| 摘要 |
<p>An electro-hydraulic servo valve system comprising a two-stage spool type servo valve including a first stage (20) comprising an electrical force motor (12) and a second stage (21) including a spool (28) for controlling flow to an actuator (14). The force motor (12) is operable upon receipt of a command electrical signal to cause to move the spool (28). A first feed-back (16) is operable to cause the force motor (12) to stop the movement of the spool (28). A second feedback (19) is also operable to stop the movement of the spool (28) at a predetermined position. The second feedback (19) has a greater gain than said first feedback (16) so that it normally dominates in the system. The second feedback (19) comprises a pair of identical electrical sensors (35, 36) connected in parallel, and operable by movement of the spool (28). A comparator circuit (18) compares the electrical signals from the sensors (35, 36) and is operable when the signals deviate from one another by a predetermined amount to disable the second feedback (19) so that the first feedback (16) will function permitting the electro-hydraulic servo valve system to operate without the second feedback (19).</p> |
