Scanlab RTC6 PCIe Board - Synchronization by Encoder Signals; Intended Use

RTC6 boards
Doc. Rev. 1.0.21 en-US
9 Programming Peripheral Interfaces
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9.3.3 Synchronization by Encoder
Signals
Intended Use
When processing moving workpieces, the laser scan
processes need to be adapted to the current
workpiece position.
To incorporate the current workpiece position, the
RTC6 can evaluate signals of up to two user-supplied
incremental encoders. Though incremental encoders
do not register the current workpiece position, they
register the motion of the transport system (conveyor
belt, rotating plate, etc.)
(1)
: For each transport
motion, they provide signals (depending on the
direction of movement) to the RTC6 which can result
in incrementing or decrementing of its two internal
encoder counters
(2)
. The states of the RTC6’s encoder
counters thereby correspond directly to the position
of the workpiece
(3)
.
If workpieces are always processed at a constant
speed and an encoder is therefore not mandatory,
then the encoder signals can also be simulated by
simulate_encoder, so that the encoder counters are
incremented with a constant counting rate of 1 MHz.
The current counts of both encoder counters can be
queried by the control command get_encoder.
Alternatively, they can be stored in a buffer by the
list command store_encoder and then retrieved
from there by the control command read_encoder.
In addition, the RTC6 automatically evaluates the
current counts if execution of the laser scan processes
is controlled as follows:
• For Processing-on-the-fly-applications (see
Chapter 8.6 ”Processing-on-the-fly”, page 242),
the coordinate values of all Vector Commands
and “Arc” Commands are transformed in
accordance with the current encoder counts.
• By the list command wait_for_encoder_mode,
further execution of a list can be postponed until
the selected encoder counter has overstepped or
understepped a predefined value.
• With 2D movements,
wait_for_encoder_in_range waits until the
encoder values are within a given rectangle.
• For External Starts, a track delay can be defined
by simulate_ext_start, set_ext_start_delay or
set_ext_start_delay_list for postponing
execution of a start relative to the triggering
input signal or corresponding command, see
Section ”External Start”, page 290.
• Encoder-speed-dependent “Automatic Laser
Control“, see Section ”Encoder-Speed-Dependent
Laser Control”, page 204, uses the current
encoder speed (counter pulses in the most recent
10 µs interval) of an encoder counter to control a
laser control signal parameter.
(1) The actual workpiece position can also be forwarded
by the McBSP interface to the RTC6 PCIe Board (see
Chapter 9.3.4 ”Synchronization and Online Positioning
by McBSP Signals”, page 300).
(2) See Notice!, page 57.
(3) The encoder counters are signed 32-bit counters. Upon
reaching the maximum (minimum) counter value,
counting continues with the minimum (maximum)
value. A counter reset only occurs if triggered by
Processing-on-the-fly-commands (see set_fly_x,
set_fly_y, set_fly_rot).
set_control_mode( Bit #9 = 1 ) can be used to
precisely synchronize the encoder reset with external
start signals.