A smart homing satellite guidance system

Abstract

This invention discloses an intelligent homing satellite guidance system, comprising: a target attack subsystem and a target indication subsystem; the target indication subsystem is used to search for, discover, and attach to a target, and to send a signal of the target's real-time position coordinates to the target attack subsystem; the target attack subsystem calculates its relative position to the target in real time based on the target coordinate signal sent by the target indication subsystem and the ephemeris information of the navigation satellite, guiding the target attack subsystem to attack the target; wherein, the target attack subsystem and the target indication subsystem are respectively equipped with satellite receiver I and satellite receiver II, which respectively receive the ephemeris information of the navigation satellites in their respective airspaces, and respectively calculate the pseudorange information of their respective positions, and then calculate the coordinate information of their respective positions.

Description

Technical Field

[0001] This invention relates to the field of guidance and control technology, and more specifically to an intelligent homing satellite guidance system. Background Technology

[0002] Satellite guidance is a low-cost guidance method widely used in drones, missiles, and other fields. Its working principle is as follows: a satellite receiver is installed on the aircraft to acquire the aircraft's coordinates (accuracy, latitude, and altitude) in real time; the coordinates of the launch point and target point are pre-stored in the flight control computer; during flight, the flight control computer calculates the relative position of the aircraft and the target in real time, and uses guidance control algorithms to calculate control commands to guide the aircraft towards the target. The positioning accuracy of traditional satellite receivers is around 10 meters.

[0003] Differential satellite navigation is a satellite positioning technology that first uses a differential satellite receiving reference station with known precise three-dimensional coordinates to obtain pseudorange or position correction values. These correction values ​​are then sent to the user (or other satellite receivers) in real time or afterward to correct the user's measurement data, thereby improving satellite positioning accuracy. The key to this technology is the differential satellite receiving reference station with known three-dimensional coordinates. The satellite receiver is placed on this reference station, and by comparing the satellite information received by the receiver with the known precise coordinates of the reference station, the pseudorange error in the vicinity of the reference station is corrected, thus improving the satellite receiver's positioning accuracy (up to within 0.1m).

[0004] Satellite guidance offers advantages such as low cost and fire-and-forget capability, but it also has limitations. First, its accuracy is insufficient; traditional satellite-guided spacecraft have a hit accuracy of around 10 meters, often only suitable for attacking clustered targets or large structures like bridges, making precise attacks on single point targets difficult. Second, it struggles against moving targets. The target coordinates for satellite-guided spacecraft are pre-programmed into the flight control computer, often indicating a fixed target or a target with known motion patterns and limited maneuverability (such as large ships). For ground-based vehicles or other targets with some mobility, satellite-guided spacecraft struggle to achieve precise attacks. While differential satellite positioning offers high accuracy, it requires precise three-dimensional coordinates of a base station, which is difficult to achieve in complex battlefield environments.

[0005] In summary, existing satellite guidance systems suffer from limitations in achieving high-precision strikes against targets and in engaging moving targets. Therefore, to fill the gaps in the application capabilities of existing satellite guidance systems, it is necessary to leverage advancements in intelligent technologies to develop a satellite guidance system capable of target search and high-precision strikes against moving targets. Summary of the Invention

[0006] In view of this, the present invention provides an intelligent homing satellite guidance system, which has target search capability and can achieve high-precision strikes against moving targets.

[0007] The technical solution of the present invention is as follows: an intelligent homing satellite guidance system, comprising: a target attack subsystem and a target indication subsystem; the target indication subsystem is used to search for, discover, and attach to a target, and send a signal of the real-time position coordinates of the target to the target attack subsystem; the target attack subsystem calculates its relative position to the target in real time based on the target coordinate signal sent by the target indication subsystem and the ephemeris information of the navigation satellite, and guides the target attack subsystem to attack the target; wherein, the target attack subsystem and the target indication subsystem are respectively equipped with satellite receiver I and satellite receiver II, which respectively receive the ephemeris information of the navigation satellites in their respective airspaces, and respectively calculate the pseudorange information of their respective positions, and then calculate the coordinate information of their respective positions.

[0008] Preferably, the flight platform I of the target attack subsystem is a projectile-type aircraft with a signal receiver mounted on its nose; the satellite receiver I is located in the signal receiver, which can receive ephemeris signals sent by navigation satellites, position information of the target indication subsystem sent by the coordinate indicator in the target indication subsystem, and pseudorange information from the target indication subsystem to each navigation satellite, and can calculate the relative distance between the target attack subsystem and the target indication subsystem according to the relative position calculation algorithm; wherein, the satellite receiver II is located in the coordinate indicator, and the coordinate indicator further includes: a signal transmitter, which transmits the pseudorange information of the target indication subsystem's location from each navigation satellite and the position information of the target indication subsystem calculated by the satellite receiver II to the signal receiver in the target attack subsystem.

[0009] Preferably, the relative position calculation algorithm is as follows:

[0010] Let the coordinates of the target indication subsystem be (x t ,y t ,z t The coordinates of the target attack subsystem are (x...). m ,y m ,z m The coordinates of the j-th navigation satellite are... Where j is a positive integer; let the relative coordinates from the target attack subsystem to the target indication subsystem be (x, y, z), then x = x m -x t y = y m -y t , z = z m -zt ;

[0011] use and Let represent the pseudorange received by satellite receiver II on the target indication subsystem and satellite receiver I on the target attack subsystem from the j-th navigation satellite, respectively. Then the pseudorange difference between the target attack subsystem and the target indication subsystem is:

[0012] Let the actual distance from the target indication subsystem to the j-th navigation satellite be . Its expression is:

[0013] Let c be the speed of light, dT t dT represents the clock bias of satellite receiver II on the target indication subsystem. m The clock bias of satellite receiver I on the target attack subsystem, and the distance difference d between the target indication subsystem and the target attack subsystem caused by the clock bias, are given by d = c(dT). m -dT t );

[0014] Construct the state variable X = [xyzd] T Let N be the number of receivable navigation satellites. Construct an N×1 dimensional vector Z, where the elements of vector Z are the pseudorange differences between each navigation satellite calculated by the target attack subsystem and the target indication subsystem. The expression for vector Z is:

[0015]

[0016] Construct an N×1 dimensional intermediate transformation vector H, whose expression is:

[0017]

[0018] The solution expression for state variable X is:

[0019] X=(H T H) -1 H T Z

[0020] By solving the equation using the least squares method, we can obtain the values ​​of each parameter in the state variable X, and then calculate the coordinates of the target attack subsystem relative to the target indication subsystem, thereby obtaining the relative distance between the target attack subsystem and the target indication subsystem.

[0021] Preferably, the target indication subsystem further includes: a flight platform II, a target search device, and an attachment device; the flight platform II is used to carry the coordinate indicator, the target search device, and the attachment device, with the coordinate indicator and the target search device located on the front and back of the flight platform II respectively, and attachment devices are provided at opposite ends of the flight platform II, one of which is rotatable and the other is fixed; after the target indication subsystem flies to the set range of the target, the flight platform II adjusts the attitude of the target indication subsystem to unfold the rotatable attachment device and align it with the target to be attached part; subsequently, the flight platform II adjusts the flight trajectory of the target indication subsystem, moves closer to the direction of the designated target part, and contacts and adheres the adhesive surface I in the rotatable attachment device to the designated target part; after the adhesive surface I is adhered to the designated target part, the flight platform II adjusts the flight attitude so that the adhesive surface II in the other attachment device contacts and adheres to the target to be attached part, thereby realizing the attachment of the target indication subsystem to the target.

[0022] Preferably, the adhesive surface I and adhesive surface II are respectively covered by adhesive surface protective cover I and adhesive surface protective cover II; wherein, adhesive surface protective cover I covers the adhesive surface I and is fixed by explosion bolt I, adhesive surface protective cover II covers the adhesive surface II and is fixed by explosion bolt II, and the explosion bolt I and explosion bolt II are used to disconnect the connection between adhesive surface protective cover I and adhesive surface I and between adhesive surface protective cover II and adhesive surface II, thus exposing adhesive surface I and adhesive surface II.

[0023] Preferably, the flight platform II is a small quadcopter.

[0024] Preferably, the target search device includes: an image camera, a gimbal, and an image transmitter. The image camera is mounted on the gimbal and is used to capture images of the battlefield environment. The gimbal is used to rotate the image camera, thereby expanding the detection field of view of the target indication subsystem. The image transmitter is used to transmit the image information captured by the image camera to the ground station.

[0025] Preferably, the image camera of the target search device is a white light camera, a night vision camera, or an infrared camera.

[0026] Preferably, the flight platform I of the target attack subsystem can also be a rotorcraft or a fixed-wing aircraft.

[0027] Preferably, the target indication subsystem can also fly alongside the target within a set range.

[0028] Beneficial effects:

[0029] 1. The satellite guidance system of the present invention has target search capability and can achieve high-precision strike on moving targets, enabling satellite-guided weapons to have the capability to strike moving targets with high precision. This overcomes the limitation of traditional satellite-guided weapons that can only attack stationary cluster targets, and improves the hit accuracy of satellite-guided weapons from 10m to within 1.5m, solving the problem that existing satellite guidance systems are unable to strike moving targets with high precision.

[0030] 2. This invention has a fine target search capability: The flight platform of the signal transmitter carried by the target attack subsystem and the target search device carried by the target indication subsystem is an ultra-small rotorcraft. This flight platform has the characteristics of small size, strong stealth penetration capability and long-term loitering capability, which can covertly conduct long-term and large-area fine search of targets, and has a stronger detection capability for concealed targets. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the working principle of the satellite guidance system of the present invention.

[0032] Figure 2 This is a flowchart illustrating the workflow of the satellite guidance system of this invention.

[0033] Figure 3 This is a schematic diagram of the installation of the signal receiver on the target attack subsystem in this invention.

[0034] Figure 4 This is a schematic diagram of the target indication subsystem in this invention.

[0035] Figure 5 This is a schematic diagram showing the morphological changes of the target indication subsystem of the satellite guidance system of the present invention under different working states.

[0036] Figure 6 (a) is a schematic diagram of the target indication subsystem before it is attached to the target, and (b) is a schematic diagram of the target indication subsystem after it is attached to the target.

[0037] Among them, 1-signal receiver, 2-coordinate indicator, 3-flight platform II, 4-target search device, and 5-attachment device. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] This embodiment provides an intelligent homing satellite guidance system that has target search capabilities and can achieve high-precision strikes against moving targets.

[0040] like Figure 1 As shown, the satellite guidance system includes: a target attack subsystem and a target indication subsystem;

[0041] like Figure 3 As shown, the flight platform I of the target attack subsystem is a projectile-type aircraft, with a signal receiver 1 mounted on its nose. The signal receiver 1 includes a satellite receiver I, which can receive ephemeris signals sent by navigation satellites. Simultaneously, the signal receiver 1 can also receive the position information of the target indication subsystem and the pseudorange information from the target indication subsystem to each navigation satellite sent by the coordinate indicator 2 in the target indication subsystem. It can also calculate the relative distance between the target attack subsystem and the target indication subsystem using a relative position calculation algorithm. The coordinate indicator 2 includes a satellite receiver II and a signal transmitter. The satellite receiver II can receive ephemeris information sent by navigation satellites over its area and calculate the pseudorange information from the satellite receiver II (i.e., the target indication subsystem) to each navigation satellite based on this ephemeris information. It further calculates the coordinates (precision, latitude, and altitude) of the target indication subsystem's location. The signal transmitter can send the pseudorange information from the target indication subsystem's location to each navigation satellite, calculated by the satellite receiver II, and the position information of the target indication subsystem to the signal receiver 1 in the target attack subsystem.

[0042] The algorithm for calculating the relative position is as follows:

[0043] Let the coordinates of the target indication subsystem be (x t ,y t ,z t The coordinates of the target attack subsystem are (x...). m ,y m ,z m The coordinates of the j-th navigation satellite are... Where j is a positive integer; let the relative coordinates from the target attack subsystem to the target indication subsystem be (x, y, z), then x = x m -x t y = y m -y t , z = z m -z t ;

[0044] use and Let represent the pseudorange received by satellite receiver II on the target indication subsystem and satellite receiver I on the target attack subsystem from the j-th navigation satellite, respectively. Then the pseudorange difference between the target attack subsystem and the target indication subsystem is:

[0045] Let the actual distance from the target indication subsystem to the j-th navigation satellite be . Its expression is:

[0046] Let c be the speed of light, dT tdT represents the clock bias of satellite receiver II on the target indication subsystem. m The clock bias of satellite receiver I on the target attack subsystem, and the distance difference d between the target indication subsystem and the target attack subsystem caused by the clock bias, are given by d = c(dT). m -dT t );

[0047] Construct the state variable X = [xyzd] T Let N be the number of receivable navigation satellites. Construct an N×1 dimensional vector Z, where the elements of vector Z are the pseudorange differences between each navigation satellite calculated by the target attack subsystem and the target indication subsystem. The expression for vector Z is:

[0048]

[0049] Construct an N×1 dimensional intermediate transformation vector H, whose expression is:

[0050]

[0051] The solution expression for state variable X is:

[0052] X=(H T H) -1 H T Z (3)

[0053] By solving equation (3) using the least squares method, the values ​​of each parameter in the state variable X can be obtained, and then the coordinates of the target attack subsystem relative to the target indication subsystem can be calculated, thereby obtaining the relative distance between the target attack subsystem and the target indication subsystem.

[0054] The flight control computer on the target attack subsystem calculates flight control commands based on the calculated relative distance between the target attack subsystem and the target indication subsystem, in order to control the target attack subsystem to fly toward the target indication subsystem;

[0055] like Figure 4 As shown, the target indication subsystem also includes: flight platform II 3, target search device 4, and attachment device 5; flight platform II 3 is used to carry coordinate indicator 2, target search device 4, and attachment device 5, with coordinate indicator 2 and target search device 4 located on the front and back of flight platform II 3 respectively, and attachment devices 5 are provided at opposite ends of flight platform II 3, with one attachment device 5 being rotatable and the other being fixed; as Figure 5 and Figure 6As shown, after the target indication subsystem flies to the vicinity of the target, the flight platform II3 adjusts the attitude of the target indication subsystem so that the rotatable attachment device 5 can be deployed and aligned with the target attachment area. Subsequently, the flight platform II3 adjusts the flight trajectory of the target indication subsystem, moving closer to the location of the designated target area, and contacts and adheres the adhesive surface I in the rotatable attachment device 5 to the designated target area. After the adhesive surface I is adhered to the designated target area, the flight platform II3 adjusts its flight attitude so that the bottom surface of the target indication subsystem is parallel to the plane of the target attachment area, and contacts and adheres the adhesive surface II in another attachment device 5 (fixed attachment) to the target attachment area, thereby achieving the attachment of the target indication subsystem to the target.

[0056] In this embodiment, the adhesive surface I in the rotatable attachment device 5 and the adhesive surface II in the fixed attachment device 5 are respectively covered and protected by adhesive surface protective cover I and adhesive surface protective cover II; wherein, adhesive surface protective cover I covers the adhesive surface I and is fixed by explosion bolt I, adhesive surface protective cover II covers the adhesive surface II and is fixed by explosion bolt II, and when explosion bolt I and explosion bolt II are applied, the connection between adhesive surface protective cover I and adhesive surface I and adhesive surface II is released, and adhesive surface I and adhesive surface II are exposed.

[0057] In this embodiment, the flight platform I of the target attack subsystem can also be a rotorcraft or a fixed-wing aircraft.

[0058] In this embodiment, the flight platform II3 is a small quadcopter aircraft that can cruise along a predetermined trajectory and has the ability to take off, land, hover, and maneuver.

[0059] In this embodiment, the target search device 4 includes: an image camera, a gimbal, and an image transmitter. The image camera is mounted on the gimbal and is used to capture images of the battlefield environment. The gimbal can rotate the image camera, which can expand the detection field of view of the target indication subsystem. The image transmitter can transmit the image information captured by the image camera to the ground station. Ground station personnel can perceive the battlefield environment and select and lock onto targets based on the transmitted image information.

[0060] In this embodiment, the image camera of the target search device 4 can be a white light camera, a night vision camera, or an infrared camera. When a white light camera is used, it can capture images of the target area environment and compare the captured images with the target images to locate the target.

[0061] In this embodiment, the target indication subsystem can not only attach to a designated part of the target, but also fly alongside the target in the vicinity (within a set range).

[0062] The overall working principle of this satellite guidance system is as follows:

[0063] like Figure 2As shown, the target indication subsystem is released and flies towards the target area. Simultaneously, satellite receiver II in coordinate indicator 2 starts working, receiving ephemeris information from navigation satellites in the area and calculating the location in real time. After reaching the target area, the target indication subsystem performs cruise flight, the target search device 4 works, takes pictures of the surrounding environment, and transmits the environmental images back to the ground station. The ground station operator finds and locks onto the target based on the transmitted environmental images and transmits the target lock command to the target indication subsystem. When the target indication subsystem receives the target lock command, it flies towards the target. After flying to the vicinity of the target (for example, the distance between the target indication subsystem and the target is less than 0.5m), it finds the part of the target that can be attached and flies to the vicinity of that part of the target.

[0064] During the above stages, the rotatable attachment device 5 is in a folded state;

[0065] After the target designation subsystem flies to the designated attack location, flight platform II3 adjusts its attitude so that the rotatable attachment device 5 is deployed and aligned with the designated target location. Explosive bolts I and II act, releasing the connection between adhesive protective cover I and adhesive surface I, and between adhesive protective cover II and adhesive surface II. Adhesive protective cover I and adhesive protective cover II detach from their respective attachment devices 5, exposing adhesive surfaces I and II. Flight platform II3 adjusts its flight trajectory, moving closer to the designated target location, bringing adhesive surface I into contact with and bonding it to the designated target location. After adhesive surface I is bonded to the designated target location, flight platform II3 adjusts its flight attitude so that the plane of flight platform II3 is parallel to the plane of the designated target location, bringing adhesive surface II into contact with and bonding it to the designated target location, thus achieving the attachment of the target designation subsystem to the designated target location.

[0066] Once the target indication subsystem is attached to the designated part of the target, the signal transmitter in coordinate indicator 2 starts to work and begins to transmit pseudorange information from the location of the target indication subsystem to each navigation satellite.

[0067] The target attack subsystem is launched and flies towards the target area. When the satellite receiver I in the signal receiver 1 on the target attack subsystem receives the ephemeris signal of the navigation satellites in the area, and the signal receiver 1 receives the pseudorange signal from the location of the target indication subsystem to each navigation satellite and the position information of the target indication subsystem transmitted by the coordinate indicator 2, the relative distance between the target attack subsystem and the target indication subsystem is calculated according to the relative position calculation algorithm. The flight control computer on the target attack subsystem calculates the guidance control command based on the relative distance information between the target attack subsystem and the target indication subsystem, and then forms the guidance information of the target attack subsystem to guide the target attack subsystem to the target.

[0068] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A smart homing satellite guidance system, characterized in that, include: Target attack subsystem and target designation subsystem; The target indication subsystem is used to search for, discover, and attach to targets, as well as send the real-time position coordinates of the targets to the target attack subsystem. The target attack subsystem calculates its relative position to the target in real time based on the target coordinate signals sent by the target indication subsystem and the ephemeris information of the navigation satellites, guiding the target attack subsystem to attack the target. The target attack subsystem and the target indication subsystem are respectively equipped with satellite receiver I and satellite receiver II, which receive the ephemeris information of the navigation satellites in their respective airspaces, and calculate the pseudorange information of their respective positions, and then calculate the coordinate information of their respective positions. The flight platform I of the target attack subsystem is a projectile-type aircraft with a signal receiver (1) mounted on its head. The satellite receiver I is located in the signal receiver (1). The signal receiver (1) can receive ephemeris signals sent by navigation satellites, position information of the target indication subsystem sent by the coordinate indicator (2) in the target indication subsystem, and pseudorange information of the target indication subsystem to each navigation satellite. It can also calculate the relative distance between the target attack subsystem and the target indication subsystem according to the relative position calculation algorithm. The satellite receiver II is located in the coordinate indicator (2). The coordinate indicator (2) also includes a signal transmitter. The signal transmitter sends the pseudorange information of the target indication subsystem's location to each navigation satellite and the position information of the target indication subsystem calculated by the satellite receiver II to the signal receiver (1) in the target attack subsystem. The relative position calculation algorithm is as follows: Let the coordinates of the target indication subsystem be (x... t ,y t ,z t The coordinates of the target attack subsystem are (x...). m ,y m ,z m The coordinates of the j-th navigation satellite are... Where j is a positive integer; let the relative coordinates from the target attack subsystem to the target indication subsystem be (x, y, z), then x = x m -x t y = y m -y t , z = z m -z t ; use and Let represent the pseudorange received by satellite receiver II on the target indication subsystem and satellite receiver I on the target attack subsystem from the j-th navigation satellite, respectively. Then the pseudorange difference between the target attack subsystem and the target indication subsystem is: Let the actual distance from the target indication subsystem to the j-th navigation satellite be . Its expression is: Let c be the speed of light, dT t dT represents the clock bias of satellite receiver II on the target indication subsystem. m The clock bias of satellite receiver I on the target attack subsystem, and the distance difference d between the target indication subsystem and the target attack subsystem caused by the clock bias, are given by d = c(dT). m -dT t ); Construct the state variable X = [xyzd] T Let N be the number of navigation satellites that can be received. Construct an N×1 dimensional vector Z. The elements of vector Z are the pseudorange differences between each navigation satellite calculated by the target attack subsystem and the target indication subsystem. The expression for vector Z is: Construct an N×4 dimensional intermediate transformation vector H, whose expression is: The solution expression for state variable X is: X=(H T H) -1 H T Z (3) By solving equation (3) using the least squares method, the values ​​of each parameter in the state variable X can be obtained, and then the coordinates of the target attack subsystem relative to the target indication subsystem can be calculated, thus obtaining the relative distance between the target attack subsystem and the target indication subsystem.

2. The intelligent homing satellite guidance system as described in claim 1, characterized in that, The target indication subsystem further includes: flight platform II (3), target search device (4), and attachment device (5); flight platform II (3) is used to carry coordinate indicator (2), target search device (4), and attachment device (5), and the coordinate indicator (2) and target search device (4) are located on the front and back of flight platform II (3) respectively. Attachment devices (5) are provided at opposite ends of flight platform II (3), and one of the two attachment devices (5) is rotatable and the other is fixed; when the target indication subsystem flies into the set range of the target, flight platform II... (3) Adjust the attitude of the target indication subsystem so that the rotatable attachment device (5) is deployed and aligned with the target to be attached; then, the flight platform II (3) adjusts the flight trajectory of the target indication subsystem and moves closer to the target to be attached, so that the adhesive surface I in the rotatable attachment device (5) contacts and adheres to the target to be attached; after the adhesive surface I is adhered to the target to be attached, the flight platform II (3) adjusts the flight attitude so that the adhesive surface II in the other attachment device (5) contacts and adheres to the target to be attached, thereby realizing the attachment of the target indication subsystem to the target.

3. The intelligent homing satellite guidance system as described in claim 2, characterized in that, The adhesive surface I and adhesive surface II are respectively covered by adhesive surface protective cover I and adhesive surface protective cover II; wherein, adhesive surface protective cover I covers the adhesive surface I and is fixed by explosion bolt I, and adhesive surface protective cover II covers the adhesive surface II and is fixed by explosion bolt II. When explosion bolt I and explosion bolt II are applied, the connection between adhesive surface protective cover I and adhesive surface I and adhesive surface II is released, and adhesive surface I and adhesive surface II are exposed.

4. The intelligent homing satellite guidance system as described in claim 2, characterized in that, The flight platform II (3) is a small quadcopter.

5. The intelligent homing satellite guidance system as described in claim 2, characterized in that, The target search device (4) includes: an image camera, a gimbal, and an image transmitter. The image camera is mounted on the gimbal and is used to capture images of the battlefield environment. The gimbal is used to rotate the image camera, thereby expanding the detection field of the target indication subsystem. The image transmitter is used to transmit the image information captured by the image camera to the ground station.

6. The intelligent homing satellite guidance system as described in claim 4, characterized in that, The image camera of the target search device (4) is a white light camera, a night vision camera, or an infrared camera.

7. The intelligent homing satellite guidance system as described in any one of claims 1-5, characterized in that, The target attack subsystem's flight platform I is a rotary-wing or fixed-wing aircraft.

8. The intelligent homing satellite guidance system as described in any one of claims 1-5, characterized in that, The target designation subsystem can also accompany the target within a set range.

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