Development of a four-axis robotic manipulator for centrifuge modeling at HKUST

The Geotechnical Centrifuge Facility at Hong Kong University of Science and Technology (HKUST) has recently acquired and commissioned a four-axis robotic manipulator for its 400-gt geotechnical centrifuge. The manipulator is designed to serve as a platform on which many computer-controlled activities such as excavation and loading can be performed. Central components of this robot are linear and rotary driving mechanisms, a tool changer with multiple tool adapters, and a motion controller. The driving mechanisms are to control movements in the three-dimensional space as well as rotation about the vertical axis. The maximum strokes are 875, 838 and 317 mm in the x, y, and z directions respectively, and the maximum rotation angle is 270°. The load capacities are ±5 Nm torque, and ±1000 N, ±1000 N, ±5000 N forces in the x, y, z directions, respectively. Four different types of tools can be handled using the tool changer and four tool adapters installed on the main frame. Fluid pressure and electrical signals can also be transmitted to the working tool through the tool changer and adapters. The sequence of motion is controlled through a ROBotic Control System (ROBCOS). Instructions can be input either through a teaching pendant or through a keyboard manually. The robotic manipulator has been used to correct an initially tilted building using soil extraction technique in-flight. The test set-up and some results of this test at 30 g are described in this paper.