Qing Zheng Kiran K. Chedella Weifeng Xu Liying Wu Reduced-order active disturbance rejection control for induction motors. 1139-1144 2011 CCA http://dx.doi.org/10.1109/CCA.2011.6044421 conf/IEEEcca/2011 db/conf/IEEEcca/IEEEcca2011.html#ZhengCXW11