A physical model of mantis shrimp for exploring the dynamics of ultrafast systems

Efficient and effective generation of high-acceleration movement in biology requires a process to control energy flow and amplify mechanical power from power density–limited muscle. Until recently, this ability was exclusive to ultrafast, small organisms, and this process was largely ascribed to the high mechanical power density of small elastic recoil mechanisms. In several ultrafast organisms, linkages suddenly initiate rotation when they overcenter and reverse torque; this process mediates the release of stored elastic energy and enhances the mechanical power output of extremely fast, spring-actuated systems. Here we report the discovery of linkage dynamics and geometric latching that reveals how organisms and synthetic systems generate extremely high-acceleration, short-duration movements. Through synergistic analyses of mantis shrimp strikes, a synthetic mantis shrimp robot, and a dynamic mathematical model, we discover that linkages can exhibit distinct dynamic phases that control energy transfer from stored elastic energy to ultrafast movement. These design principles are embodied in a 1.5-g mantis shrimp scale mechanism capable of striking velocities over 26 m s−1 in air and 5 m s−1 in water. The physical, mathematical, and biological datasets establish latching mechanics with four temporal phases and identify a nondimensional performance metric to analyze potential energy transfer. These temporal phases enable control of an extreme cascade of mechanical power amplification. Linkage dynamics and temporal phase characteristics are easily adjusted through linkage design in robotic and mathematical systems and provide a framework to understand the function of linkages and latches in biological systems.

Design and Bending Analysis of a Metamorphic Parallel Twisted-Scissor Mechanism

The conventional scissor mechanism is used in modern engineering and robotic applications due to its metamorphic ability. The folding configuration provides the space-saving and unfolding provides longer linear expansion capability. However, a conventional scissor suffers unexpected and uncontrolled large bending deformation due to low bending stiffness while unfolding configuration, which may damage its structure. It also has a sudden bending singularity during unfolding, which may also damage the actuator. These limitations impose a significant constraint on real-life applications such as foldable robot arms, space robot arms, reconfigurable robots, etc. In this paper, we proposed a multi-strands parallel twisted-scissor mechanism (PTSM) to enhance its usability. The PTSM is inspired by a rope structure and designed by introducing a metamorphic segment (MS) using the S-shape linkage design approach to improve its bending stiffness without affecting conventional scissors' fundamentals. The PTSM has a unique feature of several automatic-link locking mechanisms to avoid singularity without using additional sensors, mechanism, or control. We experimentally checked the proposed design's functionality and its feasibility. We formulated a cantilever bending model for foldable PTSM with N metamorphic segments considering revolute joint clearance for bending estimation, experimentally verified, and analyzed the bending deformation in the X-Y and Y-Z planes. Also, it is compared with a conventional scissor. Finally, we found that PTSM is stronger than conventional scissor and can fold/unfold smoothly using a single linear actuator. PTSM can provide large linear displacement with small bending deformation without bending singularity.

Preparing Pathology Data for Linkage

IntroductionThe Tasmanian Data Linkage Unit (TDLU) undertook a complex data linkage project in 2019 linking public and private pathology data to five disparate health datasets. Having linked pathology data previously, the unit was aware of the challenges it faced linking a large dataset covering a fourteen-year time span. The aim of this study was to use data-linkage to develop a Tasmanian dataset to quantify the burden and distribution of chronic kidney disease, including identifying barriers to dialysis treatment services. Objectives and ApproachA cohort was selected from public and private providers of pathology services in Tasmania from 2004-2017 to support the establishment of a comprehensive researchable dataset. A linkage plan was developed that included detailed processes for cleaning and de-duplicating the pathology data prior to linkage. The larger private pathology dataset comprised 3.9 million records and data cleaning strategies were implemented. De-duplication created extensive clerical review and methods to reduce this work were devised and implemented as part of the linkage process. ResultsDe-duplication based on exact matches reduced the size of the dataset from 3.9 million to just over 520,000 individuals. Internal linkage of the dataset resulted in approximately 47,000 ‘groups’ eligible for review. Structured Query Language (SQL) queries were constructed and the number of groups eligible for review decreased by 42%. Further analysis was conducted, which resulted in an appropriate ‘cut off’ threshold being determined for clerical review and an estimate of false positive links remaining was calculated. Conclusion / ImplicationsMethods of reducing the amount of manual clerical review can be incorporated into a linkage design when there is a thorough understanding of the characteristics and content of the dataset to be linked. The methods used for this linkage project will be utilised for future projects using pathology data.

Analysis and Design of an Auxiliary Catching Arm for an Apple Picking Robot

The newly designed 3-dimensional catching robot consists of three revolute joints where the forward linkage is a parallelogram mechanism for keeping the catching end-effector parallel to the picking manipulator’s base. A virtual apple field of 505 apples, designed to test the picking abilities of 7 DOF arm, was used to determine the capabilities of this new catching arm design. The target catching efficiency was 90% for the provided virtual apple field with a maximum drop height of 30 cm. The target coordinates for each virtual apple were found by computer simulation in MATLAB. Geometric parameters were selected such that the catching manipulator could reach every possible drop position in the picking manipulator’s workspace. The design was completed, fabricated, and validated, utilizing the elegant mechanical linkage design. The workspace analysis showed that it had an acceptable 93% catching efficiency, and as the drop height increased, the efficiency approaches 100%. Definitive inverse-kinematics provided exact joint angles required to catch all catchable apples inside of the workspace. Using these angles, the general equation of motion, using Lagrangian mechanics, yielded the required torque outputs of each of the three motors on the arm. Validation of these torques through laboratory experimentation was considered adequate.

Shape-Memory Polymeric Artificial Muscles: Mechanisms, Applications and Challenges

Shape-memory materials are smart materials that can remember an original shape and return to their unique state from a deformed secondary shape in the presence of an appropriate stimulus. This property allows these materials to be used as shape-memory artificial muscles, which form a subclass of artificial muscles. The shape-memory artificial muscles are fabricated from shape-memory polymers (SMPs) by twist insertion, shape fixation via Tm or Tg, or by liquid crystal elastomers (LCEs). The prepared SMP artificial muscles can be used in a wide range of applications, from biomimetic and soft robotics to actuators, because they can be operated without sophisticated linkage design and can achieve complex final shapes. Recently, significant achievements have been made in fabrication, modelling, and manipulation of SMP-based artificial muscles. This paper presents a review of the recent progress in shape-memory polymer-based artificial muscles. Here we focus on the mechanisms of SMPs, applications of SMPs as artificial muscles, and the challenges they face concerning actuation. While shape-memory behavior has been demonstrated in several stimulated environments, our focus is on thermal-, photo-, and electrical-actuated SMP artificial muscles.

Multi-Objective, Reliability-Based Design Optimization of a Steering Linkage

Reliability-based design optimization (RBDO) of a mechanism is normally based on the non-probabilistic model, which is viewed as failure possibility constraints in each optimization loop. It leads to a double-loop nested problem that causes a computationally expensive evaluation. Several methods have been developed to solve the problem, which are expected to increase the realization of optimum results and computational efficiency. The purpose of this paper was to develop a new technique of RBDO that can reduce the complexity of the double-loop nested problem to a single-loop. This involves using a multi-objective evolutionary technique combined with the worst-case scenario and fuzzy sets, known as a multi-objective, reliability-based design optimization (MORBDO). The optimization test problem and a steering linkage design were used to validate the performance of the proposed technique. The proposed technique can reduce the complexity of the design problem, producing results that are more conservative and realizable.

Patterning in Patient Referral to and Uptake of a National Exercise Referral Scheme (NERS) in Wales from 2008 to 2017: A Data Linkage Study

Exercise referral schemes have shown small but positive impacts in randomized controlled trials (RCTs). Less is known about the long-term reach of scaled up schemes following a RCT. A RCT of the National Exercise Referral Scheme (NERS) in Wales was completed in 2010, and the scheme scaled up across Wales. In this study, using a retrospective data linkage design, anonymized NERS data were linked to routine health records for referrals between 2008 and 2017. Rates of referral and uptake were modelled across years and a multilevel logistic regression model examined predictors of uptake. In total, 83,598 patients have been referred to the scheme and 67.31% of eligible patients took up NERS. Older adults and referrals for a musculoskeletal or level four condition were more likely to take up NERS. Males, mental health referrals, non-GP referrals and those in the most deprived groupings were less likely to take up NERS. Trends revealed an overall decrease over time in referrals and uptake rates among the most deprived grouping relative to those in the least deprived group. Findings indicate a widening of inequality in referral and uptake following positive RCT findings, both in terms of patient socioeconomic status and referrals for mental health.

Effect of linkage design of an elbow implant on micro-motion: a finite element analysis

The major reason for total elbow arthroplasty failure is loosening. Loosening is the outcome of a detrimental mechanical incident, which causes the failure of the bond between the bone bed and implant. The shape of the linkage of an elbow implant has a considerable role to transfer a portion of the load to the cement-bone and cement-implant interfaces. Therefore, in this study, the linkage of an elbow implant was modified to reduce loosening using finite element analyses. Elbow bone was constructed using image processing software. Linkage components were modeled using modeling computer-aided design software. Material properties and boundary conditions were applied. The stress distribution and micro-motion were obtained in linkage component and cement-implant-bone interfaces respectively. Based on our results, sub-design 3B proved less interface micro-motion compared to others. Our study showed that modification of a linkage reduces the micro-motion transferred to bone-cement and cement-implant interfaces. A reduction of micro-motion, through linkage modification, may improve the clinical outcomes.