WASET
    Santosh Kr. Choudhary,  LQR Based PID Controller Design for 3-DOF Helicopter System.   journal   = {International Journal of Electrical and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    September 2014, vol. 92(8). 1498 - 1503
    [viewed 25 April 2024]. Available from: https://publications.waset.org/pdf/9999411.