In some cases especially hardware, it is essential that PID tuning is done safely.

I've implemented this reinforcement learning algorithm in C++ for safely tuning a PID controller on a hardware system with successful results i.e. has been successfully deployed at customer sites for in-situ tuning.

https://github.com/befelix/SafeOpt

http://papers.nips.cc/paper/6692-safe-model-based-reinforcem...