The class ultv is defined by LTV parametric uncertainties of the form:
Here
 , are fixed matrices (having the same size as ).
 is a piecewise continuous timevarying parameter vector that takes its values form the (compact) polytope
 is assumed to be star convex:
The ultis class can be defined by
Just specifying defines an LTV parametric uncertainty on the interval , which is repeated once (i.e., and ).
Specifying and/or changing properties proceeds as summarized in the following two tables for properties related to the uncertainty and to IQCmultiplier respectively.
Property  Description 
Polytope  With the option Polytope on can specify the generator points of as
Note: It is always assumed that the 0 is contained in the set. 
UncertaintyMap  Specify the matrices as a cell array . This defines the uncertainty map . Note: In case you wish to apply the DGrelaxation scheme, must be defined such that with , begin normalized. 
InputChannel/ OutputChannel  Specify which input and output channels of the uncertain plant are affected by . For each , the channels should be specified as:
Here the order of the channels is not relevant, while , respectively denote the and in and output channel of the uncertain plant . Note here thatthe row length of and equals the number of repetitions of . The option InputChannel/ OutputChannel should then be specified as a cell:

Property  Description 
RelaxationType  Specify the relaxation type. Options are (default = ‘DG’): – DGscalings: ‘DG’ – Convex hull relaxation: ‘CH’ – Partial convexity: ‘PC’ – Zeroth order Polya relaxation: ‘ZP’ 
PrimalDual  Specify whether the multiplier should be a primal/dual parametrization (default = ‘Primal’). – Primal multipliers: ‘Primal’ – Dual multipliers: ‘Dual’ Note: For a standard IQCanalysis, all multipliers must be primal ones. 
Note: See Section 5.2 of [1] for the details on the mathematical derivation of the IQCmultiplier.