Method and system for following target
A system and a method for following a target are disclosed. The system includes steps of: A. providing a signal transmitting RF module mounted on a target, a signal receiving RF module on a moving carrier, and at least 3 laser rangefinders aside the signal receiving RF module; B. calculating an estimated distance and a directional angle; C. driving the moving carrier toward the target while maintaining the directional angle substantially 0 degree; D. repeating step B and step C until the estimated distance is shorter than a control exchange distance; E. dynamically tracking the target by one of the laser rangefinders so that a relative distance between said laser rangefinder and the target can be successively calculated while calculating the estimated distance and the directional angle; and F. driving the moving carrier to keep the relative distance within a predetermined range and maintain the normal direction substantially toward the target.
1. A method for following a target, comprising the steps of:
A. providing a signal transmitting radio frequency (RF) module mounted on a target, a signal receiving RF module on a moving carrier, and at least 3 laser rangefinders aside the signal receiving RF module;
B. calculating an estimated distance between the signal transmitting RF module and the signal receiving RF module, and a directional angle between a direction from the signal transmitting RF module to the signal receiving RF module and a normal direction to a front plane of the moving carrier where the signal receiving RF module is located by RF signals sent from the signal transmitting RF module and received by the signal receiving RF module, wherein a first laser rangefinder has a tracing direction substantially along with the normal direction for sending and receiving laser beams;
C. driving the moving carrier toward the target while maintaining the directional angle substantially 0 degree;
D. repeating step B and step C until the estimated distance is shorter than a control exchange distance;
E. dynamically tracking the target by one of the laser rangefinders so that a relative distance between said laser rangefinder and the target is able to be successively calculated while calculating the estimated distance and the directional angle; and
F. driving the moving carrier to keep the relative distance within a predetermined range and maintain the normal direction substantially toward the target.
2. The method according to claim 1 , further comprising steps after step E and step F:
E1. checking whether the relative distance is shorter than a predetermined percentage of the control exchange distance or no laser rangefinder traces the target; and
E2. if one of the condition in step E1 happens, repeating step B and step C; otherwise, processing step F.
3. The method according to claim 2 , wherein the predetermined percentage ranges from 50% to 90%.
4. The method according to claim 1 , further comprising steps after step F:
G. checking whether a difference between the directional angle and a relative angle between the normal direction and a connecting line from the first laser rangefinder to the target falls within a predetermined range of degrees; and
H. if a result of step G is yes, repeating step F; if the result of step G is no, repeating step B and step C.
5. The method according to claim 4 , wherein the predetermined range of degrees is +3%˜−3%.
6. The method according to claim 1 , wherein the normal direction substantially toward the target is maintained by turning the moving carrier left until the first laser rangefinder traces the target if a second laser rangefinder on the left of the first laser rangefinder traces the target and turning the moving carrier right until the first laser rangefinder traces the target if a third laser rangefinder on the right of the first laser rangefinder traces the target.
7. The method according to claim 6 , wherein tracing directions of the second laser rangefinder and/or the third laser rangefinder deviate from that of the first laser rangefinder to a predetermined angle.
8. The method according to claim 7 , wherein the predetermined angle is not larger than 45°.
9. The method according to claim 1 , wherein the control exchange distance ranges from 1.5 m to 2.5 m.
10. A system for following a target, comprising:
a signal transmitting RF module, mounted on a target to be followed, working to send RF signals;
a signal receiving RF module, mounted on a moving carrier, pairing with the signal transmitting RF module, working to receive the RF signals sent from the signal transmitting RF module;
at least 3 laser rangefinders, mounted aside the signal receiving RF module, each calculating a relative distance between itself and the target; and
a controller, signally connected with the signal receiving RF module and the at least 3 laser rangefinders, operating to calculate an estimated distance between the signal transmitting RF module and the signal receiving RF module, and a directional angle between a direction from the signal transmitting RF module to the signal receiving RF module and a normal direction to a front plane of the moving carrier where the signal receiving RF module is located by RF signals sent from the signal transmitting RF module and received by the signal receiving RF module, send commands to control moving of the moving carrier, and dynamically track the target by one of the laser rangefinders so that the relative distance is able to be successively calculated,
wherein a first laser rangefinder has a tracing direction substantially along with the normal direction for sending and receiving laser beams; the controller keeps calculating the estimated distance and the directional angle and drives the moving carrier toward the target while maintains the directional angle substantially 0 degree until the estimated distance is shorter than a control exchange distance; when the estimated distance is shorter than the control exchange distance, the controller still calculates the estimated distance and the directional angle while drives the moving carrier to keep the relative distance within a predetermined range and maintain the normal direction substantially toward the target.
11. The system according to claim 10 , wherein when the estimated distance is found to be shorter than the control exchange distance, the controller further checks whether the relative distance is shorter than a predetermined percentage of the control exchange distance or no laser rangefinder traces the target; if one of said conditions happens, the controller utilizes the estimated distance and the directional angle to drive the moving carrier.
12. The system according to claim 11 , wherein the predetermined percentage ranges from 50% to 90%.
13. The system according to claim 10 , wherein when the controller utilizes the relative distance and a relative angle, which is between the normal direction and a connecting line from the first laser rangefinder to the target, to drive the moving carrier, the controller also checks whether a difference between the directional angle and the relative angle falls within a predetermined range of degrees; if the difference falls within the predetermined range of degrees, keep driving the moving carrier with the relative distance and the relative angle; if the difference does not fall within the predetermined range of degrees, drive the moving carrier with the estimated distance and the directional angle.
14. The system according to claim 13 , wherein the predetermined range of degrees is +3%˜−3%.
15. The system according to claim 10 , wherein the normal direction substantially toward the target is maintained by turning the moving carrier left until the first laser rangefinder traces the target if a second laser rangefinder on the left of the first laser rangefinder traces the target and turning the moving carrier right until the first laser rangefinder traces the target if a third laser rangefinder on the right of the first laser rangefinder traces the target.
16. The system according to claim 15 , wherein tracing directions of the second laser rangefinder and/or the third laser rangefinder deviate from that of the first laser rangefinder to a predetermined angle.
17. The system according to claim 16 , wherein the predetermined angle is not larger than 45°.
18. The system according to claim 10 , wherein the control exchange distance ranges from 1.5 m to 2.5 m.
19. The system according to claim 10 , further comprising an antenna module, connected to the signal receiving RF module, for receiving the signals from the signal transmitting RF module, wherein the antenna module comprises:
an omnidirectional antenna, receiving signals from the signal transmitting RF module for pairing and stopping operating after pairing is finished; and
at least 3 directional antennas, each receiving signals from a specific range of horizontal angles, wherein a difference between central directional angles of the specific range of horizontal angles for any two directional antennas is a multiple of a fixed angle.
20. The system according to claim 19 , wherein when the at least 3 directional antennas receive no signals from the signal transmitting RF module, the omnidirectional antenna initiates again for pairing.