Aiming　at　the　improvement　of　machining　stability,　a　new　on-line　chatter　control　method　is　presented,　which　is　to　actively　adjust　the　machining　dynamics　in　process　based　on　the　application　of　smart　materials　in　manufacturing　systems.　For　on-line　chatter　avoidance　in　boring,　an　adaptive　control　system　is　given,　which　employs　a　novel　design　of　the　boring　bar　containing　a　smart　material,　electrorheological(ER)　fluid.　This　control　system　successfully　suppresses　boring　chatter　by　automatically　adjusting　the　dynamics　of　the　bar　according　to　the　information　from　the　monitored　sensor　signal.