Retrieves the state-space model from the transfer function expressed in terms of polynomials ratio

bnsn + … b1s + b0 / amsm + … a1s + a0

Syntax

A,B,C,D = SSFromTF(num,den)

Argument

Name

Description

num

A vector of the numerator coefficients in descending power of .  Its length is equal to n+1.

den

A vector of the denominator coefficients in descending power of s.  Its length is equal to m+1.  See Comments below for restrictions.

Outputs

Name

Description

A

The (m-1) x (m-1) state transition matrix.

B

The (m-1) x 1 control vector mapping inputs to state variables.

C

The 1 x (m-1) output vector relating the states to outputs.

D

The feed-forward 1 x 1 matrix mapping the input directly to the output.

Example

Find the state space system for the transfer function expressed as

2s + 1 / 3s2 + 4

Syntax

Num = [2, 1]

Den = [3, 0, 4]

A,B,C,D = SSFromTF(Num, Den)

Result

A =  0 -1.3333

    1  0

B =  1

    0

C = 0.66667 0.33333

D = 0

Comments

The order of the numerator must be less than or equal to that of the denominator, for example, n ≤ m.  The order of the denominator must be at least one, for example, m ≥ 1 and a1 must be non-zero if m = 1.

See Also

LSim