Design Of A Piston Engine Debugging And Testing System For Small Unmanned Aerial Vehicle

Small unmanned aerial vehicle (UAV) has been used widely in military and civil fields. As the power system of the UAV, the piston engine is a device needed the largest repair workload and most complex adjustment in the airborne equipment. The working state of the engine is directly related to taking off safely and flying stably for the UAV. The wear, aging and performance declining of the engine are likely to appear after continuous running, and the stabilization of engine operation is also affected by the wear of the propeller. Therefore, a debugging and testing system must be used to test engine performance, troubleshooting and trial run at fixed periods.In order to achieve performance testing, data analysis and fault diagnosis of the engine and its components, according to the requirements of engine operation and routine maintenance, the main contents of the engine debugging and testing, including the check of airborne sensors and actuators, and the measurement of engine performance parameters and operating parameters ware presented. Accordingly, an engine debugging and testing system was developed. In this paper, main research works are as follows:1) In order to test the engine in the internal and external field, a mobile test stand was designed. The test bench was consisted of mobile platform, a force measuring device, a starting device, an oil supply device, a battery and a junction box. The engine thrust and torsion were measured by the force measuring device based on the moment balance and lever principle, and the sensors could be calibrated by the use of standard weight to simulate thrust and torsion. The safe and convenient starting of the engine was realized by the electrical starting device consisted of a start button, an electromagnetic switch and a start motor. The starting motor could be disconnected reliably from engine by the electrical disconnection device consisted of a disconnection bottom, a disconnection electromagnet and a time-delay relay after engine started. The3-dimensional adjustment for installation position of the starting motor could be realized by the starting device to ensure the engine axis and starting motor axis in the same line.2) In order to provide experimental data for the evaluation of the engine operation state, a portable measurement and control instrument was developed based on Freescale16-bit dual-core microcontroller. The instrument was mainly consisted of a signal conditioning module, a network communication module, a servo control module, a power supply module, a shutdown control module, a liquid crystal display (LCD) module, and other components. The engine operation could be controlled through throttle actuator and the multi-parameters could be measured by the instrument. The changing process of the measured parameters could be displayed through LCD in real time, and measurement data could be uploaded to the data management system through the Ethernet interface, so as to meet requirements for bench test and airborne test with no separation between the UAV and the engine.3) In order to facilitate the management and analysis of measurement data, background data management software was developed on the Visual Basic programming environment. The numerical display of the measured parameters, time-domain waveform display, fast data transmission and storage, data dynamic data playback, data analysis, data monitoring and fault alarm could be achieved by the software with data acquisition mode of real-time measurement and dynamic measurement including five interface for trial run preparing, real trail run, integrity testing, data management and simulating test.Through a large numbers of bench test, the functions and reliability of the system were examined and evaluated. The results show that the engine can be controlled stably and reliably by the system, the change process of the measured parameters of the engine can be really reflected by the measured data. The test requirements for engine performance testing, debugging and maintenance are meet fully.