Machine Learning Engineer Nanodegree
Reinforcement Learning
Project: Train a Smartcab How to Drive
Project Overview
In this project reinforcement learning techniques is applied for a self-driving agent in a simplified world to aid it in effectively reaching its destinations in the allotted time. First the environment is investigated and the agent operates in by constructing a very basic driving implementation. Once agent is successful at operating within the environment, then each possible state is identified where the agent can be in when considering such things as traffic lights and oncoming traffic at each intersection. With states identified, a Q-Learning algorithm is implemented for the self-driving agent to guide the agent towards its destination within the allotted time. Finally, the Q-Learning algorithm is improved upon to find the best configuration of learning and exploration factors to ensure the self-driving agent is reaching its destinations with consistently positive results.
Description
In the not-so-distant future, taxicab companies across the United States no longer employ human drivers to operate their fleet of vehicles. Instead, the taxicabs are operated by self-driving agents, known as smartcabs, to transport people from one location to another within the cities those companies operate. In major metropolitan areas, such as Chicago, New York City, and San Francisco, an increasing number of people have come to depend on smartcabs to get to where they need to go as safely and reliably as possible. Although smartcabs have become the transport of choice, concerns have arose that a self-driving agent might not be as safe or reliable as human drivers, particularly when considering city traffic lights and other vehicles. To alleviate these concerns, as an employee for a national taxicab company is to use reinforcement learning techniques to construct a demonstration of a smartcab operating in real-time to prove that both safety and reliability can be achieved.
Software Requirements
This project uses the following software and Python libraries:
Starting the Project
This project contains three directories:
/logs/: This folder will contain all log files that are given from the simulation when specific prerequisites are met./images/: This folder contains various images of cars to be used in the graphical user interface./smartcab/: This folder contains the Python scripts that create the environment, graphical user interface, the simulation, and the agents.
Finally, in /smartcab/ are the following four files:
- Modify:
agent.py: This is the main Python file where work on the project is performed.
- Do not modify:
environment.py: This Python file will create the smartcab environment.planner.py: This Python file creates a high-level planner for the agent to follow towards a set goal.simulation.py: This Python file creates the simulation and graphical user interface.
Definitions
Environment
The smartcab operates in an ideal, grid-like city (similar to New York City), with roads going in the North-South and East-West directions. Other vehicles will certainly be present on the road, but there will be no pedestrians to be concerned with. At each intersection there is a traffic light that either allows traffic in the North-South direction or the East-West direction. U.S. Right-of-Way rules apply:
- On a green light, a left turn is permitted if there is no oncoming traffic making a right turn or coming straight through the intersection.
- On a red light, a right turn is permitted if no oncoming traffic is approaching from your left through the intersection. To understand how to correctly yield to oncoming traffic when turning left, you may refer to this official drivers? education video, or this passionate exposition.
Inputs and Outputs
Assume that the smartcab is assigned a route plan based on the passengers? starting location and destination. The route is split at each intersection into waypoints, and you may assume that the smartcab, at any instant, is at some intersection in the world. Therefore, the next waypoint to the destination, assuming the destination has not already been reached, is one intersection away in one direction (North, South, East, or West). The smartcab has only an egocentric view of the intersection it is at: It can determine the state of the traffic light for its direction of movement, and whether there is a vehicle at the intersection for each of the oncoming directions. For each action, the smartcab may either idle at the intersection, or drive to the next intersection to the left, right, or ahead of it. Finally, each trip has a time to reach the destination which decreases for each action taken (the passengers want to get there quickly). If the allotted time becomes zero before reaching the destination, the trip has failed.
Rewards and Goal
The smartcab will receive positive or negative rewards based on the action it as taken. Expectedly, the smartcab will receive a small positive reward when making a good action, and a varying amount of negative reward dependent on the severity of the traffic violation it would have committed. Based on the rewards and penalties the smartcab receives, the self-driving agent implementation should learn an optimal policy for driving on the city roads while obeying traffic rules, avoiding accidents, and reaching passengers? destinations in the allotted time.
Run
In a terminal or command window, navigate to the top-level project directory smartcab/ (that contains this README) and run one of the following commands:
python smartcab/agent.py
python -m smartcab.agent
This will run the agent.py file and execute your agent code.