CLASSICAL CONTROL - TRANSFER FUNCTION MODEL
CLASSICAL CONTROL - TRANSFER FUNCTION MODEL
Classical Control - Transfer FUNCTION MODEL
1. Classical control is a branch of control engineering
that deals with the behavior of dynamical systems with inputs, and
how their behavior is modified by feedback, using the Laplace transform as a basic tool to model such systems.
2. In classical control systems, knowledge of the plant is in the
form of a set of algebraic and differential equations, which analytically
relate inputs and outputs.
3. The system analysis is carried out in the time domain using differential
equations in the complex-s domain with Laplace transform or in the frequency domain by
transforming from the complex-s domain.
4. All systems are assumed to be second-order and single variable, and
higher-order system responses and multivariable effects are ignored
5. The classical control theory and methods (such AS ROOT locus) are based
on a simple input-OUTPUT DESCRIPTION of the plant, usually expressed as A
TRANSFER function.
6. These methods do not HAVE ANY knowledge of the interior structure of THE
PLANT, and limit us to single-input single-OUTPUT (SISO) systems, and allows only
limited control of the closed-loop behavior when feedback control is used
7. Transfer function models describe the relationship between the inputs
and outputs of a system using a ratio of polynomials. The order of the Transfer
Function model is equal to the order of the denominator polynomial.
8. The roots of the denominator polynomial are referred to as the poles
of the Transfer Function model. The roots of the numerator polynomial are referred
to as the zeros of the model. The parameters of a transfer function model are its
poles, zeros, and transport delays.
LIMITATIONS/DRAWBACKS
1. Transfer function defined only under zero initial condition
2. Applicable only to the linear time-invariant system. (Due to the
assumptions such as linearity, time-invariance, etc.)
3. It Is restricted to single input single output as this becomes highly
cumbersome for use in the multi-input multi-output system.
4. It reveals only the system output for a given input and provides no information
regarding the internal states of the system
5. It does not provide an optimal design
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