When a finger touches an ultrasonic vibrating plate, a non-sinusoidal contact force is produced. This force is called acoustic finger force. In a setup where closed-loop control is performed on the vibration amplitude, a component of the acoustic finger force can be measured at the fundamental vibration frequency of the plate. This calculation is obtained from the measurement of the variation of the controller voltage between the no-load case and when a finger is present. This calculation is made for a group of twelve participants. From these results a PCA (Principal Component Analysis) model is created. This model permits estimation of the acoustic finger force response of a participant at any vibration amplitude, based on a one or two point measurement. Finally, a linear relation between the PCA coefficients and the friction reduction is proposed. The objective of this relation would be to ultimately provide the means to create an amplitude reference calibration based on the desired friction reduction level, and thus be able to produce a standardized tactile feedback for each user, despite the biomechanical differences in finger pad properties between subjects.

中文翻译：

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面外超声振动的基本声学指力PCA模型及其与减摩的相关性

当手指接触超声波振动板时，会产生非正弦接触力。这种力称为声学手指力。在对振动幅度执行闭环控制的设置中，可以在板的基本振动频率下测量声学手指力的分量。该计算是通过测量空载情况和手指存在时控制器电压的变化而获得的。该计算是针对一组十二名参与者进行的。根据这些结果创建了 PCA（主成分分析）模型。该模型允许基于一点或两点测量来估计参与者在任何振幅下的声学手指力响应。最后，提出了 PCA 系数和摩擦减少之间的线性关系。这种关系的目的是最终提供基于所需摩擦减少水平创建幅度参考校准的方法，从而能够为每个用户产生标准化的触觉反馈，尽管受试者之间的指垫特性存在生物力学差异.