Summary of the Actuators of the FAST Active Reflector

2225 hydraulic actuators are used to support the deformation of FAST(Five-hundred-meter Aperture Spherical radio Telescope) active reflector. For hydraulic actuator of different design schemes, the design based on bi-directional gear pump is selected based on prototype test, reliability and maintainability. Of the 2225 actuators, 2075 are designed to meet maximal load of 7 tons, 140 of load 10 tons, and 10 of load 15 tons. In operation of observation, for each of the time ticks(Interval 500ms), the piston position precision of the hydraulic actuator is controlled to be better than 0.25mm, which is over ten times better than the typical node precision requirement of the active reflector. Each of the actuator is physically connected to the control room by optical cable for transmission of control commands and actuator status. Each of the actuators is further designed to meet the shield effect requirement for the radio telescope. With both good reliability and easy maintainability, the actuators worked well to support the scientific observation of the giant telescope.