Slide
5
The
rotational servohydraulic actuator is used to apply torsional loads.
It is driven by high pressure hydraulic fluid. The actuator has
a built-in rotary variable differential transducer, or, RVDT to
measure rotation. An attached servo-valve controls both the direction
and volume of the hydraulic fluid into and out of the actuator.
Vane type rotary actuators have the smallest possible weight to
size ratio, fast response with no backlash and long life. The figure
on the right shows the working principle of a double vane rotary
actuator. Let's look at the mechanism of anticlockwise rotation
of the actuator. High pressure oil is pumped inside the actuator
from port I and the shaft begins to rotate in the anticlockwise
direction. Opposite chambers in the actuator communicate through
a hole in the shaft. Low pressure oil flows out the actuator through
port II. Similarly, for clockwise rotation the direction of fluid
flow is reversed.
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