Aimin Liu Yaru Liang Shang Gao Jing Wang The Method of PID Parameter Optimization Based on Modified Linear Quadratic Optimal Control in the Linear DC Motor. 81-89 2007 ICIC (3) http://dx.doi.org/10.1007/978-3-540-74282-1_10 conf/icic/2007-3 db/conf/icic/icic2007-3.html#LiuLGW07