Study Of Environment Monitoring System For Refrigerated Truck Of Agricultral Products Based On Embedded ARM

The promulgation and implementation of China's"Food Safety Law"in 2009 greatly contributed to the standardization and information of China's food production, storage, transportation, marketing and so on. At present, China's Agricultural cold-chain logistics standard has just started, cold chain is still in the initial stage of construction, and refrigerated truck equipment and technology is relatively backward, with low levels of information technology.The loss rate of vegetables and fruits in circulation is as high as 25~30%.To address these issues, an environment monitoring system based on ARM for refrigerated truck of agricultural products was developed, which applied 1-wire bus protocols and WinCE operating system multi-threaded programming. It realized the function of online collection, storage and display of the environmental temperature and humidity data of refrigerated trucks, and used frequency conversion technology to achieve rapid agricultural environment refrigeration of refrigerated trucks. It met the requirement of a modern agricultural product refrigerated truck with some basic functions. The main content of this study and the results as following:(1) Select S3C2410 micro controller as the central controller of refrigerated trucks'environmental monitoring systems, and migrate the WinCE operating system;(2) Apply DS18B20 digital temperature sensor and DS2450S D/A converter, with a combination of HSM40 humidity sensor in the design of information collection module. Use 1-wire data transfer protocol to take an online test on the environmental temperature and humidity, it not only greatly saved the controller's I/O port resources, but also simplified the wiring and reduced mutual interference and ensured the accuracy of information collection. Experiment results showed that the temperature and humidity measurement accuracy is respectively within±0.5℃and±3%RH. At the same time, it enhanced the real-time and reliability of environmental monitoring unit by using WinCE multi-threaded programming techniques.(3) Regulate the temperature of the refrigerated truck refrigeration system with the frequency control method by using the sensorless brushless DC motor to drive compressor, compared to the traditional "fixed frequency" speed mode, it is of high cooling speed, small temperature fluctuations, low noise and high system security;(4) Design a three-phase full-bridge motor drive circuit for brushless DC motor's frequency control, in order to promptly capture the motor "back EMF zero-crossing signal" to detect the rotor position, and thus correct the phase change opportunity, the system changed the kernel code as well as the OAL code of WinCE system, and developed stream drivers associated with the interruption;(5) Apply adaptive fuzzy PID control algorithm to adjust the environmental temperature of refrigerated trucks, and carried out simulation analysis in the MATLAB7.0, the results showed that it is of strong anti-interference and better control compared to the conventional PID control.