Patrick-Woo/Term2-P4-CarND-PID-Control

CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

Udacity CarND Project 9 - Term 2, Project 4

Project Basics

I use a Proportional-Integral-Derivative Controller, or PID for short in this C++ project, in order to drive a simulated car around the term 1 lake side track. The project involves implementing the controller primarily for the steering angle of the car (although I used the value from this controller to also determine throttle), as well as tuning coefficients for each PID value in order to calculate a steering angle that keeps the car on the track.

Project Steps

• Implement PID Controller for Steering
• (optional: controlling throttle as well and I unfortunately fail to perform the optional target with PID but gain the throttle value with an experiening equation, which reveals the fact the larger the steer value is, the smaller the throttle should be.)
• Optimize init parameters for each PID coefficient

Results / Reflection

A video of the simulated car driving around the lake side track can be found here.

Components of PID

• The "P" for proportional means that the car will steer in proportion to the cross-track error, or CTE. CTE is essentially how far from the middle line of the road the car is. This makes sense, as if the car is to the left of the line then you would want to steer to the right; if it is far to the left of the middle with a high CTE then you want a higher steering angle. However, if the coefficient is set too high for P, the car will oscillate a ton, as the car will constantly overcorrect and overshoot the middle. If the coefficient is too low, the car may react too slowly to curves when the car gets off-center with a higher CTE.
• The "I" for integral sums up all CTEs up to that point, such that too many negative CTEs (in this case, meaning the car has been to the left of the middle of the lane for awhile) will drive up this value, causing the car to turn back toward the middle, preventing the car from driving on one side of the lane the whole time. If the coefficient is too high for I, the car tends to have quicker oscillations, and does not tend to get up to a quick speed. A low coefficent for I will cause the car to tend to drift to one side of the lane or the other for longer periods of time.
• The "D" for derivate is the change in CTE from one value to the next. This means that 1) if the derivative is quickly changing, the car will correct itself (i.e. higher steering angle) faster, such as in the case of a curve, and 2) if the car is moving outward from the middle, this will cause the steering to get larger (as the derivative sign will match the proportional sign), but if the car is moving toward the center (meaning the derivative value will be negative), the car's steering angle will get smoothed out, leading to a more smoother driving experience. Too high of a coefficient leads to almost constant steering angle changes of large degrees, where although the car will be well-centered it can hardly move. Too low of a D coefficient will lead to the oscillations being too high with more overshooting.

Finding the right coefficients

At first, I initlize the PID as the rules below:setting the kp with 0.1 and kI kD with 0. After trying serval kp values, I add kd to the PID model and then add ki.

And when the car can go through the first turn. I use the sebstian's coordinate ascent method to tune PID parameters.

Although it was removed from the final code, I tried out different parameters, but found the values that found manually good enough under my current implementation.

So I pick up the mannual paramaters P.I.D(0.3125, 0.0025, 3.0279).

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Dependencies

• cmake >= 3.5
• All OSes: click here for installation instructions
• make >= 4.1(mac, linux), 3.81(Windows)
  • Linux: make is installed by default on most Linux distros
  • Mac: install Xcode command line tools to get make
  • Windows: Click here for installation instructions
• gcc/g++ >= 5.4
  • Linux: gcc / g++ is installed by default on most Linux distros
  • Mac: same deal as make - [install Xcode command line tools]((https://developer.apple.com/xcode/features/)
  • Windows: recommend using MinGW
• uWebSockets
  • Run either ./install-mac.sh or ./install-ubuntu.sh.
  • If you install from source, checkout to commit e94b6e1, i.e.

    git clone https://github.com/uWebSockets/uWebSockets 
    cd uWebSockets
    git checkout e94b6e1
    

    Some function signatures have changed in v0.14.x. See this PR for more details.
• Simulator. You can download these from the project intro page in the classroom.

There's an experimental patch for windows in this PR

Basic Build Instructions

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

Tips for setting up your environment can be found here

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./

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