Hiromitsu Ogawa and  Manato Ono and  Naohiro Ban and  Yoshihisa Ishida,  Two Stage Control Method Using a Disturbance Observer and a Kalman Filter.   journal   = {International Journal of Electronics and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    December 2009, vol. 36(12). 2265 - 2268
    [viewed 10 May 2021]. Available from: https://publications.waset.org/pdf/5232.