Other MathWorks Products (Known Software and Documentation Problems)

Known Software and Documentation Problems

Control System Toolbox 4.2: Documentation Updates

Nx Property Has Been Removed

In the lists of state-space (SS) model properties on pages 2-29 and 11-196 of the Release 11 version of the Control System Toolbox User's Guide, a property called Nx is listed. This property is not shipping with the Control System Toolbox 4.2 software.

To access the number(s) of states in an SS model or an LTI array of SS models, use

size(sys,'order')

In the case that sys is an LTI array of SS models with a different number of states in each model,

size(sys,'order')

returns an array whose entries correspond to the number of states in each model in the LTI array.

Initializing an Array of SS Models with Zero Entries

To initialize an array of SS models with zero entries, such that:

Each model in the array has Ny outputs and Nu inputs.
The array has size [S1 S2...Sn].

use

sys = ss(zeros([Ny Nu S1 S2 ... Sn]))

Note that the syntax

sys = ss(zeros([Ny Nu S1 S2 ... Sn]),Nx)

reported on page 4-15 of the Release 11 version of the Control System Toolbox User's Guide is not correct.

Corrections to the 747 Jet Transport Example

There are two small changes to the 747 jet transport example described on page 9-3 of the "Design Case Studies" chapter of the Control System Toolbox User's Guide. You can also make these changes to the M-file jetdemo if you want to use the demo to follow along with the text.

The first change is in the values of the B matrix. The result is that the state-space matrices for the 747 jet model during cruise flight at MACH = 0.8 and H = 40,000 feet are

A = [-0.0558   -0.9968    0.0802    0.0415
      0.5980   -0.1150   -0.0318         0
     -3.0500    0.3880   -0.4650         0
           0    0.0805    1.0000         0];

B = [ 0.0729     0.0000
     -4.7500     0.00775
      1.5300     0.1430
           0         0];

C = [0     1     0     0
     0     0     0     1];

D = [0     0
     0     0];

This change modifies the command-line outputs for the remainder of the demonstration, but does not otherwise change the results of the example qualitatively.

The other modification to this model is that the units of the control inputs (rudder and aileron deflections) are measured in radians, not in degrees.

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