Syntax

H = energyfunction(x, v, F, E);

Description

Returns the partial derivative of an energy function and the derivative of the energy variable. Used for port hamiltonian functions.

F = d(E)/dx

v = ddt(x) or x = int(v);

x and v have a causal relation: one of them should be an input and one of them should be an output.

Example

In this example the potential energy of a spring is given by the variable E. E is defined as a function of the variable x.

parameters

 real k = 1000 {N/m};

variables

 real H {J};                // spring energy (potential)

 real x {m};

 real v {m/s};

 real F {N};

 real E {J};

equations

 v = sin (time);

 E = 0.5*k*x^2;

 H = energyfunction ( x , v, F , E );

20-sim will (symbolically) solve this to:

F = d(E)/dx = 0.5 * k * 2 * x

and

x = int(v)

Limitations