Microprocessors in process control

Automatic control techniques are now economically available through microprocessors to a wide range of manufacturing industry. The stress on replacing analog process controllers by microprocessor based systems is becoming increasingly pervasive. This paper is aimed at creating a greater awareness about the capabilities of microprocessors for process control. The hardware and software requirements for implementing certain digital algorithms are considered. Algorithms for realizing adaptive control are introduced and the recent trend towards distributed control is highlighted.     

Designing genetic regulatory networks using fuzzy Petri nets approach

In this paper, we have successfully presented a fuzzy Petri net (FPN) model to design the genetic regulatory network. Based on the FPN model, an efficient algorithm is proposed to automatically reason about imprecise and fuzzy information. By using the reasoning algorithm for the FPN, we present an alternative approach that is more promising than the fuzzy logic. The proposed FPN approach offers more flexible reasoning capability because it is able to obtain results with fuzzy intervals rather than point values. In this paper, a novel model with a new concept of hidden fuzzy transition (HFT) to design the genetic regulatory network is developed. We have built the FPN model and classified the input data in terms of time point and obtained the output data, so the system can be viewed as the two-input and one output system. This method eliminates possible false predictions from the classical fuzzy model thereby allowing a wider search space for inferring regulatory relationship. The experimental results show the proposed approach is feasible and acceptable to design the genetic regulatory network and investigate the dynamical behaviors of gene network.     

A Microprocessor-Based Multiloop Process Controller

This paper describes a microprocessor-based multiloop process controller which can be readily utilized in a broad range of industrial applications. The controller, developed around Intel's 8085 microprocessor, provides the user with, in one unit, a software package combining feedback, feed-forward, ratio, and cascade control functions.     

Microprocessor-based sliding mode controller for a micromachine

The design and microprocessor-based implementation of a power system stabilizer using variable-structure systems theory is presented. The design is based on a geometric approach for finding the switching hyperplanes for discontinuous control. The stabilizer is implemented on a laboratory micromachine using an INTEL 8085A microprocessor. The experimental results show the effectiveness of the stabilizer in improving system damping. The parameter insensitivity in the sliding mode is demonstrated     

The use of FORTH language in process control

A tutorial discussion is given on the high-level programming language FORTH with particular reference to process control application. The advantages of FORTH are illustrated through a practical example.

FORTH, originally developed for telescope control, contains many features designed to facilitate the construction of software for process control systems. In this paper, we describe some of these features and provide a design of a software package for a multiloop control system to illustrate its use. The software package, developed for Rockwell's AIM 65 microcomputer, contains programs written in FORTH for implementing feedback, feed-forward, ratio and cascade control functions. Experimental results pertaining to a furnace simulated on an EAL-580 hybrid computer are presented. A brief discussion is given on experience gained in the use of FORTH language for process control.     

Microprocessor implementation of fast Walsh-Hadamard transform forcalculation of symmetrical components

A microprocessor-based algorithm for the calculation of symmetrical components of a three-phase system is presented. The symmetrical component transformation is applied to the input waveform, and the harmonic content in the sequence components thus obtained is filtered out by using the fast Walsh-Hadamard transform. The algorithm is fast and accurate and the three sequence components can be calculated in 3/4th of a cycle after fault occurrence     

A Microprocessor-Based Scheme for Torque-Angle and Speed Measurement

This paper describes a new scheme for continuous monitoring of torque angle and speed of a 3-kVA laboratory synchronous machine. The proposed scheme does not require mounting of an optical disc or a magnetic pickup on the shaft of the machine. Use is made of a 400-Hz 32-pole tacho generator mounted on the machine shaft. Intel's 8085A microprocessor is employed for the measurement and calculations of torque angle and percentage slip. The testing and evaluation of the scheme, for various operating conditions, have been carried out in the laboratory.     

Design of digital controllers for multivariable stochastic systems

A new approach for designing controllers for randomly disturbed interactive multivariable systems is proposed. This is based on an extension of the inverse-Nyquist-array method and the minimum variance control strategy for single-input/single-output systems.     

Microprocessor-based negative-sequence relay

A three-phase power system can be subjected to various types of faults. Symmetrical components furnish a tool which is well suited for analysing such faults. This paper describes a microprocessor-based system which calculates the symmetrical components from the sampled data of the three phase quantities in real time. The computed symmetrical components can be used conveniently in a variety of protection schemes. A negative-sequence relay for the protection of three-phase generators is described. The relay protects a generator against negative-sequence current using a constant-current extension of the characteristic of an inverse-time induction relay responsive to negative-sequence current. The performance of the relay has been evaluated in the laboratory under various fault conditions. Some test results are included in this paper.     

Comments on: ‘Diagonal dominance for multivariable Nyquist array methods using function minimization’

The above paper (Leininger, 1979) claims to give a ‘new’ method for achieving diagonal dominance in multivariable systems. This is, however, not the first time that a function minimization approach has been used to obtain dominance. An optimisation oriented method was first proposed in 1975 (Ahson, 1975). This method is based on a new formulation of diagonal dominance criterion which takes into account model parameter uncertainties.