Control by linearization of nonlinear system has been in focus and widely accepted by the control system experts. Dynamic model of Three Phase Horizontal Gravity Separator (TPHGS) has nonlinear characteristics. Various control techniques have been proposed to control TPHGS. In this paper approximate linearization technique due to Kang and Krener is applied to linearize the nonlinear system. TPHGS is described by nonlinear differential equations. A transformation of variables leads to state equations describing TPHGS. Considering deviation about set points of variables, a control affine system is derived. Approximate linearization in the form of quadratic linearization is applied to the control affine system describing the TPHGS. The linear equations involving the coordinate and input transformation coefficients are solved. Application of input and coordinate transformation leads to a linear system with third and higher order nonlinearities. A realistic numeric example together with a simulation illustrates the application of quadratic linearization. Approximate linearization avoids the zero dynamics which may arise in exact feedback linearization.

Digital communications started replacing analogue signal transmissions when smart transmitters were implemented through the HART protocol. Since then the drive for Open Systems Interconnectivity has brought about the Fieldbus Technology which is deemed to herald a new era in signal communications. This paper addresses the two applications of this new technology in the area of communications and a means of harnessing the data that can be made available from such devices.

This paper presents a temporal logic formulation of discrete event control which forms a new theoretical basis for control analysis and synthesis of a class of discrete event systems (DES). Specifically, the new basic notions of controllability, control invariance and /spl Sigma//sub u/-invariance are characterized for a safety temporal logic formula, and the necessary and sufficient condition for the existence of its supervisor is established. The existing result based on the predicate approach is shown to be generalized under our formulation. A control synthesis procedure is given for a class of DES based on a specialized safety formula, known as the forbidden state specification. Two simple examples illustrate the proposed axiomatic approach.

A unifying temporal logic framework is proposed for modeling, specifying, and analyzing mechanical assembly sequences. Propositional temporal logic of Manna and Pneuli is the assertion language used for representing and analyzing all constraints or conditions that assembly sequences must satisfy. The generalization of the existing representations through the proposed framework is demonstrated. A new concept of reverse-equivalence, relating assembly and disassembly forms of knowledge, is introduced. It is shown that existing and new assembly sequence properties can be formulated and rigorously proved via mechanical theorem proving based on two assembly process-axioms, and the language inference rules and theorems. Comparison of the proposed framework with the existing representation schemes highlights the main strengths of the proposed framework, viz., temporal expressiveness, strong mechanical manipulation capability and precise formalism. The implementation of the framework on an IPC SUN SPARC workstation using Quintus Prolog for automatic generation of assembly sequences is described. A simple example illustrates the use of the proposed framework for representation, evaluation and selection of feasible assembly sequences.>

A temporal logic framework is proposed ~OT modelling, specifying and analysing mechanical a ssembly sequences. PTO~Ositional temporal logic of Manna and Pneuli is the assertion language for representing and analysing all constraints OT conditions that assembly sequences must satisfy; and for logically integrating them t o yield all f easible sequences. The strength of this framework over existing representation schemes lilzs in its strong mechanical m anipulability, temporal expressiveness and precise formalism. The implementation of the framework on a workstation for automatic generation of assembly sequences is dedcribed. A sample example illustrates the use of the f ramework.