Our group has already studied a position control system for flexible link robot arms. The control law of this method is natural extension from the computed torque method for a rigid link robot arm. It is not limited within operating range which can be regarded as a linear system. In addition, it does not require a switching like an input used in a sliding mode control. However, we need to consider the modeling error because this method uses the model based control. In this paper, we propose a new position control of 2DOF flexible link robot arms based on computed torque method. In addition, we theoretically investigate the stability of the proposed method. Moreover, we propose a simple adaptive identification method in order to decrease the modeling error. The validity of the proposed scheme is illustrated by the theoretical analysis and experimental results.
Reliable estimation of surface fault displacements is crucial to the safety of nuclear power plant facilities. It is necessary to develop a numerical method for the estimation. In the study, we develop a finite element method in which the following two functions are implemented: (1) a symplectic time integration of an explicit scheme to properly conserve the energy of the system; and (2) rigorously formulated joint elements of high order. The finite element method is enhanced with parallel computing capability. We apply the developed method to solve simple three-dimensional models of faults embedded in a rock mass. It includes a comparison of results from quasi-static and dynamic simulations and investigation of the sensitivity of results to the shear stiffness on faults. In the study, we propose capacity computing with a quasi-static simulation for uncertainty quantification.
Previous studies on the modelling of coupled thermo-hydro-mechanical (THM) processes in bentonite-based engineered barrier systems (EBSs) showed the sensitivity of the output quantities to changes in the input parameters. To investigate the effects of uncertainties on the modelling results, to improve the understanding of the coupled processes active in the repository near field and to gain in-depth understanding of model uncertainties of different codes, a sensitivity analysis and code comparison of EBS simulations was performed within the Task Force on Engineered Barrier Systems. The analysis included variations in material parameter values, boundary and initial conditions, considered physical processes and model geometries, amounting to 60 different cases. This in-depth analysis helped evaluate the influence of parameter and conceptual uncertainties on the results of coupled THM simulations and to identify key parameters and processes. The cross-code comparison encouraged a fruitful exchange among modelling teams and led to very good agreements between the results of the different codes. Serving as a benchmark example for THM-coupled simulations of bentonite-based EBSs, the study helped increase the confidence in the modelling capabilities of several codes used for safety evaluations of repositories for spent fuel and high-level radioactive waste.
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