Comprehensive System Identification of Ducted Fan UAVs - Cal Poly

3.3 Servo Actuator IdentificationThe goal of the actuator test program was to measure a set of data that was used toidentify models of the actuator dynamic response characteristics. These actuator modelsinclude linear transfer functions of the input/output relationships as well as non-linearactuator properties such as actuator rate and position limits.The identification was performed using the CIFER. Linear 0 th /2 nd order transferfunctions capturing the actuator dynamics were identified. Testing allowed for thedetermination of the maximum angular rates and positions using linear curve-fitting ofthe square wave responses. An explanation of the construction of the actuator blockdiagrams built is also included. The actuators are a critical part of the flight controlsystem and it is important to have accurate models of the dynamics and limits of theactuators themselves. Individual blocks were created for each actuator corresponding toeach of the tested 5 volt and 6 volt conditions. This section also includes a time domainvalidation of the actuator models.The goal of bench testing the control surface actuators was to collect a set ofbench test data that will be used to identify the actuator dynamics. This test data was alsoused to determine the position and rate limits of the actuators. The significance of othernon-linear actuator properties, such as hysteresis and stiction, are also evaluated from thebench test data.The bench testing was carried out in accordance with CIFER flight test techniqueswherever possible. Five separate actuators from four manufacturers were tested. The- 56 -