Performance Of Force Sensor Research Articles

Optical fiber membrane-based Fabry–Perot tactile force sensing platform powered by LED ambient lighting

This study introduces an optical fiber tactile force sensing platform powered by ambient LED lighting. Based on the interaction between a multimode optical fiber and a micro-polymer membrane, it is possible to excite an Extrinsic Fabry-Perot Interferometer (EFPI); this EFPI is pumped by collected incident light from the ambient LED lighting environment; here, a Fresnel lens and multimode fiber collect this light. The collector system maintains suitable light intensity even during 360° rotation. When transversal loads between 0 to 1 N are applied over the membrane, the tactile force sensor shows a wavelength shift towards shorter wavelengths; consequently, a 6.5 nm/N sensitivity and resolution of 0.15 N are obtained. Moreover, the phase analysis of the Fourier spectrum addresses intensity variations during rotation, revealing a sensitivity of 3 rad/N. The sensor offers stability, minimal hysteresis, minimal temperature modulation, and suitable time response across four sensing areas. Moreover, the statistical analysis and tactile force sensor performance ensure reliable tactile measurement with a null probability of overlap upon force application. It is crucial to note that this tactile force sensor provides a genuinely low-cost implementation due to the utilization of ambient LED lighting as the light source. This aspect represents an exciting advancement in fiber sensing technology.

A Force-Sensing System on Legs for Biomimetic Hexapod Robots Interacting with Unstructured Terrain.

The tiger beetle can maintain its stability by controlling the interaction force between its legs and an unstructured terrain while it runs. The biomimetic hexapod robot mimics a tiger beetle, and a comprehensive force sensing system combined with certain algorithms can provide force information that can help the robot understand the unstructured terrain that it interacts with. This study introduces a complicated leg force sensing system for a hexapod robot that is the same for all six legs. First, the layout and configuration of sensing system are designed according to the structure and sizes of legs. Second, the joint toque sensors, 3-DOF foot-end force sensor and force information processing module are designed, and the force sensor performance parameters are tested by simulations and experiments. Moreover, a force sensing system is implemented within the robot control architecture. Finally, the experimental evaluation of the leg force sensor system on the hexapod robot is discussed and the performance of the leg force sensor system is verified.

A Novel Cell Force Sensor for Quantification of Traction during Cell Spreading and Contact Guidance

In this work, we present a ridged, microfabricated, force sensor that can be used to investigate mechanical interactions between cells exhibiting contact guidance and the underlying cell culture substrate, and a proof-of-function evaluation of the force sensor performance. The substrates contain arrays of vertical pillars between solid ridges that were microfabricated in silicon wafers using photolithography and deep reactive ion etching. The spring constant of the pillars was measured by atomic force microscopy. For time-lapse experiments, cells were seeded on the pillared substrates and cultured in an on-stage incubator on a microscope equipped with reflected differential interference contrast optics. Endothelial cells (ECs) and fibroblasts were observed during attachment, spreading, and migration. Custom image analysis software was developed to resolve cell borders, cell alignment to the pillars and migration, displacements of individual pillars, and to quantify cell traction forces. Contact guidance classification was based on cell alignment and movement angles with respect to microfabricated ridges, as well as cell elongation. In initial investigations made with the ridged cell force sensor, we have observed contact guidance in ECs but not in fibroblast cells. A difference in maximal amplitude of mechanical forces was observed between a contact-guided and non-contact-guided, but mobile, EC. However, further experiments are required to determine the statistical significance of this observation. By chance, we observed another feature of cell behavior, namely a reversion of cell force direction. The direction of forces measured under rounded fibroblast cells changed from outwards during early cell attachment to inwards during further observation of the spreading phase. The range of forces measured under fibroblasts (up to 138 nN) was greater than that measured in EC (up to 57 nN), showing that the rigid silicon sensor is capable of resolving a large range of forces, and hence detection of differences in traction forces between cell types. These observations indicate proof-of-function of the ridged cell force sensor to induce contact guidance, and that the pillared cell force sensor constructed in rigid silicon has the necessary sensitivity to detect differences in traction force vectors between different cell phenotypes and morphologies.

Sensorless Force Control Based on H.INF. Control Theory.

This paper proposes the new force control without force sensor. The proposed system is designed by H∞ control theory. Generally, The force sensor is usually used on the force control system. However, according to both the performance of force sensor and the condition of target environment, the force sensor can not be mounted to the robot manipulator.Acceleration controller based on the disturbance observer has been studied to overcome the problem of force disturbance and nonlinear effect. However, it is difficult for this system to take account of the frequency characteristics of both sensor noise effect and disturbance rejection systematically. This paper proposes the new acceleration controller and the torque observer based on H∞ control theory. These proposed systems are systematically designed by the mixed sensitivity H∞ control design method. These systems have a simple and robust structure.