Delta RMC151 - Manual (Page 77)

3 Controller Features
2 Z Trigger a Home on the Index (Z) Input. QAx Quad
3 Z And H Trigger a Home on the Index (Z) Input if the Home Input
is high.
QAx Quad
4 Z And Not
H
Trigger a Home on the Index (Z) Input if the Home Input
is low.
QAx Quad
Using the Home Input (Trigger Types 0 - 1)
The Home input is defined as follows:
Feedback Type Home Input
Quadrature (RMC70 QAx or RMC150
Quad)
Home input on the axis connector.
Quadrature (RMC70 Q1 Module) Reg input on the axis connector.
Universal I/O Module quadrature
input
Corresponding Reg n input on the module.
When the home is armed and the Home Input trigger occurs, the exact counts at the time
the trigger occurred are latched. This position is used as the physical home position. The
Actual Position at this location is set to the requested Home Position as specified by the
Arm Home (50) command. The Command Position and Target Position will be offset by
the difference between the new and old Actual Positions.
On quadrature axes, the counts are latched within 40μs (150μs for UI/O module, with
Filter Reg Input off) of the trigger and are therefore typically very accurate (depending on
the encoder resolution, of course). To obtain an accurate trigger, the direction and speed
should be the same each time the axis is homed. This is because proximity switches have
delays and hysteresis.
Using the Z input (Index Pulse) (Trigger Types 2 - 4)
The Z input is available on the RMC150 Quad module.
Homing with the Index (Z) pulse is the most accurate method of homing. When the home
is armed and the Index (Z) pulse of the encoder is encountered (with or without the
Home Input, depending on the trigger type), the Home is latched. When this occurs, the
Actual Position at the location of the Z pulse is set to the Requested Position as
specified by the Arm Home (50) command. The Command Position and Target Position
will be offset by the difference between the new and old Actual Positions.
In order to achieve the most accurate homing with the Index (Z) pulse, you must issue
the Learn Z Alignment (54) command when setting up your axis. This command sets the
Index (Z) Home Location parameter. Once this parameter is set correctly, you can home
with the Index (Z) pulse in any direction, at any speed, and the home will always occur at
the exact same position on the encoder. See the Learn Z Alignment (54) topic for details.
Linear Positioner Homing Tips
When using a quadrature encoder on a linear positioner, the axis must be homed to
retain absolute positions. This is easiest if the proximity switch controlling the Home input
is placed at one end of the travel (for example, in the retracted position); this will be the
home position. This is a typical procedure for homing a linear positioner:
1. Arm the homing by issuing an Arm Home (50) command with a Trigger Type of H
Falling.
2. If the axis is at an unknown position:
Retract until the Home Input status bit is ON. This can be done with a Move Velocity
command. Then, extend until the Home Input status bit is OFF. When the Home
Input status bit turns off, the axis will home and the Home Latched status bit will be
set.
If the axis is already retracted:
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