CN113581448A - Microminiature unmanned aerial vehicle using grid rudder and control method - Google Patents
Microminiature unmanned aerial vehicle using grid rudder and control method Download PDFInfo
- Publication number
- CN113581448A CN113581448A CN202110843597.6A CN202110843597A CN113581448A CN 113581448 A CN113581448 A CN 113581448A CN 202110843597 A CN202110843597 A CN 202110843597A CN 113581448 A CN113581448 A CN 113581448A
- Authority
- CN
- China
- Prior art keywords
- aerial vehicle
- unmanned aerial
- grid
- grid control
- control surfaces
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C9/00—Adjustable control surfaces or members, e.g. rudders
- B64C9/02—Mounting or supporting thereof
Landscapes
- Engineering & Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Control Of Position, Course, Altitude, Or Attitude Of Moving Bodies (AREA)
Abstract
The invention discloses a micro unmanned aerial vehicle using a grid rudder and a control method, and belongs to the field of attitude control of micro aircrafts. Unmanned aerial vehicle adopts cylindric shell, and four grid control faces are in cylindric unmanned aerial vehicle shell bottom with horizontal installation mode evenly distributed, and the center of symmetry of four grid control faces is on same vertical line with unmanned aerial vehicle's focus, and unmanned aerial vehicle's screw is in cylindric unmanned aerial vehicle shell top, and the grid control face is installed in unmanned aerial vehicle's bottom and is used for unmanned aerial vehicle's attitude control. Compared with a flat control surface on a conventional small unmanned aerial vehicle, the grid control surface has more excellent pneumatic characteristics, has more excellent control performance when being applied to the micro unmanned aerial vehicle, and can effectively reduce the influence of side wind. According to the invention, through numerical simulation and flight test in windless and windy environments, the aerodynamic characteristics and the control performance of the grid control surface are more superior to those of the conventional flat control surface through simulation calculation and test results.
Description
Technical Field
The invention relates to a micro unmanned aerial vehicle using a grid rudder and a control method, belonging to the field of attitude control of micro aircrafts.
Background
The grid rudder is an unconventional aerodynamic lift and control layout, which is a spatial multi-lift surface system made up of an outer frame of small chord length and numerous inner panels. The method plays a great role in the fields of missile guidance, satellites and the like at present. However, the control research and application of the grid rudder on the microminiature aircraft is almost zero so far. The cross wind is a fatal pain point for a micro aircraft, the micro aircraft generally uses a flat control surface, the pneumatic characteristic of the flat control surface has unsatisfactory effect on the micro unmanned aerial vehicle, and the influence on the unmanned aerial vehicle on offsetting the cross wind, posture change, motion control and the like is very limited.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects of the prior art, the invention aims to provide a micro unmanned aerial vehicle using a grid rudder and a control method, which can enhance the robustness of the unmanned aerial vehicle to resist the influence of side wind and improve the control characteristic of the unmanned aerial vehicle.
The technical scheme is as follows: in order to achieve the purpose, the invention adopts the following technical scheme:
the unmanned aerial vehicle adopts a cylindrical shell, four grid control surfaces are uniformly distributed at the bottom of the cylindrical unmanned aerial vehicle shell in a horizontal installation mode, and the symmetric centers of the four grid control surfaces and the gravity center of the unmanned aerial vehicle are on the same vertical line; a propeller of the unmanned aerial vehicle is arranged above the top of the cylindrical unmanned aerial vehicle shell; the first and second grid control surfaces positioned at the left and right sides of the unmanned aerial vehicle are marked as a first pair of grid control surfaces, and the third and fourth grid control surfaces positioned at the front and the rear sides of the unmanned aerial vehicle are marked as a second pair of grid control surfaces; the deflection angle of the grid control surface and the acting force of the propeller wake of the unmanned aerial vehicle on the control surface are in a linear relation; the first pair of grid control surfaces is used for controlling the front and back movement of the unmanned aerial vehicle, and the second pair of grid control surfaces is used for controlling the steering movement of the unmanned aerial vehicle.
Preferably, the grid rudder is a honeycomb grid rudder surface with an inclined wall and a frame forming an angle of 45 degrees, so that the strength of the rudder surface is enhanced.
Preferably, the propeller of the unmanned aerial vehicle adopts coaxial double propellers to overcome the self-rotating torque generated by the single propeller, and the length of the propeller is larger than that of the grid control surface.
Preferably, the weight of the drone is between 600g and 700 g.
The method for controlling the micro unmanned aerial vehicle by using the grid rudder realizes the back-and-forth movement and the steering movement of the unmanned aerial vehicle by controlling the deflection angles of four grid rudder surfaces arranged at the bottom of the unmanned aerial vehicle; the four grid control surfaces are uniformly distributed at the bottom of the cylindrical unmanned aerial vehicle shell in a horizontal installation mode, and the symmetric centers of the four grid control surfaces and the gravity center of the unmanned aerial vehicle are on the same vertical line; a propeller of the unmanned aerial vehicle is arranged above the top of the cylindrical unmanned aerial vehicle shell; the first and second grid control surfaces positioned at the left and right sides of the unmanned aerial vehicle are marked as a first pair of grid control surfaces, and the third and fourth grid control surfaces positioned at the front and the rear sides of the unmanned aerial vehicle are marked as a second pair of grid control surfaces; the method comprises the following steps:
when a reference pitch angle given by an inertial measurement unit IMU is received, calculating the resultant moment of the unmanned aerial vehicle according to a dynamic equation and a kinematic equation of the aircraft, further determining the aerodynamic moment generated by the propeller wake flow on the first pair of grid control surfaces, and determining the reference deflection angle of the first pair of grid control surfaces according to the linear relation between the grid control surface deflection angle and the aerodynamic moment; calculating a PWM value according to the reference deflection angle, outputting a PWM signal to a steering engine of the first pair of grid control surfaces, completing the deflection of the first pair of grid control surfaces, and realizing the front-back motion of the unmanned aerial vehicle;
when a reference roll angle given by an inertial measurement unit IMU is received, calculating the resultant moment of the unmanned aerial vehicle according to a dynamic equation and a kinematic equation of the aircraft, further determining the aerodynamic moment generated by the propeller wake flow on the second pair of grid control surfaces, and determining the reference deflection angle of the second pair of grid control surfaces according to the linear relation between the grid control surface deflection angle and the aerodynamic moment; and calculating a PWM value according to the reference deflection angle, outputting a PWM signal to a steering engine of the second pair of grid control surfaces, finishing the deflection of the second pair of grid control surfaces and realizing the steering motion of the unmanned aerial vehicle.
Preferably, the linear relation between the grid control surface deflection angle and the aerodynamic moment is obtained by multiplying the linear relation between the grid control surface deflection angle and the aerodynamic force, which are fitted, by the moment arm from the grid control surface to the axis of the unmanned aerial vehicle; the linear relation between the grid control surface deflection angle and the aerodynamic force is obtained through Fluent numerical simulation.
Preferably, when numerical simulation is carried out through Fluent, a closed cylindrical space is used as an air domain during simulation, the height of the air domain is 15-20 times of the thickness of the grid control surface, and the diameter length of the cross section is 3-4 times of the length of the grid control surface.
Preferably, the linear relationship between the grid control surface deflection angle and the aerodynamic moment is expressed as:
wherein M isareo,1、Mareo,2、Mareo,3、Mareo,4The magnitude of the moment, gamma, generated by the first, second, third and fourth grid control surfaces respectivelylIs the included angle between the first and second grid control surfaces and the horizontal plane, gammarIs the included angle between the control plane of the third and fourth grids and the horizontal plane, LlThe length of the force arm from the first grid control surface and the second grid control surface to the axis of the unmanned aerial vehicle, LrThe length of the force arm from the third and fourth grid control surfaces to the axis of the unmanned aerial vehicle, CldrAnd CmdeAnd delta is a linear coefficient of the grid control surface simulated by Fluent under corresponding conditions for corresponding dimensionless aerodynamic coefficients.
Preferably, the aircraft's equations of dynamics are expressed as:
the kinematic equation for an aircraft is expressed as:
wherein, [ L M N]TThree components of resultant moment in the coordinate system of the body, [ p, q, r]TThe angular velocity vector is three components of the body coordinate system, points on the variables represent derivatives, theta is a pitch angle, phi is a roll angle, psi is a yaw angle, and I isxx、Iyy、Izz、Ixz、IzxIs the rotational inertia of the unmanned plane
The respective components of (a); under the organism coordinate system, the origin of coordinates is located the unmanned aerial vehicle barycenter, the directional unmanned aerial vehicle the place ahead of X axle perpendicular to organism axis of ordinates, the directional unmanned aerial vehicle right side of Y axle perpendicular to organism axis of ordinates, and the Z axle points down along the organism axis of ordinates.
Preferably, the resultant moment of the unmanned aerial vehicle is composed of a torque generated by a propeller and a torque generated by four grid control surfaces; the torque produced by the four grid control surfaces is expressed as:
has the advantages that: when the grid rudder is used by the unmanned aerial vehicle, the influence of crosswind on the machine body can be greatly reduced due to the horizontal installation mode of the grid rudder, and the robustness of the unmanned aerial vehicle is enhanced; in a windless environment, due to the fairing effect of the grid on the airflow and the characteristics of the grid rudder, the control performance of the unmanned aerial vehicle is linear, and the control performance of the unmanned aerial vehicle is greatly improved; and the control of the grid rudder of the micro unmanned aerial vehicle greatly improves the control characteristic of the grid rudder applied to the micro unmanned aerial vehicle, and effectively improves the flight characteristic of the micro unmanned aerial vehicle. Compared with the prior art, the method can enhance the robustness of the unmanned aerial vehicle, effectively reduce the influence of crosswind on the unmanned aerial vehicle, has higher reliability, and improves the control characteristic of the unmanned aerial vehicle in a windless environment.
Drawings
Fig. 1 is a schematic diagram of a micro unmanned aerial vehicle using a grid rudder according to an embodiment of the present invention.
Fig. 2 is a top view of the mounting of the bottom grid rudder of the unmanned aerial vehicle housing in an embodiment of the invention.
Fig. 3 is a schematic diagram of grid-rudder meshing in numerical simulation according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of air domain meshing in numerical simulation according to an embodiment of the present invention.
Fig. 5 is a schematic spatial diagram of the model integral grid division in the numerical simulation according to the embodiment of the present invention.
FIG. 6 is a graph showing simulation curves of the forces generated by the control surfaces of the grids at different tilt angles according to the embodiment of the present invention.
Fig. 7 is a flow chart of pitch control using grid rudders in an embodiment of the present invention.
Fig. 8 is a flowchart of roll control using grid rudders in an embodiment of the present invention.
Fig. 9 is a comparison graph of the magnitude of the acting force generated by the control surface in the windless environment in the embodiment of the invention.
FIG. 10 is a comparison of the yaw angle produced by a standard crosswind fuselage in an embodiment of the invention.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and examples.
Considering that the flat rudder is not linear in control characteristic, the flat rudder can generate large force for the unmanned aerial vehicle when the action of the flat rudder is small in amplitude, and the control performance is good, but when the action amplitude of the flat rudder is large, the control performance is obviously reduced, and the control characteristic presents a nonlinear characteristic. The grid rudder is applied to the control of the micro unmanned aerial vehicle, so that the influence of crosswind on the unmanned aerial vehicle can be effectively reduced in a windy environment, the robustness of the unmanned aerial vehicle is improved, the control characteristic of the unmanned aerial vehicle is improved in a windless environment, and the grid rudder is a breakthrough leap in comparison with the control performance of a flat rudder. In view of the above, the embodiment of the present invention provides a micro unmanned aerial vehicle using grid rudders, where the unmanned aerial vehicle uses a cylindrical housing, four grid control surfaces are uniformly distributed at the bottom of the cylindrical housing in a horizontal installation manner, and the symmetric centers of the four grid control surfaces and the center of gravity of the unmanned aerial vehicle are on the same vertical line; a propeller of the unmanned aerial vehicle is arranged above the top of the cylindrical unmanned aerial vehicle shell; the deflection angle of the grid control surface and the acting force of the propeller wake of the unmanned aerial vehicle on the control surface are in a linear relation, the front and back motion of the unmanned aerial vehicle can be better controlled by adjusting the deflection angles of the left and right grid control surfaces, and the steering motion of the unmanned aerial vehicle is controlled by adjusting the deflection angles of the front and back grid control surfaces.
As shown in fig. 1 and 2, for a specific model of the unmanned aerial vehicle adopted in the embodiment of the present invention, coaxial double propellers and four grid control surfaces are adopted, and the model mainly includes coaxial propellers 1 and 2, a transmission rod 8, an unmanned aerial vehicle housing 9 and four grid control surfaces at the bottom 13 of the unmanned aerial vehicle housing. The motor 3, the automatic pilot system 5, the battery 7 and four steering engines 14 are installed in the unmanned aerial vehicle shell 10, and the three fixing plates 4, 6 and 15 are used for fixing the motor 3, the automatic pilot system 5, the battery 7 and the four steering engines 14. The coaxial propellers 1 and 2 are arranged at the upper end of the transmission rod 8, and the lower end of the transmission rod 8 is connected with the output shaft of the motor 3. The first pair of grid control surfaces 11 and the second pair of grid control surfaces 12 are mounted on the outer wall of the unmanned aerial vehicle shell 9 below the third fixing plate 15 and are respectively controlled by corresponding steering engines 14. The grid rudder is horizontally installed, so that the influence of crosswind on the airplane body can be effectively reduced. The grid rudder structure can adopt a honeycomb type with inclined walls and a frame forming an angle of 45 degrees so as to enhance the structural strength of the grid rudder structure. The weight of the unmanned aerial vehicle is between 600g and 700 g. The self-rotating torque generated by the single propeller can be overcome by adopting a coaxial double-propeller structure.
In order to research the control characteristics of the grid rudder on the aircraft and the control algorithm of the accurate PID, the output characteristics of the grid rudder are firstly researched correspondingly, so that the control strategy and the control algorithm for the micro aircraft can be made according to the output characteristics of the grid rudder, and the corresponding aircraft control algorithm can be made only if the output characteristics of the grid rudder are clear. Therefore, the Fluent is a numerical method for effectively researching the fluid mechanics under the complex flowing flow field, can give out the overall aerodynamic parameters and local flow field details, provides a basis for further structure optimization design, and is also suitable for the grid rudder.
The grid rudder adopts a honeycomb structure design and consists of a plurality of fins which are arranged at certain intervals and are crossed mutually. On the generation of the grids, the grids of the grid rudders are arranged in a staggered mode, so that the difficulty of butt joint with the machine body grids is greatly increased. In the embodiment, a structured scheme is adopted, in order to calculate the acting force of the grid rudder under the action of the washing air flow under the hovering of the coaxial unmanned aerial vehicle, the grid rudder is placed in a closed cylindrical space when a calculation model is established, then corresponding boundary conditions and incoming flow conditions are set in Fluent software, in order to be closer to the stress condition of the control surface under the actual condition, the closed cylindrical space is used as an air domain during simulation, the height of the closed cylindrical space is 15-20 times of the thickness of the control surface, the diameter length of the cross section is 3-4 times of the length of the control surface, and the simulation calculation result is closer to the result under the real environment.
After the simulation model is built, the model is subjected to mesh division, the size of the mesh in the mesh division needs to be selected by fully considering the size of the simulation model, and the quality of the divided mesh needs not to be lost on the basis that the model can be fully divided into the meshes, for example, fig. 3 is the mesh divided by a grid rudder, fig. 4 is the mesh divided by an air domain, and fig. 5 is a space schematic diagram of the whole divided mesh of the calculation model.
After the grid division is finished, setting corresponding constraint conditions, wherein the main parameters comprise media types, unit area conditions, boundary conditions, grid interfaces and initialization, after all the constraint conditions are set, setting and calculating iteration steps to solve, the optimal selection of the iteration steps in different models is different, and the judgment standard is that the iteration presents a trend of converging to a certain stable state.
After the operation is finished, the final grid rudder aerodynamic force is calculated, and the acting force of the propeller downwash airflow on the multiple surfaces is calculated in the Table Viewer of the result model.
The grid rudder model is simulated under the condition that the power angle is 0-50 degrees respectively to obtain the acting force of the unmanned aerial vehicle downwash airflow on the control surface under different inclination angles, and the simulation data is shown in figure 6.
It can be seen from simulation data that the output characteristic of the acting force generated by the grid rudder under different inclination angles is close to a linear state, and an equal-proportion control effect on the unmanned aerial vehicle is generated along with the change of the angle, for the control of the unmanned aerial vehicle, the linear control characteristic is the optimal control characteristic in order to keep the stable state of the unmanned aerial vehicle and complete actions such as pitching and rolling, and the like, and the control performance of the algorithm under the control characteristic can reach the optimal state, so that the grid rudder has an excellent control effect on the miniature unmanned aerial vehicle. Therefore, the linear PID controller of the unmanned aerial vehicle can be designed from the output characteristic angle of grid rudder linearity.
For clarity of explanation of the grid rudder control strategy, the relevant coordinate system, aircraft dynamics and kinematics equations, and already the relevant forces, are first introduced.
1. Definition of coordinate system
The ground inertial coordinate system is selected as a reference standard, and the machine body inertial coordinate system and the machine body fixed connection coordinate system are matched with the ground inertial coordinate system.
Ground inertial coordinate system FeThe origin of the point is fixedly connected with the takeoff position of the unmanned aerial vehicle, and a unit vector i on an X axis under the coordinate systemeUnit vector j on north and Y-axisePointing to the east, unit vector k on the Z axisePointing to the geocentric; body inertial frame FvUnit vector i on X axis under inertial coordinate system of machine bodyvUnit vector j on north and Y-axisvPointing to the east, unit vector k on the Z axisvPointing to the geocentric; fixed coordinate system F of bodybThe origin of coordinates is located at the center of mass of the unmanned aerial vehicle, and the lower X-axis of the coordinate system is singleBit vector ibUnit vector j perpendicular to longitudinal axis of body, pointing forward, and Y-axisbPerpendicular to the longitudinal axis of the unmanned aerial vehicle, pointing to the right side of the unmanned aerial vehicle, and forming a unit vector k on the Z axisbPointing downwards along the longitudinal axis of the machine body.
After the reference frames are determined, the attitude of the aircraft may be determined based on the transitions between the respective reference frames. Hereinafter, the inertial coordinate system is referred to as a machine body inertial coordinate system, and the machine body coordinate system is referred to as a machine body fixed connection coordinate system.
In an inertial frame fixedly connected to the aircraft, the X-axis of the frame points north, the Y-axis points east, and the Z-axis points ground. The most basic method for representing the relationship between the inertial coordinate system and the body coordinate system is to use a rotation matrix
Rotation matrix
Is a 3x3 matrix, multiplied by which the vector rotated to the representation in the current coordinate system is obtained:
euler angles are the most common method for representing the attitude of an aircraft, and represent the attitude of the aircraft as a sequence of three consecutive rotations: (1) inertial frame FvAround kvRotation psi to Fv1In a coordinate system; (2) fv1Coordinate system around jv1Rotation of theta to Fv2In a coordinate system; (3) fv2Coordinate system around iv2Rotate phi to the body coordinate system Fb(ii) a Where θ is the pitch angle, φ is the roll angle, ψ is the yaw angle.
This process is represented by a rotation matrix as:
wherein the content of the first and second substances,
is to represent the conversion process from the inertial system to the body system, the subscript of R represents the coordinate system being rotated, the superscript of R represents the coordinate system to be rotated into, these three rotation matrices can be combined into a matrix from FvTo FbThe rotation matrix of (a):
2. aircraft kinetic equation
In an inertial coordinate system, the mass center motion equation of the aircraft under the action of the resultant external force is as follows:
setting force
Can be decomposed into
The centroid kinetic equation is expressed as
Under the body coordinate system, the rigid body rotation dynamic equation of the aircraft is given by a Newton Euler equation:
in the formula (I), the compound is shown in the specification,
is the moment of momentum of the unmanned aerial vehicle,
the aircraft is subjected to external torque.
Moment of momentum
Under the coordinate system of the machine body
Wherein J is the rotational inertia of the unmanned aerial vehicle,
therefore, it is
Then under the body coordinate system, the rotational dynamics equation can be written as follows:
setting torque
The three components under the machine system are [ LmN]TThen there is
3. Kinematic equation of aircraft
The kinematic equations of the aircraft do not involve forces and moments, and the aircraft is regarded as a whole in relation to the spatial position in which it is located. Considering the rotation motion of the aircraft around the mass center, the relationship between the attitude angular rate of the aircraft and 3 angular velocity components under the coordinate axis of the body is
When the speed of the aircraft in each axis direction under the coordinate axis of the airframe is converted into the speed under the inertial coordinate system of the ground, the three-dimensional space position of the aircraft can be expressed by the following formula
4. Unmanned aerial vehicle resultant force and resultant moment analysis
Analysis is carried out under the organism coordinate system, and the power that this embodiment unmanned aerial vehicle receives and moment mainly come from three aspects, screw pulling force, control surface control power and gravity, the resultant force and the formula of resultant force moment as follows:
in the formula (I), the compound is shown in the specification,
for the tension generated by the propeller, i ═ 1,2 represents an upper propeller and a lower propeller;
the subscript j represents the number of the control surface;
for the torque (N · m) generated by the propeller,
the aerodynamic moment applied to the control surface.
The tensile force vector that coaxial two oar unmanned aerial vehicle's upper and lower screw produced is as follows:
the pull force provided by the propeller is related to the motor speed and is a function of the square of the motor speed
In the formula, cTIn order to be the coefficient of tension,
is the corresponding motor speed.
The results of the simulation analysis in the front and the real flight test verification in the back show that the results of the simulation and the experimental verification are basically consistent, which shows that the linear relation fitted by the simulation result can basically reflect the functional relation between the aerodynamic force generated by the grid control surface and the deflection angle of the control surface, therefore, under the condition of not considering the influence of airspeed on the control surface (because the flight speed of the unmanned aerial vehicle is low, the influence of airspeed on the control surface can be ignored, and only the influence of propeller washing flow on the control surface is considered), the influence of the propeller washing flow on the control surface mainly lies in the force along the X axis of the machine body and the force along the Y axis of the machine body, and can be clearly obtained by numerical simulation results under the same condition of the grid control surface in the front, under the experimental condition, the linear numerical relationship between the aerodynamic force generated by the grid control surface and the deflection angle of the grid control surface is as follows:
the force along the X axis of the fuselage is provided by the first and second grid control surfaces:
Fareo,1＝Fareo,2＝δ×γl (19)
the force along the Y axis of the fuselage is provided by the third and fourth grid control surfaces:
Fareo,3＝Fareo,4＝δ×γr (20)
in the formula, Fareo,1、Fareo,2、Fareo,3、Fareo,4The aerodynamic force generated by the first, second, third and fourth grid control surfaces (acting force generated by the unmanned aerial vehicle) is respectively in the unit of N (the unit of the simulation result is g); gamma raylIs the included angle between the first and second grid control surfaces and the horizontal plane, gammarThe included angle between the third grid control surface and the horizontal plane and the included angle between the fourth grid control surface and the horizontal plane are included; delta is a linear coefficient of the grid control surface simulated by Fluent under corresponding conditions, a numerical curve obtained by the simulation example can be seen, and the value of delta is 3 multiplied by 10-3(since the unit of the simulation result is g, and the equations (19) and (20) use N, it is necessary to add 10-3) (ii) a The coefficients of equations (19) and (20) are obtained by numerical simulation.
The control force vector generated by the four control surfaces is
The gravity vector is expressed as:
in the formula, m is the unmanned aerial vehicle mass, and g is acceleration of gravity.
The torque generated by the upper and lower propellers can be expressed as
In the formula, Mprop,iAs a function of the square of the motor speed,
cMis the relevant tension coefficient.
According to the method for analyzing the aerodynamic force value generated by the grid control surface, the output characteristic of the grid control surface is linear, and the action force of the aerodynamic force of the grid control surface on the unmanned aerial vehicle can linearly express the action force of the grid control surface through a direct proportional function, so that when the torque action generated by the control surface under the action of the propeller is analyzed, only the moment arm needs to be added under the action formula of the grid control surface, and then the resultant force of two pairs of control surfaces is obtained. Because unmanned aerial vehicle flying speed is lower, the influence of airspeed to the control plane can be ignored, only considers the influence of screw washing flow to the control plane. The aerodynamic moment generated by the propeller wake pair control surface in a machine body coordinate system around the X axis and the Y axis is respectively:
in the formula, CldrAnd CmdeFor corresponding dimensionless aerodynamic coefficients, LlThe length of the force arm from the first grid control surface and the second grid control surface to the axis of the unmanned aerial vehicle, LrIs the third and the fourthThe length of the force arm from the grid control surface to the axis of the unmanned aerial vehicle.
It is possible to obtain,
so far, the mathematical model of the unmanned aerial vehicle is obtained, and the control algorithm of the unmanned aerial vehicle can be related based on the mathematical model.
Therefore, the grid rudder output characteristic is a linear characteristic, so that the attitude of the unmanned aerial vehicle can be linearly corrected according to the error generated by the unmanned aerial vehicle when a PID control algorithm is designed, and the grid rudder output characteristic specifically comprises a PID pitch controller and a PID roll controller.
The pitching control mainly controls the forward and backward movement state of the unmanned aerial vehicle, and the pitching power of the unmanned aerial vehicle comes from the grid control surface, so the deflection included angle between the grid control surface and the horizontal plane becomes a reference input of the action of the unmanned aerial vehicle, and the output characteristic of the grid control surface is a linear characteristic, so the forward and backward movement speed of the unmanned aerial vehicle and the deflection angle of the grid control surface present a linear relation. When the output signal (real flight path) of the unmanned aerial vehicle has an error with (reference input) a preset flight path, an error signal is generated, the signal is processed by the controller to become an input signal of the actuator, the input signal is superior to the linear relation reason of the grid control surface input and output, the input signal (namely the steering engine input signal) of the actuator and the error signal are in a linear relation, and the actuator is controlled to adjust a control object (the attitude and the speed of the unmanned aerial vehicle) until the desired value is reached.
The control method comprises the following steps: when a reference pitch angle given by an inertial measurement unit IMU is received, calculating the resultant moment of the unmanned aerial vehicle according to the kinetic equation and the kinematic equation of the aircraft represented by the formulas (13) and (14), further determining the aerodynamic moment generated by propeller wake flow to the first pair of grid control surfaces according to the formulas (23) and (25), and determining the reference deflection angle of the first pair of grid control surfaces according to the linear relation between the grid control surface deflection angle represented by the formula (24) and the aerodynamic moment; and calculating a PWM value according to the reference deflection angle, outputting a PWM signal to a steering engine of the first pair of grid control surfaces, finishing the deflection of the first pair of grid control surfaces and realizing the front-back motion of the unmanned aerial vehicle. The entire pitch control flow is shown in fig. 7.
Based on the same principle, roll control is: when a reference roll angle given by an inertial measurement unit IMU is received, calculating the resultant moment of the unmanned aerial vehicle according to the dynamic equation and the kinematic equation of the aircraft represented by the formulas (13) and (14), further determining the aerodynamic moment generated by the propeller wake flow to the second pair of grid control surfaces according to the formulas (23) and (25), and determining the reference deflection angle of the second pair of grid control surfaces according to the linear relation between the grid control surface deflection angle represented by the formula (24) and the aerodynamic moment; and calculating a PWM value according to the reference deflection angle, outputting a PWM signal to a steering engine of the second pair of grid control surfaces, finishing the deflection of the second pair of grid control surfaces and realizing the steering motion of the unmanned aerial vehicle. The entire roll control flow is shown in fig. 8.
The effects of the present invention are verified and explained below in connection with real flight testing. The flight test uses a microminiature coaxial double-oar unmanned aerial vehicle as an experimental carrier, tests the control performance of the grid rudder and compares the control performance with a conventional flat plate rudder. The grid rudder of the invention is applied to a microminiature aircraft schematically shown in figure 1, and the installation plan view of the grid rudder at the tail of the aircraft is shown in figure 2.
In the flight test process, the type of the bottom control surface is only changed in the contrast test, namely the four grid control surfaces in the figure 2 are changed into the flat control surfaces, other conditions are completely the same, the surface areas of the grid control surfaces and the flat control surfaces are the same, and test data are measured in the first experiment and the second experiment when the coaxial unmanned aerial vehicle hovers.
For a micro unmanned aerial vehicle, the size of a blade, the endurance time and the rudder effect of the unmanned aerial vehicle are in a mutually contradictory relationship: when the unmanned aerial vehicle uses the blades with larger size, larger lift force can be provided for the unmanned aerial vehicle, which is beneficial to the unmanned aerial vehicle, but the cruising ability of the unmanned aerial vehicle can be reduced while the size of the blades is increased, the rotating speed of the large blades can be correspondingly reduced, and the reduction of the rotating speed causes the reduction of the rudder effect, which is harmful to the unmanned aerial vehicle; when the paddle with smaller size is used for the unmanned aerial vehicle, the cruising ability of the unmanned aerial vehicle can be improved, and the rudder effect is correspondingBut the tension of the drone itself will be affected, which is not good for the drone, and therefore a balancing point among them needs to be found. The numerical relationship between blade size and rudder effect is approximately a parabolic relationship of a quadratic function lambda ═ a χ2. The method is characterized in that the method comprises the following steps of obtaining a grid control surface, obtaining a coefficient of a quadratic function relation, obtaining x, and obtaining the control surface of the grid control surface.
Through a large number of experiments, the following optimal experimental balance parameters are obtained as experimental process parameters:
1. unmanned aerial vehicle parameters: weight: 540 g; the down-wash airflow velocity of the coaxial double-paddle unmanned aerial vehicle during suspension: 13 m/s; distance from lower oar to control surface: 21 cm; blade size: a pair of 8 cun.
2. Grid rudder basic parameters: area of horizontal plane: 60cm2(ii) a Length: 100 mm; width: 60 mm; thickness of rudder: 10 mm; individual grid size: 10mm × 10 mm; grid arrangement mode: and the honeycomb type arrangement is inclined by 45 degrees.
3. Basic parameters of the flat rudder: area of vertical surface: 60cm2(ii) a Length: 100 mm; width: 60 mm.
Experiment one: deflection force generated by control surface inclination angle to unmanned aerial vehicle in windless environment
Table 1 magnitude of acting force of control surface inclination angle to unmanned aerial vehicle in windless environment
The meanings of the parameters in table 1:
angle: because the grid rudder surface is horizontally installed, the deflection angle of the grid rudder is the size of the included angle between the rudder surface and the horizontal plane; the flat control surface is vertically arranged, and the flat control surface is an included angle between the control surface and a vertical plane;
rudder type: the parameters of the grid rudder and the plate rudder used in the flight test are shown in the basic parameters of the experimental process.
Test data: the deflection force of a single control surface to the unmanned aerial vehicle under a certain inclination angle is in unit g.
The data in the table are plotted by a curve, as shown in FIG. 9. As can be seen from fig. 9: in a windless environment, under the same area and the same condition, when the deflection angle of the flat rudder is smaller, the rudder effect is very high, the control action on the unmanned aerial vehicle is very strong, a very large acting force can be generated at a very small angle, and when the deflection angle is larger, the change of the generated acting force is very small, and at the moment, the control action on the unmanned aerial vehicle is very weak; the output of the grid rudder is close to the linear characteristic, the equal-proportion control effect on the unmanned aerial vehicle is generated along with the change of the angle, the linear characteristic is the optimal control characteristic for the control of the unmanned aerial vehicle, under the control effect, the designed PID control algorithm displays higher superior performance on the control effect of the unmanned aerial vehicle, and the grid rudder and the corresponding control algorithm have better control effect.
Experiment two: deflection angle generated by fuselage under standard crosswind environment
TABLE 2 deflection angle size of fuselage generation under standard crosswind
The meaning of the parameters in the table:
wind speed: the second experiment is carried out in a standard crosswind environment, wherein the wind speed refers to the standard wind speed for generating force on the side body of the unmanned aerial vehicle;
rudder type: parameters of the grid rudder and the flat plate rudder used in the flight test are shown as basic parameters in the experiment process, and the parameters in the experiment I are completely the same;
test data: the size of the deflection angle generated by the unmanned aerial vehicle body at the corresponding side wind speed refers to the included angle between the central axis of the unmanned aerial vehicle and the vertical direction.
The data in the table are plotted by a curve, as shown in FIG. 10. Through fig. 10, it can be seen that in a standard crosswind environment, under the same area and the same condition, the grid rudder has stronger resistance to crosswind than a flat plate rudder, crosswind with the same speed, and an unmanned aerial vehicle provided with the grid rudder has less influence on the fuselage due to crosswind, and the unmanned aerial vehicle has smaller deflection angle, so that the robustness of a PID control algorithm designed based on the grid rudder on the control of the unmanned aerial vehicle is verified, and the grid rudder and a corresponding control algorithm thereof have better control effect.
Experiments show that the grid rudder scheme more suitable for micro unmanned aerial vehicle control is provided, the grid rudder has better control characteristics in a windless environment, the grid rudder can better resist the influence of crosswind in a crosswind environment, the performance of the unmanned aerial vehicle is greatly improved, and the grid rudder is superior to the conventional flat rudder surface.
Claims (10)
1. The microminiature unmanned aerial vehicle using the grid rudder is characterized in that the unmanned aerial vehicle adopts a cylindrical shell, four grid rudder surfaces are uniformly distributed at the bottom of the cylindrical unmanned aerial vehicle shell in a horizontal installation mode, and the symmetric centers of the four grid rudder surfaces and the gravity center of the unmanned aerial vehicle are on the same vertical line; a propeller of the unmanned aerial vehicle is arranged above the top of the cylindrical unmanned aerial vehicle shell; the first and second grid control surfaces positioned at the left and right sides of the unmanned aerial vehicle are marked as a first pair of grid control surfaces, and the third and fourth grid control surfaces positioned at the front and the rear sides of the unmanned aerial vehicle are marked as a second pair of grid control surfaces; the deflection angle of the grid control surface and the acting force of the propeller wake of the unmanned aerial vehicle on the control surface are in a linear relation; the first pair of grid control surfaces is used for controlling the front and back movement of the unmanned aerial vehicle, and the second pair of grid control surfaces is used for controlling the steering movement of the unmanned aerial vehicle.
2. The micro unmanned aerial vehicle using grid rudders as claimed in claim 1, wherein the grid rudders are honeycomb grid rudders having a structure in which inclined walls and a frame form an angle of 45 °.
3. The miniature drone with grid rudder of claim 1, wherein the propellers of the drone are coaxial double propellers, the length of the propeller blades is greater than the length of the grid rudder surface.
4. The micro unmanned aerial vehicle using a grid rudder of claim 1, wherein the unmanned aerial vehicle has a weight of between 600g and 700 g.
5. The method for controlling the microminiature unmanned aerial vehicle by using the grid rudder is characterized in that the method realizes the front-back movement and the steering movement of the unmanned aerial vehicle by controlling the deflection angles of four grid rudder surfaces arranged at the bottom of the unmanned aerial vehicle; the four grid control surfaces are uniformly distributed at the bottom of the cylindrical unmanned aerial vehicle shell in a horizontal installation mode, and the symmetric centers of the four grid control surfaces and the gravity center of the unmanned aerial vehicle are on the same vertical line; a propeller of the unmanned aerial vehicle is arranged above the top of the cylindrical unmanned aerial vehicle shell; the first and second grid control surfaces positioned at the left and right sides of the unmanned aerial vehicle are marked as a first pair of grid control surfaces, and the third and fourth grid control surfaces positioned at the front and the rear sides of the unmanned aerial vehicle are marked as a second pair of grid control surfaces; the method comprises the following steps:
when a reference pitch angle given by an inertial measurement unit IMU is received, calculating the resultant moment of the unmanned aerial vehicle according to a dynamic equation and a kinematic equation of the aircraft, further determining the aerodynamic moment generated by the propeller wake flow on the first pair of grid control surfaces, and determining the reference deflection angle of the first pair of grid control surfaces according to the linear relation between the grid control surface deflection angle and the aerodynamic moment; calculating a PWM value according to the reference deflection angle, outputting a PWM signal to a steering engine of the first pair of grid control surfaces, completing the deflection of the first pair of grid control surfaces, and realizing the front-back motion of the unmanned aerial vehicle;
when a reference roll angle given by an inertial measurement unit IMU is received, calculating the resultant moment of the unmanned aerial vehicle according to a dynamic equation and a kinematic equation of the aircraft, further determining the aerodynamic moment generated by the propeller wake flow on the second pair of grid control surfaces, and determining the reference deflection angle of the second pair of grid control surfaces according to the linear relation between the grid control surface deflection angle and the aerodynamic moment; and calculating a PWM value according to the reference deflection angle, outputting a PWM signal to a steering engine of the second pair of grid control surfaces, finishing the deflection of the second pair of grid control surfaces and realizing the steering motion of the unmanned aerial vehicle.
6. The method as claimed in claim 5, wherein the linear relationship between the grid control surface deflection angle and the aerodynamic moment is obtained by multiplying the linear relationship between the grid control surface deflection angle and the aerodynamic force by the moment arm from the grid control surface to the axis of the UAV; the linear relation between the grid control surface deflection angle and the aerodynamic force is obtained through Fluent numerical simulation.
7. The method as claimed in claim 6, wherein the closed cylindrical space is used as an air space for simulation when performing numerical simulation by Fluent, the height of the closed cylindrical space is 15-20 times of the thickness of the control surface of the grid, and the diameter of the cross section is 3-4 times of the length of the control surface of the grid.
8. The method of controlling a micro unmanned aerial vehicle using a grid rudder as claimed in claim 5, wherein the linear relationship between the grid rudder surface deflection angle and the aerodynamic moment is expressed as:
wherein M isareo,1、Mareo,2、Mareo,3、Mareo,4The magnitude of the moment, gamma, generated by the first, second, third and fourth grid control surfaces respectivelylIs the included angle between the first and second grid control surfaces and the horizontal plane, gammarIs the included angle between the control plane of the third and fourth grids and the horizontal plane, LlThe length of the force arm from the first grid control surface and the second grid control surface to the axis of the unmanned aerial vehicle, LrThe length of the force arm from the third and fourth grid control surfaces to the axis of the unmanned aerial vehicle, CldrAnd CmdeAnd delta is a linear coefficient of the grid control surface simulated by Fluent under corresponding conditions for corresponding dimensionless aerodynamic coefficients.
9. The method of controlling a micro unmanned aerial vehicle using a grid rudder as claimed in claim 5, wherein the dynamic equation of the aircraft is expressed as:
the kinematic equation for an aircraft is expressed as:
wherein, [ L M N]TThree components of resultant moment in the coordinate system of the body, [ p, q, r]TThe angular velocity vector is three components of the body coordinate system, points on the variables represent derivatives, theta is a pitch angle, phi is a roll angle, psi is a yaw angle, and I isxx、Iyy、Izz、Ixz、IzxIs the rotational inertia of the unmanned plane
The respective components of (a); under the organism coordinate system, the origin of coordinates is located the unmanned aerial vehicle barycenter, the directional unmanned aerial vehicle the place ahead of X axle perpendicular to organism axis of ordinates, the directional unmanned aerial vehicle right side of Y axle perpendicular to organism axis of ordinates, and the Z axle points down along the organism axis of ordinates.
10. The method as claimed in claim 5, wherein the resultant torque of the drone is composed of the torque generated by the propeller and the torque generated by the four grid control surfaces; the torque produced by the four grid control surfaces is expressed as:
wherein M isareo,1、Mareo,2、Mareo,3、Mareo,4The magnitudes of the moments generated by the first, second, third and fourth grid control surfaces respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110843597.6A CN113581448A (en) | 2021-07-26 | 2021-07-26 | Microminiature unmanned aerial vehicle using grid rudder and control method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110843597.6A CN113581448A (en) | 2021-07-26 | 2021-07-26 | Microminiature unmanned aerial vehicle using grid rudder and control method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113581448A true CN113581448A (en) | 2021-11-02 |
Family
ID=78249954
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110843597.6A Withdrawn CN113581448A (en) | 2021-07-26 | 2021-07-26 | Microminiature unmanned aerial vehicle using grid rudder and control method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113581448A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114879718A (en) * | 2022-07-12 | 2022-08-09 | 南京理工大学 | Method for controlling an aircraft with a grid rudder |
-
2021
- 2021-07-26 CN CN202110843597.6A patent/CN113581448A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114879718A (en) * | 2022-07-12 | 2022-08-09 | 南京理工大学 | Method for controlling an aircraft with a grid rudder |
| CN114879718B (en) * | 2022-07-12 | 2022-09-13 | 南京理工大学 | Method for controlling an aircraft with a grid rudder |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109614633B (en) | Nonlinear modeling and linearization balancing method for composite rotor craft | |
| US6568634B2 (en) | Wing-drive mechanism and vehicle employing same | |
| Hernandez-Garcia et al. | Transition flight control of a cyclic tiltrotor UAV based on the gain-scheduling strategy | |
| CN109703768B (en) | Soft air refueling docking method based on attitude/trajectory composite control | |
| Wang et al. | Design, implementation and verification of a quadrotor tail-sitter VTOL UAV | |
| Oosedo et al. | Design and simulation of a quad rotor tail-sitter unmanned aerial vehicle | |
| Baris et al. | Wind tunnel testing of static and dynamic aerodynamic characteristics of a quadcopter | |
| Small et al. | Modelling and control of a tilt-wing unmanned aerial vehicle | |
| Ducard et al. | Modeling of an unmanned hybrid aerial vehicle | |
| Chiappinelli et al. | Modeling and control of a passively-coupled tilt-rotor vertical takeoff and landing aircraft | |
| Phan et al. | Attitude control mechanism in an insect-like tailless two-winged flying robot by simultaneous modulation of stroke plane and wing twist | |
| Chao et al. | Mathematical modeling and control of a tiltrotor UAV | |
| CN113581448A (en) | Microminiature unmanned aerial vehicle using grid rudder and control method | |
| CN113200145B (en) | Portable micro coaxial double-propeller unmanned aerial vehicle and control method thereof | |
| Wang et al. | Modeling and hover control of a novel unmanned coaxial rotor/ducted-fan helicopter | |
| Min et al. | Experimental study of a quadrotor cyclocopter | |
| CN115729264A (en) | Flexible self-adaptive winglet-based stability-variable stealth aircraft control method | |
| Barve et al. | Modelling, simulation and altitude-range-analysis of quad-copter uav | |
| Hernández-García et al. | A total energy control system design for the transition phase of a tiltrotor aerial vehicle | |
| CN112506046B (en) | Stability augmentation control method for wingtip hinged combined type flight platform | |
| Lee et al. | Design, modeling and control of t 3-multirotor: a tilting thruster type multirotor | |
| Alam et al. | Robust hover mode control of a tiltrotor using nonlinear control technique | |
| Cheviron et al. | Generic nonlinear model of reduced scale uavs | |
| Malang | Design and control of a vertical takeoff and landing fixed-wing unmanned aerial vehicle | |
| Kiani et al. | A new bio-inspired flying concept: The quad-flapper |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WW01 | Invention patent application withdrawn after publication |
Application publication date: 20211102 |
|
| WW01 | Invention patent application withdrawn after publication |