Abstract: Fuel cell power system is a long endurance power scheme for electric Unmanned Aerial Vehicles (UAVs), and the control technology of fuel cells is critical to the reliability and efficiency of the power system. For small air cooling open cathode proton exchange membrane fuel cells used in UAVs, a feedforward fuzzy PID method for stack temperature control and an ampere-hour integration threshold method for membrane water management are proposed. The proposed methods consider the overall control process of the fuel cells for engineering applications, taking into account simultaneously the fuel cell temperature control and water management to achieve efficient control of the entire fuel cell system. Through the developed test platform, the proposed control technology is tested, verified, and compared with the existing temperature control and water management methods. The results show that the proposed feedforward fuzzy PID, similar to the traditional fuzzy PID, can reach the target temperature faster than the PID method during the long time startup process of the fuel cell, reducing the response time by 7%. When the fuel cell current continues to decrease, the proposed feedforward fuzzy PID, with its overshoot being 34% of that of the PID method and 43% of the traditional fuzzy PID method, exhibits an obvious advantage in inhibiting the overshoot. The proposed ampere-hour integration threshold control method for water management can not only prevent the flooding failure, but improve the fuel economy, saving about 15% of hydrogen in the test compared with the existing water management method.

Key words: UAVs, fuel cells, thermal management, water management, feedforward fuzzy PID control