SMAC
LAC-26 Technical Reference Manual
4/29/2013 27
4.3 Motion Commands
Motion Commands are those commands that involve or cause the actual movement of a servo.
Any position mode (PM) based motion will be carried out using a trapezoidal velocity profile with the
maximum velocity determined by the Set Velocity (SV) command. The acceleration and deceleration are
the same and both are determined by the Set Acceleration (SA) command.
During the execution of a Position Mode based motion,
the target position (MA or MR) and
the
maximum velocity (SV) may be changed at any time, however, changes to the acceleration (SA)
will be ignored.
If a velocity mode (VM) based motion is under way, the maximum velocity
(SV) and the
acceleration (SA) may be changed at any time. During this type of motion, the target position will
continuously be set equal to the current optimal position. If a torque mode (QM) based motion is under
way, the torque setting (SQ) may be changed at any time. During this type of motion, the target and
optimal positions will continuously be set equal to the current real position.
In either PM, VM or QM, a Stop (ST) or Abort (AB) command will cause motion for the specified
servo axis to cease. If a servo axis is in Position Mode (PM) and is commanded into Velocity Mode
(VM), the motion will continue (only with no target destination) at the current maximum
velocity set
by the Set Velocity (SV) command. If a servo axis is in PM or VM and commanded
into Torque
Mode (QM), the servo output will be reduced to zero, and the unit will be placed in QM. If a servo
axis is in VM and commanded into PM, the servo will be stopped at the current acceleration rate
and placed into the PM mode. If a servo axis is in QM and commanded into VM, it will attempt to
instantly assume the last known maximum velocity and remain in VM. If a servo axis is in QM and
commanded into PM, the output will be reduced to zero, and the servo will begin station keeping in PM.
There is another mode of operation referred to as "Electronic Gearing Mode". This mode is
a supplement to the position
based modes of operation. Electronic gearing causes the servo axis
for which it is in effect (or the
slave axis), to move proportionally to the servo axis it is tracking (or
the master axis) in conjunction with it's own motion profile. The proportion of the slave axis it set by the
Gear Ratio (GR) command.
When the EG command is issued, the relative position of the master axis (from the time
of
the EG command),
is monitored by the slave axis. This relative motion is multiplied by the value
set with the GR command
and the product of which is added to the optimal temporal
position of
the slave axis. The
result
of this is to allow the motion profile of the master
servo
axis
to
be
superimposed on the slave axis' motion profile. While the EG mode is primarily
intended
for use
with axis' that are operating in position mode (PM), it will also work with axis' that are operating
in
velocity mode (VM).
Command:
aAB
-- Abort Motion --
This command causes an emergency stop on servo axis 'a'. The servo stops abruptly but leaves
the servo control loop enabled. The target position is changed to be equal to the present position. The
command is used for stopping an undesired motion.
Related Commands: ST
Command:
aCI
-- Capture on Index --
This command
causes the position counter of servo axis 'a' to be stored in the internal
variable HREG upon receipt of an index pulse. For more information on HREG, see the Register
Commands and the listing of the internal variables.
Related Commands: FI, WI
