtained, and when the change rate of the distance of the target obstacle is greater than a preset threshold, the approaching trend of the obstacle is determined.

[0054] In this step, the spatial boundary of the touch area is determined according to the type of motor parameter mutation feature, and the touch time is calculated based on the change speed of the approaching trend of the obstacle and the current time.

[0055] In this step, the change rate of the distance of the target obstacle represents the change speed of the distance of the obstacle with time, with the unit of m / s. The preset threshold is the critical value for judging the fast approach of the obstacle, which is usually set to 2 m / s. The approaching trend of the obstacle represents the direction and speed characteristics of the relative motion between the obstacle and the UAV.

[0056] This step is executed in the process of continuous tracking of obstacles, for evaluating the collision risk. By analyzing the trend of the change of the obstacle distance, it is determined whether there is a potential collision threat. Specifically, the obstacle distance data is updated every 50 ms, and the change rate is calculated by dividing the difference between two adjacent measurement values by the time interval. When the change rate is greater than the preset threshold of 2 m / s, and this trend is maintained for 3 consecutive samplings, it is confirmed that there is a situation of rapid approach of the obstacle.

[0057] S103, based on the mutation feature analysis of the initial force state of the collision, the escape energy is calculated according to the spatial distribution of the touch area and the kinetic energy parameter, the motion range is determined by the attitude angle, and the optimal escape direction is generated based on the force state in the motion range. The optimal escape direction is the path direction with the minimum energy loss.

[0058] Wherein, the initial force state of the collision represents the distribution of external force and torque acting on the unmanned aerial vehicle at the moment of collision. The spatial distribution refers to the geometric shape and positional relationship of the touch area in three-dimensional space. The escape energy represents the kinetic energy reserve required for the unmanned aerial vehicle to escape from the collision area. The motion range refers to the motion space range that the unmanned aerial vehicle can achieve under the current attitude. The optimal escape direction represents the escape path with the minimum energy loss. The path direction refers to the direction vector of the center of mass of the unmanned aerial vehicle during the escape process. The energy loss refers to the kinetic energy consumed due to air resistance and attitude adjustment during the escape process.

[0059] This step is executed immediately after determining the collision risk, for calculating the risk avoidance path. When a collision risk occurs, it is necessary to quickly determine the best escape scheme to safely escape from the dangerous area with the minimum energy loss. Specifically, first, a force analysis model is established based on the mutation feature, and the impact force and torque generated by the collision are calculated. Considering factors such as air resistance and gravity, an energy balance equation is established to calculate the minimum kinetic energy required for escape. Then, the action range of the unmanned aerial vehicle is determined according to the current attitude angle, and a dynamic programming algorithm is used to search for the escape path with the minimum energy loss within the range.

[0060] In some embodiments, the generation of the optimal escape direction can be achieved in various ways: optionally, the escape direction is generated based on the potential field method: first, a repulsive force field model of the collision area is constructed, the touch area is set as the potential field source, the repulsive force in each direction is calculated, then the kinetic energy field is superimposed, the path with the minimum potential energy is searched within the action range, and finally the path is smoothed to obtain the final escape direction; optionally, the escape direction is generated based on the sampling method: a plurality of candidate directions are uniformly sampled within the action range, the complete motion trajectory of each direction is calculated, the energy loss of each trajectory is calculated through simulation, the trajectory with the minimum loss is selected as the escape direction, and real-time dynamic adjustment is performed. It can be understood that other methods can also be used to generate the optimal escape direction, which is not limited here.

[0061] In some embodiments, the step specifically includes:

[0062] According to the type of motor parameter mutation feature, the direction of the collision force is determined, the moment component generated by the collision is calculated based on the direction of the collision force and the attitude angle, and the moment component and the kinetic energy parameter are substituted into a preset force model to obtain an initial force state of the collision.

[0063] In this step, the direction of the collision force represents the spatial vector direction of the collision force. The moment component refers to the decomposition value of the moment along the three rotation axes generated by the collision. The force model is a mathematical model describing the transmission and action of the force in the collision process. The initial force state of the collision includes a complete mechanical description of the force size, direction and action point position.

[0064] This step is executed immediately after determining the collision type, and is used to establish a mechanical analysis model of the collision process. Based on the different force conditions corresponding to different types of collision features, the initial force state needs to be accurately calculated to guide the subsequent risk avoidance action. Specifically, first, the force direction is determined according to the type of mutation feature: for the type of rotational speed drop, the force direction is parallel to the rotor axis; for the type of rotational speed fluctuation, the force direction is at a 45-degree angle with the rotor plane; for the type of rotational speed block, the force direction is perpendicular to the rotor plane. Then, the force direction vector is coordinate-transformed with the current attitude angle to calculate the moment component in the body coordinate system. Finally, the moment component and the kinetic energy parameter are substituted into the rigid body collision model to solve the complete force state at the moment of collision.

[0065] The collision volume is calculated based on the spatial boundary of the touch area, the energy loss in the collision process is calculated based on the collision volume and the kinetic energy parameter, and the remaining kinetic energy is determined as the escape energy.

[0066] In this step, the collision volume represents the size of the space where the collision occurs. The energy loss refers to the part of the kinetic energy that is converted into heat energy and deformation energy in the collision process. The escape energy is the minimum kinetic energy reserve required to complete the risk avoidance action.

[0067] This step is executed after determining the force state, and is used to evaluate the energy conversion process of the collision. By analyzing the energy change in the collision process, it is determined whether the unmanned aerial vehicle has sufficient escape energy. Specifically, first, the collision volume is calculated according to the boundary of the touch area: for a spherical region, the volume V = 4 / 3πr³; for an ellipsoidal region, the volume V = 4 / 3πabc (a, b, c are the lengths of the three semi-axes). Then, the energy loss is calculated based on the collision volume: loss energy = collision volume x material characteristic coefficient x kinetic energy density. Finally, the remaining energy available for escape is obtained by subtracting the loss energy from the current kinetic energy.

[0068] According to the attitude angle, a three-dimensional space range in which the UAV can move is calculated, and an optimal escape direction is generated based on an initial force state of collision in the three-dimensional space range by using an energy optimization algorithm.

[0069] In this step, the three-dimensional space range refers to a space region in which the UAV can move at the current attitude. The energy optimization algorithm is a calculation method for finding a path with minimum energy consumption. The optimal escape direction represents a motion direction with minimum energy loss.

[0070] This step is executed after the escape energy is calculated, and is used for planning an optimal risk-avoiding path. Based on the dynamic characteristics of the UAV and environmental constraints, an escape path with the highest energy efficiency needs to be generated. Specifically, first, a motion space is calculated according to the current attitude angle: a spherical coordinate system is established with the current position of the UAV as the origin, and the attitude angle limit is converted into a feasible range of azimuth angle and pitch angle by using a rotation matrix transformation. Then, the A* algorithm is used for path searching in this range, and the energy consumption per unit displacement is used as the cost function, and the additional energy loss caused by the initial force of collision is considered, and the motion direction with the minimum total energy consumption is calculated iteratively.

[0071] S104, stopping the main rotor in the touch area, and calculating the target rotating speed of the second rotor and the third group of rotors according to the optimal escape direction and the touch time, and controlling the second rotor and the third group of rotors according to the target rotating speed, the main rotor being the rotor that collides with the obstacle, the second rotor being the opposite rotor at an angle of one hundred and eighty degrees with the main rotor, and the third group of rotors being the other rotors except the main rotor and the second rotor.

[0072] The main rotor refers to the rotor that directly collides with the obstacle. Stopping refers to the process of reducing the rotating speed of the rotor to zero. The target rotating speed refers to the working rotating speed that the other rotors need to reach. The second rotor refers to the rotor that is symmetrically distributed with the main rotor. The opposite rotor refers to the rotor that is opposite to the main rotor in the rotor layout. The third group of rotors refers to the other working rotors except the main rotor and the second rotor. Control refers to the process of achieving the target rotating speed by adjusting the motor input.

[0073] This step is executed after the optimal escape direction is determined, and is used for implementing specific risk-avoiding actions. When the risk-avoiding actions are executed, the working states of the rotors need to be coordinated to ensure that the UAV still has basic flight capability after the main rotor is stopped. Specifically, first, it is detected whether the main rotor is located in the touch area, and if so, a stop command is executed immediately. Then, the required thrust and moment are calculated according to the optimal escape direction, and a dynamic equation set is established combined with the touch time, and the target rotating speed that the second rotor and the third group of rotors need to reach is solved. Finally, the actual rotating speed of each rotor is made to follow the target value through closed-loop control.

[0074] In some embodiments, the coordinated control of the rotors can be achieved in various ways: optionally, a hierarchical control method is adopted: an upper controller calculates the desired resultant force and moment according to the escape direction, a middle controller distributes the force and moment to each rotor to obtain the target rotational speed, and a bottom controller executes the specific motor speed regulation, and different control periods are adopted in each layer of controller to ensure the real-time response; optionally, a predictive control method is adopted: a dynamic prediction model containing all rotors is established, and the rotor speed sequence is optimized in the prediction time domain, so that the predicted trajectory is closest to the desired escape path, and the control amount is updated in real time. It can be understood that other methods can also be used to achieve the coordinated control of the rotors, which are not limited here.

[0075] In some embodiments, the step specifically comprises:

[0076] Detecting whether the main rotor is located in the touch area, and when it is detected that the main rotor is located in the touch area, controlling the main rotor to stop rotating.

[0077] In this step, the touch area represents a dangerous space range determined according to the collision feature. The position detection refers to judging the relative relationship between the spatial position of the rotor and the touch area. The stop rotating refers to the control process of reducing the rotor speed to zero. The main rotor refers to the rotor that collides.

[0078] This step is continuously executed after determining the touch area, and is used to achieve the emergency stop of the colliding rotor. By monitoring the position of the rotor in real time and executing the stop instruction in time, the loss caused by the collision is reduced. Specifically, the real-time spatial coordinates of the main rotor are first obtained, which are substituted into the position judgment function with the boundary equation of the touch area: for a spherical area, it is judged whether the distance from the rotor to the center of the area is less than the radius of the sphere; for an ellipsoidal area, the rotor coordinates are substituted into the standard equation of the ellipsoid to verify whether the boundary condition is met. When the judgment result is true, a stop instruction is immediately sent to the motor driver to achieve rapid stop through increasing the back electromotive force braking coefficient. A typical stop process includes: first, cutting off the power supply of the motor, then applying a reverse current to generate a braking torque, and finally short-circuiting the motor to form a self-locking.

[0079] The desired acceleration is generated according to the optimal escape direction, and a dynamic equation set is established based on the desired acceleration and the touch time, and the target rotational speed of the second rotor and the third group of rotors is obtained by solving the dynamic equation set.

[0080] In this step, the desired acceleration represents the acceleration vector required to achieve the escape motion. The dynamic equation set is a set of mathematical equations describing the relationship between the motion of the unmanned aerial vehicle and the rotational speed of the rotor. The target rotational speed refers to the working rotational speed that the other rotors need to reach.

[0081] This step is executed after the optimal escape direction is determined, for calculating the working parameters of the compensating rotors. By establishing and solving the dynamic equations, the specific control amount required to maintain flight is determined. Specifically, first multiply the optimal escape direction unit vector by the desired speed, and then divide by the preset acceleration time (usually 0.5 seconds) to obtain the desired acceleration. Then establish an equation set containing force balance equations and moment balance equations: ∑F = ma represents the relationship between the resultant force and the acceleration, and ∑M = Jα represents the relationship between the moment and the angular acceleration. The thrust and moment generated by each rotor are expressed as a quadratic function of the rotational speed, which is substituted into the equation set. Finally, the equation set is solved by a numerical method (such as the Newton-Raphson method) to obtain the target rotational speed values of the second rotor and the third group of rotors.

[0082] According to the target rotational speed, the rotational speed of the second rotor and the third group of rotors is closed-loop controlled, so that the actual rotational speed of the second rotor and the third group of rotors matches the target rotational speed.

[0083] In this step, closed-loop control refers to the process of continuously adjusting the control amount based on feedback information. Actual rotational speed refers to the current rotational speed of the rotor. Rotational speed matching refers to controlling the deviation between the actual rotational speed and the target rotational speed within the allowable range.

[0084] This step is continuously executed after obtaining the target rotational speed, for realizing precise rotational speed adjustment. By real-time feedback control, the rotor rotational speed is ensured to always follow the target value changes. Specifically, an independent PID controller is established for each rotor, with a control period of 10 ms. The controller takes the rotational speed deviation e(t) = target rotational speed - actual rotational speed as input, and calculates the control amount u(t) = Kp·e(t) + Ki·∫e(t)dt + Kd·de(t) / dt. Where the proportional coefficient Kp = 0.5, the integral coefficient Ki = 0.1, and the differential coefficient Kd = 0.05. The control amount is transmitted to the motor driver through a PWM signal to adjust the motor input voltage. At the same time, the deviation between the actual rotational speed and the target rotational speed is monitored, and when the deviation is less than ±50 rpm, it is considered to meet the matching requirements.

[0085] The method provided by the embodiment is further described in more detail below. Please refer to Figure 2 , which is another flowchart of the rotor collision warning and automatic shutdown method in the embodiment of the present application.

[0086] S201, obtain the feature type of the motor parameter mutation feature, and retrieve the corresponding emergency control strategy from the preset escape mode library according to the feature type, the emergency control strategy including the shutdown time sequence of the main rotor and the rotational speed adjustment sequence of the second rotor and the third group of rotors.

[0087] The feature type of the motor parameter mutation feature refers to the parameter change mode exhibited by the rotor motor in the collision process, mainly including three types of rotational speed sudden drop type, rotational speed fluctuation type and rotational speed block type. The preset escape mode library is a set of emergency control schemes preset for different collision feature types. The emergency control strategy consists of two parts: the main rotor stop timing defines the time process of the collision rotor from starting to decelerate to completely stopping, and the rotational speed adjustment sequence of the second rotor and the third group of rotors defines the rotational speed change curve of the other rotors in this process.

[0088] This step first determines the collision type by analyzing the change characteristics of motor speed, current and other parameters. For the rotational speed sudden drop type, the motor speed drops rapidly within a short time by more than 50%; for the rotational speed fluctuation type, the rotational speed fluctuates up and down and the fluctuation amplitude is more than 30%; for the rotational speed block type, the rotational speed drops slowly but the current increases significantly. After determining the type, the corresponding control strategy is retrieved from the escape mode library. For example, for the rotational speed sudden drop type collision, a fast stop strategy is adopted, the main rotor is completely stopped within 0.1 seconds, the second rotor maintains 90% rated speed, and the third group of rotors gradually increases to 110% rated speed. For the rotational speed fluctuation type, a gradual stop strategy is adopted, the main rotor is stopped by segmented deceleration within 0.3 seconds, and the second rotor and the third group of rotors adjust the rotational speed according to the preset curve. By executing the control strategy matched with the collision feature, the collision process is accurately controlled.

[0089] S202, set control priority based on emergency control strategy, so that the execution priority of the emergency control strategy is higher than that of the real-time control instruction based on the optimal escape direction.

[0090] The control priority refers to the execution sequence when multiple control instructions exist at the same time. The emergency control strategy is a control sequence optimized in advance for the collision scenario. The real-time control instruction is a control quantity generated based on the optimal escape direction calculated based on the current state.

[0091] This step sets the priority mechanism of the controller to ensure that the execution of the emergency control strategy is not disturbed by the real-time control instruction. In specific implementation, a double-layer control structure is established inside the controller: the upper layer is an emergency control strategy executor that directly receives the preset rotational speed adjustment sequence; the lower layer is a real-time control executor that processes the control instruction calculated based on the optimal escape direction. When a collision is detected and the emergency control strategy is started, the upper controller locks the control right and temporarily shields the real-time control instruction from the lower layer. After the execution of the emergency control strategy is completed, the instruction execution right of the lower controller is restored. This layered control structure ensures the continuity and reliability of the execution of the control strategy in the collision process.

[0092] S203, according to the real-time feedback value of the rotor motor speed and the attitude angle, the deviation from the preset speed in the emergency control strategy is calculated, and the speed of the second rotor and the third group of rotors is compensated and adjusted based on the deviation.

[0093] The rotor motor speed refers to the actual rotating speed of each rotor, which is obtained by real-time measurement through a motor encoder. The attitude angle includes the roll angle, pitch angle and yaw angle of the unmanned aerial vehicle, which is provided by an inertial measurement unit. The preset speed is the target speed value specified in the emergency control strategy. The speed deviation represents the difference between the actual speed and the preset speed.

[0094] This step realizes accurate adjustment of the speed through closed-loop control. First, the real-time speed of each rotor and the attitude angle of the unmanned aerial vehicle are obtained, and the measured speed is compared with the preset speed at the corresponding time in the emergency control strategy to calculate the speed deviation value. Then, according to the deviation value, a compensation control amount is designed: when the deviation is positive, the motor input voltage is reduced to reduce the speed; when the deviation is negative, the motor input voltage is increased to increase the speed. The size of the compensation control amount is proportional to the deviation value, and the proportional coefficient is determined through experiment calibration. Independent closed-loop control is performed for the second rotor and the third group of rotors respectively to realize synchronous following of the speed of each rotor to the preset control strategy.

[0095] S204, when the execution of the emergency control strategy is completed, it is judged whether the restart condition of the main rotor is met based on the flight state parameters, and when the restart condition is met, the speed of the main rotor is adjusted to the rated working speed according to the preset speed-time curve.

[0096] The flight state parameters include the flight height, speed, attitude angle and acceleration of the unmanned aerial vehicle. The restart condition refers to the environmental and state requirements for allowing the main rotor to resume work, including obstacle distance, attitude stability and remaining energy, etc. The speed-time curve defines the process of gradually accelerating the main rotor from the stopped state to the working speed. The rated working speed refers to the rated operating speed of the main rotor of the unmanned aerial vehicle in the normal flight state.

[0097] This step determines whether the main rotor meets the restart conditions through multiple judgments after the emergency control strategy is executed. First, it detects whether the obstacle distance is greater than the safety threshold (usually 3 meters), whether the absolute values of the roll angle and the pitch angle are less than 5 degrees, and whether the remaining battery power is higher than 30%. When these conditions are met simultaneously, the main rotor restart program is started. The restart process uses a segmented acceleration method: in the first stage (0-0.5 seconds), the speed is increased from 0 to 20% of the rated speed; in the second stage (0.5-1.5 seconds), it is linearly increased to 60% of the rated speed; in the third stage (1.5-2.5 seconds), it is gradually increased to 100% of the rated speed. During the entire acceleration process, the motor current and temperature are continuously monitored, and if an abnormality occurs, the restart is immediately aborted. Through this gradual restart method, the main rotor is ensured to recover to a stable working state.

[0098] S205, obtain the moment of inertia parameter of the main rotor and the current motor torque value, and calculate the minimum braking distance of the main rotor according to the moment of inertia parameter and the current motor torque value.

[0099] The moment of inertia parameter represents the inertia of the rotor rotating around its axis, which is related to the mass distribution and geometric size of the rotor. The motor torque value refers to the torque size on the output shaft of the motor, which is collected in real time through the motor driver. The minimum braking distance defines the shortest distance required for the rotor to completely stop from the current working state.

[0100] This step determines the braking characteristics of the rotor through dynamic calculation. First, the moment of inertia J (unit: kg·m²) of the main rotor and the current motor torque T (unit: N·m) are obtained. According to the law of conservation of angular momentum, the angular deceleration α = T / J of the rotor is calculated. When the current rotor angular velocity is ω, the time t required for complete stop is ω / α. During this braking process, the angle θ = ωt / 2 rotated by the rotor is converted into a linear distance d = θr (r is the rotor radius), which is the minimum braking distance. For example, for a certain type of unmanned aerial vehicle main rotor with a moment of inertia of 0.02 kg·m² and a maximum braking torque of 2 N·m, when the working speed is 6000 rpm, the calculated minimum braking distance is about 0.8 meters.

[0101] S206, based on the minimum braking distance, a collision safety buffer zone is delineated, and the boundary position of the collision safety buffer zone is taken as a warning threshold for triggering the main rotor stop.

[0102] The collision safety buffer zone is a spatial range delineated by adding a safety margin to the minimum braking distance. The warning threshold is the distance criterion for triggering the main rotor stop operation. The boundary position refers to the outer contour of the buffer zone.

[0103] This step is based on the minimum braking distance to build a collision avoidance safety mechanism. Multiply the minimum braking distance by a safety factor (1.5) to get the basic buffer distance, and then consider the measurement error of the ranging sensor (±0.1 meters) and environmental interference factors to determine the range of the collision safety buffer zone. Take the minimum braking distance of 0.8 meters as an example, and set the radius of the buffer zone to 1.3 meters. When the obstacle enters this range, the pre-stop rotation program of the main rotor is triggered immediately. The shape of the buffer zone is determined according to the rotor rotation plane: circular in the horizontal direction and elliptical in the vertical direction to adapt to the braking characteristics in different directions. Through this buffer zone design based on the dynamics characteristics, early warning and disposal of collision risks are realized.

[0104] S207, when the target obstacle distance is less than the warning threshold, the rotation speed of the main rotor is reduced to a preset safe rotation speed in advance.

[0105] The target obstacle distance is the actual distance from the unmanned aerial vehicle to the obstacle measured by laser ranging or ultrasonic sensor. The warning threshold is the boundary distance of the collision safety buffer zone mentioned above. The preset safe rotation speed is the reduced running rotation speed value determined after considering the collision risk, which is usually set to 30%-50% of the calibrated working rotation speed.

[0106] This step prevents and mitigates collisions by actively reducing speed. When the ranging sensor detects that the obstacle distance is less than the warning threshold (1.3 meters), the control system immediately starts the speed reduction program. The speed reduction process is divided into two stages: rapid speed reduction and stable operation. The rapid speed reduction stage lasts for 0.2 seconds, and the rotation speed is rapidly reduced from the calibrated working rotation speed (6000 rpm) to the preset safe rotation speed (2400 rpm) by increasing the motor braking current. After entering the stable operation stage, the control system maintains the stability of the safe rotation speed through the PI controller, and controls the rotation speed fluctuation range within ±100 rpm. At the same time, the remaining thrust after speed reduction is calculated in real time to ensure that it is greater than 60% of the weight of the unmanned aerial vehicle to maintain basic flight ability. If the obstacle distance continues to decrease, the rotation speed will be further reduced until the complete stop is triggered.

[0107] S208, get the current spatial orientation of the main rotor, and divide the main rotor into an obstacle-facing end and a far-obstacle end.

[0108] The spatial orientation of the main rotor refers to the azimuth and pitch angle of the rotor rotation plane relative to the obstacle. The obstacle-facing end refers to the sector area on the rotor rotation plane closest to the obstacle. The far-obstacle end refers to the sector area opposite to the obstacle-facing end.

[0109] This step establishes the spatial relationship model between the rotor and the obstacle. First, the spatial attitude of the main rotor rotation plane is measured by the gyroscope and magnetometer, and the angle between the rotor plane and the obstacle line is calculated combined with the three-dimensional coordinates of the obstacle. Based on this angle, the rotor circumference is evenly divided into two 180-degree sectors: the smaller angle side is defined as the obstacle-facing end, and the reverse side is defined as the obstacle-avoiding end. The instantaneous rotation position of the rotor is determined by the motor encoder signal, and the spatial range of each sector is updated in real time. This dynamic partitioning method provides a spatial reference for subsequent differentiated control.

[0110] S209, control the rotor twist angle of the obstacle-facing end to increase by a first preset angle, and control the rotor twist angle of the obstacle-avoiding end to decrease by a second preset angle.

[0111] The rotor twist angle refers to the inclination angle of the rotor blade relative to the rotation plane. The first preset angle and the second preset angle are the target twist angle changes of the rotor blades of the obstacle-facing end and the obstacle-avoiding end, respectively, and their values are determined through wind tunnel tests.

[0112] This step realizes the differentiated twist control of the rotor blades. In the obstacle-facing end, the rotor twist angle is increased by 3 degrees (first preset angle) through the steering drive, so that the region generates an outward deflection force; in the obstacle-avoiding end, the rotor twist angle is reduced by 2 degrees (second preset angle), generating an inward deflection force. The adjustment of the twist angle adopts a gradual change process of 0.1 seconds to avoid vibration caused by sudden changes. The difference in twist angles between the two ends causes the rotor to generate uneven lift distribution during rotation, forming a resultant force that makes the rotor as a whole deviate from the obstacle. The control system adjusts the ratio of the two preset angles in real time to achieve precise control of the deflection effect.

[0113] S210, calculate the deflection force generated by the main rotor according to the change of the twist angle, and use the deflection force to make the main rotor generate a preset deflection speed around the rotor shaft.

[0114] The deflection force is an asymmetric aerodynamic force caused by the change of the rotor twist angle, and its size is related to the twist angle, air density, and rotor rotation speed. The preset deflection speed refers to the target deflection angular velocity of the main rotor around its axis. The rotor shaft refers to the central axis of the rotor rotation.

[0115] This step determines the deflection characteristics of the rotor through aerodynamic calculation. First, the lift and drag generated by a single rotor blade at different twist angles are calculated based on the blade element theory: for the near-end (twist angle increases by 3 degrees) and the far-end (twist angle decreases by 2 degrees), the lift component F_L perpendicular to the plane of rotation and the drag component F_D parallel to the plane of rotation are calculated respectively. The lift coefficient C_L and the drag coefficient C_D are obtained by looking up the table, combined with the air density ρ, the rotor area S, and the current speed v, to calculate the force F = 1 / 2·ρ·v²·S·C. The difference between the forces at the near-end and the far-end is projected onto the horizontal plane to obtain the resultant force F_t that causes the overall deflection of the rotor. According to the moment balance equation M = F_t·r (r is the rotor radius), the deflection moment is calculated. Finally, according to the moment of inertia J of the rotor, the angular acceleration α = M / J is solved, and the time required to reach the preset deflection speed (0.5 rad / s) is determined.

[0116] S211, detect the difference between the actual deflection speed of the main rotor and the preset deflection speed, and when the difference is greater than the preset threshold, adjust the twist angle change rate of the near-end and the far-end.

[0117] The actual deflection speed is obtained through gyroscope measurement. The preset threshold is the upper limit of the allowed deflection speed error, which is 0.1 rad / s. The twist angle change rate refers to the speed at which the twist angle of the rotor blade changes over time.

[0118] This step realizes closed-loop control of the deflection speed. The control system samples the actual deflection speed every 10 ms and compares it with the preset value of 0.5 rad / s to calculate the error. When the error exceeds the threshold of 0.1 rad / s, the twist angle adjustment program is started. If the actual speed is too low, increase the change rate of the near-end twist angle (from 0.1 degrees / ms to 0.15 degrees / ms), while reducing the change rate of the far-end (from 0.1 degrees / ms to 0.05 degrees / ms); if the actual speed is too high, adjust the change rates of the two ends in the opposite direction. Through this differentiated rate adjustment, precise control of the deflection speed is achieved. During the control process, it is continuously monitored whether the twist angle exceeds the mechanical limit (±5 degrees), and if it does, the corresponding change rate is immediately reduced.

[0119] S212, according to the twist angle change rate, recalculate the force distribution of the main rotor, convert the force distribution into the compensation speed of the second rotor and the third group of rotors, and adjust the target speed of the second rotor and the third group of rotors through the compensation speed.

[0120] The force distribution refers to the size and direction of the aerodynamic force acting on each point of the main rotor. The compensation speed is the speed adjustment amount applied to other rotors to balance the deflection effect of the main rotor. The target speed is the final working speed that each rotor needs to reach.

[0121] This step coordinates the deflection of the main rotor with the overall attitude control. According to the rate of change of the twist angle, the aerodynamic force distribution of each sector of the main rotor is calculated using computational fluid dynamics model. These forces are decomposed in the body coordinate system to obtain the resulting force and moment. To offset these additional forces and moments, the rotational speed of the second rotor and the third group of rotors need to be compensated. The calculation of the compensation speed uses the inverse dynamics method: the dynamic equation set containing all rotors is established, and the balance of the force and moment generated by the main rotor is taken as the constraint condition to solve the rotational speed adjustment amount required by each rotor. The second rotor, as the counter-rotor, its compensation speed is proportional to the deflection force of the main rotor; the third group of rotors is allocated different compensation speeds according to its spatial position to balance the remaining moment components. Finally, the compensation speed is superimposed on the original target speed, and the speed regulation is executed through the motor driver.

[0122] The rotor collision early warning and automatic stop system in the embodiment of the present application is described from the perspective of hardware processing. Please refer to Figure 3 FIG. 1 is a schematic structural diagram of an entity device of the rotor collision early warning and automatic stop system in the embodiment of the present application.

[0123] It should be noted that Figure 3 The structure of the rotor collision early warning and automatic stop system shown is only an example, and should not bring any limitation to the function and use range of the embodiment of the present application.

[0124] As Figure 3 shown, the rotor collision early warning and automatic stop system includes a central processing unit (CPU) 301, which can perform various appropriate actions and processes according to the program stored in a read-only memory (ROM) 302 or the program loaded from a storage part 308 to a random access memory (RAM) 303, such as performing the method described in the above embodiment. In the RAM 303, various programs and data required for system operation are also stored. The CPU 301, the ROM 302, and the RAM 303 are connected to each other through a bus 304. An input / output (I / O) interface 305 is also connected to the bus 304.

[0125] The following components are connected to the I / O interface 305: an input section 306 including an audio input device, a push button switch, and the like; an output section 307 including a Liquid Crystal Display (LCD), and an audio output device, a lamp, and the like; a storage section 308 including a hard disk and the like; and a communication section 309 including a network interface card such as a LAN (Local Area Network) card, a modem, and the like. The communication section 309 performs a communication process via a network such as the Internet. A drive 310 is also connected to the I / O interface 305 as necessary. A removable medium 311, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, and the like, is attached to the drive 310 as necessary so that a computer program read therefrom can be installed into the storage section 308 as necessary.

[0126] In particular, the processes described above with reference to the flowcharts can be implemented as a computer software program in accordance with embodiments of the present application. For example, embodiments of the present application include a computer program product comprising a computer program carried on a computer readable medium, the computer program containing a computer program for executing the methods illustrated by the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via the communication section 309, and / or installed from the removable medium 311. When the computer program is executed by the central processing unit (CPU) 301, various functions defined in the present application are performed.

[0127] Note that specific examples of the computer readable storage medium can include but are not limited to one or more of the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read only memory (ROM), an erasable programmable read only memory (EPROM), a flash memory, a optical fiber, a portable compact disc read only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the present application, a computer readable storage medium can be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0128] The computer program product of the present application can be a computer program embodied on a non-transitory computer readable medium. When the computer program runs on a computing device, various steps of a method according to the present application are performed. The computing device can be any kind of device which is able to process data, including a computer, a mobile phone (like a smart phone), a PDA (Personal Digital Assistant), a server or another type of computing device.

[0129] In particular, the rotor collision early warning and automatic shutdown system of the embodiment includes a processor and a memory, and the memory stores a computer program. When the computer program is executed by the processor, the rotor collision early warning and automatic shutdown method provided in the above embodiment is implemented.

[0130] As another aspect, the present application also provides a computer readable storage medium. The storage medium can be included in the rotor collision early warning and automatic shutdown system described in the above embodiments, or can exist independently without being assembled into the rotor collision early warning and automatic shutdown system. The storage medium carries one or more computer programs. When the one or more computer programs are executed by a processor of the rotor collision early warning and automatic shutdown system, the rotor collision early warning and automatic shutdown system implements the rotor collision early warning and automatic shutdown method provided in the above embodiments.

[0131] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the present application; even though the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0132] In the above embodiments, according to the context, the term "when" can be interpreted as meaning "if" or "after" or "in response to determining" or "in response to detecting". Similarly, according to the context, the phrase "upon determining" or "if detecting (the stated condition or event)" can be interpreted as meaning "if determining" or "in response to determining" or "upon detecting (the stated condition or event)" or "in response to detecting (the stated condition or event)".

[0133] Those skilled in the art can understand that all or part of the processes in the above-mentioned method embodiments can be implemented by a computer program instructing relevant hardware to complete, the program can be stored in a computer readable storage medium, and the program can include the processes of the above-mentioned method embodiments when executed. The aforementioned storage medium includes ROM or random storage memory RAM, magnetic disc or optical disc and various storage code medium.

Claims

1. A method for rotor collision warning and automatic shutdown, characterized in that, The method is applied to a rotor collision early warning and automatic stop system, and comprises the following steps: Obtaining flight state parameters and environment perception data of a target unmanned aerial vehicle, wherein the flight state parameters comprise rotor motor speed, attitude angle and kinetic energy parameters, and the environment perception data comprises target obstacle distance; Identifying motor parameter mutation characteristics according to the change trend of the flight state parameters, judging obstacle approaching trend based on the environment perception data, determining a collision area and a collision time based on the motor parameter mutation characteristics and the obstacle approaching trend, wherein the motor parameter mutation characteristics represent a collision initial state, and the collision area represents a spatial range of collision; Determining a collision force direction according to the type of the motor parameter mutation characteristics, calculating a collision generated torque component based on the collision force direction and the attitude angle, and obtaining the collision initial force state by substituting the torque component and the kinetic energy parameters into a preset force model; Calculating a collision volume based on the spatial boundary of the collision area, calculating energy loss in a collision process according to the collision volume and the kinetic energy parameters, and determining remaining kinetic energy as the escape energy; Calculating a three-dimensional space range in which the unmanned aerial vehicle can move according to the attitude angle, and generating the optimal escape direction in the three-dimensional space range based on the collision initial force state by using an energy optimal algorithm, wherein the optimal escape direction is a path direction with minimum energy loss; Stopping a main rotor in the collision area, calculating target speeds of a second rotor and a third group of rotors according to the optimal escape direction and the collision time, and controlling the second rotor and the third group of rotors according to the target speeds, wherein the main rotor is a rotor that collides, the second rotor is a counter-rotor with a one-hundred-and-eighty-degree included angle with the main rotor, and the third group of rotors are other rotors except the main rotor and the second rotor.

2. The method of claim 1, wherein, The steps of identifying motor parameter mutation characteristics according to the change trend of the flight state parameters, judging obstacle approaching trend based on the environment perception data, and determining a collision area and a collision time based on the motor parameter mutation characteristics and the obstacle approaching trend, specifically comprise the following steps: Obtaining rotor motor speed change rate and attitude angle change rate in a preset time window, calculating a speed mutation amplitude based on the rotor motor speed change rate, and calculating an attitude mutation amplitude based on the attitude angle change rate; Judging the type of the motor parameter mutation characteristics according to the speed mutation amplitude and the attitude mutation amplitude; Obtaining a change rate of the target obstacle distance, and determining the obstacle approaching trend when the change rate of the target obstacle distance is greater than a preset threshold value; Drawing the spatial boundary of the collision area according to the type of the motor parameter mutation characteristics, and calculating the collision time based on the change speed of the obstacle approaching trend and the current time.

3. The method of claim 1, wherein, The steps of stopping the main rotor in the collision area, calculating target speeds of a second rotor and a third group of rotors according to the optimal escape direction and the collision time, and controlling the second rotor and the third group of rotors according to the target speeds, specifically comprise the following steps: detecting whether the main rotor is located in the touch area, and controlling the main rotor to stop rotating when it is detected that the main rotor is located in the touch area; generating an expected acceleration according to the optimal escape direction, establishing a dynamic equation set based on the expected acceleration and the touch time, and solving the dynamic equation set to obtain target rotating speeds of the second rotor and the third group of rotors; performing closed-loop control on the rotating speeds of the second rotor and the third group of rotors according to the target rotating speeds, so that the actual rotating speeds of the second rotor and the third group of rotors match the target rotating speeds.

4. The method of claim 1, wherein, After the steps of stopping the main rotor in the touch area, calculating the target rotating speeds of the second rotor and the third group of rotors according to the optimal escape direction and the touch time, and controlling the second rotor and the third group of rotors according to the target rotating speeds, the method further comprises: obtaining a feature type of the motor parameter mutation feature, and calling a corresponding emergency control strategy from a preset escape mode library according to the feature type, the emergency control strategy including a stop time sequence of the main rotor and a rotating speed adjustment sequence of the second rotor and the third group of rotors; setting a control priority based on the emergency control strategy, so that the execution priority of the emergency control strategy is higher than that of a real-time control instruction based on the optimal escape direction; calculating a deviation from a preset rotating speed in the emergency control strategy according to real-time feedback values of the rotor motor rotating speed and the attitude angle, and compensating and adjusting the rotating speeds of the second rotor and the third group of rotors based on the deviation; after the execution of the emergency control strategy is completed, judging whether a restart condition of the main rotor is met based on the flight state parameters, and adjusting the rotating speed of the main rotor to a designated working rotating speed according to a preset rotating speed-time curve when the restart condition is met.

5. The method of claim 1, wherein, After the steps of stopping the main rotor in the touch area, calculating the target rotating speeds of the second rotor and the third group of rotors according to the optimal escape direction and the touch time, and controlling the second rotor and the third group of rotors according to the target rotating speeds, the method further comprises: obtaining a rotating inertia parameter and a current motor torque value of the main rotor, and calculating a minimum braking distance of the main rotor according to the rotating inertia parameter and the current motor torque value; based on the minimum braking distance, demarcating a collision safety buffer zone, and taking a boundary position of the collision safety buffer zone as a warning threshold for triggering the stopping of the main rotor; when the target obstacle distance is less than the warning threshold, reducing the rotating speed of the main rotor to a preset safety rotating speed in advance.

6. The method of claim 5, wherein, After the steps of stopping the main rotor in the touch area, calculating the target rotating speeds of the second rotor and the third group of rotors according to the optimal escape direction and the touch time, and controlling the second rotor and the third group of rotors according to the target rotating speeds, the method further comprises: obtaining a current spatial orientation of the main rotor, and dividing the main rotor into an obstacle-facing end and an obstacle-remote end; controlling the rotor torsion angle of the obstacle-facing end to increase by a first preset angle, and controlling the rotor torsion angle of the obstacle-remote end to decrease by a second preset angle; calculating a deflection force generated by the main rotor according to the change of the twist angle, and using the deflection force to generate a preset deflection speed of the main rotor around a rotor shaft; detecting a difference between an actual deflection speed of the main rotor and the preset deflection speed, and adjusting a change rate of the twist angle of the leading end and the trailing end when the difference is greater than a preset threshold; recomputing a force distribution of the main rotor according to the change rate of the twist angle, converting the force distribution into a compensation rotating speed of the second rotor and the third group of rotors, and adjusting a target rotating speed of the second rotor and the third group of rotors through the compensation rotating speed.

7. A rotor collision warning and automatic shutdown system, characterized by, The rotor collision warning and automatic stop system comprises one or more processors and a memory; the memory is coupled with the one or more processors, and the memory is used to store computer program codes, the computer program codes comprise computer instructions, and the one or more processors invoke the computer instructions to enable the rotor collision warning and automatic stop system to perform the method in any one of claims 1-6.

8. A computer-readable storage medium comprising instructions, characterized in that, When the instructions run on the rotor collision warning and automatic stop system, the rotor collision warning and automatic stop system is enabled to perform the method in any one of claims 1-6.

9. A computer program product, characterised in that, When the computer program product runs on the rotor collision warning and automatic stop system, the rotor collision warning and automatic stop system is enabled to perform the method in any one of claims 1-6.

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