An electro-hydraulic shaking table is a useful experimental apparatus to real-time replicate the desired acceleration signal for evaluating the performance of the tested structural systems. The article proposes a combined control strategy to improve the tracking accuracy of the electro-hydraulic shaking table. First, the combined control strategy utilizes an adaptive inverse control as a feedforward controller for extending the acceleration frequency bandwidth of the electro-hydraulic shaking table when the estimated plant model may be a nonminimum phase system and its inverse model is an unstable system. The adaptive inverse control feedforward compensator guarantees the stability of the estimated inverse transfer function. Then, the combined control strategy employs an improved internal model control for obtaining high fidelity tracking accuracy after the modeling error between the estimated inverse transfer function using adaptive inverse control and the electro-hydraulic shaking table actual inverse system is improved by the improved internal model control. So, the proposed control strategy combines the merits of adaptive inverse control feedforward compensator and improved internal model control. The combined strategy is programmed in MATLAB/Simulink, and then is compiled to a real-time PC system with xPC target technology for implementation. The experimental results demonstrate that a better tracking performance with the proposed combined control strategy is achieved in an electro-hydraulic shaking table than with a conventional controller.
A new analytical method for springback of small curvature plane bending is addressed with unloading rule of classical elastic-plastic theory and principle of strain superposition. We start from strain analysis of plane bending which has initial curvature, and the theoretic derivation is on the widely applicable basic hypotheses. The results are unified to geometry constraint equations and springback equation of plane bending, which can be evolved to straight beam plane bending and pure bending. The expanding and setting round process is one of the situations of plane bending, which is a bend-stretching process of plane curved beam. In the present study, springback equation of plane bending is used to analyze the expanding and setting round process, and the results agree with the experimental data. With a reasonable prediction accuracy, this new analytical method for springback of plane bending can meet the needs of applications in engineering. plane bending, springback, geometry constraint equations, springback equation, the expanding and setting round process Citation: Zhao J, Yin J, Ma R, et al. Springback equation of small curvature plane bending.
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