238 Agilent 1200 Series Autosampler Reference Manual
8 Theory of Operation
Transport Unit Control
The transport drive electronics use current-controlled pulse-width modulation
(PWM) to drive the X, Z, θ, and gripper motors in closed-loop servo control
mode. Dedicated electronics in the SGS L6506 provide the current-control
loop. Commutation is done in FPGA logic. SGS L6201 SMT output drivers are
used for all four stepper motors. Motor encoder signals are connected to the
ASIC where the encoder quadrature decoded clock and the up/down signal
are used in the FPGA to provide instantaneous stepper motor commutation
with respect to the motor rotor position.
Wiring between the autosampler main board (ASM) and the motors and
encoders uses a flat-band cable (64 pin) and a flex board on which 10
reflection light sensors are located. Six light sensors are used for vial-tray
identification, one for gripper decoding, and three for decoding of the
initialization position.
Figure 37 Transport unit control
FPGA
Theta Drive
Gripper
Drive
X-Axis Drive
Z-Axis Drive
ASIC
Motor
Encoder
Motor
Encoder
Motor
Encoder
Motor
Encoder
Via
transport
unit flex
board
Reflection sensors on transport unit flex board:
Tray decoding (6), gripper decoding (1), initialization
sensors (3).
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