Feedback Speed Control of a Small Two-Stroke Internal Combustion Engine that Propels an Unmanned Aerial Vehicle

Unmanned aerial vehicles (UAV) require intelligent control of their power source. Small UAV are typically powered by electric motors or small two-stroke internal combustion (IC) engines. Small IC engines allow for longer flight times but are more difficult to control and cause significant ground noise. A hybrid operation that uses the engine at high altitudes and the electric motors at low altitudes is desired. This would allow for extended flight with acceptable ground noise levels. Since the engine can not be restarted in the air it must be able to remain at idle for an extended time without stalling. A feedback controller is created for an OS160FX carbureted two-stroke engine. The controller implements a Proportional-Integral-Derivative (PID) algorithm to regulate the rotational speed of the engine shaft. The controller also monitors the temperature of the engine and is capable of monitoring the altitude of the aircraft. It is constructed with commercially available components and is based on an open-source micro-controller. The engine and the controller were ground tested to determine the engine\u27s performance characteristics and the appropriate tuning parameters of the PID algorithm. The controller allows the engine to idle at 1800 rpm without stalling. The controller is able to quickly respond to changes in the commanded speed and settle on this speed within 10 seconds. The speed is regulated through the engine\u27s full range of speeds. The performance of the controller was found to be negatively affected by sub-optimal carburetor fuel-valve settings