Quantitative analysis of cleavage-stage embryos is a critical step for embryo evaluation in in vitro fertilization (IVF) treatment. Deep learning-based instance segmentation methods have emerged as a promising solution. However, existing methods, typically designed for opaque instances in nature scenes, face challenges when applied to segmenting overlapping cells in cleavage-stage embryos. The semi-transparency of the cells in cleavage-stage embryos leads to vague boundaries and complex overlaps between cells, making it difficult for existing models to segment these cells without merging or missing cells. In this work, we propose a novel instance segmentation network for segmenting overlapping, semi-transparent cleavage-stage embryo cells. Specifically, the network introduces two specialized branches that learn complementary representations: an overlap branch for addressing inter-instance overlaps and a boundary branch for dealing with intra-instance shapes. Then, an attention-based feature fusion module is designed to integrate learned overlap and boundary features to enhance the instance representation for the segmentation branch. Finally, an overlap-aware post-processing module leverages the outputs from the overlap and boundary branches to adaptively adjust suppression thresholds, ensuring the preservation of distinct yet highly overlapping cells. Experiments on two cleavage-stage embryo datasets demonstrate that our method outperformed state-of-the-art methods in both segmentation accuracy and recall, highlighting its potential for quantitative embryo evaluation in clinical IVF.

Robotic steering of magnetic guidewires has shown great potential in accelerating endovascular interventions, enhancing the success rate of time-sensitive surgeries such as stroke treatment. Incomplete state feedback of the guidewire from 2D perspective images and unknown interactions with the surrounding vessel wall raise challenges in modeling and steering control. These two factors, however, are commonly overlooked by existing works. In this paper, 2D perspective images of the guidewire, which comply with prevalent medical imaging modalities, are used as the only feedback. A model-based external force observer is proposed that allows the guidewire to perceive the unknown interactions, and a compliance controller is subsequently designed to handle the external force while steering the guidewire. Experiments conducted in a human-sized phantom demonstrate how the compliance controller preserves stability and safety by adapting to the estimated external force.

This paper presents a novel biomimetic morphing quadrotor design inspired by the morphology of an eagle claw during prey capture. The arms of the quadrotor are capable of vertical folding to enable dynamic grasping, mimicking the transition of the eagle claw from an open to a closed state. This transition is achieved through the rotation of a central servomotor and the associated movement of 20 links. Thanks to the closed-loop multi-link structure of the frame, the propellers of the quadrotor remain in a fixed orientation when the arms are folded, allowing for system stabilization at any arm rotation angle. The geometric property of the whole frame is analyzed to determine the relationships and constraints of the links, which is important in experimental vehicle fabrication. To handle possible physical property changes and external disturbances during grasping, the adaptive sliding mode controllers are applied. To deal with objects of unknown size in grasping tasks, an admittance filter is proposed for adaptive morphology. While in flight, our proposed morphing quadrotor is able to rapidly or continuously transition to any configuration within its range smoothly. Experimental results show the ability of the quadrotor to dynamically grasp various unknown objects at 0.4m/s without additional tools, as well as its versatility in traversal of narrow spaces and perching.

Contact-based aerial interaction control in unknown environments is a challenging issue. To solve this problem, this paper presents an image-based impedance control scheme for an aerial manipulator. Unlike points and image moments, the line features considered in this paper cannot uniquely determine the pose of the onboard camera. Therefore, a nonlinear observer is proposed to online provide supplementary 3D information of the system. After that, a hierarchical tracking controller, which is equipped with an image-space impedance filter, is designed to implement a trajectory tracking task with tunable compliance, while at the same time achieving a subtask that aims to determine the final pose of the aerial manipulator. By planning task-space trajectories, desired interaction behavior can be specified without relying on the global position of the system. Furthermore, the effectiveness criterion of the observer is derived, and the stability of the system is proven. Several experiments, including a push-and-slide task, robustness analysis, and a comparison with the state of the art have been conducted to demonstrate the feasibility of the method. Note to Practitioners—This article presents a method for controlling an aerial manipulator to interact with unknown environments without measuring the global position of both the environment and the aerial manipulator. Furthermore, unlike the existing methods, the proposed visual servoing method is based on line features, which are generally more robust than point features. Moreover, it would be intuitive for users to specify the approaching path and the interaction behavior of the aerial manipulator by just planning the image feature trajectories and the desired distance between the aerial manipulator and the environment. This distance is online estimated using the visual feedback of a monocular camera, instead of relying on any costly 3D-vision sensors or lidars, making it an economical solution for aerial manipulation in field environments.

In this paper, an image-based impedance control strategy for force tracking of an unmanned aerial manipulator (UAM) is presented. Firstly, image features with nice decoupling characteristics are designed and the relationship between the camera motion and the image features is derived. Then, a two-stage strategy is proposed to achieve force tracking of the UAM on a planar object in an arbitrary pose. The first stage drives the end-effector perpendicular to the object’s planer surface by pure visual servoing. To achieve force tracking under the visual guidance, an adaptive visual impedance control method which adjusts the target stiffness according to the force tracking error and the visual feature error is proposed in the second stage. The closed-loop system is proved asymptotically stable by means of Lyapunov analysis. Further, the stability in free flight phase of the stage two is also analyzed and ensured. Finally, experiments were carried out including a whiteboard cleaning task in different poses. The experimental results illustrate the validity and effectiveness of the proposed approach. Note to Practitioners—This work is motivated by the contact force tracking problem of an unmanned aerial manipulator (UAM) without the position measurement. In recent years, impedance control is widely used in force tracking problems. However, position measurement is needed both for the robot and the object in most studies. To generate desired force under visual guidance, image-based visual servoing is combined with a novel impedance controller with variable stiffness. The idea is intuitive. For a human in contact with a wall, the contact force is controlled by adjusting his arm stiffness, which means the stiffness is adapted to the difference between the desired and actual contact force. Furthermore, the stiffness is also adapted to the visual tracking error, removing the assumption that no tracking error is in the inner loop of the impedance controller in the previous works. The proposed strategy is a promising solution for real applications and is validated by a board cleaning experiment in this paper.

Physical human–robot interaction in the field of aerial vehicles has received more research attention in recent years. In this article, a visual impedance control strategy for human–aerial robot cooperative transportation with a tethered vehicle is presented. Without a positioning system, the aerial vehicle is controlled to follow the human partner by using cable force and visual features of the object as feedback. Furthermore, being aware of human motion is important to improve efficiency and smoothness of the cooperation. Without measuring velocities of the aerial vehicle and the human, we propose to directly estimate the relative velocity of them by a vision-based velocity observer. This estimated velocity is then integrated into a visual impedance scheme. The stability of the system is rigorously proved by Lyapunov analysis and passivity analysis. Indoor experiments where a human participant transports a long bar with a tethered aerial vehicle are conducted. Results of experiments under different human velocities and intentions demonstrate the effectiveness and reliability of the proposed method.

Inter-signal timing skew gives rise to reduced timing margins at the receiver and limits the data rate of parallel links. This paper proposes a new inter-signal timing skew compensation technique for parallel links with voltage-mode incremental signaling. The proposed technique employs an early/late block to detect the rising and falling edges of adjacent pulses generated at the output of comparators due to inter-signal timing skews, and subsequently to allocate the optimal sampling point of the samplers to maximize timing margins. Two delay-locked loops (DLLs) are employed to place the sampling clock to the optimal sampling position. The skew compensation range is quantified with reference of the delay range of the DLLs. The effectiveness of the proposed deskewing method is validated using a 1 Gbyte/s parallel link implemented in UMC-0.13 mum 1.2 V CMOS technology with three microstrip channels on a FR4 substrate.