Miscellaneous Functions (Not yet properly filed/documented)

axis2dlim (axdata)

Function File

Determine axis limits for 2-D data (column vectors); leaves a 10% margin around the plots. Inserts margins of +/- 0.1 if data is one-dimensional (or a single point). Input axdata n by 2 matrix of data [x y]. Output axvec Vector of axis limits appropriate for call to axis function.

moddemo (inputs)

Function File

Octave Control toolbox demo: Model Manipulations demo.

prompt (str)

Function File

Prompt user to continue Input str Input string. Its default value is: \n ---- Press a key to continue ---

rldemo (inputs)

Function File

Octave Control toolbox demo: Root Locus demo.

[rldata k] = rlocus (sys[, increment, min_k, max_k])

Function File

Displays root locus plot of the specified SISO system. ----- --- -------- --->| + |---|k|---->| SISO |-----------> ----- --- -------- | - ^ | |_____________________________| Inputs sys system data structure min_k Minimum value of k max_k Maximum value of k increment The increment used in computing gain values Outputs Plots the root locus to the screen. rldata Data points plotted: in column 1 real values in column 2 the imaginary values. k Gains for real axis break points.

[yy idx] = sortcom (xx[, opt])

Function File

Sort a complex vector. Inputs xx Complex vector opt sorting option: "re" Real part (default); "mag" By magnitude; "im" By imaginary part. if opt is not chosen as "im" then complex conjugate pairs are grouped together, a - jb followed by a + jb. Outputs yy Sorted values idx Permutation vector: yy = xx(idx)

[num den] = ss2tf (a, b, c, d)

Function File

Conversion from tranfer function to state-space. The state space system: . x = Ax + Bu y = Cx + Du is converted to a transfer function: num(s) G(s)=------- den(s) used internally in system data structure format manipulations.

[pol zer, k] = ss2zp (a, b, c, d)

Function File

Converts a state space representation to a set of poles and zeros; k is a gain associated with the zeros. Used internally in system data structure format manipulations.

starp (P K, ny, nu)

Function File

Redheffer star product or upper/lower LFT respectively. +-------+ --------->| |---------> | P | +--->| |---+ ny | +-------+ | +-------------------+ | | +----------------+ | | | | +-------+ | +--->| |------+ nu | K | --------->| |---------> +-------+ If ny and nu "consume" all inputs and outputs of K then the result is a lower fractional transformation. If ny and nu "consume" all inputs and outputs of P then the result is an upper fractional transformation. ny and/or nu may be negative (i.e. negative feedback).

[a b, c, d] = tf2ss (num, den)

Function File

Conversion from tranfer function to state-space. The state space system: . x = Ax + Bu y = Cx + Du is obtained from a transfer function: num(s) G(s)=------- den(s) The vector den must contain only one row whereas the vector num may contain as many rows as there are outputs y of the system. The state space system matrices obtained from this function will be in controllable canonical form as described in Modern Control Theory (Brogan, 1991).

[zer pol, k] = tf2zp (num, den)

Function File

Converts transfer functions to poles-and-zero representations. Returns the zeros and poles of the SISO system defined by num/den. k is a gain associated with the system zeros.

[a b, c, d] = zp2ss (zer, pol, k)

Function File

Conversion from zero / pole to state space. Inputs zer pol Vectors of (possibly) complex poles and zeros of a transfer function. Complex values must come in conjugate pairs (i.e. x+jy in zer means that x-jy is also in zer). The number of zeros must not exceed the number of poles. k Real scalar (leading coefficient). Outputs a b c d The state space system in the form: . x = Ax + Bu y = Cx + Du

[num den] = zp2tf (zer, pol, k)

Function File

Converts zeros / poles to a transfer function. Inputs zer pol Vectors of (possibly complex) poles and zeros of a transfer function. Complex values must appear in conjugate pairs. k Real scalar (leading coefficient).