an on-off limiting member fixedly connected with the first member,

a drive fixation apparatus, which comprises a rear sleeve, a drive structure and a second gear, wherein the rear sleeve is connected with the on-off limiting member through a limiting assembly, the drive structure is fixed in the rear sleeve and connected with the second gear, the second gear and the first gear are eccentrically arranged, and under a limiting action of the limiting assembly, the rear sleeve rotates, in relative to the on-off limiting member, between a first position and a second position on the on-off limiting member; the limiting assembly comprises a sliding slot and a locating pin fitting with the sliding slot, the sliding slot is formed in the on-off limiting member and extends circumferentially along a center of the on-off limiting member, and two tail ends of the sliding slot are separately formed with the first position and the second position; and the locating pin is limited in the sliding slot and fixedly connected with the rear sleeve, and an elastic damping member for increasing a frictional force between the locating pin and the on-off limiting member is also arranged between a front end face of the rear sleeve and a front end face of the on-off limiting member; and

wherein the rear sleeve is configured to rotate to the first position such that the second gear meshes with the first gear, the drive structure drives the first gear to rotate through the second gear, the first member is in electric mode, and the rear sleeve is also locked and fixed to the on-off limiting member through a locking structure, to maintain a meshing state of the second gear and the first gear; and wherein the rear sleeve is configured to rotate to the second position such that the second gear is separated from the first gear, and the first member enters a manual mode.