A new method for discretizing continuous-time controllers is derived, using principles of controller approximation. It focuses on the closed-loop use of the discrete-time controller. The resulting approximation criterion is a measure for stability of the control system, provides an upper bound on the sampling time for which stability can be guaranteed, and because it is based on continuous-time controller approximation it indicates the cost of discretization in terms of performance degradation. The discrete-time controller is obtained through minimization of this criterion, which can be performed with standard software used in H/sub infinity / controller design. >

A new approach to the discretization of continuous-time controllers

Implementation of digital controllers—a survey

Optimal regulation of systems described by a countably infinite number of objects

A new method for discretising continuous-time controllers is derived, using principles of controller approximation (Anderson & Yi [1]). It focuses on the closed-loop use of the discrete-time controller. The resulting approximation criterion is a measure for stability of the control system, provides an upper bound on the sampling time for which stability can be guaranteed and because it is based on continuous-time controller approximation it indicates the cost of discretization in terms of performance degradation. The discrete-time controller is obtained through minimization of this criterion, which can be performed with standard software used in H ? controller design.

This paper discusses the relationship among various recently developed constant state-feedback digital redesign methods Then, for a unity-output feedback system with an analog plant in cascade with an analog controller, the best and simple Chebyshev quadrature digital redesign method is utilized to find new pulse-amplitude-modulated (PAM) and pulse-width-modulated (PWM) digital controllers for effective digital control of the analog plant The digital controllers are determined from existing or pre-designed analog controllers as in the case of PID controllers for industrial control processes and robotics, phase lead-lag compensators for servo-mechanisms and regulator systems and guidance-autopilots for aircraft and missiles etc The proposed method provides an alternative methodology for indirect digital design of a continuous-time unity-output feedback system and enables us to accurately and effectively implement an existing or pre-designed cascaded analog controller via a digital controller

Design of PAM and PWM digital controllers for cascaded analog systems

Brief paper: Digital redesign of continuous systems by matching of states at multiple sampling periods

Digital approximation of continuous-data control systems by point-by-point state comparison

Modeling and dynamic simulation of multiple-stack variable-reluctance step motors

Time-optimal control for multiple stepping of a variable-reluctance type stepping motor is discussed. A controller with phase-position feedback is designed and built for the minimum-time control of the motor. Experimental results showed that the controlled motor is capable of traveling a prescribed number of steps in near minimum time by the injection of one or two single pulses and the proper adjustment of the lead angle of the feedback sensors. High-speed responses such as 300 steps in 100 ms from start to stop have been achieved experimentally.

http://ieeexplore.ieee.org/iel5/9/24110/01099314.pdf

Time-optimal control of a stepping motor

In this paper, a procedure is developed to investigate and predict the properties of certain types of forced oscillations in a class of nonlinear sampled-data control systems. Use is made of the discrete describing function, and the results are checked on the IBM 7094 digital computer. A sinusoidal input signal with variable amplitude and phase is applied to a relay-type sampled-data control system. It is shown that the input signal has the effect of changing the shape of the critical regions of the negative-inverse of the discrete describing function. The amplitude, phase, and frequency of the forced oscillation can be computed from the intersection between the critical region and frequency loci of the linear portion of the system. Proper selections of amplitude, phases and frequency of the forcing sinusoidal signal permit the elimination and suppression of certain types of sustained oscillations in the system.

http://ieeexplore.ieee.org/iel5/9/24090/01098305.pdf

B. C. Kuo

Papers

Brief paper: Digital redesign of continuous systems by matching of states at multiple sampling periods

Digital approximation of continuous-data control systems by point-by-point state comparison

Modeling and dynamic simulation of multiple-stack variable-reluctance step motors

Time-optimal control of a stepping motor

Forced oscillations and suppression of oscillations in nonlinear sampled-data systems