| 摘要 |
<p>A drive mechanism comprising a power driven screw (16) and a nut means (17) co-operating with the screw includes a device for the correction of backlash prevailing between the screw and the nut means. The correction takes place electronically by modification of two pulse trains (A, B) which are generated by a pulse generator (19) which is synchronized with the movement of the screw. Out of the two pulse trains information as to position and direction of movement is derived for a movable unit (11), which is connected to the nut means and which, for instance, can be a printing unit in a printer or a typewriter. A measured or estimated value of the backlash is digitally stored with a resolution of one quarter of the period of the pulse trains. This resolution is four times the smallest distance through which the movable unit can be moved. The two pulse trains (A, B) are combined in a signal modifying device (21) in four different ways and in a selected one of two opposite successions to perform displacement of a predetermined flank (8) in one (B) of the pulse trains as many steps of one quarter of the period as correspond to the stored backlash value and in a direction corresponding to the selected succession.</p> |
