Mixed-Norm Multi-Objective Robust Controller Applied to a Very Flexible Aircraft

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90725/1/AIAA-2011-6256-879.pd

Application of Robust Control Design Techniques to the Aeroservoelastic Design Optimization of a Very Flexible UAV Wing

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83662/1/AIAA-2010-9123-917.pd

Design and Analysis of a MEMS Fabry-Perot Pressure Sensor

Accurate dynamic pressure measurements in the jet engine compressors are the key point in the detection of instabilities that are often precursors to surge or rotating stall. Localized pressure measurements are also very helpful in vehicles aerodynamics performance optimization. A new MEMS pressure sensor capable of measuring pressures between 14.7 psi to 100 psi is presented in this work. The sensor is based on the effect of the viscous damping force on the frequency response of a micro cantilever beam. The frequency response of a micro cantilever beam is affected by two types of damping, squeeze film damping and air flow damping. Both these effects are modeled here. The airflow damping is dependent on the air pressure and increases with pressure. This sensitivity to pressure is utilized to predict the ambient air pressure. In order to measure the beam frequency response, a Fabry-Perot interferometer is fabricated using the cantilever beam and the substrate. An electro-optical measurement system is setup to measure the frequency response of the sensor. A custom made pressure chamber is designed and fabricated to allow high pressure tests. The measured frequency response of the cantilever beams are compared with the model results. The experimental results are fitted to the model predictions using pressure as the fitting parameter. The estimated pressure is then compared with the applied pressure. The estimated pressure is in good agreement with the actual pressure for pressures below 40 psi. For the PolyMUMPs fabricated sensors, the error is less than 4% for pressure values smaller than 40 psi

Multidisciplinary Design Optimization of A Highly Flexible Aeroservoelastic Wing

A multidisciplinary design optimization framework is developed that integrates control system design with aerostructural design for a highly-deformable wing. The objective of this framework is to surpass the existing aircraft endurance limits through the use of an active load alleviation system designed concurrently with the rest of the aircraft. The novelty of this work is two fold. First, a unified dynamics framework is developed to represent the full six-degree-of-freedom rigid-body along with the structural dynamics. It allows for an integrated control design to account for both manoeuvrability (flying quality) and aeroelasticity criteria simultaneously. Secondly, by synthesizing the aircraft control system along with the structural sizing and aerodynamic shape design, the final design has the potential to exploit synergies among the three disciplines and yield higher performing aircraft. A co-rotational structural framework featuring Euler--Bernoulli beam elements is developed to capture the wing's nonlinear deformations under the effect of aerodynamic and inertial loadings. In this work, a three-dimensional aerodynamic panel code, capable of calculating both steady and unsteady loadings is used. Two different control methods, a model predictive controller (MPC) and a 2-DOF mixed-norm robust controller, are considered in this work to control a highly flexible aircraft. Both control techniques offer unique advantages that make them promising for controlling a highly flexible aircraft. The control system works towards executing time-dependent manoeuvres along with performing gust/manoeuvre load alleviation. The developed framework is investigated for demonstration in two design cases: one in which the control system simply worked towards achieving or maintaining a target altitude, and another where the control system is also performing load alleviation. The use of the active load alleviation system results in a significant improvement in the aircraft performance relative to the optimum result without load alleviation. The results show that the inclusion of control system discipline along with other disciplines at early stages of aircraft design improves aircraft performance. It is also shown that structural stresses due to gust excitations can be better controlled by the use of active structural control systems which can improve the fatigue life of the structure.Ph