Electricity: motive power systems – Positional servo systems – With particular 'error-detecting' means
Patent
1983-09-06
1986-06-10
Dobeck, B.
Electricity: motive power systems
Positional servo systems
With particular 'error-detecting' means
318625, 318480, 350271, 250229, 310231, G05B 106
Patent
active
045945390
ABSTRACT:
A light valve has a pair of rotating vanes for controlling the cross section of a light beam passing between the vanes. The vanes rotate on corresponding shafts, each controlled by its own integral motor. Separate feedback control systems produce electrical control signals to each motor for rotating each shaft independently of the other to control the desired phase angles of the vanes. In one embodiment, both motors are permanent magnet direct current servo motors in which the wound armature is an integral part of each shaft. A stationary magnetic field generated by permanent magnets is common to both motors. Power is supplied to each armature by a pair of thin, parallel, flexible, electrically conductive strips extending from an end of each shaft. The conductive strips reduce the torque on the shaft when twisted during operation. In one embodiment, the control system produces a calibrated digital control signal from a PROM representing the desired phase angles of the rotating blades. The digital signal is converted to analog control signals compared with position feedback signals from the rotating blades and damping signals produced by blade velocity feedback signals. Error signals fed to variable gain amplifiers control the positions of the vanes. Whenever new commands are input to the variable gain amplifiers, amplifier gain is temporarily switched to a high gain mode, and after the phase angle of the shaft has stabilized, the amplifier gain is switched back to a low gain mode. The separate motors and their servo systems speed up response time and substantially reduce any tendency toward oscillations.
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