Xiuyu Gao

Cyber-physical systems for real-time hybrid structural testing: a case study

Real-time hybrid testing of civil structures, in which computational models and physical components must be integrated with high fidelity at run-time, represents a grand challenge in the emerging area of cyber-physical systems. Actuator dynamics, complex interactions among computers and physical components, and computation and communication delays all must be managed carefully to achieve accurate tests. In this paper we present a case study of several fundamental interlocking challenges in developing and evaluating cyber-physical systems for real-time hybrid structural testing: (1) how physical and simulated components can be integrated flexibly and efficiently within a common reusable middleware architecture; (2) how predictable timing can be achieved atop commonly available hardware and software platforms; and (3) how physical vs. simulated versions of different components within a system can be interchanged with high fidelity between comparable configurations. Experimental results obtained through this case study give evidence of the feasibility and efficacy of these steps towards our overall goal: to develop a Cyber-physical Instrument for Real-time hybrid Structural Testing (CIRST).

Towards Configurable Real-Time Hybrid Structural Testing: A Cyber-Physical System Approach

Real-time hybrid testing of civil structures represents agrand challenge in the emerging area of cyber-physical systems. Hybrid testing improves significantly on either purely numerical or purely empirical approaches by integrating physical structural components and computational models. Actuator dynamics, complex interactions among computers and physical components, and computation and communication delays all hamper the ability to conduct accurate tests. To address these challenges, this paper presents initial work towards a Cyber-physical Instrument for Real-time hybrid Structural Testing (CIRST). CIRST aims to provide two salient features: a highly configurable architecture for integrating computers and physical components; and system support for real-time operations in distributed hybrid testing. This paper presents the motivation of the CIRST architectureand preliminary test results from a proof-of-concept implementation that integrates a simple structural element and simulation model. CIRST will have broad impacts on thefields of both civil engineering and real-time computing.It will enable high-fidelity real-time hybrid testing of awide range of civil infrastructures, and will also providea high-impact cyber-physical application for the study andevaluation of real-time middleware.

Computational Tool for Real-Time Hybrid Simulation of Seismically Excited Steel Frame Structures

AbstractReal-time hybrid simulation (RTHS) offers an economical and reliable methodology for testing integrated structural systems with rate-dependent behaviors. Within a RTHS implementation, critical components of the structural system under evaluation are physically tested, while more predictable components are replaced with computational models under a one-to-one timescale execution. As a result, RTHS implementations provide a more economical and versatile alternate approach to evaluating structural/rate-dependent systems under actual dynamic and inertial conditions, without the need for full-scale structural testing. One significant challenge in RTHS is the accurate representation of the physical complexities within the computational counterparts. For RTHS, the requirement for computational environments with reliable modeling and real-time execution capabilities is critical. Additionally, the need of a flexible environment for implementation and easy integration of such platforms with remaining RTHS c...

Experimental Validation of a Generalized Procedure for MDOF Real-Time Hybrid Simulation

AbstractReal-time hybrid simulation (RTHS) has increasingly been recognized as a powerful methodology to evaluate structural components and systems under realistic operating conditions. The concept of RTHS combines the advantages of both numerical analysis and physical laboratory testing. Furthermore, the enforced real-time execution condition enables testing of rate-dependent components. One of the most important challenges in RTHS is to achieve synchronized boundary conditions between computational and physical substructures. The level of synchronization, i.e., actuators tracking performance, largely governs RTHS test stability and accuracy. The objective of this study is to propose and validate a generalized procedure for multiple-degree-of-freedom (MDOF) RTHS. A loop-shaping H∞ robust control design strategy is proposed to control the motion of the actuators. Validation experiments are performed successfully, including the challenges of multiple actuators dynamically coupled through a continuum steel ...

A Real-Time Hybrid Testing Platform for the Evaluation of Seismic Mitigation in Building Structures

Real-time hybrid testing (RTHT) has become a promising alternative to reduce the cost and operational demands when evaluating the performance of damping systems for seismic response attenuation in building structures. While damper devices can be physically tested, buildings can be represented with computational models to avoid the expense of testing a large, integrated specimen. Therefore, reliable simulation tools are needed to accurately recreate the behavior of the computational component under real-time execution demands; also, appropriate control schemes for testing the experimental component using hydraulic actuators are required for high fidelity RTHT implementation. In this paper, a novel RTHT platform appropriate for the study and evaluation of damped buildings is presented. The main components of the platform are described, including the computational tool for performing non-linear dynamic analysis of steel frames and the advanced robust control strategy for the hydraulic actuators. Additionally, initial results of a validation experiment using a re-configurable steel moment-resisting frame are presented to demonstrate the accuracy and efficiency of the proposed RTHT framework.

Experimental validation of a scaled instrument for Real-Time Hybrid Testing

A highly reconfigurable cyber-physical Real-time Hybrid Test (RTHT) instrument is under development that is particularly suitable for Civil Engineering structural control testing applications. The instrument serves as a testbed for studying structural system behavior under dynamic loading and associated vibration mitigation control techniques. The focus of this paper is to validate the developed framework experimentally regarding both its accuracy and efficiency in conducting RTHT. A MATLAB-based nonlinear finite element simulation tool, designed to predict seismically excited non-linear building response, is used as an analytical substructure, with a magneto-rheological (MR) damper as a physical substructure. A model based control scheme is adopted to compensate for de-synchronization between substructure interfaces caused by hydraulic actuator dynamics. The RTHT is then conducted for both passive and semi-active MR damper control cases, the results of which show an excellent match between RTHT and pure numerical simulation outputs, thus demonstrating the effectiveness of the prototype instrument.

The Design and Performance of Cyber-Physical Middleware for Real-Time Hybrid Structural Testing

Real-time hybrid testing of civil structures, in which computational models and physical components must be integrated with high fidelity at run-time represents a grand challenge in the emerging area of cyber-physical systems. Actuator dynamics, complex interactions among computers and physical components, and computation and communication delays all must be managed carefully to achieve accurate tests. To address these challenges, we have developed a novel middleware for integrating cyber and physical components flexibly and with suitable timing behavior within a Cyber-physical Instrument for Real-time hybrid Structural Testing (CIRST). This paper makes three main contributions to the state of the art in middleware for cyber-physical systems: (1) a novel middleware architecture within which cyber-physical components can be integrated flexibly through XML-based configuration specifications, (2) an efficient middleware implementation in C++ that can maintain necessary real-time performance, and (3) a case study that evaluates the middlewares performance and demonstrates its suitability for real-time hybrid testing. Type of Report: Other Department of Computer Science & Engineering Washington University in St. Louis Campus Box 1045 St. Louis, MO 63130 ph: (314) 935-6160 The Design and Performance of Cyber-Physical Middleware for Real-Time Hybrid Structural Testing Huang-Ming Huang, Xiuyu Gao, Terry Tidwell, Christopher Gill, Chenyang Lu, Shirley Dyke Department of Computer Science and Engineering {hh1, ttidwell, cdgill, lu}@cse.wustl.edu Department Mechanical, Aerospace, and Structural Engineering xg2@cec.wustl.edu, sdyke@wustl.edu Washington University, St. Louis, MO, USA Abstract—Real-time hybrid testing of civil structures, in which computational models and physical components must be integrated with high fidelity at run-time represents a grand challenge in the emerging area of cyber-physical systems. Actuator dynamics, complex interactions among computers and physical components, and computation and communication delays all must be managed carefully to achieve accurate tests. To address these challenges, we have developed a novel middleware for integrating cyber and physical components flexibly and with suitable timing behavior within a Cyber-physical Instrument for Real-time hybrid Structural Testing (CIRST). This paper makes three main contributions to the state of the art in middleware for cyber-physical systems: (1) a novel middleware architecture within which cyber-physical components can be integrated flexibly through XML-based configuration specifications, (2) an efficient middleware implementation in C++ that can maintain necessary real-time performance, and (3) a case study that evaluates the middleware’s performance and demonstrates its suitability for real-time hybrid testing.Real-time hybrid testing of civil structures, in which computational models and physical components must be integrated with high fidelity at run-time represents a grand challenge in the emerging area of cyber-physical systems. Actuator dynamics, complex interactions among computers and physical components, and computation and communication delays all must be managed carefully to achieve accurate tests. To address these challenges, we have developed a novel middleware for integrating cyber and physical components flexibly and with suitable timing behavior within a Cyber-physical Instrument for Real-time hybrid Structural Testing (CIRST). This paper makes three main contributions to the state of the art in middleware for cyber-physical systems: (1) a novel middleware architecture within which cyber-physical components can be integrated flexibly through XML-based configuration specifications, (2) an efficient middleware implementation in C++ that can maintain necessary real-time performance, and (3) a case study that evaluates the middleware’s performance and demonstrates its suitability for real-time hybrid testing.