Operation & Software Manual
114
Direct Drives & Systems
Chapter C: System functions
ETEL Doc. - Operation & Software Manual # DSC2P 903 / Ver. F / 3/6/05
12.9 Homing
After phasing (refer to
), a
homing
has to be carried out, moving the motor until it reaches a fix
reference mark
(also called
index)
. The motor movement can highly vary during a homing according to the
type of encoder used. Some display several reference marks at regular distance from each other to know the
motor absolute position (multi-reference mark encoder) and others display only one (mono-ref. mark encoder).
Finally some encoders have no ref. marks, and homing has to be done against a fix
mechanical end stop
or
against a
limit switch
or
home switch
. The
IND
.<axis> command starts the homing (it can be used only if the
power is on and K61=1). With EnDat 2.1 encoder, there is no homing because it gives an absolute position.
The homing procedure (not available with EnDat 2.1 encoder) determines the motor absolute position, and
secondly finds a constant phase shift adjustment value for each system powered (therefore, the motor's force
will be the same after each homing).
• Determination of the motor absolute position:
For
multi-reference marks encoders
, the motor moves and knows its absolute position as soon as it finds
two successive reference marks (they are coded). It means that the position origin, also called
’0 machine’
, is
set. If during a next homing the motor uses two different successive reference marks, the ’0 machine’ remains
set in the same position.
Remark:
With a multi-reference marks encoder linear motor, the ’0 machine’ can appear outside the total
motor stroke.
Immediately after having set the ’0 machine’, the controller adds up the value contained in parameter K45 (with
EnDat 2.1 encoder, parameter K45 is added to the absolute position). This value is given in [upi]. This
procedure places the ’0 machine’ in any position set by the user according to the application. Move the ’0
machine’ to the position of the motor is possible with the
SET
command if the power is on and K61=1.
For
mono-reference mark encoders
or for a
mechanical end stop
,
home switch
or
limit switch
homing,
the motor moves until it reaches the reference mark and places there the ’0 machine’. Then the controller also
adds up the value contained in parameter K45 [upi]. The motor does not exactly stop on the reference mark.
• Calculation of the constant phase shift adjustment for each setting:
The phasing determines the motor position according to the magnets by initializing the pointers in the current
loop look-up table. This value can vary from one time to another. The
AUT
command and parameters K52 and
K53 (refer to
) enable the controller to avoid that. When the motor is
first
switched on, the AUT
command allows a precise calculation of the motor phase shift adjustment
according to the reference mark
(AUT phase shift adjustment). This phase shift adjustment value is stored in parameter K53. Then each time
the motor is switched on, the INI command calculates a phase shift adjustment value and the IND command
moves the motor until the reference mark is reached. At that moment, the INI phase shift adjustment value is
replaced (according to parameter K52) by the value contained in the parameter K53 (AUT phase shift
adjustment). Therefore the motor phase shift adjustment is always the same each time the motor is switched
on, and no longer depends on the phasing (refer to
The controller allows the user to manage two types of home switch and limit switch:
• External home/limit switch (not integrated in the encoder). In that case, the positive limit switch (reached
with a positive movement of the motor) must be connected to DIN10 (digital input), the negative limit switch
(reached with a negative movement of the motor) must be connected to DIN9 (digital input) and the home
switch must be connected to DIN2 (digital input). There can be only limit switches or only home switch or
both together.
Caution:
As there is no DIN2 on the DSCDM, it is necessary to define from which digital input the
home switch signal is coming. To do so, bits# 2 and 3 of parameter K58 must be used to
determine the origin of the home switch signal. In that case, bit# 0 and 1 of K58 must be
equal to 0.
Available on
DSC2P
DSC2V
DSCDP
DSCDL
DSCDM