Patent Publication Number: US-2023139369-A1

Title: Micro-lidar sensor

Description:
TECHNICAL FIELD 
     The technical field of the present invention relates to a rotational LIDAR sensor. 
     BACKGROUND ART 
     The contents described in this section merely provide background information on the present exemplary embodiment but do not constitute the related art. 
     With the development of robot technology, the utilization of autonomous mobile robots that set and move a route by itself is increasing. In order for an autonomous mobile robot to set a moving path by itself, the autonomous mobile robot should not only be able to recognize the current location and destination and search for a moving path, but also be able to detect and avoid obstacles on the moving path. 
     It is important to accurately detect surrounding environments and a location of the obstacle by means of a LIDAR sensor which is applied to the mobile robot. A volume and height of the LIDAR sensor may be restricted according to a requested design matter.
     (Patent Document 1) Korean Registered Patent Publication No. 10-1878827 (Jul. 10, 2018)   (Patent Document 2) Korean Registered Patent Publication No. 10-1840628 (May 15, 2018)   

     DISCLOSURE 
     Technical Problem 
     Exemplary embodiments of the present invention relate to a rotational scanning LIDAR sensor and a main object of the present invention is to place a plurality of transmitter/receiver groups on an inclined surface of a rotary module and adjust an exposure time and an intensity of light in accordance with a scanning situation through the plurality of transmitter/receiver groups, thereby generating a point cloud having an improved distance measurement accuracy to an object and extracting a relative angle on the basis of a reflective pattern reflected from the object. 
     Other and further objects of the present invention which are not specifically described can be further considered within the scope easily deduced from the following detailed description and the effect. 
     Technical Solution 
     According to an aspect of the present exemplary embodiment, a LIDAR sensor includes: a transmission/reception module which transmits light and receives reflected light; a rotary module which is connected to the transmission/reception module and is rotatable; a connection module which transmits a torque to the rotary module and has the rotary module installed therein; and a fixing module which fixes the connection module thereto and transmits a power to the connection module, and the transmission/reception module analyzes a waveform of the reflected light with one or more frequencies to measure a distance according to a time difference and acquire a point cloud, and a rotary column having a plurality of inclined surfaces is located in a rotation axis position of the rotary module. 
     The transmission/reception module includes: a plurality of transmission/reception groups in which one or more transmitters and one or more receivers are disposed to be spaced apart from each other to be combined; and a first controller which controls an operation of the plurality of transmission/reception groups, and the plurality of transmission/reception groups is installed on the plurality of inclined surfaces, is disposed in a predetermined horizontal direction while being directed to a predetermined vertical angle, and is disposed in consideration of a center of gravity. 
     The first controller controls an exposure time and an intensity of the light in accordance with a reference distance which distinguishes a near field from a far field. 
     The first controller adjusts an exposure time and an intensity of the light based on the remainder obtained by dividing a RPM of the rotary module by a predetermined integer. 
     A filter which blocks light of a predetermined wavelength band is mounted in the receiver. 
     In the receiver, pixel arrangement is formed in a rectangular shape and the rectangle is provided at a predetermined tilting angle to increase a vertical resolution. 
     The transmission/reception module includes a thermometer and the first controller compensates for an error of the measured distance according to a temperature measured by the thermometer based on stored temperature data. 
     The transmission/reception module extracts a relative angle with a reflector based on a reflection pattern according to the intensity of the reflected light by a reflectance of the reflector. 
     The first controller outputs a control command about a center direction of the reflector using the relative angle. 
     The first controller compares the reflective pattern and a stored reference pattern to find a center direction of the reflector in a direction that an error of the difference satisfies a reference range. 
     The reflective pattern has a first reflective area and a second reflective area and the first controller finds a center direction of the reflector in a direction that a size of the first reflective area and a size of the second reflective area become equal. 
     The connection module includes: a second bearing disposed at a lower end of the rotary column; and a slip ring which passes through an imaginary line formed by extending the rotary shaft of the second bearing. 
     The connection module includes a first bearing which is disposed on an upper end of the rotary column and an imaginary line formed by extending the rotation axis of the first bearing matches an imaginary line formed by extending the rotation axis of the second bearing. 
     The LIDAR sensor further includes a sensor cover which has a protrusion structure which is inserted into a recessed space of the upper end of the rotary column and is connected to the fixing module, and the sensor cover transmits or absorbs light of a predetermined wavelength band. 
     The LIDAR sensor further includes a display unit which displays status information of the LIDAR sensor at the upper end of the sensor cover. 
     The connection module includes a first gear disposed at a lower end of the rotary column and a second gear which is disposed in the fixing module to rotate while being engaged with the first gear, the fixing module includes a motor which is disposed on a side surface of the fixing module to rotate the second gear, a rotation axis of the first gear and a rotation axis of the second gear are disposed in parallel, and the rotation axis of the second gear and a rotation axis of the motor match. 
     The rotary module includes: a second controller which is located at a lower end of the rotary module and calculates a rotational speed and a rotation position of the rotary module or the first gear using a first signal collected by the first signal receiver; and a first signal receiver connected to the second controller. 
     The fixing module includes: a third controller which is located at a upper side end of the fixing module and calculates a rotational speed and a rotation position of the motor or a second gear using a second signal collected by a second signal receiver; and a second signal receiver which is connected to the third controller. 
     A plurality of first signal receivers is disposed to be spaced apart from each other, the plurality of first signal receivers compensates for an error of the rotational speed and the rotation position of the rotary module or the first gear according to the result of analyzing the plurality of received first signals. 
     According to another aspect of the present exemplary embodiment, a mobile object, includes: a LIDAR sensor which transmits light, receives reflected light, analyzes a waveform of the reflected light with one or more frequencies to measure a distance according to the time difference, and acquire a point cloud, and a moving device which is implemented to move the moving object based on the distance, and the LIDAR sensor includes: a transmission/reception module which transmits light and receives reflected light; a rotary module which is connected to the transmission/reception module and is rotatable; a connection module which transmits a torque to the rotary module and has the rotary module installed therein; and a fixing module which fixes the connection module thereto and transmits a power to the connection module, and a rotary column having a plurality of inclined surfaces is located in a rotary shaft position of the rotary module. 
     Advantageous Effects 
     As described above, according to the exemplary embodiments of the present invention, a plurality of transmitter/receiver groups located on an inclined surface of the rotary module adjusts an exposure time and an intensity of light in accordance with a scanning situation, thereby generating a point cloud having an improved distance measurement accuracy to an object and extracting a relative angle on the basis of a reflective pattern reflected from the object. 
     Even if the effects are not explicitly mentioned here, the effects described in the following specification which are expected by the technical features of the present disclosure and their potential effects are handled as described in the specification of the present disclosure. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a view illustrating a rotating operation of a moving object and a LIDAR sensor according to exemplary embodiments of the present invention. 
         FIG.  2    is a conceptual view illustrating a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  3    is a block diagram illustrating a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  4    is a view illustrating a state in which a sensor cover is coupled in a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  5    is a view illustrating a state in which a sensor cover is separated from a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  6    is a view illustrating a side surface of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIGS.  7 A and  7 B  are views illustrating a cross-section of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  8    is an exploded view illustrating a sensor cover and a display unit of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  9    is an exploded view illustrating a transmission/reception module, a rotary module, a connection module, and a fixing module of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  10    is a view illustrating a transmission/reception module of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  11    is a view illustrating a pixel arrangement of a receiver of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  12    is a view illustrating a lens of a receiver of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  13    is a view illustrating a gear placement of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIGS.  14 A and  14 B  are views illustrating a first position sensor set of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIGS.  15 A and  15 B  are views illustrating a second position sensor set of a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIGS.  16  to  18    are views illustrating an intensity acquired by a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIGS.  19  to  21    are views illustrating a distance, an intensity, and an angle acquired by a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIGS.  22  and  23    are views illustrating an intensity acquired by a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIGS.  24  to  26    are views illustrating a sensing area sensed by a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  27    is a view illustrating a reflector sensed by a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIG.  28    is a view illustrating a point cloud acquired by a LIDAR sensor according to an exemplary embodiment of the present invention. 
         FIGS.  29  to  31    are views illustrating an intensity and a distance acquired by adjusting a power by a LIDAR sensor according to an exemplary embodiment of the present invention. 
     
    
    
     BEST MODE 
     Hereinafter, in the description of the present disclosure, a detailed description of the related known functions will be omitted if it is determined that the gist of the present disclosure may be unnecessarily blurred as it is obvious to those skilled in the art and some exemplary embodiments of the present disclosure will be described in detail with reference to exemplary drawings. 
       FIG.  1    is a view illustrating a rotating operation of a moving object and a LIDAR sensor according to exemplary embodiments of the present invention and  FIG.  2    is a conceptual view illustrating a LIDAR sensor according to an exemplary embodiment of the present invention. 
     The LIDAR sensor  100  according to the present exemplary embodiment may be applied to a moving object. The LIDAR sensor is applicable to products which require distance measurement, such as flying objects including drones, a moving objects including automobiles, and small home appliances. The moving object includes a LIDAR sensor and a moving device. The moving object includes robot cleaners, logistics robots, toy cars, mobile robots for industrial or military purposes. 
     The LiDAR is a device which transmits a laser signal, measures a returning time of the reflected signal, and measures a distance to a reflector using a speed of light. The laser signal is converted into an electrical signal by a photo diode. The laser signal may have a predetermined wavelength band. 
     The distance measuring device may operate by a time of flight (TOF) manner. According to the time of flight manner, a laser emits a pulsed or square wave signal to measure a time when reflection pulses or square wave signals from objects within a measurement range reach a receiver to measure a distance between an object to be measured and the distance measuring device. 
     The moving device calculates a traveling route based on a distance to the object or detects an obstacle to move the moving object. 
     The LIDAR sensor transmits a light signal and receives a reflected light signal. The LIDAR sensor emits light to the object by a start control signal and receives light which is reflected from the object to convert the light into an electrical signal. The LIDAR sensor outputs the electrical signal during a predetermined detecting time. 
     A controller  210  of the LIDAR sensor converts a signal. The controller is connected to the receiver and a signal amplifier is connected. 
     A light source emits light to the object based on a predetermined sampling period. The sampling period may be set by the controller. The sampling period is a time when the transmitter emits light, the receiver receives reflected light, and the controller converts the light into an electrical signal in accordance with the start control signal. The LIDAR sensor may repeatedly perform this operation in a next sampling period. 
     The receiver receives light reflected from the object to convert the light into an electrical signal. The receiver extracts an intensity of the electrical signal. 
     The controller converts the electrical signal to measure an accurate timing and outputs a stop control signal. 
     The controller converts the electrical signal such that a signal point having a maximum signal magnitude has a predetermined magnitude, adjusts an magnitude of the converted electrical signal, and detect a timing having the predetermined magnitude. The controller converts the electrical signal to generate a stop control signal. 
     The controller receives an electrical signal from the receiver or the amplifier. The received electrical signal, that is, an input signal rises or falls by the reflected light. The controller exactly measures a target timing for the input signal to output the electrical signal. 
     The controller may include one or more time to digital converters which convert the difference of two times into the digital value. The input signal of the time to digital converter may be a pulse shape of the same signal source or may be an edge of other signal source. For example, the LIDAR sensor may calculate the time difference based on a rising edge or a falling edge of the start control signal and a rising edge or a falling edge of the stop control signal. 
     The LIDAR sensor calculates a pulse width based on the rising edge or the falling edge of the stop control signal and adds a factor value which is applied to a function of the pulse width versus walk error to a time of flight which has not been corrected. The LIDAR sensor corrects the time of flight using a pulse width of the reflected signal to calculate the exact time of flight. 
     The mobile robot may collect environment information (2D/3D space information) and odometry information by means of simultaneous localization and mapping (SLAM), adaptive Monte Carlo localization (AMCL), the LIDAR sensor, and the IMU sensor. 
     The LIDAR sensor  100  mounted in the moving object  10  rotates to detect the surrounding environments and the obstacles. The LIDAR sensor  100  may detect the obstacle OBS in a direction where the obstacle is located, by the sensed point cloud data. 
     In order to reduce the size of the LIDAR sensor, all components, for example, the transmitter/receiver module, the rotary module, the connection module, and the fixing module need to be closely combined. 
       FIG.  2    is a conceptual view illustrating a LIDAR sensor according to an exemplary embodiment of the present invention and  FIG.  3    is a block diagram illustrating a LIDAR sensor according to an exemplary embodiment of the present invention. 
     When the transmitter and the receiver are disposed up and down and a rotary plate rotates, the transmitter and the receiver rotate together. The LIDAR sensor adjusts the exposure time and the intensity of the light while rotating to flexibly, dynamically, and accurately measure a distance to the object and the point cloud in a near field and a far field. The LIDAR sensor recognizes a reflective pattern reflected from the object to extract a relative angle with the object and narrow the relative angle to make the reflective pattern and the reference pattern similar. 
     The LIDAR sensor  100  includes a transmission/reception module  200 , a rotary module  300 , a connection module  400 , and a fixing module  500 . 
     The transmission/reception module  200  transmits light and receives reflected light. The transmission/reception module  200  analyzes a waveform of the reflected light with one or more frequencies to measure a distance according to a time difference and acquire a point cloud. The transmission/reception module  200  analyzes a pulse waveform using a plurality of frequencies and extracts the time difference. 
     The rotary module  300  is connected to the transmission/reception module  200  and has a rotatable structure. In the position of a rotation axis of the rotary module, a rotary column having a plurality of inclined surfaces is located. 
     The connection module  400  transmits a torque to the rotary module  300  and the rotary module  300  is installed in the connection module  400 . 
     The connection module  400  is fixed to the fixing module  500  and the fixing module  500  transmits the power and data to the connection module  400 . The power and the data are transmitted to the rotary module  300  and the transmission/reception module  200  via the connection module  400 . 
       FIG.  4    is a view illustrating a state in which a sensor cover is coupled in a LIDAR sensor according to an exemplary embodiment of the present invention.  FIG.  5    is a view illustrating a state in which a sensor cover is separated from a LIDAR sensor according to an exemplary embodiment of the present invention.  FIG.  6    is a view illustrating a side surface of a LIDAR sensor according to an exemplary embodiment of the present invention.  FIG.  7    is a view illustrating a cross-section of a LIDAR sensor according to an exemplary embodiment of the present invention.  FIG.  8    is an exploded view illustrating a sensor cover and a display unit of a LIDAR sensor according to an exemplary embodiment of the present invention.  FIG.  9    is an exploded view illustrating a transmission/reception module, a rotary module, a connection module, and a fixing module of a LIDAR sensor according to an exemplary embodiment of the present invention. 
     The transmission/reception module  200  includes a first controller  210  and a plurality of transmission/reception groups  220  and  225 . 
     In the transmission/reception module, one or more transmitters  230  and one or more receivers  270  are disposed to be spaced apart from each other to be combined. Three transmitters  240 ,  250 , and  260  may be disposed. The first transmitter  240  and the second transmitter  250  are horizontally disposed and the third transmitter  260  may be vertically disposed between the first transmitter  240  and the second transmitter  250 . The transmitters  230  and  230  may include separation films  290  and  290  which are installed to be spaced apart from body tubes  280  and  285  of the receivers  270  and  275  and block the light traveling path. 
     The first controller  210  controls the operations of the plurality of transmission/reception groups  220  and  225 . The first controller  210  may adjust an exposure time and an intensity of the light of the first transmitter  240 , the second transmitter  250 , and the third transmitter  260 . A reference distance which distinguishes a near field from a far field is considered and a remainder obtained by dividing an RPM of the rotary module by a predetermined integer may be considered. 
     The plurality of transmission/reception groups  220  and  225  is installed on a plurality of inclined surfaces  312  and  314 . The plurality of transmission/reception groups  220  and  225  is directed to a predetermined vertical angle. The plurality of transmission/reception groups  220  and  225  is disposed in a predetermined horizontal direction and is disposed in consideration of a center of gravity. 
     The rotary module  300  may include a rotary column  310 , a column assembly  315 , a second controller  320 , and a first position sensor set  330 . The first position sensor set  330  may include a first signal transmitter  334  and a first signal receiver  332 . For example, the first position sensor set  330  may be implemented by a magnet and a hall senor based on a magnet signal. The first position sensor set  330  may be implemented by a protruding structure which passes between photo interrupters and the photo interrupters. The first signal is a signal acquired by the hall sensor or the photo interrupter in accordance with the rotation of the rotary module. The first signal transmitter  334  and the first signal receiver  332  may be installed in the fixing module and in the second controller, respectively. For example, the hall sensor or the photo interrupter may be connected to the second controller and the magnet or the protruding structure may be connected to the inside of the fixing module. The magnet or the protruding structure may be located to be closer to a second gear  450  or the magnet or the protruding structure may be located to be far from the second gear or located in a different direction therefrom. The second controller  320  calculates a rotation speed and a rotation position of the rotary module or the first gear  440  using a first signal collected by the first signal receiver  334 . The second controller  320  may transmit the calculated data through the connection module  400 . 
     The connection module  400  includes a second bearing  420  and a slip ring  430 . The connection module  400  may include a first bearing  410  or may not include the first bearing as needed. The first bearing  410  may be disposed at an upper end of the rotary column  310 . The second bearing  420  may be disposed at a lower end of the rotary column  310 . The slip ring  430  is located in a position passing an imaginary line obtained by extending a rotation axis of the second bearing. An imaginary line obtained by extending the rotation axis of the first bearing  410  and the imaginary line obtained by extending the rotation axis of the second bearing  420  may match. 
     The connection module  400  includes a first gear  440  and a second gear  450 . The first gear  440  may be disposed at a lower end of the rotary column or close to the rotary column. The second gear  450  is disposed in the fixing module to rotate while being engaged with the first gear. A rotation axis of the first gear  440  and a rotation axis of the second gear  450  may be disposed to be parallel. A ratio of the first gear  440  and the second gear  450  may be set to M:N. 
     The first gear  440  has a hole. The first position sensor set  330  may operate by means of a hole of the rotating first gear. The first position sensor set  330  may operate by means of a structure which is attached onto a surface of the first gear which rotates without using a hole. The first position sensor set  330  may operate by means of a structure which is attached onto the other component without using the rotating first gear. 
     The fixing module  500  includes a motor  510  which rotates the second gear  450  on a side surface of the fixing module  500 . A rotation axis of the second gear  450  and a rotation axis of the motor  510  may match. 
     The fixing module  500  may include the third controller  520  and a second position sensor set  530 . The second position sensor set  530  may include a second signal transmitter  534  and a second signal receiver  532 . For example, the second position sensor set  530  may be implemented by a magnet and a hall senor based on a magnet signal. The second position sensor set  530  may be implemented by a protruding structure which passes between photo interrupters and the photo interrupters. The second signal is a signal acquired by the hall sensor or the photo interrupter in accordance with the rotation of the second gear. The second signal transmitter  534  and the second signal receiver  532  may be installed in the second gear and in the third controller, respectively. For example, the hall sensor or the photo interrupter may be connected to the third controller and the magnet or the protruding structure may be connected to the gear. The third controller  520  calculates a rotation speed and a rotation position of the module or the second gear using a second signal collected by the second signal receiver  532 . The third controller  520  may transmit the calculated data through the connection module  400 . 
     The LIDAR sensor  100  may include a sensor cover  600 . The sensor cover  600  is connected to the fixing module with a protrusion structure which may be inserted into a dented space of the upper end of the rotary column. In a state in which the protruding structure is inserted, a non-contact state between the protrusion structure and the rotary column may be maintained with a short distance. When a first bearing is located in the dented space of the upper end of the rotary column, the protruding structure may be inserted into the center of the first bearing. The sensor cover  600  may be formed to have a structure which covers the third controller. The sensor cover  600  may transmit or absorb light with a predetermined wavelength band. 
     The LIDAR sensor  100  may include a display unit  700  which displays state information of the LIDAR sensor at an upper end of the sensor cover. The display unit  700  may include a power cable  710 , a display light source  720 , a light source separation wall  730 , and multi-layered assemblies  740 ,  750 , and  760 . 
       FIG.  10    is a view illustrating a transmission/reception module of a LIDAR sensor according to an exemplary embodiment of the present invention. 
     The transmitter may be implemented by SiPM, IrED, VCSEL, a low power laser. The transmitter forms light emitted through a beam forming unit in a line beam type. 
     The transmitter and the receiver are disposed up and down. When a rotation plate rotates, the transmitter and the receiver rotate together. A plurality of transmitter and receiver sets may be installed. The controller which is connected to the receiver may be individually implemented for every transmitter and receiver set or one controller may control the transmitter and receiver set. 
     The transmitter and receiver sets may be installed at the same angle or at different angles. The angle may be set in various forms depending on the design specification. 
     For example, two sets  220  and  215  are equally disposed in azimuth, one set of two sets is installed to be directed to an elevation angle of 15 degrees and the other one is installed to be directed to an elevation angle of −15 degrees. 
     For example, three sets are equally disposed in azimuth and are installed to be directed to a horizontal plane with respect to an elevation angle of 0 degree. Among three sets, one set is directed to the elevation angle of 15 degrees and the other one is installed to be directed to the elevation angle of −15 degrees. 
       FIG.  11    is a view illustrating a pixel arrangement of a receiver of a LIDAR sensor according to an exemplary embodiment of the present invention.  FIG.  12    is a view illustrating a lens of a receiver of a LIDAR sensor according to an exemplary embodiment of the present invention. 
     The receiver receives light reflected from the object to measure a distance to the object. The receiver may be implemented by a ToF camera. The ToF camera includes a camera lens and a ToF array. The ToF array outputs an intensity. 
     A filter which blocks light of a predetermined wavelength band may be mounted in the receiver. 
     In the receiver, the pixel arrangement is formed in a rectangle shape and the rectangle is installed at a predetermined tilting angle to increase a vertical resolution. 
     The transmission/reception module may include a thermometer. The thermometer may be installed in the inside or the outside of the transmission/reception module. The thermometer may be located in other position of the LIDAR sensor. The first controller may compensate for an error of a measured distance according to a temperature measured by the thermometer based on stored temperature data. 
       FIG.  13    is a view illustrating a gear placement of a LIDAR sensor according to an exemplary embodiment of the present invention,  FIG.  14    is a view illustrating a first position sensor set of a LIDAR sensor according to an exemplary embodiment of the present invention, and  FIG.  15    is a view illustrating a second position sensor set of a LIDAR sensor according to an exemplary embodiment of the present invention, and 
     The connection module may include a first gear  440  disposed at a lower end of the rotary column and a second gear  450  which is disposed in the fixing module to rotate while being engaged with the first gear. The gear may be replaced with a belt. 
     The fixing module includes a motor which is disposed on a side surface of the fixing module to rotate the second gear, a rotation axis of the first gear and a rotation axis of the second gear are disposed in parallel, and the rotation axis of the second gear and a rotation axis of the motor match. 
     The rotary module may include a first position sensor set including a first signal transmitter and a first signal receiver. The rotary module may include a second controller which calculates a rotation speed and a rotation position of the rotary module or the first gear using the first signal collected by the first signal receiver. 
     The fixing module may include a second position sensor set including a second signal transmitter and a second signal receiver. The fixing module may include a third controller which calculates a rotation speed and a rotation position of the motor or the second gear using the second signal collected by the second signal receiver. 
     The first signal receiver calculates an angle using a previous rotation period so that when the period varies due to the friction or control, there may be an error in rotation recognizing information. 
     A plurality of first signal receivers is provided and is disposed to be spaced apart from each other. When the plurality of first signal receivers is too close, the plurality of first signal receivers is recognized as one so that the plurality of first signal receivers is spaced apart from each other with a predetermined distance. The plurality of first signal receivers may compensate for an error of the rotation speed and the rotation position of the rotary module or the first gear in accordance with a result of analyzing the plurality of first signal. The signal acquired by the plurality of first signal receives is statistically processed or partially selected in accordance with a result obtained by comparing with a predetermined set state data 
       FIGS.  16  to  18    are views illustrating an intensity acquired by a LIDAR sensor according to an exemplary embodiment of the present invention,  FIGS.  19  to  21    are views illustrating a distance, an intensity, and an angle acquired by a LIDAR sensor according to an exemplary embodiment of the present invention, and  FIGS.  22  and  23    are views illustrating an intensity acquired by a LIDAR sensor according to an exemplary embodiment of the present invention. 
     In  FIG.  16   , a reflector having a low reflectance is located in positions 2.0 m ( 1610 ), 1.5 m ( 1620 ), 1.0 m ( 1630 ), 0.5 m ( 1640 ), 0.3 ( 1650 ) and an optical signal amplitude acquired by seeing the reflector from the front is illustrated. It is understood that the shorter the distance, the larger the circle in a left area. 
     In  FIG.  17   , a reflector having a high reflectance is located in positions 2.0 m ( 1710 ), 1.5 m ( 1720 ), 1.0 m ( 1730 ), 0.5 m ( 1740 ), 0.3 ( 1750 ) and an optical signal amplitude acquired by seeing the reflector from the front is illustrated. It is understood that the shorter the distance, the larger the circle in a left area. 
       FIG.  18    illustrates an optical signal amplitude obtained by placing a reflector having a reflective pattern area in a near field  1810  and a far field  1820 . By doing this, the reflection areas  31  and  32  may be identified. 
     The first controller may control the exposure time and the intensity of the light according to the reference distance which distinguishes the near field from the far field. The first controller may adjust the exposure time and the intensity of the light with respect to the remainder obtained by dividing the RPM of the rotary module by a predetermined integer. 
     Referring to  FIGS.  19  to  21   , the LIDAR sensor extracts a relative angle with respect to the object (reflector) at the center to follow a center line only using the angle, excluding the distance value. 
     The transmission/reception module extracts a relative angle with the reflector based on a reflective pattern according to the intensity of the reflected light, by a reflectance of the reflector. 
     The first controller outputs a control command with regard to a center direction of the reflector using the relative angle. The first controller compares the reflective pattern and the stored reference pattern to find a center direction of the reflector in a direction that an error of the difference satisfies a reference range. The reflective pattern includes a first reflection area and a second reflection area and the first controller may find the center direction of the reflector such that a size of the first reflection area and a size of the second reflection area become the same. 
     Referring to  FIG.  22   , when the LIDAR sensor is offset in a side direction (Y-axis), with respect to the reflector located in a middle field  2210  and a near field  2220 , a reflective pattern which is different from the reflective pattern may be obtained. 
     When the LIDAR sensor moves to the front of the reflector, it is found that the left level is the same as the right level, like the middle field  2230 . The LIDAR may move to the front to track without calculating a relative position based on the reflective pattern. In the far field  2240 , it is difficult to calculate the offset at the left side and the right side, so that the moving operation in a corresponding direction is performed. It moves in the corresponding direction until it recognizes the reference pattern within the error range, such as a prominent line. 
     A principle of removing an outlier will be described with reference to  FIG.  23   . 
     In a situation  2310  in which a search target is 1.3 m ahead and a very large bright brown box is placed 1.2 m to the left, an optical signal amplitude is not sufficiently high. 
     In a situation  2320  in which a search target is 1.3 m ahead and a very large white box is placed 0.2 m to the left, an optical signal amplitude is not sufficiently high. 
     In a situation  2330  in which a search target is 1.3 m ahead and an aluminum panel which is similar to the docking station is placed 0.4 m to the left, an optical signal amplitude is not sufficiently high. 
     In a situation  2340  in which a search target is 1.3 m ahead and an aluminum panel which is similar to the docking station is placed 0.2 m to the left, a sufficiently high optical signal amplitude is maintained. However, in a near field situation, a left/right auxiliary lines are not seen. That is, the reflective pattern corresponding to the reference pattern needs to be recognized with an appropriate level of optical signal amplitude. 
       FIGS.  24  to  26    are views illustrating a sensing area sensed by a LIDAR sensor according to an exemplary embodiment of the present invention. 
     Sensing areas  2410  and  2420  with respect to the docking station have a rhombus shape so that the width increases to a predetermined distance and then narrows as the distance increases. In order to increase the sensing range, the reflector is changed. 
       FIG.  25    illustrates a docking process under the assumption that wall information (angle) is not known. 
     As illustrated in  FIG.  26   , if the object is at the outside of the sensing area, when the object randomly moves and then enters the sensing area, the object is tracked. 
       FIG.  27    is a view illustrating a reflector sensed by a LIDAR sensor according to an exemplary embodiment of the present invention. In the reflector  20 , a non-reflective pattern area  23  is formed at the center and reflective patterns  21  and  22  are partially formed at the left and right. 
     The LIDAR sensor compares the reflector pattern which is obtained by being reflected from the reflective pattern area and the reference pattern or compares the reflection area sets of the reflective pattern to extract a relative angle. 
       FIG.  28    is a view illustrating a point cloud acquired by a LIDAR sensor according to an exemplary embodiment of the present invention and  FIGS.  29  to  31    are views illustrating an intensity and a distance acquired by adjusting a power by a LIDAR sensor according to an exemplary embodiment of the present invention. 
     Referring to  FIG.  28   , point clouds which are a quadrangular shape and obtained at shutter speeds of 6 msec ( 2810 ), 4 msec ( 2820 ), 2 msec ( 2830 ), and 0.4 msec ( 2840 ) are illustrated. 
     When the intensity or the power of the light is high in the near field, it is difficult to recognize the distance and the scan performance varies depending on how to set a period for a near-field scan and a far-field scan during the rotation. 
     The first controller may control the exposure time and the intensity of the light according to the reference distance which distinguishes the near field from the far field. For example, in the near field scan mode, the exposure time and the intensity may be reduced more than the far field scan mode. 
     The first controller may adjust the exposure time and the intensity of the light with respect to the remainder obtained by dividing the RPM of the rotary module by a predetermined integer. For example, when the RPM is an odd number, the near field scan mode may be set and when the RPM is an even number, the far field scan mode may be set. 
     A plurality of components included in the LIDAR sensor is combined to each other to be implemented by at least one module. The components are connected to a communication path which connects a software module or a hardware module in the apparatus to organically operate between the components. The components communicate with each other using one or more communication buses or signal lines. 
     The LIDAR sensor and the moving object may be implemented in a logic circuit by hardware, firm ware, software, or a combination thereof or may be implemented using a general purpose or special purpose computer. The apparatus may be implemented using hardwired device, field programmable gate array (FPGA) or application specific integrated circuit (ASIC). Further, the apparatus may be implemented by a system on chip (SoC) including one or more processors and a controller. 
     The LIDAR sensor and the moving object may be mounted in a computing device provided with a hardware element as a software, a hardware, or a combination thereof. The computing device may refer to various devices including all or some of a communication device for communicating with various devices and wired/wireless communication networks such as a communication modem, a memory which stores data for executing programs, and a microprocessor which executes programs to perform operations and commands. 
     The operation according to the exemplary embodiment of the present disclosure may be implemented as a program instruction which may be executed by various computers to be recorded in a computer readable medium. The computer readable medium indicates an arbitrary medium which participates to provide a command to a processor for execution. The computer readable medium may include solely a program command, a data file, and a data structure or a combination thereof. For example, the computer readable medium may include a magnetic medium, an optical recording medium, and a memory. The computer program may be distributed on a networked computer system so that the computer readable code may be stored and executed in a distributed manner. Functional programs, codes, and code segments for implementing the present embodiment may be easily inferred by programmers in the art to which this embodiment belongs. 
     The present embodiments are provided to explain the technical spirit of the present embodiment and the scope of the technical spirit of the present embodiment is not limited by these embodiments. The protection scope of the present embodiments should be interpreted based on the following appended claims and it should be appreciated that all technical spirits included within a range equivalent thereto are included in the protection scope of the present embodiments.