Precise control of the rotational velocity of brushless alternat

Details Precise control of the rotational velocity of brushless alternat Precise control of the rotational velocity of brushless alternat

1997-03-05

1999-08-03

Sircus, Brian

Electricity: motive power systems

Positional servo systems

Digital or numerical systems

318605, 318616, 318272, G05B 1929, H02P 100

Patent

active

059329866

ABSTRACT:
A brushless AC servo motor control and modified motor to minimize the rotational acceleration and deceleration of a semiconductor wafer during processing steps where fluid is applied in a thin coating on the wafer. The control utilizes sine and cosine encoder outputs of single cycle and multiple cycle per revolution to calculate motor shaft position by an inverse tangent calculation of sine and cosine ratios. Resolution of motor shaft position is greatly improved as is rotational velocity control. In response to a prediction of desired shaft position in comparison with actual position the three field currents are adjusted to change the torque applied to the rotor and shaft. In the semiconductor wafer manufacturing application the motor shaft is modified to permit vacuum attachment of the wafer to the disc that rotates with the shaft.

REFERENCES:
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patent: 4457259 (1984-07-01), Samuels
patent: 4486693 (1984-12-01), Hamati et al.
patent: 4558266 (1985-12-01), Sasaki et al.
patent: 4591774 (1986-05-01), Ferris et al.
patent: 5138564 (1992-08-01), Jong et al.
patent: 5309075 (1994-05-01), Yokoe et al.

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