Hannah Lehman and Chris Leshikar graduated with their Ph.D. Degrees in Aerospace Engineering.Congratulations Hannah and Chris, VSCL is proud of your accomplishments!

 

 

 

 

 

 

 

Hannah Lehman is the 62nd graduate student advised to completion of their degree by Dr. Valasek, and the title of her dissertation is “Hierarchical Auctions for the Coordination of Heterogeneous Agents using Machine Learning“. Hannah will be working at Sandia National Laboratories, where she has now done four graduate internships.

 

 

 

 

Chris Leshikar is the 63rd graduate student advised to completion of their degree by Dr. Valasek. Chris’s research was supported by the National Science Foundation under the Center for Autonomous Air Mobility and Sensors (CAAMS) and the title of his dissertation is “Markov Parameter Based Methods for System Identification“. Chris will begin seminary formation for the Catholic Diocese of Victoria later this year.

 

 

 

1^st Lt Noah R. Luna, USAF successfully defended his M.S. thesis on June 12th, 2025.  Noah has been with VSCL since he graduated from the USAF Academy and commissioned in June 2023.  The title of his thesis is: Real-Time Controller Architecture for the Flight Test of Custom Control Algorithms on Small Unmanned Aircraft Systems

Flight test of experimental controller designs can be difficult when using commercially available hardware on small unmanned aircraft systems. The supported software often relies on specific messaging protocols to send commands to the aircraft which can vary significantly between controllers. Furthermore, modification of an existing package to accept different types of controllers can prove to be a difficult task. This thesis details a real-time control architecture for small unmanned aircraft systems, named Kanan, capable of safely and quickly integrating a variety of flight controller designs on a various platforms including fixed-wing aircraft and rotorcraft. Kanan is a C++ based software package which supports command authority using RC channel overrides, attitude control, and both local and global position control. The Robot Operating System and MAVLink messaging protocols are fundamental for how messages are shared between an Ardupilot flight stack and onboard companion computer. Additionally, the framework provides support for pilot operated safety measures and the ability to perform common flight test maneuvers, such as doublets or sawtooth climbs, for further control system and vehicle analysis. A low-barrier to entry is achieved by restricting all necessary changes needed for various tests to only two files and including a graphical user interface to reduce the required experience to operate the ground station computer. Testing and development of experimental flight controllers with Kanan can be done more quickly and significant changes can be made to the control design without having to modify or sacrifice existing data logging and safety functionality.

Noah addressed the need for a capability to easily port custom complex control laws from our research into commercial autopilots for use in demonstrating and evaluating them in flight testing.  Noah has named his system Kanan, after his son Kanan whom was born a few short months ago. Noah’s research is supported by the United States Air Force and during his time with VSCL has contributed to all of the current research projects. Noah was also a grad assistant and lead for Dr. Valasek’s AERO 401/402 project this past year, in which a team of six Aero students addressed another need: a modular and extensible common architecture for sensors/avionics/navigation/autopilot. The new system is called Modular Open System Architecture for Low-cost Integrated Avionics (MOSA LINA).  A paper on this framework was submitted to 2026 AIAA SciTech.

Noah’s is the 65^th graduate degree completed that Dr. John Valasek has advised.

Jillian Bennett successfully defended her M.S. thesis on June 11th, 2025.  Jill has been with VSCL since her senior year in Spring 2023 and is highly engaged in control theory, and flight testing. The title of her thesis is: Nonlinear Adaptive Multiple Time Scale Stability Analysis For An Arbitrary Number Of Time Scales

 Multiple time scale systems are a set of subsystems that are dependent on each other yet have a large separation in the time which the dynamics progress. Systems of this sort are often simplified by dismissing the dependencies between vehicle states, however, the true dynamics get lost and are important to the stability of the system. Additionally, true systems have uncertain plant dynamics and disturbances that can cause instability. Therefore, a method of control must be used to account for uncertainties. Adaptive control has been shown to counteract these additional sources of motion. A combination of adaptive control and multiple time scale control for nonlinear systems is applicable to and necessary for the systems mentioned above and has been demonstrated in a method called [K]Control of Adaptive Multiple Time Scale Systems (KAMS), yet only accounts for two time scale systems. This work extends the theory and stability proof of KAMS to account for a system with any number of time scales. It also further analyzes the limitations to the time scale separation parameter size of a two and three time scale system.

Jill developed and conducted outstanding theory for nonlinear time scale systems, and the work will continue. Jill is doing a summer grad internship with Naval Research Laboratory to flight test the nonlinear multiple time scale control laws, and then she is staying with VSCL and continuing on to the Ph.D.  Very glad to have you for another degree Jill!

Jill’s research is supported by the Office of Naval Research on the project Novel Multiple Time Scale Adaptive Control for Uncertain Nonlinear Dynamical Systems. Jill’s is the 64^th graduate degree completed that Dr. John Valasek has advised.

Chris Leshikar successfully defended his Ph.D. dissertation on May 28th, 2025.  Chris has been with VSCL since his freshman year in Fall 2016 setting the record for longest duration working in VSCL of 8.83 years. The title of his dissertation is: Markov Parameter Based Methods for System Identification

Chris’s dissertation investigates modifying and extending subspace system identification methods for flight vehicle system identification. The development of accurate dynamical models of flight vehicles is a critical aspect of ensuring overall safety of flight. The development of accurate models using flight data requires the utilization of system identification techniques, which are often denoted as white-box or black-box models. This dissertation develops an approach which extends the Eigensystem Realization Algorithm, a black-box, Markov Parameter based subspace identification method, which permits the inclusion of prior model knowledge, the computation of parameter confidence bounds, and direct identification of continuous-time matrices. This is accomplished by the inclusion of the output model structure which results in a recursive Markov Parameter definition which may be reformulated into the ordinary least squares problem using the Markov Parameters. The effects of process and measurement noise, sampling rate, and data filtering on the developed approach are investigated using a simple second-order system. The theory is further extended for the identification of non-dimensional stability & control derivatives. The benefits of the approach in identifying open-loop models from closed-loop data are also presented. The developed technique is evaluated against standard flight vehicle system identification methods using experimental flight test data of multirotor and fixed-winged Unmanned Air Systems, a fixed-wing manned transport aircraft, and a supersonic commercial transport aircraft.

Chris will do a short postdoc with VSCL and then begin seminary formation for the Catholic Diocese of Victoria later this year. Chris’s research is supported by the National Science Foundation under the Center for Autonomous Air Mobility and Sensors (CAAMS). Chris’s is the 63^rd graduate degree that Dr. John Valasek has advised, and 16th Ph.D. student.

Hannah Lehman successfully defended her Ph.D. dissertation on May 27th, 2025.  Hannah has been with VSCL since her freshman year in Spring 2017, for a total of 8.42 years with VSCL during which she implemented the Theory-Computation-Experiment paradigm. The title of her dissertation is: Hierarchical Auctions for the Coordination of Heterogeneous Agents using Machine Learning

Hannah’s dissertation investigates autonomous multiagent coordination.  Machine learning has long been discussed as a candidate for facilitating autonomous multiagent vehicle coordination. Many methods of autonomous multiagent coordination have been proposed, however few if any solutions consider realistic communication challenges. By using machine learning on multiple levels, and a self organizing hierarchical system, an autonomous, pseudo decentralized, heterogeneous, system can dynamically complete tasks without being fully connected. This approach, called Hierarchical Auctions for the Coordination of Heterogeneous Agents (HACHA) will be investigated and demonstrated on four simple, proof of concept simulations. Each simulation scenario is designed to demonstrate HACHA’s applicability to a different subset of multiagent problems and address specific requirements. Within HACHA, specific algorithm and data choices will be motivated real-world hardware constraints and informed by time complexity analysis of sub-algorithms. Results show that a parallel auction coordination framework can be used to organize multiple heterogeneous agents with different sensors, movement modalities, graph connectedness, and controllers to complete a task requiring multiple agents. The auction framework is independent of individual agents and has been utilized in this paper by a combination of reinforcement learning trained agents and optimally controlled agents to complete tasks. HACHA auction propagation methods are explored and recommended use case rules are developed based on theoretical and computational investigations and results. The HACHA auction choice is explored and compared to other popular auction methods over a variety of relevant network characteristics including dynamicism, sparsity, and number of tasks.

Hannah will be doing a short postdoc with VSCL and then starting full-time at Sandia National Laboratories, where she has now done four graduate internships, in July. Hannah’s is the 62^nd graduate degree advised by Dr. John Valasek and the 15^th Ph.D. student.

VSCL is proud to welcome two new graduate research assistants:

Sadie Binz is a recent graduate of Texas A&M University with a Bachelor of Science in Aerospace Engineering. During her undergraduate studies, she was a member of Sigma Gamma Tau, the Aerospace Engineering Honor Society, and the SAE Aero Design Team, as well as an intern at Bell Helicopter. From this experience, Sadie developed an interest in flight testing and hopes to obtain her private pilot’s license in the future. She has undergraduate research experience in VSCL, primarily in system identification, and is excited to continue researching in VSCL as a graduate student pursuing a A Master of Science degree.

 

 

Raul Santos graduated from Texas A&M University in Spring 2025 with a Bachelor’s in Aerospace Engineering with minors in Computer Science and Mathematics. As an undergraduate, he co-founded the Society of Sonic Flight Engineers and began working with the VSCL as an undergraduate assistant. Raul has interned at Albers Aerospace with their Digital Engineering team as a Systems Engineering Intern, and at the Air Force Research Laboratory as a Safe Autonomy Intern with their Autonomy Capability Team. These experiences have motivated Raul to continue pursuing his interests in flight testing and aerospace autonomy as a graduate assistant researcher at the VSCL, beginning Fall 2025.

Congratulations to the VSCL undergraduate research assistants who graduated with a Bachelor of Science in Aerospace Engineering from Texas A&M University on May 9th 2025!