Mathematical Framework for Real-Time Hybrid Substructuring of Marine Structural Systems

In hybrid substructuring, a structural system is partitioned into a numerical substructure and a physical substructure. Typically, the physical substructure consists of a system component whose behavior is difficult to model while the numerical substructure consists of a computational model of the remainder of the system. Hybrid substructuring has previously been shown to be an effective method to quantify the effect of parametric uncertainties in the numerical substructure on the response of the system. This paper proposes and implements a methodology where the effect of parametric uncertainty can also be incorporated into the physical substructure. This idea is implemented in a series of small-scale Real-Time Hybrid Substructuring (RTHS) tests on a magneto-rheological fluid damper used to control a two degree-of-freedom mass-spring system. The physical current supplied to the damper is treated as a random variable. Using the RTHS test results, a metamodel of the system’s frequency domain behavior is developed using Principal Component Analysis and Kriging. This metamodel is then used to evaluate probabilistic system performance.

In recent years, both pseudo-dynamic and real time heterogeneous testing with dynamic substructuring — hybrid testing — have gained significant popularity for their applicability to testing several types of nonlinear structures/systems. In a hybrid test, a heterogeneous model of the emulated system is created by combining a Physical Substructure (PS) with a Numerical Substructure (NS) that describes the remainder of the system. Nevertheless, an efficient implementation of this technique requires overcoming certain problems, e. g., proper dynamic substructuring, reduction of external forces and actuator delay compensation. This paper presents a pseudo-dynamic test campaign undertaken by the University of Trento, Italy, on a typical full-scale industrial piping system subjected to earthquake loading in order to investigate its seismic performance. Some challenges faced during the implementation are shown and strategies adopted to overcome these problems are illustrated. Experimental activities will be described and performances of different components of the piping system, i.e., elbows, tee-joints, bolted flange joints and straight pipes under earthquake loading with the presence of an internal pressure of 3.2 MPa will be presented and commented.

Reactive power is related to the type of power that does not consume energy but stores it. In the design of test machines, the utilization of this physical phenomenon would be very beneficial. Reactive power allows for the combination of power amplification with energy savings, making it an ideal principle for conducting long-term tests that involve high loads and prolonged energy consumption. This work focuses on testing machines operating in resonance, which allows for higher test frequencies and reduced test durations. Various types of fatigue testing machines, including those with rotating-unbalance actuators, servo-hydraulic actuators, and piezoelectric actuators, are examined through vibration analysis, methodical design, and mechatronics. Resonant testing machines provide significant advantages in energy efficiency and test accuracy for a wide range of applications in materials testing. These methods are crucial for future applications in industries where energy efficiency and precise fatigue testing are critical, such as aerospace, automotive, and civil engineering.

Chapter 5 - The role of accurate simulation in the development of accelerated testing in automotive and aerospace engineering, and its connection with the engineering culture

Numerical substructures adopt predetermined hysteretic models for conventional substructure testing (CST). It is difficult to achieve accurate results in CST due to errors from modelling of numerial substructures. To diminish the negative effect caused by the assumed restoring model, online identification with least square method using experimental data was adopted to update the model of numerical substructure. The effectiveness of least square method are verified with pseudo-dynamic substructure testing for single story frame with a buckling-restrained brace. The results indicate that the on-line identification algorithm based least square method has good accuracy, stability, and efficiency.

Dynamically substructured system testing method divides an original system into several substructures. In the numerical substructure, linear components are simulated via real-time computation. In the physical substructure, a transfer system, which includes actuators and sensors, is installed to interface the numerical and physical parts. During the test, the unwanted disturbances and noise from the actuator inevitably cause synchronization errors between the outputs of numerical and physical substructures at the interface, and consequently result in unsuccessful tests. Therefore, this study proposes advanced control using the feedforward state-space linear substructuring controller plus the mixed H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> feedback controller to ensure optimal and robust synchronization. The synchronization problem is transformed to tracking design according to a numerical-substructure-based framework and is solved based on Riccati-like equations and linear matrix inequality. A multivariable mass-spring-damper substructured system is developed to verify the proposed control strategy via numerical studies.

In the dynamically substructured system (DSS) testing technique, a controller that synchronises the responses of physical and numerical substructures is an essential part of the testing scheme to ensure synchronisation fidelity. This paper discusses a novel approach that generates a two-degree-of-freedom (2-DOF) output feedback controller for multi-input, multioutput (MIMO) DSS via control synthesis. This 2-DOF output feedback controller yields robust stability and robust performance of the physical/numerical substructure synchronisation and enables controller tuning in the frequency domain. Simulation and experimental results have been shown to validate the efficacy of the method.

The active control technology was carried out on the marine diesel two-stage vibration isolation system (MDTVIS); the active control technology was able to make up for passive vibration isolation technology in the low-frequency range. The construction of a secondary path was one of the most important sectors, which had a full impact on active vibration isolation performance. Nonlinear components comprised the secondary path, which were principally the nonlinear vibration of multi-degrees of freedom in the practical MDTVIS and the nonlinear control path in the hydraulic servo actuator. The nonlinearity was not ignorable in coping with the second path, so that the vibration isolation performance was greatly influenced by the secondary path in the active control technology with the classic adaptive comb-type filter. By combining the model reference adaptive inverse control strategy with the nonlinear robust control technology, the linearity control algorithm was designed, and then the classic adaptive comb-type filter algorithm was carried out for the new system; herein the hybrid control strategy was constructed to apply to the secondary path in the practical MDTVIS. The proposed hybrid control strategy was able to improve the initial active vibration isolation control algorithm with an adaptive comb-type filter and overcome shortcomings of the vibration strengthened in some multi-harmonic-frequency sites in the low-frequency range. The total performance of vibration isolation coupling with multi-path was improved in balance.

To meet stringent Euro-6 emission regulations, a lean NOx trap (LNT) catalyst should be considered to effectively abate NOx emissions. This LNT catalyst should be periodically regenerated without deteriorating driving quality and also satisfy emission constraints, such as CO, low particulate matter or smoke, and low O2 during the regeneration phase. As a means of reductant delivery, in-cylinder post fuel injection with a feedforward (FF) control has been applied due to its simple implementation in an engine management system (EMS). However, with this method, it is difficult to satisfy the driving quality and emission constraints during the transition to or out of the regeneration phase. To solve this problem, we propose a novel LNT regeneration control method using an indicated mean effective pressure (IMEP) and a combustion lambda feedback (FB) control combined with the FF control. For the precise FB control of the post injection timing, among the location of the second rate of heat release (ROHR) peak, the magnitude of the second ROHR peak, and IMEP, the IMEP was selected as a control parameter because of its lowest cyclic variation. In addition, the exhaust lambda control was applied for the accurate FB control of the post injection quantity. The proposed method was implemented in an in-house EMS. The performance in several engine tests indicated that the torque fluctuation was minimized and all emission constraints were effectively satisfied. Furthermore, this method was also robust with regard to the thermal disturbance.

Neural prosthetic systems seek to improve the lives of severely disabled people by decoding neural activity into useful behavioral commands. These systems and their decoding algorithms are typically developed "offline," using neural activity previously gathered from a healthy animal, and the decoded movement is then compared with the true movement that accompanied the recorded neural activity. However, this offline design and testing may neglect important features of a real prosthesis, most notably the critical role of feedback control, which enables the user to adjust neural activity while using the prosthesis. We hypothesize that understanding and optimally designing high-performance decoders require an experimental platform where humans are in closed-loop with the various candidate decode systems and algorithms. It remains unexplored the extent to which the subject can, for a particular decode system, algorithm, or parameter, engage feedback and other strategies to improve decode performance. Closed-loop testing may suggest different choices than offline analyses. Here we ask if a healthy human subject, using a closed-loop neural prosthesis driven by synthetic neural activity, can inform system design. We use this online prosthesis simulator (OPS) to optimize "online" decode performance based on a key parameter of a current state-of-the-art decode algorithm, the bin width of a Kalman filter. First, we show that offline and online analyses indeed suggest different parameter choices. Previous literature and our offline analyses agree that neural activity should be analyzed in bins of 100- to 300-ms width. OPS analysis, which incorporates feedback control, suggests that much shorter bin widths (25-50 ms) yield higher decode performance. Second, we confirm this surprising finding using a closed-loop rhesus monkey prosthetic system. These findings illustrate the type of discovery made possible by the OPS, and so we hypothesize that this novel testing approach will help in the design of prosthetic systems that will translate well to human patients.

Al-Alkhalaf: the evolution of the urban built-form of a traditional settlement in Southwestern Saudi Arabia

The torsional vibration of the engine is the important factor which leads to noise and has impact on the ride comfort and stability of the vehicle. In the 21st century, under the theme of energy-saving, environmental protection and noise reduction, people pay more attention to diesel engine with the strict requirements increasingly. On the basis of discussing the mechanism of torsional vibration and its harm, the paper explores the torsional vibration testing methods of a new type of diesel engine at idle condition. By building the diesel engine test bench and constructing torsional vibration test platform based on virtual instrument, we get the status of the engine's torsional vibration through the signal processing and analysis. So it provides a certain reference to the engine manufacturing, testing and evaluation.

OPAL-RT enables the simulation of large-scale, complex systems efficiently. Systems that would typically require hours or even days to simulate on a conventional personal computer can be executed in real time using OPAL-RT, with time steps in the microsecond or nanosecond range. High performance, flexibility, and low entry-level cost are key attributes of the OPAL-RT platform. The OPAL-RT real-time simulation platform is an advanced model-based engineering design and testing environment. It delivers outstanding real-time performance for experimental studies and is widely used in engineering design applications. Therefore, it is essential to examine its hardware architecture, software structure, and real-time performance in detail. A comprehensive understanding of its hardware and software architecture, along with its simulation process, provides a structured overview of the platform. Furthermore, the application of OPAL-RT in electrical power systems serves as a valuable reference for microgrid, smart grid, and other real-time system implementations

Offshore compliant structures such as guyed platforms, tension leg platforms and articulated towers are economically attractive for deep water conditions because of their reduced structural weight compared to conventional platforms. The foundations of these kinds of structures do not resist lateral environmental loads forces; instead, restoring moments are provided by a large buoyancy force, a set of guylines or a combination of both. These structures have a fundamental frequency well below the ocean wave’s lower frequency-bound. As a result of the relatively large displacements, geometric nonlinearity is an important consideration in the analysis of such a structure. This paper presents a literature review on offshore compliant structures. The review focuses on the static and dynamic response of the structure due to various environmental conditions, such as wind, waves and current. Emphasis is placed on modeling techniques and methods of solution. Many modeling and analysis techniques are common to the aerospace and ocean engineering communities due to the similarities in structural and environmental complexities. For example, aerodynamic loads on offshore platforms are a significant part of any analysis. Also, fluid loading models bear great similarities to mechanistic wind loading models. It is in this vein that a review paper with the focus on offshore structures is included in a journal of aerospace engineering.

&lt;div class="htmlview paragraph"&gt;Although many of the larger engineering schools tend to specialize in their programs and emphasize graduate school research and development, there exists today a demand for training in basic engineering skills. Since the technology graduate is the general practitioner of engineering, the School of Technology assumes particular importance.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;In the aerospace or aviation industry, the qualified graduate should be able to find employment in the areas of design, manufacturing, or operations. Design includes preliminary layout, stress analysis, test engineering, or materials engineering; manufacturing encompasses quality control, production process, scheduling and planning, liaison and field engineering, or perhaps personnel; and operations includes actual piloting or flight instruction, airport operation and management, aircraft maintenance, and traffic control.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;The well-planned aerospace technology program is designed to serve the interests of the student and industry in these three general areas. The graduate is not so constrained that he must specialize in any one area, but has sufficient background to enter into, and be competent in, any of them. It is assumed, of course, that on-the-job training is available to develop a maximum competence in any one area.&lt;/div&gt;