Hiroyuki Kawai Toshiyuki Murao Ryuichi Sato Masayuki Fujita Passivity-based control for 2DOF robot manipulators with antagonistic bi-articular muscles. 1451-1456 2011 CCA http://dx.doi.org/10.1109/CCA.2011.6044445 conf/IEEEcca/2011 db/conf/IEEEcca/IEEEcca2011.html#KawaiMSF11