Variable Fidelity Studies in Wake Vortex Evolution, Safety, and Control

The purpose of this research is to develop a variable-fidelity approach for addressing the safety of unmanned aerial system (UAS) operations in the national aerospace system (NAS). This task is implemented on the basis of safety investigation toolkit for analysis and reporting wake vortex safety system (SITAR WVSS) code, which is a dynamic low-fidelity model addressing generation, evolution, and interaction of the leader-aircraft wake vortex with the follower-aircraft lifting surfaces. The first part of the dissertation deals with the generation, evolution, and interaction of the wake vortices produced by an aircraft. In particular, it presents the results of the vortex safety analysis conducted for selected UAS operating alongside commercial aircraft in the terminal zone. The work further investigates and compares decay and transport of the wake vortex in the vicinity of various grounds including a solid surface, a forest canopy, and a water surface, representative of various terminal zone environments. The obtained high-fidelity results form the basis for reduced-order models to be integrated into the fast-analysis code under development for in-situ wake vortex safety predictions. The second part of the dissertation introduces a robust nonlinear control method that is proven to achieve altitude regulation in the presence of unmodeled external disturbances (e.g. wind gust, wake vortex disturbance) and actuator parametric uncertainty. This method is designed as a part of “Interaction” sub-module of the SITAR WVSS model. The results demonstrate the capability of the proposed nonlinear controller to asymptotically reject wind gust/wake-vortex disturbances and the parametric uncertainty. The proposed controller is a great choice for small UAV applications with limited computational resources

Robust Nonlinear Tracking Control for Unmanned Aircraft in the Presence of Wake Vortex

The flight trajectory of unmanned aerial vehicles (UAVs) can be significantly affected by external disturbances such as turbulence, upstream wake vortices, or wind gusts. These effects present challenges for UAV flight safety. Hence, addressing these challenges is of critical importance for the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), especially in terminal zones. This work presents a robust nonlinear control method that has been designed to achieve roll/yaw regulation in the presence of unmodeled external disturbances and system nonlinearities. The data from NASA-conducted airport experimental measurements as well as high-fidelity Large Eddy Simulations of the wake vortex are used in the study. Side-by-side simulation comparisons between the robust nonlinear control law and both linear H∞ role= presentation style= box-sizing: border-box; max-height: none; display: inline; line-height: normal; font-size: 13.2px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(34, 34, 34); font-family: Arial, Arial, Helvetica, sans-serif; position: relative; \u3eH∞�∞ and PID control laws are provided for completeness. These simulations are focused on applications involving small UAV affected by the wake vortex disturbance in the vicinity of the ground (which models the take-off or landing phase) as well as in the out-of-ground zone. The results demonstrate the capability of the proposed nonlinear controller to asymptotically reject wake vortex disturbance in the presence of the nonlinearities in the system (i.e., parametric variations, unmodeled, time-varying disturbances). Further, the nonlinear controller is designed with a computationally efficient structure without the need for the complex calculations or function approximators in the control loop. Such a structure is motivated by UAV applications where onboard computational resources are limited

On Safety Assessment of Novel Approach to Robust UAV Flight Control in Gusty Environments

In a follow-up to our previous study, the current work examines the gust-induced “cone of uncertainty” in a small unmanned aerial vehicle’s (UAV) flight trajectory addressed in the context of safety assessments of UAV operations. Such analysis is a critical facet of the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), particularly in terminal airspace. The paper describes a predictive, robust feedback-loop flight control model that is applicable to various classes of UAVs and unsteady flight-path scenarios. The control design presented in this paper extends previous research results by demonstrating asymptotic (zero steady-state error) altitude regulation control in the presence of unmodeled vertical wind gust disturbances. To address the practical considerations involved in small UAV applications with limited computational resources, the proposed control method is designed with a computationally simplistic structure, without the requirement of complex calculations or function approximators in the control loop. Proof of the theoretical result is summarized, and detailed numerical simulation results are provided, which demonstrate the capability of the proposed nonlinear control method to asymptotically reject wind gust disturbances and parameter variations in the state space model. Simulation comparisons with a standard linear control method are provided for completeness

Thermal Analysis and Design for VISORS CubeSat Formation

VISORS (Virtual Super-resolution Optics with Reconfigurable Swarms) is a space physics mission for solar corona investigation that will help observe and study the heat release regions. The pair of two formation flying CubeSats containing the observatory and detector will capture the extreme ultraviolet features on the Sun with an unprecedented resolution of 0.2 arcseconds. The strict six-month mission challenges include relative orbit requirements during science observations with several advanced technologies for precise formation flying. For a successful mission, one needs to make sure all the components of the CubeSats\u27 payload meet the thermal requirements. This work performs the thermal analysis of the CubeSat swarm for several mission modes using Thermal Desktop software. Several challenges related to the temperature requirements of specific components are addressed, and solutions are demonstrated

Robust Nonlinear Tracking Control for Unmanned Aircraft in the Presence of Wake Vortex

The flight trajectory of unmanned aerial vehicles (UAVs) can be significantly affected by external disturbances such as turbulence, upstream wake vortices, or wind gusts. These effects present challenges for UAV flight safety. Hence, addressing these challenges is of critical importance for the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), especially in terminal zones. This work presents a robust nonlinear control method that has been designed to achieve roll/yaw regulation in the presence of unmodeled external disturbances and system nonlinearities. The data from NASA-conducted airport experimental measurements as well as high-fidelity Large Eddy Simulations of the wake vortex are used in the study. Side-by-side simulation comparisons between the robust nonlinear control law and both linear H∞ role= presentation style= box-sizing: border-box; max-height: none; display: inline; line-height: normal; font-size: 13.2px; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; color: rgb(34, 34, 34); font-family: Arial, Arial, Helvetica, sans-serif; position: relative; \u3eH∞�∞ and PID control laws are provided for completeness. These simulations are focused on applications involving small UAV affected by the wake vortex disturbance in the vicinity of the ground (which models the take-off or landing phase) as well as in the out-of-ground zone. The results demonstrate the capability of the proposed nonlinear controller to asymptotically reject wake vortex disturbance in the presence of the nonlinearities in the system (i.e., parametric variations, unmodeled, time-varying disturbances). Further, the nonlinear controller is designed with a computationally efficient structure without the need for the complex calculations or function approximators in the control loop. Such a structure is motivated by UAV applications where onboard computational resources are limited

Robust Nonlinear Tracking Control for Unmanned Aircraft in the Presence of Wake Vortex

The flight trajectory of unmanned aerial vehicles (UAVs) can be significantly affected by external disturbances such as turbulence, upstream wake vortices, or wind gusts. These effects present challenges for UAV flight safety. Hence, addressing these challenges is of critical importance for the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), especially in terminal zones. This work presents a robust nonlinear control method that has been designed to achieve roll/yaw regulation in the presence of unmodeled external disturbances and system nonlinearities. The data from NASA-conducted airport experimental measurements as well as high-fidelity Large Eddy Simulations of the wake vortex are used in the study. Side-by-side simulation comparisons between the robust nonlinear control law and both linear H∞ and PID control laws are provided for completeness. These simulations are focused on applications involving small UAV affected by the wake vortex disturbance in the vicinity of the ground (which models the take-off or landing phase) as well as in the out-of-ground zone. The results demonstrate the capability of the proposed nonlinear controller to asymptotically reject wake vortex disturbance in the presence of the nonlinearities in the system (i.e., parametric variations, unmodeled, time-varying disturbances). Further, the nonlinear controller is designed with a computationally efficient structure without the need for the complex calculations or function approximators in the control loop. Such a structure is motivated by UAV applications where onboard computational resources are limited

On Safety Assessment of Novel Approach to Robust UAV Flight Control in Gusty Environments

In a follow-up to our previous study, the current work examines the gust-induced “cone of uncertainty” in a small unmanned aerial vehicle’s (UAV) flight trajectory addressed in the context of safety assessments of UAV operations. Such analysis is a critical facet of the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), particularly in terminal airspace. The paper describes a predictive, robust feedback-loop flight control model that is applicable to various classes of UAVs and unsteady flight-path scenarios. The control design presented in this paper extends previous research results by demonstrating asymptotic (zero steady-state error) altitude regulation control in the presence of unmodeled vertical wind gust disturbances. To address the practical considerations involved in small UAV applications with limited computational resources, the proposed control method is designed with a computationally simplistic structure, without the requirement of complex calculations or function approximators in the control loop. Proof of the theoretical result is summarized, and detailed numerical simulation results are provided, which demonstrate the capability of the proposed nonlinear control method to asymptotically reject wind gust disturbances and parameter variations in the state space model. Simulation comparisons with a standard linear control method are provided for completeness

Robust Nonlinear Tracking Control for Unmanned Aircraft with Virtual Control Surfaces

The flight trajectory of unmanned aerial vehicles (UAVs) can be significantly affected by external disturbances such as turbulence, upstream wake vortices or wind gusts. These effects present challenges in ensuring UAV flight safety. Hence, addressing these challenges is of critical importance for integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), especially in terminal airspace. This paper presents a robust nonlinear control method that can be proven to achieve altitude regulation in the presence of unmodeled external disturbances and actuator parametric uncertainty. Proof of the theoretical result is summarized,and detailed numerical simulations are provided. Side-by-side simulation comparisons with a standard linear control method are provided for completeness. These simulations are focused on applications involving small UAVs equipped with arrays of synthetic jet actuators (SJA). The results demonstrate the capability of the proposed nonlinear controller to asymptotically reject wind gust disturbances and the parametric uncertainty inherent in the SJA model. In addition, the nonlinear controller is designed with a computationally simplistic structure. This computational structure does not require complex calculations or function approximators in the control loop. Hence, the proposed controller is a great choice for small UAV applications with limitedcomputational resources

Robust SJA-Based Nonlinear Trajectory Tracking Control Using Unmanned Aircraft LPV Model

The flight trajectory of unmanned aerial vehicles (UAVs) can be significantly affected by external disturbances such as turbulence, upstream wake vortices or wind gusts. These effects present challenges in ensuring UAV flight safety, and addressing these challenges is of critical importance for integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), especially in terminal airspace. To address these challenges, this paper presents a robust nonlinear control method, which can be proven to achieve reliable UAVtrajectory and altitude regulation in the presence of unmodeled external disturbances and model uncertainty. The proposed control method focuses on applications involving small UAVs equipped with arrays of synthetic jet actuators (SJA). The control design presented in this paper extends previous research results by demonstrating asymptotic (zero steady-state error) altitude regulation control in the presence of unmodeled vertical wind gustdisturbances. To address the practical considerations involved in small UAV applications with limited computational resources, the proposed control method is designed with a computationally simplistic structure, without the requirement of complex calculations or function approximators in the control loop. Proof of the theoretical result is summarized, and detailed numerical simulation results are provided, which demonstrate the capability of the proposed nonlinear control method to asymptotically reject wind gust disturbances and parameter variations in the state space model. Side-by-side simulation comparisons with a standard linear control method are provided for completeness

A non-invasive multipoint product temperature measurement for pharmaceutical lyophilization

Abstract Monitoring product temperature during lyophilization is critical, especially during the process development stage, as the final product may be jeopardized if its process temperature exceeds a threshold value. Also, in-situ temperature monitoring of the product gives the capability of creating an optimized closed-loop lyophilization process. While conventional thermocouples can track product temperature, they are invasive, limited to a single-point measurement, and can significantly alter the freezing and drying behavior of the product in the monitored vial. This work has developed a new methodology that combines non-invasive temperature monitoring and comprehensive modeling. It allows the accurate reconstruction of the complete temperature profile of the product inside the vial during the lyophilization process. The proposed methodology is experimentally validated by combining the sensors’ wirelessly collected data with the advanced multiphysics simulations. The flexible wireless multi-point temperature sensing probe is produced using micro-manufacturing techniques and attached outside the vial, allowing for accurate extraction of the product temperature