Design Of Direct Methanol Fuel Cell Control System Based On CAN Bus

With the development of world economy, human being has to start looking for new energy sources to replace traditional energy sources because the phenomena of the lacking of traditional energy source and environment pollution is more and more serious. Direct methanol fuel cell (DMFC) system with its advantages of efficient, environmentally friendly, easy to access and storage, becomes one of the best alternative energy sources, which is widely used in the automotive, power, defense and aerospace technologies, etc.This dissertation is mainly about the design of DMFC control system based on CAN bus. The control system which has the characteristics of "perfectly formed" is a very complex system, because the number of signals to collect and objects to control is huge. Therefore, distributed control structure based on CAN bus is adopted in this system to solve the complex problems of signals collecting and objects controlling. Eight types of smart nodes are designed in the system, and the data exchange between them is based on CAN bus. Meanwhile, a dedicated CAN bus application layer communication protocol is designed based on the DMFC control system, including the design of communication scheme, the message identifier of the distribution, data format definition and design of packet data frame.The research about energy hybrid approach of the system is also an important part of the dissertation. The system consists of three energy units:methanol fuel cells as the core energy source; super capacitor as the main energy mixing unit; and lithium batteries as auxiliary power. The energy of system boot process mainly provided by lithium battery. In the normal work course, the system energy mainly relayed on outside super capacitor discharge. When the super capacitor voltage is below 11V, the methanol fuel cell will be selected as the main energy source, and it will charge the super capacitor while discharge on the external load. The overall objective of energy management system is to maintain a constant output voltage, and meet the requirements of power the external load.Finally, the dissertation describes the system's testing process. A test software is designed to observation and analysis data conveniently. All of the experimental tests are based on this test software. The tests include single battery voltage measurement, optimal allocation of energy testing, water and heat management testing and the concentration of methanol management control testing. Experiments show that the system has the characteristics of safety, stability, efficiency and reliability, the system meets the design requirements basically.