Modification of a longitudinal wind tunnel balance for identification of Micro Air Vehicle instabilities

Research regarding Micro Air Vehicles (MAVs) has been a priority in the defense industry for several years. Recently, the interest in this area has grown in the academic environment. For MAV research, RIT currently has a longitudinal, load cell based wind tunnel balance designed, fabricated and validated by Andrew Walter [1]. The balance allows for the measurement of lift and drag. The objective of this research is to further the capabilities of the balance system by automating the testing procedure and modifying the data acquisition system to collect dynamic frequency domain lift and drag measurements. Obtaining dynamic data will allow the measurement and characterization of oscillatory instabilities in MAVs and airfoils at near stall angles of attack. The primary improvements include the utilization of filters to remove the structural influence of the balance from the frequency data, the addition of an inclinometer into the data acquisition, and the integration of a controller and step motor to automate angle of attack adjustments. Tests were performed on a flat plate to validate the automation of static data collection and the LRN-1007 to validate dynamic data acquisition and analysis. The flat plate test data agrees with published values with minor bias error. The sources of bias error include test section wall interaction, minor changes in calibration values over time, and test object interference with the pressure probe at high angles of attack. The LRN-1007 was successfully tested and compared with published values using the Strouhal number to angle of attack relationship. The flat plate and LRN-1007 testing provides sufficient evidence to validate the capabilities of the upgraded balance. Additional testing was performed on the RIT Thnikkaman MAV to fulfill the designed purpose of balance system