<p dir="ltr">To establish a long-term human presence on the Moon, it is necessary to have habitat systems that function effectively under challenging conditions and have sufficient autonomous technologies for fault detection and intervention. However, evaluating these habitats presents challenges due to their pervasive interdependencies and the harsh environmental conditions they must withstand. Thus, innovative testing techniques are vital to understanding and capturing the complexities these systems will encounter. </p><p dir="ltr">Thermomechanical real-time hybrid simulation (RTHS) provides unique opportunities to observe realistic behaviors and interdependencies, train models, test ideas, and validate methods. It is a cost-effective and accessible cyber-physical testing method that allows for the simultaneous experimental and computational modeling of systems, offering a comprehensive observation of their behavior under extreme dynamic conditions. This dissertation presents the development and experimental validation of a novel thermomechanical RTHS method to assess the multi-physics response of lunar habitat systems due to disruptive events. It outlines the conceptual framework, modeling approaches, and experimental considerations crucial to establishing the two-way coupling between a numerical and a physical subsystem through an innovative thermal transfer system. </p><p dir="ltr">The thermal transfer system utilizes a thermal actuator to impose distributed thermal loads on the experimental subsystem. The thermal actuator is identified considering switching-mode continuous dynamics for cooling and heating conditions. A switching control system is then developed to experimentally enforce the desired thermal conditions across different thermal cycles with minimum tracking error, adjusting the gains of the controller in response to varying temperature conditions. Furthermore, this dissertation demonstrates how to establish control and performance requirements for RTHS methods to effectively evaluate the realization of interface boundary conditions and determine acceptance criteria to perform RTHS tests with high confidence. </p><p dir="ltr">The RTHS method is experimentally implemented and validated through a series of scenario tests that simulate the cascading thermomechanical effects on a lunar habitat after a micrometeorite impact that damages its structural protective layer. These realistic tests aim to evaluate fault detection and decision-making methods in response to such disruptive events. Thus, using switching dynamic modeling, the RTHS problem formulation is designed to have numerical damage and repair capabilities, allowing interaction with these fault detection and intervention methods. The scenario results obtained through thermomechanical RTHS reveal behaviors and interactions that are not captured through purely numerical simulation or traditional experimental approaches. Through the experimental implementation of these scenario case studies, the thermomechanical RTHS method developed is the first of its kind to experimentally execute the effects of damage and repair intervention strategies in real-time on a numerical subsystem while simultaneously imposing the cascading effects on a physical specimen. </p><p dir="ltr">The findings of this dissertation advance our knowledge and offer insights into developing cost-effective and accessible cyber-physical methods to test novel ideas and technologies, thereby empowering and supporting space resilience and autonomy research. </p>

<p>  </p> <p>The development of an increasingly interconnected infrastructure and its rapid evolution demands engineering testing solutions capable of investigating realistically and with high accuracy the interactions among the different components of the problem to study. The examination of any of these components without losing the interaction of the other surroundings components is not only realistic, but also desirable. The more interconnected the whole system is, the greater the dependencies. Real-time Hybrid Simulation (RTHS) is a disruptive technology that has the potential to address this type of complex interactions or internal couplings by partitioning the system into numerical (better understood) substructures and experimental (unknown) substructures, which are built physically in the laboratory. These two types of substructures are connected through a transfer system (e.g., hydraulic actuators) to enforce boundary conditions in their common interfaces creating a synchronized cyber-physical system. However, despite the RTHS community has been improving these hybrid techniques, there are still important barriers in their core methodologies. Current control approaches developed for RTHS were validated mainly for linear applications with limited capabilities to deal with high uncertainties, hard nonlinearities, or extensive damage of structural elements due to plasticity. Furthermore, capturing the realistic dynamics of a structural system requires the description of the motion using more than one degree of freedom, which increases the number of hydraulic actuators needed to enforce additional degrees of freedom at boundary condition interface. As these requirements escalate for larger or more complex problems, the computational cost can turn into a prohibitive constraint. </p> <p>In this dissertation, the main research goal is to develop and validate a nonlinear controller with capabilities to control highly uncertain nonlinear physical substructures with complex boundary conditions and its parallel computational implementation for accurate and realistic RTHS. The validation of the proposed control system is achieved through a set of real-time tracking control and RTHS experiments that explore robustness, accuracy performance, and their trade-off </p>

<p>Real-time hybrid simulation (RTHS) has demonstrated certain advantages over conventional large-scale testing. In an RTHS, the system that is under study is partitioned into a numerical and a physical substructure, where the numerical part is comprised of those elements that are easier to model mathematically, while the physical part consists of those that present a complex behavior difficult to capture in a numerical model. The most complex part of this study is the isolation system, a technology used to protect structures against earthquakes by modifying how they respond to ground motions. Unbonded Fiber Reinforced Elastomeric Isolators (UFREIs) are devices that can accomplish this task and have gained attention in recent years because of their modest but valuable features that make them suitable for implementation in low-rise buildings and in developing countries because of their low cost. Our end goal for this work is to enable the testing of scaled versions of these elastomeric isolators to understand their behavior under shear tests and realistic loading. </p> <p>A testing instrument was designed and constructed to apply a uniaxial compressive force up to 22kN and a shear force of 8kN simultaneously to the specimens. A testing program was conducted where four primary sources of signal distortion were identified as caused by the servo-hydraulic system. From these results, a mechanics-based model was developed to understand better the dynamics that the sliding table can introduce to the measured signals accounting for inertial and dissipative forces. Two Bouc-Wen models were implemented to simulate the behavior of the UFREIs. The first only accounts for the hysteretic behavior of the isolator, and the second accounts for the additional nonlinearities found in the isolator’s behavior. These models were assembled in a virtual RTHS which is available to users interested in learning the applications of RTHS of a base-isolated structure with a nonlinear component.</p> <p>An RTHS experiment was conducted in the IISL where the control system comprised a delay compensator and a proportional-integral controller, which exhibited a good tracking performance with minimal delay and low RMSE. However, it can increase the distortion of the oil-column resonance in the measured signals. The simulation captures the behavior of the isolated structure for small displacements. However, it underestimates the displacement of the full-scale specimen for large displacements. The RTHS showed a better approximation of the displacement of the full-scale structure than the theoretical behavior approximated by the Bouc-Wen models.</p>