The path planning project is by far the most interesting project after Behavioral Clonning Project. This project is for Term3 (Last Term) and it is the first project for this term.

The main objective is to create a path planner that will be able to safely and smoothly create a path for a vehicle to follow along on a 3 lane highway traffic.It should be able to keep inside its lane, avoid hitting other cars and pass slow moving traffic all by using localisation, sensor fusion and map data. When passing other cars it should not hit them.

Technical Stats (Vehicle & Track)

  • Vehicle Weight: Unknown
  • Track Distance: 6,945.554m ~7km
  • Legal Speed: 50mph ~ 80kph
  • Acceleration: <10m/s
  • Legal Jerk:

Getting Started

The first thing I need to do is to move the car in our simulator and see the response. I will move it in a straight line at the max legal speed of 50mph (80kph). So in main.cpp instead of setting the speed directly, we pass next_x_vals and next_y_vals to the simulator. I then set the waypoints to be 0.5m apart (50cm). Since the car moves at 50 times/sec, a distance of 0.5m (50cm) will create a velocity of 25m/s which is close to our 50mph.


The car responded and moved but just in a straight line from 0 to 56mph in a single 20ms frame which caused a sharp rise in acceleration. The result of this was a jerk which would be very uncomfortable for any people in that car. For a comfortable ride, the total acceleration should be well below 10m/s. I also had to comment out a line of code: auto sensor_fusion=j[1][“sensor_fusion”]; for it to compile. For now I dont know what it does really but the car moves. Great

One major issue to the problem above was that the car was veering off the road in just a straight line. We need to make sure that the car stays within the lane and for that we will opt for frenet cordinates which give us the distance and deviation values which we can work with to ensure that the vehicle stays on the lane.

See part 2 for the next update.