Cable Force Determination Using Phase-Based Video Motion Magnification and Digital Image Correlation

The mode shape-aided method provides a simple and effective way for cable force determination, which, however, requires accurate parameter identification of the cable structure. This paper proposes a phase-based video motion magnification to process the image sequences of a cable. Digital image correlations were engaged to measure the dynamic displacement–time history, through tracking the surface characteristic features of the cable. Thereafter, a frequency–domain decomposition technique was applied to extract the natural frequency and mode shape of the cable from the displacement–time history measurements. The identified cable mode shapes, along with a tensioned pinned-pinned cable model, were used to estimate the cable force. The accuracy of the proposed methodology was subsequently verified through laboratory testing on an inclined cable model and field testing on a typical hanger cable of a real-world arch bridge. Overall, the study results indicated that the proposed methodology could expediently and cost-effectively estimate the tension forces of a cable with reasonably acceptable identification accuracy.

Overconstrained Cable-Driven Parallel Manipulators Statics Analysis based on Simplified Static Cable Model

In recent years, cable-driven parallel manipulators (CDPM) become more and more interesting topics of robot researchers due to its outstanding advantages. Unlike traditional parallel robots, CDPMs use many flexible cables in order to connect the robot fixed frame and the moving platform instead of using conventional rigid links. Since cables used in CDPM is very light compared to rigid links, its workspace can be very large. Besides, CDPMs are often enhanced load capacity by adding redundant actuators. They also help to widen the singularity-free workspace of CDPM. On the other hand, the redundant actuators produce the underdetermined system i.e. the system has non-unique solutions. Moreover, the elasticity and bendability of flexible cable caused by self-weight and external forces act on it, resulting in the kinematic problem of CDPMs are no longer related to the geometric problem. Therefore, the system of CDPM become non-linear when the deformation of cable is considered. In this study, we introduce the simplified static cable model and use it to linearize the static model of redundantly actuated CDPM. The algorithm to solve the force distribution problem is proposed in Sect. 4. The static-workspace and the performance of those are analyzed in a numerical test.

Fiber-based modeling and simulation of skeletal muscles

This paper presents a novel fiber-based muscle model for the forward dynamics of the musculoskeletal system. While bones are represented by rigid bodies, the muscles are taken into account by means of one-dimensional cables that obey the laws of continuum mechanics. In contrast to standard force elements such as the Hill-type muscle model, this approach is close to the real physiology and also avoids the issue of wobbling masses. On the other hand, the computational cost is rather low in comparison with full 3D continuum mechanics simulations. The cable model includes sliding contact between individual fibers as well as between fibers and bones. For the discretization, cubic finite elements are employed in combination with implicit time stepping. Several validation studies and the simulation of a motion scenario for the upper limb demonstrate the potential of the fiber-based approach.

A Nonlinear Cable Bracing Inerter System for Vibration Control

This study proposes a nonlinear cable model for the cable-bracing inerter system (CBIS). In a CBIS, cables are introduced to connect inerter systems and the structure for translation-to-rotation conversion. This CBIS employs an inerter element, a nonlinear cable bracing element and an additional damping element to utilize their synergy benefits. This paper aims to investigate the control effect of the nonlinear CBIS for high-rise buildings that are represented as bending-shear type models. First, a nonlinear inerter system is incorporated into a single-degree-of-freedom (SDOF) system and the mechanical model is proposed. An optimum design method is then developed for a high-rise building system equipped with a CBIS and the time-history analyses are conducted to validate the control effect of the CBIS. It is concluded that the employment of a CBIS can substantially improve the structural performance. A genetic algorithm can be used to obtain optimal parameters of a CBIS, thereby more effectively reducing the dynamic response of high-rise buildings.