This paper presents a novel and high-sensitivity optical tactile sensor array based on fiber Bragg grating (FBG) to explore and localize tissue abnormalities during tissue palpation in a minimally invasive surgery. This sensor consists of five separate tactile cells with the same configuration, associated fixations, and holder parts. Each tactile cell is mainly composed of a spiral elastomer, a suspended optical fiber inscribed with an FBG element, and a contact head connecting the elastomer with a threaded connection. The two ends of the fiber were glued on the two sides of the spiral elastomer to form a tight suspension status. This configuration can effectively avoid the FBG chirping failure and achieve a higher sensitivity compared with the conventional direct FBG-pasting methods. The corresponding theoretical model has been derived, and the finite element method based simulation has been performed to facilitate the structure design and investigate both static and dynamic performances. Both static calibration experiments and dynamic loading experiments have been conducted to characterize the sensor's performance. The prototyped sensor can achieve a high resolution of up to 0.93 mN and is able to operate within a force measurement range of 0–5 N with a maximum relative error of less than 8.22%. The further surface estimation experiments and in-vitro palpation implementation on a silicone phantom embedded with simulated tumors have validated the effectiveness of the proposed design. The in-vitro experiments have demonstrated an excellent capacity to detect tumors with an embedded depth of up to 8 mm.

This paper presents a high-sensitivity triaxial catheter distal force sensor for cardiac ablation through the combined use of a force-sensitive flexure and fiber Bragg grating (FBG) sensing. A miniature force-sensitive flexure has been designed as the catheter tip, and it has an elliptical hinge with a symmetric structure for two-axial transverse force sensing and employs a pair of U-type beam slots above the hinge to sense the $z$ -direction force. Five optical fibers embedded with an FBG element each have been integrated with this flexure to detect the force-induced strain on the flexure. Each fiber is configured as a tightly suspended status with its two ends fixed, ensuring to achieve an improved sensitivity. The theoretical force–deformation relationship has been derived, and the approach for decoupling force and temperature has been presented. Finite element modeling based simulations have been performed to support the parametric design and improvement of the flexure structure. Static calibration experiments demonstrate the excellent resolution values of 2.13 and 2.52 mN for both transverse directions within –1 to 1 N, and 23.12 mN for the axial direction within 0–2 N. The linearity, repeatability, and hysteresis errors have been characterized with less than 5.3%, demonstrating the stable performance. The force and temperature can be effectively decoupled and detected with a temperature less than 60 °C. Dynamic loading experiments at different spatial angles and in vitro experiments in a silicone aortic vessel phantom have been carried out to further validate the effectiveness of the proposed design.

A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of the FBG to enhance overall sensitivity. As this mechanical configuration has a high stiffness, the proposed sensor can achieve a high resonant frequency and a wide dynamic working range. The sensing principle is presented, and the corresponding theoretical model is derived and validated. Experimental results demonstrate that the developed FBG-based strain sensor achieves an enhanced strain sensitivity of 6.2 pm/με, which is consistent with the theoretical analysis result. The strain sensitivity of the developed sensor is 5.2 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The dynamic characteristics of this sensor are investigated through the finite element method (FEM) and experimental tests. The developed sensor exhibits an excellent strain-sensitivity-enhancing property in a wide frequency range. The proposed high-sensitivity FBG-based strain sensor can be used for small-amplitude micro-strain measurement in harsh industrial environments.

The fault-induced impulse responses of localized bearing fault are usually interfered by the background noise and other harmonic components. They are strongly coupled together and are hard to be separated. It is crucial to develop a fast and reliable method to extract the impulse-based feature for online bearing fault diagnosis in the industry application. In this article, we propose a new sparse elitist group lasso denoising (SEGLD) algorithm in frequency domain to detect the incipient impulse-based fault feature, which is free of utilizing the prior knowledge. We first reveal the sparse characteristics of the bearing fault signals in frequency domain. Then, a tailored denoising model is proposed. To obtain a satisfactory analytical stationary solution, the Douglas-Rachford splitting solver is employed for the denoising model. Moreover, we explore the relationship between the best regularization parameters, the periodic information and the normalization estimated noise of the rolling bearing fault signal. A rule of adaptively selecting the best regularization parameters is demonstrated. Finally, the robustness and effectiveness of the proposed SEGLD algorithm are profoundly verified by the numerical simulation and two evaluation experiments under the conditions of early fault stage and low speed scenario. Also, it is demonstrated that the proposed approach outperforms the state-of-the-art method for extracting the weak fault feature.

A novel fiber Bragg grating (FBG) sensing-based acceleration sensor has been proposed to simultaneously decouple and measure temperature and acceleration in real-time. This design applied a diaphragm structure and utilized the axial property of a tightly suspended optical fiber, enabling improvement in its sensitivity and resonant frequency and achieve a low cross-sensitivity. The theoretical vibrational model of the sensor has been built, and its design parameters and sensing properties have been analyzed through the numerical analysis. A decoupling method has been presented with consideration of the thermal expansion of the sensor structure to realize temperature compensation. Experimental results show that the temperature sensitivity is 8.66 pm/°C within the range of 30–90 °C. The acceleration sensitivity is 20.189 pm/g with a linearity of 0.764% within the range of 5~65 m/s². The corresponding working bandwidth is 10~200 Hz and its resonant frequency is 600 Hz. This sensor possesses an excellent impact resistance for the cross direction, and the cross-axis sensitivity is below 3.31%. This implementation can avoid the FBG-pasting procedure and overcome its associated shortcomings. The performance of the proposed acceleration sensor can be easily adjusted by modifying their corresponding physical parameters to satisfy requirements from different vibration measurements.