/CarND-PID-Control-Project

Primary LanguageC++

CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

Param tuning explanaition

In this project we have made use of a PID controller to drive a car.

To do that it has been implemented a C++ class (PID). The properties of this class are the PID coefficients and errors.

The class also implements two methods. The first one, called UpdateError, updates the proportional, differential and integral errors of the PID controller.

The proportional error is updated according with the new CTE value. The differential error is the substraction between the previous CTE and the current one. The integral error is the sum of the all CTE.

The TotalError method applies the following formula to calculate the total error of the controller.

error = -Kp * p_error - Kd * d_error - Ki * i_error

The key point in this project is to find the appropriate values for the coefficients.

Because of the total error it is calculated with three components, it is really important to understand how each one affects to the resulting estimation.

If the proportional coefficient is too high, the car starts to oscillate and it cannot converge.

In other hand, the integral coefficient must to be the lowest because it represents the sum of all errors. If it is too high, the car starts moving in circles.

Finally, the differential coefficient needs to be the greater one in order to detect rapid oscillations in the CTE that could represent curves in the road.

Mentioned that, the final chosen values are:

double Kp_pid_steering = 0.1;  // proportional coefficient
double Ki_pid_steering = 0.005;  // integral coefficient
double Kd_pid_steering = 4.0;  // differential coefficient

The car sometimes oscillates a little bit, but it quickly changes the steering angle and takes the right direction again. Thanks to the high kd and ki values, it does not go out of the road, even if the car is entering a curve fast.

It is also implemented a PID controller to set the throttle of the vehicle. It works fine, but not too much in comparision with the constant throttle scenario.

Depending on the CTE and the given maximum speed, the algorithm defines a target speed. After that, the controller calculates the error considering the CTE as the subtstraction between the current speed and the target speed.

Generally speaking, the car behaves properly the majority of the time and it does not go out of the road. It also gets a faster speed, but it sometimes oscillates too much and it could not be considered a safe driving.

Dependencies

Basic Build Instructions

  1. Clone this repo.
  2. Make a build directory: mkdir build && cd build
  3. Compile: cmake .. && make
  4. Run it: ./pid.

Editor Settings

We've purposefully kept editor configuration files out of this repo in order to keep it as simple and environment agnostic as possible. However, we recommend using the following settings:

  • indent using spaces
  • set tab width to 2 spaces (keeps the matrices in source code aligned)

Code Style

Please (do your best to) stick to Google's C++ style guide.

Project Instructions and Rubric

Note: regardless of the changes you make, your project must be buildable using cmake and make!

More information is only accessible by people who are already enrolled in Term 2 of CarND. If you are enrolled, see the project page for instructions and the project rubric.

Hints!

  • You don't have to follow this directory structure, but if you do, your work will span all of the .cpp files here. Keep an eye out for TODOs.

Call for IDE Profiles Pull Requests

Help your fellow students!

We decided to create Makefiles with cmake to keep this project as platform agnostic as possible. Similarly, we omitted IDE profiles in order to we ensure that students don't feel pressured to use one IDE or another.

However! I'd love to help people get up and running with their IDEs of choice. If you've created a profile for an IDE that you think other students would appreciate, we'd love to have you add the requisite profile files and instructions to ide_profiles/. For example if you wanted to add a VS Code profile, you'd add:

  • /ide_profiles/vscode/.vscode
  • /ide_profiles/vscode/README.md

The README should explain what the profile does, how to take advantage of it, and how to install it.

Frankly, I've never been involved in a project with multiple IDE profiles before. I believe the best way to handle this would be to keep them out of the repo root to avoid clutter. My expectation is that most profiles will include instructions to copy files to a new location to get picked up by the IDE, but that's just a guess.

One last note here: regardless of the IDE used, every submitted project must still be compilable with cmake and make./