New Servo System for 14m Telescope

2017. 12. 20. Changhoon Lee

1. Overview

The servo system of TRAO 14 m telescope has been operating since about 1986. It is operated as a single-dish radio telescope and is expected to continue operation into the future, both for research and for educational uses. TRAO has currently finished the important system upgrades, such as the installation of a more sensitive 16 pixel SEQUOIA-TRAO receiver, the replacement of the radome, and the computer system to improve system performance. And the upgrade of the servo system was also completed in December 2017.

Old Antenna Control Unit and Drives

2. New Servo Control System Block Diagram

3. Requirements

• Four brushless AC servo motors employing the current gear boxes and brakes • Four new servo drives for running the motors • Two absolute angle optical encoders, 29 bit Heidenhain RCN 8510 • Azimuth range 720 degrees, slew speed 1.5 degree per second, zero backlash • Elevation range 90 degrees, slew speed 0.5 degree per second, zero backlash • New hardware limit switches and azimuth turn indicator • Ability to track the axis with 2 arc seconds accuracy at the encoders • Settling time of < 5 seconds after start of damping

Installed AC servo motor, Servo Drives and I/O system, 29 bit encoder for EL-axis

3. Performance Test Results

Settling time test results

OTF tracking test results

Tracking accuracy test results at EL 30°(top left), 45°(top right), 60°(down)