Strain Gauge Utilization for Aerial Vehicle Dynamic Load Measurement

by John Bazin

Institution: University of Missouri – Kansas City
Year: 2016
Posted: 02/05/2017
Record ID: 2125343
Full text PDF: http://hdl.handle.net/10355/49496


The strain gauge is a commonly used tool for dynamic load and strain measurement of a system. The work presented in this thesis describes the development and evaluation of strain gauges applied to both an aerodynamic decelerator system and an unmanned aerial vehicle. This thesis has three main objectives: (1)develop and evaluate test a circular parachute strain gauge-based load distribution measurement system, (2) develop and evaluate a strain gauge thrust estimation system for a quadrotor unmanned aircraft, and (3)compare the developed strain gauge-based thrust estimation technique with an indirect real time parameter estimation technique for motor fault detection. In pursuit of the first thesis objective, a load distribution measurement system for the suspension lines of circular parachutes was developed. The motivation to create a load distribution measurement system stems from parachute system design traditionally requiring an extensive flight testing regimen. Numerical solution-based design is difficult due to the highly nonlinear deformation behavior of the parachute canopy. Traditionally, circular parachutes are assumed to have symmetric canopy loading upon inflation and during terminal descent. Asymmetric canopy loading can have a significant impact on circular parachute suspension line loads, but is typically neglected. The developed strain gauge-based load distribution measurement system for circular parachutes has wireless capabilities and can be readily applied to a wide variety of aerodynamic declarator systems. The developed system can be used to observe asymmetric behaviors in order to help determine the significance of asymmetric canopy loading. Custom strain gauge load cells with mounted custom circuitry to calibrate, amplify, and transmit the load data were fixed to canopy suspension lines. Parachute drop testing was performed to evaluate the effectiveness to identify any significant asymmetric canopy loading behavior. Drop testing was performed with a 1.2m (4.0ft) quarter-spherical cross based canopy with a payload of 2.0kg (4.4lbs). A 12m (39ft) guide-line based drop rig was implemented to prevent canopy rotational movement that could hinder testing repeatability. Load distribution data was first verified via both static calibration and in-flight total canopy load measurements. Drop testing was then conducted to identify loading asymmetry during both inflation and terminal descent. Results demonstrated the use of the strain gauge-based load distribution measurement system for measuring significant asymmetric canopy loading patterns. In pursuit of the second thesis objective, strain gauges were used to aid in the development of a thrust estimation system for individual motors/propellers of a small quadrotor unmanned aerial vehicle (UAV). Small UAVs have become increasingly utilized for a wide range of applications; however, such aircraft typically do not undergo the same rigorous safety protocols as their larger human-piloted counterparts. A thrust estimation technique for a… Advisors/Committee Members: Fields, Travis (advisor).