End-effector Research Articles

Utilization of Machine Learning and Explainable Artificial Intelligence (XAI) for Fault Prediction and Diagnosis in Wafer Transfer Robot

Faults in the wafer transfer robots (WTRs) used in semiconductor manufacturing processes can significantly affect productivity. This study defines high-risk components such as bearing motors, ball screws, timing belts, robot hands, and end effectors, and generates fault data for each component based on Fluke’s law. A stacking classifier was applied for fault prediction and severity classification, and logistic regression was used to identify fault components. Additionally, to analyze the frequency bands affecting each failed component and assess the severity of faults involving two mixed components, a hybrid explainable artificial intelligence (XAI) model combining Shapley additive explanations (SHAP) and local interpretable model-agnostic explanations (LIME) was employed to inform the user about the component causing the fault. This approach demonstrated a high prediction accuracy of 95%, and its integration into real-time monitoring systems is expected to reduce maintenance costs, decrease equipment downtime, and ultimately improve productivity.

Reconfigurable cable-driven parallel mechanism design: physical constraints and control

Abstract The cable-driven parallel mechanism (CDPM) is known as an interesting application in industry to pick and place objects owing to its advantages such as large workspaces. In addition to the advantages of this mechanism, there are some challenges to improving performance by considering constraints in different components, such as the behavior of cables, shape, size of the end effector and base, and model of pulleys and actuators. Moreover, the impact of online geometry reconfiguration must be analyzed. This paper demonstrates the impact of these constraints on the performance of reconfigurable CDPM. The methodology is based on the systematic review and meta-analysis guidelines to report the results. The databases used to find the papers are extracted from Scopus and Google Scholar, using related keywords. As a result, the impact of physical constraints on system performance is discussed. A total of 90 and 37 articles are selected, respectively. After removing duplicates and unrelated papers, 88 studies that met the inclusion criteria are selected for review. Even when considering the physical constraints in modeling the mechanism, simplifications in designing a model for the reconfigurable CDPM generate errors. There is a gap in designing high-performance controllers to track desired trajectories while reconfiguring the geometry, and the satisfaction of physical constraints needs to be satisfied. In conclusion, this review presents several constraints in designing a controller to track desired trajectories and improve performance in future work. This paper presents an integrated controller architecture that includes physical constraints and predictive control.

Analysis of the air gap magnetic field in cylindrical magnetic couplings based on mathematical and finite element approach

The air gap magnetic field of a magnetic coupling plays a crucial role in the examination of its static torque and eddy current losses. Precise characterization of the air gap magnetic field is essential for ensuring the accuracy of performance assessments of the magnetic coupling. This study focuses on the cylindrical magnetic coupling as the subject of investigation, employing mathematical analysis and finite element methods to evaluate and quantify the magnetic field properties. The study establishes a mathematical model of the magnetic field of a magnetic coupling based on electromagnetic field principles and the superposition theorem. An analytical formula for the magnetic flux density distribution of the air-gap magnetic field is derived. Subsequently, a three-dimensional magnetic field finite element model is created using the finite element method to numerically calculate the air gap magnetic field and validate the analytical formula. The research also explores the periodic distribution characteristics of the magnetic field in the air gap, analyzing axial differences in magnetic flux density value and direction distribution influenced by end effects.

Design and Performance Analysis of A Linear Switched Reluctance Motor Considering End Effects

Introduction: In recent years, linear actuators have gained significant attention due to their ability to provide direct linear movement without the need for motion transformation devices. One significant challenge in the design and modeling of linear actuators is the occurrence of longitudinal end-effects. The finite length of the translator stack in linear actuators causes an unbalanced phase force, leading to discrepancies between the phases at the end and center of the actuator. Neglecting these end-effects can lead to inaccuracies in the actuator's performance and control. Methods: The objective of this study is to develop a comprehensive approach for the design, sizing, and modeling of the actuator to ensure optimal performance. An energy conversion procedure calculates the thrust force and determines the actuator's geometrical parameters. A numerical model based on the finite element method is developed to analyze the actuator's magnetic behavior and establish its characteristics. Furthermore, a thorough analysis of the end effect is conducted using two-dimensional finite element analysis. Results: To accurately capture the actuator's dynamic response and enable precise control, a mathematical model is formulated, incorporating the nonlinear behavior of inductance and incorporating the end effect factor. The proposed model demonstrates high accuracy and provides a solid foundation for the control of the linear switched reluctance actuator. Conclusion: Overall, this study contributes to the advancement of direct drive systems for industrial applications by providing a detailed design procedure and an accurate modeling approach for the linear actuator, enabling more efficient and precise control strategies.

Numerical investigation on the end effects of the flow past a finite rotating circular cylinder with two free ends

This paper studies the impact of the aspect ratio and free end shape on the end effects in the flow past a rotating circular cylinder with two flat, radiused, hemispherical, and conical ends, using the large eddy simulation method at a Reynolds number of 4.6×104. The aspect ratio in the range of 6-30 and the rotation rate in the range of 0-3, are investigated. The results show that the mean drag coefficient initially decreases slightly before rapidly increasing with the rotation rate, with a critical rotation rate that rises from 1 to 1.5 as the aspect ratio increases from 6 to 30. In contrast, the mean lift coefficient increases with both the rotation rate and the aspect ratio. When the rotation rate increases and the aspect ratio decreases, the differences between the aerodynamic coefficients of the four end shapes become more pronounced. The flat end results in the highest mean drag and lift coefficients, while the hemispherical end yields the lowest ones. In addition, when the rotation rate increases, the alternate shedding vortices shift to the opposite side. They even disappear and increase the elongated streamwise vortices. Due to the combined impacts of the rotation and end effects, large-scale tip vortices are formed, significantly altering the wake structure. The intense rotation effect results in expanding the strong influence region of the end effects and shrinking (or even removing) the weak influence region.

Corrigendum to: Current Status of Patent Research on Picking End Effector

An error appeared in the citation of Tables 2 and 3 in the manuscript titled “Current Status of Patent Research on Picking End Effector”, 2024; 18(6): e190523217074 [1]. <p> Original: <p> Li [69] developed a self-triggering apple picking and collecting machine, which consists of five parts: a selftriggering gripper, a telescopic adjustment device, a rotary turntable, a collecting device, and a floor car. The gripper part innovatively adopts a selftriggering gripper design. The invention solves the problem of low apple-picking efficiency and causes less damage to apples. <p> Wang et al. [78] invented an end effector suitable for gripping spherical fruits. The fingers of the bionic human form an effective gripping space through the upper gripping finger, the lower gripping finger, and the auxiliary gripping finger, providing reliable gripping performance. This leads to the avoidance of mechanical damage to the fruit. This device has been found to improve fruit sorting efficiency and reduce labor, but its applicability is not wide enough. <p> Corrected: <p> Li [69] developed a self-triggering apple picking and collecting machine, which consists of five parts: a selftriggering gripper, a telescopic adjustment device, a rotary turntable, a collecting device, and a floor car. The gripper part innovatively adopts a selftriggering gripper design. The invention solves the problem of low apple-picking efficiency and causes less damage to apples (Table 2). <p> Wang et al. [78] invented an end effector suitable for gripping spherical fruits. The fingers of the bionic human form an effective gripping space through the upper gripping finger, the lower gripping finger, and the auxiliary gripping finger, providing reliable gripping performance. This leads to the avoidance of mechanical damage to the fruit. This device has been found to improve fruit sorting efficiency and reduce labor, but its applicability is not wide enough (Table 3). <p> The original article can be found online at https://www.eurekaselect.com/article/131925

Design and Implementation of the Soft Robot's End-Effecter

Design and Implementation of the Soft Robot's End-Effecter

Visual localization of robotic end effector via fusion of 3D Gaussian Splatting and heuristic optimization algorithm

The visual localization of the robotic end effector holds significant importance and value in intelligent manufacturing. Regarding this issue, a pose estimation framework integrating the radiance field rendering and an improved differential evolution algorithm is proposed in this paper. Firstly, multi-view images of the object are collected by an industrial camera carried on the robotic arm. Then, a 3D Gaussian Splatting model is trained, and the observation trajectory of the virtual camera is designed based on the query image in Nerfstudio for visualization. The key frames and the corresponding pose matrices of the rendered videos along the trajectory are extracted. Subsequently, the improved differential evolution algorithm through double-layer optimization proposed in this paper is employed to conduct similarity matching between the query image and the extracted rendered images. The pose matrix corresponding to the most similar rendered image is the estimated pose of the query image. Through experiments, this paper explores the influence of the frame sampling rate on the pose estimation accuracy, and conducts comparative and ablation experiments with the commonly used methods at present. The experimental results demonstrate that the proposed method possesses good feasibility and outstanding performance.

Coupling impacts of end effects and rotation on the three-dimensional flow around a rapidly rotating circular cylinder with two flat ends

Coupling impacts of end effects and rotation on the three-dimensional flow around a rapidly rotating circular cylinder with two flat ends

A Self-Calibration Method for Robot End-Effector Using Spherical Constraints

A self-calibration method utilizing spherical constraints is proposed for calibration of robot end-effectors. The method establishes a mathematical model to account for both the geometric errors of the robot and the deformation errors of the end-effector. A nonlinear least-squares parameter identification technique based on spherical constraints is employed to achieve autonomous calibration of the end-effector. Contrasted with methodologies relying on point plane or distance constraints, this novel technique delivers superior positioning accuracy, streamlined operational procedures and enhanced efficiency. Both simulation and experimental validation confirm that the self-calibration method using spherical constraints improves the positioning accuracy of the robot end-effector from 3 mm to 0.3 mm, showing the effectiveness of the method.

Influence of polypropylene fiber length and geometric shape on the compressive strength of cemented lepidolite tailings backfill

Lepidolite ore contains abundant lithium resources; however, the extraction process generates a large number of tailings, which are environmentally hazardous solid waste. Currently, cemented fiber reinforcement and tailings filling technologies are commonly used methods for tailings treatment. The fiber length and geometric shape significantly affect the performance of fiber-reinforced cemented lepidolite tailing backfill (CLTB). However, there is limited research on the impact of these two factors on the performance of CLTB. Consequently, Polypropylene fiber-reinforced CLTB of four sizes and four fiber lengths were prepared and used for uniaxial compressive strength (UCS) tests. The max UCS of fiber-reinforced CLTB was 2.84 MPa, and the maximum increase percent was 83.7% compared with the non-fiber-reinforced CLTB. The experimental results show that when the fiber length was 12 mm the CLTB had the maximum UCS, longer fibers did not necessarily result in a higher UCS. The end effect was significant when the difference in cross-sectional area was small. The UCS of the L-40 sample was higher than that of the Y-50 sample under the same fiber length. The differences in the size effect and geometric shape were the main factors influencing their mechanical performance. When the fiber length was from 0 mm to 6 mm, the size effect was obvious, the UCS values gradually decreased with an increase in the volume ratio and cross-sectional area. However, the fiber length was the primary factor influencing the fitting curve of the UCS when the fiber length was from 12 mm to 19 mm. Additionally, the addition of fibers enhanced the integrity of CLTB. In other words, fiber-reinforced CLTB exhibited improving structural integrity. This study can provide theoretical references for the research and practical applications of fiber-reinforced fillers and size effects, as well as the treatment of lepidolite tailings, while also reflecting the CLTB performance under the action of different sizes and different fiber lengths, improving the filling efficiency, mining, and backfill safety.

Design and modeling of a novel mobile cable robot with dual-stage end effector

Design and modeling of a novel mobile cable robot with dual-stage end effector

Hysteresis compensation and decoupling control of an XYΘ-type flexure-based mechanism via inverse hysteresis-coupling hybrid modeling

Planar positioning systems are widely utilized in micro and nano applications. The challenges in modeling and control of XYΘ flexure-based mechanisms include hysteresis of the piezoelectric actuators, couplings among the input axes, and coupled linear and angular motions of the end effector. This paper presents an inverse hysteresis-coupling hybrid model to account for such hysteresis and couplings. First, a specially designed kinematic chain is adopted to transfer the pose of the end effector into the linear motions at three prismatic joints. Second, an inverse hysteresis-coupling hybrid model is developed to linearize and decouple the system via a multilayer feedforward neural network. A fractional-order PID controller is also integrated to improve the motion accuracy of the overall system. Experimental results demonstrate that the proposed method can accurately control the motion of the end effector with improved accuracy and robustness.

Design and tension distribution optimization of a 9-DOF cable-driven parallel spray-painting robot with 3 degrees of redundancy

This paper presents a 9-DOF cable-driven parallel spray-painting robot (CDPSR) with 3 ° of redundancy (DORs) for automated spraying on large, curved surfaces and proposes a feasible cable tension region (FCTR) calculation algorithm for multi-redundant robots. The end effector of the CDPSR consists of two moving platforms connected by a spherical hinge and driven by 12 cables, enabling 9 DOFs of motion (3 for translation and 6 for rotation). Given that the CDPSR has three DORs, a multi-dimensional FCTR vertex calculation algorithm is introduced. The FCTR is an adjacent, continuous, and closed convex hull in every dimension; therefore, the vertices of the FCTR can be determined sequentially and dimensionally. For DOR=3, the vertices on one face of the convex polyhedron are first determined and then extended to adjacent faces until the polyhedron is closed. An experimental prototype of the proposed robot was constructed and experiments on spray trajectory planning and FCTR calculation validation were conducted. The results of the simulations and experiments verified the motion performance of the CDPSR and the accuracy and efficiency of the FCTR calculation algorithm.

Influence of robot-guide strategies on the geometry of directed energy deposition components

Directed energy deposition (DED) for additive manufacturing applications is commonly realized by the usage of industrial robots. The DED processing end effectors are usually mounted on industrial robot systems and can, therefore, be moved and oriented in up to many degrees of freedom. However, the design of the powder nozzle and the programming of the robot can limit the movement options. For this reason, translational movements, as with conventional 3D printers, are still common today. The end effector is usually guided horizontal over the component surface although welding in position (PA) is preferred in general. It may be necessary to tilt the end effector in order to gain advantages during processing due to the constrained position. This is particularly advantageous for overhang structures and is often realized with the help of a turn-tilt positioning table in combination with an industrial robot. However, this approach is, in some cases, not possible due to geometrical constrains. To extend applications in this direction, advanced methods for slicing the components and programming the robot movements are necessary. The main aspect of this work is the development, testing, and evaluation of a multidimensional DED manufacturing approach. This is tested on a thin-walled component with defined overhang areas and compared with conventional approaches. Different strategies are assessed in terms of the geometrical match of the target geometry. Influences of strategies on the results are evaluated. It can be shown that multidimensional path planning approaches lead to a better match of the target geometry.

Stability of long uniform slopes in cohesionless soils with seepage parallel to slope surface

A method is employed in this paper for the computation of earth pressures mobilized by landslides in cohesionless soil slopes against retention systems. For calculation purposes, the water table is taken to be parallel to the slope and at a depth zw. Steady seepage is assumed to be taking place in a direction parallel to the slope. End effects are taken into account. In the upper part of the slope, the soil is considered to be in a Rankine active state of equilibrium and a Rankine passive state of equilibrium is assumed to reign in the lower part of the slope. The infinite slope concept is applied to the central part of the slope. The theory shows that the slip surfaces below the water table are curved, not straight lines.The theoretical procedure developed in the present paper was applied to the analysis of an initially unstable long slope that failed in spite of the presence of a shear pile wall made up of a row of closely spaced 1m-diameter bored piles. The retaining system was designed based on the Rankine active state of equilibrium, using a factor of safety of about 1.7. It is shown that, as the shear pile wall was located in the lower part of the slope, it was subjected to a much greater force, compatible with a Rankine passive state of equilibrium, corresponding to a factor of safety of about 0.9. As a result, the shear pile wall was doomed to fail.

Numerical and Experimental Study of a Wearable Exo-Glove for Telerehabilitation Application Using Shape Memory Alloy Actuators

Hand paralysis, caused by conditions such as spinal cord injuries, strokes, and arthritis, significantly hinders daily activities. Wearable exo-gloves and telerehabilitation offer effective hand training solutions to aid the recovery process. This study presents the development of lightweight wearable exo-gloves designed for finger telerehabilitation. The prototype uses NiTi shape memory alloy (SMA) actuators to control five fingers. Specialized end effectors target the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints, mimicking human finger tendon actions. A variable structure controller, managed through a web-based Human–Machine Interface (HMI), allows remote adjustments. Thermal behavior, dynamics, and overall performance were modeled in MATLAB Simulink, with experimental validation confirming the model’s efficacy. The phase transformation characteristics of NiTi shape memory wire were studied using the Souza–Auricchio model within COMSOL Multiphysics 6.2 software. Comparing the simulation to trial data showed an average error of 2.76°. The range of motion for the MCP, PIP, and DIP joints was 21°, 65°, and 60.3°, respectively. Additionally, a minimum torque of 0.2 Nm at each finger joint was observed, which is sufficient to overcome resistance and meet the torque requirements. Results demonstrate that integrating SMA actuators with telerehabilitation addresses the need for compact and efficient wearable devices, potentially improving patient outcomes through remote therapy.

Autonomous positioning, capturing, and grasping mechanism for robot end effectors based on the attraction domain relationship

Purpose This paper aims to solve the problem of uncertain position and attitude between unstructured terrain robot and grasped target and insufficient control accuracy in extreme environment, a grasping mechanism based on attraction domain relationship is proposed, which can realize autonomous positioning, capturing and grasping of robot under low control accuracy. Design/methodology/approach The grasping mechanism was designed, taking inspiration from fishing behavior this mechanism introduces attraction domains and flexible-elastic structures through the active and passive ends to achieve automatic positioning and capture. After the capture is completed, the grasping mechanism connects the active end and the passive end, simultaneously relying on the gravity of the target object to achieve locking and release between the robot and the target object. This paper adopts theoretical, simulation and experimental verification methods to conduct theoretical and simulation analysis on the autonomous positioning and grasping process of the mechanism, and produces grasping experimental prototypes with different positions and postures. Findings The experiment shows that the gripping mechanism designed in this paper can achieve automatic positioning capture and gripping of large deviation situations under low control accuracy, with a displacement deviation of up to 10 mm (about 1/6 diameter of the end of the mechanism) and an angle deviation of up to 3°. The scientific research task in the extremely high altitude environment has finally been successfully accomplished. Originality/value Inspired by fishing behavior, this paper proposes a positioning, capturing and grasping mechanism. The attraction area built with permanent magnets, coupled with the flexible connection, enables precise capture under low control, while the grasping mechanism can also rely on gravity to self-lock and release.

A Koopman-based residual modeling approach for the control of a soft robot arm

Soft robots are challenging to model and control due to their poorly defined kinematics and nonlinear dynamics. Recently, Koopman operator theory has been shown capable of constructing control-oriented soft robot models from data. However, building these models requires extensive data collection and they do not necessarily generalize well outside of the training observations. This paper presents a more data-efficient and generalizable approach to soft robot modeling that first identifies a physics-based Koopman model then supplements it with a data-driven residual Koopman model. The resulting combined model is linear and thus compatible with real-time model-based control techniques such as Model Predictive Control (MPC). The efficacy of the approach is demonstrated on several simulated systems and on a real soft robot arm, where it is shown to generate models that are more accurate than purely physics-based models and require less data to construct than purely data-driven models. Using a model-based controller, the soft arm is able to successfully track end effector trajectories, perform a pick-and-place task, and write on a dry-erase board, showcasing the applicability of this framework to increase the capabilities of soft robotic systems.

Motion capture and AR based programming by demonstration for industrial robots using handheld teaching device

In the industrial robots field, efficient and convenient programming methods have been a hot research topic. In recent years, immersive simulation technology has been developing rapidly in many fields, which provides new horizons for the development of industrial robots. This paper presents a HTC VIVE laser scan motion capture and Holohens augmented reality (AR) based interactive Programming by Demonstration (PbD) system for industrial robot. A portable Handheld Teaching Device (HTD) and its calibration algorithm are designed in the system. The portable HTD which is tracked by a laser motion capture system can be viewed as an AR robot end-effector to teach paths. Meanwhile, the AR robot can be simulated in real time during programing. In addition, the robot reproducing the operator’s actions at the same position in space is the focus of programming. So, Multi-system registration methods are proposed to determine the relationship between robot systems, motion capture systems and virtual robot systems. Meanwhile, a path planning algorithm is proposed to convert the captured raw path points into robot-executable code. For unskilled operators, they can easily perform complex programming using the HTD. For skilled senior workers, their skills can be quickly learned by robots using the system.