Ground test results of rotor governor and rate SAS for small tilt rotor UAV

A scaled flight model of a tilt rotor aircraft for the smart UAV program has been developed. Because the flight characteristics of tilt rotor are not well known, the developed scaled model would be helpful to evaluate flight control algorithm of full scale aircraft. Prior to conducting the flight test of this scaled model, we performed the ground test using the 4-degrees of freedom ground test rig in order to evaluate the flight control system of scaled model and control algorithms. The ground test rig allows freedoms in pitch, roll, yaw and heave motions. A rotor governor algorithm and rate SAS feedbacks were evaluated on the ground test rig under hovering power condition. A rotor governor is usually used for tilt rotor aircraft instead of engine governor due to the speed sensitivity caused by a collective pitch deflection in airplane mode. In order to increase the response of vertical axis in helicopter mode, a collective pitch gradient as a function of the throttle command is used for direct collective control similar to engine governor. Through a performance evaluation of the proposed rotor governor in the test rig, an optimal RPM was selected. The performance of rate SAS for pitch, roll and yaw axes were also evaluated qualitatively on the test rig. This paper describes the ground test results of the rotor governor and rate SAS on the 4-degrees of freedom ground test rig.