It is possible to connect systems using the YopConnection command. The purpose of this is to simplify creating an initial guess for non-convex optimal control problems. By connecting your system to a controller, it is possible to create an initial guess by simulation, even for an unstable system. Despite being the main purpose, connecting the system to a controller is not the only use for connections.

## Declaration

Connections are declared using the following syntax:

c = YopConnection(arg1, arg2);


The input arguments arg1, and arg2 can be any symbolic expression that can be formulated using the system variables t, x, z, u, w, p, ode, ae, and y (see YopSystem for a description of them). arg1 and arg2 can be vector valued as long as they have the same dimension. The output argument c is a handle to the connection.

## What a YopConnection is

A YopConnection is an algebraic constraint stating

This means that the following declarations are equivalent:

c1 = YopConnection(arg1, arg2);
c2 = YopConnection(arg1-arg2, zeros(size(arg1-arg2)));
c3 = YopConnection(zeros(size(arg1-arg2)), arg1-arg2);