| 摘要 |
ION ELECTRONIC SPEED CONTROLLER FOR AN ALTERNATING-CURRENT MOTOR A high precision controller for a multi-phase ac electrical motor that is subject to a large inertial load. The controller was developed for and is particularly suitable for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. A timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. In the preferred embodiment, the motor control signal is a weighted linear sum of a speed error signal, a phase error signal, and a drift error signal, the magnitudes of which are recalculated and updated with each revolution of the motor shaft. The speed error signal is generated by a vernier-logic circuit which is drift-free and highly sensitive to small speed changes. The phase error signal is also digitally computed with adjustable sensitivity around a zero mid-scale value. The drift error signal is generated by long-term counting of the phase error and is used to compensate for slow changes in the average friction drag on the motor. The stator windings of the motor are driven by two power amplifiers which are controlled by the motor control signal. |
