Interactive Continuous And Discrete Step Response Using Matlab Gui

Abstract

It is important in the study of classical feedback control to understand the correspondence between pole locations and time response. Quadratic poles are particularly important because many systems can be approximately characterized by a quadratic. This paper describes a program, written in MATLAB and using the Graphical User Interface (GUI), which permits the user to drag a quadratic pole in the s-plane and observe, in real time, the changing continuous step response. The program provides the student with the means to actually observe concepts presented in class, including s-plane lines of constant overshoot, time to peak, and settling time.

A second program is described which allows the student to drag a quadratic pole in the z-plane and to observe the corresponding discrete step response. In addition to overshoot, time to peak, and settling time, the number of samples per cycle are easily seen as the z-pole is moved. The sample time can be changed while the program is in execution. Before describing these programs, the paper discusses aspects of GUI program development.

I. Introduction

Many engineering faculty members have taught long enough to see computer programming evolve from batch processing, to timesharing, to PCs with character based operating systems, to PCs with windows based operating systems. In the earlier evolutions it was easy to write code, frequently in FORTRAN or Basic, to serve as an aid to engineering education. In the latest evolution there are many useful commercial programs written for engineering education, but most engineering faculty still would like to write programs of their own.

Programs written for window based operating systems usually contain Graphical User Interfaces, or GUIs. Someone contemplating writing code to produce GUIs might suspect that it is a complicated process, and it is. There are some languages which help to reduce the complication, such as Visual Basic and Visual C. However, these languages require programming at a rather low level. Frequently specialized libraries must be acquired as well. The capability of a high level language, such as MATLAB along with its toolboxes, is hard to ignore.

Along with MATLAB 4 came a number of demonstration programs with GUIs. The potential of combining GUIs with the enormous capability of MATLAB is enticing. However, an examination of the code for these programs is daunting. The code is largely devoted to the