Continuous-time system representation with exact macro-difference expressions

A macro-difference equation representation is proposed which is a mixture of finite-difference quotients and integrals over finite time intervals. The choice of the micro or sampling interval length (for the numerical integration accuracy and representation bandwidth) and the choice of the macro interval length (for numerical conditioning/accuracy of the difference quotients and of the resulting equations) are independent. This approach does not need the assumption (which in practical situations is quite unnatural) of zero initial conditions.     

Feedback controller design for plants with modes and disturbances above the sampling frequency

The digital feedback controller design technique of Eitelberg (1988) could not treal closed-loop performance accurately if the continuous-time plan. had significant models and signals above the sampling frequency. Here, the above simple techinque's applicability is extended by implementing the controller with additional analogue low-pass filters, cancelled by digital ‘high-pass’ terms at or below the sampling frequency.     

Photoelectric properties of MISM phthalocyanine structure

Langmuir-Blodgett films have been prepared from copper tetra-4-t-butylphthalocyanine. A voltage dependence of capacitance can be attributed to the presence of a Schottky depletion layer. The barrier potential was determined as l·4eV, and the carrier concentration about 10²⁴m^?3     

State-space for non-linear algebraically constrained dynamical systems

Non-linear state differential equations x = f(x, u) with algebraic constraints g(x, u, e) = 0, e = e (t), which describe possibly singular systems, are considered. The derivation of equivalent unconstrained state differential equations x* = f* (x*, e, ?,...), {x* }c:{x} ≥ {x} with the ‘ output’ equations u = h*(x*, u*, e, ?,…) and x equals; h* * (x*, e, ?…) is studied. Instead of an extension of the linear matrix-oriented singular system theory, the non-linear system inversion ideas are found to be easily applicable, to preserve much of the original system structure, and to give insight into the possibly distributional behaviour of and the possible incompatibilities in the system.     

Sampling rate design based on (1 − sT/2)

A digital controller design technique must yield all controller parameters, including the sampling rate 1/T, as functions of (continuous-time) specifications. It will be shown that, under certain conditions, sampling is modelled by a continuous-time (1 -sT/2) in the loop transfer function.     

Pole-zero cancellation in discrete-time transfer functions

Discrete-time transfer function simplification by approximate pole-zero cancellation is investigated. Two equivalent ‘rules of thumb’ are derived, which are different from the continuous-time case.     

AN INDIRECT BOUNDARY ELEMENT METHOD FOR PLATE BENDING ANALYSIS

An indirect Boundary Element Method is employed for the static analysis of homogeneous isotropic and linear elastic Kirchhoff plates of an arbitrary geometry. The objectives of this paper consists of a construction and a study of the resulting boundary integral equations as well as a development of stable powerful algorithms for their numerical approximation. These equations involve integrals with high-order kernel singularities. The treatment of singular and hypersingular integrals and a construction of solutions in the neighborhood of the irregular points on the boundary are discussed. Numerical examples illustrate the procedure and demonstrate its advantages. © 1997 by John Wiley & Sons, Ltd.