User guide

90 6000 Series Programmer's Guide
End-of-Travel Limits
The 6000 controller can respond to both hardware and software end-of-travel limits. The purpose
of end-of-travel limits is to prevent the motor's load from traveling past defined limits.
HARDWARE LIMITS
6000 controllers are shipped from the factory with the hardware end-of-travel limits enabled,
but not connected. Therefore, motion will not be allowed until you do one of the following:
• Install limit switches or jumper the end-of-travel limit terminals to the GND terminal
( refer to your product's Installation Guide for wiring instructions ).
• Disable the limits with the LH command (recommended only if the load is not coupled).
• Reverse the active level of the limits with the LHLVL command.
Related Commands:
LH........... Hard limit enable
LHAD...... Hard limit decel
LHADA... Hard limit decel (s)
LHLVL... Limit switch polarity
LS........... Soft limit enable
LSAD...... Soft limit decel
LSADA... Soft limit decel (s)
LSNEG... Soft limit (negative)
LSPOS... Soft limit (positive)
TLIM...... Hard limit status
TASF...... Bits 15-18 indicate if
................ hard or soft limit was
................ encountered
TERF...... Bit 2: hard limit hit
................ Bit 3: soft limit hit
................ (must enable ERROR
................ checking bits 2 &3)
Once a hardware or software limit is reached, the 6000 controller will decelerate that axis at the
rate specified with the LHAD and LSAD commands, respectively. Servos also use the LHADA
and LSADA commands for S-curve deceleration.
Typically, software and hardware limits are positioned in such a way that when the software
limit is reached the motor/load will start to decelerate toward the hardware limit. This will
allow for a much smoother stop at the hardware limit. Software limits can be used regardless
of incremental or absolute positioning.
The default active level of the hardware limits is active-low, requiring normally-closed limit
switches. If you wish to change the active level to active-high, use the LHLVL1 command.
Software limits are defined by the LSPOS and LSNEG commands. The LSPOS command
establishes the limit in the positive direction, LSNEG for the negative direction limit. These
limits are enabled with the LS command and are scaled by the SCLD command. The software
limits are referenced from a position of absolute zero. Both software limits may be defined
with positive values (e.g., axis #2 in the example below) or negative values. Care must be
taken when performing incremental moves because the software limits are always defined in
absolute terms. They must be large enough to accommodate the moves, or a new zero
reference position must be defined (using the PSET command) before each move.
NOTES
• To ensure proper motion when using soft end-of-travel limits, be sure to set the LSPOS
value to an absolute value greater than the LSNEG value.
• Stepper products: If your system is moving heavy loads or operating at high velocities,
you may need to decrease the LHAD command value (deceleration rate) to prevent the
motor from stalling (Zeta drives and ZETA610n may compensate without reducing decel).
• If you reverse the commanded direction polarity (CMDDIR1), you should swap the hardware
end-of-travel switch connections to maintain a positive correlation with the commanded
direction.
Example In this example, the hardware and software limits are enabled on axes #1 and #2, and disabled
on axes #3 and #4. The distance scaling command (SCLD) is used to define software limit
locations in revolutions from the absolute zero position (assumes a 4000 step/rev resolution).
Deceleration rates are specified for both software and hardware limits. If a limit is encountered,
the motors will decelerate to a stop.
@ERES4000 ; Set encoder resolution to 4000 steps/rev (all axes)
SCALE1 ; Enable scaling
@SCLD4000 ; Allow user to program soft limit distance in revs (all axes)
@SCLA4000 ; Program soft limit accel/decel in revs/sec/sec (all axes)
LH3,3,0,0 ; Enable limits 1 and 2, disable limits 3 and 4
LHAD10,10 ; Set hard limit deceleration
LSAD5,10 ; Set soft limit deceleration
LSNEG0,2 ; Set neg. direction soft limit (axis 1: 0 revs; axis2: 2 revs)
LSPOS10,20 ; Establish pos. soft limit (axis 1: 10 revs; axis 1: 20 revs)
LS3,3,0,0 ; Enable soft limits 1 and 2, disable limits 3 and 4