bluuebunny/crossref_metadata_2025 huggingface dataset:
An Inexpensive Course on Layered Manufacturing and Rapid Prototyping
Authors: Bøhn Jan Helge
Published: February 2021

Rapid prototyping is revolutionizing the design process. With it, less designs are being sent directly, untested, into production. Instead, designs can now be aggressively prototyped to significantly reduce the likelihood of having to correct design errors late in the product life cycle.

This paper reports on a new, experimental first-year graduate-level course that offers the students the opportunity to explore the concept of rapid prototyping and its impact on the design process. The emphasis of the course is to familiarize students with available and forthcoming automated fabrication technologies, that, when combined with secondary processing technologies, facilitate aggressive prototyping as an integral part of the design process. In particular, students are encouraged to compare and contrast the various layered manufacturing technologies and CNC machining with respect to the prototyping needs of a designer.
Fuzzy Control of an Inverted Pendulum
Authors: Balkan Tuna , Ari Mehmet Emin
Published: February 2021

An inverted pendulum system has been designed and constructed as a physical model of inherently unstable mechanical systems. The vertical upright position of a pendulum is controlled by changing the horizontal position of a cart to which the pendulum is hinged. The stability of the system has been investigated when a fuzzy controller is used to produce the control signal, while making a single measurement. It has been shown that by using simple fuzzy rules to allow real time computation with a single angular position measurement, the system can not be made absolutely stable. However, the stability and performance of the system have been considerably improved by shrinking the membership functions of angular position, computed angular velocity and control signal when inverted pendulum is very close to the vertical upright position.
Spreadsheet Simulation for Quick Manufacturing Analysis
Authors: Petersen Harry C.
Published: February 2021

Spreadsheet simulation was used to estimate peak current demands of a hypothetical welding line for LRT car bodies for energy management. Power companies factor peak power draw into their rates; high momentary power demands can result in surges and brown-outs. Rates are often based on the power used in KVA, and also on the peak current. Exceeding that peak could result in an extreme penalty. The spreadsheet simulation which developed the peak power demands generated random numbers and maped them onto resistance welder data using Monte Carlo sampling. Peak power usages were developed for the welding line during 10,000 momentary “snapshot” simulations, contracting for a 400 KVA peak, and installing a 400 KVA circuit breaker rather than pay a rate penalty. Results were developed in a few hours using a microcomputer spreadsheet program. Other potential uses of spreadsheet simulation are listed.
Finite Element Analysis of Rotational Contact-Impact Behavior of a Geared Rotor System
Authors: Tanabe Makoto , Jiang Chen Jie , Takazawa Koya
Published: February 2021

A simple and efficient finite element formulation and numerical method to solve it for the rotational contact-impact behavior of a geared rotor system are given. A gear element is devised to model the contact-impact behavior between gears in which the irregularity of tooth pitch is also considered. A computer program has been developed to solve this problem. Numerical examples of an electric disk grinder are demonstrated and compared with the experimental result to show the effectiveness of the present method.
The Functional Feature Model: Bridging the CAD/CAM Gap
Authors: Wearring Colin
Published: February 2021

Commercial CAD systems were originally developed to support the generation of 2D engineering drawings, but evolved to support development of 3D product models. Conceptually, the product model replaces 2D engineering drawings as a means for communicating product information such as size, shape, features, datums, tolerances, and other engineering specifications. Because of their history, the software architecture and data models used by commercial CAD systems do not directly represent all the engineering product information contained in 2D engineering drawings.

Computer Assisted Engineering (CAE) tools require engineering product specifications as input. When these tools are integrated directly with the CAD system, a database representation of the product model is required for their efficient operation. Without a direct link to the CAD system, information must be transferred using standard format files, or manually entered into the CAE application. To satisfy the requirements for direct integration of CAE applications with CAD systems, the Functional Feature Model (FFM) was developed. By definition, the Functional Feature Model (FFM) contains component geometry, feature definitions, datums, datum features, tolerances and other feature attributes accessed through a standard interface.

The FFM was named to distinguish the functional features used by an engineer in the definition of part function, inspection, and assembly from the features employed by CAD systems in construction of geometry. Today, the FFM is used as the basis for CAE tools which perform analysis of product Geometric Dimensioning and Tolerancing (GD&T), 3D tolerance analysis of assemblies, and CMM programming. Any CAE application which requires the same or similar information as these applications can obtain its input from the FFM.

The FFM is a mature, commercially proven prototype for a standard product model, containing the majority of engineering product information typically represented using 2D drawings annotated with Geometric Dimensional and Tolerancing (GD&T) symbols. The FFM can be used instead of 2D drawings to supply necessary product information to CAE applications. Using the FFM, there is no need to create the 2D engineering drawing, interpret the GD&T annotation, and enter the interpreted product information into the CAE application. It provides a standard interface (independent of CAD system) for commercial development of CAE applications, and is designed in a fashion which makes it appropriate for use as a basis for emerging product model standards.

The FFM provides a prototype for related activities like the Standard for the Exchange of Product Model Data (STEP) initiative represented by the Product Data Exchange using STEP (PDES) organization in the USA. Corporate and government consortiums such as the Rapid Response Manufacturing (RRM) or Simulation Assessment Validation Environment (SAVE) initiatives could employ the FFM directly to support their objectives of developing the next generation design and simulation environment.
Pressure Distributions of Drum Brakes
Authors: Huang Yuan Mao , Shyr J. S.
Published: February 2021

With the assumptions that the interface between the brake drum and the lining plates is perfect contact, that the friction coefficient is constant, that the thermal effect is neglected, that the brake drum and metal shoes are rigid, the pressure distributions of drum brakes are studied by using the boundary element method. The constant element is used in the two dimensional model of the drum brake for simplicity and economy. The pressure distributions on the metal shoe and the lining plate and the friction force versus the effective cam lift are compared and show good agreement with the available data. The effects of the Young’s modulus of elasticity, the angle of the arc length, the friction coefficient, the location and the thickness of the lining plate, the Young’s modulus of elasticity and the angle of the arc length of the metal shoe, and the angle of the actuating force on the pressure distributions of the drum brakes are then studied.
Geometric Tolerance Analysis for Mechanism Design
Authors: Tsai Jhy-Cherng
Published: February 2021

Manufacturing tolerances and joint clearances are the two major factors affecting mechanism accuracy. As error analysis is one of the bottlenecks of precision machinery design, methods for geometric tolerance analysis must be investigated for mechanism design. This paper describes an approach for analyzing errors caused by geometric tolerances and clearances in mechanism design. The method consists of three parts: variational kinematic models for geometric tolerances, a systematic geometric dimensioning and tolerancing (GD&T) representation scheme, and computation methods for interval and statistical tolerances. Variational models are based on differential transformation to model kinematic errors caused by tolerances and clearances. The model is consistent with error models used in typical mechanical devices. The GD&T scheme, called the Tolerance Network (TN), employs graph theory for representing GD&T as well as fitting specifications of a design is described. Errors are propagated by traversal throughout the network and stack-up of these variational models along the dominate path in the TN. Error computation methods for both interval and statistical tolerance types are discussed. A method for computing central moments, rather than analytical distributions, of statistical tolerances is developed to reduce the computation complexity. A five-degree-of-freedom robot is used as an example at each step to illustrate this approach.
Variant Shape Model Applicable to Combined Geometric Tolerances
Authors: Inoue Keisuke , Okano Akira
Published: February 2021

This paper describes a variant shape model and its application to tolerance analysis. To realize a high-precision mechanism at low cost, designers specify various types of tolerances selectively, often in combination on a single face.

We propose a solid model that has attributes at points scattered over its faces. In this model, the macroscopic geometry is represented as a B-rep solid model, and the microscopic geometry (manufacturing errors and clearances) as attributes. The model can represent a wide variational class, such as shapes with form errors. We use it to present a method for generating a deviant shape model having a specified set of geometric errors.

After deviant part shapes have been generated, they are assembled virtually in such a way that they do not interfere with each other and that the physical conditions of the attachment are satisfied. Through a large number of deviant assemblies, a product’s performance is analyzed statistically and quantitatively.
Optimization of Deep Drawing Processes Using Statistical Design of Experiments
Authors: Bauer Dietrich , Krebs Regine
Published: February 2021

For a deep drawing process some important controllable variables (factors) upon the maximum drawing force are analyzed to find a setting adjustment for these process factors that provides a very low force for the metal forming process. For this investigation an orthogonal array L18 with three-fold replication is used. To find the optimum of the process, the experimental results are analyzed in accordance with the robust-design-method according to Taguchi (Liesegang et. al., 1990). For this purpose, so-called Signal-to-Noise-ratios are calculated. The analysis of variance for this S/N-ratios leads to a mathematical model for the deep drawing process. This model allows to find the pressumed optimal settings of the investigated factors. In the following, a confirmation experiment is carried out by using these optimal settings. The maximum drawing force of the confirmation experiment does not correspond with the confidence interval, which was calculated by analysis of variance techniques. So the predicted optimum of the process does not lead to a metal forming process with very low deep drawing force. The comparison with a full factorial plan shows that there are interactions between the investigated factors. These interactions could not be discovered by the used orthogonal array. Thus the established mathematical model does not describe the relation between the factors and deep drawing force in accordance with the practical deep drawing conditions.
Genetic Algorithm Based Optimal Planning Method of Energy Plant Configurations
Authors: Fujita Kikuo , Akagi Shinsuke , Yoshida Kiyotaka , Hirokawa Noriyasu
Published: February 2021

A genetic algorithm based optimization method is proposed for the planning problem of energy plant configurations. In such a planning problem, a plant configuration, i.e., types, models, and numbers of equipment, is determined so as to satisfy required energy demand conditions and to minimize the sum of plant facility cost and input energy cost. This is a combinatorial optimization problem similar to the knapsack problem, which is hard to find an optimal configuration for due to the huge number of alternatives. In this paper, we apply a genetic algorithm to such an optimal planning problem by representing a plant configuration with bit vectors and by arranging cost functions so as to keep search performance superior against the deceptive problem. The method is implemented on a symmetric shared-memory, multi-CPU workstation, where almost linear speedup is accomplished. Its performance is demonstrated by computational examples of a cogeneration plant and comparison results with a random search and a simulated annealing method.
Spot Weld/Adhesive Pattern Optimization
Authors: Yang R. J. , Rui Y. , Mohammed A. , Singh G.
Published: February 2021

This research presents a new application of topology optimization. Patterns for spot weld location and adhesive distribution when joining body panels are determined by using the topology optimization method. The density method which parameterizes the density of each finite element is employed and a sequential linear programming method is used for solving the topology optimization problem. In this study, a B-Pillar to Rail Joint exemplifies the design methodology. The results show that patterns for optimal spot weld location and adhesive distribution can be obtained for a maximum stiffness design with mass constraints.
Packing of Generic, Three-Dimensional Components Based on Multi-Resolution Modeling
Authors: Kolli Ashish , Cagan Jonathan , Rutenbar Rob
Published: February 2021

A method of optimizing layouts of three-dimensional objects of arbitrary geometry with simulated annealing is presented in this paper. Using multi-resolution models, this approach is able to generate optimal layouts of three-dimensional objects in reasonable time. An example of packing highly non-convex objects illustrates the power of this method.
Generalized Abbe Principle: Position Error Propagation in Machine Elements
Authors: Pegna Joseph
Published: February 2021

In the quest for ever finer levels of technology integration, mechanical linkages reach their precision limits at about 5micrometers per meter of workspace. Beyond this physical limit, all six dimensional degrees of freedom need to be precisely ascertained to account for mechanical imperfections.

This paper substantiates Wu’s vision of “precision machines without precision machinery.” A formulation and statistical characterization of position and orientation error propagation in rigid bodies are presented for two extreme models of measurement. It is shown that error distribution is uniquely dependent upon the design of the measurement plan. The theoretical foundations presented were evolved in the course of designing precision machinery. Other potential applications include: fixture design, metrology, and geometric tolerance verification.
Foraging-Directed Adaptive Linear Programming: An Algorithm for Solving Nonlinear Mixed Discrete/Continuous Design Problems
Authors: Lewis Kemper , Mistree Farrokh
Published: February 2021

Design models often contain a combination of discrete, integer, and continuous variables. Previously, the Adaptive Linear Programming (ALP) Algorithm, which is based on sequential linearization, has been used to solve design models composed of continuous and Boolean variables. In this paper, we extend the ALP Algorithm using a discrete heuristic based on the analogy of an animal foraging for food. This algorithm for mixed discrete/continuous design problems integrates ALP and the foraging search and is called Foraging-directed Adaptive Linear Programming (FALP). Two design studies are presented to illustrate the effectiveness and behavior of the algorithm.
The Effect of a Fractal Profile Tolerance on the Dynamic Performance of Cams
Authors: McAdams Daniel A. , Wood Kristin L.
Published: February 2021

To ensure a successful design, it is important to understand the effect that design parameters have on design performance. Tolerances are an important subset of design parameters. In this paper, the relevance of fractal surface characterization for profile tolerances is investigated. The notion of fractal geometry is discussed. The validity of a fractal characterization on a cam surface is determined. Dynamic simulations of a cam-follower system are used to qualify the effect of a fractal profile error on system performance.
A Knowledge-Based System for Machining Operation Planning in Feature Based, Open-Architecture Manufacturing
Authors: Stori James A. , Wright Paul K.
Published: February 2021

Within the Integrated Design And Manufacturing Environment (IMADE), operation planning provides a mapping from geometric design primitives to machining operation sequences for manufacturing processes. Operation planning includes tool selection, machining parameter selection, and tool path generation. An object oriented approach to program structure is adopted, whereby features, operations and tools, inherit behaviors and attributes from the appropriate class-hierarchies for the part, the manufacturing operations, and tooling classes. A detailed example is presented illustrating the operation planning search algorithm. Scripts are generated by the individual machining operations for execution on a machine tool. Tooling information is maintained in an object-oriented database through the FAR libraries for Common LISP. Examples of particular process plans show that the inherent trade-offs between specified precision and machining time can be investigated. An Open Architecture Machine Tool (MOSAIC-PM) has been used to machine the parts created by the feature based design and planning system. The novel contributions of this paper relate to the demonstration of “seamless” links between, a) design, b) planning, and c) actual fabrication by milling.
Manufacturability Analysis Using High-Level Process Planning
Authors: Herrmann Jeffrey W. , Lam Giang , Minis Ioannis
Published: February 2021

Virtual enterprises utilize the resources of the most capable partners for mutual benefit. This paper describes a high-level process planning and manufacturability analysis approach which increases decision support at the product design stage and reduces time to market by integrating the process of forming the virtual enterprise with design critiquing and process planning so that the designer can develop the process plan and evaluate the design with respect to the capabilities of the potential partners early in the design cycle. Alternative high-level process plans are generated based on the product design requirements, process capabilities, and plant performance measures. The manufacturability of each design-process plan combination is evaluated by estimating the cost, lead time, and expected quality of each high-level process plan.
Compact 2D Pattern Development From 3D Polygonal Surfaces
Authors: Wang Cheng-Hua , Bourne David A.
Published: February 2021

Pattern development involves mapping 3D surfaces into 2D flat patterns. To reduce the complexity of patterns, approximations of the surfaces into polygonal surfaces such as quadrilateral or triangular facets are usually necessary. This paper is concerned with the pattern development of polygonal surfaces with a special reference to bent sheet metal parts. The development process needs to consider the unfoldability of 2D patterns. The unfoldability requires that the 2D pattern does not overlap itself, and the faces of the part do not distort during bending. For some designs, there are multiple 2D patterns that can all be bent into the same 3D shape. The compact pattern is usually selected due to better stock utilization in cutting and nesting and ease of handling during bending. We show that the development of the compact 2D pattern can be converted into a minimum cost spanning tree problem. This approach has been implemented using an A* search algorithm and several examples are presented.
A Coordinated Product and Process Development Environment for Design for Assembly
Authors: Lee David E. , Hahn H. Thomas
Published: February 2021

The development approach embodied in design for assembly (DFA) has been demonstrated effectively in different industrial sectors and through the design of a multitude of products. However, little effort has been applied to improving development methods for the assembly operations and processes used to fabricate these products. If the benefits of concurrent engineering are to be fully realized, a more holistic approach to unifying a product’s design with development of its assembly processes is needed. This paper provides a description of our approach to establishing an environment for coordinated product and assembly process development. The steps in a product’s development cycle are introduced and the concepts of design for assembly and concurrent engineering defined. Using DFA methods as a motivation, an approach to assembly process development is derived. Referred to as Systematic Assembly Process Development (S-APD), assembly processes are defined and analyzed by using standardized generic assembly operations. To address problems created by using concurrent engineering in product/process development, two mechanisms are described. Since the focus of developing a product (i.e. how well does it perform and cost) differs from developing its assembly processes (i.e. making products at the necessary volumes), the concept of an interface reference context is introduced as a coordination mechanism and applied to development of unmanned composite low-cost aircraft. Moreover, in identifying which elements of the design are to be assembled with a specific set of production technologies, a synchronous thread is instantiated to link product and assembly process development efforts in a temporal context. Different approaches are reviewed to resolve potential conflicts related to concurrency effects generated during simultaneous product and assembly process development.
Enabling Digital Mock-up With Virtual Reality Techniques: Vision, Concept, Demonstrator
Authors: Dai Fan , Reindl Peter
Published: February 2021

Mock-ups and prototypes are very important for design evaluations. In the automotive and aeronauic industries, CAD and CAE systems are used more and more. There is a strong attempt to replace a great part of mock-ups with digital models — the so called Digital Mock-Ups. Many companies have started to evaluate existing tools and technologies, and think about, or begin to develop virtual prototyping systems for their own needs. In this paper, we present the idea of Digital Mock-Up which is developed within the ESPRIT project AIT - Advanced Information Technologies in Design and Manufacturing1, and show the vision of virtual prototyping — the use of virtual reality techniques for Digital Mock-Up, based on the AIT-DMU-demonstrator.
Distance Learning of Skills
Authors: Fukuda Shuichi , Matsuura Yoshifusa , Wongchuphan Premruedee , Takahashi Tokiko
Published: February 2021

With the increasing globalization and expansion of the people’s activities, distance learning is getting wide attention. Distance learning is not a computer aided education system alone. What is important is that collaboration over the network is a prerequisite for that, so that the technology developed there will be easily utilized for distance manufacturing and other collaborative activities over the network.

When we come to think of integrating design and manufacturing over the network, the problem of skill comes up. Skill plays a very important role in manufacturing. But most of the systems developed so far have been focusing their chief attention toward how rigously they can represent design and manufacturing knowledge and experience in terms of symbols, and non-symbolic approaches are still few.

It is believed that motion occupies a large portion of skills, but the present systems being such, and in additon, such media as TV, video, etc are one way from a teacher to a student so that it is still very difficult to learn skills over the network, since skill learning requires much interactive processes. Otherwise, students find it very difficult what part of the model motion they should concentrate their focuses.

If a teacher can edit the motion of a student and a student can watch how his or her motion is edited, the student will understand more easily what is wrong with his or her motion., and can identify where his or her attention should be focused.

Based on this idea, we have developed a preliminary system for distance learning of skills to demonstrate the effectiveness of the approach.
Industrial Applications of Conceptual Robustness
Authors: Chang Tzyy-Shuh , Ward Allen C. , Schmidt Jason W. , Stenman Michael A.
Published: February 2021

We have introduced the idea of conceptual robustness to formalize distributed concurrent engineering (Chang, et al., 1994; Chang and Ward, 1995a) and design-in-modularity (Chang and Ward, 1995b). This paper reports two industrial applications of conceptual robustness, one for distributed concurrent engineering and the other for modular design. The formulations delivered satisfactory solutions to both cases.
Classifying Functions for Mechanical Design
Authors: Kirschman C. F. , Fadel G. M. , Jara-Almonte C. C.
Published: February 2021

As design methods are studied, the usefulness of function-based methodologies becomes clear. However, for these methodologies to be fully utilized, there must be some standardization of the functions used to provide a common language. This paper presents a proposed taxonomy of elemental mechanical functions which can be used with many decomposition techniques. The taxonomy can be used as a pedagogical tool or as a basis for the derivation of a complete taxonomy.
Design for Assembly Techniques in Reverse Engineering and Redesign
Authors: Lefever Douglas D. , Wood Kristin L.
Published: February 2021

Design for Assembly (DFA) is the process by which a product is designed to be easily assembled. Such design simplifications are accomplished through reducing the number of operations required to assemble the product, improving the handling of each component, and/or modifying the required operations (insertion, joining, etc.). There exist several techniques for assessing the assemblability of a design through an analysis of these three aspects. However, there also exists a clearly defined need for evolving such techniques to indicate how a product should be redesigned with respect to customer needs and associated functionality. This paper presents three such evolutions, aimed at reducing the number of components in an assembly during redesign. The first technique is a component elimination procedure, the second technique is a component combination analysis, and the third technique establishes a logical approach for revealing more abstract component elimination or combination opportunities. These three DFA techniques are integrated within a reverse engineering and redesign methodology. They are then applied to a industrial design application, i.e., redesign of an auxiliary automobile visor. Results demonstrate definitive part count reduction, while maintaining and improving design functionality.
Principles From Toyota’s Set-Based Concurrent Engineering Process
Authors: Sobek Durward K. , Ward Allen C.
Published: February 2021

A five-year study reveals that the highly successful Toyota Motor Corporation seems to follow a different paradigm of design than other US and Japanese auto companies. This paper outlines 11 principles that appear to form the foundation of Toyota’s use of “Set-Based Concurrent Engineering.” Discussion of the principles includes illustrations from Toyota.
Validation Studies of an Information-Flow Model of Design
Authors: Christian Andrew D. , Grasso Kamala J. , Seering Warren P.
Published: February 2021

This paper describes results obtained from an information-flow model of the design process. The model represents design projects as tasks to be accomplished and information to be exchanged. An event-based simulation uses computer agents to represent engineers working on the design project within a virtual office environment, exchanging information, and making decisions. The first of two validation studies presented in this paper uses corporate records and timesheet data to construct a model and compare simulation results with actual project results. The second study evaluates the ability of a manager unfamiliar with the software to set up a model of a design project and to gain useful insights by exercising the model.
An Analysis of Multiple Peg-in-Hole Insertion Tasks
Authors: Sturges Robert H. , Sathirakul Korntham
Published: February 2021

In this paper an analysis of the physics of a multiple peg-in-hole assembly task is addressed. Insertion of three pegs, arranged in an equilateral triangle, into three holes simultaneously is chosen as an example case. Although a 3 dimensional problem, the small-angle assumption reduces the model to only 3 degrees of freedom: 2 translations in the XY plane and a rotation about the Z axis. The multiple-pegs are viewed as points in a 3 dimensional configuration-space (C-space.) The net force and torque due to contact during chamfer crossing at each point in the C-space are determined. It is shown that the net force and torque are in the directions of minimizing the lateral and angular errors of the pegs. Based on these data together with compliance models of Remote-Center Compliance (RCC) and Spatial RCC (SRCC), the force and torque that occur during multiple-peg insertion using these passive devices are predicted. The result from the prediction is used to compare the performance of the two devices, and to design strategies for successful insertion of this assembly task.
Preliminary Experiments on Using Direct Calibration As an Approach for Automated Windshield Loading
Authors: Murray William R. , Pohlhammer Christopher M. , Wilson Paul C.
Published: February 2021

Assembly experiments are described that were conducted to evaluate direct calibration, a straightforward approach to the calibration problem for sensor-guided assembly systems. In direct calibration, the entire assembly system — the robot, the sensors, and the parts to be assembled — is calibrated for the required assembly task in a single procedure to directly determine the relationship between the part feature information in sensor coordinates and the part location in robot coordinates. This calibration procedure is accomplished in two steps: calibration data are generated by using the robot to move the part(s) to be assembled under the view of the sensors; and the best-fit mapping representing this assembly process is determined.

In this research project, the method of direct calibration is applied to the use of a vision-guided robotic system to install windshields in automobiles. Glass installation on the automotive assembly line is a delicate and difficult-to-automate assembly task. In the approach to windshield loading proposed herein, direct calibration is used to provide robust estimates of the location of both the windshield and the windshield opening, or aperture, in the car body. This location information is used to modify the taught insertion path such that each windshield is inserted into the corresponding aperture in the same manner that the windshield at calibration was inserted into the aperture at calibration.

To evaluate direct calibration as an approach in windshield loading and to determine the level of performance achievable with common industrial hardware, simplified 3-DOF assembly experiments were conducted. Results from these preliminary experiments indicate that direct calibration is a promising technical approach for the industrial application of automated windshield installation.
Workspace Representation of Parallel Manipulators Using the Finite Twist Method
Authors: Singh H. , Dai J. S. , Kerr D. R.
Published: February 2021

A method has been developed that successfully represents the workspace of a parallel manipulator within a finite twist image space. A point in this space represents a unique position and orientation of the end effector. The method of analysis is based upon the established technique of simplifying the parallel manipulator, by modelling each leg as an independent serial manipulator. The workspace corresponding to each serial manipulator is mapped onto the image space to produce a hyper-volume. The intersection of the individual hyper-volumes represents the workspace of the complete parallel manipulator. Since the hyper-volume corresponds to all possible positions attainable by the end effector, this represents the reachable workspace. Within the reachable workspace there lies subsets of volumes in ⮲3 that correspond to all possible orientations attainable. Such volumes represent the dextrous workspace. Although the method is illustrated by the use of a Stewart platform, it is equally applicable to the general parallel manipulator. The method is demonstrated successfully by the use of a 3 legged, 3-DOF planar parallel manipulator.
Optimization-Based Grashof-Mechanism Synthesis via Sub-Type Specific Parameter Transforms
Authors: Podhorodeski Ron P. , Fang Xiaoqi
Published: February 2021

Transformations are developed to allow mapping from an unconstrained n-dimensional search variable set to n link length values describing a constrained linkage within a specific mechanism sub-type. The transformations are based on redefining link length limits, incorporating “Grashof-criteria” considerations, concurrently with the transformation of the unconstrained variable set values. The technique facilitates effective optimization allowing search and convergence within a preferred mechanism sub-type. A transform is presented for a Grashof four-bar (crank-rocker), the methodology being easily applied to other single and multiple-loop planar mechanisms. The developed transforms are demonstrated to be effective through application in the synthesis of mechanism dimensions for a deep-digging implement.
The Synthesis of a Transmission With Intersecting Axes for Rectifying and Reducing a Periodic Speed: A Preliminary Study
Authors: Teng ChinPun , Angeles Jorge , Khader Khaled
Published: February 2021

In power-transmission tasks, the mechanical designer faces sometimes the problem of transmitting a constant angular velocity from a shaft at the output of a motor to another shaft connected to the load. When the first shaft is connected to the rotor of the motor via a gear box directly, and the motor is supplied with an effective speed control system, then the problem of power transmission can be readily solved using a spur-gear train if the shafts are parallel; a bevel-gear train if the two shafts intersect; and a gear train with skew axes if the shafts are neither parallel nor intersecting. However, instances occur in practice whereby the rotor of the motor is connected to a speed reducer that does not preserve the constancy of the motor speed, e.g., when a sprocket-chain transmission is used. In these cases, the input speed is not constant, but periodic. This paper focuses on the design of a transmission mechanism that serves to rectify the periodic speed of an input shaft to deliver a constant speed to the load. Moreover, in doing this, we show that it is possible to reduce the speed delivered by the motor as well. The problem of power transmission between parallel axes was reported in an earlier paper. Here, we report work on the corresponding problem when the shafts intersect. In the two cases, a transmission based on cams is synthesised, this paper reporting on a design based on spherical cams.
Position Analysis and Higher-Order Synthesis of the Swinging-Block Mechanism
Authors: Benedetto Augusto Di , Pennestrì Ettore
Published: February 2021

Algorithms for graphical analysis and kinematic synthesis of the path generator swinging-block mechanism are proposed in this paper. In particular, through a blending of optimization procedures and higher-curvature properties of infinitesimal rigid motions, it is shown how such a mechanism may approximate symmetric continuous curves with up to two sets of four infinitesimally separated precision points. Thus the generated path has eight precision points in common with the ideal curve.
A New Class of Linkage With Synthesis Method for Exact Dwell Motion at 1-2 Limit Positions of Output Link
Authors: Zhang W. J.
Published: February 2021

Occasions still exist for a designer to select a purely mechanical means to realize some special motion types, such as exact dwell at limit positions of the output link. This happens particularly when the design emphasis is placed on highly reliability, high operation speed and low cost. In this paper, a new principle and synthesis method to develop a class of linkages which enable a relatively long exact dwell at 1-2 limit positions of output link are presented. It will be shown that with this new class of linkages, a longer exact dwell can be realized in comparison with those existing classes of linkages including cam mechanisms. Furthermore, a spatial input and output motion can be realized. Application of such a kind of linkage has been found in a package packing machine.
The Optimum Quality Index for the Stability of In-Parallel Planar Platform Devices
Authors: Lee Jaehoon , Duffy Joseph , Keler Max
Published: February 2021

The paper investigates primarily the geometrical meaning of the determinant of the Jacobian (det j) of the three connector lines of a planar in-parallel platform device using reciprocity. A remarkably simple result is deduced : The maximum value of det j namely, det jm is simply one-half of the sum of the lengths of the sides of the moving triangular platform. Further, this result is shown to be independent of the location of the fixed pivots in the base.

A dimensionless ratio λ = |det j| / det jm is defined as the quality index (0 ≤ λ ≤ 1) and it is proposed here to use it to measure “closeness” to a singularity.

An example which determines the optimal design by comparing different shaped moving platforms having the same det jm is given and demonstrates that the optimal shape is in fact an equilateral triangle.
Dynamic Modeling of Parallel Manipulators
Authors: Baiges Ivan J. , Duffy Joseph
Published: February 2021

The dynamic response is an important consideration when designing and controlling manipulators. This dynamic response can be better understood with the explicit equations of motion.

This paper presents the derivation of the explicit equations of motion for a parallel manipulator using Kane’s Method. These equations illustrate the high degree of coupling existing in this type of manipulator.

A simulation program is developed with the equations of motion and used for the inverse dynamic analysis of the system. The results of the tests indicate that the most important coupling effect is caused by gravity.
Force Distribution Characteristics of Actively Reconfigurable Wheeled Vehicle Systems
Authors: Sreenivasan S. V. , Nanua P.
Published: February 2021

This paper addresses the force distribution issues associated with redundantly actuated wheeled vehicles that are suited for operation on uneven terrain. Basic results relating to the partitioning of motion and force variables in these mechanisms are developed. The redundant actuation scheme allows for the control of force distribution in the system, in addition to motion control. The unique kinematic characteristics of wheeled systems, that makes these vehicles ‘singular’ on even terrain, and ‘near-singular’ on uneven terrain; and the presence of ‘kinematic slipping’ when these vehicles move on uneven terrain make their force distribution mathematics distinct from other systems considered in the literature. In a singular configuration, it is shown here that these active wheeled vehicles possess only a partial control over their internal force distribution. A procedure to partition the ‘force space’ into controllable and uncontrollable spaces is provided based on a geometric approach. Closed-form force space results are included for an actively articulated multi-module system (a generalization of a passive, articulated mobile robot that has been studied extensively in literature).

The force distribution in actively reconfigurable wheeled vehicles is closely related to their rate kinematics. Rate kinematics of these vehicles has been studied in a companion paper [SN96].
On the Existence and Characteristics of Solution Paths at Algorithm Singularities
Authors: O’Neil Kevin A. , Chen Yu-Che , Seng Jiaqing
Published: February 2021

The Extended Jacobian method is a popular approach for controlling a kinematically redundant arm which allows one to resolve redundancy by locally optimizing an objective function and to gain repeatability for a cyclic end effector trajectory. It is a special case of a family of methods called constraint function methods. It has been found that the occurrence of algorithmic singularities can cause severe difficulties and the advantages of the methods such as repeatability might no longer exist. The purpose of this analysis is to study the characteristics of algorithmic singularities, especially ones where only one rank is lost. We establish sufficient conditions for the existence of a joint path at an algorithmic singularity. The phenomenon of branch repeatability is shown to occur at an algorithmic singularity. We also show that the extended Jacobian method cannot successfully optimize the objective function beyond the singularity without loss of continuity of the joint derivative. Simple examples are given to demonstrate the use of our theoretical results.
The Effects of Actuation Schemes on the Kinematic Performance of Manipulators
Authors: Matone Ricardo , Roth Bernard
Published: February 2021

This paper is concerned with the effects of actuation schemes on three measures of kinematic performance which depend upon a manipulator’s Jacobian matrix (namely, the minimum singular value, the manipulability, and the condition number.) We begin by presenting a simple framework on how to incorporate actuator location and drive mechanisms in the kinematic model. Then, we redefine the performance measures using the new model. For each measure we derive properties relating its joint space to its actuator space description. Next we demonstrate that the choice of actuation scheme influences the size, shape, and direction of the velocity ellipsoid of the end-effector. Finally, we employ the above concepts in the design of a 2R planar mechanical arm. Its transmission ratios and drive mechanisms are selected in order to obtain good kinematic characteristics. We show that the choice of actuation scheme can be used to improve kinematic performance.
The Problem of Scheduling Parallel Computations of Multibody Dynamic Analysis Is NP-Hard
Authors: Liu Jin-Fan , Abdel-Malek Karim A.
Published: February 2021

A formulation of a graph problem for scheduling parallel computations of multibody dynamic analysis is presented. The complexity of scheduling parallel computations for a multibody dynamic analysis is studied. The problem of finding a shortest critical branch spanning tree is described and transformed to a minimum radius spanning tree, which is solved by an algorithm of polynomial complexity. The problems of shortest critical branch minimum weight spanning tree (SCBMWST) and the minimum weight shortest critical branch spanning tree (MWSCBST) are also presented. Both problems are shown to be NP-hard by proving that the bounded critical branch bounded weight spanning tree (BCBBWST) problem is NP-complete. It is also shown that the minimum computational cost spanning tree (MCCST) is at least as hard as SCBMWST or MWSCBST problems, hence itself an NP-hard problem. A heuristic approach to solving these problems is developed and implemented, and simulation results are discussed.
A Parallel Manipulator With Only Translational Degrees of Freedom
Authors: Tsai Lung-Wen , Stamper Richard
Published: February 2021

This paper presents a novel three degree of freedom parallel manipulator that employs only revolute joints and constrains the manipulator output to translational motion. Closed-form solutions are developed for both the inverse and forward kinematics. It is shown that the inverse kinematics problem has up to four real solutions, and the forward kinematics problem has up to 16 real solutions.
The Kinematics of Active Surfaces: Hyper-Redundant In-Parallel Manipulators
Authors: Smith David R. , Parziale Peter C.
Published: February 2021

Active surfaces are introduced, defined, and modeled as a cooperating set of parallel manipulators. In this context, active surfaces may be viewed as a means of approximating complex shapes or as hyper-redundant in-parallel force manipulators for modal vibration control. Such surfaces may be employed to correct for support structure deformations or vibrations, as well as to achieve other shape dependent performance requirements. As a result of these features, active surfaces have applications in many types of intelligent structures, such as telescopes, communications antennas, bridges, and airfoils. The paper provides an overview of the kinematics of active surfaces. Additionally, it outlines the vibration control problem, and demonstrates how active surfaces can be employed as a modal force manipulator.
Follow-the-Leader Control for the Payload Inspection and Processing System
Authors: Williams Robert L. , Tamasi Gabor
Published: February 2021

This paper presents a follow-the-leader algorithm for control of the Payload Inspection and Processing System (PIPS) at NASA Kennedy Space Center. PIPS is an automated system, programmed off-line for inspection of Space Shuttle payloads after integration and prior to launch. PIPS features a hyper-redundant 18-dof serpentine truss manipulator capable of snake-like motions to avoid obstacles. Given an obstacle-free trajectory for the manipulator tip, the follow-the-leader algorithm ensures whole-arm collision avoidance by forcing ensuing links to follow the same trajectory. This paper summarizes modular development, implementation, testing, and graphical demonstration of the algorithm for prototype PIPS hardware.
Design of a Cleaning and Homogenization Robot for Large Oil Storage Tanks
Authors: Qin Y. , Rastegar J. , Khorrami F.
Published: February 2021

A number of methods are currently employed for cleaning and inspection of large fuel storage tanks. All of these methods require that the tank be first taken out of service, emptied, the present sludge material removed, vented, and cleaned before the inspection process is undertaken. This process is very time consuming, laborious and costly. In addition, there is a great safety concern for people that have to operate the machinery inside the tank. In this paper, the design of a novel robotic system for cleaning large crude and # 6 oil storage tanks through regular homogenization that also prepares the tank surfaces and weld line for in-situ inspection is presented. The developed system is shown to not only reduce the direct and indirect cost of fuel tank cleaning and inspection, but also greatly reduce the amount of solid waste that has to be disposed of at high cost and with potentially high adverse environmental impact. This design solves most of the problems associated with the presently available telerobotic systems for similar operations since it makes it possible for the operator to be in constant visual contact with the robot operating within the tank. This novel design also greatly reduces the logistics problems related to the tether line and its handling within the tank and its entanglement. A prototype of this system is under construction.