Broekman André, Willem Jacobsz Schalk, Louw Hendrik, Kearsley Elsabé, Gaspar Tiago, Da Silva Burke Talia Simone
Department of Civil Engineering, University of Pretoria, Pretoria, South Africa.
HardwareX. 2020 Oct 17;8:e00151. doi: 10.1016/j.ohx.2020.e00151. eCollection 2020 Oct.
Geotechnical centrifuges are valuable instruments for physical modelling of complex geotechnical problems in a controlled laboratory setting. In comparison to full-scale testing, scaled models are cost effective to construct and instrument and, when tested in a geotechnical centrifuge at increased centrifugal accelerations, are capable of replicating full-scale stress-strain soil behaviour. Centrifuge modellers require specialised hardware and instruments capable of functioning under high accelerations. Such hardware is costly, nearly always purpose built, and often rely on commercial, closed-source data acquisition systems, hardware and control systems. This paper demonstrates a novel and versatile, low cost, open source logger and control system that works in parallel alongside existing centrifuge hardware. This solution, termed Fly-by-Pi, was developed using the Raspberry Pi microcomputer. The system provides closed-loop control of linear actuators with the ability to operate in either cyclic, monotonic, or static load- or displacement-control. The control mechanism can be reprogrammed according to experimental requirements, even during flight in the centrifuge. Three independent experiments are described which included the Fly-by-Pi controller as a key component in their operation. Based on the experience gained during these experiments, the authors encourage wide-spread adoption of open-sourced hardware solutions in extreme testing environments.
土工离心机是在可控实验室环境中对复杂岩土工程问题进行物理模拟的宝贵仪器。与全尺寸测试相比，缩尺模型的构建和仪器安装成本效益高，并且在岩土离心机中以增加的离心加速度进行测试时，能够复制全尺寸的应力应变土行为。离心机建模人员需要能够在高加速度下运行的专用硬件和仪器。这种硬件成本高昂，几乎总是定制的，并且通常依赖于商业的、闭源的数据采集系统、硬件和控制系统。本文展示了一种新颖且通用的低成本开源记录器和控制系统，它可以与现有的离心机硬件并行工作。这个名为“Fly-by-Pi”的解决方案是使用树莓派微型计算机开发的。该系统提供对线性执行器的闭环控制，能够在循环、单调或静态载荷或位移控制下运行。控制机制可以根据实验要求重新编程，即使在离心机运行期间也是如此。文中描述了三个独立实验，这些实验在运行中将“Fly-by-Pi”控制器作为关键组件。基于这些实验获得的经验，作者鼓励在极端测试环境中广泛采用开源硬件解决方案。
