Arm type recovery system for recovering fixed-wing unmanned aerial vehicle and control method

Abstract

The invention relates to an arm type recovery system for recovering a fixed-wing unmanned aerial vehicle and a control method, the arm type recovery system comprises two mechanical arm units, each mechanical arm unit comprises a large arm, a small arm, a base and a reel assembly, a support is arranged on each base, the lower end of each large arm is rotatably installed on the corresponding support, a large arm driving device is arranged on each support, and the reel assemblies are arranged on the small arms. The upper end of the large arm is connected with the small arm through a connecting joint, the connecting joint comprises a connecting seat and a small arm driving device, the connecting seat comprises a concave part on the upper side and a shaft sleeve on the lower side, the shaft sleeve is connected with the small arm driving device, and the upper end of the small arm is rotationally installed in the concave part; the connecting base and the small arm driving device are both installed on the large arm upper connecting base, reel assemblies are arranged in the base, and the two ends of the blocking cable sequentially penetrate through the small arm and the large arm of the mechanical arm unit on the corresponding side, then stretch into the base on the corresponding side and are wound on the corresponding reel assemblies. Accurate control can be achieved so that the arresting cable can be accurately hooked to the unmanned aerial vehicle hook.

Description

Technical Field

[0001] The invention relates to the field of fixed-wing unmanned aerial vehicle recovery, and in particular to an arm-type recovery system and a control method for recovering a fixed-wing unmanned aerial vehicle. Background Art

[0002] Fixed-wing UAVs play an extremely important role in environmental monitoring, surveying and mapping, patrol and rescue in the ocean or on land. In application scenarios such as environmental monitoring, other tools are limited by movement speed and maneuverability, so it is difficult to conduct large-scale environmental coverage monitoring in a short period of time. Fixed-wing UAVs have the advantages of fast speed, strong maneuverability, large activity range and long battery life. They can quickly conduct large-scale environmental coverage monitoring, especially when multiple UAVs work together at the same time, which can greatly improve the operating efficiency. In addition, the technology of fixed-wing UAVs is relatively mature and the development cost is low.

[0003] At present, the common methods of fixed-wing UAV recovery include net recovery and parachute recovery. Net recovery refers to a recovery method in which the UAV uses a specific guidance method to slow down and lower its altitude, and finally crashes into the arresting net. The net recovery system is generally composed of an arresting net, an energy-absorbing buffer device, and a terminal guidance device. The key to this recovery method is to accurately guide the UAV to fly into the arresting net and gently absorb the kinetic energy of the UAV, so as to achieve safe recovery. However, for special environments such as the sea, due to the harsh environment at sea (wind, waves, deck swaying, etc.), coupled with the small area of ​​the arresting net, its terminal guidance accuracy is often difficult to guarantee. Parachute recovery is to use a parachute to recover the UAV. This recovery method is simple to operate. The entire process from the flight state to the safe recovery of the UAV is completed automatically, and the requirements for the operator are relatively low. However, parachute recovery also has many disadvantages. For example, the built-in parachute will occupy the space and load in the fuselage. The UAV descends quickly during landing. The fuselage will be subjected to a strong impact at the moment of landing, which is easy to cause different degrees of damage. In addition, for special environments such as the sea, due to the influence of the environment, the landing point of the UAV is difficult to accurately control. There is also a recovery method in the prior art that uses arresting cables and drone hooks to slow down the drone on a deck in a limited space until it stops. However, since the arresting cable is smaller in size than existing arresting nets and other methods, it is more difficult to guide. Summary of the invention

[0004] The object of the present invention is to provide an arm-type recovery system and a control method for recovering a fixed-wing UAV, which can achieve precise control so that the arresting cable is accurately hooked to the UAV.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The invention discloses an arm-type recovery system for recovering a fixed-wing unmanned aerial vehicle, comprising two mechanical arm units, and the mechanical arm unit comprises a main arm, a forearm, a base and a reel assembly, wherein a support is provided on the base, and the lower end of the main arm is rotatably mounted on the support, a main arm driving device is provided on the support, and the main arm is driven to rotate by the main arm driving device, the upper end of the main arm is connected to the forearm through a connecting joint, and the connecting joint comprises a connecting seat and a forearm driving device, wherein the connecting seat comprises a concave portion on the upper side and a shaft sleeve on the lower side, and the shaft sleeve is connected to the forearm driving device, the upper end of the forearm is rotatably mounted in the concave portion, the upper end of the main arm is provided with a main arm upper connecting seat, and the connecting seat and the forearm driving device are both mounted on the main arm upper connecting seat, a reel assembly is provided in the base, and two ends of an arresting cable respectively pass through the forearm and the main arm of the mechanical arm unit on the corresponding side in sequence, and then extend into the base on the corresponding side and are wound around the corresponding reel assembly.

[0007] The boom body of the boom includes boom side plates on both sides, and the arresting cable passes between the boom side plates on both sides. A boom lower connecting seat is provided at the lower end of the boom body, and the end portions of the boom lower connecting seat are respectively rotatably installed on the supports on the corresponding sides, and one end of the boom lower connecting seat is fixedly connected to the boom driving device.

[0008] A first arm wire hole is provided at the lower end of the arm body of the arm, a base wire opening is provided on the base, and a support wire ring is provided on the support close to the base wire opening. After the arresting rope is output from the first arm wire hole, it first passes through the support wire ring and then enters the base through the base wire opening and is wound around the reel assembly.

[0009] The upper end of the forearm body of the forearm is provided with a forearm rotating shaft, the upper ends of the side walls on both sides of the concave part are provided with lower covers, and an upper cover is fixedly provided above the lower cover, and the forearm rotating shaft is rotatably arranged in a circular hole formed between the upper cover and the lower cover on the corresponding side.

[0010] The forearm body of the forearm is a circular tube structure, and the lower end of the forearm body is provided with a lower end cap with a first forearm wire passing hole, the arresting cable enters the forearm body through the first forearm wire passing hole of the lower end cap, the upper end of the forearm body is provided with a second forearm wire passing hole, and the upper connecting seat of the boom is provided with a first wire ring, a second wire ring and a second boom wire passing hole. After the arresting cable is output from the second forearm wire passing hole, it passes through the second wire ring and the first wire ring in sequence and then enters the boom body of the boom through the second boom wire passing hole.

[0011] The forearm driving device includes a forearm motor and a harmonic reducer connected in sequence, wherein the output end of the harmonic reducer is fixedly connected to the lower end of a connecting shaft, the upper end of the connecting shaft is inserted into the sleeve on the lower side of the connecting seat, and the upper end of the connecting shaft and the sleeve are key-connected.

[0012] The base includes a box body, and two supports are arranged on the top plate of the box body, the top plate is provided with a base wire hole, the reel assembly is arranged inside the box body, and the lower end of the box body is provided with a support foot; the reel assembly includes a reel drive device and a reel frame, wherein baffles are provided on both sides of the reel frame, a reel shaft is provided inside the reel frame, and the reel shaft is driven to rotate by the reel drive device, the arresting rope is wound around the reel shaft and the winding position is limited by the baffles on both sides of the reel frame, and guide plates are provided on both sides above the reel frame along the tangential direction.

[0013] A control method of the arm-type recovery system for recovering a fixed-wing UAV comprises the following steps:

[0014] Step 1: Determine the motion control algorithm. After the drone enters the recovery orbit, there is always relative motion between the drone and the end of the robotic arm unit. This relative motion is the disturbance generated by the outside world. Based on the prediction algorithm of fast Fourier transform and adaptive fuzzy-PID control, the above disturbance is first subjected to fast Fourier transform:

[0015] f Obs，i =f FFT，i (1);

[0016]

[0017]

[0018] In the above formulas (1) to (3), f Obs,i represents the predicted frequency of the end of the robot unit, represents the predicted phase angle at the end of the robot unit, a Obs,i represents the predicted amplitude at the end of the robot unit, f FFT，i It means that the peak detector identifies the frequency corresponding to the i-th harmonic in the main N harmonic functions, represents the estimated value after Fourier transformation at time t, represents the estimated value of the first-order derivative after Fourier transform at time t, and T represents the time value within a period of ΔT;

[0019] Step 2: Superimpose the estimated harmonics of different frequencies to predict T pre The expected motion signal after time, that is, the expected position W at the end of the robot unit pre (t):

[0020]

[0021] In the above formula (7), the compensation value ρ(t) is a constant at time t:

[0022]

[0023] in, represents the estimated value of the odd wave at time T;

[0024] Step 3: Construct the fuzzy control algorithm at the end of the robot arm unit:

[0025] U(t)=K P E(t)+K I ∑E(t)+K D EC(t) (8);

[0026] In the above formula (8), U(t) represents the output value of the PID regulator, E(t) represents the system input deviation, EC(t) represents the change in the system input deviation, and the parameter K P , K I , K D represents the fuzzy control parameters, where:

[0027] E(t)=H(t)-W pre (t) (9);

[0028] In the above formula (9), H(t) represents the current position of the end of the robot arm unit, W pre (t) is obtained by the above formula (7);

[0029] Apply fuzzy theory to establish parameter K P , K I , K D The relationship between the absolute value of the input deviation |E| and the absolute value change rate of the deviation |EC| is:

[0030]

[0031]

[0032]

[0033] In the above formulas (10) to (12), μ i represents the membership function, K Pi , K Ii , K Di Indicates the weighted value under different states;

[0034] Step 4: Determine the expected movement angle A of the two robot arm units (1) 1 , S 1 and the desired movement angle A of the forearms (2) of the two robot units 2 , S 2 :

[0035] A 1 =B1 =sec(U(t) / 2800);

[0036] A 2 =B 2 = -2 × sec (U (t) / 2800);

[0037] Where U(t) is obtained by the above formula (8).

[0038] In step 1, the relative motion between the drone and the end of the robotic arm unit is represented by a superposition of a set of simple harmonic waves with different periods:

[0039]

[0040] In the above formula (4), A i represents the amplitude corresponding to the i-th simple harmonic wave, f i represents the frequency corresponding to the i-th simple harmonic wave, represents the phase corresponding to the i-th simple harmonic wave, and ρ(t) represents the initial compensation value of the interference signal. Therefore, in the above equations (1) to (3):

[0041]

[0042]

[0043] In the above formulas (5) to (6), A FFT,i It means that the peak detector identifies the amplitude corresponding to the i-th harmonic in the main N harmonic functions, It means that the peak detector identifies the phase corresponding to the i-th harmonic in the main N harmonic functions.

[0044] In step 3, for the convenience of computer processing and implementation, the absolute value of the input deviation |E|, the absolute value change rate of the deviation |EC| and the output membership function in the above equations (10) to (12) are all linear functions, and |E|, |EC| and PID parameter K are set to P , K I , K D The fuzzy control domain is described by four different fuzzy linguistic variables: zero (symbol Z), small (symbol S), medium (symbol M), and large (symbol B). Then, the membership functions of the fuzzy linguistic variables corresponding to the domain involving the fuzzy deviation |E| and the membership functions of the fuzzy linguistic variables corresponding to the domain involving the fuzzy deviation |EC| are obtained respectively. In addition, the above four descriptions of Z, S, M, and B are |E|, |EC|, and K P , K I , K D The four membership components of

[0045] In order to improve the system response speed and system adjustment accuracy, the following fuzzy control rules are designed:

[0046] Table 1 K P Fuzzy Control Rules

[0047]

[0048] Table 2K I Fuzzy Control Rules

[0049]

[0050] Table 3K D Fuzzy Control Rules

[0051]

[0052] After obtaining the values ​​of |E| and |EC|, the membership component and component weight value of |E| are obtained according to the membership function of the fuzzy linguistic variable corresponding to the domain involving the fuzzy deviation |E|, and the membership component and component weight value of |EC| are obtained according to the membership function of the fuzzy linguistic variable corresponding to the domain involving the fuzzy deviation |EC|. Then, the membership component and component weight value of |E| and the membership component and component weight value of |EC| are substituted into the above Table 1 to obtain K. P Substitute the membership components into Table 2 above to obtain K I Substitute the membership components into Table 3 above to obtain K D The membership component of K is finally determined according to the parameter value table obtained from the experiment. P , K D , K I value.

[0053] The advantages and positive effects of the present invention are:

[0054] 1. The present invention utilizes a boom driving device to drive the boom to rotate, utilizes a forearm to drive the forearm to rotate, and at the same time the reel assembly cooperates to release or retract the arresting cable to ensure that the arresting cable is stretched. The present invention can achieve precise control of the position of the end of the mechanical arm unit by precisely controlling the rotation angle of the boom and the rotation angle of the forearm, thereby ensuring that the arresting cable is accurately hooked to the drone. In addition, the control method of the present invention takes into account the influence of various environmental factors at sea, represents the relative motion between the drone and the end of the mechanical arm unit as a superposition of a group of simple harmonic waves with different periods, and adopts a prediction algorithm based on fast Fourier transform and adaptive fuzzy-PID control to obtain accurate boom rotation angle and forearm rotation angle, thereby greatly reducing the influence of various environmental factors at sea.

[0055] 2. The upper arm and the lower arm of the present invention are connected by a connecting joint, and the upper side of the connecting seat in the connecting joint is a concave portion, and the lower side is a shaft sleeve. The end of the forearm is rotatably connected to the concave portion, and the shaft sleeve is fixedly connected to the output shaft of the forearm driving device and realizes rotational drive, thereby realizing the rotation of the connecting seat and the forearm. At the same time, the forearm can realize adaptive rotation relative to the concave portion of the connecting seat, thereby supporting flexible arrestment and height compensation, so as to better cooperate with the autonomous and safe recovery operation of the UAV under complex sea conditions.

[0056] 3. The present invention has designed a unique arresting cable routing structure, in which both ends of the arresting cable pass through the small arm and the big arm on the corresponding side respectively and then extend to the base on the corresponding side and are wound around the corresponding reel assembly, so that when the mechanical arm unit moves, it will not affect the arresting cable tension and the routing path. At the same time, the upper connecting seat of the big arm of the big arm is provided with a first wire ring and a second wire ring for the arresting cable to pass through, and the support on the side of the base near the base wire opening is provided with a support wire ring for the arresting cable to pass through, so as to ensure that the arresting cable will not be knotted, stuck, broken, worn, etc. when it is retracted and released. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a schematic diagram of the structure of the system of the present invention,

[0058] Figure 2 for Figure 1 Schematic diagram of the structure of the middle and large arm.

[0059] Figure 3 for Figure 2 Another structural diagram of the middle and upper arm.

[0060] Figure 4 for Figure 1 Schematic diagram of the structure of the middle and small arms.

[0061] Figure 5 for Figure 4 A in the enlarged view,

[0062] Figure 6 for Figure 5 A cross-sectional view of the connecting joint.

[0063] Figure 7 for Figure 1 Schematic diagram of the structure of the middle base.

[0064] Figure 8 This is a schematic diagram of the arresting cable routing direction of the system of the present invention.

[0065] Fig. 9 for Figure 8 Schematic diagram of the structure of the middle reel assembly,

[0066] Fig.10 for Fig. 9 Cross-sectional view of the middle reel assembly,

[0067] Fig.11 for Figure 8 An enlarged view of the connection between the middle and lower arms and the upper arms.

[0068] Fig.12 for Figure 8 An enlarged view of the connection between the middle arm and the base.

[0069] Fig.13 is the membership function of the fuzzy linguistic variable corresponding to the domain of the fuzzy deviation |E| in the control method of the present invention,

[0070] Fig.14 It is the membership function of the fuzzy linguistic variable corresponding to the domain involving the fuzzy deviation |EC| in the control method of the present invention.

[0071] Among them, 1 is a big arm, 101 is a big arm arm body, 1011 is an arm body side plate, 102 is a big arm upper connecting seat, 1021 is a first wire ring, 1022 is a second wire ring, 103 is a big arm lower connecting seat, 104 is a big arm driving device, 2 is a small arm, 201 is a lower end cap, 202 is a small arm arm body, 2021 is a small arm shaft, 203 is a connecting joint, 2031 is an upper cover, 2032 is a small arm motor, 2033 is a connecting seat, 20331 is a lower cover , 20332 is the bushing, 2034 is the connecting shaft, 2035 is the harmonic reducer, 204 is the upper end cap, 3 is the arresting rope, 4 is the base, 401 is the support, 4011 is the support wire ring, 402 is the box body, 4021 is the top plate, 4022 is the support foot, 4023 is the base wire hole, 5 is the reel assembly, 501 is the driving motor, 502 is the reducer, 503 is the reel frame, 5031 is the guide plate, 5032 is the reel shaft, and 5033 is the bearing. DETAILED DESCRIPTION

[0072] The present invention will be further described below in conjunction with the accompanying drawings.

[0073] like Figures 1 to 14 As shown, the present invention includes two mechanical arm units, and the mechanical arm units include a large arm 1, a small arm 2, a base 4 and a reel assembly 5, wherein two supports 401 are provided on the base 4, and the lower end of the large arm 1 is rotatably installed between the two supports 401, and a large arm driving device 104 is provided on either side of the support 401, and the large arm 1 is driven to rotate by the large arm driving device 104, and the upper end of the large arm 1 is connected to the small arm 2 through a connecting joint 203, and as shown Figures 5-6As shown, the connecting joint 203 includes a connecting seat 2033 and a small arm driving device, wherein the connecting seat 2033 includes a concave portion on the upper side and a shaft sleeve 20332 on the lower side, and the shaft sleeve 20332 is connected to the small arm driving device through a connecting shaft 2034, and the upper end of the small arm 2 is rotatably installed in the concave portion, as shown in FIG. Figure 2 As shown, the upper end of the upper arm 1 is provided with an upper arm connecting seat 102, and the connecting seat 2033 and the small arm driving device are both installed on the upper arm connecting seat 102. Figure 8 As shown, a reel assembly 5 is provided in the base 4, and the two ends of the arresting cable 3 respectively pass through the small arm 2 and the big arm 1 of the corresponding side mechanical arm unit in sequence, and then extend into the base 4 of the corresponding side and are wound on the corresponding reel assembly 5. When the present invention is working, the big arm 1 is driven to rotate by the big arm driving device 104, and the small arm 2 is driven to rotate by the small arm driving device on the one hand, and on the other hand, because the small arm 2 is rotatably installed in the concave part of the connecting seat 2033, under the pulling action of the arresting cable 3, the small arm 2 can realize adaptive rotation.

[0074] like Figures 2-3 As shown, in this embodiment, the boom body 101 of the boom 1 includes arm body side plates 1011 on both sides, and the arresting rope 3 passes between the arm body side plates 1011 on both sides. A boom lower connecting seat 103 is provided at the lower end of the boom body 101, and the two ends of the boom lower connecting seat 103 are respectively supported and rotated on the support 401 on the corresponding side through bearings or other suitable rotating support elements. One end of the boom lower connecting seat 103 is fixedly connected to the boom driving device 104, and the boom driving device 104 drives the boom lower connecting seat 103 to rotate, thereby driving the entire boom 1 to rotate. In this embodiment, the boom driving device 104 is a reduction servo motor. In addition, a first boom wire passing hole is provided at the lower end of the boom body 101, as shown in FIG. Figure 7 As shown, the base 4 is provided with a base through line 4023, and as shown Fig.12 As shown, a support wire ring 4011 is provided on the support 401 near the base through wire 4023. Figure 8 As shown, after the arresting cable 3 is output from the first arm wire hole, it first passes through the support wire ring 4011, then enters the base 4 through the base wire 4023 and is wound around the reel assembly 5.

[0075] like Figures 4 to 6As shown, in this embodiment, the forearm body 202 of the forearm 2 is a circular tube structure, and the lower end of the forearm body 202 is provided with a lower end cap 201 with a first forearm wire-through hole, the arresting cable 3 enters the forearm body 202 through the first forearm wire-through hole of the lower end cap 201, and the upper end of the forearm body 202 is rotatably connected with the concave portion on the upper side of the connecting seat 2033, wherein the upper end of the forearm body 202 is provided with a forearm rotating shaft 2021, the upper ends of the side walls on both sides of the concave portion are provided with lower covers 20331, and an upper cover 2031 is fixed above the lower cover 20331, the forearm rotating shaft 2021 is rotatably supported by a bearing and arranged in a circular hole formed between the upper cover 2031 and the lower cover 20331 on the corresponding side, and the upper end of the forearm body 202 is provided with a second forearm wire-through hole, as shown Fig.11 As shown, the upper connecting seat 102 of the upper arm 1 is provided with a first wire ring 1021 and a second wire ring 1022, and the upper connecting seat 102 is provided with a second wire hole for the upper arm. Figure 8 As shown, the arresting cable 3 is output from the second small arm through-hole, passes through the second wire ring 1022 and the first wire ring 1021 in sequence, and then enters the big arm body 101 through the second big arm through-hole. Figures 5-6 As shown, in this embodiment, the forearm driving device includes a forearm motor 2032 and a harmonic reducer 2035 connected in sequence, wherein the output end of the harmonic reducer 2035 is fixedly connected to the lower end of the connecting shaft 2034, the upper end of the connecting shaft 2034 is inserted into the sleeve 20332 on the lower side of the connecting seat 2033, and the upper end of the connecting shaft 2034 and the sleeve 20332 are key-connected to achieve synchronous rotation. The harmonic reducer 2035 is a well-known technology in the art and is a commercially available product.

[0076] like Figure 7 As shown, in this embodiment, the base 4 includes a box body 402, and two supports 401 are arranged on the top plate 4021 of the box body 402, the top plate 4021 is provided with a base wire hole 4023, the reel assembly 5 is arranged inside the box body 402, and the lower end of the box body 402 is provided with a support foot 4022.

[0077] like Figures 9-10As shown, in this embodiment, the reel assembly 5 includes a reel drive device and a reel frame 503, wherein baffles are provided on both sides of the reel frame 503, a reel shaft 5032 is provided inside the reel frame 503, and the reel shaft 5032 is driven to rotate by the reel drive device, and the arresting cable 3 is wound around the reel shaft 5032 and the winding position is limited by the baffles on both sides of the reel frame 503. In this embodiment, the two ends of the reel shaft 5032 are supported by bearings 5033 to realize rotation, and guide plates 5031 are provided on both sides of the upper side of the reel frame 503 along the tangential direction, and the arresting cable 3 enters the reel frame 503 along the inner side of the guide plates 5031. In this embodiment, the reel drive device includes a driving motor 501 and a reducer 502 connected in sequence, and the output shaft of the reducer 502 is coaxially fixedly connected to the reel shaft 5032.

[0078] The working principle of the present invention is:

[0079] When the present invention works, Figure 8 As shown, the arresting cable 3 is straightened by the ends of the mechanical arm units on both sides, wherein the two ends of the arresting cable 3 respectively pass through the forearm 2 and the upper arm 1 of the corresponding side mechanical arm unit in turn, and then extend into the base 4 on the corresponding side and are wound on the corresponding reel assembly 5, the upper arm 1 is driven to rotate by the upper arm driving device 104, and the lower arm 2 is driven to rotate by the lower arm driving device, thereby realizing the end position adjustment of the two mechanical arm units, and at the same time, the reel assembly 5 cooperates to retract or release the arresting cable 3 to ensure its straightening, and when the fixed-wing UAV is recovered, the ends of the two mechanical arm units adjust their positions in real time according to the disturbance situation, this disturbance refers to the fact that after the UAV enters the recovery orbit, due to the influence of factors such as wind and waves, there is always relative movement between the UAV and the ends of the mechanical arm units of the system of the present invention, and this relative movement refers to the disturbance generated by the outside world, but the present invention ensures that the arresting cable 3 can be hooked and aligned with the UAV through the coordinated action of the above-mentioned upper arm 1, lower arm 2 and other mechanisms, thereby realizing the smooth recovery of the UAV.

[0080] The control method of the system of the present invention is as follows:

[0081] Step 1: Determine the motion control algorithm. The present invention adopts a prediction algorithm based on fast Fourier transform and adaptive fuzzy-PID control. First, the above disturbance is subjected to fast Fourier transform:

[0082] f Obs,i =f FFT,i (1);

[0083]

[0084]

[0085] In the above formulas (1) to (3), fObs，i represents the predicted frequency of the end of the robot unit, represents the predicted phase angle at the end of the robot unit, a Obs,i represents the predicted amplitude at the end of the robot unit, f FFT,i It means that the peak detector identifies the frequency corresponding to the i-th harmonic in the main N harmonic functions, represents the estimated value after Fourier transformation at time t, It represents the estimated value of the first-order derivative after Fourier transform at time t, and T represents the time value within a period of ΔT.

[0086] The relative motion between the drone and the end of the mechanical arm unit of the present invention can be expressed as a superposition of a set of simple harmonic waves (also called modes) with different periods, specifically:

[0087]

[0088] In the above formula (4), A i represents the amplitude corresponding to the i-th simple harmonic wave, f i represents the frequency corresponding to the i-th simple harmonic wave, represents the phase corresponding to the i-th simple harmonic wave, and ρ(t) represents the initial compensation value of the interference signal. Therefore, in the above equations (2) to (3):

[0089]

[0090]

[0091] In the above formulas (5) to (6), f FFT,i It also means that the peak detector identifies the frequency corresponding to the i-th harmonic in the main N harmonic functions, A FFT,i It means that the peak detector identifies the amplitude corresponding to the i-th harmonic in the main N harmonic functions, It means that the peak detector identifies the phase corresponding to the i-th harmonic in the main N harmonic functions.

[0092] The peak value detector is a well-known technology in the art, which is a software detector on data and detects the maximum and minimum values ​​of data through real-time data recording.

[0093] Step 2: Superimpose the estimated harmonics of different frequencies to predict T pre The expected motion signal after time, that is, the expected position W at the end of the robot unit pre (t):

[0094]

[0095] In the above formula (7), the compensation value ρ(t) is a constant at time t, which can be calculated as:

[0096]

[0097] In the above formula, Represents the estimated value of the odd wave at time T.

[0098] Step 3: Construct the fuzzy control algorithm of the end-point of the robot arm unit and construct the following control algorithm:

[0099] U(t)=K P E(t)+K I ∑E(t)+K D EC(t) (8);

[0100] In the above formula (8), U(t) represents the output value of the PID regulator, E(t) represents the system input deviation, EC(t) represents the change in the system input deviation, that is, the difference between two E(t), and the parameter K P , K I , K D represents the fuzzy control parameters, where:

[0101] E(t)=H(t)-W pre (t) (9);

[0102] In the above formula (9), H(t) represents the current position of the end of the robot arm unit, W pre (t) is the desired position of the end of the robot arm unit obtained in step 2 above;

[0103] Apply fuzzy theory to establish parameter K P , K I , K D The relationship between the absolute value of the input deviation |E| and the absolute value change rate of the deviation |EC| is:

[0104]

[0105]

[0106]

[0107] In the above formulas (10) to (12), μ i represents the membership function, K Pi , K Ii , K Di Indicates the weighted value under different states;

[0108] For the convenience of computer processing and implementation, the absolute value of the input deviation |E|, the absolute value change rate of the deviation |EC| and the output membership function in the above equations (10) to (12) are all linear functions. The |E|, |EC| and PID parameter K are set toP , K I , K D The fuzzy control domain is described by four different fuzzy linguistic variables: zero (symbol Z), small (symbol S), medium (symbol M), and large (symbol B), and then the membership functions of the fuzzy linguistic variables corresponding to the domain involving the fuzzy deviation |E| are obtained respectively, as shown in Fig.13 As shown in , and the membership function of the fuzzy linguistic variables corresponding to the domain involving the fuzzy deviation |EC|, as Fig.14 As shown, Fig.13 and Fig.14 The horizontal axis is the input variable, and the vertical axis is its membership weighted value. The above four descriptions of Z, S, M, and B are |E|, |EC|, and K P , K I , K D The four membership components of .

[0109] In order to improve the system response speed and improve the system adjustment accuracy, the fuzzy control rules in Tables 1 to 3 are designed as follows: Table 1K P Fuzzy Control Rules

[0110]

[0111] Table 2K I Fuzzy Control Rules

[0112]

[0113] Table 3K D Fuzzy Control Rules

[0114]

[0115] Table 4

[0116] Z S M B <![CDATA[K P ]]> 0.9 0.6 0.3 0 <![CDATA[K I ]]> 0.7 0.6 0.5 0.4 KD 0.1 0.4 0.8 0.9 ;

[0118] Assuming |E|=0.1, |EC|=2.4, then according to Figures 13-14 It can be calculated that the weighted value of the membership component of |E| is 0.75 for Z, the weighted value of S is 0.25, and the weighted value of M and B are both 0. Similarly, the weighted value of the membership component of |EC| is 1 for M, and the weighted value of the others is 0.

[0119] Substitute the membership degree into Table 1 and calculate K according to the above formula (10): P Weighted value, where |E| is Z with a weight of 0.75, and |EC| is M with a weight of 1, K PContains 0.75 B (the intersection of E's Z column and EC's M row is B, and 0.75×1=0.75, so 0.75 B is obtained). Similarly, when |E| is S with a weight of 0.25 and |EC| is M with a weight of 1, K P Contains 0.25 B (the intersection of E's S column and EC's M row is B, and 0.25×1=0.25, so 0.25 B is obtained), then K P Use B with a weighting coefficient of 1 (0.75+0.25), and then according to K P Use B to check Table 4 (parameter value table obtained from the experiment) to obtain K P is 0; similarly K I is 0.4, K D is 0.9, and then substituted into the above formula (8) to obtain U(t).

[0120] Step 4: Determine the expected movement angle A of the arm 1 of the two robot units 1 , B 1 And the expected movement angle A of the forearm 2 of the two robot arm units 2 , B 2 :

[0121] A 1 =B 1 =sec(U(t) / 2800);

[0122] A 2 =B 2 =-2×sec(U(t) / 2800).

Claims

1. An arm-type recovery system for recovering a fixed-wing UAV, characterized in that: The invention comprises two mechanical arm units, and the mechanical arm units comprise a large arm (1), a small arm (2), a base (4) and a reel assembly (5), wherein a support (401) is provided on the base (4), and the lower end of the large arm (1) is rotatably mounted on the support (401), a large arm driving device (104) is provided on the support (401), and the large arm (1) is driven to rotate by the large arm driving device (104), and the upper end of the large arm (1) is connected to the small arm (2) via a connecting joint (203), and the connecting joint (203) comprises a connecting seat (2033) and the small arm driving device, wherein the connecting seat (2033) comprises a connecting seat (2033) and a small arm driving device, and wherein the connecting seat (2033) comprises a connecting seat (2033) and a small arm driving device. The forearm (2) comprises a concave portion on the upper side and a shaft sleeve (20332) on the lower side, and the shaft sleeve (20332) is connected to the forearm driving device, the upper end of the forearm (2) is rotatably mounted in the concave portion, the upper end of the boom (1) is provided with a boom upper connecting seat (102), and the connecting seat (2033) and the forearm driving device are both installed on the boom upper connecting seat (102), a reel assembly (5) is provided in the base (4), and the two ends of the arresting rope (3) respectively pass through the forearm (2) and the boom (1) of the corresponding side mechanical arm unit in turn, and then extend into the base (4) on the corresponding side and are wound around the corresponding reel assembly (5).

2. The arm-type recovery system for recovering a fixed-wing UAV according to claim 1, characterized in that: The boom body (101) of the boom (1) comprises boom body side plates (1011) on both sides, and the arresting rope (3) passes between the boom body side plates (1011) on both sides. A boom lower connecting seat (103) is provided at the lower end of the boom body (101), and the ends of the boom lower connecting seat (103) are respectively rotatably mounted on the supports (401) on the corresponding sides, and one end of the boom lower connecting seat (103) is fixedly connected to the boom driving device (104).

3. The arm-type recovery system for recovering a fixed-wing UAV according to claim 1, characterized in that: A first arm wire hole is provided at the lower end of the arm body (101) of the arm (1), a base wire opening (4023) is provided on the base (4), and a support wire ring (4011) is provided on the support (401) close to the base wire opening (4023). After the arresting rope (3) is output from the first arm wire opening, it first passes through the support wire ring (4011) and then enters the base (4) through the base wire opening (4023) and is wound on the reel assembly (5).

4. The arm-type recovery system for recovering a fixed-wing UAV according to claim 1, characterized in that: The upper end of the forearm body (202) of the forearm (2) is provided with a forearm rotating shaft (2021), the upper ends of the side walls on both sides of the concave portion are provided with lower covers (20331), and an upper cover (2031) is fixedly provided above the lower cover (20331), and the forearm rotating shaft (2021) is rotatably arranged in a circular hole formed between the upper cover (2031) and the lower cover (20331) on the corresponding side.

5. The arm-type recovery system for recovering a fixed-wing UAV according to claim 1, characterized in that: The arm body (202) of the arm (2) is a circular tube structure, and the lower end of the arm body (202) is provided with a lower end cap (201) with a first arm wire hole, and the arresting rope (3) enters the arm body (202) through the first arm wire hole of the lower end cap (201), and the upper end of the arm body (202) is provided with a second arm wire hole, and the upper arm connecting seat (102) of the arm (1) is provided with a first conductor (1021), a second conductor (1022) and a second arm wire hole, and the arresting rope (3) is output from the second arm wire hole, passes through the second conductor (1022) and the first conductor (1021) in sequence, and then enters the arm body (101) of the arm (1) through the second arm wire hole.

6. The arm-type recovery system for recovering a fixed-wing UAV according to claim 1, characterized in that: The forearm driving device comprises a forearm motor (2032) and a harmonic reducer (2035) connected in sequence, wherein the output end of the harmonic reducer (2035) is fixedly connected to the lower end of a connecting shaft (2034), the upper end of the connecting shaft (2034) is inserted into a sleeve (20332) on the lower side of the connecting seat (2033), and the upper end of the connecting shaft (2034) and the sleeve (20332) are key-connected.

7. The arm-type recovery system for recovering a fixed-wing UAV according to claim 1, characterized in that: The base (4) comprises a box body (402), and two supports (401) are both arranged on a top plate (4021) of the box body (402), and a base wire hole (4023) is provided on the top plate (4021), and the reel assembly (5) is arranged inside the box body (402), and a support foot (4022) is provided at the lower end of the box body (402); the reel assembly (5) comprises a reel driving device and a reel frame (503), wherein baffles are provided on both sides of the reel frame (503), a reel shaft (5032) is provided inside the reel frame (503), and the reel shaft (5032) is driven to rotate by the reel driving device, the arresting rope (3) is wound around the reel shaft (5032) and the winding position is limited by the baffles on both sides of the reel frame (503), and guide plates (5031) are provided on both sides above the reel frame (503) along the tangential direction.

8. A control method for an arm-type recovery system for recovering a fixed-wing UAV according to claim 1, characterized in that: The steps include: Step 1: Determine the motion control algorithm. After the drone enters the recovery orbit, there is always relative motion between the drone and the end of the robotic arm unit. This relative motion is the disturbance generated by the outside world. Based on the prediction algorithm of fast Fourier transform and adaptive fuzzy-PID control, the above disturbance is first subjected to fast Fourier transform: f Obs，i =f FFT，i (1); In the above formulas (1) to (3), f obs,i represents the predicted frequency of the end of the robot unit, represents the predicted phase angle at the end of the robot unit, a Obs,i represents the predicted amplitude at the end of the robot unit, f FFT,i It means that the peak detector identifies the frequency corresponding to the i-th harmonic in the main N harmonic functions, represents the estimated value after Fourier transformation at time t, represents the estimated value of the first-order derivative after Fourier transform at time t, and T represents the time value within a period of ΔT; Step 2: Superimpose the estimated harmonics of different frequencies to predict T pre The expected motion signal after time, that is, the expected position W at the end of the robot unit pre (t): In the above formula (7), the compensation value ρ(t) is a constant at time t: in, represents the estimated value of the odd wave at time T; Step 3: Construct the fuzzy control algorithm at the end of the robot arm unit: U(t)=K P E(t)+K I ∑E(t)+K D EC(t) (8); In the above formula (8), U(t) represents the output value of the PID regulator, E(t) represents the system input deviation, EC(t) represents the change in the system input deviation, and the parameter K P , K I , K D represents the fuzzy control parameters, where: E(t)= w (t)-W pre (t) (9); In the above formula (9), H(t) represents the current position of the end of the robot arm unit, W pre (t) is obtained by the above formula (7); Apply fuzzy theory to establish parameter K P , K I , K D The relationship between the absolute value of the input deviation |E| and the absolute value change rate of the deviation |EC| is: In the above formulas (10) to (12), μ i represents the membership function, K Pi , K Ii , K Di Indicates the weighted value under different states; Step 4: Determine the expected movement angles A1 and B1 of the large arms (1) of the two robot arm units and the expected movement angles A2 and B2 of the small arms (2) of the two robot arm units: A1=B1=sec(U(t) / 2800); A2=B2=-2×sec(U(t) / 2800); Where U(t) is obtained by the above formula (8).

9. The control method of the arm-type recovery system for recovering a fixed-wing UAV according to claim 8, characterized in that: In step 1, the relative motion between the drone and the end of the robotic arm unit is represented by a superposition of a set of simple harmonic waves with different periods: In the above formula (4), A i represents the amplitude corresponding to the i-th simple harmonic wave, f i represents the frequency corresponding to the i-th simple harmonic wave, represents the phase corresponding to the i-th simple harmonic wave, and ρ(t) represents the initial compensation value of the interference signal. Therefore, in the above equations (1) to (3): In the above formulas (5) to (6), A FFT,i It means that the peak detector identifies the amplitude corresponding to the i-th harmonic in the main N harmonic functions, It means that the peak detector identifies the phase corresponding to the i-th harmonic in the main N harmonic functions.

10. The control method of the arm-type recovery system for recovering a fixed-wing UAV according to claim 8, characterized in that: In step 3, for the convenience of computer processing and implementation, the absolute value of the input deviation |E|, the absolute value change rate of the deviation |EC| and the output membership function in the above equations (10) to (12) are all linear functions, and |E|, |EC| and PID parameter K are set to P , K I , K D The fuzzy control domain is described by four different fuzzy linguistic variables: zero (symbol Z), small (symbol S), medium (symbol M), and large (symbol B). Then, the membership functions of the fuzzy linguistic variables corresponding to the domain involving the fuzzy deviation |E| and the membership functions of the fuzzy linguistic variables corresponding to the domain involving the fuzzy deviation |EC| are obtained respectively. In addition, the above four descriptions of Z, S, M, and B are |E|, |EC|, and K P , K I , K D The four membership components of In order to improve the system response speed and system adjustment accuracy, the following fuzzy control rules are designed: Table 1 K P Fuzzy Control Rules Table 2 K I Fuzzy Control Rules Table 3 K D Fuzzy Control Rules After obtaining the values ​​of |E| and |EC|, the membership component and component weight value of |E| are obtained according to the membership function of the fuzzy linguistic variable corresponding to the domain involving the fuzzy deviation |E|, and the membership component and component weight value of |EC| are obtained according to the membership function of the fuzzy linguistic variable corresponding to the domain involving the fuzzy deviation |EC|. Then, the membership component and component weight value of |E| and the membership component and component weight value of |EC| are substituted into the above Table 1 to obtain K. P Substitute the membership components into Table 2 above to obtain K I Substitute the membership components into Table 3 above to obtain K D The membership component of K is finally determined according to the parameter value table obtained from the experiment. P , K D , K I .

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