LRS Micro-g LaCoste FG5, Руководство пользователя, Страница: 27 / 149

Design: Components and Function
2
2.5.2.DROPPER CONTROLLER
The dropper controller uses three modes to operate the dropping chamber.
These modes are OSC, AUTO, and MANUAL. The operator also controls the
status of these modes and the dropper triggering with the RESET and INIT
switches and the trigger source (INT/EXT) switch. See Chapter 4 for a detailed
discussion of the modes and switches.
The dropper controller can direct the motor in the Dropping Chamber to lift the
cart and test mass to a specified height, to move the cart at a specified velocity,
and to track the test mass during free-fall.
The motor drives the cart/test mass assembly by turning a pulley and stainless
steel drive belt which is attached to the cart. The motor also turns an optical
shaft encoder that provides accurate information to the dropper controller on the
position and velocity of the pulley.
Information on the relative position of the test mass to the cart during free-fall is
provided by a sphere detector system. An LED and a linear detector are
mounted on opposite sides of the cart, and an optical glass sphere is mounted on
the test mass. The sphere focuses a beam of light from the LED onto the linear
detector, indicating the precise location of the center of the sphere relative to the
cart. The dropper controller uses this information to determine whether to
maintain, increase, or decrease current to the motor to achieve the appropriate
relative position of the cart and the test mass. This feedback system is a
conventional analog servo system.
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