Development of High-Precision and High-Resolution Servo-Controllers, That Have High Noise-Rejection Ability

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Maximum speed of high-resolution controllers for NC machines and robots is not high enough to avoid misoperation under strong electrical noise environment. Because the controllers require low-pass filters whose cutoff frequency is sufficiently low for removing electrical noise involved in two-phase signals obtained from position sensors such as rotary or linear encoders. If resolution of encoder becomes higher, the output of two-phase signals becomes lower, and S/N of two-phase signals decreases as the resolution increases. This means that we must use the low-pass filters to work the controller without misoperation.This research project developed a high-speed and high-resolution servo-controller that has high noise rejection ability by using two-phase type PLL proposed by T.Emura. This two-phase type PLL can make the cutoff frequency of low-pass filter extremely higher. Therefore, we can raise the speed of servo-controller. First, an analog type servo-controller was made for trial. Though the analog type has very good characteristics, it has a weak point that its circuit is very complex and making cost is very expensive. Therefore, next, a digital type servo-controller was made for trial, because the circuits of digital one is simple and the making cost becomes lower.Performance of the digital type servo-controller was tested, and experimental results showed that it has very good characteristics in resolution, operational speed, noize rejection ability, etc. This means that very excellent results was obtained by the project of this grant-in-aid.