Encoder Simulation; Synchronization And Online Positioning Via Mcbsp Signals - Scanlab RTC 5 PC Interface Board Installation And Operation Manual

Encoder Increment
(360°)
Encoder
Signal 1
Encoder
Signal 2
Counter
Pulses
Timing diagram of a typical encoder signal pair and of the corre-
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sponding RTC counter pulses
Figure 60 shows the timing diagram of a typical
encoder signal pair. The second encoder signal is
usually phase-shifted by 90° relative to the first
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signal. The internal RTC encoder counter triggers at
each edge of both signals, i.e. one encoder increment
results in four counter pulses (counts). The relative
90° phase-shift of the two signals allows the RTC
board to detect not only the speed but the direction
of movement as well. Depending on the direction of
movement, the counter value is increased or
decreased.
The signals of encoder input ENCODER X will trigger
encoder counter Encoder0, the signals of encoder
input ENCODER Y will trigger encoder counter
Encoder1.
The input signals of the user-supplied encoder must
not exceed a maximum allowed frequency of 4 MHz
(i.e. 16 encoder signal edges per µs).

Encoder Simulation

The encoder simulation can be activated (and deacti-
vated) via simulate_encoder. The RTC
periodic 1 MHz clock signal. After the encoder simu-
lation is activated, the selected encoder counter (or
both counters) will be incremented at this clock rate.
Signals of an attached incremental encoder will then
be ignored.
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RTC 5 PC Interface Board
Rev. 1.9 e
9 Programming Peripheral Interfaces
9.3.4 Synchronization and Online
For processing moving workpieces with a (stationary)
scan system or a (stationary) workpiece with a
moving scan system (e.g. via a robot arm), the laser
scan processes need to be adapted to the workpiece's
current position relative to the scan system
(Processing-on-the-fly). Before processing randomly
or imprecisely positioned and oriented workpieces,
the scan system needs to be precisely aligned to the
workpiece (online positioning).
Encoder Rotation Angle
The current position of the workpiece or scan system
60
can be forwarded via the McBSP interface to the
RTC
mitted at the McBSP interface can be queried via
read_mcbsp. In addition, the RTC
evaluates the current input value if execution of the
laser scan processes is controlled as follows:
• For Processing-on-the-fly-applications (see
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• Via the list command wait_for_mcbsp, further
• Via online positioning (see
Notes
• To compensate linear motion, cartesian coordi-
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5 provides a
• The signals at the McBSP interface have no impact
Positioning via McBSP Signals
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5. The input value most recently fully trans-
page 177), the coordinate values of all vector and
arc commands are transformed in accordance
with the current input value (i.e. in accordance
with the current position of the workpiece or scan
system).
execution of a list can be postponed until the
input value (i.e. the position of the workpiece or
scan system) has reached, overstepped or under-
stepped a pre-defined value.
system will be aligned in accordance with the
current input values.
nates can be forwarded via the McBSP interface.
Compensation of rotational motion, on the other
hand, requires transmission of angle positions
(i.e. values proportional to the current angle
position – similar to synchronization via encoder
signals, see page 215). It doesn't matter if the
transmitted signal resets or simply counts further
upon overflow (angle > 360°).
on the track delay, which can be defined for
external list starts (via simulate_ext_start,
set_ext_start_delay or
set_ext_start_delay_list).
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5 automatically
page 165), the scan
216