Linkage synthesis: Topology selection fixed by dimensional constraints, study of an example

A compliant gripper with nearly parallel gripping motion is developed by a topology synthesis and a dimensional synthesis approach. The topology synthesis process can generate linkage-type compliant mechanisms. Suitable boundary conditions of the topology synthesis process are selected to achieve the desired functions of the device. The dimensional synthesis is based on an evolutionary optimal design process. To meet various design goals, a nondominated multi-objective genetic algorithm is selected for the optimal design process. A kinetostaic model based on the chained beam constraint model is developed for force–displacement analysis of the designs. Efficiency and accuracy of the design approach are proved by experiments. Appropriate linkage types of compliant mechanisms may be discovered by the topology optimization process before moving on to the dimensional synthesis to obtain final designs.

The ability to calculate represents a complex cognitive process including verbal, spatial, somatic, memory, and executive functions. The origin of mathematical concepts can be traced to subhuman species. The immediate recognition of certain small quantities without counting – subitizing – is found not only in animals but also in small children. During child development, different stages in the acquisition of numerical knowledge are observed, including global quantification, recognition of small quantities, enumeration, correspondence construction, counting, and finally permutability (arithmetic). Some numerical abilities, such as correspondence construction, probably existed in prehistoric man. In human history, as well as in child development, counting begins with sequencing the fingers; this may be the reason for the frequent use of a decimal system. Written numbers appeared in history before written language. Neuroimaging techniques have demonstrated that different brain areas are active during arithmetical tasks, but the specific pattern of brain activity depends on the particular type of task that is performed. It can be assumed that during human history, the development of new numerical abilities was correlated with the involvement of new brain areas during the performance of progressively more complex numerical tasks. Mediators used in numerical cognition continue evolving with the introduction of new contemporary technologies.

This chapter describes an identification task and associated test methodology. Image quality is quantified by the ability to identify objects in a test set. Chapter 7 describes an imager resolution metric that predicts the ability of observers to perform the identification task. The resolution metric predicts the impact of imager blur, noise, and sampling on target identification. This chapter also discusses the use of diverse target sets to establish operational utility. In a target acquisition sense, the focus is on the average probability of identifying many objects in the scene. The ability to identify a specific target is not addressed. The focus on diverse target sets greatly simplifies the analysis presented in Chapter 7. Also, if the goal of imager analysis is to select a good imager for a particular type of task, target sets provide a better way to quantify performance than specific target analysis. Using standard target sets to check visual acuity is quite common. In Fig. 6.1, the patient is reading an eye chart in the optometrist's office. The doctor tells her to read the smallest line she can. Many others have tried to read this or similar charts. The doctor knows the letter size that represents average vision. Reading the chart provides a quantitative method of comparing vision among observers. Using high-contrast letters is not the best way to check vision, however. A scene consists of many luminance levels. The eye achieves an integrated view of objects by connecting lines and surfaces. These lines and surfaces do not share a particular brightness throughout their extent. For example, the background immediately behind a target might not be uniform, and yet the eye sees the target silhouette. Perspective is gained from converging lines even if they vary in luminance with increasing range. Slight changes in hue or texture can provide an excellent cue as to the distance and orientation of an object. Acute vision requires not only the ability to discriminate small details that happen to have good contrast, but also the ability to discriminate small differences in shades of gray.

In the past few years, volunteers have produced geographic information of different kinds, using a variety of different crowdsourcing platforms, within a broad range of contexts. However, there is still a lack of clarity about the specific types of tasks that volunteers can perform for deriving geographic information from remotely sensed imagery, and how the quality of the produced information can be assessed for particular task types. To fill this gap, we analyse the existing literature and propose a typology of tasks in geographic information crowdsourcing, which distinguishes between classification, digitisation and conflation tasks. We then present a case study related to the “Missing Maps” project aimed at crowdsourced classification to support humanitarian aid. We use our typology to distinguish between the different types of crowdsourced tasks in the project and choose classification tasks related to identifying roads and settlements for an evaluation of the crowdsourced classification. This evaluation shows that the volunteers achieved a satisfactory overall performance (accuracy: 89%; sensitivity: 73%; and precision: 89%). We also analyse different factors that could influence the performance, concluding that volunteers were more likely to incorrectly classify tasks with small objects. Furthermore, agreement among volunteers was shown to be a very good predictor of the reliability of crowdsourced classification: tasks with the highest agreement level were 41 times more probable to be correctly classified by volunteers. The results thus show that the crowdsourced classification of remotely sensed imagery is able to generate geographic information about human settlements with a high level of quality. This study also makes clear the different sophistication levels of tasks that can be performed by volunteers and reveals some factors that may have an impact on their performance.

Comprehensive approach for the dimensional synthesis of a four-bar linkage based on path assessment and reformulating the error function

Optimization of linkages for generalized rigid-body guidance synthesis based on finite element models

This study combines product- and process-oriented research methods and tools to observe whether and how the presence of pre-translated text affects translation quality and influences the translator’s research patterns. It is part of the LeMaTTT project, a simulated longitudinal empirical study exploring the impact of MT on info-mining and thematic competences in legal translation. Data were elicited through a translation task completed by a cohort of 110 final-year MA trainees with training in legal translation and basic MT literacy, and a cohort of 54 first-year MA trainees with no to very limited experience in specialised translation and post-editing. This paper provides a first analysis of selected process-related data concerning the allocation of time and the use of external resources throughout the translation or post-editing processes of 40 participants, 20 from each cohort. Preliminary results highlight some correlations between the use of time and external resources and both (a) the development of thematic and info-mining competences and (b) the specific type of task, i.e. whether from-scratch translation or post-editing.

Compliant mechanisms have been defined as mechanical systems that derive some or all of their mobility from the flexibility of one or more of their members. In general, due to the large-deflection nature of the compliant members, analysis and synthesis of compliant mechanisms have typically required a numerical iterative solution method. Recently, analytical loop-closure synthesis techniques have been extended to the design of compliant mechanisms, by utilizing the concept of an equivalent pseudo-rigid-body model for a compliant mechanism. These developments have greatly simplified the synthesis of compliant mechanisms. These mechanisms have been synthesized for three precision points using analytical and graphical methods. In rigid-link mechanism design, additional precision points may be incorporated by using Burmester theory. With this enhancement as the motivation, this paper presents the first use of Burmester theory to design compliant mechanisms for four and five precision points. This is facilitated by use of the concept of an equivalent pseudo-rigid-body model. Burmester theory yields a linear set of kinematic equations, allowing for their easy utilization herein. Also for some design problems, this theory can provide a graphical representation of all possible solutions for compliant mechanisms. In addition to the specification of precision points for compliant mechanisms, input torque and/or potential energy values may also be prescribed.

This paper presents the design and simulation of a jumping mechanism as a means of flight initiation in Flapping Wing Micro Air Vehicles (FWMAV) inspired by birds. Most flying birds take off for flight from standing or perching position at low air speed. A lightweight 4-bar leg mechanism has been designed using dimensional synthesis by motion generation. Graphical and analytical methods are established to determine the kinematic dimensions that fulfill some prescribed take-off maneuvers. Link cross sections have been optimized to reduce weight. The jumping leg has been tested with an efficient aerodynamic model that accurately predicts unsteady flapping wing aerodynamic characteristics just after launching. Transition of forces from leg to wings has been analyzed. For a jumping angle of about 50 degrees at 10m/s the 33.3 g ornithopter model gains momentum and reaches steady state flight at a velocity close to the initial value.

The paper considers dimensional synthesis of a path generator four-bar linkage by applying the modified Differential Evolution (DE) algorithm. During the search of the space, the DE algorithm may skip the right solution and lead to premature convergence. If the step is reduced, the search space is reduced as well, so that convergence becomes slower. Search efficiency may be achieved by including Lévy Flight in the DE algorithm. Namely, when the DE algorithm identifies the space of best solution, then a Levý Flight step is used for local search in that region, which significantly increases the exploitation capability and allows obtaining a very efficient solution of the optimization problem. The algorithm was tested with three examples of dimensional synthesis of a path generator four-bar linkage. The proposed algorithm can be very efficiently applied to solving very complex optimization problems.

This paper, a sequel to a companion paper on function generation, discusses the path and motion generation problems in the synthesis of linkages with relatively small input cranks. The point on the floating link (i.e., the coupler of a crank-rocker linkage or the connecting rod in a slider-crank linkage) traces an approximate ellipse. This fact serves as a major distinction between the method described herein and the conventional, more general, synthesis techniques. In other words, only elliptical paths may be generated by the path (or coupler) points in the synthesis of linkages with small cranks. Higher-order path and motion generation, in which velocity, acceleration, slope and the rate of change of slope of the coupler path may be specified, are also addressed in this paper.

Spherical parallel manipulators (SPMs) have promising industrial applications due to their strong mechanical performance. However, they face challenges such as singularity avoidance, tight tolerance manufacturing requirements, and the need for versatile and dexterous end-effector functionalities. Additionally, SPMs lack customizability due to singularity and collision issues. This work introduces a novel design principle that addresses these challenges by benchmarking two analytical methods: structural synthesis using screw theory and dimensional synthesis using dimensionless parameters. A proof of concept of a 2-DoF SPM that can operate within a cylindrical constraint and realize a full workspace without collision is presented. This design allows for adjustable reachable workspace at the end-effector, despite significant geometric constraints. These findings on mechanical design solutions provide customizability for SPMs, and a 3D model with an aspect ratio of 1/12 is presented and discussed for potential practical applications. Overall, it is identified that both a simulation using Recurdyn and inverse kinematic model show the desired movements at the moving platform with the maximum error of 0.0013°.

Cuckoo Search algorithm: A metaheuristic approach to solving the problem of optimum synthesis of a six-bar double dwell linkage

GA\SQP optimization for the dimensional synthesis of a delta mechanism based haptic device design

A structural dynamic model of the human brain has been developed using finite element techniques. In the modeling process, soft tissue and internal fluids are discretized into solid 8‐node elements. One dimensional nodal constraints and membrane elements represent skull and internal folds of the dura, respectively. The geometric shapes of the cerebri, cerebellum, and brain stem are carefully duplicated. As a consequence of this emphasis on geometric detail, more than 1000 degrees of freedom are utilized. Linear elasticity and small deformations are assumed. The dynamic characteristics of the brain model are investigated. Symmetric and unsysmmetric natural frequencies and normal modes are presented, and their effects on brain response and injury are discussed. The rotational character of the lower modes clearly demonstrates the importance of head rotation in brain injury research. A comparison of modes computed with and without the internal folds of dura (the falx and tentorium), reveals that these membran...