Henri Poincarè Group of Complex Systems, Physics Faculty, University of Havana, Havana, Cuba.
PLoS One. 2013 Aug 5;8(8):e67838. doi: 10.1371/journal.pone.0067838. Print 2013.
While "vibrational noise" induced by rotating components of machinery is a common problem constantly faced by engineers, the controlled conversion of translational into rotational motion or vice-versa is a desirable goal in many scenarios ranging from internal combustion engines to ultrasonic motors. In this work, we describe the underlying physics after isolating a single degree of freedom, focusing on devices that convert a vibration along the vertical axis into a rotation around this axis. A typical Vibrot (as we label these devices) consists of a rigid body with three or more cantilevered elastic legs attached to its bottom at an angle. We show that these legs are capable of transforming vibration into rotation by a "ratchet effect", which is caused by the anisotropic stick-slip-flight motion of the leg tips against the ground. Drawing an analogy with the Froude number used to classify the locomotion dynamics of legged animals, we discuss the walking regime of these robots. We are able to control the rotation frequency of the Vibrot by manipulating the shaking amplitude, frequency or waveform. Furthermore, we have been able to excite Vibrots with acoustic waves, which allows speculating about the possibility of reducing the size of the devices so they can perform tasks into the human body, excited by ultrasound waves from the outside.
虽然机器旋转部件引起的“振动噪声”是工程师经常面临的一个常见问题，但在许多场景中，将平移运动转换为旋转运动或反之亦然是一个理想的目标，这些场景包括内燃机到超声波电机等。在这项工作中，我们描述了隔离一个自由度后的基础物理学，重点研究了将垂直方向上的振动转换为围绕该轴的旋转的装置。一个典型的 Vibrot（我们将这些设备标记为 Vibrot）由一个刚性体组成，其底部以一定角度连接有三个或更多的悬臂弹性腿。我们表明，这些腿通过“棘轮效应”将振动转换为旋转，这是由腿尖与地面之间的各向异性的粘滑-飞行运动引起的。通过类比用于分类腿部动物的运动动力学的弗劳德数，我们讨论了这些机器人的行走模式。我们可以通过操纵振动的幅度、频率或波形来控制 Vibrot 的旋转频率。此外，我们已经能够用声波激励 Vibrot，这使得我们可以推测通过外部超声波激励来减少设备的尺寸，以便它们可以在人体内部执行任务。
