Pei-Ching Chen

Adaptive model-based tracking control for real-time hybrid simulation

Model-based feedforward–feedback tracking control has been shown as one of the most effective methods for real-time hybrid simulation (RTHS). This approach assumes that the servo-hydraulic system is a linear time-invariant model. However, the servo-control closed-loop is intrinsically nonlinear and time-variant, particularly when one considers the nonlinear nature of typical experimental components (e.g., magnetorheological dampers). In this paper, an adaptive control scheme applying on a model-based feedforward–feedback controller is proposed to accommodate specimen nonlinearity and improve the tracking performance of the actuator, and thus, the accuracy of RTHS. This adaptive strategy is used to estimate the system parameters for the feedforward controller online during a test. The robust stability of this adaptive controller is provided by introducing Routh’s stability criteria and applying a parameter projection algorithm. The tracking performance of the proposed control scheme is analytically evaluated and experimentally investigated using a broadband displacement command, and the results indicates better tracking performance for the servo-hydraulic system can be attained. Subsequently, RTHS of a nine-story shear building controlled by a full-scale magnetorheological damper is conducted to verify the efficacy of the proposed control method. Experimental results are presented for the semi-actively controlled building subjected to two historical earthquakes. RTHS using the adaptive feedforward–feedback control scheme is demonstrated to be effective for structural performance assessment.

Dynamics, control and real-time issues related to substructuring techniques: application to the testing of isolated structure systems

This article presents the designs of output-based adaptive and numerical-substructure-based controllers for the testing of a base-isolated substructured system. The linear numerical-substructure-based controllers, which are developed using state-space and transfer-function methods and a higher-order actuator model, are introduced in order to address new substructured eigenvalue techniques in relation to testing stability and accuracy. An output-based framework for the synthesis of new adaptive substructuring controllers and for the associated stability proof is discussed, based upon an ad hoc reference model concept. Implementation studies favourably verify the proposed control and analysis strategies, showing that the adaptive controller effectively compensates for time-varying and unwanted parameters within the actuator systems, and using the substructured eigenvalue can explicitly predict the testing performance in advance. In addition, the results also indicate that a feedforward controller incorporating closed-loop control schemes could be disadvantageous if the numerical substructure contains the dynamic parameters, which possibly may yield slow substructured eigenvalues.

Axial Performance of Various Strengthening Methods Applied on Full-Scale Rectangular RC Columns

The performance of RC columns subjected to axial force is relative to the confinement. CFRP wrapping, a generally adopted retrofit method, was proved not to effectively provide confining force due to the bulging effect on the column face. Therefore, this paper is focused on the performance of the retrofitted full-scale rectangular RC columns using different retrofit schemes including the proposed CFRP wrapping conjugated with CFRP anchors method. A total of eleven rectangular RC columns with low transverse reinforcement ratio were constructed. Among them, one was tested as benchmark; one was purposely constructed with larger transverse reinforcement ratio; five were retrofitted by using CFRP wrapping and CFRP anchors; and the other four were retrofitted by using different shapes of steel jacketing alone or with adhesive anchors. All the specimens were subjected to monotonic incremental axial force until failure occurred. Experimental results demonstrated that the ductility of the specimens retrofitted by using CFRP wrapping with CFRP anchors was significantly improved compared with those retrofitted by using only CFRP wrapping. On the other hand, the specimen with octagonal steel jacketing performed better than all other specimens not only on ductility but also on strength. Finally, a novel numerical model considering the contribution of the retrofit material will be proposed and validated in the future.