Yangquan Chen Kevin L. Moore Relay feedback tuning of robust PID controllers with iso-damping property. 23-31 2005 35 IEEE Transactions on Systems, Man, and Cybernetics, Part B 1 http://dx.doi.org/10.1109/TSMCB.2004.837950 db/journals/tsmc/tsmcb35.html#ChenM05