Study on large radius of spherical fiducial surface of bearing of highspeed railway forming base on virtual axis

It is popular to use the method of mold grinding at home and abroad^[i] when a cylindrical roller-bearing of highspeed railway is proceeded, however it couldn’t realize a continuous processing. It’s needed to make axis of roller swing around a fixed axis and roller rotate around self-axes in order to realize a continuous processing, which needs a mechanism swinging around fixed axis. Because a diameter of spherical surface of cylindrical roller-bearing exceeds five meters, the dimension of a swinging mechanism must be very huge, which makes moment of inertia become great and limit the swinging speed. This mechanism isn’t practical. In view of this situation, a 4-RPR structure based on the theory on parallel robot was brought forward to realize a mechanism swinging around vitual axes. Its dimension and moment of inertia are so small that the continuous processing of rollers could be gotten. The direct and inverse kinematic models are established in this paper.