Serial Mechanism Research Articles

A Novel Two-Degree-of-Freedom Gimbal for Dynamic Laser Weeding: Design, Analysis, and Experimentation

Current robotic laser weeding systems mostly rely on serial mechanisms with one or two actuated axes, which can barely meet the requirements of high precision and dynamic performances. In this article, a novel laser weeding gimbal is proposed based on a two-degree-of-freedom 5-revolute rotational parallel manipulator to perform a dynamic intrarow laser weeding operation. Comprehensive analyses consisting of kinematics, workspace, singularity, and dynamics are carried out to evaluate the performance of the proposed design. Finally, experimental tests were conducted both in lab and field environments and the results are provided, in which the positioning accuracy has been evaluated as in average errors of 0.62 mm in position at the distance of 535 mm, and the dynamic weeding efficiency is around 0.72 s/weed with a dwell time of 0.64 s at the tracking speed of 0.1 m/s. The effectiveness of the proposed dynamic intrarow weeding mechanism has been evaluated in a real field trial.

Biomimetic Robotic Sea Lion Foreflippers: Design, Modeling, and Experimentation

Otariidae are excellent swimmers and the only ones among the marine mammals that use foreflippers for propulsion. Taking California sea lion as the bionic prototype, this article proposed and developed a biomimetic robotic sea lion foreflipper device (robotic flipper for short), which is composed of a pair of bionic flippers and a serial mechanism consisting of a wobbling coin mechanism and a RSSR spatial crank-rocker mechanism. The attitude and motion characteristics of the bionic flipper were obtained based on the kinematic analysis of the robotic flipper. Kinematic analysis and tank experiments show that the robotic flipper can effectively imitate the motion characteristics of the sea lion foreflipper. In addition, it can also obtain different flipper tip trajectories by adjusting the length of the connecting rod of the RSSR mechanism, and the generated thrust from the trajectory like sea lion foreflipper is larger than that from other flipper tip trajectories. A higher clapping frequency can generate a higher thrust, and the bionic flexible flipper has higher thrust and thrust efficiency than the rigid one. A larger pitch angle of the robotic flipper can result in a larger peak thrust but not always a larger average thrust. The present robotic flipper shows a better thrust performance at the pitch angle of 15°.

Religious Coping, Experiential Avoidance, Self-Compassion, and Post-Traumatic Stress by COVID-19: a Serial Mediation Study

The COVID-19 pandemic has brought consequences to mental health, with religiosity being a relevant coping factor in reducing the negative impact of the health crisis. Based on a convenience sample of Chilean adults, this study sought to explore the relationship between religious coping and post-traumatic stress due to COVID-19, hypothesizing that this relationship would be mediated by experiential avoidance and self-compassion. A non-experimental cross-sectional design was used, applying an online survey to 300 adults who lived in Chile. The results show that all variables are related and that experiential avoidance (EA) and self-compassion play a serial mediating role in the relationship between negative religious coping (NRC) and post-traumatic stress. Furthermore, the results showed that religious coping, experiential avoidance, self-compassion, and COVID-19 post-traumatic stress are significantly interrelated. Moreover, a serial mediation was found among the variables: higher experiential avoidance and lower level of self-compassion mediate the impact of COVID-19 post-traumatic stress in people with negative religious coping. At the end of the article, the implications of the results and how these variables interact in a serial mediation mechanism that sheds further light on the relationships between negative religious coping, mental health, and adverse situations such as COVID-19 are discussed.

Multi resource allocation with partial preferences

We provide efficient, fair, and non-manipulable mechanisms for the multi-type resource allocation problems (MTRAs) and multiple assignment problems where agents have partial preferences over bundles consisting of multiple divisible items. We uncover a natural reduction from multiple assignment problems to MTRAs, which preserves the properties of MTRA mechanisms. We extend the well-known random priority (RP) and probabilistic serial (PS) mechanisms to MTRAs with partial preferences as multi-type PS (MPS) and multi-type RP (MRP) and propose a new mechanism, multi-type general dictatorship (MGD), which combines the ideas of MPS and MRP. We show that for the unrestricted domain of partial order preferences, unfortunately, no mechanism satisfies both sd-efficiency and sd-envy-freeness, even as they each satisfy different weaker notions of the desirable properties of efficiency, fairness, and non-manipulability we consider. Notwithstanding this impossibility result, our main message is positive: When agents' preferences are represented by acyclic CP-nets, MRP satisfies ex-post-efficiency, sd-strategyproofness, and upper invariance, while MPS satisfies sd-efficiency, sd-envy-freeness, ordinal fairness, and upper invariance, recovering the properties of RP and PS; the MGD satisfies sd-efficiency, equal treatment of equals, and decomposability under the unrestricted domain of partial preferences. We introduce a natural domain of bundle net preferences, which generalizes previously studied domain restrictions of partial preferences for multiple assignment problems and is incomparable to the domain of acyclic CP-nets. We show that MRP and MPS satisfy all properties of the RP and PS under bundle net preferences as well.

Sustainable human resource management practices, employee resilience, and employee outcomes: Toward common good values

AbstractExtant literature has generated limited understanding of whether and how sustainable human resource management (HRM) will lead to better and more sustainable outcomes, such as enhanced employee well‐being and improved employee performance. Moving toward common good values and drawing on the job demands‐resources model, this study theorizes and tests the relationships among sustainable HRM practices, employee resilience, work engagement, and employee performance. The empirical results of a multilevel and multisource study in the Chinese context provide supporting evidence for our theoretical model. The findings demonstrate that sustainable HRM practices positively affect employee resilience, and lead to a high level of work engagement among employees. Employee resilience also has an indirect effect on employee performance through work engagement. This study, with its theoretical and practical implications, reveals a serial mediation mechanism through which sustainable HRM practices contribute to both employee well‐being and employee performance.

Principals’ Contextual Leadership on Teachers’Organizational Commitment: Teacher Empowerment and Teachers’ Workplace Well-Being as a Serial Mediator

As integration of Theory Z and Fiedler’s Contingency Theory in leadership, this study proposed a new model to reveal the underlying mechanism of psychological elements such as leadership practices, teacher empowerment, and teachers’ workplace wellbeing towards teachers’ organizational commitment (TOC). Despite the relevance of contextual leadership practices (CLP) and teachers’ emotion in school effectiveness, little is known about the implication, specifically on TOC. Data were gathered from a sample of 371 secondary school teachers selected by multi-stage random sampling method from one of the states in Malaysia and structural equation modelling was employed to assess the proposed model. Results using Structural Equation Modeling confirmed that these psychological elements directly and positively influence TOC. Additionally, teacher empowerment (TE) and teachers’ workplace wellbeing (TWW) as serial mediators significantly explained the indirect relationship sequentially. Findings provide an evidence of how a novel and comprehensive model can be practiced to enhance TOC through a serial mechanism as proposed by the integration of Theory Z and Fiedler’s Contingency Theory in leadership.

Dynamic analysis of a three-fingered deployable metamorphic robotic grasper

This paper selects a three-fingered deployable metamorphic robotic grasper as the studied object and presents a distributed dynamic modeling method for the multi-body system based on the metamorphic mechanism. Considering that the grasper contains two independent motion configurations, dynamic models of them are independently established, and then the final dynamic model of the whole grasper is formed. To further improve the modeling accuracy, it is creatively proposed that irregular links can be seen as rigid connections of multiple regular links, by which the dynamic model for the deployment motion of the grasper is firstly established via the Lagrange equation. For the grasping motion, since the finger of the grasper can be equivalent to a planar 4R serial mechanism, the dynamic models of the base mechanism and the basic module are established by the Lagrange equation to obtain the relationships between the driving forces and the equivalent torques. The whole grasper is then established by the recursive Newton-Euler method to enhance the modeling efficiency. Finally, the effectiveness of the dynamic model is well verified by the dynamic simulation.

One key issue in inverse kinematic modeling of lower mobility serial mechanisms

• The D-H parameters method for establishing pose coupling equations of serial mechanisms is proposed. • The terminal pose coupling equations of two serial mechanisms are established in closed form. • The feasible positions and orientations of the end-effector for serial mechanisms are determined. The inverse kinematics of lower mobility serial mechanisms is an important problem, but it has not been well solved actually. The feasible six dimension pose of the end-effector can not be reasonably given, which leads to the defect of the inverse solution model of this kind of mechanisms. In this paper, this problem is solved based on establishing the pose coupling equations using D -H(Denavit–Hartenberg) parameters method. The complete inverse kinematics of two 5-DOF(Degree of freedom) serial mechanisms considering pose coupling equations are established to illustrate the improved inverse kinematic modeling process. The results show that the serial mechanisms always have highly coupled nonlinear pose coupling equations which can be effectively used in determining the feasible pose of the end-effector. The proposed inverse kinematics producer is applicable for other serial mechanisms.

A multi-level examination of the link between diversity-related HR practices and employees’ performance: evidence from Italy

ABSTRACT Understanding how diversity-focused HR practices influence individual performance is critical to enhancing organizational competitiveness. In the current article, we examine the effects of diversity-focused HR practices on individual performance in terms of social information processing theory and social exchange theory. In particular, we draw upon constructs of diversity-focused HR practices, inclusion climate, employee relational attachment, and individual performance to hypothesize serial mediation mechanisms linking diversity-focused HR practices to individual performance. We collected time-lagged, multi-level, and multi-source data from 475 employees and their immediate supervisors working in the hotel industry of Italy. Our results demonstrated that diversity-focused HR practices were positively related to inclusion climate, which in turn improved relational attachment among employees. Moreover, diversity-focused HR practices were positively related to individual performance via sequential mediation of inclusion climate and relational attachment.

Design, Assessment, and Trajectory Control of a Novel Decoupled Robotic Nanomanipulator

To avoid the problems of low bandwidth or complex structure brought by conventional serial and parallel mechanisms, a novel decoupled robotic nanomanipulator (DRNM) with a hybrid configuration is conceived in this article to enable fast nanoscale manipulation. The proposed DRNM employs a new hybrid compliant structure to actuate the terminal platform and decouple the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> - and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -axial motions. The unique hybrid mechanism is devised using two H-shaped parallelogram flexures that are assembled in a serial manner and actuated in a parallel manner, bringing in the merits of a flexible terminal platform, compact structure, good decoupling, and wide bandwidth in working directions. To enhance the dynamic positioning performance of the proposed DRNM, a run-to-run-position-forward-based integral controller that can handle the hysteresis nonlinearity of the piezoelectric actuator with adaptive zero-point parameter is further designed. The DRNM prototype is tested having an in-plane resonant frequency of 2005 Hz and a cross coupling of 0.88%. While tracking a circular trajectory with a diameter of 3 µm at a frequency of 20 Hz, the DRNM exhibits a maximum filtered tracking error of 4.3 nm.

Requirements on the Spatial Distribution of Elastic Components Used in Compliance Realization

In this letter, necessary conditions on the locations and orientations of elastic components in a compliant mechanism used to realize any given spatial compliance are identified. The topologies considered are either fully parallel or fully serial mechanisms having an arbitrary number of lumped elastic components. It is shown that the requirements on elastic components are characterized by a sphere for the location distribution and by three cones for the orientation distribution. The easy to assess conditions on the set of components can be used to achieve a more desirable mechanism geometry when used in conjunction with existing spatial compliance synthesis procedures.

Dynamic stability analyzes for a parallel–serial legged quadruped robot

One of the basic characteristics of the walking robots is the maintenance of their dynamic balance during the walk, and the stability of legged robots in locomotion is necessary. In the past few years, the dynamics of legged robots was studied based on very simple or simplified leg structures. A more complete dynamic model is essential for the further research of a practical legged robot. As an important enrichment in stability study for a walking robot, a stability measure named as moment ratio stability margin is introduced, which takes all stability factors into formulation. The mechanical structure of a novel parallel–serial legged mechanism is introduced. Based on this structure, the performance of the proposed method is demonstrated. The advantages and practical significance of the proposed technique are illustrated by comparing it with conventional methods. The experimental study is carried out to evaluate and characterize the performances of this method.

Person-environment fit, organizational commitment and retirement intentions: a serial mediation model

PurposeThe aim of this study is to investigate the effect of person–environment (P–E) fit, specifically person–organization (P–O) fit, on retirement intentions through a serial mediation mechanism mobilizing person–job (P–J) fit and affective organizational commitment as mediators.Design/methodology/approachThe relationships were examined using the Hayes (2013) serial mediation model. A time-lag approach was adopted, with data collected from managers aged 50 and over working in the French banking sector (N = 204).FindingsThe empirical results show that the P–O fit is both directly and indirectly related to retirement intentions through P–J fit and affective organizational commitment. Nevertheless, the study’s findings show the explanatory power of the authors’ antecedents to predict the two types of retirement considered in this study.Originality/valueBy considering retirement in its plurality this study extends prior research models by examining the mechanisms through which P–O fit influences different retirement intentions.

FusionNet: A Convolution–Transformer Fusion Network for Hyperspectral Image Classification

In recent years, deep-learning-based hyperspectral image (HSI) classification networks have become one of the most dominant implementations in HSI classification tasks. Among these networks, convolutional neural networks (CNNs) and attention-based networks have prevailed over other HSI classification networks. While convolutional neural networks with perceptual fields can effectively extract local features in the spatial dimension of HSI, they are poor at capturing the global and sequential features of spectral–spatial information; networks based on attention mechanisms, for example, Transformer, usually have better ability to capture global features, but are relatively weak in discriminating local features. This paper proposes a fusion network of convolution and Transformer for HSI classification, known as FusionNet, in which convolution and Transformer are fused in both serial and parallel mechanisms to achieve the full utilization of HSI features. Experimental results demonstrate that the proposed network has superior classification results compared to previous similar networks, and performs relatively well even on a small amount of training data.

Tight social welfare approximation of probabilistic serial

We study the problem of approximate social welfare maximization (without money) in assignment problems for n agents who have cardinal preferences over a finite set of items. Probabilistic Serial (PS) mechanism is known to be ordinally efficient and envy-free. We prove that its social welfare approximation ratio is Θ(n−12) while no envy-free mechanism can achieve an approximation ratio better than O(n−12). In addition, our proof also implies a Θ(n−12) rank approximation of PS, answering an open question posted in [8].

A repelling-screw-based approach for the construction of generalized Jacobian matrices for nonredundant parallel manipulators

This paper presents a unified and generalized approach for the construction of Jacobian matrices for general, nonredundant parallel manipulators that possess serial and/or mixed-topology limbs. Using linear algebra, a method for the calculation of repelling screws is proposed, based upon which the underlying correlations amongst the screws (twists and wrenches) that correspond to both the permitted, and constrained, motions of general mechanisms are identified and analyzed. The effect of linear combinations on the repelling screw system is revealed, and further used to determine the constraint wrenches/twists of a parallel manipulator and its limbs. By means of utilising repelling screws, the dualities in parallel and serial mechanisms are revisited and extended. Furthermore, a simple and unified method for the identification of unknown twists and wrenches is proposed, based upon which an intuitive and systematic approach for the formulation of generalized Jacobian matrices for nonredundant parallel manipulators is derived. The generalized multilevel hierarchical Jacobian contains complete constraint, singularity, kinematics, and statics information at both limb and platform levels. A number of provided examples demonstrate the effectiveness and application of the proposed approach.

Exploring interdependent privacy – Empirical insights into users’ protection of others’ privacy on online platforms

Recent information privacy research has started to spark a debate about privacy infringements that happen not on an individual, but on a multi-party level. Here, a person’s own information privacy is affected by the decisions of others – a phenomenon referred to as interdependent privacy. Building on the 3R Interdependent Privacy Protection Framework, we explore the underlying mechanisms of how and why interdependent privacy violations happen and how they can be remedied. Drawing on an online vignette experiment (N = 330), we investigate the efficacy of an interdependent privacy salience nudge and reveal that it can decrease the likelihood that users disclose others’ personal information by 62%. Furthermore, we develop a novel measurement instrument and empirically validate that users’ decision to disclose others’ personal information to an online platform is formed via a serial mediation mechanism through users’ realization of the data transfer, recognition of others’ ownership, and respect for others’ rights. We discuss important implications for both theory and practice.

A baseline-reactive scheduling method for carrier-based aircraft maintenance tasks

Carrier-based aircraft maintenance tasks are conducted in time-critical, resource-constrained, and uncertain environments. Optimizing the scheduling allocation scheme of maintenance personnel and equipment, reasonably responding to uncertainty disturbances, and maintaining a high fleet availability are vital to the combat and training missions of carrier-based aircraft. The maintenance task scheduling problem for carrier-based aircraft is investigated in this study. First, a mathematical model for comprehensive carrier-based aircraft maintenance task scheduling that considers constraints such as maintenance personnel, equipment/shop, space, and parallel capacity is developed. Second, to generate the baseline scheduling scheme, an improved non-dominated sorting genetic algorithm II (I_NSGA-II) with local neighborhood search is proposed for the model optimization solution; I_NSGA-II uses the serial scheduling generation scheme mechanism to generate the time sequence scheduling scheme for maintenance personnel and equipment/workshop of different fleet sizes. Third, to cope with dynamic uncertainty disturbances, two reactive scheduling methods, i.e., complete rescheduling and partial rescheduling, are proposed to perform reactive scheduling corrections to the baseline schedule. Case simulation shows that the established mathematical model is reasonable and practical, and that the proposed I_NSGA-II is superior to the current mainstream algorithms. In addition, the decision maker can select between the two reactive scheduling methods flexibly based on the different forms and scales of disturbance.

Posture Evaluation Based on Forward Kinematics and Inverse Kinematics of Parallel Link Type Machine Tool

Parallel mechanisms with multiple links have been expected to be used in machining because they are higher in rigidity, accuracy, and output power than series mechanisms, such as industrial robots. However, unlike conventional machine tools, which consist of linear and rotary axes, parallel mechanisms have a large number of error factors. In the parallel link mechanism, there is no guide surface that physically guarantees linearity, and all accuracy is determined by the operating performance of the composite axes. This makes it difficult to identify any error factors. Therefore, a kinematics model is devised, and the behavior of the tool tip is checked by inputting the encoder information during the actual operation of a specific axis. Based on the results, we evaluate the machining characteristics of the target machine tool. The target machine tool in this study is a 5-axis machine tool that combines a 3-DOF parallel mechanism consisting of three linear motion axes and a 2-DOF serial mechanism consisting of two rotary axes. In our previous research, we tried to build a forward kinematics model. Although its prediction accuracy was insufficient, it was possible to actually identify the cause of the defect in the quality of the machined surface using the servo position information of the kinematics machine. However, we have not been able to construct an inverse kinematics model that is suitable for calculating the correction position command value to improve the quality of the machined surface. In this study, based on the shape creation theory, we devise and evaluate the kinematics model of a robotic machine tool that has a parallel mechanism. As a result of comparing the kinematics model with the 3D-CAD model in order to evaluate the accuracy of the former, it was confirmed that the proposed method has high simulation accuracy. Then, machining tests were carried out to evaluate the machining accuracy by measuring, based on proposed kinematics model, the machined surfaces in order to identify the mechanism that affects the texture of the machined surface. In addition, we performed a circle interpolation to confirm the effects of reversing the motion of each drive axis on the behavior of the tool tip. As a result, it is considered that the linear motion axis has a large effect on the behavior of the tool tip on the quadrant glitch of each drive axis. It was also found that the effects of the 1st- and 3rd-axes on the behavior of the tool tip are different from those of the 2nd-axis.

Kinematic and mechanical error analysis of serial spherical linkages using a modular approach

Although spherical mechanisms have been widely implemented in medical and industrial fields, there still lacks a simple and systematic approach for analyzing their kinematics and mechanical errors. Therefore, the purpose of this paper is to provide a modular approach for kinematic and mechanical error analysis of serial spherical mechanisms that can be decomposed into predefined modules. Firstly, the forward and inverse kinematics, described by rotation matrices, of the spherical serial manipulator are derived. Besides, the error propagations of the spherical serial manipulator are formulated based on the derived kinematic equations. The derived algorithms are programed into subroutines to analyze the kinematics and mechanical error of a serial spherical linkage by analyzing each of its substructures as the illustrative examples have shown. Until now, the presented module in this paper is applicable to a variety of serial spherical mechanisms, and the feasibility of this method adopting high-class modules will be explored in the future.