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Chapter 4
Operation - Tutorial
4.1
Introduction
The following brief tutorial guides the user through a typical series of moves and
parameter adjustments performed using the PC based APT software. It assumes that
the unit is electrically connected as shown in Section 3.3.3. that the APT Software is
already installed - see Section 3.1. and that the stage being driven is the Thorlabs
DDS220 Direct Drive Translation stage.
Warning
The APTServer includes built in safety features which prevent the user from
performing a move before the actuators being driven have been ‘homed’. If a
custom software application, which operates outside of the APTServer, is
being used to position the actuator, then these safety features will not be
implemented. In this case, it is the responsibility of the user to home the
motors before performing any further moves. Failure to home the motors will
cause an error in positional information which could result in damage to the
unit and possible injury to personnel operating the equipment.
Caution
The maximum velocity at which the encoder can operate is approximately
400 mm/sec. Above this speed, encoder pulses may be lost and, as a
result, the position readout becomes incorrect. This renders normal
operation impossible because phase commutation of the motor is also
based on the encoder reading.
When the stage is controlled by the BBD101 controller, the maximum
velocity is limited to safe values. However, if the output is disabled (with
the controller connected and monitoring the position) and the stage is
moved manually at high speeds, it is possible to exceed this limit. If the
BBD101 controller is subsequently used again to move the stage, the
incorrect encoder reading will cause incorrect operation, often resulting
in sudden uncontrolled moves. It is therefore important not to move the
stage excessively quickly when it is moved manually.
The BBD controller has fault monitoring to detect the loss of encoder
pulses. If this fault occurs, an error message will be generated and the
controller must be powered down and re-started so that correct phasing
and commutation can be established.
If this fault occurs when the stage is being controlled via the MJC001
joystick, in the absence of a PC, the red LED on the joystick console is lit,
and all operation is suspended until the controller is shut down and
rebooted.
