Water access control method of tandem configuration cross-medium unmanned aerial vehicle based on switching system

Abstract

The invention belongs to the technical field of aircraft control, and particularly relates to a switching system-based tandem configuration cross-medium unmanned aerial vehicle in-water access control method, which comprises the following steps of: 1) respectively establishing dynamic models of a tandem configuration water-air cross-medium unmanned aerial vehicle in different flight stages; 2) aiming at the kinetic model of the water-air cross-medium unmanned aerial vehicle, designing a sliding mode controller of the unmanned aerial vehicle in different flight stages; and step 3) using software to perform a simulation experiment of the water-air cross-medium unmanned aerial vehicle repeatedly crossing the medium. According to the invention, the unmanned aerial vehicles in different flight stages are regarded as different systems, and the controller is independently designed for control. Through simulation experiments, it is shown that the control method can effectively control the position and attitude stability of the unmanned aerial vehicle in the water entering and exiting process, can well cope with external environment interference and has good robustness.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft control, and in particular relates to a method for controlling entry and exit of a tandem-configured cross-medium UAV based on a switching system. Background Art

[0002] Nowadays, the research on unmanned aerial vehicles has made great progress in both structural design and control technology, but its working field is limited to a single medium. The research on amphibious water-air unmanned aerial vehicles (HAUV) is still in its initial development stage. Amphibious water-air unmanned aerial vehicles have the advantages of rapid deployment and high maneuverability of unmanned aerial vehicles (UAVs), fast cruising ability of unmanned surface vessels (USVs) or high concealment of unmanned underwater vehicles (UUVs), so they have broad application prospects in both military and civilian fields. As a new type of aircraft, amphibious water-air unmanned aerial vehicles have air flight segments, underwater navigation segments and medium crossing segments. Their dynamic characteristics are significantly different from those of traditional single-medium aircraft. It is very difficult to make the aircraft have the ability to fly in both water and air environments. Water-air cross-medium UAVs can be divided into bionic cross-medium UAVs, fixed-wing or multi-rotor cross-medium UAVs and multi-modal cross-medium UAVs. The object of the present invention, the tandem twin-rotor water-air cross-medium UAV, is a new multi-modal cross-medium UAV. It is significantly different from the existing water-air cross-medium UAV in terms of configuration and actuator configuration. It has functions such as hovering in the air, vertical take-off and landing, and rapid maneuvering. It also has the advantages of high aerodynamic efficiency, less power required for hovering, and a large allowable range of center of gravity movement. Currently, no one has studied the water entry and exit control method of this model. In terms of control, since the tandem water-air cross-medium UAV uses two different sets of actuators in the air and underwater, and is underdriven when flying in the air, there is a problem that the same controller cannot be used to control the two flight stages of the UAV. Summary of the invention

[0003] The purpose of the present invention is to provide a method for controlling entry and exit of a tandem-configured cross-medium UAV based on a switching system, so as to solve the technical problem that a tandem twin-rotor cross-medium UAV cannot be operated by the same controller in different flight phases.

[0004] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0005] In some embodiments of the present application, a method for controlling water entry and exit of a tandem-configured cross-medium UAV based on a switching system is provided, comprising the following steps:

[0006] Step 1) establishing dynamic models of the tandem-configured water-air cross-medium UAV at different flight stages;

[0007] Step 2) Design a sliding membrane controller for the UAV in different flight phases based on the dynamic model of the water-air cross-medium UAV;

[0008] Step 3) Use software to conduct simulation experiments of the water-air cross-medium UAV repeatedly crossing the medium.

[0009] In some embodiments of the present application, step 1 includes:

[0010] Step 1.1) Build the kinematic model of the drone:

[0011]

[0012]

[0013] Where ξ1=[xyz] T , Respectively represent the position and direction of the drone relative to the inertial coordinate system, V = [uvw] T ,W=[pqr] T They represent the components of the linear velocity and angular velocity of the UAV in the inertial coordinate system in the body coordinate system;

[0014] in, is the rotation matrix from body coordinates to ground coordinates, T is the conversion matrix from angular velocity to Euler angular velocity in body coordinates, and its specific expression is as follows:

[0015]

[0016]

[0017] Where c*, s* represent cos*, sin* respectively;

[0018] Step 1.2) Based on the system parameter matrix, a dynamic model of the cross-medium UAV in the air and underwater flight states is constructed;

[0019]

[0020] In the formula, η=[ξ1 T ξ2 T ] T ,v=[V T W T ] T , is the inertia matrix including the underwater additional mass, is the centripetal force matrix caused by the drone and the additional mass, is the hydraulic and moment damping matrix caused by the first-order and second-order velocities, where v ris the speed of the drone relative to the water flow, and its expression is:

[0021]

[0022] v w is the water flow velocity, are the restoring forces and moments due to gravity and buoyancy, The thrust and torque matrix provided to the propulsion device, is the interference matrix caused by model uncertainty and external disturbances.

[0023] In some embodiments of the present application, designing a sliding membrane controller includes:

[0024] Step 2.1) Design the underwater sliding mold controller:

[0025] Define the sliding surface s as

[0026]

[0027] In the formula is the sliding surface coefficient, is the error between the actual position and attitude of the cross-medium UAV and the expected value, is the error between the actual speed, angular velocity and the expected value;

[0028] in,

[0029]

[0030] Taking the derivative of (7), we get the reaching law :

[0031]

[0032] For the underwater sliding mold controller, we get:

[0033]

[0034] Where u is the output signal of the controller, and u can be obtained by inverse solution through the reaching law;

[0035] Step 2.2) Design the air slide controller:

[0036] The translational dynamic equation in the z direction is:

[0037]

[0038] Design virtual input u z ,

[0039]

[0040] get,

[0041]

[0042] u1 is the control force of the z axis, and u2, u3, and u4 are the control torques of the x, y, and z axes respectively. Since the cross-medium UAV is an underactuated system in the air cruise phase, it is not easy to control the translation of the x, y, and z directions only with u1. Therefore, a virtual control amount u is introduced in the x and y directions. x ,u y , the translational dynamic equations of x and y are as follows:

[0043]

[0044] Let the virtual control quantity u x 、u y for

[0045]

[0046] At this time, feedback linearization can also be performed in the x and y directions. On the basis that u1 is determined by z, u x ,u y Make x, y achieve the control target; according to the cross-medium UAV to achieve aerial trajectory tracking, a fixed reference trajectory (x d ,y d ,z d ,ψ d ), at this time, the expected roll angle and pitch angle φ of the corresponding trajectory tracking are solved by the inverse solution module d ,θ d ,Right now

[0047] φ d =arcsin(u x sinψ d -u y cosψ d )(twenty two);

[0048]

[0049] In order to realize trajectory tracking, the controller is designed according to the given reference trajectory, and sliding mode control is adopted in the three directions of x, y, and z. From equations (10) and (15), we can get

[0050]

[0051] Substituting equation (24) into equations (17) and (20) yields u1, ux, and uy

[0052]

[0053] byu x ,u y Inversely solve the desired roll angle and pitch angle φ d ,θ d ;

[0054] Among them, the three Euler angles are also controlled by the sliding mode controller.

[0055]

[0056] In formula (24-26), λ and ε are the sliding surface coefficient and reaching law coefficient respectively, and the subscript 1 indicates the air controller parameter;

[0057] Step 2.3) Switching rule design

[0058] The cross-medium UAV is regarded as a particle, and the height position z of the UAV is used as the switching variable. When z<0, the UAV is regarded as being in the underwater diving stage, and the underwater sliding mode controller and UUV dynamics model are adopted; when z≥0, the UAV is regarded as being in the air cruising stage, and the air sliding mode controller and UAV dynamics model are adopted.

[0059] In some embodiments of the present application, the reaching law is

[0060]

[0061]

[0062] In the formula is the reaching law coefficient, and the subscript 2 indicates the underwater controller parameter;

[0063] In the actual control process, the use of the sgn function will cause a sudden change in the controller output, which will cause oscillation. The hyperbolic tangent function is used to replace the sgn function.

[0064]

[0065] By changing the coefficient κ, tanh is made to fit the sgn function. The smaller the coefficient κ, the steeper the curve, and the closer tanh is to the sgn function.

[0066] So the reaching law becomes

[0067]

[0068] Combining equations (11) and (15), the expression of the underwater controller output u is:

[0069]

[0070] Compared with the prior art, the beneficial effect of the present invention is that, in view of the water entry and exit control problem of a tandem twin-rotor configuration water-air cross-medium UAV with multiple systems and external uncertain interference, the UAVs in different flight stages are regarded as different systems and are controlled by separate controllers. Through simulation experiments, it is demonstrated that the control method can effectively control the position and attitude stability of the UAV during the water entry and exit process, and can well cope with external environmental interference (water flow disturbance, crosswind interference), and has good robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0072] Figure 1 A schematic diagram of a tandem-configuration water-air cross-medium UAV provided in an embodiment of the present invention;

[0073] Figure 2 A schematic diagram of the overall control frame of the water-air cross-medium UAV provided in an embodiment of the present invention;

[0074] Figure 3 A schematic diagram of a sliding mode control block provided in an embodiment of the present invention;

[0075] Figure 4 A schematic diagram of the inner and outer ring control frame of the water-air cross-medium UAV provided in an embodiment of the present invention;

[0076] Figure 5 A schematic diagram of a position tracking curve of a water-air cross-medium UAV provided in an embodiment of the present invention;

[0077] Figure 6 A schematic diagram of a height error curve provided by an embodiment of the present invention;

[0078] Figure 7 A schematic diagram of a roll angle curve of a cross-medium UAV provided by an embodiment of the present invention;

[0079] Figure 8 A schematic diagram of a pitch angle curve of a cross-medium UAV provided by an embodiment of the present invention;

[0080] Fig. 9 A schematic diagram of a yaw angle curve of a cross-medium UAV provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0081] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0082] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0083] See attached Figure 1-9 As shown, according to some embodiments of the present application, the following steps are included:

[0084] Step 1) establishing dynamic models of the tandem-configured water-air cross-medium UAV at different flight stages;

[0085] Step 2) Design a sliding membrane controller for the UAV in different flight phases based on the dynamic model of the water-air cross-medium UAV;

[0086] Step 3) Use software to conduct simulation experiments of the water-air cross-medium UAV repeatedly crossing the medium.

[0087] In this application, the sliding mode controller, switching rules, actuators, and the dynamic model of the tandem-configured cross-medium UAV are composed of four parts. The expected posture and the actual posture of the UAV are subtracted to obtain an error signal, and the height signal of the UAV is transmitted to the switching rule module to determine the direction of the error signal transmission. The error signal is given to the sliding mode controller to obtain a control signal, which enters the distribution module. The distribution module obtains the rotor speed and rudder angle signals and gives them to the actuator to obtain the control force and control torque, which are finally input into the dynamic model of the cross-medium UAV to calculate the position and attitude of the UAV.

[0088] The specific implementation steps are as follows.

[0089] Step 1) Establish the dynamic model of the tandem-configuration water-air cross-medium UAV

[0090] The research objects of this application are Figure 1 As shown, the kinematic model of the drone is:

[0091]

[0092]

[0093] In the formula Respectively represent the position and direction of the drone relative to the inertial coordinate system, V = [uvw] T ,W=[pqr] T They represent the components of the linear velocity and angular velocity of the UAV in the inertial coordinate system in the body coordinate system. is the rotation matrix from body coordinates to ground coordinates, T is the conversion matrix from angular velocity to Euler angular velocity in body coordinates, and their specific expressions are as follows:

[0094]

[0095]

[0096] Where c*, s* represent cos*, sin* respectively;

[0097] The configuration, propulsion device and force conditions of the cross-medium UAV in different flight stages (air cruising, underwater diving) are different, and its dynamic model is also different. When flying in the air, the cross-medium UAV can be regarded as a helicopter with a tandem twin-rotor configuration. Its position and attitude are controlled by two rotors and two servos, and it is an under-actuated system; when diving underwater, it can be regarded as an unmanned submarine, and its position and attitude are controlled by five underwater thrusters and a tail rudder. For the convenience of writing and analysis, the dynamic model of the cross-medium UAV in two flight states is now written in the following unified form:

[0098]

[0099] In the formula v=[V T W T ] T , is the inertia matrix including the underwater additional mass, is the Coriolis centripetal force (torque) matrix caused by the drone and the additional mass, is the hydraulic and moment damping matrix caused by the first-order and second-order velocities, where v r is the speed of the drone relative to the water flow, and its expression is:

[0100]

[0101] v w is the water flow velocity, are the restoring forces and moments due to gravity and buoyancy, The thrust and torque matrix provided to the propulsion device, is the interference matrix caused by model uncertainty and external disturbances.

[0102] For the dynamic model (5), when i = 1, the UAV is in the air flight stage; when i = 2, the UAV is in the underwater diving stage; when in different flight stages, C i (v),D i (v r ),g i (η), The matrices are not the same, the specific system parameter matrix is:

[0103] 1) Air system parameter matrix

[0104]

[0105] Where m is the mass of the drone, I xx ,I yy ,I zz For drones about x B ,y B ,z B Moment of inertia about the three axes.

[0106]

[0107]

[0108] S2=O 3×3 (A4)

[0109]

[0110] D 1 (v r )=O 6×6 (A6)

[0111]

[0112]

[0113] Where, η f ,η r are the tilt angles of the front and rear rotors of the UAV, Ω f ,Ω r are the rotation speeds of the front and rear rotors of the UAV, c T is the lift coefficient of the rotor.

[0114]

[0115] In the formula, are the disturbance force and disturbance torque respectively.

[0116] 2) Underwater system parameter matrix

[0117]

[0118] In the above formula, the expression of the additional mass (moment of inertia) coefficient is as follows.

[0119] Added mass / moment of inertia coefficient expression

[0120]

[0121] Among them, B is the width of the body, H is the height of the body, L is the length of the body, and K is the corresponding additional mass of the ellipsoid, which can be obtained by looking up the table.

[0122]

[0123]

[0124]

[0125]

[0126]

[0127] In the formula, X u ,X u|u| They represent the linear and quadratic hydrodynamic viscosity coefficients in the x direction, Y v ,Y v|v| The linear and quadratic terms in the y direction are the hydrodynamic viscosity coefficients, Z w ,Z w|w| They represent the linear and quadratic hydrodynamic viscosity coefficients in the z direction, M q ,M w represents the viscosity coefficient of the first-order hydrodynamic moment on the y-axis, M w|w| represents the viscosity coefficient of the quadratic hydrodynamic moment, N r ,N v Represents the first-order hydrodynamic moment viscosity coefficient of the z-axis, N v|v| represents the viscosity coefficient of the quadratic hydrodynamic moment.

[0128]

[0129] In the formula, F B is the buoyancy of the drone in water.

[0130]

[0131] B i =[d i r i ×d i ] T (A18);

[0132] In the formula, the action points of each thruster are

[0133] The thrust direction vectors of each thruster are d1=d2=[0 0 -1] T ,d3=[cosδ e sinδ e 0] T ,d4=d5=[0 0 1] T, so the control force and control torque directly generated by the thruster are:

[0134]

[0135]

[0136] In the formula, are the disturbance force and disturbance torque respectively.

[0137] In addition, in order to simplify the dynamic model of the UAV, the following assumptions are considered:

[0138] Assumption 1: The drone is in the body coordinate system O B Next about (x B ,z B ) plane is inertial and hydrodynamically symmetric.

[0139] Assumption 2: The origin of the body coordinate system is O B It is also the center of gravity of the drone, and the center of buoyancy is z b In z B axis, above the center of gravity.

[0140] Assumption 3: When the cross-medium drone is underwater, the rolling angular velocity is 0, which means

[0141] Assumption 4: Because the UAV's inertia product is much smaller than the main diagonal elements of the inertia matrix, it can be ignored.

[0142] Step 2) Controller Design

[0143] In view of the cross-medium UAV dynamics model and control requirements established above, this application uses a sliding mode control method with strong robustness that can overcome system uncertainty and external disturbances. The control objective to be achieved is to maintain the attitude of the cross-medium UAV stable (i.e., attitude angle θ,ψ→0), so that the drone can achieve vertical takeoff from underwater z=-1m at 0.1m / s to the air z=1m, hover for a period of time, and then return to the origin at the same speed. Next, the controller design and switching rules will be introduced in detail. The control block diagram of the entire control system is as follows Figure 2 shown.

[0144] Step 2.1) Underwater sliding mold controller design

[0145] Define the sliding surface s as

[0146] In the formula is the sliding surface coefficient, which is a positive definite matrix, is the error between the actual position and attitude of the cross-medium UAV and the expected value, is the error between the actual velocity and angular velocity and the expected value.

[0147]

[0148]

[0149] Taking the derivative of (7), we get the reaching law

[0150] For underwater sliding mold controller, there are also:

[0151] Where u is the controller output signal, and u can be obtained by selecting a suitable reaching law. In this application, the reaching law is selected as

[0152]

[0153] In the formula is the reaching law coefficient, and the subscript 2 represents the underwater controller parameter.

[0154] In the actual control process, the use of the sgn function will cause a sudden change in the controller output, which will cause oscillation and have a great impact on the control effect. In order to reduce this effect, the hyperbolic tangent function is used to replace the sgn function.

[0155]

[0156] By changing the coefficient κ, tanh can be made to fit the sgn function more closely. The smaller the coefficient κ, the steeper the curve, and the closer tanh is to the sgn function.

[0157] So the reaching law becomes,

[0158] Combining equations (11) and (15), the expression of the underwater controller output u is:

[0159]

[0160] The control block diagram of the sliding mode controller is as follows: Figure 3 shown.

[0161] Step 2.2) Design of air sliding mode controller

[0162] Because the movement of cross-media drones in the air is strongly coupled, the control system is usually designed based on the idea of ​​inner and outer loop hierarchical design. Among the six state quantities of cross-media drones, the x and y position states are not directly related to the control input. The control input directly acts on the attitude channel, but the change of x and y positions depends on the change of attitude. The attitude quantity can be used as an actuator to achieve the desired state of the position quantity. In terms of structure, the position can be used as the outer loop and the attitude as the inner loop. The inner and outer loop control structure is as follows: Figure 4 shown.

[0163] Figure 4 Where u1 is the control force of the z-axis, which is obtained through feedback linearization.

[0164] The translational dynamic equation in the z direction is:

[0165] Design virtual input u z ,

[0166] So we can get,

[0167] u2, u3, u4 are the control torques of x, y, z axes respectively.

[0168] Since the cross-medium UAV is an underactuated system in the air cruising stage, it is not easy to control the three directions of x, y, and z using only the control quantity u1. Therefore, a virtual control quantity u1 is introduced in the two directions of x and y. x ,u y .

[0169]

[0170] Let the virtual control quantity u x 、u y for

[0171]

[0172] At this time, feedback linearization can also be performed in the x and y directions. Based on the determination of u1 by z, design u x ,u y So that x, y achieve the control target. Generally speaking, cross-medium UAVs can realize aerial trajectory tracking by giving a reference trajectory (x d ,y d ,z d ,ψ d ). At this time, the inverse solution module is used to solve the desired roll angle and pitch angle φ to achieve the corresponding trajectory tracking. d ,θ d ,Right now

[0173] φd =arcsin(u x sinψ d -u y cosψ d ) (twenty two);

[0174]

[0175] To achieve trajectory tracking, we can design a controller by giving a reference trajectory and adopt sliding mode control in the three directions of x, y, and z. From equations (10) and (15), we can get

[0176]

[0177] Substituting equation (24) into equations (17) and (20) yields u1, ux, and uy

[0178]

[0179] byu x ,u y Inversely solve the desired roll angle and pitch angle φ d ,θ d ,The three Euler angles are also controlled using sliding mode controller.

[0180]

[0181] In formula (24-26), λ and ε are the sliding surface coefficient and reaching law coefficient respectively, and the subscript 1 represents the air controller parameter.

[0182] Step 2.3) Switching rule design

[0183] The cross-medium UAV is regarded as a particle, and the height position z of the UAV is used as the switching variable. When z<0, the UAV is regarded as being in the underwater diving stage, and the underwater sliding mode controller and UUV dynamics model are adopted; when z≥0, the UAV is regarded as being in the air cruising stage, and the air sliding mode controller and UAV dynamics model are adopted.

[0184] Step 3) System simulation experiment and analysis

[0185] Matlab / Simulink software was used to conduct a simulation experiment of a water-air cross-medium UAV repeatedly crossing the medium. The UAV took off vertically from underwater at a speed of 0.1m / s to a certain height in the air, then hovered for 10s, and then fell vertically into the water at the same speed. The initial height was z=-1m underwater, the expected height was z=1m in the air, and finally returned to the origin z=-1m.

[0186] Considering that the UAV will be disturbed by the external environment during flight (such as water flow disturbance, crosswind disturbance, etc.), random noise disturbance is applied when the UAV is underwater, and a crosswind disturbance is applied at t = 20s (when the cross-medium UAV is in a hovering state in the air), which is more in line with the actual flight situation. The calculation of the crosswind is related to the wind force level and the wind direction angle α. Each level of wind has a corresponding wind pressure. The specific calculation method is as follows.

[0187] F di =PA i cosσ i ,(i=x,y,z)(27)

[0188] In the formula, F di is the wind disturbance force, P is the wind pressure, A i is the frontal area, cosσ i It is related to the wind direction angle and the drone’s own attitude.

[0189] Let the unit vector of the wind direction angle be Q, and the normal vector of the body coordinate system be B x ,B y ,B z

[0190] Q = [0 - sin α - cos α] T (28)

[0191]

[0192]

[0193] In order to verify the effectiveness and robustness of the control method proposed in this application, we selected

[0194] The most significant impact on the cross-medium UAV is the cross wind perpendicular to the side of the fuselage, that is, α = 90. After repeated experimental tests, the cross-medium UAV can withstand a maximum wind force of level 6, and the corresponding wind pressure is about 119Pa.

[0195] The simulation results are as follows Figure 5-9 shown. Figure 5 Middle d is the expected height. As can be seen from the figure, the drone tracks the expected trajectory well. In the water-air and air-water medium crossing sections, the drone can still maintain stable tracking of the trajectory without obvious position deviation. In addition, at t=20s, the y position shifted by 0.4m. This is because the cross-medium drone was disturbed by the crosswind for 1s, but the drone was able to restore the y position to stability within 3s, and x and z were almost unaffected. Figure 6 The height error curve shows that the maximum height error does not exceed 0.1m, which also shows that the cross-medium UAV tracks the expected height well.

[0196] Figure 7 It is the roll angle curve of the cross-medium UAV. The roll angle changes significantly at t=10s and t=20s. The former is because the cross-medium UAV is in the water-to-air crossing stage, and the latter is because the UAV is disturbed by crosswind. However, the roll angle can recover stability in a very short time and remain near 0. Figure 8 , Fig. 9 are the pitch angle curve and the yaw angle curve, respectively. Figure 8-9 It can be seen that the pitch angle and yaw angle can be basically kept near 0 during the entire process of the cross-medium drone flight. Figure 7-9 It is shown that the cross-medium UAV, under the control of the sliding mode control algorithm based on the switching system proposed in this application, can well cope with the influence of random water flow interference and crosswind interference force, and ensure the stability of the UAV's attitude.

[0197] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0198] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0199] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0200] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0201] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined in this application may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown in this application, but will conform to the widest scope consistent with the principles and novel features disclosed in this application.

Claims

1. A method for controlling water entry and exit of a tandem-configuration cross-medium UAV based on a switching system, characterized in that: The following steps are involved: Step 1) establishing dynamic models of the tandem-configured water-air cross-medium UAV at different flight stages; Step 2) Design a sliding membrane controller for the UAV in different flight phases based on the dynamic model of the water-air cross-medium UAV; Step 3) Use software to conduct simulation experiments of the water-air cross-medium UAV repeatedly crossing the medium.

2. According to claim 1, a method for controlling entry and exit of a tandem-configuration cross-medium UAV based on a switching system, characterized in that: The step 1 includes: Step 1.1) Build the kinematic model of the drone: Where ξ1=[xyz] T , Respectively represent the position and direction of the drone relative to the inertial coordinate system, V = [uvw] T ,W=[pqr] T They represent the components of the linear velocity and angular velocity of the UAV in the inertial coordinate system in the body coordinate system; in, is the rotation matrix from body coordinates to ground coordinates, T is the conversion matrix from angular velocity to Euler angular velocity in body coordinates, and its specific expression is as follows: Where c*, s* represent cos*, sin* respectively; Step 1.2) Based on the system parameter matrix, a dynamic model of the cross-medium UAV in the air and underwater flight states is constructed; In the formula v=[V T W T ] T , is the inertia matrix including the underwater additional mass, is the centripetal force matrix caused by the drone and the additional mass, is the hydraulic and moment damping matrix caused by the first-order and second-order velocities, where v r is the speed of the drone relative to the water flow, and its expression is: v w is the water flow velocity, are the restoring forces and moments due to gravity and buoyancy, The thrust and torque matrix provided to the propulsion device, is the interference matrix caused by model uncertainty and external disturbances. For the dynamic model (5), when i = 1, the UAV is in the air flight stage; when i = 2, the UAV is in the underwater diving stage.

3. The method for controlling water entry and exit of a tandem-configuration cross-medium UAV based on a switching system according to claim 1, characterized in that: The design of the sliding membrane controller includes: Step 2.1) Design the underwater sliding mold controller: Define the sliding surface s as In the formula is the sliding surface coefficient, is the error between the actual position and attitude of the cross-medium UAV and the expected value, is the error between the actual speed, angular velocity and the expected value; Taking the derivative of (7), we get the reaching law For the underwater sliding mold controller, we get: Where u is the output signal of the controller, and u can be obtained by inverse solution through the reaching law; Step 2.2) Design the air slide controller: The translational dynamic equation in the z direction is: Design virtual input u z , get, u1 is the control force of the z-axis, and u2, u3, and u4 are the control torques of the x-, y-, and z-axes respectively; Introduce virtual control quantity u in the x and y directions x ,u y , the x,y translational dynamic equations are as follows: Let the virtual control quantity u x 、u y for At this time, feedback linearization can also be performed in the x and y directions. On the basis that u1 is determined by z, u x ,u y Make x, y achieve the control target; according to the cross-medium UAV to achieve aerial trajectory tracking, a fixed reference trajectory (x d ,y d ,z d ,ψ d ), at this time, the expected roll angle and pitch angle φ of the corresponding trajectory tracking are solved by the inverse solution module d ,θ d ,Right now f d =arcsin(u x sinψ d -u y cosψ d (22); In order to realize trajectory tracking, the controller is designed according to the given reference trajectory, and sliding mode control is adopted in the three directions of x, y, and z. From equations (10) and (15), we can get Substituting equation (24) into equations (17) and (20) yields u1, ux, and uy byu x ,u y Inversely solve the desired roll angle and pitch angle φ d ,θ d ; Among them, the three Euler angles are also controlled by the sliding mode controller. In formula (24-26), λ and ε are the sliding surface coefficient and reaching law coefficient respectively, and the subscript 1 indicates the air controller parameter; Step 2.3) Switching rule design The cross-medium UAV is regarded as a particle, and the height position z of the UAV is used as the switching variable. When z < 0, the UAV is regarded as being in the underwater diving stage, and the underwater sliding mode controller and UUV dynamics model are adopted; when z ≥ 0, the UAV is regarded as being in the air cruising stage, and the air sliding mode controller and UAV dynamics model are adopted.

4. The method for controlling water entry and exit of a tandem-configuration cross-medium UAV based on a switching system according to claim 3, characterized in that: The reaching law is In the formula is the reaching law coefficient, and the subscript 2 indicates the underwater controller parameter; In the actual control process, the use of the sgn function will cause a sudden change in the controller output, which will cause oscillation. The hyperbolic tangent function is used to replace the sgn function. By changing the coefficient κ, tanh is made to fit the sgn function. The smaller the coefficient κ, the steeper the curve, and the closer tanh is to the sgn function. So the reaching law becomes Combining equations (11) and (15), the expression of the underwater controller output u is:

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