Danaher Motion
06/2005
Single-Axis Motion
4.
SINGLE-AXIS MOTION
The SERVO
STAR
MC supports three main types of motion:
Single-axis motion
Master-Slave motion
Multiple-axes motion
A motion generator controls all motion in the MC. This software device
receives commands from MC tasks and produces position and velocity
commands for the drives every servo cycle. The two main single-axis motion
commands are
JOG
and
MOVE
. The MC also provides ways to synchronize
the execution of motion commands as well as changing motion profiles on-
the-fly. In addition, the MC provides multiple modes for starting and stopping
motion.
All motion commands are subject to inherent system delays due to SERCOS
communications. One cycle time is required to transmit a command. A
second cycle time is required to receive the position feedback. Thus, the
minimum system delay is 2 SERCOS cycles. If microinterpolation is enabled
in the drive, there is an additional delay of 1 cycle time. Additional,
indeterminate, delays may result from the servo system dependent on drive
tuning and kinetics of the mechanical system.
4. 1
M
OTION
G
ENERATOR
The basis of all motion in the MC is the motion generator. When you issue a
motion command such as
JOG
or
MOVE
to an axis, a motion generator is
created in software. That motion generator controls the position and velocity
commands of the axis specified in the move command. At regular intervals
(normally 2 or 4 ms), the motion generator updates these commands. At the
end of motion, the motion generator is terminated. The figure below shows
the normal operation of a motion generator.
4.1.1. Motion
Conditions
Several conditions must be met before the MC generates motion:
The controlling task must attach to the controlled axis.
The controlled axis must be enabled.
The system and axis motion flags must be enabled.
Before a task can send motion commands to an axis,
the axis must be
attached to the task
. Attaching is also required for gearing. This prevents
other tasks from attempting to control the axis. To attach an axis, issue
ATTACH
from the controlling task:
Program
Attach A1
M-SS-005-03 Rev
E
85