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Space robots play a significant role in on‐orbit servicing (OOS) missions, such as inspecting, capturing, refueling, and repairing satellites, assembling and maintaining large space infrastructure, and removing orbital debris. Over the past four decades, many space robot engineering applications and technology verifications for OOS have been accomplished. This article comprehensively reviews the advances by representative space robotic programs on space shuttles, outside/inside the International Space Station and the China Space Station, as well as on satellites, and the development trends of space robots are summarized. In addition, the primary key technologies and challenges are explored, including the following: 1) visual perception for noncooperative targets; 2) motion planning and control with a free‐floating base and flexibility; 3) multifunctional end‐effectors; 4) ground teleoperation with long time delays; and 5) high‐fidelity ground verification. Finally, the prospects for space robot future research are presented. This review highlights advances in representative space robotic programs on space shuttles, outside/inside the International Space Station and the China Space Station, and on satellites, and their development trends are summarized. The leading critical technologies and challenges in using space robots are investigated herein. Subsequently, it presents the prospects for future space robot research.

In recent years, with the rapid development of science and technology, agricultural robots have gradually begun to replace humans, to complete various agricultural operations, changing traditional agricultural production methods. Not only is the labor input reduced, but also the production efficiency can be improved, which invariably contributes to the development of smart agriculture. This paper reviews the core technologies used for agricultural robots in non-structural environments. In addition, we review the technological progress of drive systems, control strategies, end-effectors, robotic arms, environmental perception, and other related systems. This research shows that in a non-structured agricultural environment, using cameras and light detection and ranging (LiDAR), as well as ultrasonic and satellite navigation equipment, and by integrating sensing, transmission, control, and operation, different types of actuators can be innovatively designed and developed to drive the advance of agricultural robots, to meet the delicate and complex requirements of agricultural products as operational objects, such that better productivity and standardization of agriculture can be achieved. In summary, agricultural production is developing toward a data-driven, standardized, and unmanned approach, with smart agriculture supported by actuator-driven-based agricultural robots. This paper concludes with a summary of the main existing technologies and challenges in the development of actuators for applications in agricultural robots, and the outlook regarding the primary development directions of agricultural robots in the near future.

In recent years, the agricultural sector has turned to robotic automation to deal with the growing demand for food. Harvesting fruits and vegetables is the most labor-intensive and time-consuming among the main agricultural tasks. However, seasonal labor shortage of experienced workers results in low efficiency of harvesting, food losses, and quality deterioration. Therefore, research efforts focus on the automation of manual harvesting operations. Robotic manipulation of delicate products in unstructured environments is challenging. The development of suitable end effectors that meet manipulation requirements is necessary. To that end, this work reviews the state-of-the-art robotic end effectors for harvesting applications. Detachment methods, types of end effectors, and additional sensors are discussed. Performance measures are included to evaluate technologies and determine optimal end effectors for specific crops. Challenges and potential future trends of end effectors in agricultural robotic systems are reported. Research has shown that contact-grasping grippers for fruit holding are the most common type of end effectors. Furthermore, most research is concerned with tomato, apple, and sweet pepper harvesting applications. This work can be used as a guide for up-to-date technology for the selection of suitable end effectors for harvesting robots.

In the process of aero-engine blade polishing, parameter uncertainties and unmodeled disturbances in the pneumatic end-effector cause fluctuation of the polishing force, affecting the quality of blade processing. To solve the problems mentioned above, a polishing force adaptive controller based on dual extended state observer is proposed. A novel mathematical model of the pneumatic end-effector is established based on the flow characteristics near the zero position of the proportional valve, and a matched disturbance factor is introduced. The controller proposed in this paper contains parameter adaptive law and dual extended state observer. The former aims to compensate for the parameter uncertainties, and the latter aims to compensate for the matched and unmatched disturbances, respectively. The experimental analysis including aero-engine blade polishing constant contact stress control is applied. Simulation and experimental studies show that the controller proposed in this paper can effectively compensate for the influence of parameter uncertainties and unmodeled disturbances on the fluctuation of the polishing force. The fluctuation of the polishing force is 0.41 N, and the quality of the surface finish of aero-engine blades is improved.

Fruit and vegetable harvesting robots have been widely studied and developed in recent years. However, the usage of existing end-effectors remains a challenge because they cannot be extended to other fruits and vegetables. This study proposes a novel end-effector that can harvest a variety of fruits and vegetables without any additional and complex control. For efficient harvesting, an end-effector in which the cutting, suction and transporting modules were integrated was designed and the performance of each module was verified through lab and field experiments, ensuring a reduction in harvesting time and improved productivity, the goal of harvest automation. Field experiments were conducted for a total of five cases (− 30°, − 15°, 0°, 15° and 30°) for each entry angle in three places. A total of 160 cluster tomatoes were harvested, with a total success rate of 80.6% and a total harvesting time of 15.5 s. The success rates for each entry angle were 75.0%, 71.9%, 93.8%, 81.2% and 81.2% and the harvesting times were 20.2, 16.0, 13.5, 13.7 and 14.1 s, respectively. The results also open the possibility of designing a robust harvesting system for the proposed end-effector. This study also provides directions for future discussion through which harvesting robots and the utilization of robust harvesting systems can be improved.

In this paper, we propose a method for selecting end-effectors based on depth images for a robot that performs picking tasks using multiple end-effectors. The proposed method evaluates the graspability of each end-effector in a scene by convolving a hand model, represented as a two-dimensional binary structure, with the depth image of the target scene. A key feature of the method is that it requires no pre-training and does not rely on object or environmental models, operating solely with simple models of the end-effectors. In picking experiments involving eight types of electronic components commonly used in factory automation, the proposed method effectively alternated between suction and two-finger grippers. Compared to other training-free end-effector selection methods and approaches using a single end-effector, the proposed method demonstrated an improvement of over 14% in grasp success rate compared to the second-best method.

Agricultural robots have become increasingly crucial in precise agriculture. This paper reviews recent developments in end-effectors applied in the robotic harvesting of fruits and vegetables. The control and harvest function of the end-effector is the focus. Different structures are categorized based on their properties. Advantages and limitations in each category are introduced. For the collection method, the hard-grab method is very popularly for low difficulties and the soft one can protect the fruits adequately and can harvest different fruits of similar size; double-finger type is used widely with the advantages of low cost, while the multi-finger type has the much higher stability. The collection method is divided into the cutting and twisting methods. The former is applied for low difficulties but may spread diseases among plants; therefore, thermal cutting, namely using high temperature to separate stem and crop, and the twisting method is used. Overall, different types of end-effectors show various advantages. With consideration of the target crop physical properties, a proper decision for the harvester can be made.

During the picking process of the apple harvesting robot, the attitude of the end effector holding the apple and the movement method of separating the apple directly affect the success rate of picking. In order to improve the stability of the picking process, reduce the gripping force, and avoid apple dislodgement and damage, this work studies the new apple-picking pattern of the flexible three-fingered end-effector based on the analysis of the existing apple-picking pattern. First, two new three-finger grasping postures for wrapping the apple horizontally and vertically on the inside of the fingers are proposed, and a new method of separating the stem with a circular-pull-down motion of the end-effector picking the apple is designed. Then, the pressure on the apple under different picking patterns was analyzed, and a branch–stem–apple simulation model was established. Combining the constraint conditions such as the angle between the apple stem and the vertical direction, the movement speed, the root impulse, and so on, the optimal angle of apple circular movement and the force required to realize the movement are obtained through dynamic simulation experiments. Finally, the experiments of apple picking patterns were carried out with the flexible three-fingered end-effector. The experiment shows that the best angle for apple picking is 15°~20° using the circular-pull-down movement separation method. In terms of average grasping force peaks and pressures, the combination of the vertical holding posture of the inner finger and the circular-pull-down movement separation method is the best picking pattern. In this pattern, the average peak exerts force on the inner side of a single finger is about 8.52 N, and the pressure is about 20.9 KPa.

Achieving safe robotic manipulation at the microscopic scale usually requires sophisticated equipment, imposing accessibility difficulty in practice. Inspired by tiny bubbles in nature, a new paradigm is proposed for achieving multifunctional manipulation and sensing using microbubbles for biological application in aqueous environments at low cost. Without demanding the expensive cost of fabrication devices, bubbles with various sizes are easy to generate in situ, which is enabled by bubble‐endowed interface interactions. It is demonstrated that bubbles acting as micro end‐effectors rapidly and adaptively realize dexterous manipulation of microobjects such as biological organisms and droplets. They can function as microgrippers to grasp microobjects based on interface interaction‐induced adhesion and act as soft micromanipulators to safely manipulate fragile objects. Moreover, the bubble micro end‐effector can sense and perceive the designated objects for contact measurement of microforces or surface textures at a microscopic scale via the shape changes of their ultrasoft structures. The reported method successfully integrates grasping, manipulation, and measurement functions in liquid using a single microbubble of less than 1 mm3 volume. These nondestructive functionalities showcase promising prospects for bubble‐based micro end‐effectors in biological manipulation and sensing applications. Inspired by bubbles, this article proposes a low‐cost method for multifunctional manipulation and sensing using microbubbles in aqueous environments. Bubbles are easily generated in situ, enabling the safe and adaptive handling of microobjects and sensing of microforces and surface textures. This method integrates grasping, manipulation, and measurement within a bubble (<1 mm3), showing promise for biological applications.

Robot technology is considered one of the most promising technologies to achieve intelligent production, with picking robots being the most common type. Picking robots are highly integrated mechatronic systems, which autonomously complete tasks including picking, carrying, and sorting. The application of picking robots enhances the efficiency of production across various environments. In this paper, a classification-design-optimization-application integrated framework of picking robots is addressed, contributing to theoretical research and application of picking robots. Classification of picking robot is established and analyzed considering the differences of overall form and end-effector to guide the development of research strategies and approaches of picking robot. Design of picking robot is described from different aspects of the target, structure, monitoring, and control design. Additionally, the commonly used optimization methods for picking robots, including structural parameters, kinematics and dynamics, and energy consumption, are discussed. Finally, the application of picking robots under different environments is expounded, and the challenges and prospects of picking robots are highlighted. This study could present theoretical support and application measures for picking robot study and technology development.