In this paper we study identification of discrete time systems using normalized coprime factorization. Robust identifications which agree with robust control theory have been actively investigated in frequency domain and time domain. We have proposed several new identification methods using normalized coprime factorization for time domain identification problems, in which the evaluated functions are given to have relation to the graph topology. In these methods, unknown terms of the identified rational functions, which are caused by I/O data finiteness, are optimally interpolated so that the evaluated functions are minimized. On the other hand, we can show other methods in which the unknown coefficients are approximately equal to 0. According to this idea, we propose some new identification methods using truncated model in this paper. Their algorithms contain iteration of some processes, to solve a linear matrix inequality or the 2-block problem of H∞-norm condition. We also give numerical examples and discuss the effectiveness and the problems of these methods.
This paper discusses the lot scheduling method in a semiconductor fabrication, which is a typical repetitive production process. As for the algorithm to schedule lot operating sequence, simulated annealing (SA) method is applied to this scheduling formulated in the combinatorial optimization problem between machines and silicon wafer lots. To accelerate convergence of SA computation keeping up the solution quality, a new technique for reduction of the problem size and improvement of neighborhood creation are developed. Moreover, in our system, material flow in every process is simulated to consider not only the lot inventory but also the future lot arrival.
This paper is concerned with the zeros of sampled-systems which are composed of a fractional order hold, a continuous-time plant and a sampler in series. The locations of the zeros are investigated when the sampling period tends to zero. Further, the stability conditions of the zeros for sufficiently small sampling periods are derived. The fractional order hold has an advantage to the zero order hold on the stability of the discrete zeros when the relative degree of a continuous-time transfer function is two.
A hydraulic motor servosystem is useful for control of high power and quick response such as drawing control of horizontal continuous casting machine at steel making process. But, it is necessary to accomplish stable control with highspeed. In this paper, the dynamic characteristics of hydraulic motor servosystem is studied by using mathematical models of its components. It is proposed to use a simple bypass valve for getting stable control which is able to damp the hydraulic servosystem. The effectiveness of the proposed method is confirmed by a numerical simulation and an actual experiment.
This paper studies state feedback control of Petri nets under partial observation. We consider the case where a control specification is given in terms of conjunction of component predicates. For such a specification, modular feedback synthesis is useful. We first show that modular synthesis of the unique maximally permissive controller (MPC) is not always possible under partial observation. We then present a necessary and sufficient condition for the unique MPC to be constructed in a modular fashion. Moreover, we demonstrate modular synthesis of the unique MPC for a simple manufacturing system.