This repository contains the code used to control by means of model-free Reinforcement Learning an airborne wind energy system used for electric energy production. The physical model is based on the "yo-yo configuration" proposed by Canale et al., 2009.

First of all, the C++ environment libkite.so has to be compiled, by executing the command:

make #to compile on standard x86 systems

make parallel #to enable parallel loading of turbulent flow data (on x86 only)

make m1 #to compile on Apple silicon macs, not recommended

Learning can be performed by running the command:

python run.py

The specifications of the learning process are enforced by using input parameters:

• alg: RL algorithm to be used, either sarsa or td3 (dql is soon to be deprecated);
• path: Path where to store learning outputs;
• wind: Kind of wind pattern to use, either const or lin or turbo;
• episodes and duration: Number of learning episodes and maximum duration of each episode (in seconds);
• lr and eps: Initial learning rate and initial exploration rate (for SARSA);
• actor_lr and critic_lr: learning rates for actor-critic (TD3);
• lrstartand epsstart: learning step when to start learning rate and exploration rate decay;
• lrrate and epsrate: exponents for the aforementioned decay, shaped as a power law.
• step: interval between two actions;

Constant and linear wind patterns are generated algorithmically on-the-go, while the turbulent flow data (~14GB) can be downloaded by typing the following command in the env folder:

wget --load-cookies /tmp/cookies.txt "https://docs.google.com/uc?export=download&confirm=$(wget --quiet --save-cookies /tmp/cookies.txt --keep-session-cookies --no-check-certificate 'https://docs.google.com/uc?export=download&id=15u4cvvwuiFLsNw6VlbYSLADoMQReszOn' -O- | sed -rn 's/.*confirm=([0-9A-Za-z_]+).*/\1\n/p')&id=15u4cvvwuiFLsNw6VlbYSLADoMQReszOn" -O flow.tgz && rm -rf /tmp/cookies.txt

Then extract the turbulent flow files by typing:

tar zxvf flow.tgz

After successfully completing a learning process, one can evaluate the learned policy by running:

python test.py

With similar parameters as the other script.

Example of a kite trajectory in the turbulent Couette flow:

python run.py --alg=sarsa --wind=turbo --episodes=50000 --eval_episodes=1000  --lr=0.1 --lrstart=1000000 --epsstart=1200000 --path=./results/turbo/

Authors:

• Lorenzo Basile
• Maria Grazia Berni
• Claudio Leone

Project developed in the group of prof. Antonio Celani (QLS@ICTP, Trieste)