Why do I receive an "undefined command/function hinfpar" error when using the HINFGS function in the Robust Control Toolbox 3.0.1(R14SP2)?

When I execute the following commands:

load G_pol;

[Gopt,K] = hinfgs(G_pol,[1 1],2);

I receive the following error:

 ??? Undefined command/function 'hinfpar'.

 Error in ==> hinfgs at 78

 [A,B1,b2,C1,c2,D11,d12,d21,d22]=hinfpar(psinfo(pds,'sys',1),r);

Answer 1

[MathWorks Support Team]

There is a bug in the Robust Control Toolbox 3.0.1 (R14SP2) that causes the error when using the HINFGS function. This behavior occurs because:

1. The HINFPAR, KLMI, MACH_EPS, XDIAG, GETPHI functions are only available in the "private" directory at the path: '$MATLABROOT/toolbox/robust/rctobsolete/lmi/private/'.

2. The HINFGS function exists at two places. The default version of the function is at the path: '$MATLABROOT/toolbox/robust/rctlmi/'. Since the '$MATLABROOT/toolbox/robust/rctlmi/private/' directory does not contain the HINFPAR and the other functions, MATLAB does not find these files.

To work around this issue, execute the following code in MATLAB:

path([matlabroot, '\toolbox\robust\rctobsolete\lmi'],path);

This will add the required path at the top of the current search path and thus the HINFGS function in the '\toolbox\robust\rctobsolete\lmi' directory will be invoked. The '\toolbox\robust\rctobsolete\lmi\private' directory has the HINFPAR and other functions that are necessary for the successful execution of the HINFGS function.

In all the above cases, "$MATLABROOT" is the output of executing the MATLABROOT command on the MATLAB command prompt.