Dr. John Valasek
Seminar 1: Multiple-Time-Scale Nonlinear Output Feedback Control of Systems With Model Uncertainties (Dr. John Valasek)
WebEx Link: https://force.my.webex.com/force.my/j.php?MTID=mba10bd9e12f5b612d2adc2b79c1c7d2f
Meeting number (access code): 2550 544 5654
Meeting password: neCev2rfT35 (63238273 from phones and video systems)
Abstract: Systems with dynamics evolving in distinct slow and fast timescales include aircraft (Khalil & Chen, 1990), robotic manipulators, (Tavasoli, Eghtesad, & Jafarian, 2009), electrical power systems (Sauer, 2011), chemical reactions (Mélykúti, Hespanha, & Khammash, 2014), production planning in manufacturing (Soner, 1993), and so on. The Geometric Singular Perturbation theory (Fenichel, 1979) is a powerful control law development tool for multiple-timescale systems because it provides physical insight into the evolution of the states in more than one timescale. The behaviour of the full-order system can be approximated by the slow subsystem, provided that the fast states can be stabilised on an equilibrium manifold. The fast subsystem describes how the fast states evolve from their initial conditions to their equilibrium trajectory or the manifold. This presentation develops two nonlinear, multiple-time-scale, output feedback tracking controllers for a class of nonlinear, nonstandard systems with slow and fast states, slow and fast actuators, and model uncertainties. The class of systems is motivated by aircraft with uncertain inertias, control derivatives, engine time-constant, and without direct measurement of angle-of-attack and sideslip angle. One controller achieves the control objective of slow state tracking, while the other does simultaneous slow and fast state tracking. Each controller is synthesized using time-scale separation, lower-order reduced subsystems, and estimates of unknown parameters and unmeasured states. The estimates are updated dynamically, using an online parameter estimator and a nonlinear observer. The update laws are so chosen that errors remain ultimately bounded for the full-order system. The controllers are simulated on a six-degree-of-freedom, high-performance aircraft model commanded to perform a demanding, combined longitudinal and lateral/directional maneuver. Even though two important aerodynamic angles are not measured, tracking is adequate and as good as a previously developed full-state feedback controller handling similar parametric uncertainties. Additionally, even though the two controllers in theory achieve two different control objectives, it is possible to choose either one of them for the same maneuver. Of the two new output feedback controllers, the slow state tracker accomplishes the maneuver with less control effort, while the simultaneous slow and fast state tracker does so with a smaller number of gains to tune.
VSCL student 
Garrett Jares ’17 will be presenting the paper “Flight Demonstration and Validation of Control Acquisition Autopilot Attack”. The paper investigated a method of cyber attack by which an attacker might take over control of a vehicle. This paper built upon prior work by demonstrating and validating the attack on a DJI F450 quadrotor running the ArduCopter autopilot. The experiments focused on two scenarios. One in which the victim performed regulation while the attacker performed non-zero setpoint control and another in which the victim performed non-zero setpoint control while the attacker performed regulation of the system. The experimental results show how the attack poses a threat to real-world UAS and evaluates its performance under different control scenarios.
Chris Leshikar ’20 will be presenting the paper “System Identification Flight Testing of Inverted V-Tail small Unmanned Air System”, which addresses challenges in conducting flight testing an inverted V-Tail fixed-winged vehicle and the results obtained from the flight tests. The goal of the flight tests was to obtain longitudinal, lateral/directional and combined longitudinal lateral/directional linear state-space model for the RMRC Anaconda using the Observer\Kalman Identification (OKID) algorithm. Both manual and automated excitation signals were injected into the Anaconda. Parametric sweeps of the excitation signals were performed using the Developmental Flight Test Instrumentation Two (DFTI2) system. The identified longitudinal linear state-space model modelled the longitudinal dynamics well and the identified lateral/directional reasonably well while the identified combined longitudinal lateral/directional model showed decent correlation with the decoupled models.
Maison Clouatre is an incoming Ph.D. student in the aerospace engineering department. He will graduate in May 2022 with a double major in electrical engineering and mathematics from Mercer University. As an undergraduate, Clouatre held visiting research positions in the Electronic Systems (ELSYS) Laboratory at the Georgia Tech Research Institute (GTRI), the Vehicle Systems & Control Laboratory (VSCL) at Texas A&M University, and the Laboratory for Information & Decision Systems (LIDS) at the Massachusetts Institute of Technology (MIT). His research interests lay at the intersection of control theory, optimization, and learning, and he focuses on applying his theory to the fields of quantum information science and aerospace engineering. Clouatre is both a Goldwater Scholar and Stamps Scholar. At VSCL, Clouatre will research quantum control and learning for quantum dynamics.
Cassie-Kay McQuinn ’21 is an M.S. student in the aerospace engineering department. Cassie-Kay has been an active member of VSCL since Fall 2021, working in system identification. She will graduate in December from Texas A&M University with a B.S. in Aerospace Engineering with Engineering Honors. In addition to completing Engineering Honors, she is a Presidential Endowed Scholar, the 2021 Aerospace Engineering Advisory Board Scholarship recipient, and has earned a certificate of Holistic Leadership in Engineering through completion of the Zachry Leadership Program. She is the current Vice President of the Texas A&M chapter of the Sigma Gamma Tau Aerospace Engineering Honor Society. As an undergraduate she interned with L3Harris Technologies working in the Structural Analysis and Structural Design departments. Cassie-Kay’s main interests include flight test engineering, aircraft dynamics and system identification.
Alex Gross, a Junior Aerospace engineering student, has been awarded the prestigious AIAA Cary Spitzer Digital Avionics Scholarship.