Fig.1

Schematic diagram of UAV air recovery scenario

Table 1

Model parameters of soft towed grabber

Fig.2

Key longitudinal aerodynamic coefficients of grabber

Fig.3

Control surface efficient coefficient of grabber

Fig.4

Lateral stability coefficients of grabber

Fig.5

Force diagram of the grabber in equilibrium state

Fig.6

Diagram block of grabber position and attitude control

Fig.7

Control loop of inner loop angular rate

Table 2

Control parameters of towed cable

Fig.8

Graphic geometry relationship of the grabber’s visual position

Fig.9

Definition of function and proportional relationship of the front and rear rudder surfaces of the grabber

Table 3

Equivalent control surfaces’ efficiency and maneuvering sensitivity of grabber

Fig.10

Response of pitch angle attitude

Fig.11

Response of roll angle attitude

Fig.12

Position tracking response of soft towed grabber （vehicle speed）

Fig.13

Response of inner loop attitude and airflow angle under end position maneuver

Fig.14

Response of control surfaces under end position maneuver

Fig.15

Forces and moments and towed angle of soft towed system （vehicle speed）

Fig.16

Position tracking response of soft towed grabber （designed speed）

Fig.17

Forces and moments and towed angle of soft towed system （designed speed）

Fig.18

Hardware system of grabber based on vision positioning system

Fig.19

On-vehicle demonstration test platform in static mode

Fig.20

Definition of function and polarity of remote operator

Table 4

Relationship between grabber attitude response and polarity of control command and corresponding rudder surfaces

Fig.21

Schematic diagram of on-vehicle demonstration test platform

Fig.22

Pitch channel speed reduction command

Fig.23

Attitude responses of grabber without control

Fig.24

Relationship of lateral attitude and vision position

Fig.25

Relationship of lateral displacement and velocity of vision positioning system

Fig.26

Velocity of towed grabber in on-vehicle test

Fig.27

Attitude responses of towed grabber in on-vehicle test

Fig.28

Velocity of towed grabber in the NED frame

Fig.29

Relative velocity components in body axis

Fig.30

Relative velocity components in the body axis from vehicle test data

Fig.31

Towed velocity and vision positioning information