7.8 Stabilogram and distribution of reactions at the supports

Ergoniza Intelligent presents the results of the support-reaction calculation under Support reaction loads in the Exertion window and in the Stabilogram tool (Figure 30). The former shows the distribution of forces, expressed in newtons (N), and reaction moments, expressed in newton-meters (N·m), between the left and right supports and between the front and rear of each support.

The interpretation of the front and rear areas depends on the support type. When support occurs at the feet, the front corresponds to the forefoot and the rear to the heel. When one leg is supported simultaneously at the knee and foot, the front corresponds to the knee and the rear to the forefoot. When modeling seated posture in a chair, the equivalent front support corresponds to the knee and the rear support to the hip on the same side.

In the example in Figure 30, the supports correspond to the feet and the reaction forces have only a vertical component because the model is not supporting loads with horizontal components. In this particular case, the distribution of forces relative to the center of pressure satisfies equilibrium without reaction moments arising at the supports.

The bottom of the Support reaction loads section also displays the Residual moments, which are zero in the example in Figure 30. Residual moments are discussed in Section 8.3.

The Stabilogram shows the position of the center of pressure, represented by a blue circle, relative to the base of support. It also represents the support points and the geometry defining the base. The size of the markers associated with the support points is proportional to the reaction supported by each point.

Below the graph, the percentage distribution of the load between the left and right supports is shown, together with its internal distribution between the front and rear areas. The interpretation of these areas depends on the support type, as indicated above.

Ergoniza Intelligent estimates physical contact of the feet, knees, and hips with the floor from their distance to it. The Contact tolerance control sets the maximum distance at which contact is considered to exist. When seated in a chair, the equivalent knee and hip supports are established according to the model described in Section 7.7, while foot contact with the floor continues to be determined from foot position.