Device for controlling DC motor

摘要

A device for controlling a DC motor to establish a target speed, comprising: a speed setter for providing plural command values of speed of the DC motor; a speed selector for selecting one of the plural command values; a current regulator for controlling an amount of electric current to be applied to the DC motor so that a value of a feedback signal corresponding to a current speed of the DC motor coincides with the command value of speed selected by said selector; and a controller for controlling the selector to select a first command value of the plural command values for a first time span of a cyclic control time which is determined as a function of a period of the feedback signal, and to select a second command value of the plural command values for a second time span which is a remainder of the cyclic time. The target speed falls within a range defined by the first and second command values. The controller determines a ratio of the first time span to the second time span so that the target speed is established. The controller may change the first time span so that the current speed of the DC motor coincides with the target speed.