Southern African Large Telescope

Prime Focus Imaging Spectrograph

Generic Mechanism


Jeffrey W Percival

Modification Record
Version Date Comments
1.0 27-Feb-2003
1.1 27-Feb-2003 Add in-line content

Our second motion control effort was more ambitious.

A combined view

Combined View

This shows the "generic mechanism" we built to verify the behavior of chosen components, explore fabrication plans and techniques, and to test our mechanism control designs in software. We built a mechanism section and control section. We also built a LabVIEW control module.

The mechanism section.

Mechanism Section

This shows the mechanism section of the Generic Mechanism.

At the top is a worm-driven linear stage (like our slimask elevator). It has an incremental rotary encoder on the left end, and a cable transducer (like a yo-yo) on the right. The cable is pulled out as the stage moves to the left, and provides an analog signal.

The bearing has end-of-travel switches (a Hall-effect vane switch and a Reed switch), and a home indicator used when initializing the encoder.

At the bottom is a 2-port Festo pneumatic actuator, like we will use with the slitmask fetch/stow operation.

We were surprised by the size of the wire bundle, considering that this plate supports only two actuators!

The control section.

Control Section

This shows the control section of the generic mechanism. Clockwise from upper left:

A LabVIEW User Interface