Real-Time Marker Localization Learning for GelStereo Tactile Sensing

Visuotactile sensing technology is becoming more popular in tactile sensing, but the effectiveness of the existing marker detection localization methods remains to be further explored. Instead of contour-based blob detection, this paper presents a learning-based marker localization network for GelStereo visuotactile sensing called Marknet. Specifically, the Marknet presents a grid regression architecture to incorporate the distribution of the GelStereo markers. Furthermore, a marker rationality evaluator (MRE) is modelled to screen suitable prediction results. The experimental results show that the Marknet combined with MRE achieves 93.90% precision for irregular markers in contact areas, which outperforms the traditional contour-based blob detection method by a large margin of 42.32%. Meanwhile, the proposed learning-based marker localization method can achieve better real-time performance beyond the blob detection interface provided by the OpenCV library through GPU acceleration, which we believe will lead to considerable perceptual sensitivity gains in various robotic manipulation tasks

RISE-based adaptive control of electro-hydraulic servo system with uncertain compensation

Electro-hydraulic servo system (EHSS) plays an important role in many industrial and military applications. However, its high-performance tracking control is still a challenging mission due to its nonlinear system dynamics and model uncertainties. In this paper, a novel adaptive robust integral method of the sign of the error (ARISE) with extended state observer (ESO) is proposed. Firstly, the nonlinear mathematical model of typical EHSS with modeling uncurtains and uncertain nonlinear is established. Then, ESO is used to estimate the state and lumped disturbance, of which the unknown parameter estimations can be updated by the novel adaptive law. Results shows that the novel controller achieves better tracking performance in maximum tracking error, average tracking error and standard deviation of the tracking error

A New Characterization Parameter of out-of-plane Constraint for C(T) Specimens

As the resistance of structures against the crack-tip plastic deformation, constraints has attracted much attention in the research of material fracture behaviour. In order to increase the accuracy of structural integrity assessment, many characterization parameters of in-plane and out-of-plane constraints have been considered and proposed in the last few decades. Three-dimensional finite element analyses have been conducted for five C(T)50 specimens with different out-of-plane constraint. The distributions of four constraint parameters (σ22/σ0, Tz, h and Dp) along crack fronts were calculated. To characterize the out-of-plane constraint, the capability of constraint parameters such as σ22/σ0, Tz, h and Dp were analyzed and compared. Results show that, compared with the three constraint parameters (σ22/σ0, Tz and h) based on crack-tip stress fields, the parameter Dp based on crack-tip equivalent plastic strain is more sensitive to out-of-plane constraint, and may effectively characterize the out-of-plane constraint

In-Hand Object Localization Using GelStereo Visuotactile Sensing

Cui S, Li Q, Cai Y, Wang S. In-Hand Object Localization Using GelStereo Visuotactile Sensing. Presented at the IROS2021- Dexterous manipulation workshop, Prague.In-hand object localization has always been a critical but difficult aspect of dexterous robotic manipulation. We attempt to address this issue in this paper through the use of point cloud registration techniques. Specifically, the grasping pose is estimated by registering the high-resolution 3D contact point cloud sensed by a novel GelStereo tactile sensor with the object template point cloud. Extensive qualitative and quantita- tive analyses of in-hand localization and insertion experiments of small parts are performed on our robot platform. The experimental results verify the accuracy and robustness of the proposed in-hand object localization pipeline

Modeling and Optimization of Laser Cladding Fixation Process for Optical Fiber Sensors in Harsh Environments

In order to overcome the shortcomings of the poor shear resistance of the bare optical fiber whose coating layer falls off due to harsh conditions, such as on aero-engines and the marine environment, the coaxial powder feeding laser cladding method (CPFLCM) is proposed to connect the optical fiber sensor and the substrate. The concentration field model of the powder flow is established in sections, the effective number model of particles and the corresponding laser attenuation rate are obtained. Through simulation, the influence of relevant parameters of laser cladding on the temperature field was analyzed, and the accurate parameters of laser cladding were optimized. Finally, the temperature rise trajectory of the substrate temperature field was verified by using the fiber grating temperature sensor. Through experiments, the quality of the molten pool and the optical transmission loss of the optical fiber sensor were analyzed, and the consistency of the simulation optimization parameters was verified. Through this paper, it can be concluded that the proposed CPFLCM can realize the effective connection of the optical fiber sensor to the substrate. It is of great significance in the application of optical fiber sensors in harsh environments of oceans and aerospace

Evolving Roles for Targeting CTLA-4 in Cancer Immunotherapy

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is a membrane glycoprotein expressed by activated effector T cells (Teffs) and participates in the repression of T cell proliferation, cell cycle progression and cytokine production. Currently, antibodies targeting CTLA-4, ipilimumab and tremelimumab are widely used as a therapeutic approach in a variety of human malignancies. However, their detailed mechanism remains unclear. Therefore, in this review, we focused specifically on recent findings concerning the role of CTLA-4 in immune response and also discussed clinical studies of targeting CTLA-4, alone or in combination with other therapies for the treatment of cancers. CTLA-4 blockade is used as a therapeutic approach for the treatment of cancer through competing with CD28-positive costimulation for binding to their shared B7 ligands or exhibiting direct inhibitory effect on signaling molecules in the cytoplasmic tail. At present, antibodies for targeting CTLA-4 or in combination with other therapies significantly reinforced the anti-tumor effect and improved the prognosis of malignant disease. In addition, severe adverse events of targeting CTLA-4 therapy could be a challenge for the development of this therapeutic strategy. This review may provide some new insights for clinical studies of targeting CTLA-4