RamAirKite.jl

A Julia package for simulation of generic ram-air kites built on SymbolicAWEModels.jl.

Overview

RamAirKite.jl provides model setup utilities, simulation functions, and configuration structs for simulating ram-air kites. Unlike V3Kite.jl which is tailored for the TU Delft V3 kite with KCU-specific steering/depower percentages, RamAirKite is designed for generic ram-air kite simulations with direct torque control.

Installation

It is suggested to install this package from git:

git clone https://github.com/OpenSourceAWE/RamAirKite.jl.git
cd RamAirKite.jl/bin
./install

After the installation, launch Julia with

cd ..
./bin/run_julia

and then, in the Julia REPL run the example with

include("examples/ram_air_kite.jl")

Quick Start

using RamAirKite
using SymbolicAWEModels
using GLMakie  # For visualization

# Configure settings
set_data_path(ram_air_data_path())
set = Settings("system.yaml")
set.physical_model = "ram"   # "ram", "simple_ram", or "4_attach_ram"
set.v_wind = 15.51           # m/s
set.l_tether = 50.0          # meters

# 1. system structure  2. model  3. init
sys_struct = create_sys_struct(set)
sam = SymbolicAWEModel(set, sys_struct)
# edit sys_struct here (transforms, tethers, group damping, ...) before init!
init!(sam)

See examples/ram_air_kite.jl for a full stepping loop with logging, steering, and replay.

Physical Model Variants

The package supports three physical model variants, each with different levels of complexity:

"ram" (default)

Standard 4-group ram-air kite with bridle system:

• Full bridle geometry
• 4 deformable wing groups along span
• Suitable for most simulations

"simple_ram"

Simplified model without bridle:

• Direct tether connection to wing
• Single-segment tethers
• Faster simulation, reduced fidelity

"4_attach_ram"

Detailed 4-point bridle attachment:

• 4 deformable wing groups
• Full pulley constraints
• Highest fidelity, slower simulation

3-Winch Control System

The ram-air kite uses a 3-winch torque control system:

1. Power Left Winch: Controls left side of power line
2. Power Right Winch: Controls right side of power line
3. Steering Winch: Differential steering control

For simulation, the package provides sinusoidal steering oscillation via sim_oscillate!(), which applies torque inputs to create periodic left-right steering motions.

Configuration Options

RamAirSimConfig(
    # Model selection
    physical_model = "ram",              # Model variant
    wing_type = QUATERNION,              # QUATERNION or REFINE

    # Simulation parameters
    sim_time = 10.0,                     # Total time [s]
    dt = 0.05,                           # Time step [s]
    vsm_interval = 3,                    # VSM update frequency

    # Environment
    v_wind = 15.51,                      # Wind speed [m/s]
    upwind_dir = -90.0,                  # Upwind direction [deg]

    # Initial conditions
    tether_length = 50.0,                # Tether length [m]
    elevation = nothing,                  # Elevation [deg] or nothing

    # Steering control
    steering_freq = 0.5,                 # Oscillation frequency [Hz]
    steering_magnitude = 1.0,            # Torque magnitude [Nm]
    steering_bias = 0.2,                 # Torque bias [Nm]

    # Model options
    remake_cache = false,                # Force rebuild cache
    brake = true,                        # Winch brake engaged
)

Running Examples

julia --project=examples examples/ram_air_kite.jl

Dependencies

• SymbolicAWEModels.jl: Core symbolic modeling
• VortexStepMethod.jl: Aerodynamic calculations
• KiteUtils.jl: Common types and utilities
• GLMakie.jl (optional): Visualization

Data Files

The package includes bundled data files in data/ram_air_kite/:

• system.yaml - System configuration
• settings.yaml - Simulation settings
• vsm_settings.yaml - Aerodynamic settings
• ram_air_kite_body.obj - 3D CAD model
• ram_air_kite_foil.dat - Airfoil shape
• *_polar.csv - Cl/Cd/Cm polars with deflection angles

License

MPL-2.0