Customizable Recorder of Animal Kinesis (CRoAK): A Multi-axis Instrumented Enclosure for Measuring Animal Movements

We designed a novel device, called CRoAK, to quantify the movements of small animals in response to acoustic stimulation. We built our setup in a mini acoustically insulated chamber in which we suspended a small acoustically transparent animal enclosure. On the bottom of the enclosure, we attached an Arduino controlled 9 Degrees of Freedom (9DoF) Inertial Measurement Unit (IMU) that combines three different 3-axis sensors, an accelerometer (linear acceleration), a gyroscope (angular velocity), and a magnetometer (direction of the magnetic field). In our implementation of CRoAK, we relied solely on the gyroscope to quantify the motion of the enclosure in response to the movements made in response to a stimulus. We did not use the accelerometer in this implementation because we anchored the suspended enclosure to minimize oscillations in the system after perturbation by an animal’s movement. This means that, by design, we eliminated the possibility of linear translation such that movements would result in angular displacement of the enclosure that could be captured by the gyroscope. Other users may find the accelerometer more useful in customized implementations of CRoAK more suitable to their purpose. We also did not use the magnetometer in our single-speaker setup, but it could be used in multi-speaker implementations of CRoAK to measure perturbations of the local magnetic field that occur when different speakers are being driven, for example, to coordinate movements with sounds broadcast from different directions. Here we provide CAD figures of the device along with the Arduino code that was used to collect data from the sensor.

本研究设计了一款名为CRoAK的新型装置，用于量化小型动物受声学刺激时的运动行为。我们的实验装置搭建于小型声学隔音舱内，舱内悬挂有一款声学通透的小型动物饲养舱。在饲养舱底部，我们搭载了一款由Arduino控制的九自由度（9 Degrees of Freedom, 9DoF）惯性测量单元（Inertial Measurement Unit, IMU），该单元集成了三类三轴传感器：加速度计（accelerometer，用于采集线性加速度）、陀螺仪（gyroscope，用于采集角速度）以及磁强计（magnetometer，用于检测磁场方向）。在本研究的CRoAK实现方案中，我们仅使用陀螺仪来量化饲养舱在外界刺激引发动物运动时的舱体运动状态。本次实现中未使用加速度计，原因在于我们对悬挂的饲养舱进行了固定处理，以最大程度抑制动物运动引发扰动后系统产生的振荡。这意味着，从设计之初我们就排除了系统产生线性平移的可能，因此动物的运动只会引发饲养舱的角位移，而这一变化可通过陀螺仪进行采集。其他使用者在针对自身需求定制CRoAK装置时，或许会发现加速度计的实用性更强。在本次单扬声器的实验设置中，我们同样未使用磁强计；但在多扬声器的CRoAK实现方案中，磁强计可用于检测不同扬声器驱动时产生的本地磁场扰动，例如用于实现不同方向播出的声音与动物运动的关联校准。本次研究附带了该装置的计算机辅助设计（Computer-Aided Design, CAD）图纸，以及用于采集传感器数据的Arduino代码。