Tuning gain for autopilot - tunablesurface problem

Hello, I've been recently trying to scheduls gains in 3-loop autopilot provided with MATLab in design a guidance system due my simulations when changing mass and other parameters of rokcet. I've been trying to use Tuning of Gain-Scheduled Three-Loop Autopilot, but when trying to use 'tunablesurface' in Tunable gain surface I'm getting error like this:

     Undefined function or variable 'tunableSurface'.
    Error in tune_gain_surf (line 4)
    Kp = tunableSurface('Kp', 0.1, TuningGrid, ShapeFcn);

How to deal with it?

[Geoff Hayes]

Tom - according to tunableSurface, this object was introduced in R2015b as part of the Robust Control Toolbox. Do you have this toolbox and this version of MATLAB? What happens when you type (in the Command Window)

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