Nonstationary Parts Research Articles

The On-Line Solidification Control in the Continuous Casting Process

For the solidification control in the continuous casting machine of slabs and/or blooms, two on-line control models -- the surface temperature pattern control and the crater end control -- have been developed in Nippon Steel Corporation. The surface temperature pattern control model can estimate the on-line solidification pattern and control the secondary cooling optimally. The crater end control model can move or keep the complete solidification point to the target area. The surface temperature pattern control model has improved the surface quality of non-stationary casting parts of slabs and blooms and these two models have been found useful for the establishment of the stable production of high-temperature castings suitable for direct-rolling and hot charging processes.

On LQ Optimum Control Of Armax Processes

A new method of LQ optimum control design for ARMAX processes is presented. It operates in time domain and solves the problem for finite control horizon but at the same time makes it possible to determine the stationary control law, to which the solution converges for growing control horizon, in terms of polynomial equations. The solution of the standard Ricatti equation is replaced by sequential factorization and de-composition of certain band matrices. This leads to efficient and numerically stable algorithms. Unlike the polynomial theory, the stationary solution obtained is unique (if it exists) and optimal also for transient and nonstationary parts of the control process. Both regulation and servo problems are considered.

Theory for hydroacoustic multiple target scattering assessment with experimental verification

A new formulation for hydroacoustic scattering is presented. An average target density is defined assuming that for each aggregation of N scatterers, an ensemble of configurations is possible. Each configuration gives rise to an unique reflected signal which is input to a linear time invariant bandlimited system and the output or observable signal is processed to determine N. The problem is formulated as a nonstationary stochastic process with the autocorrelation function of the input process being derived and shown to consist of stationary and nonstationary parts. Then the energy spectrum of the output process is determined using a two-dimensional Fourier transform and linear system theory. The developed theory is compared with experimental data obtained in an elaborate test conducted by NMFS Fisheries Engineering Laboratory at Bay Saint Louis, Mississippi. Calculated target densities are found to lie within 89% confidence limits based on Tchebycheff's inequality.