Motion controller with remote linking
AssigneeAllen-Bradley Company, Inc.
InventorsMichael A. Fugere, David E. Halpert
Life of this patent
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Abstract
Multiple motion controllers for controlling servo motors are connected by a digital communications link so that controlled axes of the motion controllers may be slaved together regardless of their physical proximity. A given controller broadcasts position or command signals on the communications link in response to a request report message from any another controller. A second request report message may stop the broadcasting to conserve link capacity. Time shifting implicit in the link messages is corrected by estimating the velocity of the master axis and extrapolating the position to the local axes' time of updating.
Claims3
A method of controlling a servo motor unit receiving command signals from a slave motion controller in response to axis signals indicating position from a master motion controller remotely located and connected to the slave motion controller via a digital communications link, the link communicating the axis signals from the master motion controller to the slave motion controller, the method comprising the steps of:
- causing the slave motion controller to read a local clock at the time of receipt of each axis signal;
- estimating from the axis signal the velocity of the axis associated with the axis signals;
- causing the slave motion controller to read the local clock again immediately prior to updating the command signals to the motor from the slave motion controller;
- adjusting the axis signal according to the time difference indicated by the two readings of the local clock and the estimated velocity;
- and
- updating the command signals to the motor from the slave motion controller according to the adjusted axis signal.
Dependencies are inferred from the claim text.