Design and Implementation of Road Lighting Control System Based on CAN Bus

In recent years, with the rapid development of domestic urbanization, the scale and number of road lighting facilities have expanded rapidly, the power consumption of road lighting has risen rapidly, and there is a serious phenomenon of waste of electricity. The traditional urban road lighting system is generally controlled by a special circuit box to the high-pressure sodium lamp in the circuit to realize the overall switch in the circuit. It is not possible to perform single-point control on a single street lamp in the circuit, and the flexibility is poor, and the sodium lamp has a high supply voltage. The power consumption is large and the ballast needs to be equipped. The change of the power load of the city under different time periods will also affect the service life of the high pressure sodium lamp. Therefore, the circuit voltage needs to be adjusted. In addition, due to the lack of effective monitoring methods, “on-demand lighting” cannot be performed according to the actual conditions of the road surface. Nowadays, while demanding the quality standards of road lighting, how to effectively reduce energy consumption has become a new research direction [1]. At present, some areas are energy-saving and consumption-reducing. The “mid-night light” system is implemented. Some street lights are turned off by adopting “light one by one”, but the uniformity of road illumination is destroyed, which is very unfavorable for traffic safety and social security. In order to effectively realize single point control in the loop and improve the real-time and reliability of data transmission, the CAN bus is used for message transmission, and the high-pressure sodium lamp is replaced by LED light source to realize distributed control in the serial communication network, and get rid of the traditional RS485. The bus master polls the communication method and saves energy. At the same time, the control strategy considers the scene factors such as time, road segment, ambient illuminance and traffic flow, and implements the information interaction according to the preset TPO control strategy [2].

1 Road lighting control system

The schematic diagram of the composition of the road lighting control system based on CAN bus is shown in Figure 1. The system is mainly composed of the underlying CAN node controller part and the computer monitoring part. The node controller is divided into a sub-node street lamp controller (RTU) and a main node loop controller (LTU), and the bottom bus uses a common twisted pair as the communication medium. In the sensor module, a magnetic sensor (or pressure sensor) is configured on each node for detecting vehicle information, and an illuminance sensor collects illuminance information. At the same time, the circuit periodically collects current, voltage, power factor and other electrical parameters, and each node LED dimming circuit can set multiple levels of street lamp brightness. The information communication between the sub-nodes of the street lamps and between the sub-nodes and the main nodes is realized through the CAN bus.

The computer monitoring section is responsible for the adjustment of the control strategy. The master node loop controller uploads the state parameters to the computer monitoring part and stores them in the database. The computer compares the normal data, determines the abnormal conditions in the loop, determines the abnormal position, and sends a control command to the master node. system

Features:

1 Monitor traffic flow and weather conditions;

2 single lamp fault detection;

3 monitoring power consumption;

4 control current to achieve single lamp dimming;

5 Reasonably adjust the number of lights and

time.

2 How does vehicle information control work?

The master node combines multiple policies according to the TPO (time place occasion) control strategy, with LED lights as the control object. The main control strategies include:

1 minute time control. For different lighting requirements, use hierarchical lighting brightness, control all street lights to stay bright during busy hours at night, adjust the street lights to lower brightness when traffic is scarce near midnight, and realize smart lighting for further stepping. Vehicle Information

Control mode, detecting that the vehicle adjusts brightness by information;

2 Environmental parameter control. Adjust the lighting control according to the actual environmental parameters such as illumination and traffic flow to obtain better lighting quality and power saving effect, such as opening the street light in advance in case of poor weather and low visibility, or monitoring the vehicle flow at a certain During the period of sudden change (proliferation), timely adjust the street lights to highlight to emergency.

3 group control [1]. Different street lamps in the same lighting circuit may have different illumination brightness requirements due to their different positions. With the characteristics of LED single lamp control, it is possible to specify certain sub-nodes in the loop to form a group to achieve different Scene control. For example, some nodes only use time control strategies, some nodes use vehicle information control strategies, and sub-nodes of critical road segments (such as warning lights, landscape lights) are not adjusted and remain highlighted.

4 Vehicle information control. Compared with the traditional lighting strategy, the vehicle information control strategy better reflects the characteristics of “on-demand lighting”, actively perceives the situation of vehicles on the road, adjusts the brightness of the current road segment, and introduces a predictive mechanism for the lighting requirements of the next road segment. Adjust the brightness of the street lights to be highlighted before the vehicle arrives.

This paper focuses on the implementation of the vehicle information control strategy, which is based on the approximate position of the vehicle and the direction of travel for closed-loop control, which can adjust the illumination of the front road segment. The system main node loop controller first requests the vehicle information of each sub-node to pass the information, and synthesizes the vehicle information, determines which node positions in the current loop have vehicles passing, and requests the street lamp brightness information at the position and the next road position where the vehicle travels. And determining whether the brightness of the street light of the child node is a highlighted state, and transmitting brightness adjustment information to the street light child node whose brightness is low, so that the brightness is adjusted to match the running of the vehicle, and the other child nodes not related to the driving of the vehicle are temporarily not affected. To achieve single lamp control, the control effect is shown in Figure 1.

When the master node transmits a vehicle information request frame with an ID identifier, if the ID identifier is defined in each child node, the child node can receive the vehicle information request frame. If multiple child nodes detect that a vehicle passes at the same time, the receiving vehicle information message object in the master node can receive the message of multiple child nodes in turn by setting the mask bit and according to the non-destructive bit arbitration mechanism of the CAN [3]. information. The request and transmission of the child node luminance information is similar to the vehicle information. Each sub-node can receive a single-point brightness control frame, and can judge whether it is consistent with its own address in the data segment, and if it is consistent, modify the current street lamp brightness.

3 node controller composition

The node controller uses Infineon's 16-bit microprocessor XE164FM [4 - 5], which has 4 independent CAN nodes, up to 128 independent message objects, and data transfer rates up to 1 Mbit / s. The peripheral part includes a CAN transceiver module, a serial communication module, an LED dimming circuit module, a vehicle sensor module, a power module, an illuminance sensor module interface, and an LCD display module.

Interface, JTAG online debugging interface, etc., as shown in Figure 2.

The CAN transceiver uses the IFX1050G. The PWM pulse of different duty cycles can be generated by the timer GPT1 module. The brightness of the street light is set by the IO output PWM wave to the LED dimming module. T2 is triggered when a rising edge transition occurs after the T3 timer overflows. The T2 register is reloaded to the T3 timer. T4 is triggered when the falling edge of the T3 timing overflow occurs. The contents of the T4 register are reloaded into the T3 register. The set value and brightness are shown in Table 1.