An indoor area positioning system and method for mobile robots

Abstract

This invention discloses an indoor area positioning system and method for a mobile robot. After an RFID detector detects an RFID tag on the robot, it sends a global reset command, resetting the local clocks of all LED nodes in the LED matrix and activating the area indicator lights. The photoelectric receiver on the robot detects the frequency of the area light signals, queries a frequency mapping table to obtain the current area number, and sends a signal to the corresponding area's LED matrix controller to control the operation of that group of LEDs. The network coordinator continuously sends synchronization signals to control the exposure of the linear CCD sensor and the blinking of the LEDs. When an LED is detected in the field of view of the linear CCD camera on the robot, its address mapping table is queried. Based on the LED's position in the world coordinate system and the sensor coordinate system, the transformation matrix between the two coordinate systems—that is, the sensor's position—is calculated, and thus the robot's position is determined. This invention reduces the range of LED cyclic blinking from global to local, decreasing the time of each LED matrix cycle and increasing the positioning frequency.

Description

Technical Field

[0001] This invention relates to the field of robot positioning, and more specifically to a method and system for positioning mobile robots in indoor areas. Background Technology

[0002] Indoor positioning refers to locating a target within an indoor environment. It can be applied to indoor navigation, security monitoring, smart homes, and other fields. Traditional indoor positioning solutions mainly include technologies based on wireless signals, voiceprints, and cameras. However, these solutions have limitations in practical applications, such as low accuracy, poor real-time performance, and susceptibility to interference. Therefore, developing a high-precision, reliable, and practical indoor positioning solution has always been a popular research direction.

[0003] Currently, various indoor positioning technologies have been applied in commercial scenarios and personal life. Common indoor positioning solutions include those based on Wi-Fi, Bluetooth, voiceprint, and cameras. Among them, Wi-Fi-based indoor positioning solutions utilize Wi-Fi signal strength for positioning, resulting in relatively low accuracy, only reaching the level of a few meters; Bluetooth positioning solutions require the deployment of a large number of Bluetooth beacons in the scene, leading to high costs; voiceprint positioning solutions have certain requirements regarding environmental noise and user accents, posing challenges in practical applications; while camera-based positioning solutions can achieve high accuracy and coverage, but they present privacy and security issues and are susceptible to interference from factors such as lighting conditions. Summary of the Invention

[0004] To address the problems and shortcomings of existing technologies, this invention provides a robot indoor positioning method based on the concept of regional positioning. By employing a CCD sensor for positioning, the positioning frequency can be increased, and it is unaffected by the size of the indoor environment. Compared to traditional high-precision optical positioning systems, it can achieve a higher positioning frequency in large scenes, effectively improving the accuracy and reliability of indoor positioning.

[0005] The technical solution adopted in this invention is as follows:

[0006] On the one hand, the present invention provides an indoor area positioning system for a mobile robot, characterized in that it includes a mobile robot body, a network coordinator, an LED matrix set in the indoor environment, and an RFID reader set at the entrance of the indoor environment.

[0007] The mobile robot body is equipped with RFID tags, linear CCD sensors, IMU sensors, robot controllers, and photoelectric receivers;

[0008] The LED matrix includes LED lights, area signal lights, and an LED matrix controller. The LED matrix controller is placed in the environment, with one controller in each area. Each LED controller has a unique ID.

[0009] The RFID reader and RFID tag work together to detect whether the robot has entered the room;

[0010] The area signal lights are used to send light signals of different frequencies;

[0011] The photoelectric receiver is used to receive light signals of different frequencies and determine the current area code of the mobile robot body based on the frequency of the received light signals.

[0012] The corresponding LED matrix controller is used to reset the local clock of all LEDs within the range and activate the corresponding LEDs after receiving a synchronization signal;

[0013] The network coordinator is used to send synchronization signals to the linear CCD sensor and the LED matrix;

[0014] The linear CCD sensor is used to calculate the three-dimensional coordinates of the LED in the upper field of view;

[0015] The robot microcomputer is used to calculate the robot's pose based on the coordinates of the LED in the world coordinate system and the sensor coordinate system.

[0016] The IMU sensor is used to calibrate the robot pose of the overlapping portions where adjacent regions intersect.

[0017] Preferably, the RFID reader is placed at the location that the mobile robot body needs to pass through to enter the indoor area, and the sensing range of the RFID reader is 1m, covering the indoor entrance area.

[0018] Preferably, the photoelectric receiver and the area signal light are used to achieve area positioning. The photoelectric receiver uses a photodiode, and the area signal light uses an LED.

[0019] Preferably, the LED matrix adopts a time address structure, in which each LED in the matrix is ​​assigned a corresponding time address. A single synchronization signal is used to synchronously trigger the LED node and the linear CCD sensor through a combination of a local clock and a wireless chip on the LED node.

[0020] Preferably, the linear CCD sensor consists of three CCD cameras arranged in a Y-shape, corresponding lens groups, control and data processing units. A light spot on a plane in space is refracted by the lens group and forms an image point on the linear CCD. The three linear CCDs can determine three planes, and the intersection of the planes is the position of the photoelectric sensor.

[0021] On the other hand, the present invention also provides a method for indoor area positioning of a mobile robot, characterized by comprising the following steps:

[0022] S1. Install multiple zone traffic lights and RFID readers indoors.

[0023] S2. When the mobile robot enters the room, the RFID reader is triggered by the RFID tag on the mobile robot and sends a global reset command to the network coordinator.

[0024] S3. The network coordinator broadcasts the instruction to the LED matrix controllers worldwide to activate all area traffic lights globally and reset the local clock of the LED lights in each area;

[0025] S4: The photoelectric receiver on the mobile robot detects the frequency in the light signal of the area. After the robot controller queries the frequency mapping table to obtain the area number, it sends a control command to the LED matrix controller of the corresponding area to activate the LED matrix in the area. The LED matrix then cycles to light up all the LED nodes in it.

[0026] S5. The LED matrix controller resets the clock of all LED nodes after each cycle; the network coordinator sends synchronization messages to the LED nodes and the linear CCD at the same time to control the exposure of the linear CCD sensor.

[0027] S6. The linear CCD sensor detects the LED light signal. Based on the coordinates of three points in space in two coordinate systems, the transformation matrix between the two coordinate systems is calculated, which is the position of the sensor coordinate system. Then, the pose of the robot in the world coordinate system is obtained.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The indoor positioning method based on optical sensors of this invention has a positioning accuracy at the mm level, which is higher than that of wireless and vision-based positioning methods.

[0030] 2. By reducing the range of each LED flashing cycle from the global to the local, the positioning frequency can be increased several times.

[0031] 3. Most existing positioning technologies can only calculate three-dimensional coordinates. The positioning technology proposed in this invention can calculate the robot's orientation in addition to three-dimensional coordinates, which can facilitate more precise attitude control of the robot. Attached Figure Description

[0032] Figure 1 System block diagram of the indoor area positioning system provided in the embodiments of this application

[0033] Figure 2 An indoor LED matrix layout diagram provided for an embodiment of this application;

[0034] Figure 3 A schematic diagram of the mobile robot provided in the embodiments of this application.

[0035] Figure 4 Flowchart of the indoor positioning method based on region division provided in the embodiments of this application Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0037] Please refer to Figure 1 It showcases the system framework of the entire indoor area positioning system, which includes RFID detection devices, RFID tags, linear CCD sensors, photoelectric receivers, IMU sensors, LED matrix, area signal lights, network coordinator, and mobile robots.

[0038] After receiving the regional light signal, the robot looks up the frequency mapping table and sends control commands to the LED matrix controller. The LED matrix controller activates the LED matrix in the corresponding region and resets the local clock of each LED node within the matrix. The linear CCD sensor on the vehicle resolves the coordinates of the LEDs in the sensor coordinate system within the field of view and sends them to the robot control module. The robot control module then queries the current world coordinates of the LEDs. The robot obtains the coordinates of three pairs of points in space and solves for the transformation matrix between the two coordinate systems.

[0039] The light spectrum ranges from 1K to 1M, which differs significantly from the spectrum of the LED matrix, enabling the photoelectric receiver to accurately identify each frequency. This invention also includes a frequency mapping table to map the frequencies of the area signal lights to their corresponding area numbers.

[0040] Please refer to Figure 2This exhibit demonstrates the layout of an LED matrix and zone traffic lights within an indoor space. The LED matrix is ​​an N*M size LED array. The indoor space is divided into several zones, each numbered, and all LEDs within a zone form an LED matrix. A zone traffic light is placed at the geometric center of each zone, with a transmission frequency between 1kHz and 1MHz. Each zone traffic light is assigned a different frequency. A frequency mapping table is established based on the zone number and assigned frequency. An RFID detection device is placed at the room entrance to detect whether a mobile robot has entered the room and to trigger a reset signal for the crystal oscillator clock of the global LED group controller. Upon receiving a control command, the LED matrix controller activates the LED matrix and resets the local clock of each LED node within the matrix. The global LED array is divided into several zones according to the size of the indoor scene, each zone being an N*M size LED matrix. Each LED matrix contains a matrix controller, which controls the frequency and on / off status of the zone traffic lights and sends synchronization signals to the LED nodes within the matrix. The local clock of each LED node wakes up a wireless chip at the corresponding time based on its time address; upon receiving the synchronization signal, the wireless chip illuminates the LED. Each LED in the LED matrix is ​​coded, and its position in the world coordinate system is measured in advance using a high-precision measuring device (such as a laser tracker). An address mapping table is established to map the LED numbers to their positions in the world coordinate system. Based on the coordinates of three pairs of points in different coordinate systems, the transformation matrix between the two coordinate systems is calculated, and then the robot's pose is determined.

[0041] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the mobile robot's components. The RFID tag, photoelectric receiver, and linear CCD sensor are all positioned on top of the robot's main body. The linear CCD sensor's field of view faces directly upwards, while the IMU sensor is mounted at the robot's center of gravity; this position minimizes errors caused by robot movement. The linear CCD sensor measures the position of LED nodes within its field of view. The network coordinator simultaneously sends synchronization signals to both the matrix controller and the linear CCD sensor, ensuring that the exposure time of the linear CCD is synchronized with the LED illumination time.

[0042] Please refer to Figure 4 , Figure 4 The workflow of the entire system is briefly described, and the detailed steps of the entire system operation are as follows:

[0043] Step 1: The mobile robot enters the building. The RFID detection device at the entrance is triggered by the RFID tag on the robot and sends a global reset command to the network coordinator. The network coordinator then broadcasts this command to all LED matrix controllers globally. This command performs two operations: activates all area traffic lights globally; and resets the local clock of the LED matrix controller in each area.

[0044] Step 2: The photoelectric receiver on the mobile robot detects the frequency of the light signal in the area, where the emission frequency of the area's signal lights is above 1kHz. After the robot control module queries the frequency mapping table to obtain the area number, it sends a control command to the corresponding area's LED matrix controller to activate the LED matrix within that area. The LED matrix then cyclically illuminates all its LED nodes.

[0045] Step 3: Each LED in the LED matrix is ​​assigned a corresponding address. Each LED node maintains a local clock, which wakes up the node's wireless chip at the beginning of each time address to receive a synchronization message. At other times, the node's wireless chip remains in sleep mode to extend battery life. The LED matrix controller resets the clocks of all LED nodes after each cycle. The network coordinator sends synchronization messages to the LED nodes and simultaneously sends synchronization messages to the linear CCD sensor to control its exposure.

[0046] Step 4: The LEDs in the field of view of the linear CCD sensor form three image points u1, u2, and u3 on the three linear CCDs in the sensor. The positions of the LEDs in the coordinate system of the linear CCD sensor are (X... S ,Y S Z S ),(X S ,Y S Z S The following relationship exists between the image point u and the image point u:

[0047]

[0048] Among them l [i][j] It is a linear CCD camera C i Projection matrix L i The parameters, projection matrix L i The definition of is:

[0049]

[0050] Where f is the focal length of the linear CCD camera, and u0 is the pixel origin coordinate of the linear CCD. It is the transformation matrix between the linear CCD camera coordinate system C and the sensor coordinate system S.

[0051] The position of the LED in the sensor coordinate system can be calculated using the above formula. Each LED has a working cycle of 30ms, with the LED lit for 1ms within that cycle and remaining off the rest of the time. The mobile robot continuously acquires data from three LED points in its field of view. Based on the coordinates of these three points in two coordinate systems, the transformation matrix between the two coordinate systems is calculated, which represents the position in the sensor coordinate system. Since the transformation matrix between the sensor and robot coordinate systems is known, the robot's pose in the world coordinate system can then be obtained.

[0052] Step 5: Since the illumination range of each area's traffic light is not a regular square, to ensure global coverage, the boundaries of two adjacent areas will partially overlap. When the robot moves to the boundary between two adjacent areas, the photoelectric converter will simultaneously receive signals from the traffic lights in both areas. At this time, the robot controller will read the IMU's positioning data, and after the robot leaves the overlapping area, it will send a shutdown command to the LED controller of the original area. Because the overlapping area is relatively small, the cumulative error of the IMU during this period can be ignored, providing accurate robot pose estimation.

[0053] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Those skilled in the art can make simple modifications or equivalent substitutions to the technical solution of the present invention, without departing from the essence and scope of the present invention.

Claims

1. An indoor area positioning system for a mobile robot, characterized in that, It includes the mobile robot body, network coordinator, LED matrix installed in the indoor environment, and RFID reader installed at the entrance of the indoor environment; The mobile robot body is equipped with RFID tags, linear CCD sensors, IMU sensors, robot controllers, and photoelectric receivers; The LED matrix includes LED lights, area signal lights, and an LED matrix controller. The LED matrix controller is placed in the environment, with one controller in each area. Each LED controller has a unique ID. The RFID reader and RFID tag work together to detect whether the robot has entered the room; The area signal lights are used to send light signals of different frequencies; The photoelectric receiver is used to receive light signals of different frequencies and determine the current area code of the mobile robot body based on the frequency of the received light signals. The corresponding LED matrix controller is used to reset the local clock of all LEDs within the range and activate the corresponding LEDs after receiving a synchronization signal; The network coordinator is used to send synchronization signals to the linear CCD sensor and the LED matrix; The linear CCD sensor is used to calculate the three-dimensional coordinates of the LED in the upper field of view; The robot controller is used to calculate the robot's pose based on the coordinates of the LED in the world coordinate system and the sensor coordinate system. The IMU sensor is used to calibrate the robot pose of the overlapping portions where adjacent regions intersect.

2. The indoor area positioning system for a mobile robot according to claim 1, characterized in that, The RFID reader is placed at the location that the mobile robot needs to pass through to enter the indoor area. The sensing range of the RFID reader is 1m, covering the indoor entrance area.

3. The indoor area positioning system for a mobile robot according to claim 1, characterized in that, The photoelectric receiver and the area signal light are used to achieve area positioning. The photoelectric receiver uses a photodiode, and the area signal light uses an LED.

4. The indoor area positioning system for a mobile robot according to claim 1, characterized in that, The LED matrix adopts a time address structure, in which each LED in the matrix is ​​assigned a corresponding time address. A single synchronization signal is used to synchronously trigger the LED node and the linear CCD sensor through a combination of a local clock and a wireless chip on the LED node.

5. The indoor area positioning system for a mobile robot according to claim 1, characterized in that, The linear CCD sensor consists of three CCD cameras arranged in a Y-shape, corresponding lens groups, control and data processing units. A light spot on a plane in space is refracted by the lens group and forms an image point on the linear CCD. The three linear CCDs can determine three planes, and the intersection of the planes is the position of the photoelectric sensor.

6. A method for indoor area localization of a mobile robot, applied to the indoor area localization system of the mobile robot as described in any one of claims 1-5, characterized in that, include: S1. Install multiple area traffic lights and RFID readers indoors; S2. When the mobile robot enters the room, the RFID reader is triggered by the RFID tag on the mobile robot and sends a global reset command to the network coordinator. S3. The network coordinator broadcasts the instruction to the LED matrix controllers worldwide to activate all area traffic lights globally and reset the local clock of the LED lights in each area; S4: The photoelectric receiver on the mobile robot detects the frequency in the light signal of the area. After the robot controller queries the frequency mapping table to obtain the area number, it sends a control command to the LED matrix controller of the corresponding area to activate the LED matrix in the area. The LED matrix then cycles to light up all the LED nodes in it. S5. The LED matrix controller resets the clock of all LED nodes after each cycle; the network coordinator sends synchronization messages to the LED nodes and the linear CCD at the same time to control the exposure of the linear CCD sensor. S6. The linear CCD sensor detects the LED light signal. Based on the coordinates of three points in space in two coordinate systems, the transformation matrix between the two coordinate systems is calculated, which is the position of the sensor coordinate system. Then, the pose of the robot in the world coordinate system is obtained.

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