Lighting control: energy saving and humanization are the key points

In 1787, Watt invented the centrifugal governor, the speed regulation of the steam engine, which was considered as a landmark event for the large-scale application of automatic control technology. Research on control theory has become a major need of society. Since then, the development of control theory has gone through three stages. The first stage is the classical control theory stage based on feedback theory, which can only solve the linear input system problem of single input-single output; the second stage is the modern control theory stage, which mainly solves the problem of multi-input-multi-output system, not only For the linear steady system and the nonlinear time-varying system, a good solution is also proposed. The third stage is the intelligent control stage. Combined with artificial intelligence technology and intelligent algorithm, the complex system is controlled. The intelligent control is at home and abroad. A very active and challenging area represents one of the latest directions in the development of science and technology today.

In 1879, Edison invented incandescent lamps to illuminate the world. People's lighting methods were changed. The lighting requirements were no longer limited to the rigid demands of visual shading. The light environment required a richer experience and artistic enjoyment. Pay more attention to energy conservation, environmental protection and health. After entering the 21st century, network and informationization have become the mainstream of the times. Combined with the development of control disciplines, it has provided means for people to achieve these pursuits.

Research and application of lighting control

The continuous advancement of research and application of control theory and technology has promoted the development and application of lighting control. In accordance with the three development stages of control theory, lighting control has also gone through three stages: traditional lighting control with manual as the main control method, automatic lighting control based on digital control technology, and computer technology, communication technology, and automation. Control technology-based intelligent lighting control has now entered the era of intelligent lighting control. With the rise of smart cities, smart lighting has become an inseparable part of smart cities, and the core of smart lighting is intelligent lighting control.

2.1 Lighting control and energy saving

With the outbreak of the global energy crisis, green lighting and low-carbon lighting are imperative, and even zero energy consumption is proposed. Lighting control plays a vital role in lighting energy conservation and is an indispensable means of achieving green lighting. The object of lighting control is the light, and the control of the lighting fixture is the dimming control. Dimming control has experienced variable resistance dimming, voltage regulator dimming, thyristor dimming, and pulse width modulation (PWM) dimming, which saves a significant amount of power.

In recent years, in outdoor road lighting, lighting control technology is adopted. When the traffic volume of a person is large, the street lamp is fully powered, and when the night is quiet and the traffic volume of the vehicle is low, the half-power operation, that is, the implementation of dual-power street lighting, achieves energy-saving effects. With the development of LED light source technology, efficiency improvement and price reduction, it is easier to control, drive and dim, which provides great possibilities for lighting energy saving. Such as Beijing, Shenzhen and Shanghai, the underground large space, tunnels, subway stations have been newly built or renovated, directly using LED lighting, using intelligent control system, dimming according to different time periods, saving energy; intelligent perception in the office and other spaces Whether or not to achieve automatic dimming according to the behavior of the person using the lamp, to meet the lighting needs of different people, to create a comfortable, energy-saving light environment.

Indoor lighting control not only targets a single system, but also integrates with other systems to achieve optimal control of energy savings. Since 2010, Tongji University has participated in the “International Solar Decathlon Competition” initiated by the US Department of Energy for three consecutive years, aiming to build “zero energy consumption” buildings. First of all, the indoor lighting can be continuously dimmed and linked with the shading system. It is free to choose the natural illumination to supplement the illumination or the artificial illumination to increase the indoor illumination. Secondly, according to the needs of different situations, the lighting system sets different scene modes (such as: visitor mode, viewing mode, dinner mode, party mode), and can complete one-button switching to meet people's needs. Finally, the lighting control system is highly integrated with other control systems (air conditioning, hot water, ventilation, phase change materials) and integrated into the same large control system, as shown in Figure 1, with a user-friendly interface that is user-friendly and easy to operate. The intelligent and user-friendly control strategy can be accessed through the local interface or through the mobile phone and remote computer to achieve detailed monitoring of detailed energy consumption distribution, real-time measurement and statistics of energy consumption of each power circuit, and zero energy consumption.

Figure 1 Intelligent Integrated System

2.2 Lighting Control and Health

The development of society has made people pay more and more attention to the relationship between lighting and human health. People not only need to have lights, but also need a natural, safe, comfortable and healthy light environment. Studies have shown that humans have formed many mechanisms to adapt to light during the evolution process, and the physiological and psychological effects of illumination on people are significant. Light mainly affects people's physiological functions through the nervous system, such as biological rhythm, immunity, etc. There is an inverted U-shaped curve between illumination intensity and emotion. The subjects think that too dark or too bright illumination will impair the emotional experience; The influence is also regulated by some factors such as color temperature. The illuminance and color temperature also interact. The researcher in the simulation classroom found that under the condition of medium and high color temperature, the learning ability of the subject is improved, but the high color temperature is easy to cause fatigue and tension, so the classroom should be suitable. Artificial lighting with medium color temperature (4000K); at the same time, phototherapy has become a mature solution to the seasonal affective disorder (SAD). Various studies have shown that lighting is inextricably linked to people's health. People use lighting control to adjust the physiological flux and color of human light by adjusting the output luminous flux and color temperature of the artificial light source to provide the most healthy lighting environment.

People have always liked natural light, advocating its sense of direction, security and good color, while also thinking that artificial lighting can be controlled. Therefore, the linkage control strategy using natural light and artificial light will be more in line with the "people-oriented" design concept. By controlling the amount of twilight projection to the amount of space used, supplemented with appropriate amount of artificial illumination; predicting the indoor natural illuminance distribution according to the vertical illuminance distribution projected by the twilight to the window, controlling the opening degree of the electric curtain and the illumination level of the indoor artificial illumination To create a healthy, energy-saving, comfortable lighting space.

To properly control the opening degree of the curtain and the illumination of the artificial lighting in the room, it is necessary to scientifically predict the illumination distribution of the natural light in the room. Because of the variability of natural light and the variability of office space, it poses a difficult problem to predict the illumination distribution of indoor natural light in time, and the rise of intelligent control research provides an advanced means for us to solve this problem. Figure 2 shows the combined control system for artificial lighting and natural daylighting.

Figure 2 Joint lighting control system for artificial lighting and natural lighting

Taking the Jiading Campus Library of Tongji University as an example, the researchers proposed a comprehensive and optimal result based on the two-dimensional fuzzy control algorithm in order to achieve the comprehensive optimal results of the leaf angle of the sunshade louver to the lighting, ventilation and occlusion. The control system is shown in Figure 3. The brightness sensor is set to detect the current sky brightness as an input parameter for controlling the sunshade blade angle system, and the intelligent sunshade control system of the two-dimensional fuzzy control algorithm is used to control the louver angle to adjust the natural light and control the artificial illumination. It not only ensures that the illumination at the window is not higher than the highest illumination that can be accepted by the human eye for a long time, but also makes full use of natural lighting instead of artificial lighting, saving corresponding energy consumption and realizing the humanization and intelligence of library lighting.

Fig. 3 Block diagram of intelligent sunshade control system based on two-dimensional fuzzy control algorithm

2.3 Lighting Control and Management

Urban lighting monitoring systems are the most extensive and successful example of lighting control technology applications. With the development of urban construction, the urban span has increased, and the number of lighting controllers has increased dramatically. Therefore, the control and management of urban lighting equipment is particularly important. Conventional lighting control usually uses a timer or a light controller to allow different areas to be turned on in a predetermined state, but real-time control is not possible, and it is not convenient for remote monitoring and management, which often causes failures and cannot be repaired in time. With the development of communication technology and computer technology, the use of computers with certain communication methods, such as GPRS, 3G technology, etc., can be used in all areas of the city, road sections, landscape lighting box substations, substation cabinets, control cabinets, etc., from the measurement and control system Centralized implementation of intelligent data collection and monitoring, namely supervisory control and data acquisition systems. Through the urban monitoring system, it is possible to combine the climate, sunrise, sunset, season and other natural factors of different regions, flexibly and effectively control the light source, formulate different control strategies, and meet the human needs for lighting under the premise of providing necessary safety lighting. To achieve effective energy conservation. In addition, effective real-time monitoring can detect safety faults in time, replace maintenance equipment in time, and minimize human losses and inconveniences. It is an indispensable technical support and effective way for urban management departments to implement scientific management.

Latest developments in lighting control technology

3.1 Humanized and personalized lighting

Lighting is first and foremost a visual need, as well as physical health, work safety and efficiency, quality of life and security, traffic safety, leisure activities and enjoyment of life. It is important to meet the circadian rhythm of people's physiology. With the rapid development of intelligent control technology, while meeting the visual, physiological and psychological needs of people, it also plays an increasingly important role in the "people-oriented" health lighting. For example, indoor lighting control not only limits the controlled object to lamps or curtains, louvers, etc., but should understand lighting control as various aspects that can affect the lighting environment. At present, the intelligent dynamic lighting system using new LED light sources and lamps in the room can be illuminated with different illumination and color temperature as needed. With the change of natural lighting, the luminous flux of the light source can be adjusted, the output illuminance can be controlled, and the color temperature can be adjusted. It can provide cool blue light illumination with blue light in the morning and warm white light illumination at night, truly “on-demand light control”. "To create a comfortable light environment."

3.2 Intelligent lighting

With the continuous development of the control discipline, in the 1970s, the development of control theory entered the advanced stage - the intelligent control stage. Intelligent control has been greatly applied and developed in various aspects. The continuous advancement of intelligent control research and application has contributed to its application and development in lighting control. With the advent of the era of big data, wireless communication technology and cloud computing technology have also been greatly developed in intelligent lighting control systems, as shown in Figure 4:

Figure 4 Intelligent lighting control system

With the rise of smart cities, smart lighting has become a new development direction for the development and application of intelligent lighting control, and is the best practice of green lighting in smart cities. It realizes remote centralized control and management of street lamps by applying advanced, efficient and reliable power line carrier communication technology and wireless GPRS/CDMA communication technology. It has automatic adjustment of brightness, remote lighting control, fault active alarm and lamp line according to traffic flow. Cable anti-theft, remote meter reading and other functions can greatly save power resources, improve the level of public lighting management, and save maintenance costs.

Summary and outlook

This article focuses on the latest research results, application areas and development trends of lighting control and technology. As we all know, the ultimate goal of lighting control is to scientifically control people's lamp behavior, which requires a lot of research on "human lamp behavior" to obtain reasonable results. With the further maturity of big data cloud computing and service technology, data collection and analysis of human lamp behavior is possible, which will bring more optimal control and decision-making solutions for lighting control. On the other hand, with the in-depth study of the balance between lighting energy consumption and visual comfort, it not only meets energy-saving but also healthy humanized lighting, lighting control technology that integrates networking, personalization and intelligence will be applied. More extensive. At the same time, the research results of modern control theory and intelligent control algorithm are combined with the lighting control strategy, and the image processing, power carrier and other technologies are introduced into the lighting control to a greater extent, to obtain more accurate control effects, and to achieve intelligent lighting.

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