A tethered grabber control system and method based on polar coordinates and control weights

Abstract

The present invention discloses a tethered grabber control system and method based on polar coordinates and control weights. The system studies a grabber connected by a tether and having autonomous maneuverability. The method is an approximate control method for a tethered grabber based on fuzzy control, backstepping and sliding mode control. First, the dynamic model of the tethered grabber is represented in polar coordinates, and the attitude and position weights are adjusted using the fuzzy control method to achieve temporal separation of attitude control and position control. Based on the aforementioned system model in polar coordinates, the backstepping method and the sliding mode control method can be used to respectively design controllers so that the grabber, on the one hand, approaches the target with high accuracy along a determined trajectory, and on the other hand, ensures that the disturbance to other state quantities is small and within a controllable range. This method utilizes a control method that combines state representation in polar coordinates with control weights, and can enable the tethered grabber to accurately approach the target to be captured in a uniquely determined state without reconfiguring the actuator.

Description

Technical Field

[0001] The present invention belongs to the field of intelligent autonomous target capture, and in particular relates to a tether capture device control system and method based on polar coordinates and control weights. Background Art

[0002] The combination of drones and grippers offers unique advantages for approaching, capturing, and transporting targets in complex environments. Current grippers primarily consist of rigid robotic arms and tethered grippers. The former lacks autonomous maneuverability and relies entirely on the precise position control of the drone platform for target capture. Furthermore, they lack the ability to capture slow-moving targets. Errors in the drone platform's position control increase the uncertainty and complexity of the task.

[0003] The tethered grabber consists of a freely retractable tether and a grabber. The tether connection point can move forward and backward along the grabber's longitudinal axis. Ducted engines are symmetrically mounted on either side of the grabber, making it a typical underactuated system. Relatively speaking, due to the limitations of the drone's payload capacity, the grabber's total mass must be as small as possible, so it cannot carry too many actuators, which would prevent the roll channel from being directly controlled. When the grabber reaches within a relatively small range of the target, its state must be deterministic. That is, the grabber's own state information must be uniquely determinable when capturing the target, placing higher demands on the control system's control accuracy. When the target moves at low speeds, the grabber must have high tracking accuracy, which places additional demands on the control system. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a tethered grabber control system and method based on polar coordinates and control weights. The attitude control and position control are separated by representing the state of the grabber in polar coordinates. In addition, the attitude weights and position weights are adjusted to achieve the temporal separation of the two, so that the grabber can approach the target in a certain state.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A tethered grabber control method based on polar coordinates and control weights comprises the following steps:

[0007] The desired yaw angle is obtained through the desired yaw angle command regulator, the tracking error is set according to the desired yaw angle, the tracking error is corrected by the attitude weight, and the virtual control amount of the yaw angle is obtained. The control torque of the yaw angle is obtained through the virtual control amount of the yaw angle; the attitude weight is adjusted in combination with the control torque to make the yaw angle of the catcher converge to the desired state;

[0008] The pitch motion is controlled by controlling the forward and backward movement of the tether connection point, thereby controlling the roll motion of the capture device, wherein the virtual control quantity of the roll motion is the desired instruction of the pitch motion angular velocity;

[0009] The polar diameter of the catcher is obtained through the polar coordinate equation, and the horizontal tracking error is established through the polar diameter. The horizontal tracking error is corrected by the position weight. Combined with the sliding mode control method, the center of mass motion control law of the catcher is established to control the horizontal motion of the catcher.

[0010] By introducing height error and combining with sliding mode control method, a flight height control law of the grabber is established to control the flight height of the grabber.

[0011] A further improvement of the present invention is:

[0012] Preferably, the desired yaw angle command regulator is:

[0013] ψ d =-atan2(x Im -x,z Im -z) (6)

[0014] Among them, ψ d is the desired yaw angle, the x Im is the coordinate of the virtual point on the x-axis, the z Im is the coordinate of the virtual point on the z-axis, x is the coordinate of the capture device on the x-axis, and z is the coordinate of the capture device on the z-axis;

[0015] The tracking error e ψ for:

[0016] e ψ =ψ-ψ d (13)

[0017] Where ψ is the yaw angle;

[0018] The tracking error is corrected by the posture weight: e a =K a e ψ ;

[0019] Among them, K a is the posture weight;

[0020] The virtual control value of the yaw angle ψ is:

[0021]

[0022] in, is the differential of the desired yaw angle, is the differential of the posture weight, k ψ is the yaw control parameter;

[0023] The control torque is:

[0024]

[0025] in, is the nonlinear term in the model, is the yaw input coefficient, is the differential of the desired yaw rate, and is the yaw rate control parameter.

[0026] Preferably, the posture weight is obtained by a fuzzy control method, and the original posture weight expression in the fuzzy control method is:

[0027]

[0028] After defuzzifying the original posture weight of formula (9), the posture weight is obtained.

[0029] Preferably, the virtual control instruction for the rolling motion is:

[0030]

[0031] Preferably, the equation for the forward and backward movement distance of the tether connection is:

[0032]

[0033] Among them, k p 、T i and τ are the control parameters of PID respectively.

[0034] Preferably, the polar coordinate equation is:

[0035]

[0036] The tracking error is:

[0037] e ρ =ρ-ρ d

[0038] Among them, ρ d is the expected diameter, ρ d The command regulator is:

[0039]

[0040] The position weight is:

[0041]

[0042] The tracking error of the corrected horizontal plane is:

[0043] e p =K p e ρ .

[0044] Preferably, the position weight is obtained by a fuzzy control method, and the original position weight expression in the fuzzy control method is:

[0045]

[0046] After defuzzifying the original position weight of formula (1), the position weight is obtained.

[0047] Preferably, the center of mass motion control rate is:

[0048]

[0049] Preferably, the flight altitude rate control law is:

[0050]

[0051] A tethered grabber control system based on polar coordinates and control weights, comprising:

[0052] The yaw motion control unit obtains the desired yaw angle through the desired yaw angle command regulator, sets the tracking error based on the desired yaw angle, corrects the tracking error using the attitude weight, obtains the virtual control amount of the yaw angle, and obtains the control torque of the yaw angle based on the virtual control amount of the yaw angle; combines the control torque to adjust the attitude weight so that the yaw angle of the catcher converges to the desired state;

[0053] A roll motion control unit, configured to control the pitch motion by controlling the forward and backward movement of the tether connection point, thereby controlling the roll motion of the capture device, wherein the virtual control amount of the roll motion is the desired instruction of the pitch motion angular velocity;

[0054] The horizontal motion control unit is used to obtain the polar diameter of the catcher through the polar coordinate equation, establish the horizontal plane tracking error based on the polar diameter, correct the horizontal plane tracking error through the position weight, and establish the center of mass motion control rate of the catcher in combination with the sliding mode control method, thereby controlling the horizontal motion of the catcher;

[0055] The flight height control unit is used to introduce height error and, combined with the sliding mode control method, establish the flight height control law of the catcher, thereby controlling the flight height of the catcher.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The present invention discloses a tethered grabber control system and method based on polar coordinates and control weights. The system studies a grabber connected by a tether and having autonomous maneuverability. The method is an approximate control method for a tethered grabber based on fuzzy control, backstepping and sliding mode control. First, the dynamic model of the tethered grabber is represented in polar coordinates, and the attitude and position weights are adjusted using the fuzzy control method to achieve temporal separation of attitude control and position control. Based on the aforementioned system model in polar coordinates, the backstepping method and the sliding mode control method can be used to respectively design controllers so that the grabber, on the one hand, approaches the target with high accuracy along a determined trajectory, and on the other hand, ensures that the disturbance to other state quantities is small and within a controllable range. This method utilizes a control method that combines state representation in polar coordinates with control weights, and can enable the tethered grabber to accurately approach the target to be captured in a uniquely determined state without reconfiguring the actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 is a virtual point schematic diagram;

[0059] Figure 2 It is the control system structure diagram; DETAILED DESCRIPTION

[0060] The present invention is described in further detail below with reference to the accompanying drawings:

[0061] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise expressly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a communication between the internal parts of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0062] The tethered grabber system consists of a flying platform, a grabber and a tether. The tether connection point on the grabber is movable, and together with the engines symmetrically installed on both sides of the tether, it serves as the grabber's actuator. The present invention mainly addresses the motion control problem of the grabber.

[0063] The present invention is a grabber approximation control method based on polar coordinates and control weights. By expressing the movement of the grabber in the horizontal plane in polar coordinates and combining the control weights, the grabber can accurately approximate the target with little impact on other channels, thus overcoming the limitations of existing methods.

[0064] Figure 1 This is a schematic diagram of a virtual point. Using geometric methods to determine the desired yaw angle can easily lead to sudden changes in the value when the gripper reaches a small area near the target. This problem can be effectively addressed by placing virtual points on the gripper-target line and using the information from these virtual points to determine the desired yaw angle.

[0065] Figure 2 The control system structure diagram is shown below. First, the target position information is decomposed into angle and position commands using a control command regulator. The horizontal position command is converted into radial form. The critical error is then scaled using control weights, and the corresponding controllers are used to control the gripper's speed and direction, achieving precise approach to the target.

[0066] The proposed tethered grabber approximation control method based on polar coordinates and control weights mainly consists of the following four steps:

[0067] Step 1: Express the motion of the catcher in the horizontal plane in polar coordinates, keeping the other channels unchanged, and obtain the dynamic equation that meets the control requirements.

[0068] The mass and inertia of the capturer are defined as m and J respectively, the attitude angles are defined as roll angle γ, yaw angle ψ and pitch angle θ respectively, and the angular velocity of each axis is ω x 、ω y and ω z The coordinate rotation order from the inertial system to the current system is 2-3-1, and the target position R is defined as T =[x T y T z T ] T , the real-time position of the capture device is R = [xyz] T At the same time, the distance the tether connection point moves in the longitudinal direction of the capture device is ΔX Q , the tether tension is T, and its components along the coordinate axis are T x ,T y ,T z The total thrust of the ducted engine is always along the longitudinal axis of the catcher and its magnitude is F, and the corresponding torque magnitude is M F .

[0069] This step primarily converts the horizontal motion of the grabber to polar coordinates, while other motions, such as elevation, remain in Cartesian coordinates. The polar diameters of the grabber and target can be directly determined by calculating their respective distances from the origin. Velocity and tether tension require other methods to determine direction.

[0070] In the present invention, by comparing the current moment's polar diameter ρ with the previous moment's polar diameter Get the speed V ρ , tether tension direction T ρ It is obtained by comparing the platform diameter ρ1 and the capture diameter, which can be expressed as follows:

[0071]

[0072]

[0073]

[0074]

[0075] According to the existing dynamic model of the catcher, the horizontal motion can be expressed in polar coordinates as:

[0076]

[0077] where f ρ is a nonlinear term, b ρ is the control output coefficient, and F is the total thrust of the engine. Based on the above formula, a controller can be designed to enable the catcher to complete the approach task.

[0078] Step 2: Use virtual points to design the desired command regulator to obtain the desired yaw angle, desired polar radius command and other desired commands.

[0079] (By setting the virtual point R Im , and on this basis, the following expected command regulator is designed, formula (6) and formula (7), to solve the problem of numerical mutation when solving the expected yaw angle command in real time). From the above, we can know that the target position R T =[x T y T z T ] T and the capture position is R = [xyz] T ,like Figure 1 As shown, select a virtual point R within an appropriate distance on the straight line where it is located Im =[x Im y Im z Im ] T , we can get the desired yaw angle ψ d and the expected radius ρd The command regulator is:

[0080] ψ d =-atan2(x Im -x,z Im -z) (6)

[0081]

[0082] In addition, the desired height instruction y d =y T , the expected roll angle is 0. When the attitude control accuracy is high in the initial stage, the virtual point will not change.

[0083] Step 3: Use fuzzy control method to design position weights to obtain weight values that can make the posture converge quickly and have little impact on other channels.

[0084] Use the above method to get the posture weight K a and position weight K p , thereby achieving temporal separation of attitude control and position control. Since the research subject of this invention is underactuated and it is desired that the attitude of the grabber be determined when it reaches a certain range of the target to be captured, changes in the roll angle caused by yaw angle control errors should be minimized. By using different weights to separate attitude control and position control, when the attitude converges to the neighborhood of the expected value, position control is then performed to allow the grabber to approach the target along a predetermined trajectory.

[0085] Assume that the posture tracking error is e ψ , fuzzify it and design fuzzy sets based on prior knowledge as very small (SS), very small (VS), small (LS), small (S), slightly small (PS), slightly large (PB), large (B), relatively large (LB), very large (VB), and very large (SB). According to actual control requirements, the yaw tracking error e ψ When it is large, a larger posture weight must be used to make it converge quickly to the expected value. Therefore, the following fuzzy rule table is available:

[0086] Table 1 Posture weight fuzzy rule table

[0087] if(if) SS VS LS S PS PB B LB VB SB then SS VS LS S PS PB B LB VB SB

[0088] Get the fuzzy relationship:

[0089] R a ((SS×SS)∪(VS×VS)∪(LS×LS)∪(S×S)∪(PS×PS)∪(PB×PB)∪(B×B)∪(LB×LB)∪(VB×VB)∪(SB×SB) (8)

[0090] In fuzzy decision making, the posture weight is the combination of the error vector and the fuzzy relationship

[0091]

[0092] By defuzzifying it using the average maximum membership method, the attitude control weight K that meets the requirements can be obtained. a .

[0093] Similarly, the position control weight is given by the fuzzy control method. Since the accuracy of the posture control affects the position control to a certain extent, the present invention uses the posture control error as the update information of the position weight, thereby achieving the fundamental requirements of time separation of posture position control and high-precision position control. Based on the prior basis, the posture error and the position weight are fuzzified, and the fuzzy sets are designed as very small (SS), very small (VS), small (LS), small (S), slightly small (PS), slightly large (PB), large (B), large (LB), very large (VB), and very large (SB). Fuzzy rules are specified based on the condition that the position weight must be very small when the posture error is slightly large. The following fuzzy rule table is provided:

[0094] Table 2 Position weight fuzzy rule table

[0095] if(if) SS VS LS S PS PB B LB VB SB then SB VB LB B PB PS S LS VS SS

[0096] Get the fuzzy relationship:

[0097] R p ((SS×SB)∪(VS×VB)∪(LS×LB)∪(S×B)∪(PS×PB)

[0098] ∪(PB×PS)∪(B×S)∪(LB×LS)∪(VB×VS)∪(SB×SS) (10)

[0099] Similarly, in fuzzy decision making, the original position weight is the synthesis of the error vector and the fuzzy relationship:

[0100]

[0101] Similarly, the position control weight K that meets the requirements can be obtained by defuzzifying it p .

[0102] Step 4: Use the aforementioned control method to design a position controller and a posture controller respectively to control the movement direction and speed of the capture device, so that it can track the command signal obtained in step 2 in a certain time sequence under the action of the control weight, and achieve accurate approach to the target to be captured.

[0103] Specifically, based on the dynamic model in step 1 and combined with the attitude weights and position weights in step 3, the tethered grabber control system is designed using the backstepping method and sliding mode control method to track the control instructions given in step 2 and approach the target according to the predetermined trajectory.

[0104] The posture controller in the present invention is divided into two parts (such as Figure 2 ), the yaw motion of the grabber is controlled by the differential ducted motor, and the pitch motion is controlled by the forward and backward movement of the tether connection point. The roll channel has no direct control mechanism, so the coupling of yaw and pitch is used to stabilize the roll channel at the desired value.

[0105] (1) Yaw motion control

[0106] The yaw motion of the tethered grabber is controlled using the classic backstepping method. The yaw motion of the grabber can be described by the following equation:

[0107]

[0108] Among them, f ψ and are the nonlinear terms of yaw channel kinematics and dynamics, b ψ and are their corresponding control input coefficients, u ψ is the virtual control value of yaw angle, M F is the yaw control torque.

[0109] First, for the kinematic subsystem, let the tracking error be:

[0110] e ψ =ψ-ψ d (13)

[0111] The posture tracking error after correction using posture weight is e a =K a e ψ In general, given the error differential:

[0112]

[0113] where k ψ is the control parameter. According to the kinematic subsystem in formula (12), the virtual control quantity can be expressed as

[0114]

[0115] Similarly, define the angular velocity tracking error e ω =ω y -ω yd , and assuming that the angular velocity loop can be tracked well, the virtual control quantity u ψThat is the desired angular velocity ω yd The differential value of the angular velocity tracking error can also be given satisfy:

[0116]

[0117] in and is the yaw rate control parameter. According to the dynamic subsystem of formula (12), the control torque is:

[0118]

[0119] in, is the differential of the desired yaw rate. Under the above control torque, by adjusting the attitude weight K a The yaw angle of the catcher can be quickly converged to the desired state.

[0120] (3) Roll / Pitch motion control (the virtual control quantity for roll is the desired pitch angular velocity command, and the pitch motion is directly controlled by moving the connection point, thereby indirectly controlling roll)

[0121] The roll of a tethered capture device is typically not directly controllable. However, the present invention utilizes the coupling of yaw and pitch motion to reduce the range of variation during disturbances, maintaining the roll angle within a relatively small acceptable range when the disturbance is minimal. Pitch motion is primarily controlled by moving the tether connection point forward and backward. Because the relationship between the tether connection point position and the pitch angle is complex and a straightforward control law cannot be derived directly, PID control is employed.

[0122] like Figure 2 As shown, the desired roll angle instruction γ has been given in the control instruction adjustment d The kinematic equation of the catcher rolling channel is:

[0123]

[0124] If the roll tracking error is assumed to be e γ =γ-γ d , the virtual control instruction of the pitch angular velocity can be obtained as:

[0125]

[0126] in, is the differential of the desired roll angle, k z is the roll control parameter. In particular, in this application, γ d It is always equal to 0. Here, the virtual instruction is considered to be the desired instruction of the pitch angular velocity, that is, the virtual control amount of the roll motion.

[0127] Assume that the pitch angle tracking error The moving distance of the tether connection point can be expressed using PID control as

[0128]

[0129] In the above control law, the PID control parameter k is appropriately adjusted p 、T i and τ can make the pitch angle converge to the desired value and remain stable.

[0130] (3) The position control in the present invention uses the tether retraction and release and the ducted motor to control the height movement of the catcher and its movement in the horizontal plane, respectively. The height movement control is relatively independent. The details are as follows:

[0131] 1) Control of center of mass motion in the horizontal plane (position weights and the center of mass motion equation in the horizontal plane in polar coordinate form are used here)

[0132] From formula (5), we can get the polar diameter of the catcher as ρ, and the polar diameter of the catcher is Integrate to get; ρ is the assumed tracking error e in the horizontal plane ρ =p-ρ d , tracking error e after position weight correction p =K p e ρ The polar coordinate equation (5) of the tethered catcher in the horizontal plane is the center of mass motion equation. Based on the center of mass motion equation, the sliding mode control method is adopted, and the sliding mode surface s is set. ρ :

[0133]

[0134] Among them, λ ρ is the control bandwidth of the horizontal center of mass motion. And, the differential of the given sliding surface satisfies:

[0135]

[0136] where k ρ and ε ρ is the control gain. According to formula (5), the center of mass motion control law can be expressed as:

[0137]

[0138] At this point, the total thrust F of the bypass engine is obtained, combined with the torque M of the above formula (17): F , we can find the thrust of each engine, specifically:

[0139]

[0140]

[0141] Among them, h d Indicates the distance between the ducted engine mounting wheel and the longitudinal axis of the catcher.

[0142] 2) Flight altitude control

[0143] The height of the grabber is controlled by tether retraction and extension. The system's dynamic model does not explicitly include the center of mass motion in the height direction related to tether retraction and extension. Therefore, a more intuitive dynamic equation is derived from the tether constraint equation. To improve control accuracy, the integral of the tracking error is introduced as a new error variable, and a corresponding height controller is designed.

[0144] The dynamic equation in the height direction can be expressed as follows

[0145]

[0146] Among them, f y is the nonlinear term of the height channel in the model, b y is the height control input coefficient, and c is the control input.

[0147] Similarly, combined with the expected flight height y d Define the height tracking error e y =yy d , introduce the integral of the error and construct a new error variable To improve the control accuracy,

[0148]

[0149] Among them, ξ y is the height error integral coefficient. Based on the above tracking error, the sliding surface is defined as

[0150]

[0151] In the above formula, λ y is the height control bandwidth. Obtain the differential expression of the sliding surface so that it satisfies

[0152]

[0153] Among them, k y and ε y is the altitude control parameter. Based on the above derivation, the flight altitude control law can be obtained as follows:

[0154]

[0155] By retracting and releasing the tether according to the above control law, the height of the catcher can be changed according to the desired trajectory, and the steady-state performance is improved by introducing the integral of the error.

[0156] The key to the implementation of the method of the present invention is that, without reconfiguring the actuator, the motion state of the grabber is represented in polar coordinates, and the attitude control weight and position control weight are combined, and controllers are designed based on fuzzy control, backstepping method and sliding mode control methods respectively, so that the tethered grabber can accurately approach the target to be captured on the one hand, and on the other hand, ensure that the other states are within the controllable range.

[0157] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0158] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A tethered grabber control method based on polar coordinates and control weights, characterized in that: The following steps are involved: The desired yaw angle is obtained through the desired yaw angle command regulator, the tracking error is set according to the desired yaw angle, the tracking error is corrected by the attitude weight, and the virtual control amount of the yaw angle is obtained. The control torque of the yaw angle is obtained through the virtual control amount of the yaw angle; the attitude weight is adjusted in combination with the control torque to make the yaw angle of the catcher converge to the desired state; The posture weight is obtained by a fuzzy control method, and the original posture weight expression in the fuzzy control method is: (9) in, is the yaw tracking error; After defuzzifying the original posture weight of formula (9), the posture weight is obtained; The position weight is obtained by a fuzzy control method, in which the original position weight expression is: (11) After defuzzifying the original position weight of formula (1), the position weight is obtained; The pitch motion is controlled by controlling the forward and backward movement of the tether connection point, thereby controlling the roll motion of the capture device, wherein the virtual control quantity of the roll motion is the desired instruction of the pitch motion angular velocity; The polar diameter of the catcher is obtained through the polar coordinate equation, and the horizontal tracking error is established through the polar diameter. The horizontal tracking error is corrected by the position weight. Combined with the sliding mode control method, the center of mass motion control law of the catcher is established to control the horizontal motion of the catcher. By introducing the height error and combining it with the sliding mode control method, the flight height control law of the catcher is established to control the flight height of the catcher. The virtual control instruction of the rolling motion is: (19)； in, denote the roll angle and pitch angle respectively, is the desired roll command, is the roll tracking error; The center of mass motion control rate is: (23)； The flight altitude rate control law is: (30)。 2. The tethered grabber control method based on polar coordinates and control weights according to claim 1, characterized in that: The desired yaw angle command regulator is: (6) in, is the desired yaw angle, is the coordinate of the virtual point on the x-axis, is the coordinate of the virtual point on the z-axis, x is the coordinate of the capture device on the x-axis, and z is the coordinate of the capture device on the z-axis; The tracking error for: （13） in, is the yaw angle; Correcting the tracking error by posture weight is: ; in, is the posture weight; The yaw angle The virtual control quantity is: (15) in, is the differential of the desired yaw angle, is the differential of the posture weight, is the yaw control parameter; The control torque is: (17) in, is the nonlinear term in the model, is the yaw input coefficient, is the differential of the desired yaw rate, and is the yaw rate control parameter.

3. The tethered grabber control method based on polar coordinates and control weights according to claim 1, characterized in that: The equation for the forward and backward movement distance of the tether connection is: (20) in, 、 and are the control parameters of PID respectively.

4. The tethered grabber control method based on polar coordinates and control weights according to claim 1, characterized in that: The polar coordinate equation is: (5) The tracking error is: in, is the expected polar diameter, The command regulator is: (7) The position weight is: The tracking error of the corrected horizontal plane is: 。 5. A tethered capture control system based on polar coordinates and control weights for implementing the control method of claim 1, characterized in that: include: The yaw motion control unit obtains the desired yaw angle through the desired yaw angle command regulator, sets the tracking error based on the desired yaw angle, corrects the tracking error using the attitude weight, obtains the virtual control amount of the yaw angle, and obtains the control torque of the yaw angle based on the virtual control amount of the yaw angle; combines the control torque to adjust the attitude weight so that the yaw angle of the catcher converges to the desired state; A roll motion control unit, configured to control the pitch motion by controlling the forward and backward movement of the tether connection point, thereby controlling the roll motion of the capture device, wherein the virtual control amount of the roll motion is the desired instruction of the pitch motion angular velocity; The horizontal motion control unit is used to obtain the polar diameter of the catcher through the polar coordinate equation, establish the horizontal plane tracking error based on the polar diameter, correct the horizontal plane tracking error through the position weight, and establish the center of mass motion control rate of the catcher in combination with the sliding mode control method, thereby controlling the horizontal motion of the catcher; The flight height control unit is used to introduce height error and, combined with the sliding mode control method, establish the flight height control law of the catcher, thereby controlling the flight height of the catcher.

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