Some aspects of algorithms for digital control with a microcomputer

Abstract

We study the principles of constructing algorithrr:s for direct digital control for an automatic control system of complicated (step-by-step or multiple-input multiple-output} structure, based on modular software in the controlling microcomputer and taking account of the controller saturation mode. initialization conditions of the elements of the system, reliability of the input information, and the principles of automatic blocking of the system elements when the normal operating mode breaks down.The appearance and rapid improvement of microprocessor technology has led to its widespread use in digital automatic control systems (ACS). The design of digital automatic control systems with controlling microcomputers has made it possible to apply more complicated functional elements of systems, new architectural principles for constructing automatic control systems in which hardware implementation is replaced with solution by software methods, which in turn have made it possible to implement more complicated control functions with a higher degree of system reliability.In the present paper we consider a method for algorithmically equipping systems of direct digital control in the implementation of step-by-step automatic control systems with feedback for deviation and forwakd connections for perturbations, as well as multiple-input multiple-output automatic control systems with external intersecting connections.Algorithms for direct digital control can be divided according to to their operational designation into two parts: a computational algorithm by means of which all computational procedures are carried out, and a logical algorithm that characterizes the state of the direct digital control system and moves the system from one state to another.To characterize the state of the system the logical algorithm forms a controller status word (CSW) of the system on each pass of the microcomputer. The length of this word equals the length of a microcomputer command and consists of t6 bits. The CSW characterizes the state of the system (active/inactive), the control mode (automatic/manual), the initialization of the controller (initializing or operating mode), the input data quality (normal, or with anomalous rejection due to transmitter failure), controller saturation mode (unrestricted controller output (resp. output with restrictions from above/below), output not connected with the next element of the ACS), control policy being used (P/I/PI/PD/PID), and characteristics of the controller output connection with the next element of the system (output connected via a discrete signal output module with an executive mechanism (EM) of constant rate (output used in the structure of the digital ACS or transformed into an analog signal). The table below gives a detailed picture of the CSW.The basis of the computational part of a digital direct control algorithm is the discrete PID-policy for controlwhere/zn is the control action, n is a discrete time at which the controller functions, K is the transmittivity factor, g,~ is the discre...