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# uss

Specify uncertain state-space models or convert LTI model to uncertain state-space model

## Syntax

```usys = uss(a,b,c,d)
usys = uss(a,b,c,d,Ts)
usys = uss(d)
usys = uss(a,b,c,d,Property,Value,...)
usys = uss(a,b,c,d,Ts,Property,Value,...)
usys = uss(sys)
```

## Description

uss creates uncertain state-space models (uss objects) or to convert LTI models to the uss class.

usys = uss(a,b,c,d) creates a continuous-time uncertain state-space object. The matrices a, b, c and d can be umat and/or double and/or uncertain atoms. These are the 4 matrices associated with the linear differential equation model to describe the system.

usys = uss(a,b,c,d,Ts) creates a discrete-time uncertain state-space object with sampling time Ts.

usys = uss(d) specifies a static gain matrix and is equivalent to usys = uss([],[],[],d).

Any of these syntaxes can be followed by property name/property value pairs.

usys = uss(a,b,c,d,'P1',V1,'P2',V2,...) set the properties P1, P2, ... to the values V1, V2, ...

usys = uss(sys) converts an arbitrary ss, tf or zpk model sys to an uncertain state-space object without uncertainties. Both usys.NominalValue and simplify(usys,'class') are the same as ss(sys).

## Examples

You can first create two uncertain atoms and use them to create two uncertain matrices. These four matrices can be packed together to form a 1-output, 1-input, 2-state continuous-time uncertain state-space system.

```p1 = ureal('p1',5,'Range',[2 6]);
p2 = ureal('p2',3,'Plusminus',0.4);
A = [-p1 0;p2 -p1];
B = [0;p2];
C = [1 1];
usys = uss(A,B,C,0);
```

In the second example, you can convert a not-uncertain tf model to an uncertain state-space model without uncertainties. You can verify the equality of the nominal value of the usys object and simplified representation to the original system.

```G = tf([1 2 3],[1 2 3 4]);
usys = uss(G)
USS: 3 States, 1 Output, 1 Input, Continuous System
isequal(usys.NominalValue,ss(G))
ans =
1
isequal(simplify(usys,'class'),ss(G))
ans =
1
```

## See Also

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