WinchModels

Introduction

This package shall implement different models of ground stations for airborne wind energy systems. A ground station has the following components:

• motor/generator
• brake (optional)
• gearbox (optional)
• drum

Currently implemented is a model of the 20kW ground station from Delft University of Technology. In addition, a generic, torque controlled winch without brake is implemented. The torque controlled winch can operate both with a set_torque or with a set_speed. If a set_speed is provided, then a PI controller for is used that compares the actual speed and the set speed and controls the torque. The async generator cannot be used with a set_torque, only with a set_speed which is equal to the synchronous speed of the motor/ generator.

Mathematical background

Torque controlled winch.

Installation

First, install Julia 1.12 or 1.13. Then launch Julia and install this package using the package manager.

using Pkg
pkg"add WinchModels"

Exported types

AbstractWinchModel
AsyncMachine
TorqueControlledMachine
MatlabMachine

Main functions

calc_acceleration(wm::AsyncMachine, speed, force;            set_torque=nothing, set_speed=nothing, use_brake = false)
calc_acceleration(wm::TorqueControlledMachine, speed, force; set_torque=nothing, set_speed=nothing, use_brake = false)
calc_acceleration(wm::MatlabMachine, speed, force;           set_torque=nothing, set_speed=nothing, use_brake = false)
calc_force(wm::AsyncMachine, set_speed, speed)
update_winch_state!(wm, set_speed; use_brake=false, speed=nothing, force=nothing)

Winch model in Matlab

The MatlabMachine is the model of the AsyncMachine, implemented in Matlab by the function async_machine_step.m, which must be on the Matlab path. It needs Matlab R2020b or newer and using MATLAB (package extension WinchModelsMATLABExt). Matlab is called once per time step, in update_winch_state!, which gets the reel-out speed and the tether force at the start of the step; within the time step, calc_acceleration(...; update_state=false) uses the linearization around that point. The Matlab function, examples and documentation are part of KiteControllers.jl, see Winch Model in Matlab.

Plot of function "calc_force"

Helper functions

calc_reactance
calc_inductance
calc_resistance
calc_coulomb_friction
calc_viscous_friction
smooth_sign

Plot of function "smooth_sign"

Performance

using WinchModels, BenchmarkTools, KiteUtils

set = se()
wm = AsyncMachine(set)
@benchmark calc_acceleration(wm, 7.9, 8.0, 100.0)

On i7-7700K 17ns for Julia, 1050ns with Python.

License

This project is licensed under the MIT License. Please see the below WAIVER in association with the license.

WAIVER

Technische Universiteit Delft hereby disclaims all copyright interest in the package “KiteModels.jl” (models for airborne wind energy systems) written by the Author(s).

Prof.dr. H.G.C. (Henri) Werij, Dean of Aerospace Engineering

See also

• Research Fechner for the scientific background of this code
• the package KiteUtils
• the packages KiteModels and KitePodModels and AtmosphericModels
• the package RobustKiteControllers which provides path following controllers, but no reel-in control yet.
• the packages WinchControllers, KiteControllers and KiteViewers
• the VortexStepMethod