Complex sentence: Force feedback has been implemented experimentally in some excavators and is useful when excavating mixed materials such as large rocks embedded in silt or clay, as it allows the operator to "feel" and work around unseen obstacles, enabling significant increases in productivity.
Split into simpler sentences: Force feedback has been implemented experimentally in some excavators and is useful when excavating mixed materials such as large rocks embedded in silt or clay. It allows the operator to "feel" and work around unseen obstacles, enabling significant increases in productivity.