9 December 1983 The Motion Control System For The Large Optics Diamond Turning Machine (LODTM)
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Abstract
LODTM, built by LLNL for DOD, is a precision vertical lathe used to diamond turn large optical parts (to 64" diameter) to 1 μinch rms figure error. The LODTM motion controls require precision sensors, precision servos, and a wideband (330 Hz) real time computer. Position is sensed to 1/40 μinch resolution by laser interferometers and differential capacitance gauges. Precision servos operating at 1/10 μinch resolution and at low velocities with zero backlash are required. A unique Fast Tool Servo (FTS), located close to the diamond tool, adjusts the final tool position. The LODTM controls coordinate the X, Z, and FTS servos to cause the tool to move on a specified contour and at a specified feedrate in the X-Z plane. The part floppy diskette commands this motion with a linear CNC and real time (32-bit) computer. During each 1.5 ms sample time, the computer must DMA 14 sensor readings into memory, calculate the X and Z Tool Coordinates, calculate the FTS input, output the following errors, output the FTS input, store "flight recorder" information, and check for anomalies.
© (1983) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Howard K. McCue, "The Motion Control System For The Large Optics Diamond Turning Machine (LODTM)", Proc. SPIE 0433, Contemporary Methods of Optical Manufacturing and Testing, (9 December 1983); doi: 10.1117/12.936791; https://doi.org/10.1117/12.936791
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KEYWORDS
Servomechanisms

Fourier transforms

Real-time computing

Sensors

Control systems

Capacitance

Diamond

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