End-effector Research Articles

Learning to Improve Operational Efficiency from Pose Error Estimation in Robotic Pollination

Autonomous pollination robots have been widely discussed in recent years. However, the accurate estimation of flower poses in complex agricultural environments remains a challenge. To this end, this work proposes the implementation of a transformer-based architecture to learn the translational and rotational errors between the pollination robot’s end effector and the target object with the aim of enhancing robotic pollination efficiency in cross-breeding tasks. The contributions are as follows: (1) We have developed a transformer architecture model, equipped with two feedforward neural networks that directly regress the translational and rotational errors between the robot’s end effector and the pollination target. (2) Additionally, we have designed a regression loss function that is guided by the translational and rotational errors between the robot’s end effector and the pollination targets. This enables the robot arm to rapidly and accurately identify the pollination target from the current position. (3) Furthermore, we have designed a strategy to readily acquire a substantial number of training samples from eye-in-hand observation, which can be utilized as inputs for the model. Meanwhile, the translational and rotational errors identified in the end-manipulator Cartesian coordinate system are designated as loss targets simultaneously. This helps to optimize the training of the model. We conducted experiments on a realistic robotic pollination system. The results demonstrate that the proposed method outperforms the state-of-the-art method, in terms of both accuracy and efficiency.

Current Status of Patent Research on Picking End Effector

Background: Fruit and vegetable picking, as the most important part of fruit and vegetable production, is a labor-intensive industry. Fruit and vegetable picking robots can effectively improve the efficiency of picking and reduce labor requirements. As the most important part of the picking robot, the picking end-effector effectively plays a key role in improving the picking efficiency and ensuring the wholeness of the fruit. Therefore, the development trend of picking end effectors has received more and more attention. Objective: The study aimed to solve the problems of high labor consumption and low picking efficiency of manual picking; thus, the grasping method of the picking end effector has been continuously improved. Methods: This article has presented various representative patents related to the picking end effector, such as the suction end effector, multi-finger end effector, and bionic end effector. Results: Through the investigation of a large number of picking end effector patents, the current problems, such as low accuracy and large clamping damage, are summarized and analyzed. In addition, the future trends of fruit and vegetable picking end effectors are discussed. Conclusion: The optimization of the picking end effector is conducive to reducing manual labor and improving the picking rate of fruits and vegetables. More relevant patents will be invented in the future.

Memory Efficient Deep Learning-Based Grasping Point Detection of Nontrivial Objects for Robotic Bin Picking

Picking up non-trivial objects from a bin with a robotic arm is a common task of modern industrial processes. Here, an efficient data-driven method of grasping point detection, based on an attention squeeze parallel U-shaped neural network (ASP U-Net) for the bin picking task, is proposed. The method directly provides all necessary information about the feasible grasping points of objects, which are randomly or regularly arranged in a bin with side walls. Moreover, the method is able to evaluate and select the optimal grasping point among the feasible ones for two types of end effectors, i.e., a vacuum cup and a parallel gripper. The key element of the utilized ASP U-Net neural network is the transformation of a single RGB-Depth image of the bin containing nontrivial objects into a schematic grey-scale frame, where the positions and poses of the grasping points are coded into gradient geometric shapes. The experiments carried out in this study include a comprehensive set of scenes with randomly scattered, ordered, and semi-ordered objects arranged in impeccable or deformed bins. The results indicate outstanding accuracy with more than acceptable computational requirements. Additionally, the scaling possibilities of the method can offer extremely lightweight implementations, applicable, for example, to battery-powered edge-computing devices with low RAM capacity.

A tactile sensing system capable of recognizing objects based on bioinspired self-sensing soft pneumatic actuator

Tactile sensors play an important role when robots perform contact tasks, such as physical information collection, force or displacement control to avoid collision. For these manipulations, excessive contact may cause damage while poor contact cause information loss between the robotic end-effector and the objects. Inspired by skin structure and signal transmission method, this paper proposes a tactile sensing system based on the self-sensing soft pneumatic actuator (S-SPA) capable of providing tactile sensing capability for robots. Based on the adjustable height and compliance characteristics of the S-SPA, the contact process is safe and more tactile information can be collected. And to demonstrate the feasibility and advantage of this system, a robotic hand with S-SPAs could recognize different textures and stiffness of the objects by touching and pinching behaviours to collect physical information of the various objects under the positive work states of the S-SPA. The result shows the recognition accuracy of the fifteen texture plates reaches 99.4%, and the recognition accuracy of the four stiffness cuboids reaches 100%by training a KNN model. This safe and simple tactile sensing system with high recognition accuracies based on S-SPA shows great potential in robotic manipulations and is beneficial to applications in domestic and industrial fields.

Simultaneous compensation of geometric and compliance errors for robotics with consideration of variable payload effects

In order to satisfy the high accuracy requirements of robotic applications, it is necessary to consider not only the geometric errors but also the compliance errors which are caused by the self-gravity of the link and the external payloads. A general error model is developed based on the modified Denavit-Hartenberg (DH) model. For the parameters in the error model, there is a coupling between the compliance coefficients and the link parameters, making it difficult to use only the compliance coefficients to compute the compliance errors due to external payloads. As the external payload for the robot manipulator varies, the parameter identification of the model should be conducted again. In this paper, a novel algorithm using a variable payload method is proposed to first identify the compliance coefficients using different payloads and end effector position information. Second, the kinematic parameter errors and link parameters are identified with the given compliance coefficients. Then, the algorithm generates a modified trajectory using the calibrated DH tables for the precision compensation. Simulation and experimental results demonstrate that the positioning accuracy can be improved by 80 % to 90 % even under different payloads. The root mean square, mean, maximum, and standard deviation of the residual errors by using the proposed algorithm could outperform the conventional kinematic algorithm.

Day/Night Power Generator Station: A New Power Generation Approach for Lunar and Martian Space Exploration

In the not-too-distant future, humans will return to the Moon and step foot for the first time on Mars. Eventually, humanity will colonize these celestial bodies, where living and working will be commonplace. Energy is fundamental to all life. The energy that people use to sustain themselves on Earth, and in particular on these other worlds, is the integrated, safe production of electrical power, day and night. This paper proposes a radically new solution to this problem: Solar Tracking by day and a Solar Rechargeable Calcium Oxide Chemical Thermoelectric Reactor by night. Called the “Robotic End Effector for Lunar and Martian Geological Exploration of Space” (REEGES) Day/Night Power Generator Station, this form of thermoelectric power generation is mathematically modeled, simulation is performed, and a concept model design is demonstrated in this paper. The results of the presented simulation show the maximum total system output capability is 9.89 V, 6.66 A, and 65.9 W, with an operating time of up to 12 h, through a scalable design. This research provides instructions to the Space Research Community on a complete and novel development methodology for creating fully customized, configurable, safe, and reliable solar/thermoelectric day/night power generators, specifically meant for use on the Moon and Mars, using the Proportional-Integral-Derivative++ (PID++) Humanoid Motion Control Algorithm for its operation on a computationally lightweight microcontroller.

Discrete-Time Visual Servoing Control with Adaptive Image Feature Prediction Based on Manipulator Dynamics.

In this paper, a practical discrete-time control method with adaptive image feature prediction for the image-based visual servoing (IBVS) scheme is presented. In the discrete-time IBVS inner-loop/outer-loop control architecture, the time delay caused by image capture and computation is noticed. Considering the dynamic characteristics of a 6-DOF manipulator velocity input system, we propose a linear dynamic model to describe the motion of a robot end effector. Furthermore, for better estimation of image features and smoothing of the robot's velocity input, we propose an adaptive image feature prediction method that employs past image feature data and real robot velocity data to adopt the prediction parameters. The experimental results on a 6-DOF robotic arm demonstrate that the proposed method can ensure system stability and accelerate system convergence.

An automatic robot for ultrasonic partial discharge detection of gas-insulated switchgear

Purpose Gas-insulated switchgear (GIS) stands as a pivotal component in power systems, susceptible to partial discharge occurrences. Nevertheless, manual inspection proves labor-intensive, exhibits a low defect detection rate. Conventional inspection robots face limitations, unable to perform live line measurements or adapt effectively to diverse environmental conditions. This paper aims to introduce a novel solution: the GIS ultrasonic partial discharge detection robot (GBOT), designed to assume the role of substation personnel in inspection tasks. Design/methodology/approach GBOT is a mobile manipulator system divided into three subsystems: autonomous location and navigation, vision-guided and force-controlled manipulator and data detection and analysis. These subsystems collaborate, incorporating simultaneous localization and mapping, path planning, target recognition and signal processing, admittance control. This paper also introduces a path planning method designed to adapt to the substation environment. In addition, a flexible end effector is designed for full contact between the probe and the device. Findings The robot fulfills the requirements for substation GIS inspections. It can conduct efficient and low-cost path planning with narrow passages in the constructed substation map, realizes a sufficiently stable detection contact and perform high defect detection rate. Practical implications The robot mitigates the labor intensity of grid maintenance personnel, enhances inspection efficiency and safety and advances the intelligence and digitization of power equipment maintenance and monitoring. This research also provides valuable insights for the broader application of mobile manipulators in diverse fields. Originality/value The robot is a mobile manipulator system used in GIS detection, offering a viable alternative to grid personnel for equipment inspections. Comparing with the previous robotic systems, this system can work in live electrical detection, demonstrating robust environmental adaptability and superior efficiency.

High precision control of industrial robot based on flexible joint response model

For industrial robots, their repetition accuracy is high, but their absolute accuracy and trajectory accuracy are low, which limits the application of industrial robots in more scenarios. Current solutions mainly address precision issues caused by static errors through adjustments in kinematic parameters. Approaches such as dynamic feedforward control, torque computation methods, intelligent control, dual encoder control, visual servoing, etc., are employed to enhance dynamic tracking accuracy, yet they commonly suffer from insufficient precision, poor robustness, high costs, and usability challenges. In response to the difficulty in reducing dynamic errors, this paper proposes a high-precision control technique based on compensating for flexible joint responses. By compensating for deviations in flexible joint responses, the trajectory precision at the end-effector of industrial robots is improved.

Wire-arc directed energy deposition of metal using a tendon-driven soft robotic gun: prototyping and conceptual validation

ABSTRACT Most directed energy deposition (DED) implementations employ a rigid end effector to deposit material layer-by-layer, which is insufficient in cases with space constraints. To enhance the flexibility, this paper proposes a novel soft-robotic gun (SRG) based DED technology. The ideology is to replace the rigid weld gun with a tendon-driven omnidirectional-steering continuum manipulator, which a computer can numerically control. To this end, both requirements and concepts of the SRG-DED are introduced. A prototype system is designed and implemented before dedicated kinematic modelling and trajectory planning mechanisms are presented. As demonstrated by the experimental results, the developed trajectory planning algorithm improves the computational efficiency of tendon variables and enhances the consistency of trajectory tracking. The prototype system can deposit a complex path on an inclined substrate and fabricate a thin-wall component within a pipeline. The validation work confirms the feasibility and applicability of the prototype system for metal additive manufacturing applications.

Force and time-optimal trajectory planning for dual-arm unilateral cooperative grasping

This paper studies the dual-arm manipulation of an object by means of two collaborative robots. The latter hold the object through limited contact areas, thus applying unilateral contact constraints. This manipulation strategy increases versatility, since it does not require specific grippers depending on the object shape and size. However, to ensure grasping stability (i.e. no slipping of the object), a suitable internal force must be prescribed to ensure the fulfillment of the static-friction condition. In this work, the trend of the internal force is included among the inputs of a time-optimal trajectory planning, in order to find the minimal internal prestress that is able to both satisfy the static-friction condition and manipulate the object in minimal time. Admittance control is used to modulate the forces exerted by the robot end-effectors on the object. An extensive experimentation, on different 6-dimensional trajectories reaching linear and angular accelerations up to 4.5 m/s2 and 7.4 rad/s2, is presented and discussed.

Research on Electric Field Homogenization in Radial Multi-Nozzle Electrospinning.

Electrospinning is an effective method to prepare nanofibers at present. Aiming at problems such as low spinnable viscosity and the low productivity of the traditional multi-needle, a radial nozzle was proposed in this paper. In order to solve the problem of end effects in multi-nozzle electrospinning, COMSOL Multiphysics 6.0 software was used to simulate the electric field in electrospinning with seven radial nozzles. And the influence on the electric field intensity and distribution of the structural parameters of the radial nozzle, including the number, length, tip-shape, and tip-pointing direction of the vanes, were studied. Then, the electric field intensity of any point on the central axis of a radial nozzle was obtained based on the principle of electric field superposition, and then the rotation angle of the vanes corresponding to the minimum Coulomb repulsion force on the target point was deduced. At last, the method of electric field homogenization of a rotating vane arrangement was obtained. In the simulation, the strength and homogenization of the electric field were taken as the research objective, and the optimum structure parameters of the radial nozzle were obtained; the uniform theory of the electric field based on the orientation of the vanes was verified. Then, electrospinning with seven radial nozzles was performed, and it was found that each radial nozzle can produce multiple jets during electrospinning, and the prepared electrospun membranes have even thickness and high porosity. What is more, the fibers are relatively finer and more uniform.

Enhancing environmental performance: evidence from SAARC Countries

ABSTRACT This paper examines the influence of population density, economic growth, and regulatory quality on the environmental performance of five SAARC countries from 2000 to 2020. To this end, fixed and random effects models are used. Quantitative data on socio-economic and environmental characteristics reveals notable differences across countries. The results show a significant positive and negative impact of the covariates economic growth and population density, respectively, on environmental performance. While the estimated coefficient of the regulatory quality variable was positive, it was statistically insignificant. The results also suggest a significant inter-country dependency and a significant change in environmental performance across countries over time. Based on the results, several strategic approaches are proposed at both individual and multi-country settings. Furthermore, we emphasize the roles of the government, international and regional agencies, private sector, and civil society organizations. Finally, possible extensions of the present paper are discussed.

Kinematic Modelling of Humanoid Robot Based on Vectorial Approach

The present work is dedicated to the study of the inverse kinematics solution of a humanoid bipedal robot with 30 degrees of freedom using a newly approach based on vectors that generated from the geometric space of the robot. The solutions of the inverse kinematics problem for all joints articulations are carried out through a simple and linear equations. Finally, simulations of results are performed through harmonization of trajectories of end effectors of the robot's members.

Comparative Study of Mechanical Scaling Effects of Origami-Inspired Motion Generation Mechanisms with Multi-Degree Vertices

Origami exhibits the remarkable ability to transform into diverse shapes, including quadrilaterals, triangles, and more complex polygons. This unique property has inspired the integration of origami principles into engineering design, particularly in the development of foldable mechanisms. In the field of robotics, when combined with actuators, these foldable mechanisms are referred to as active origami. Origami-based mechanisms play a pivotal role as versatile end effectors or grippers, enabling them to accurately trace desired trajectories. The performance of these mechanisms heavily relies on their specific fold patterns. To shed light on their capabilities, this study focuses on five representative structures using spherical mechanisms: oriceps, Miura ori, MACIOR, and two hexagonal structures. To assess their potential, a comparative analysis is conducted, evaluating their kinematic and scaling performances. The analysis employs the “scaling factor” as a metric, which quantifies the mechanical advantage of these mechanisms. This metric aids in the selection of appropriate structures for various applications.

Experimental and numerical analysis of 3D end effects in Naval Magnetohydrodynamic propulsion motors

This study explores the impact of end electric current on the performance of a marine magnetohydrodynamic (MHD) propulsion motor or thruster using a comprehensive 3D numerical simulation. The investigation focuses on various operating parameters, such as electromagnetic and drag forces, efficiency, losses, current, and different pressure components. To validate the numerical findings, a scaled-down experimental setup is utilised. The results demonstrate that certain operating parameters of MHD motors are not affected by the three-dimensional characteristics of their channels. These parameters, including fluid velocity, can be accurately calculated using the analytical model based on the effective electric current of the motor. Conversely, other operating parameters of MHD motors are significantly influenced by the end effects in their channels. For example, the overall efficiency, which depends on the total electric current of the motor, should be calculated using a more precise simulation method.

Систематизация рабочих органов машин глубокого фрезерования

Currently, ensuring energy security is a key priority for the country. Peat resources account for one-third of the country's total energy potential. Apart from energy production, peat finds extensive use in agriculture, chemical industry, construction, and the production of construction materials. Presently, milled peat constitutes the main volume of production in the country. The technology of its extraction involves preparing areas and removing undergrowth, stumps, and wood debris during preparation of the deposit by trenching or deep milling. However, due to the imperfections of the equipment, peat contamination and loss of its quality occur. This article analyzes means for carrying out preparatory operations to condition the surface of the deposit. It discusses the designs of end effectors for deep milling machines, their cutting structures, and the specific features of the tools used, i.e. blades, cutters, mills, chains. Classification of end effectors for peat machines as well as tools for deep milling of the deposit surface is proposed. This systematization involves identifying classification features by the type of machines, impact on the wood debris, movement of the end effector, its arrangement and design, as well as by parameters and types of the end effector’s cutting structures. The article may be useful for engineers, researchers, graduate students, and organizations involved in designing and studying processes of peat deposits conditioning.

Visual Servoing and Kalman Filter Applied to Parallel Manipulator 3-RRR

This study introduces a novel methodology integrating computer vision, visual servo control, and the Kalman Filter to precisely estimate object locations for a 3-RRR planar type parallel manipulator. Through kinematic analysis and the development of a vision system using color indicators, the research enhances the ability of the manipulator to track object trajectories, especially in cases of occlusion. Employing Eye-to-Hand visual servo control, the research further refines the visual orientation of the sensor for optimal end effector and object identification. The incorporation of the Kalman Filter as a robust estimator for occluded objects underscores the predictive accuracy of the system. Results demonstrate the effectiveness of the methodology in trajectory generation and object tracking, with potential implications for improving robotic manipulators in dynamic environments. This comprehensive approach not only advances the fields of kinematic control and visual servoing but also opens new avenues for future research in complex spatial manipulations.

Analysis of size effect and its influencing factors of brittle red sandstone with different heights

We carried out uniaxial compression tests on brittle red sandstone with different heights. The test results show that the uniaxial compressive strength of rock sample increases first and then tends to be stable with the increase of the size, which is approximately stable between 75 and 81 MPa. Both elastic energy and dissipated energy increase with the increase of rock sample size. In order to further analyze the mechanism behind these phenomena, we combined advanced numerical simulation and theoretical analysis to explain these phenomena, and systematically analyzed the end face effect as one of the key factors affecting the uniaxial compression characteristics of brittle red sandstone for the first time. Small sized rock samples are very sensitive to end effect. The middle of the large sized rock samples is in a uniform compression state, and the effect of end effect is weakend. When there are rigid pads at both ends of the rock sample, there is an obvious elastic vertebral body during the loading process of the rock sample. The bearing capacity of rock samples with rigid pads is greater than that of rock samples without rigid pads, and the energy released during instantaneous failure of rock samples without rigid pads is greater than that of rock samples with rigid pads. The findings of this paper make a valuable contribution to establishing optimal study sample sizes and advancing the utilization of laboratory test mechanics parameters in engineering applications.

A fast modeling method for permanent magnet cylindrical eddy current brakes considering end effects

A fast modeling method for permanent magnet cylindrical eddy current brakes considering end effects