Regarding　torsional　vibrations　during　coaxial　transmission,　its　structure　was　analyzed　and　a　mathematical　model　was　establised,　meanwhile　a　multi　mass　rotating　test　platform　was　built　to　study　torsional　vibrations　in　coaxial　transmssion.　Secondly,　input　command　shaping　method　was　used　to　filter　input　signals.　Traditional　input　shapers,　to　some　extent,　rely　on　modes　and　the　parameter　adjustment　is　more　complex.　In　terms　of　the　existence　of　input　shapers,　a　parameter　self-tuning　method　was　proposed　based　on　PSO,　and　by　transfer-function　transformation,　it　can　achieve　online　signal　collection　and　offline　optimization,　avoiding　system　oscillation　aroused　easily　by　online　optimization,　while　offline　optimization　does　not　require　modeling　with　vibration　free　and　high　accuracy.　Different　algorithms　were　verified　on　test　platform　and　the　result　shows　that　compared　to　traditional　trap　filter　and　other　filters,　the　input　shaper　greatly　restrains　system　torsional　vibrations　meanwhile　compromises　its　dynamic　functions　as　little　as　possible,　and　it　achieves　fast　vibration-free　system　response.　©,　2014,　Editorial　Department　of　Electric　Machines　and　Control.　All　right　reserved.