for F in * ; do NF=`echo $F | perl -lne "s/ /_/g; s/\._/./g; s/[',-]//g; print lc"` ; mv "$F" "$NF" ; done

for F in * ; do NF=`echo $F | perl -lne 's /\. /./g; s/ /_/g; print lc'` ; mv "$F" $NF ; done

for F in * ; do NF=`echo $F | perl -lne 's /\. /./; s/ /_/g; print lc'` ; mv "$F" $NF ; done

test with echo instead of mv
example removes spaces after dots, replaces spaces with _, removes ' , and -, and finally lowercases filenames

Batch rename files in directory

files, perl

Bash