Motor speed control apparatus and motor speed control method

摘要

A method and apparatus for controlling the speed of a motor for a hard disk drive. The motor speed control apparatus includes a speed feedback controller which uses selected feedback coefficients. The feedback coefficients are suitable to the rotor assemblies having different moments of inertia. A driving force is applied to the motor to rotate the installed rotary assembly. A detector determines the period of rotation and a period of subsequent rotation at the initiation of the motor. An identification means identifies a rotor assembly installed on the motor from said detected period. The time constant of said motor is a function of the moment of inertia of the rotor assembly installed on the motor and can be obtained from the period of rotation and the period of subsequent rotation at the time said motor is started up. A selector chooses the appropriate feedback coefficients for the identified rotor assembly. The rotor assembly varies its moment of inertia according to the number of the magnetic disks that form said rotor assembly and provides the motor speed control apparatus. Accordingly, an optimum startup time and a high rotation accuracy is obtainable at low cost while consuming low power and downsizing.