AquaGym environment

The goal of this AI project is to build a gym environment that simulates the motion of a water drone with differential drive moving in a cluttered environment and subject to a superimposed non-deterministic water flow. The idea is that a DQN policy can learn its way to reach the goal state providing thrust to the motors at each step. On top of that, the water flow changes the drone's trajectory and so a correction is needed in order to avoid the collisions. Two types of environment are offered, differing in the domain of the action space (either continuous or discrete).

Design choices

• the world dimensions are 100x100, so the position is in [0,100] x [0,100];
• the angle in [-pi,+pi], from right (-pi) to left (+pi), where 0 is the north direction;
• the motors' thrust is in [0.2,0.5];
• for the continuous action space case any combination in [0.2,0.5] x [0.2,0.5] is allowed;
• for the discrete action space case we provide 3 actions, with indexes from 0 to 2, [rotate left, rotate right, full throttle], which are mapped onto the thrusts (0.2, 0.5), (0.5, 0.2) and (0.5, 0.5);
• the wave speed is in [-0.05,+0.05] with a variance of 0.001;
• obstacles are rectangles or circles and can be customized in position and size;
• for the reward function we choose:
  • +10 when the goal is reached;
  • -10 when hitting either an obstacle or the border;
  • (prev_dist_from_goal - dist_from_goal) * 0.7 for each non-ending move; both collisions and reaching the goal are ending events;

DQN implementation

We also provide a Deep-Q-Network implementation to obtain the policy, edit file dqn_train_policy.py in order to train the network and dqn_train_plotter.py to see the overall rewards/success during the process. After the training, use test_dqn.py to see the resulting policy (we also provide files test_optimal.py and test_random.py for comparison) and dqn_test_plotter.py to see the overall success rate and reward distribution. A quasi-intuitive plot of the q-value in the various states is available with dqn_qvalue_plotter.py.

With the provided setup, we can obtain results similar to those shown in the plots below.