Problem while restoring controlfile of RAC database

I have backed up my rac database and started my target database in nomount but when i try to restore my controlfile from the backup i receive this error :

no AUTOBACKUP found or specified handle is not a valid copy or piece

The script for the backup is OK :

RUN { ALLOCATE CHANNEL ch00 TYPE DISK FORMAT '/orabackup/rman/PR2/%d_DB_%u_%s_%p';

set controlfile autobackup format for device type disk to "/orabackup/rman/PR2/cf_homedb.%F";

backup filesperset 4 INCREMENTAL LEVEL 0 AS COMPRESSED BACKUPSET database;

sql "alter system archive log current"; release channel ch00;

ALLOCATE CHANNEL CH01 TYPE DISK FORMAT '/orabackup/rman/PR2/al_%U';