PID control

pid

 * http://blog.solutions-cubed.com/pid-motor-control-with-an-arduino/ position control pid with dc motor.
 * http://www.solutions-cubed.com/motor-control/

github
https://github.com/X-Sim/X-PID-Arduino-PID-motor-control, http://www.x-sim.de/forum/portal.php GUI interface for tuning

Journals
https://www.researchgate.net/publication/285759625_Optimal_PID_controller_design_through_swarm_intelligence_algorithms_for_sun_tracking_system