Theoretical difference of the backd

Theoretical difference of the backdrivability by the vibration direction In this study, we used vibrations to achieve friction reduction in the worm gear. There are two types of friction reduction phenomena. The first type is caused by the jumping of the tooth surface of the worm gear by the vibration, which generates periodic conditions of contact and non-contact, and during the non-contact condition, it loses friction. The second type is caused bythe vibration (oriented parallel to the lead angle), which exceeds the friction force. In the article [15] the bearings that hold the shafts of the worm gear are held by the rubber parts, and the shafts can vibrate in all directions. However, the vibration that changes the length between the shafts of the worm screw and the worm wheel is not recommended, because it significantly displaces the contact point from the pitch circle of the gear. Moreover, such motion causes a misalignment of the axes of the shafts. Therefore, in this paper we will discuss the vibrations caused in the direction of the axis of the worm screw and of the worm wheel [16], as such vibrations do not cause a change in the gap of the gear shafts. The specifications of the worm gear (composed of a worm screw and a worm wheel) are shown in Table 1. We assembled the worm gear, and a pulley was installed to the shafts of both the worm screw and the worm wheel. First, a weight was hung on the pulley of the worm wheel to generate a contact force between the worm gear teeth. Next, the mass of the weight hung from the worm screw was increased slowly, and the weight initiated rotation of the worm gear was measured. Accordingly, we obtained the coefficient of static friction µ shown in Table 1.