Analysis of Force Characteristics in Foot Operations Using Isometric Device

The lower limbs, which have multiple degrees of freedom, can be used to manipulate a robot or an object in a virtual environment. Such manipulation can be achieved by measuring the direction of force exerted by the lower limbs using an isometric device equipped with a force sensor. This study experimentally investigates the differences between the intended and actual directions of force exerted by the lower limbs when operating an isometric device. The results of experiments conducted using 48 force directions indicate that there are five prominent characteristics in the differences between the intended and actual force directions. For example, when the intended force is the backward direction, an upward force component is also generated. In addition, we conducted a musculoskeletal analysis to analyze the causes of the differences between the intended and actual force directions and calculated the metabolic energy consumption ( $E_{m}$ ). The results confirm that some force directions result in lower $E_{m}$ and show that the actual force directions measured in the experiment tend to be close to the force directions that resulted in lower $E_{m}$ . This suggests that reducing $E_{m}$ is one of the causes of the differences between the intended and actual force directions.