Abstract: A method for quickly testing stepping motors (10). The motor phases (.PHI.A-.PHI.C) are connected in series, and a constant current is applied to the phases. The rotor (12) of the motor (10) under test is rotated unidirectionally at a constant speed, and the voltage drop across each phase is measured and converted into back EMF. The back EMF is then analyzed to determine a characteristic of the motor (10), for example stepping accuracy of each of the phases, or related torque information, and the result of the analysis is then compared with a predetermined motor parameter to provide comparison data or a signal of a pass or fail condition based upon the comparison.

Abstract: A stepper motor damping control system. Damping is performed by switching the power supply connection(s) of energized motor phase windings alternatively ON and OFF at a predetermined relatively high fixed rate. Said switching is performed using a clock signal information for switching one way and an information denoting equality between a voltage substantially proportional to the current flowing through said motor phase windings with a predetermined sawtooth sloped reference signal synchronized with said clock signal for switching the other way.

Abstract: In a daisy wheel or rotary print wheel typewriter, a single motor is employed to accomplish both ribbon lift and feed for typewriter ribbon and correction ribbon loaded in a cartridge assembly. A single motor drive moves the cartridge assembly support about an axis to present the typewriter ribbon or the correction ribbon to the print point at the print line. When the elevation of the cartridge assembly about the axis is such to permit normal typing upon the typewriter ribbon, only the feed ratchet for the ribbon is engaged. Alternatively, when the rotation is greater, for example, for typing on the correction ribbon, the added elevation of the cartridge assembly effects disengagement of the normal ratchet feed for the typewriter ribbon while allowing advancement of the correction ribbon.