Eighteen HBMDF-2Swater-proof bending load cellswere combined
and installed to measure the forces between the spar and torus as
shown in Fig. 6. These load cells rigidly connected the two bodies and
measured the total forces and moments in the global x, y and z directions.
The eighteen load cells were installed at six positions and for
each position, there were three load cells combined. Three of the
positions were located on the top of the torus and they were 120
degrees apart with respect to the vertical axis of the cylinder; the
other three positions were located on the bottom of the torus with the
same x and y coordinates of the top ones. At each position, three load
cells were combined orthogonally to measure the forces in three local
directions. The total forces along the three global directions were then
calculated from these load cell measurements. For each load cell, the
measured force was assumed to be applied on the center of the load
cell, and then the corresponding moment can be derived by knowing
the distance of the force applied position to the origin of the coordinatesystem. For a single load cell, the nonlinearity, the hysteresis error and the creep over 5 mins are all between −0.05% to +0.05% of the
sensitivity.