Control files error

I use Oracle 11g R2 and when I try to start my database from sqlplus, I get this error:

ORA-00205: error in identifying control file, check alert log for more info        

The alert log file has this:

ORA-00210: cannot open the specified control file
  ORA-00202: control file: '/u01/app/oracle/product/11.2.0/dbhome_1/dbs/ora_control1'
   ORA-27037: unable to obtain file status