|
| In recent years, an increasing number of synchronous
AC linear motors have been applied in linear stages of
manufacturing machines for semiconductor devices and
liquid crystal panels. Formerly, pole sensors were used
in detecting phase angles of AC linear motors in most
cases. Although there is a method for detecting phase
angles without using a pole sensor, the method has disadvantages
such as vibrations of the mechanical system
caused by the thrust command for detecting phase
angles and the inability to the specify travel distance
of the machine being detected. In this report, SHI Control
Systems, Ltd. (SCS) describes a new control system
without pole sensor for detecting phase angles used
in SCS's SDLN/SDPF series high-precision driver for
controlling linear motors, based on an explanation of
the operating principle of synchronous AC servomotors.
This control system reduces vibrations generated in
detection (low noise) and achieves near-zero travel distance.
In addition, the system is capable of accurately
detecting the phase of a traveling machine by judging
the phase angle according to the acceleration. The control
system is especially effective for linear motors that
are used in precision mechanical systems with low frictions
achieved with air bearings. |
|
|
|
