Rockwell Automation Publication 2080-UM002L-EN-E - November 2021
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Chapter 7 Motion Control
If any one of these limits is reached on a moving axis (except on homing), an
over travel limit error will be reported and the axis will be stopped based on
configured behavior.
Sample Limits configuration in Connected Components Workbench
Hard Limits
Hard limits refer to the input signals received from physical hardware devices
such as limit switches and proximity sensors. These input signals detect the
presence of the load at the maximum upper and minimum lower extents of
allowable motion of the load or movable structure that carries the load, such as
a load tray on a transfer shuttle.
Hardware limits are mapped to discrete inputs that are associated with data
tags/variables.
When a hard limit switch is enabled, the axis comes to a stop when the limit
switch is detected during motion. If hard stop on hard limit switch is
configured as ON and the limit is detected, motion is stopped immediately
(that is, PTO pulse is stopped immediately by the hardware). Alternatively, if
hard stop on hard limit switch is configured as OFF, motion will be stopped
using Emergency Stop parameters.
When any hard limit switch is enabled, the input variable connecting to this
physical input can still be used in User Application.
When a hard limit switch is enabled, it will be used automatically for
MC_Home function block, if the switch is in the Homing direction configured
in the Connected Components Workbench software (Mode:
MC_HOME_ABS_SWITCH or MC_HOME_REF_WITH_ABS). See
Soft Limits
Soft limits refer to data values that are managed by the motion controller.
Unlike hardware limits that detect the presence of the physical load at specific
points in the allowable motion of the load, soft limits are based on the stepper
commands and the motor and load parameters.
Soft limits are displayed in user-defined units. The user can enable individual
soft limits. For non-enabled soft limits (whether upper or lower), an infinite
value is assumed.
