Kodak 800 SERIES service manual Servo Motor Controller

NovaJet 800 Series Service Manual

Servo Motor Controller

GATE ARRAY

MOTOR

DRIVER

MAIN PWA

SERVO

CONNECTOR

CARRIAGE CONNECTOR

SERVO MOTOR

ENCODER

CARRIAGE

Figure 2-8. Servo Motor Controller.

The Carriage Assembly is driven by the Servo Motor. The speed of the Carriage Assembly is controlled by varying the duty cycle of the signal applied to the controller. The microprocessor checks the position of the Carriage Assembly approximately 1,000 times per second (during the servo interrupt). It then updates the PWM (pulse width modulator) register in the gate array which sets the duty cycle to make adjustments to the Carriage Assembly speed. A linear optical encoder is used to monitor the Carriage Assembly position.

The optical encoder strip runs the length of the Stabilizer Bracket and contains 150 lines and spaces per inch. Thus there are 300 edges per inch. The detector circuit actually consists of two optical edge detectors. They are separated from each other by one half the width of one of the optical lines on the encoder strip. This allows 4 evenly spaced pulses to be developed for each line on the encoder strip. This is known as quadra- ture signals. It gives an effective resolution of 600 lines per inch. See Figure 2-9 for a graphical representation of quadrature signals.

Maximum velocity of the Servo Motor is 46.6 inches per second (IPS). Servo Motor life is rated to 2.8 million cycles or approximately 2800 plot hours.

Theory of Operation 2-13