title: Note: high precision angle generator using multiple ultrasonic motors and a self-calibratable encoder.
abstract: We present an angle generator with high resolution and accuracy, which uses multiple ultrasonic motors and a self-calibratable encoder. A cylindrical air bearing guides a rotational motion, and the ultrasonic motors achieve high resolution over the full circle range with a simple configuration. The self-calibratable encoder can compensate the scale error of a divided circle (signal period: 20") effectively by applying the equal-division-averaged method. The angle generator configures a position feedback control loop using the readout of the encoder. By combining the ac and dc operation mode, the angle generator produced stepwise angular motion with 0.005" resolution. We also evaluated the performance of the angle generator using a precision angle encoder and an autocollimator. The expanded uncertainty (k = 2) in the angle generation was estimated less than 0.03", which included the calibrated scale error and the nonlinearity error.
authors: Center for Length, Korea Research Institute of Standards and Science, 267 Gajeong-ro, Yuseong-gu, Daejeon 305-340, South Korea.
authors: Jong-Ahn
authors: JA
authors: Kim
authors: Jae Wan
authors: JW
authors: Kim
authors: Chu-Shik
authors: CS
authors: Kang
authors: Jonghan
authors: J
authors: Jin
authors: Tae Bong
authors: TB
authors: Eom