Control System Block Diagram; Motor Unit Control; Pattern Generator - Baby Lock BL7800 Service Manual

4.

CONTROL SYSTEM BLOCK DIAGRAM

Control system block diagram
5.

MOTOR UNIT CONTROL

The main motor for the sewing machine is required to smoothly change from low speed to high speed without any
fluctuations due to load or temperature changes. To fully comply with this requirement, this model adopts PWM
control using FET.
6.

PATTERN GENERATOR

For conventional sewing machines, the pattern was generated by rocking the needle bar and the feed regulator by
means of a pattern cam onto which the pattern data had been mechanically engraved. In contrast to this, this model
stores the data electronically in memory and uses a feed pulse motor, and a zigzag pulse motor to directly rock the
needle bar and the feed regulator to generate the pattern. In addition, the pulse motors must move the position of
the needle while the needle is raised and stop it in the correct position (and similarly, they must move the position of
the feed regulator while the needle is lowered). Thus, highly-precise positioning and a fast response speed are
required. Because of this, the feed pulse motor, and a zigzag pulse motor were adopted, and a simple open-loop
structure circuit was employed.
Block diagram of pattern generator control
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