Take all initial values into account

[ufechner7]

For the KPS4 model, all initial values should be taken into account:

initial:
    elevations: [70.8]               # initial elevation angle   [deg]
    elevation_rates: [0.0]           # initial elevation rate  [deg/s]
    azimuths: [0.0]                  # initial azimuth angle     [deg]
    azimuth_rates: [0.0]             # initial azimuth rate    [deg/s]
    headings: [0.0]                  # initial heading angle     [deg]
    heading_rates: [0.0]             # initial heading rate    [deg/s]
    # three values are only needed for RamAirKite, for KPS3 and KPS4 use only the first value
    l_tethers: [150.0]               # initial tether lengths      [m]
    kite_distances: [51.0]           # initial kite distances     [m]
    v_reel_outs: [0.0]               # initial reel out speeds   [m/s]
    depowers: [25.0]                 # initial depower settings    [%]
    steerings: [0.0]                 # initial steering settings   [%]

It might be useful to make this work for KPS3 first. To determine the initial tether shape, https://github.com/AndreaBertozzi/TetherModels.jl could be used. Probably it would be a good idea to use https://github.com/SciML/NonlinearSolve.jl to determine the initial equilibrium.

[1-Bart-1]

NonlinearSolve can find the initial tether shape when you start with a straight tether as well (you might have to add some relaxation to the solver for this to work).