CN110825119A

CN110825119A - Target following method and system

Info

Publication number: CN110825119A
Application number: CN201810917069.9A
Authority: CN
Inventors: 张俊仁; 邱柏侥; 江明哲; 杨栢林; 杜永明
Original assignee: Gaolin Communication Technology Co Ltd; Fuxin Technology Co Ltd
Current assignee: Gaolin Communication Technology Co Ltd; Fuxin Technology Co Ltd; Trusval Technology Co Ltd
Priority date: 2018-08-13
Filing date: 2018-08-13
Publication date: 2020-02-21

Abstract

The invention discloses a target following method and a target following system. The method comprises the following steps: A. providing a signal transmitting radio frequency module arranged on a target, a signal receiving radio frequency module arranged on a mobile carrier, and at least 3 laser range finders arranged beside the signal receiving radio frequency module; B. calculating an estimated distance and a direction angle; C. driving the mobile carrier to advance toward the target while maintaining the directional angle substantially at 0 degrees; D. repeating steps B and C until the estimated distance is less than a control exchange distance; E. dynamically tracking the target by one of the at least 3 laser rangefinders; driving the mobile carrier to keep the relative distance within a predetermined range and maintain the normal direction substantially towards the target.

Description

Target following method and system

Technical Field

The present invention relates to a target following method and system, and more particularly, to a target following method and system using two different detection techniques.

Background

For short walks carrying items, one may choose to put all items in a backpack or luggage. If the size of the items to be carried is large, a cart or even an electric vehicle may be a good option for saving physical strength. For example, a golf cart may carry all of the equipment that a person needs in a golf course when playing golf. However, cumbersome accessories cannot follow us at any time, and thus, the need for these cumbersome accessories to be intelligent and powered.

In real life, such an invention does exist. For example, the COWAROBOTTM R1 smart luggage provides a luggage following solution for users, which lets people go to do something else. The smart luggage includes a wristband worn on a user's hand, the wristband in wireless communication with the smart luggage. On the telescopic rod, there is a set of laser modules. A laser camera is mounted on the handle of the telescoping pole to receive the reflected laser beam from the environment and further recognize the human image to calculate the position of the person to be followed. Meanwhile, a control module beside the laser camera controls the power wheel module to move when the owner walks. The wristband will alert if the smart luggage becomes lost and its owner cannot be found. The owner may return to the previous location to find the smart luggage. The intelligent luggage case can help people move heavy objects when people travel and shop.

The smart luggage and related applications have found wide acceptance worldwide. In addition to drones, people need to assist devices to move on the ground following them. However, such target following systems that do not include a powered wheel module are too expensive and the tracking effect still needs to be improved.

Disclosure of Invention

Based on this, it is necessary to provide another useful target following system and related applications for the problems that the target following system is too expensive and the tracking effect is not good.

A method of object following, comprising the steps of: A. providing a signal transmitting radio frequency module arranged on a target, a signal receiving radio frequency module arranged on a mobile carrier and at least 3 laser range finders arranged beside the signal receiving radio frequency module; B. calculating an estimated distance between the signal transmitting radio frequency module and the signal receiving radio frequency module and a direction angle between a direction from the signal transmitting radio frequency module to the signal receiving radio frequency module and a normal direction of a front plane on the mobile carrier where the signal receiving radio frequency module is located, by a radio frequency signal transmitted from the signal transmitting radio frequency module and received by the signal receiving radio frequency module, wherein a tracking direction of the first laser range finder is substantially along the normal direction for transmitting and receiving a laser beam; C. driving the mobile carrier toward the target while maintaining the directional angle at substantially 0 degrees; D. repeating steps B and C until the estimated distance is less than a control exchange distance; E. dynamically tracking the target by one of the at least 3 laser rangefinders so that the relative distance between the laser rangefinder and the target can be continuously calculated while calculating the estimated distance and the heading angle; F. driving the moving carrier to keep the relative distance within a predetermined range and maintain the normal direction substantially towards the target.

In one embodiment, the method, further comprising the step between step E and step F: E1. checking whether the relative distance is less than a predetermined percentage of the control exchange distance or whether none of the laser rangefinders track to the target; E2. if any of the events of step E1 occurs, repeating step B and step C; otherwise, executing step F. The predetermined percentage can be 50 percent to 90 percent

According to the present application, the method may further comprise, after step F, the steps of: G. checking whether a difference between the direction angle and a relative angle formed between the normal direction and a line from the first laser range finder to the target falls within a predetermined angle range; H. if the result of step G is yes, repeating step F; and if the result of the step G is negative, repeating the step B and the step C. The predetermined angle range may be + 3% to-3%.

The normal direction substantially towards the target may be maintained by: if a second laser range finder to the left of the first laser range finder tracks the target, then turn the mobile vehicle to the left until the first laser range finder tracks the target, and if a third laser range finder to the right of the first laser range finder tracks the target, then turn the mobile vehicle to the right until the first laser range finder tracks the target. The tracking direction of the second laser range finder and/or the third laser range finder is deviated from the tracking direction of the first laser range finder to a predetermined angle. The predetermined angle is not greater than 45 °. The control exchange distance may be 1.5m to 2.5 m.

An object following system according to the present application comprises: the signal transmitting radio frequency module is arranged on a target to be followed and used for transmitting a radio frequency signal; the signal receiving radio frequency module is arranged on the mobile carrier, is matched with the signal transmitting radio frequency module and is used for receiving the radio frequency signal transmitted by the signal transmitting radio frequency module; at least 3 laser range finders, which are arranged beside the signal receiving radio frequency module and calculate the relative distance between the laser range finders and the target; a controller, signal connected to the signal receiving RF module and the at least 3 laser rangefinders, for calculating an estimated distance between the signal transmitting RF module and the signal receiving RF module and a direction angle between a direction from the signal transmitting RF module to the signal receiving RF module and a normal direction of a front plane of the mobile vehicle where the signal receiving RF module is located by RF signals emitted from the signal transmitting RF module and received by the signal receiving RF module, sending a command to control movement of the mobile vehicle, and dynamically tracking the target by one of the at least 3 laser rangefinders so that the relative distance can be continuously calculated. A tracking direction of the first laser range finder is substantially along the normal direction for emitting and receiving a laser beam; the controller continuously calculates the estimated distance and the direction angle and drives the mobile vehicle to move towards the target to maintain the direction angle substantially at 0 degrees until the estimated distance is shorter than a control swap distance; when the estimated distance is shorter than the control swap distance, the controller still calculates the estimated distance and the direction angle while driving the mobile vehicle to keep the relative distance within a predetermined range and maintain the normal direction substantially toward the target.

In one embodiment, when the estimated distance is found to be shorter than the control swap distance, the controller further checks whether the relative distance is shorter than a predetermined percentage of the control swap distance or whether no laser rangefinder is tracking the target; if any one of the above conditions occurs, the controller drives the mobile vehicle by using the estimated distance and the direction angle. The predetermined percentage may be 50% to 90%.

According to the present application, when the controller drives the moving vehicle using the relative distance and a relative angle, the controller also checks whether a difference between the direction angle and the relative angle falls within a predetermined angle range; the relative angle is formed between the normal direction and a connecting line from the first laser range finder to the target, and if the difference value falls within the predetermined angle range, the moving vehicle is continuously driven at the relative distance and the relative angle; and if the difference value does not fall into the preset angle range, driving the mobile carrier by the estimated distance and the direction angle. The predetermined angle range may be + 3% to-3%.

In one embodiment, the system may further comprise an antenna module connected to the signal receiving rf module for receiving the signal from the signal transmitting rf module, wherein the antenna module comprises: the omnidirectional antenna receives a signal from the signal transmitting radio frequency module for pairing and stops operating after the pairing is finished; at least 3 directional antennas, each directional antenna receiving signals from a particular horizontal angle range, wherein the difference in center directional angles of the particular horizontal angle range for any 2 directional antennas is a multiple of a fixed angle. When the at least 3 directional antennas do not receive the signal from the signal transmitting RF module, the omni-directional antenna can start pairing again.

The method and system for following the target provided by the application utilize two technologies to detect the distance between the target and the mobile carrier. When the detected distance is shorter than a control exchange distance, the distance data from the laser range finder replaces the distance data from the radio frequency module. Thus, relative distance following may be applied to the target. At the same time, the system for following the target can be compactly mounted on any moving carrier, such as a smart boot or golf cart. The overall cost of the target following carrier thus manufactured can be reduced and the traceability can be improved compared to similar products on the market.

Drawings

FIG. 1 is a schematic view of a target following vehicle;

FIG. 2 is a schematic structural diagram of a mobile module;

FIG. 3 is an illustration of the definition of estimated distance and heading angle;

FIG. 4 is a schematic view of an arrangement of laser rangefinders;

FIG. 5 is a schematic view of another arrangement of the laser range finder;

FIG. 6 is an explanatory diagram of the relationship between the control exchange distance, the relative distance, and the estimated distance;

FIG. 7 is a schematic view of an arrangement of antennas;

FIG. 8 is a schematic diagram of a structure of a target device;

FIG. 9 is a flow chart of a target following method;

FIG. 10 is a flow chart of a more specific target following method;

FIG. 11 is a flow chart of another more specific object following method.

Wherein the content of the first and second substances,

10 target following carrier

20 target

100 target end equipment

110 signal transmitting radio frequency module

120 first power module

130 first control unit

140 fixed module

150 alarm unit

200 moving carrier

210 outer casing

211 accommodating space

212 fixing plate

220 moving module

221 wheel set unit

222 motor

223 second control unit

230 second power module

300 target following assembly

310 signal receiving radio frequency module

320 laser range finder

321 first laser range finder

322 second laser rangefinder

323 third laser rangefinder

330 controller

340 antenna module

341 omnidirectional antenna

342 direction antenna

Detailed Description

Referring to fig. 1, an embodiment of an object following vehicle 10 according to the present application is disclosed. The object following vehicle 10 comprises three main parts: target-end device 100, mobile carrier 200, and target-following assembly 300. A detailed description of these components, functions and their interactions is provided below with respect to the drawings.

The target device 100 is used to install on a target to be followed. In application, the target may be a person moving on the ground. The following of the target is realized, so that certain carried articles can correspondingly move along with the target. For example, if the object is a visiting visitor, the object following vehicle 10 may be an intelligent luggage that automatically moves with the visitor. If the target is a golfer, the target following vehicle 10 may also be a golf cart. The target device 100 has a signal transmitting rf module 110, a first power module 120, a first control unit 130 and a fixing module 140. The signal transmitting rf module 110 can emit rf signals. In the present embodiment, the signal transmitting rf module 110 unidirectionally transmits rf signals; in other embodiments, the signal transmitting rf module 110 may be a bi-directional transmission. I.e., the signal transmitting rf module 110 can also receive rf signals.

The first power module 120 is electrically connected to the rf signal transmitting module 110, and can provide power required for operation to any electronic components connected thereto. Because the target end device 100 should be designed as compact as possible so that it does not burden the target to carry, the selection of the first power module 120 should be carefully considered. In practical applications, the first power module 120 is a low-battery secondary battery, such as a lithium battery, that can be charged when the power is depleted or at a low level. For convenience, the first power module 120 may be designed to use a low-power primary battery, such as a mercury battery. The present application is not particularly limited.

The first control unit 130 is electrically connected to the signal transmitting radio frequency module 110 and the first power module 120. The first control unit 130 may take the form of an integrated circuit. The first control unit 130 functions to manage the operation of the signal transmitting rf module 110. The first control unit 130 may be designed to control the power output and recharging of the first power module 120, if possible.

The fixing module 140 is mounted to the tool on the object to be followed. Therefore, it may carry the signal transmitting rf module 110, the first power module 120 and the first control unit 130. In practice, the fixing module 140 may be in the form of a wrist band that is mounted to a moving part of an object, such as a human wrist. The securing module 140 may also be designed as a charm that is attached to a lanyard or mounted in a key ring.

The mobile vehicle 200 is an integral part of the mobile following target, and includes a housing 210, a mobile module 220, and a second power module 230. The housing 210 is used to house carried items, such as clothing purchased by a visitor. Therefore, the housing 210 has a receiving space 211, as shown by the dashed line box in fig. 1. In the present embodiment, the accommodating space 211 is completely closed by the housing 210 and may be opened for use when the housing 210 is opened. In other embodiments, the housing 210 may have several openings, and the receiving space 211 can be connected to the space of the housing 210. A good example of such an application is an intelligent golf cart. The golf equipment may be placed in the accommodation space 211 and the cart body is the housing 210.

The mobile module 220 is responsible for the movement of the mobile carrier 200, is integrated with the housing 210 and can move on the ground according to the received commands. Referring to fig. 2, the moving module 220 may further include a plurality of sub-modules according to the present application. The sub-modules are a wheel set unit 221, a motor 222, and a second control unit 223. The wheel set unit 221 is a component group and has at least 2 wheels that push, stop, and turn the mobile vehicle 220 in a rotating manner. In practice, the wheel set unit 221 may be several non-powered wheels with at least one powered wheel, and in addition, some of the wheels may be controlled to change the direction of their rotational axis, i.e. the direction wheel. The wheel set unit 221 may also be a combination of universal wheels. Of course, in order to improve the off-road performance, the wheel set unit 221 may be a plurality of track wheels around which a track is attached. However, the wheel set unit 221 is not itself powered. Therefore, the motor 222 is coupled to the wheel set unit 221, and outputs power to the wheel set unit 221 to drive the wheel set unit 221. Any type of motor suitable for driving the designed wheel set unit 221 may be used, and the present application is not particularly limited. The number of motors 222 can be more than one to achieve fine directional control or increase speed, if desired.

Like the first control unit 130, the second control unit 223 may be in the form of an integrated circuit electrically connected to the wheel set unit 221 and the motor 222, and can control the operations of the wheel set unit 221 and the motor 222 according to commands received from a controller 330.

The second power module 230 is detachably connected to the housing 210. Because of the detachability, the second power module 230 can be removed from the housing 210 to reduce the overall weight of the mobile vehicle 200 or to perform maintenance if the mobile vehicle 200 only needs to use its carrying function and not the target following function. Similarly, the second power module 230 is used to provide power. Unlike the first power module 120, the second power module 230 must provide a higher amount of power and should be rechargeable. Therefore, the second power module 230 should be a high-capacity secondary battery pack.

The target following assembly 300, which is a key part for performing target following and controlling the movement of the mobile vehicle 200, is mounted on the mobile vehicle 200 and electrically connected to the second power module 230, as shown by the right dashed line in fig. 1. In the present embodiment, one electric wire (right dotted line) connecting the object following assembly 300 and the second power module 230 is embedded in the housing 210; in other embodiments, the wires may be mounted on the surface of the housing 210, i.e., in the receiving space 211 or the external environment. In one embodiment, the target following assembly 300 should be mounted on an outer surface of the housing 210, or embedded in the housing 210 with a portion thereof exposed outward. On the one hand, it reduces the occupancy of the accommodation space 211; on the other hand, the target following assembly 300 can be easily installed or removed for maintenance. The target follower assembly 300 includes three sub-modules: a signal receiving RF module 310, at least 3 laser range finders 320 and the controller 330. The following is a description of these sub-modules.

The signal receiving rf module 310 is selected according to the signal transmitting rf module 110 in the target device 100, so that the signal receiving rf module 310 can be paired with the signal transmitting rf module 110 and can receive the rf signal transmitted from the signal transmitting rf module 110. Similarly, the signal receiving rf module 310 may also transmit and receive rf signals bidirectionally. In one embodiment, the signal receiving RF module 310 and the signal transmitting RF module 110 use 5.8G (802.11a/n/ac) bandwidth. The two radio frequency modules together provide data for calculating the estimated distance and the direction angle.

Referring to fig. 3, for a better understanding, the figure defines the estimated distance De and the direction angle θ. The estimated distance De is defined as the distance between the signal transmitting rf module 110 and the signal receiving rf module 310, and is calculated by the rf signal transmitted from the signal transmitting rf module 110 and received by the signal receiving rf module 310. The estimated distance De is an "estimate" because the rf signal may float when transmitted, resulting in an erroneous calculation of the true distance. The direction angle θ is defined as the angle between the direction from the rf signal transmitter 110 to the rf signal receiver 310 (solid line) and the normal direction N of the front plane of the mobile carrier 200 where the rf signal receiver 310 is located. Here, a fixing plate 212 having a smooth plane is used to mount the signal receiving rf module 310 so as to indicate the normal direction N. In other embodiments, normal direction N may be defined by any plane of any device on signal receiving rf module 310, as long as the plane is not easily changed by external forces or heat. In fact, any technique that can realize the calculation of the estimated distance De and the direction angle θ described above using radio frequency signals can be applied to the present application. A key feature of the present application is to control the distance between the target and the mobile vehicle 200 based on the rf signal and the results of at least 3 laser range finders 320.

Referring to FIG. 4, an arrangement of laser rangefinder 310 is shown. Each laser range finder 320 calculates a precise relative distance Dr between the target 20 and itself by emitting a laser beam that is reflected off of the target 20. The number of laser range finders 320 should be at least 3, such as 3, 4, 5 or more. In one embodiment, the number should be odd, meaning that there will be one central laser range finder 320. In the present embodiment, three laser rangefinders 320 are used for illustration in order to simplify the target following assembly 300. Which are the first laser rangefinder 321, the second laser rangefinder 322 on the left side of the first laser rangefinder 321, and a third laser rangefinder 323 on the right side of the first laser rangefinder 321, respectively. The laser range finder 320 has a laser beam emitter (not shown) and a laser beam receiver (not shown). Taking the first laser range finder 321 as an example, when the emitted laser beam is reflected by the target 20 and then received by the first laser range finder 321, the relative distance Dr is obtained. However, when the emitted laser beam is not reflected (there is no distance data available. it also means that the associated laser rangefinder 320 cannot detect or track the target 20. the second laser rangefinder 322 and the third laser rangefinder 323 are located adjacent to the first laser rangefinder 321. regardless of how many laser rangefinders 320 are used, they should be located adjacent to the RF signal receiving module 310. this is because the references for calculating the distance De and the relative distance Dr should be as close as possible.

Each laser range finder 320 has a tracking direction, which is the direction in which the laser beam is emitted. In the present embodiment, the tracking directions of the three laser range finders 320 are different. The tracking direction of the first laser range finder 321 is 0 deg., pointing upward. In other words, the tracking direction of the first laser range finder 321 is substantially along the normal direction N for emitting and receiving the laser beam. The tracking direction of the second laser range finder 322 is 10 ° counterclockwise. The tracking direction of the third laser range finder 323 is 10 ° clockwise. This means that the tracking direction of the second laser range finder 322 and/or the third laser range finder 323 may be deviated from the tracking direction of the first laser range finder 321 by a predetermined angle. In this example, the predetermined angle is 10 °. In one embodiment, the predetermined angle may be greater but should not be greater than 45 °.

Referring to FIG. 5, in another embodiment, the tracking directions of the three laser range finders 320 are the same. However, the second laser range finder 322 and the third laser range finder 323 are further away from the first laser range finder 321. Such an arrangement of laser rangefinder 320 is also within the scope of the present application. The difference in the arrangement between fig. 4 and 5 is that the arrangement in fig. 4 should be applied to a mobile vehicle 200 with a narrower front, such as a smart trunk, while the arrangement in fig. 4 should be applied to a mobile vehicle 200 with a wider front, such as a golf cart.

The controller 330 is signal-connected to the signal receiving rf module 310 and the at least 3 laser rangefinders 320. Meanwhile, in order to issue a command to control the second control unit 223, they are connected by a connection line (a left dotted line) as shown in fig. 1. Similarly, the connecting wires may be embedded in the housing 210, or may be disposed on the surface of the housing 210. The controller 330 is configured to calculate the estimated distance De and the direction angle θ, issue a command to the second control unit 223 to control the movement of the mobile carrier 200, and dynamically track the target 20 by one of the at least 3 laser rangefinders 320, so as to continuously calculate the relative distance Dr.

The present application utilizes two techniques to obtain the distance between the target and the tracker itself, namely, the technique using the laser range finder 320 and the technique using the signal receiving rf module 310. The controller 330 uses the feedback information from the rf signal receiving module 310 to calculate the estimated distance De and the direction angle θ, so that the absolute position can be identified. At the same time, the controller 330 also uses the results of the at least 3 laser range finders 320 to obtain relative position identification. The latter is more accurate than the former. Thus, having the same reference as the tracker, the relative distance Dr may be used to represent the "true distance" when the target is closer to the controller 330. The estimated distance De is used when the target is far from the controller 330, and the relative distance Dr may be incorrect because there may be many obstacles between the laser range finder 320 and the target. For the switching of the relative distance Dr and the estimated distance De, here, the control exchange distance Dce is defined as a boundary line to which the relative distance Dr and the estimated distance De are applied. In practice, in one embodiment, the exchange distance Dce is controlled to be between 1.5m and 2.5 m. Preferably, the control exchange distance Dce is 2 m.

Referring to fig. 6, the relationship between the control exchange distance Dce, the relative distance Dr, and the estimated distance De is shown. In general, the estimated distance De can be far, ranging from 2m to over 20 m. If the distance between the controller 330 and the target obtained by the signal receiving RF module 310 is shorter than the control exchange distance Dce, the relative distance Dr from the laser range finder 320 is taken as the real distance. Although the distance data from the laser range finder 320 is used, the controller 330 continuously calculates the estimated distance De and the direction angle θ as needed.

The controller 330 drives the mobile carrier 200 to move toward the target such that the distance between the mobile carrier 200 and the target is shortened. Meanwhile, the controller 330 maintains the direction angle θ substantially at 0 degrees until the estimated distance is shorter than the control exchange distance Dce. As described above, when the estimated distance De is shorter than the control exchange distance Dce, the controller 330 still calculates the estimated distance De and the direction angle θ while driving the mobile carrier 200 to keep the relative distance Dr within a predetermined range and maintain the normal direction N substantially toward the target. The predetermined range is set to keep the mobile carrier 200 away from the target to avoid collision, for example, the predetermined range may be 0.5 m. The normal direction N is substantially maintained toward the target by the following method. Please refer back to fig. 4. If the second laser range finder 322 at the left of the first laser range finder 321 tracks the target 20, which means that the normal direction N rotates a little bit clockwise, the normal direction N can be substantially directed to the target 20 by only rotating the mobile carrier 200 to the left until the first laser range finder 321 tracks the target 20. Conversely, if the third laser range finder 323 at the right of the first laser range finder 321 tracks the target 20, which means that the normal direction N rotates a little bit counterclockwise, the normal direction N can be substantially directed to the target 20 again by only turning the mobile carrier 200 to the right until the first laser range finder 321 tracks the target 20.

The frame rate of the laser range finder 320 and the signal receiving rf module 310, i.e. the data acquisition frequency, may be several tens of times per second, for example, 10 times per second. Therefore, when something or someone quickly enters between the object and the controller 330, it is difficult to find the distance between the object and the controller 330. Therefore, some special decision control of the switching distance needs to be designed to solve the above problem. When the estimated distance De is found to be shorter than the control swap distance Dce, the controller 330 can further check whether the relative distance Dce is shorter than a predetermined percentage of the control swap distance De, or no laser rangefinder 320 is tracking the target. This is to check whether someone suddenly breaks in, or the target is lost. If any of the above occurs, the controller 330 drives the mobile carrier 200 using the estimated distance De and the direction angle θ instead of using the relative distance Dr determined by the laser range finder 320. In one embodiment, the predetermined percentage is 50% to 90%. In other words, the sudden change in the relative distance Dce may be up to 1m or 1.8 m. Under another condition, when the controller 330 drives the mobile carrier 200 using the relative distance Dr and a relative angle, the controller 330 also checks whether the difference between the direction angle θ and the relative angle falls within a predetermined angle range. The relative angle is formed between the normal direction N and a line from the first laser range finder 321 to the target 20. If the difference value falls within the predetermined angle range, the mobile carrier 200 is continuously driven at the relative distance Dr and the relative angle. If the difference does not fall within the predetermined angle range, the mobile carrier 200 is driven at the estimated distance De and the direction angle θ. The predetermined angle range should not be set too large, and in one embodiment, the predetermined angle range may be + 3% to-3%.

Referring to fig. 7, the target following assembly 300 may further include an antenna module 340 according to the present application. The target following assembly 300 may be connected to the signal receiving rf module 310 to receive the signal from the signal transmitting rf module 110. The antenna module may include an omni-directional antenna 341 and at least 3 directional antennas 342. The omnidirectional antenna 341 receives a signal from the signal transmitting rf module 110 for pairing, and the omnidirectional antenna 341 stops operating after the pairing is completed. The omnidirectional antenna 341 is used to establish a connection between the signal transmitting rf module 110 and the signal receiving rf module 310. The number of directional antennas 342 is preferably 3, 5 or 7. Each directional antenna 342 may receive signals from a particular horizontal angular range. For example, directional antenna 342, marked by a dot, receives a signal from the top side of fig. 7, where a particular horizontal angular range is represented by two dashed lines. The difference in the center directional angle of the specific horizontal angular range of any 2 directional antennas 342 is a multiple of one fixed angle. In the present embodiment, the center azimuth of a specific horizontal angular range of any directional antenna 342 faces outward along the connection between itself and the omnidirectional antenna 341. The directional angle θ may be determined by the signal received by the directional antenna 342. For example, two directional antennas 342 marked with diagonal lines receive signals from the signal transmitting rf module 110. A more accurate directional angle theta can be obtained by finding the signal strength in the directional antenna 342. The directivity angle theta falling between the center directivity angles of the specific horizontal angle ranges of the 2 directivity antennas 342 is actually closer to the one whose received signal strength is stronger.

Sometimes, if the target moves too fast to follow, i.e. the target is farther away from the receiving rf module 310 where the signal can reach, or there is a noise signal in the environment, the connection between the transmitting rf module 110 and the receiving rf module 310 is interrupted. I.e., no signal from the signal transmitting rf module 110 is received by the at least 3-way antenna 342. If this happens, the omni-directional antenna 341 will initiate pairing again. Thus, the online can be reestablished.

Referring to fig. 8, in another embodiment, the target device 100 may further include an alert unit 150. The warning unit 150 is electrically connected to the first control unit 130 and the first power module 120, and is capable of providing an alarm message. In practical applications, the warning unit 150 may be a buzzer, an LED, a micro-speaker, or a micro-motor. Thus, the alert message may be in the form of a beep, sound, music, light, or vibration. If the directional antenna 342 does not receive the signal from the rf signal transmitting module 110, the controller 330 will send an alarm signal to the alarm unit 150 via the rf signal receiving module 310 and the rf signal transmitting module 110, and then the alarm unit sends out an alarm message.

Referring to fig. 9, a target following method is also provided according to the present application. The first step S01 of the method is to provide a signal emitting rf module mounted on a target, a signal receiving rf module mounted on a mobile carrier, and at least 3 laser range finders beside the signal receiving rf module. The functions of the devices mentioned here are the same as those of the correspondingly named devices mentioned above. Next, the next step S02 is to calculate the estimated distance and direction angle. The definitions of the estimated distance and the direction angle are the same as those disclosed in the previous embodiment and are not repeated. It should be noted that the tracking direction of the first of the at least 3 laser range finders is substantially along the normal direction as disclosed in the previous embodiment for emitting and receiving the laser beam.

The third step S03 is to drive the mobile vehicle to advance toward the target while maintaining the direction angle substantially at 0 degree. In this step, the motion of the mobile carrier towards the target is controlled by the position data. The position data are estimated distance and direction angle. Next, the next step S04 is a repetitive loop process for guiding the mobile vehicle from the calculated position data: repeating steps S02 and S03 until the estimated distance is shorter than a control exchange distance. The control exchange distances described above have been defined identically in the previous embodiments. In practical application, the control exchange distance should be 1.5 m-2.5 m.

As described above, if the distance is shorter than the control exchange distance, the distance between the mobile carrier and the target is determined by the laser range finder. Thus, the next step S05 is to dynamically track the target by one of the at least 3 laser rangefinders, so as to continuously calculate the relative distance between the laser rangefinder and the target, and calculate the estimated distance and the direction angle. Dynamic tracking means that none of the laser rangefinders is assigned to track and find the distance between it and the target. As long as one of the laser rangefinders finds the target, its data can be used until the first laser rangefinder takes charge of the job. The final step S06 of the method is to drive the mobile carrier to keep the relative distance within a predetermined range and to maintain the normal direction substantially facing the target. The object can thus be followed by the mobile carrier.

Referring to fig. 10, there are some unpredictable conditions for the rf module and/or the laser rangefinder that interfere with the distance measurement. Therefore, additional steps are necessary to deal with these problems. Before the data of the laser range finder can be used stably, inspection steps must be taken. For example, there are two additional steps after step S05: checking whether the relative distance is shorter than a predetermined percentage of the control exchange distance or whether none of the laser rangefinders track the target (S05-1) and repeating steps S02 and S03 if any of the events of step S05-1 occurs; otherwise, step S06 is performed (S05-2). Step S05-1 determines whether the relative distance is significantly decreased or whether the laser range finder loses the target originally tracked by the RF module. In other words, it checks whether someone or something suddenly appears between the target and the laser rangefinder or the laser rangefinder fails to catch the target. If step S05-1 occurs, step S05-2 allows the data computed by the radio frequency module to be used to determine the current location of the target. After the target position is determined, the method will continue from step S04. Here, the predetermined percentage should be 50% to 90%.

Referring to fig. 11, in another case, there may be an additional step after step S06. The first step S07 is to check whether the difference between the direction angle and a relative angle formed between the normal direction and a line from the first laser range finder to the target falls within a predetermined angle range. The second step S08 is that if the result of step S07 is yes, step S06 is repeated; if the step S07 is false, the steps S02 and S03 are repeated. Steps S07 and S08 are used to deal with the situation where a person suddenly appears between the target and the laser range finder, resulting in different direction determination by the rf module. In one embodiment, the predetermined angle range is + 3% to-3%.

As with the target following vehicle, the method also provides the same procedure to maintain the normal direction substantially towards the target. The method is achieved by the following steps: if a second laser range finder to the left of the first laser range finder tracks the target, then turn the mobile vehicle to the left until the first laser range finder tracks the target, if a third laser range finder to the right of the first laser range finder tracks the target, then turn the mobile vehicle to the right until the first laser range finder tracks the target. In one embodiment, the tracking direction of the second laser range finder and/or the third laser range finder is offset from the tracking direction of the first laser range finder by a predetermined angle. Similarly, the predetermined angle should not be greater than 45 °.

The technical features of the above embodiments may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above examples only show some embodiments of the present invention, and the description thereof is specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A target following method, comprising the steps of:

A. providing a signal transmitting radio frequency module arranged on a target, a signal receiving radio frequency module arranged on a mobile carrier and at least 3 laser range finders arranged beside the signal receiving radio frequency module;

B. calculating an estimated distance between the signal transmitting radio frequency module and the signal receiving radio frequency module and a direction angle between a direction from the signal transmitting radio frequency module to the signal receiving radio frequency module and a normal direction of a front plane on the mobile carrier where the signal receiving radio frequency module is located, by a radio frequency signal transmitted from the signal transmitting radio frequency module and received by the signal receiving radio frequency module, wherein a tracking direction of the first laser range finder is substantially along the normal direction for transmitting and receiving a laser beam;

C. driving the mobile carrier toward the target while maintaining the directional angle at substantially 0 degrees;

D. repeating steps B and C until the estimated distance is less than a control exchange distance;

E. dynamically tracking the target by one of the at least 3 laser rangefinders so that the relative distance between the laser rangefinder and the target can be continuously calculated while calculating the estimated distance and the heading angle;

F. driving the moving carrier to keep the relative distance within a predetermined range and maintain the normal direction substantially towards the target.

2. The method of claim 1, further comprising, between step E and step F, the steps of:

E1. checking whether the relative distance is less than a predetermined percentage of the control exchange distance or whether none of the laser rangefinders track to the target;

E2. if any of the events of step E1 occurs, repeating step B and step C; otherwise, executing step F.

3. The object following method according to claim 2, characterized in that the predetermined percentage is 50-90%.

4. The object following method according to claim 1, further comprising, after step F, the steps of:

G. checking whether a difference between the direction angle and a relative angle formed between the normal direction and a line from the first laser range finder to the target falls within a predetermined angle range;

H. if the result of step G is yes, repeating step F; and if the result of the step G is negative, repeating the step B and the step C.

5. The object following method according to claim 4, wherein the predetermined angle range is + 3% to-3%.

6. The object following method according to claim 1, characterized in that the normal direction substantially towards the object is maintained by: if a second laser range finder to the left of the first laser range finder tracks the target, then turn the mobile vehicle to the left until the first laser range finder tracks the target, and if a third laser range finder to the right of the first laser range finder tracks the target, then turn the mobile vehicle to the right until the first laser range finder tracks the target.

7. The method of claim 6, wherein the tracking direction of the second laser range finder and/or the third laser range finder is offset from the tracking direction of the first laser range finder by a predetermined angle.

8. The object following method according to claim 7, wherein the predetermined angle is not more than 45 °.

9. The target following method according to claim 1, wherein the control exchange distance is 1.5m to 2.5 m.

10. An object following system, comprising:

the signal transmitting radio frequency module is arranged on a target to be followed and used for transmitting a radio frequency signal;

the signal receiving radio frequency module is arranged on the mobile carrier, is matched with the signal transmitting radio frequency module and is used for receiving the radio frequency signal transmitted by the signal transmitting radio frequency module;

at least 3 laser range finders, which are arranged beside the signal receiving radio frequency module and calculate the relative distance between the laser range finders and the target;

a controller, signal-connected to the signal-receiving RF module and the at least 3 laser rangefinders, for calculating an estimated distance between the signal-transmitting RF module and the signal-receiving RF module and a direction angle between a direction from the signal-transmitting RF module to the signal-receiving RF module and a normal direction of a front plane on the mobile vehicle where the signal-receiving RF module is located, by RF signals emitted from the signal-transmitting RF module and received by the signal-receiving RF module, sending a command to control movement of the mobile vehicle, and dynamically tracking the target by one of the at least 3 laser rangefinders so as to be able to continuously calculate the relative distance,

wherein the tracking direction of the first laser range finder is substantially along the normal direction for emitting and receiving a laser beam; the controller continuously calculates the estimated distance and the direction angle and drives the mobile vehicle to move towards the target to maintain the direction angle substantially at 0 degrees until the estimated distance is shorter than a control swap distance; when the estimated distance is shorter than the control swap distance, the controller still calculates the estimated distance and the direction angle while driving the mobile vehicle to keep the relative distance within a predetermined range and maintain the normal direction substantially toward the target.

11. The target following system of claim 10, wherein when the estimated distance is found to be shorter than the control swap distance, the controller further checks whether the relative distance is shorter than a predetermined percentage of the control swap distance or whether no laser rangefinder is tracking the target; if any one of the above conditions occurs, the controller drives the mobile vehicle by using the estimated distance and the direction angle.

12. The object following system according to claim 11, wherein the predetermined percentage is 50% to 90%.

13. The object following system according to claim 10, wherein when the controller drives the moving vehicle using the relative distance and a relative angle, the controller also checks whether a difference between the direction angle and the relative angle falls within a predetermined angle range; the relative angle is formed between the normal direction and a connecting line from the first laser range finder to the target, and if the difference value falls within the predetermined angle range, the moving vehicle is continuously driven at the relative distance and the relative angle; and if the difference value does not fall into the preset angle range, driving the mobile carrier by the estimated distance and the direction angle.

14. The object following system according to claim 13, wherein the predetermined angular range is + 3% to-3%.

15. The object following system according to claim 10, wherein the normal direction substantially towards the object is maintained by: if a second laser range finder to the left of the first laser range finder tracks the target, then turn the mobile vehicle to the left until the first laser range finder tracks the target, and if a third laser range finder to the right of the first laser range finder tracks the target, then turn the mobile vehicle to the right until the first laser range finder tracks the target.

16. The target following system of claim 15, wherein the tracking direction of the second laser range finder and/or the third laser range finder is offset from the tracking direction of the first laser range finder by a predetermined angle.

17. The target following system of claim 16, wherein the predetermined angle is no greater than 45 °.

18. The target following system of claim 10, wherein the control exchange distance is 1.5m to 2.5 m.

19. The target following system of claim 10, further comprising an antenna module connected to the signal receiving rf module for receiving the signal from the signal transmitting rf module, wherein the antenna module comprises:

the omnidirectional antenna receives a signal from the signal transmitting radio frequency module for pairing and stops operating after the pairing is finished;

at least 3 directional antennas, each directional antenna receiving signals from a particular horizontal angle range, wherein the difference in center directional angles of the particular horizontal angle range for any 2 directional antennas is a multiple of a fixed angle.

20. The object following system of claim 19, wherein the omni-directional antenna initiates pairing again when none of the at least 3 directional antennas receive a signal from the signal transmitting rf module.