Hall Rick S, Desmoulin Geoffrey T, Milner Theodore E
Department of Kinesiology and Physical Education, McGill University, Montreal, QC, Canada H2W 1S4.
J Biomech. 2008 Dec 5;41(16):3492-5. doi: 10.1016/j.jbiomech.2008.09.031. Epub 2008 Nov 18.
Miniature sensors that could measure forces applied by the fingers and hand without interfering with manual dexterity or range of motion would have considerable practical value in ergonomics and rehabilitation. In this study, techniques have been developed to use inexpensive pressure-sensing resistors (FSRs) to accurately measure compression force. The FSRs are converted from pressure-sensing to force-sensing devices. The effects of nonlinear response properties and dependence on loading history are compensated by signal conditioning and calibration. A fourth-order polynomial relating the applied force to the current voltage output and a linearly weighted sum of prior outputs corrects for sensor hysteresis and drift. It was found that prolonged (>20h) shear force loading caused sensor gain to change by approximately 100%. Shear loading also had the effect of eliminating shear force effects on sensor output, albeit only in the direction of shear loading. By applying prolonged shear loading in two orthogonal directions, the sensors were converted into pure compression sensors. Such preloading of the sensor is, therefore, required prior to calibration. The error in compression force after prolonged shear loading and calibration was consistently <5% from 0 to 30N and <10% from 30 to 40N. This novel method of calibrating FSRs for measuring compression force provides an inexpensive tool for biomedical and industrial design applications where measurements of finger and hand force are needed.
能够测量手指和手部施加的力而不干扰手动灵活性或运动范围的微型传感器在人体工程学和康复领域将具有相当大的实用价值。在本研究中，已开发出利用廉价的压敏电阻（FSR）来精确测量压缩力的技术。FSR从压力传感装置转变为力传感装置。通过信号调理和校准来补偿非线性响应特性以及对加载历史的依赖性的影响。一个将施加的力与当前电压输出相关联的四阶多项式以及先前输出的线性加权和可校正传感器的滞后和漂移。研究发现，长时间（>20小时）的剪切力加载会使传感器增益变化约100%。剪切加载还具有消除剪切力对传感器输出影响的作用，尽管仅在剪切加载方向上。通过在两个正交方向上施加长时间的剪切加载，传感器被转换为纯压缩传感器。因此，在进行校准之前需要对传感器进行这种预加载。经过长时间剪切加载和校准后，压缩力的误差在0至30N范围内始终<5%，在30至40N范围内<10%。这种用于校准FSR以测量压缩力的新方法为需要测量手指和手部力量的生物医学和工业设计应用提供了一种廉价工具。
