| 摘要 |
<p>An electro-hydraulic servo valve system comprising a two-stage spool type servo valve including a first stage comprising an electrical force motor and a second stage including a spool for controlling flow to an actuator. The force motor is operable upon receipt of a command electrical signal to move the spool. A first feedback is operable to cause the force motor to stop the movement of the spool. A second feedback is also operable to stop the movement of the spool at a predetermined position. The second feedback has a greater gain than said first feedback so that it normally dominates in the system. The second feedback comprises a pair of identical electrical sensors connected in parallel, and operable by movement of the spool. A comparator circuit compares the electrical signals from the sensors and is operable when the signals deviate from one another by a predetermined amount to disable the second feedback so that the first feedback will function permitting the electro-hydraulic servo valve system to operate without the second feedback.</p> |
