Error detection and recovery in flexible assembly systems

This study investigates error detection and recovery for flexible assembly systems. A method for error recovery based upon an expert system is presented. An expert system is used to control the assembly cell, but the robot controller controls the assembly operation. This ensures adequate speed of the assembly cycle. The robot signals the expert system when an error occurs. It determines the cause of the error and recommends a preprogrammed recovery procedure to correct the error automatically. The system is flexible and new error recovery routines are easily added to the system. The proposed method was implemented in the Mark II assembly cell at 1VF-KTH in Stockholm. The reliability of the assembly cell increased considerably after installation of the error detection and recovery system. The error detection did not affect the cycle time and error recovery took less than 10 seconds on average.