Development Research and Design Technology-Computer Engineering GPS / GIS / GSM Buying Time Logistics Distribution Auxiliary System Chen Xiaowei, Bao Liwei, Yao Zhibang 2 (1. Institute of Systems Engineering, Zhejiang University, Hangzhou 310027; 2. Zhongheng Century Technology Industrial Co., Ltd Hangzhou, 310053) Combined with the characteristics of the logistics industry, it has been successfully applied in practice.
Logistics is the process of economic activities and business movements that transfer material information from supply to demand. From the perspective of system engineering, logistics is a modern system that organically synthesizes various activities related to transportation, storage, packaging, distribution, circulation processing, and information processing. Therefore, in order to make the logistics system achieve the best operating state, the logistics must be managed from the system point of view. To manage logistics with a systematic perspective, we must first understand the status of the various processes of the system. To this end, we must first collect information on each process of logistics. The information collection equipment is diverse with different forms of required information, such as POS machines, GPS, etc. Perform logistics management and configuration based on the collected logistics information. Taking information collection as the starting point, there are many logistics products with industry characteristics, some of which have played a good role in the application. For example, Zhejiang Zhongheng Century Technology Development Co., Ltd. uses two-dimensional barcodes and POS machines as information Logistics monitoring and management system of collection means.
In order to shorten the logistics completion cycle, increase the distribution speed, and be competent for small batches and multi-variety distribution tasks to meet the current economic development requirements, there is an urgent need to implement real-time monitoring, monitoring and scheduling of logistics distribution tools such as vehicles. To achieve this goal, you need to obtain the location information of the delivery vehicle at any time and let the information be expressed in an intuitive form. To this end, we have designed a logistics distribution assistance system that uses GPS as the information collection method, GIS as the information expression method, and GSM as the communication method.
1 The design of the logistics distribution auxiliary system The overall framework of the system is as follows.
The system is divided into vehicle-mounted stations and monitoring centers. The vehicle platform is composed of GPS user equipment, GPS control system, and GSM communication module. GPS user equipment is used to obtain geographic location information. The GPS control system processes the geographic information received by GPS, and then the GSM * letter module sends the GPS processed information through the wireless network, so the logistics distribution monitoring center receives the information from the vehicle station. information.
The logistics distribution monitoring center is the core of the system, which is composed of the GSM communication module ±, the control center computer and the G 丨 S map table. The GSM communication module of the monitoring center is responsible for receiving the signals sent by the vehicle station, and the control center computer analyzes the received information and transmits it to the corresponding map station. It is processed by the map computer and displays the location of the delivery vehicle. In addition, the monitoring center can also issue instruction messages to control the behavior of the vehicle-mounted device, when to start sending geographic location information, and the time interval for sending geographic location information. The vehicle-mounted station can also actively send a message to the monitoring center to request the operation of sending geographic location information when necessary.
Logistics distribution auxiliary system structure The application object of this system is a logistics enterprise. Compared with similar systems and similar logistics distribution auxiliary systems, it has the following characteristics: the use of GSM as a logistics distribution vehicle to transmit geographic location information to the logistics distribution monitoring center means. The adoption of this solution is based on two considerations: 1) GSM can be used to transmit the geographic location information of the distribution vehicle to the logistics distribution center using a short message system to reduce the operating cost of the system; 2) GSM can be used to achieve the function of voice transmission, which It is considered that when the system is used to realize real-time dispatch of logistics distribution vehicles, the logistics distribution center needs to communicate with foreign personnel in language.
A separate C / A code GPS receiver is used, and no GPS differential reference station is provided to reduce the system construction cost. With this scheme, the geographic location information received may have an error of ~ 100 meters. However, after investigation and research, we believe that the error of 100 meters does not affect the completion of real-time scheduling tasks of distribution vehicles, which can reduce the power, associate researcher; Yao Zhibang, associate professor, general manager: 2001-07-04 cost does not affect the operation of the system.
(3) A communication protocol has been established for the communication between the vehicle-mounted unit of the distribution vehicle and the logistics distribution monitoring center to ensure the quality of the communication and facilitate the system's promotion to the entire industry and the expansion of functions. This work has never been done before by similar systems.
2 Design of logistics distribution monitoring software After the overall design of the system is completed, software design becomes the key to whether the system can be realized. The system software is developed with VisualC ++ 6.0, which has high compilation efficiency, fast running speed, good stability and easy maintenance. From the perspective of practical application, we design the system's software as several large modules for display, all of which are unified in the software user interface of the monitoring center.
The functions completed by the electronic map display module are: displaying the map of the location of the monitored vehicle, implementing the function of the eagle eye navigation map, enlarging the display area, reducing the display area, and graph layering. The data transmission communication software module includes: (1) the communication between the GPS user equipment and the GPS control system. This part enables the GPS control system to receive the geographic information transmitted by the GPS user equipment; (2) the communication between the vehicle-mounted station and the computer of the monitoring center. This part is responsible for receiving the geographic information transmitted by the vehicle-mounted station, as well as the control and scheduling of the vehicle-mounted station; (3) the communication between the monitoring center computer and the map station.
In this part, the monitoring center computer transmits the received geographic information to the map station monitoring the vehicle-mounted station. The coordinate conversion algorithm software is to convert the latitude and longitude coordinates of the vehicle-mounted unit into (x, y) coordinates that can be displayed on the map table. The conversion algorithm needs to be continuously updated as the electronic map zooms in and out. The G1S map database module stores geographic information of the map. The general dispatch control module is designed according to the situation of logistics and distribution monitoring, such as instructing when the vehicle-mounted station sends geographic information, how often to send geographic information, and so on.
The communication information between the vehicle-mounted station and the monitoring center is relatively complex, including control instructions, geographic information, time information, alarm information, etc. If further consideration is needed for the upgrade, it is required to transmit the vehicle's loading information (such as load weight, loaded weight) Etc.) is more complicated; in addition, in order to facilitate the promotion of the system to the entire industry and related industries, a set of protocols has been established for the communication between the vehicle-mounted station and the monitoring center.
3 Message delivery protocol of the logistics distribution auxiliary system Through the introduction of the logistics distribution auxiliary system above, the overall function of the system has been clearly understood, especially the functions of the vehicle-mounted platform and the monitoring center. And these functions are the main basis of communication protocol.
After research, we believe that this agreement must meet the following five requirements: 1) The geographic information of the vehicle station must be accurately transmitted to the monitoring center; 2) The monitoring center must achieve control of the behavior of the vehicle station, when to start sending geographic messages, and why Stop sending geographic messages, etc .; 3) Implement the alarm function; 4) Facilitate system upgrades and adapt to the needs of different industry applications.
SOURCETYPE (information source type) represents the type of information source, that is, the device from which the information is sent. For example, it indicates whether the information is sent by the vehicle-mounted station or the monitoring center.
SOURCElD (information source ID) represents the exact source of information. For example, if the SOURCETYPE byte represents an onboard station, then SOURCE1D represents the number of the onboard station (that is, which onboard station).
DESTTYPE (Information Destination Type) represents the type of information destination, that is, the type of device that accepts the information. For example, whether the information is sent by the vehicle station or a monitoring center.
DEST1D (Information Destination ID) represents the exact device that receives the information. For example, if the DESTTYPE byte represents a vehicle-mounted station, then DESTID represents the number of the vehicle-mounted station.
MSGTYPE (message type) represents the type of the message. In this system, there are mainly the following types. Alarm help message, track record message, system setting message.
MSGID (message ID) is further classified according to the message type. Taking the type of track record message as an example, when the monitoring station commands the vehicle-mounted station to send geographic location information, there are four typical commands: ①Specify the vehicle-mounted station to transmit geographic information according to the start time, interval time, and end time; ②Specify the vehicle-mounted station to press Start location, separation distance and continuous distance to transmit geographic information; ③ order the vehicle-mounted station to immediately begin to transmit geographic information; ④ order to immediately end the transmission of geographic information, etc. Each of the above instructions has a unique MSG 丨 D to represent the MSG (message body) representing the substance of the message. It is closely related to MSGTYPE and MSGID. If the monitoring center sends an instruction to the vehicle-mounted station to transmit geographic information in the form of a specified start time, a specified time interval, and a specified end time, then the start time, time interval, and end time should be stated in the MSG. If the vehicle-mounted station transmits geographic information to the monitoring center, the MSG mainly stores the longitude and latitude information of the vehicle-mounted station.
MSGLENGTH (message length) represents the length of MSG (message body) and is used to help read and analyze MSG content.
Defined by the above protocol, it can be found that this protocol fully reflects the need for easy expansion. For example, if the logistics vehicle needs to run on the specified route due to the needs of the application and the vehicle that deviates from the route is alerted, then add the deviation route to the alarm request information type It is sufficient to alarm, but it is reflected in the protocol by taking an unassigned two-byte integer value in the corresponding MSG1D field for definition. In addition, we can find that the establishment of the agreement makes the information transmitted between the vehicle-mounted station and the monitoring center very standardized, which actually standardizes the communication of similar logistics distribution auxiliary system products. It is also extremely important for the realization of the communication process of the products of similar systems (such as the public security 110 police car monitoring system, the bank banknote transport vehicle monitoring system, etc.).
4 Conclusion Because this system fully considers the operating costs of logistics companies, the actual functional requirements of logistics companies and the scalability of the system design, it has been successfully applied in practice. However, in the application, logistics companies have also put forward higher requirements, hoping to obtain more comprehensive information on distribution vehicles (such as loaded weight, loaded volume). This is also the direction of our next efforts.
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