Holding Device with a Chain Net and its Modeling

A holding device with a chain net developed for automating and cutting labor in lifting has been used to remove wave-dissipating blocks and to recover hydrofoils from the seabed. It operates simply, but lifting safety must be rigorously checked, especially for heavy objects, so lifting models are highly desirable. We discuss modeling holding a four-leg block with the device, showing that its geometrical and static constraints are expressed as a set of nonlinear simultaneous equations having the same number of unknowns. From the solution to the simultaneous equations, the holding configuration and chain tension useful in determining whether the device can hold the block are obtained. Our proposal is also applicable to a four-leg block with a broken leg.