YCSU / Udacity_SDC_T2P4_PID_Control

PID in C++

CarND-Controls-PID

Self-Driving Car Engineer Nanodegree Program

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Dependencies

• cmake >= 3.5
• make >= 4.1
• gcc/g++ >= 5.4
• uWebSockets == 0.13, but the master branch will probably work just fine

Basic Build Instructions

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

The effect of PID components

The value of K_p, K_i, and K_d was chosen by manually tuning. The tuning process is similar to twiddle but mixed with the human intelligence :D

The effect of the PID component is demonstrated by the following examples. The car drove on the same path with different coefficients.

K_p=0, K_d=0, K_i=0

When all the coefficients are zeros, the CTE increased indefinitely.

K_p=0.09, K_d=0, K_i=0

As we increased K_p, the CTE initially decreased. However, the car overshot the ideal trajectory and started to oscillate.

K_p=0.09, K_d=1.3, K_i=0

We also increased K_d. The car was able to stay on the track. Notice that there is a spike.

K_p=0.09, K_d=1.3, K_i=0.003

We also increased K_i. the amplitude of oscillation increased a bit. There is no steady state error in this case. However, if there was, K_i component would help correct this error.