Multipurpose controller design using parametric optimization with dynamic constraints

A systematic and effective design procedure for a class of linear multivariable feedback control systems is proposed For simultaneously achieving robust tracking of the prescribed input signal via the Q-parametrization approach and internal model principle, the prescribed transient specifications by choosing an appropriate performance criterion, robust stabilization, and sensitivity minimization. The problem can best be cast in the form of an optimization problem with dynamic constraints. A numerical method is formulated to solve the optimization problem with dynamic constraints using a non-linear programming method. A numerical example is provided to illustrate the main results of the paper.     

Application of the Persidskii theorem to non-linear system stabilization via dynamic output feedback

We consider the stabilization problem in the sense of Lyapunov of a class of ‘k-bounded’ non-linear systems via dynamic output feedback, where the non-linearities of the systems are not necessarily continuously differentiable but satisfy ‘k-bounded’ conditions. The factorization theory of linear systems and the quasi-stability result of Persidskii are combined to provide such a dynamic output feedback scheme.     

Strategies for scalable symbolic execution-driven test generation for programs

With the advent of advanced program analysis and constraint solving techniques,several test generation tools use variants of symbolic execution.Symbolic techniques have been shown to be very effective in path-based test generation;however,they fail to scale to large programs due to the exponential number of paths to be explored.In this paper,we focus on tackling this path explosion problem and propose search strategies to achieve quick branch coverage under symbolic execution,while exploring only a fraction...     

Gelation behaviour of UHMWPE/camphene

The sol–gel transition behaviour of ultra-high molecular weight polyethylene (UHMWPE) in decalin, paraffin oil and camphene has been investigated. UHMWPE solutions exhibit a thermo-reversible gelation, recognized in gels, which is due to crystallization. Viscosity results indicated that polymer molecules disentangled more easily when camphene was used as a solvent. This characteristic implies that camphene is a more desirable solvent for solution processing of UHMWPE. A higher recrystallization temperature, Tc, also occurred at a higher gelation temperature, Tgel. The gel melting temperature, Tm,gel, was also measured and its dependency on polymer concentration was investigated using the Eldridge–Ferry equation. The reciprocal of the absolute gel melting temperature was found to have a linear relationship with the logarithm of polymer concentration     

Structural synthesis of ancient Chinese foot-operated silk-reeling mechanism

This work synthesizes the structures of the foot-operated silk-reeling mechanism, which was vaguely depicted in many literatures in ancient China. Based on the analysis of the mechanism, the structural characteristics and design constraints of the mechanism with indeterminate links and joints are concluded. Then, according to the concepts of generalization and specialization subject to the concluded design constraints, all feasible structures of the mechanism that met the technological standards of the subject’s time period are reconstructed. This reconstruction process provides a logical foundation to better understanding, clarification, and suggestions for the issue of ancient mechanical drawings with indeterminate links and joints.     

AN EXPERIMENTAL OBSERVATION OF A SOLITARY WAVE IMPINGE-MENT,RUN-UP AND OVERTOPPING ON A SEAWALL

A sequence of laboratory experiments using solitary waves was performed to model the effect of leading form of three types of tsunamis(a bore,an impinging wave and an overtopping wave)on a seawall on a sloping beach.The wave evolution process,impinging pressure along the seawall surface,total overtopping discharge behind the seawall and the maximum run-up height on the rear slope were measured and compared.Laboratory data were employed to re-examine relevant empirical formulae in the literature.The effect of the presence of the seawall in reducing maximum run-up height using the present setup was briefly discussed.The present data can be used for calibrating numerical and mathematical models.     

Robust LQG optimal controller design for multivariable discrete saturating systems with noise spectral uncertainties and non-linear time-varying unmodelled dynamics

A design procedure is proposed for robust linear-quadratic-gaussian (LQG) optimal controller synthesis against noise spectral uncertainties, non-linear time-varying (NLTV) unmodelled dynamics in discrete saturating systems. A robust stability criterion is derived for multivariable stochastic discrete-time systems with NLTV unmodelled dynamics and constrained actuators. An algorithm based on the robust stabilization creterion is presented for synthesing a robust controller not only to minimize the least favourable cost functional but also to satisfy the robust stabilization criterion by specifying an appropriate weighting scalar in the cost functional. A necessary and sufficient condition for the solvability of such a robust stabilization problem is derived by means of the Nevanlinna-Pick interpolation theory. The Wiener Z-domain solution for controller synthesis, the saddle point theory, and the properties of Schur operator (Class S) are employed to treat this problem. Finally, a numerical example is given to illustrate the results.     

Robust controller synthesis in non–linear multivariable systems: using dither as auxiliary

A dither is a high frequency signal introduced into a non-linear system in order to improve its performance. It is shown that the stability of a dithered system can be predicted rigorously by establishing the stability of its corresponding smoothed system when the dither has a sufficiently large amplitude as well as high–enough frequency, and the transfer function of the ‘linearized’ feedback system has a high-frequency attenuation property. A generally parametrized controller, advanced by Youla et al., and a dither as its auxiliary are simultaneously introduced to augment the stability of the non–linear feedback system, where the controlled plant are not necessarily stable. The main feature of this study is that the technique of robustness optimization is used to find a lower bound on the dither amplitude for stabilization of the non–linear feedback system. Furthermore, there arc no stable, square, and minimum-phase constraints on the controlled plant.