Abstract: A method for controlling the rotational speed of a rotary body in which drive means for driving the rotary body is actuated on the basis of predetermined step-like speed command values corresponding to rotational angles of said rotary body. At transition points between said step-like speed command values are preset one or more intermediate speed command values so that the rotary body will change its rotational speed smoothly.

Abstract: A cam grinding apparatus has a base member, a rocking bar rockably mounted on the base member, a master cam shaft rotatably mounted on the rocking bar, and a drive motor for driving the master cam shaft in rotation. A cam shaft to be ground is supported by the master cam shaft so as to have the cam section thereof ground by a grindstone while being rocked by the rocking bar and rotated by the master cam shaft. There is provided at least one device for detecting the rotational angle of the drive motor and for detecting the phase angle of the rocking bar.