DigitAx User Guide
Issue code: dgxu4
10-9
When reading the total value from the buffer, Pr75
must be read first. When Pr75 is accessed, the
value in Pr76 is frozen until it has also been
accessed.
Make the following settings for digital pulse
position control:
1. Set b14 at 0.
2. Set b15 at 1.
3. Set b16 at 0.
4. Set b17 at 0.
Fixed Increment Reference control
Fixed Increment Reference control allows a certain
number of pulses to be added or subtracted from
the buffer while the Drive is running. This allows a
phase shift to be introduced between the master
and any slave Drives. The function is controlled
using the digital inputs on terminals B4 and B5 (see
the table below). The increment value is set in
Pr20. The buffer is updated every 5ms.
B4 B5 Value of Pr20
+24V 0V or open
circuit
Added to count
0V or open
circuit
+24V Subtracted from
count
0V or open
circuit
0V or open
circuit
No effect on count
+24V +24V No effect on count
Make the following settings for fixed increment
position control:
1. Set b14 at 0.
2. Set b15 at 1.
3. Set b16 at 1.
4. Set b17 at 0.
Position Hold at zero speed
When the value held in the buffer is zero, the Drive
holds the motor at zero speed but any position
reference is lost. The buffer is cleared to under
either of the following conditions:
• When the Drive is enabled
• When a Stop signal is received
When the motor is required to be held at zero speed
for a period of time before the final position is
reached (eg. when the machine door is opened)
without clearing the value in the buffer (and hence
losing the position reference), the limit-switch
function should be used by setting b16 at 1. This
holds the motor at zero speed by inhibiting rotation
in either direction.
Spindle orientation
This function allows the motor to be stopped at a pre-
defined position when under analog or digital speed
reference control. The orientation position for the
shaft is set in Pr27. The range of Pr27 is 0 to 2047,
giving a resolution of 0.176°. The orientation
command can be given in either of two ways as
follows:
Set b53 and b18 at 1 (Stop, orientate and hold
with ramps) using serial communications.
Set b53 at 1, and apply a Stop signal to terminal
B6.
When the Stop signal is received, the motor
decelerates to the orientation speed set in Pr54. The
motor continues rotating in the same direction until
the orientation position is reached.
Parameter b41 (Shaft orientation) is set at 1 when
the following applies:
Pr53 ≥ Pr27 – Pr83
During orientation, the value of Pr37 is used for the
position loop gain.
Methods of stopping
Auto-stop
If the DC bus voltage falls below the value set in
Pr5, b18 is automatically set at 1 and the motor is
stopped without deceleration ramp (stopping under
current limit) (see Normal stop-and-hold below). The
motor remains stopped even if the
DC bus voltage
recovers immediately. To re-start the motor, use
serial communications to set b18 at 0.
Normal stop-and-hold
When a Stop signal is applied to terminal B6, or b18
is set at 1, the Drive brings the motor to standstill,
but the Drive does not become disabled. The
motor can be stopped without deceleration ramp
(stopping under current limit), or ramps can be
included to make the stop smoother. This keeps the
motor under torque control, and consequently holds
the motor at the stopped position. The motor
stops at a random position unless some external
control loop is used.
Ramps are selected by setting b22 at 1. When a
Stop signal is received, the Drive decelerates the
motor at the rate given in Pr11 or Pr12. Selection
of ramps for stop-and-hold mode is independent of
whether ramps are selected to act on the speed
reference.
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