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The SOAR Mount Control Unit Upgrade Project seeks to replace the current MCU in the SOAR telescope. The new control unit will be based on the National Instruments cRIO-9039 controller, which will allow to improve the telemetry, improve fault detection and use new digital control techniques.
This will allow a more compact and robust MCU. This paper introduces the project, shows the control architecture and the current status of the new MCU implementation.
In order to investigate the response to the telescope mount servo control, to wind induced disturbances, we have instrumented the 4m Blanco Telescope mount, upper secondary ring, with a novel 2-axis direct wind force sensor, sampled at 200 Hz, using inexpensive pocket digital scale type load cells, this combined with a small surface area of 0.00375 m2, we have obtained wind pressure noise values of 0.4 Pa-rms.
Our investigation will compare the Power Spectral Density (PSD) of the wind disturbance forces, with the expected Kolgomorov model, and explore the correlation between wind disturbance forces, and mount tracking jitter.
Also we will establish under what dome, wind direction, and wind speed conditions the increased mount tracking jitter, could affect science image results, and cause an increase in image ellipticity, and FWHM. This information should help observers, in taking appropriate measures, to minimize the wind induced image degradation in the future.
During observing, or Active Mode2, the M1M3 mirror is supported by an array of 156 support and figure control actuators consisting of 268 pneumatic cylinders that react to gravity and inertial loads and provide figure error correction. Load cells on the actuators measure forces that are communicated to the M1M3 control system. However, the figure actuators do not define the mirror position. This is defined with six axially stiff linear actuators called hardpoints3 arranged in a hexapod pattern to restrain rigid body motion of the mirror in a kinematic fashion. By adjusting the length of each hardpoint, the mirror can be adjusted in all six degrees of freedom with respect to the cell. Displacement sensors and load cells on the hardpoints communicate displacements and forces to the control system, which processes the telemetry and issues force corrections to the figure actuators to zero out any loads and moments on the hardpoints.
In Static Mode, the M1M3 mirror is no longer supported by figure actuators and the position sensing of the hard point hexapod is inactive. A second support system consisting of 288 wire rope isolators called Static Supports come into play. The static supports mechanically capture the mirror whether in Active or Static Mode and in the event the mirror experiences motion beyond the active motion range in any direction. The static supports also safely support the mirror during seismic events for all elevation angles. In active mode, the static supports do not contact the mirror and thus, do not affect the mirror positioning or figure.
This paper focuses on the detailed design, development, testing, integration, and current status of the M1M3 pneumatic figure actuators.
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