Auxiliary Axis For Rensselaer'S Geotechnical Centrifuge Center In-Flight Robot - Design Considerations

Rensselaer's Geotechnical Centrifuge Center is a resource for conducting research into the behavior of soils, earthen structures and other materials under high g-force conditions. The 3m radius centrifuge can accelerate a roughly I m x I m x I m payload up to as much as 200 g's. Under such loading, properly prepared soil samples accurately simulate deep soil conditions at I g. The system also includes an In-flight Robot that provides the capability to perform experiments while the centrifuge is in operations, as well as a 2-D shaker and associated 2-D Laminar Box that permit earthquake simulations while in flight. However prior to the implementation of the Auxiliary Axis, pilings were limited to a maximum usable length of approximately 15cm. The objective of Auxiliary Axis is to provide the capability to handle long pilings (up to 35cm) in situations where both the 2-D Shaker and 2-D Laminar Box are used. The Aux Axis is attached to the exterior of the in-flight robot when needed, and removed when not. The Aux Axis is designed to perform in a 50 g's environment which holds some unique engineering concerns. It is designed so that installation and removal is as simple as possible, and can typically be completed in about 30 minutes. The Aux Axis is powered by the existing robot Z axis motor and belt drive system. Consequently, both the Z axis and the Aux Axis move simultaneously when the Aux Axis is installed. The Aux Axis is geared approximately 8.42 times higher than the Z axis so that it moves much further than the Z axis during operation. This permits the pilings; which are attached to the Aux Axis, to be fully inserted into the soil sample before the Z axis has moved far enough to interfere with the top of the 2-D Laminar Box.