Monitoring system designed to extract critical natural frequencies of a cargo ship

Abstract

A system includes several load cells, each coupled to a lashing that secures shipping containers, accelerometer cells, each coupled to a shipping container at the top of a stack, and an inclinometer cell coupled to a cargo ship. The cells are configured to transmit data to a computer. All the cells comprise a processor programmed to acquire a time series of measurements and, preferably, decompose the time series into a sum of sinusoidal signals, each having a frequency and an amplitude. Alternatively, the computer can be programmed to decompose the time series. The computer is programmed to identify the signal components caused by the roll of the cargo ship or by resonances in shipping container stacks. The computer estimates cumulated damages caused by fatigue in the lashings and/or twist locks. The system is used to trigger alarms and/or schedule maintenance.