Development of a scalable actuator control system for use in a geotechnical centrifuge

Abstract

Abstract. The paper details the characteristics of a single axis actuator control system, capable of conducting tests via both displacement and load control method. The scalable actuator control system or SACS, was developed at the University of Dundee to match the increasing complexity involved in motion control and load sequences during model tests in the centrifuge. The module has a single PID controller driving a single axis with provision to future expansion, a waveform generator and sequence controller; which are operated within a single intuitive user interface, LABVIEW. The interface allows a seamless switching between automated and manual control, resulting in simultaneous automated control of the actuator in load and/or displacement control. Keywords. Motion control, PID controller, automation, servo motor, screw jack, centrifuge, model tests, displacement control. Introduction In recent times, as physical modelling techniques have evolved, the demand for a more complex, sophisticated, user configurable and flexible actuator control system has arisen. Geotechnical centrifuge modelling for example, demands an advanced, remotely controlled and highly configurable motion system for performing real time experiments in a safe way. Unfortunately, the development of the actuator control system with special attention to geotechnical centrifuge modelling has been rather limited. At University of Dundee a manually controlled actuator system was historically used on the beam centrifuge facility to study various geotechnical problems such as behavior of skirted foundations under combined loading along vertical and horizontal directions [1]. A similar study has been reported [2], where an improved automated actuator control system was used. However, there is an urgent need to develop an actuator control system which is robust, efficient and capable of undertaking monotonic and cyclic heavy duty load testing in a high acceleration field with utmost efficiency and minimal cost. In this context, the development and constant improvement of software applications are required for easy implementation of control algorithms and creation of user friendly interfaces with virtual instruments (VI) [3]. Thus, in this paper, the National Instrument SoftMotion module and the LabVIEW graphical development