User guide

Chapter 3. Basic Operation Setup 105
Target Zone Mode (Move Completion Criteria)
Under default operation (Target Zone Mode
not enabled), the 6000 product's move
completion criteria is simply derived from
the move trajectory. The 6000 product
considers the current preset move to be
complete when the commanded trajectory has
reached the desired target position; after that,
subsequent commands/moves can be
executed for that same axis. Consequently,
the next move or external operation can
begin before the actual position has settled
to the commanded position (see diagram).
Position
Time
Velocity
Commanded
Actual
Actual
Commanded
Time
When the Target Zone Mode
is
not enabled, the move is
considered to be complete
and subsequent moves can
now be executed.
Move is actually
Completed
NOTE
Stepper products may use
the Target Zone mode
ONLY if operating in
encoder step mode (ENC1)
with encoder feedback.
To prevent premature command execution before the actual position settles into the
commanded position, use the Target Zone Mode. In this mode, enabled with the STRGTE
command, the move cannot be considered complete until the actual position and actual
velocity are within the target zone (that is, within the distance zone defined by STRGTD and
less than or equal to the velocity defined by STRGTV). If the load does not settle into the
target zone before the timeout period set with the STRGTT command, the 6000 product detects
a timeout error (see illustration below).
If the timeout error occurs, you can prevent subsequent command/move execution only if you
enable the ERROR command to continually check for this error condition, and when it occurs
to branch to a programmed response you can define in the ERRORP program. (Refer to the
Error Handling section, page 30, for error program examples.)
As an example, setting the distance zone to ±5 counts (STRGTD5), the velocity zone to ≤0.5
revs/sec (STRGTVØ.5), and the timeout period to 1/2 second (STRGTT5ØØ), a move with a
distance of 8,000 counts (D8ØØØ) must end up between position 7,995 and 8,005 and settle
down to ≤0.5 rps within 500 ms (1/2 second) after the commanded profile is complete.
Damping is critical To ensure that a move settles within the distance zone, it must be damped to the point that it
will not move out of the zone in an oscillatory manner. This helps ensure the actual velocity
falls within the target velocity zone set with the STRGTV command (see illustration below).
Actual
STRGTD
(Distance Zone)
STRGTV
(Velocity Zone)
STRGTT
(Timeout Period)
PositionVelocity
Commanded
Failed Move Completion
Timeout Occurs,
Error Bit Set
Commanded
Actual
Successful Move Completion
Time
Time
STRGTT
(Timeout Period)
PositionVelocity
Commanded
Actual
Commanded
Time
Time
STRGTD
(Distance Zone)
STRGTV
(Velocity Zone)
Actual
Move
Completed
Move
Completed
TSTLT
(Actual Settling Time)
Checking the
Settling Time
Checking the Actual Settling Time: Using the TSTLT command, you can display the actual
time it took the last move to settle into the target zone (that is, within the distance zone
defined by STRGTD and less than or equal to the velocity defined by STRGTV). The reported
value represents milliseconds. This command is usable whether or not the Target
Zone Settling Mode is enabled with the STRGTE command.