8.3 Residual moments

When support is distributed between both sides of the body, Ergoniza Intelligent calculates loads along the upper chain, beginning at the wrists and proceeding successively through the elbows, shoulders, and L5/S1 joint. This procedure determines the force and moment transmitted to the pelvis from the upper body.

Independently, loads along the lower chain are calculated from the reaction forces determined at the contacts with the floor, following the procedure described in Section 7. The calculation proceeds from the ankles toward the knees and hips, as shown in Figure 32 (B), and determines the actions transmitted to the pelvis from the lower limbs.

Under static-equilibrium conditions, the resultant moment at the pelvis obtained from the upper chain should be compatible with that obtained from the lower limbs. However, the distribution of reactions among the different supports and the simplifications used to represent the contacts may produce a discrepancy between the two results. Ergoniza Intelligent uses this difference to determine the residual moments. For rotation about the vertical axis, the moment produced by the horizontal components of the external forces is also taken into account.

Once calculated, the residual moments are distributed among the active support areas in proportion to the portion of the total load supported by each one. These moments are incorporated into the calculation of the lower-limb joints to close the overall equilibrium of the model. They do not represent newly measured external loads, but rather compensation terms derived from the calculation procedure. Their values are shown under Residual moments in the Support reaction loads panel (Figure 30) described in Section 7.8.