精密柔索传动是一种通过主、从动轮之间有适当预紧的传动介质实现的摩擦挠性传动方式，具有轻质、高效、简洁等特点，在轻量化光电侦察吊舱等系统中得到了广泛的应用。张力是精密柔索传动系统的一项关键设计参数，可以有效调控传动特性。但是，由于空间结构尺寸所限，现有的张力测量方法难以进行精确测量。本文提出了一种改进型三点弯曲张力测量方法。建立了张力对传动特性的灵敏度关系，推导了基于抗弯刚度的张力测量修正模型。为了验证修正模型的有效性，将精密柔索传动单元下两种不同规格的传动柔索应用在三种不同跨距下，进行张力测试。实验结果表明，修正模型下的张力偏差均值大幅度减小，张力偏差能够缩小到5 N以内，满足柔索传动系统的张力测量精度要求。

The precision cable drive is a flexible frictional transmission method in which power is transmitted from drive capstans to a driven pulley by a properly preloaded transmission medium. Owing to its many advantages, such as lightweight, high efficiency, and simplicity, it has been widely used in the field of lightweight electro-optical tracking. Cable tension is an important design parameter that can effectively regulate the transmission characteristics of the precision cable drive. However, accurate measurements of cable tension in highly confined spaces are difficult to make with the existing tension meter method. Therefore, a revised three-point-bending method was proposed in this paper. Parametric sensitivity was investigated to evaluate the relationship between the transmission characteristics of the drive and cable tension. Furthermore, a revised model for measuring cable tension that included bending rigidity was established. To validate the proposed theoretical models, a series of experiments were performed with two types of cables and three kinds of measuring spans. The test results reveal that the tension deviation could can be reduced to 5 N by using the proposed method, which is considerably lower than that obtained with the tension meter method reported in the literature. The revised method can meet the requirements of cable tension measurement in a precision cable drive system.