12

Concept of State Variable Modelling

12.1 INTRODUCTION

The concept of modelling, analysis and design of control systems discussed, so far was based on their transfer functions which suffer from some drawbacks as stated below.

  1. The transfer function is defined only under zero initial conditions.
  2. It is only applicable to linear time-invariant systems and generally restricted to single-input singleoutput (SISO) systems.
  3. It gives output for a certain input and provides no information about the internal state of the system.

To overcome these drawbacks in the transfer function, a more generalised and powerful technique of state variable approach in the time domain was developed. The state variable method of modelling, analysis and design is applicable ...

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