Parker Hannifin S.p.A S.B.C. Division
SLVDN User’s Manual
Page 153 of 181
13.1.8.
Functional description
By choosing a method of homing by writing a value to
homing method
will clearly establish
the homing signal (positive limit switch, negative limit switch, home switch)
the direction of actuation and where appropriate
the position of the index pulse(*).
The home position and the zero position are offset by the
home offset
, see the definition of
home offset
for how this offset is used.
Various homing positions are illustrated in the following diagrams. An encircled number
indicates the code for selection of this homing position. The direction of movement is also
indicated. Further homing methods may be defined by the manufacturer using the negative
values of
homing method
.
There are four sources of homing signal available, these are the negative and positive limit
switches, the home switch and the index pulse from an encoder.
In the diagrams of homing sequences shown below, the encoder count increases as the axle's
position moves to the right, in other words the left is the minimum position and the right is the
maximum position.
For the operation of positioning drives, an exact knowledge of the absolute position is
normally required. Since for cost reasons, drives often do not have an absolute encoder, a
homing operation is necessary. There are several, application-specific methods. The
homing
method
is used for selection.
The exact sequence of the homing operation is clearly described by the method. In some
circumstances, a device has several methods to choose from, using the
homing method
.
(*) with resolver feedback, it’s necessary set the object 0x6098 with negative sign. In this
case the homing function is stopped immediately after the home sensor, and the actual
position becomes the home position.
13.1.8.1.
Homing methods
The following sub-sections describe the details of how each of the homing modes shall
function.
13.1.8.1.1.
Method 1: Homing on the negative limit switch and index
pulse
Using this method the initial direction of movement is leftward if the negative limit switch is
inactive (here shown as low). The home position is at the first index pulse to the right of the
position where the negative limit switch becomes inactive.