Rockwell Automation Publication 2080-UM002K-EN-E - March 2019 101
Motion Control Chapter 7
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
Homing Function Block
on page 122.
Soft Limits
Soft limits refer to data values that are managed by the motion controller. Unlike
hardware limits which 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.
Soft Limits are activated only when the corresponding axis is homed. Users can
enable or disable soft limits, and configure an upper and lower limit setting
through the Connected Components Workbench software.
When a soft limit is enabled, the axis comes to a stop when the limit is detected
during motion. The motion is stopped using emergency stop parameters.
If both hard and soft limits are configured as enabled, for two limits in the same
direction (upper or lower), the limits should be configured such that the soft
limit is triggered before the hard limit.
PTO Pulse Limits
This limit parameter is not configurable by the user and is the physical limitation
of the embedded PTO. The limits are set at 0x7FFF0000 and -0x7FFF0000
pulses, for upper and lower limits, respectively.
PTO pulse limits are checked by the controller unconditionally — that is, the
checking is always ON.
Soft Limits Checking on the Function Blocks
Function Block Limits Checking
MC_MoveAbsolute The target position will be checked against the soft limits before motion
starts.
MC_MoveRelative
MC_MoveVelocity The soft limits will be checked dynamically during motion.
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