WO2020119101A1

WO2020119101A1 - Nb-iot based classroom light environment control system

Info

Publication number: WO2020119101A1
Application number: PCT/CN2019/095205
Authority: WO
Inventors: 张宇宁; 郦光选
Original assignee: 东南大学
Priority date: 2018-12-14
Filing date: 2019-07-09
Publication date: 2020-06-18
Also published as: CN109640442A; CN109640442B

Abstract

The present invention discloses a classroom light environment control system based on NB-IOT, comprising a device terminal, a cloud platform and a host computer monitoring terminal, the light environment collecting terminal is composed of a main control chip, an NB-IOT module and a camera module, and is used to obtain the light environment information of the entire classroom, calculate the brightness value of each LED in the room through image processing and send the brightness value to the host computer; the LED control terminal is composed of a main control chip, an NB-IOT module, an LED and an LED constant current driving module, and is used to receive a control signal to control LED brightness; the cloud platform serves as a communication relay between the host computer monitoring terminal and the device terminal; the host computer monitoring terminal is used to receive data sent by the collecting terminal and forward the data to the control terminal through the cloud platform, and simultaneously back up the data. The system can calculate and adjust the brightness of the LED in each area in real time according to the classroom application scenario and indoor brightness distribution, providing a healthy and suitable indoor light environment for students.

Description

A classroom light environment control system based on NB-IOT

Technical field

The invention relates to the field of Internet communication technology, in particular to a classroom light environment control system based on NB-IOT.

Background technique

The classroom lighting environment is crucial to students' visual health and learning efficiency. Uncomfortable lighting will cause frequent over-regulation of the human eye, causing muscle tension and visual fatigue. At the same time, it will also cause a decline in learning efficiency and affect the student's mental state.

At present, almost all classrooms are controlled by manually controlled fluorescent lamps, which can only be controlled manually in light and dark states. Unable to adjust the brightness of indoor lamps accordingly to reduce unnecessary power loss when the external ambient light changes; when the lighting in various areas of the classroom is uneven, the brightness of lamps in each area cannot be automatically changed to provide uniform indoor lighting; play during the class In the case of a projector, the traditional situation is to turn off the lights in the first half of the classroom. This will cause the students to watch the projector with a large difference in background brightness and the brightness of the projector, which will increase visual fatigue. Therefore, an intelligent light control system focusing on students' visual health is urgently needed now. In the prior art, the photoresistor is generally simply used to measure the illuminance, and then the brightness of the lamp is adjusted by negative feedback, or the brightness of the lamp is artificially adjusted by manual control on the upper computer side.

Most of today's IoT intelligent light control systems are based on GPRS or wifi, Bluetooth, zigbee and other local area network methods. Although GPRS is based on a cellular network and can be directly connected to the Internet, its cost is high, the flow rate is expensive, and the power consumption is large; LAN Although the cost is relatively cheap, it requires at least two hops to connect to the network, that is, it needs an additional aggregation gateway to access the network, which is disadvantageous in development, installation and maintenance, and hardware costs.

Summary of the invention

Object of the invention: The purpose of the invention is to solve the shortcomings of the prior art, and to provide a classroom light environment control system based on NB-IOT, which has the ability to cover a large number of connections, lower power consumption and lower modules Cost, the ability to collect accurate light environment information in the classroom in real time, calculate the most suitable LED brightness value through judgment and detection of multiple parameters, and send each LED brightness value to the cloud platform through NB-IOT communication, and then send To the monitoring end of the upper computer, the upper computer stores the display brightness information and sends the LED brightness control signal to the LED control end to change the brightness of each LED lamp.

Technical solution: In order to achieve the above objectives, a NB-IOT-based classroom light environment control system according to the present invention is characterized by comprising: a device end composed of a light environment acquisition end and an LED control end, a cloud platform and a host computer Monitoring end

The light environment collecting end is composed of a control chip, an NB-IOT module, and a camera module. The light environment collecting end uses multi-exposure fusion to obtain accurate light environment information in the classroom, and calculates the optimal brightness value of each indoor LED through image processing. Send to the monitoring terminal of the host computer;

The LED control terminal is composed of a control chip, an NB-IOT module, an LED lamp and an LED constant current drive module, and is used to receive a control signal and then control the brightness of the LED lamp;

The cloud platform serves as a communication relay between the monitoring end of the host computer, the LED control end, and the light environment collection end, and the cloud platform and the device end are connected and communicated through the base station;

The monitoring terminal of the host computer includes a server for storing data and a computer interface terminal. The server and the cloud platform exchange information in real time. The computer interface terminal accesses the server in real time to obtain data and distribute data. When the computer interface terminal goes offline, the server remains online Data exchange with the lower end.

As a further preferred aspect of the present invention, the device end is composed of a light environment collecting end and a plurality of LED control ends. The light environment collecting end is installed directly behind the classroom for shooting and recording the overall information of the classroom. Each LED control end is installed In the classroom ceiling, the brightness of an LED lamp is independently controlled, and the communication with the monitoring end of the host computer is realized through the NB-IOT module.

As a further preference of the present invention, the light environment collecting end obtains a wide-angle image by shooting and recording scene images of the entire room, and then transforms the distortion-free planar image for subsequent processing through an image de-distortion algorithm within STM32.

As a further preference of the present invention, the light environment collecting end records the indoor high dynamic range brightness information through multiple exposures of the camera, captures multiple images with different exposures and then restores a reflection through the fusion algorithm and the camera brightness response curve For highly dynamic images of real scene brightness, multiple images with different exposures are obtained by changing the exposure time.

As a further preference of the present invention, the brightness of the desktop is determined according to the obtained high dynamic image, and then the real-time illumination of the desktop is determined according to the reflection characteristics of the desktop. When the illumination of the desktop is higher than the limited value, the LED brightness of the corresponding lamp is continuously lowered until the next acquisition When the obtained illuminance value is within the suitable range or until the LED brightness is 0, the adjustment is stopped, and when the desktop illuminance is lower than the standard value, the LED brightness of the corresponding lamp is increased.

As a further preferred aspect of the present invention, the acquired plane image is used to determine the pixel area where the blackboard is located in the image according to the chromaticity characteristics of the blackboard, and whether the classroom enters the classroom mode is judged based on whether the blackboard contains prominent highlight areas. Decrease the brightness of the LED in the front area of the classroom.

As a further preference of the present invention, the light environment collecting end calculates the brightness required by each LED in the room through the scene brightness information recorded by multi-exposure shooting, and sends it to the cloud platform through the NB-IOT module, and the cloud platform forwards the signal To the monitoring end of the host computer.

As a further preferred aspect of the present invention, the upper computer monitoring terminal is used to receive the collected signal sent by the light environment collecting terminal, display the brightness information of each LED lamp of each classroom on the display in real time and back up the storage, and simultaneously store each The LED brightness control signal is sent to the corresponding LED control terminal.

As a further preferred aspect of the present invention, the host computer setting system is in a manual mode or an automatic mode.

As a further preferred aspect of the present invention, the LED control terminal controls the LED constant current driver through the PWM wave according to the received LED brightness value, and then controls the LED brightness. In order to adapt to the characteristics of the human eye, soft adjustment is adopted when adjusting the LED brightness Way, that is, when the LED brightness is to be increased, the target brightness value is achieved by slowly increasing the PWM wave duty cycle for a period of time; when the LED brightness is to be reduced, by slowly reducing the PWM wave duty cycle for a period of time Reach the target brightness value.

Beneficial effect: The NB-IOT-based classroom light environment control system provided by the present invention has the following advantages compared with the prior art:

1. Compared with the traditional indoor lighting control system, the structure of the device terminal is more convenient, the installation is convenient and the space is small, and the network can be directly accessed without the need for a convergence gateway;

2. The adopted NB-IOT communication method has the advantages of wide coverage, strong connection, low power consumption and low cost;

3. The system can be truly intelligent, record the overall indoor light environment information, and then perform multi-parameter fusion analysis and calculation, and then adjust the response LED brightness to make the classroom achieve the most suitable light environment state, and to a certain extent. Save energy.

BRIEF DESCRIPTION

Figure 1 is a schematic diagram of the structure of the present invention;

Figure 2 is the overall structure of the classroom space structure and lower-end equipment;

Figure 3 is the camera brightness curve, that is, the corresponding relationship between the exposure and the pixel gray value;

Figure 4 is the flow chart of classroom light environment adjustment;

Figure 5 is a schematic diagram of the location of the blackboard, blackboard lamp and projector;

Figure 6 is a structural diagram of the monitoring terminal of the host computer;

FIG. 7 is a specific structural diagram and power supply diagram of the LED control terminal.

detailed description

The present invention will be further clarified below with reference to the drawings.

A classroom light environment control system based on NB-IOT according to the present invention, as shown in FIG. 1, wherein the device end includes two types of devices: a classroom light environment collecting end and an LED control end, one light environment collecting end is composed of: The high-performance STM32 chip, NB-IOT module and camera module are composed, while the LED control terminal is composed of a relatively low-end STM32 chip, NB-IOT module and LED constant current drive controller. The device side communicates with the operator's base station through the NB-IOT module, and the base station connects to the cloud platform. The cloud platform can communicate with the device side in real time, and the device side realizes the function of connecting to the Internet. The cloud platform acts as a relay. After receiving the data information from the device, it can convert the data format and send it to the monitoring terminal of the upper computer. It can also receive the control signal from the monitoring terminal of the upper computer. After converting the format, it can be sent to the device through the base station. When not online, the cloud platform can temporarily cache the data, and then send the data to the device after the device starts NB-IOT communication. The monitoring terminal of the upper computer is the uppermost part of the entire system, including the computer interface and the server. The server interacts with the cloud platform in real time. After logging in, the computer interface can access the server to obtain data and send data. When the computer interface is After going offline, the server can still stay online, interact with the lower-end data and process the data.

As shown in FIG. 2, for the overall arrangement of the system in the classroom of the present invention, the layout of the desks, blackboards, and lamps in the classroom has been drawn in the figure, and this layout is in line with the situation of most existing primary and secondary classrooms. The device is installed at a specific location in the classroom, and interacts with the host computer through NB-IOT communication. The device end includes a classroom light environment collection end and multiple LED control terminals, where the light environment collection end is installed at the ceiling position at the rear of the classroom. Figure 2 shows a typical installation position where the camera can collect The image information of the desktop and blackboard, and it is not easy to be blocked by the student's body when collecting desktop images. The LED control terminal is used to control the brightness of the LED lamps. A lamp is equipped with an LED control terminal device, and each lamp in the room can achieve individual brightness control.

Since classrooms usually have a relatively large space, it is often impossible to record the information of the entire space at once with a lens of ordinary viewing angle. Therefore, the light environment collecting end of the present invention obtains classroom image information through an embedded camera equipped with a fisheye lens or an ultra-wide-angle lens. The fisheye lens is an extreme wide-angle lens. The angle of view can be close to 180 degrees. The overall information of the classroom can be recorded in one shot. However, the captured image has serious distortion. First, the image needs to be distorted.

The core of the classroom light environment acquisition end of the present invention is to synthesize the actual spatial brightness image with high dynamic range through multi-exposure shooting. According to the principle of geometric optics, the illuminance received by the camera sensor has the following correspondence with the actual scene brightness:

In formula (1), E is the illuminance of the camera light sensor plane (CCD or CMOS), L is the brightness of the actual scene, τ is the lens transmittance, and F _m is the reciprocal of the camera relative numerical aperture. At the same time, the light sensor plane illuminance E has the following relationship with the exposure:

H＝E×T (2)

Where T is the exposure time and H is the exposure amount.

As shown in Figure 3, the corresponding relationship between camera exposure and gray value is called the camera brightness response curve. It is fixed after the camera leaves the factory. This camera brightness curve can be restored by experimental calibration. According to the brightness curve and the exposure time used for shooting, combining the formulas (1) and (2), the mapping relationship between the image gray value and the actual scene brightness can be determined.

However, the dynamic range of the image brightness obtained by the camera with one exposure shot is often limited, and the problem of overexposure of the local highlight area or insufficient exposure of the local dark area may occur. The present invention uses multi-exposure fusion to record high dynamic brightness information. Use high-exposure shooting to record information in low-brightness segments of a scene, and low-exposure shooting to record information in high-brightness segments in actual scenes. The minimum number of shots required for a multi-exposure process is determined by equation (3):

n=N _scene /N _camera (3)

Where n is the number of shots required for one multi-exposure, that is, the number of pictures required for high dynamic fusion, _scene N is the brightness dynamic range of the classroom scene, and _camera N is the dynamic range of the camera. After obtaining such n multi-exposure images, weight fusion method is used to fuse the n images into a high dynamic brightness range image. The implementation process is shown in the following formula:

L _i = f(B _i ), i is an integer from 1 to n (4)

Where L _i is the brightness value recovered from a single image, B _i is the pixel gray value, f() is the brightness-grayscale correspondence determined by equations (1) and (2), and L is the fusion of n images The final brightness value obtained after weighting. It can be seen that the closer the pixel gray value is to 128 pixels, the greater the weight in the brightness restoration process. This rule is determined by the shape of the curve in FIG. 2. The closer to the pixel point of 128 gray values, the slope The larger the value, the higher the accuracy in the process of mapping the gray value of the pixel to the exposure amount H and then to the brightness L in this area, so the pixels closer to the 128 pixel value are assigned more weight.

After restoring an image with a high dynamic brightness range, the actual brightness information at any location in the classroom can be accurately obtained. According to the chromaticity characteristics of the classroom desktop, the desktop area in the captured image can be determined. The chromaticity characteristics of the desktop can be determined by referring to data or actual measurements, and then the approximate illuminance of the desktop can be obtained by the brightness of the desktop area. The specific calculation process is as follows. In this calculation, the desktop is approximately equivalent to a complete diffuse reflector:

E _in =πL/ρ (8)

Where E _in is the desktop illuminance, ρ is the desktop reflectivity, and L is the measured desktop brightness. Equation 8 expresses the relationship between the desktop brightness and illuminance. If the calculated desktop illuminance value is not within a reasonable range, then recalculate the brightness of the corresponding fixture in the area, send a dimming command to adjust the brightness of the fixture, and then continue to detect whether the desktop illuminance meets the requirements, and continue to adjust the brightness of the fixture if it does not meet the feedback The flow chart of adjustment is shown in Figure 4.

The blackboard is used frequently in the learning process of the students. The lighting conditions of the blackboard are directly related to the eyesight of the students, so more detailed adjustment is needed. Figure 5 shows the schematic diagram of the positions of the blackboard, blackboard lamp and projector. At the top are two blackboard lamps, which are controlled by their respective LED control devices. The blackboard is located on the front wall, and the projection whiteboard is generally located in the middle of the blackboard. In the area, the whiteboard is usually blocked by the blackboard surface. When it is used, the blackboard surface is pushed away to expose the whiteboard as a projection plane. Firstly, the location of the pixel area of the blackboard in the captured image is determined by chromaticity recognition. The chromaticity characteristics of the blackboard can be determined by referring to data or actual measurement, and the location of the blackboard in the image can be determined according to this chromaticity characteristic. According to the brightness of the blackboard area, combined with formula (8), the blackboard surface illuminance can be calculated, and the blackboard light is adjusted according to the blackboard surface illuminance. This adjustment process is similar to the illumination illuminance adjustment process. When a high-brightness area with a large area is detected in the blackboard area, it means that the projector is turned on and there is a projected image on the whiteboard. At this time, the blackboard light should be turned off, and the brightness of the lamps in the first half of the classroom should be reduced accordingly to enter the multimedia class mode.

As shown in Fig. 6, after calculating the adjusted brightness of the corresponding lamp, the light environment collection end sends this information to the NB base station through the NB-IOT module, and the base station sends the information to the cloud platform, which has a relay cache With the function of converting data format, the binary data received by the device can be converted into json format data and sent to the host computer monitoring end. The json data is specifically sent to the user's server. When the user opens the computer interface, it can be Real-time data interaction with the server. The computer interface has the functions of real-time monitoring of the status of the equipment and manual control of lamps and lanterns.

As shown in Figure 7, the specific structure of the LED control terminal, the power module converts 220V AC to 5V DC and 220V DC, 5V DC is used to power the control chip and NB-IOT module, and the LED constant current drive controller is 220V Power supply can generate a constant current source to drive LED lamps to emit light. The LED control terminal receives the lamp brightness control signal through the NB-IOT module, and after processing by STM32, generates a PWM wave with a corresponding pulse width to the constant current drive controller. The constant current drive controller controls the brightness of the lamp based on the received PWM wave. Based on the frequency limit of human eyes perceiving flicker, the dimming frequency of the lamp should be at least 100HZ. At the same time, considering that when the brightness of the lamp is changed, the sudden brightness change will cause discomfort to the human eye, causing visual fatigue and a decrease in learning efficiency. When adjusting the brightness of the LED, a soft adjustment method is adopted, that is, when the brightness of the LED is to be increased Internally gradually increase the duty cycle of the PWM wave to achieve the target brightness value; when the LED brightness is to be reduced, the target brightness value is achieved by gradually reducing the PWM wave duty cycle over a period of time.

The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the technical field to understand the contents of the present invention and implement them accordingly, and cannot limit the scope of protection of the present invention. For those of ordinary skill in the art, without departing from the principles of the present invention, a number of improvements and retouches can be made, and these improvements and retouches should also be considered as the scope of protection of the present invention.

Claims

A classroom light environment control system based on NB-IOT is characterized in that it includes an equipment end composed of a light environment acquisition end and an LED control end, a cloud platform and a host computer monitoring end;

The light environment collecting end is composed of a control chip, an NB-IOT module, and a camera module. The light environment collecting end uses multi-exposure fusion to obtain accurate light environment information in the classroom, and calculates the optimal brightness value of each indoor LED through image processing. Send to the monitoring terminal of the host computer;

The LED control terminal is composed of a control chip, an NB-IOT module, an LED lamp and an LED constant current drive module, and is used to receive a control signal and then control the brightness of the LED lamp;

The cloud platform serves as a communication relay between the monitoring end of the host computer, the LED control end, and the light environment collection end, and the cloud platform and the device end are connected and communicated through the base station;

The monitoring terminal of the host computer includes a server for storing data and a computer interface terminal. The server and the cloud platform exchange information in real time. The computer interface terminal accesses the server in real time to obtain data and distribute data. When the computer interface terminal goes offline, the server remains online Data exchange with the lower end.
The NB-IOT-based classroom light environment control system according to claim 1, wherein the device end is composed of a light environment collecting end and a plurality of LED control ends, and the light environment collecting end is installed in the classroom At the rear, it is used to record and record the overall information of the classroom. Each LED control terminal is installed on the classroom ceiling to independently control the brightness of an LED light fixture, and communicates with the host computer monitoring terminal through the NB-IOT module.
The NB-IOT-based classroom light environment control system according to claim 1, wherein the light environment collecting end obtains a wide-angle image by shooting and recording the scene image of the entire room, and then passes through the image inside the STM32 The distortion algorithm transforms the distortion-free planar image for subsequent processing.
A classroom light environment control system based on NB-IOT according to claim 3, characterized in that: the light environment collecting end records the brightness information of the indoor high dynamic range through multiple exposures of the camera, and shoots multiple exposures with different exposures The image of degree is then restored to a high dynamic image reflecting the brightness of the real scene through the fusion algorithm and the camera brightness response curve. Multiple exposure images are obtained by changing the exposure time.
A classroom light environment control system based on NB-IOT according to claim 4, characterized in that the brightness of the desktop is determined according to the obtained high dynamic image, and then the real-time illuminance of the desktop is determined according to the reflection characteristics of the desktop. When it is higher than the limit value, the LED brightness of the corresponding fixture is continuously lowered until the next collected illumination value is within the suitable range or until the LED brightness is 0, then the adjustment is stopped. When the desktop illumination is lower than the standard value, the LED brightness of the corresponding fixture is increased.
A classroom light environment control system based on NB-IOT according to claim 3, characterized in that: through the acquired planar image, the pixel area where the blackboard is located in the image is determined according to the chromaticity characteristics of the blackboard, according to whether the blackboard is Contains highlighted areas to judge whether the classroom has entered the classroom mode, if it is the classroom mode, then lower the brightness value of the LED in the front area of the classroom.
The NB-IOT-based classroom light environment control system according to claim 3, wherein the light environment collecting end calculates the brightness required by each LED in the room through scene brightness information recorded by multi-exposure shooting , Sent to the cloud platform through the NB-IOT module, and the cloud platform then forwards the signal to the monitoring terminal of the host computer.
The classroom light environment control system based on NB-IOT according to claim 7, characterized in that: the upper computer monitoring end is used to receive the collected signal sent by the light environment collecting end, and each The LED brightness information is displayed on the display in real time and backed up for storage. At the same time, each LED brightness control signal is sent to the corresponding LED control terminal.
A classroom light environment control system based on NB-IOT according to claim 8, characterized in that the upper computer setting system is in manual mode or automatic mode.
A classroom light environment control system based on NB-IOT according to claim 8, characterized in that: the LED control terminal controls the LED constant current driver through the PWM wave according to the received LED brightness value, and then controls the LED Brightness, in order to adapt to the characteristics of the human eye, a soft adjustment method is adopted when adjusting the brightness of the LED, that is, when the brightness of the LED is to be increased, the target brightness value is achieved by slowly increasing the duty cycle of the PWM wave over a period of time; when the LED is to be reduced The brightness reaches the target brightness value by slowly reducing the duty cycle of the PWM wave for a period of time.