Drive synchronisation

I have one query regarding the logo plc

I have to synchronize two drive of overhead conveyor which is 500 meter long.For synchronization i wil send the same analog voltage for both drives.but for error detection two proximity sensors are mounted on sproket of 2 drive.so i have to count that pulses for the confirmation that both drives are synchronized & chain is not broken.

The speeds variation are 5 speed through switch.