bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of a Balanced Breech System for the M1A1 Main Gun System Using Finite Element Techniques
Authors: Hopkins David A. , Wilkerson Stephen A.
Published: March 2021

A series of experiments were recently conducted in an attempt to reduce the dynamic motions of the M256 gun system during firing. Data collected during these experiments included the motion of the gun tube and breech mechanism for both the standard (unbalanced) configuration and a modified system in which mass was added such that the breech center of gravity (CG) was coincident with the gun tube centerline. The results indicated a noticeable change in the dynamic motions between these two configurations. Prior experiments indicated that the unbalanced breech drops several tenths of a millimeter during the firing cycle. Also, the gun tube whipping motion, which is induced by the powder pressure couple, vibrates the gun in a similar fashion regardless of ammunition type. Furthermore, the gun tube shape at shot exit always resembles a distorted sine wave. This behavior was noted for both heat and kinetic energy (KE) munitions in previous unbalanced breech tests conducted with the M256 gun. However, when the breech is balanced, the dynamics of the entire system change in both shape and magnitude of displacement.

This report attempts to explain the results of the tests performed. This was accomplished using a three-dimensional (3-D), transient, finite element (FE) model of the entire system, which included breech, gun tube, trunnion mount, recoil, and projectile. Results from these calculations provide an explanation of the observed behavior of the system. Insight acquired about the nature of the system’s behavior was then used to propose several simple improvements to the M256 gun system which can be applied to gun systems in general. Implementation of these changes should decrease the shot-to-shot variability associated with gun accuracy.
Dynamic Response of Composites to Impact Loading
Authors: Cheng Wing L.
Published: March 2021

This paper shares some of our experiences in the use of a supercomputer to facilitate the analysis of impact process in thick composites, and also in the benefits of color animation of the results on a Macintosh computer. An explicit nonlinear finite element program has been ported to the CRAY-2 Supercomputer at the National Center for Supercomputing Applications (NCSA) of the University of Illinois at Urbana-Champaign (UIUC). The calculations were carried out using an impact model developed for high velocity impact of fiber-reinforced layered composites. The model is built on a continuum approach and includes a basic orthotopic constitutive material behavior. It has been validated to some degree with ballistic tests and therefore can provide a reasonable estimate of the effectiveness of a fiber-reinforced layered composite construction as a protective system. A computer program was developed to convert the results of the analysis for hundreds of time steps to 8-bit raster images. The images stored in NCSA’s Hierarchical Data Format (HDF) were then transferred to a color Macintosh workstation and animated using graphics tools developed at NCSA. The same set of images were also directly recorded on a video tape and displayed on any standard VCR. This animation capability allowed us to see important detailed information about various quantities like deformation, pressure, stress, etc., which cannot be easily observed by any other means.
Adiabatic Flame Temperature and Product Composition for Lean Combustion of Hydrogen-Methane Combination
Authors: Dülger Zafer
Published: March 2021

Adiabatic combustion of methane (natural gas)-hydrogen mixtures is analyzed The adiabatic flame temperature and products composition (especially NOx and CO2 concentrations) variation with excess air (fuel-air equivalence ratio), hydrogen enrichment of methane, and reactant temperature is determined It is shown that reductions in NOx and CO2 emissions are possible with the extended lean limit of combustion of methane associated with hydrogen enrichment CO2 concentrations are also reduced with hydrogen enrichment, reductions being dependent upon the degree of enrichment.
Process Improvement Using Design by Experiments
Authors: Li Hsien-chen , Lin Fuyau
Published: March 2021

This paper present an approach to apply Design by Experiments for process improvement with the objectives to minimize cost and shorten investigation time. A case study of PCB (Printed Circuit Board) manufacturing process is chosen to illustrate this approach. A Fractional Factorial Design by Experiment was performed due to the constraints of the time, budget, and resources.
A Self-Organizing Fuzzy Controller Using Neural Networks
Authors: Li Wei , Wu Zuowei
Published: March 2021

This paper presents a self-organizing fuzzy logic control scheme based on neural networks, which consists of a traditional fuzzy logic (FL) controller and a conventional derivative (D) controller. Since membership functions regarding change-in-error ė represent the feedback of velocity they strongly affect transient behaviors of a system. In the proposed scheme, therefore, such membership functions are parameterized by the use of the cubic splines. Then, neural networks are adopted to optimize them in self-organizing process. To demonstrate the effectiveness of the proposed method, we report a number of simulation results involving both step and tracking control of a nonlinear plant.
Sensor-Based Robot Navigation in Uncertain Environments Using Fuzzy Logic
Authors: Li Wei , He Kezhong
Published: March 2021

This paper presents a new method for sensor-based mobile robot navigation in unknown environments using fuzzy logic. The inputs to the fuzzy control scheme consist of a heading angle between the robot and a specified target and distances between the robot and obstacles to the left, front, and right locations. The outputs from the control scheme are commands for the speed control unit of two rear wheels of a mobile robot.

Distances between the robot and obstacles are acquired by an array of ultrasonic sensors. Current coordinates of the robot are measured by a wheel ancoder system. The velocities of the driving wheels are controlled by a motor drive unit.

The main idea of the proposed method is quantitatively to formulate reactive behaviors and efficiently to coordinate their conflicts and competitions by fuzzy sets and fuzzy rules.

Simulation results show that the proposed method can be efficiently applied to robot navigation in complex and uncertain environments based on sensors.
Computer Simulations for Design and Optimization of a Fuzzy Control System
Authors: Edwards Dean B. , Canning John R. , de Sam Lazaro Anthony
Published: March 2021

The use of fuzzy logic in control systems is becoming increasingly popular as a method of handling non-linear control problems. The design of fuzzy systems is generally undertaken using intuition and a trial-and-error approach for tuning. A system so developed may be less than optimum as no accepted evaluation norms are available. In this paper a generic method to design and to optimize a fuzzy control system is developed. The results of computer simulations of a system constructed using this technique are submitted and discussed. The experimental verification of the method is presented.
Effective Integration of Computer Programming in Engineering Education
Authors: Untener Joseph A.
Published: March 2021

Computer programming assignments in technical courses often involve the instructor choosing a given problem from the text and requiring the students to write a program to solve that problem. While this approach provides the student with an opportunity to improve some skills, there may be more effective approaches.

This paper discusses an approach that initially gives the student only a narrative describing a company’s set of circumstances. The class then discusses how the situation might be improved using computer applications. Through discussion, a set of parameters for the application is developed. By the end of the discussion, the application that will help the company has been defined by the students. The required features and the desirable features are identified. The outcome of the discussion becomes the computer assignment.

When used in a fluid mechanics course by the author, the approach yielded many benefits. The students a) had personal ownership in the assignment, b) were able to see the true power of the computer in automating a repetitive process, c) developed logic and critical thinking abilities, and d) solved a problem similar to ones they will face upon graduation.
Optimal Tolerancing: The Link Between Design and Manufacturing Productivity
Authors: Iannuzzi Mark , Sandgren Eric
Published: March 2021

A computational design tool is presented which permits the optimal allocation of tolerances for mechanical and electrical components and assemblies. The basic approach involves the coupling of a nontraditional optimization method with a Monte Carlo based tolerance analysis. The objective is to determine the tolerance range value to assign to each nominal dimension which minimizes the production cost of the component or assembly while simultaneously meeting all critical dimensional and functional constraints imposed upon the design. A discretization of possible tolerance range values is performed and a global search is conducted by a genetic algorithm. Both the fine and course grain performance of the combined algorithm is demonstrated on a series of test problems ranging from a simple assembly of blocks to several real mechanical design problems. Solutions generated on problems taken from the literature indicate superior performance to existing techniques. Extensions which would allow for a complete optimal dimensional management environment are examined.
Including Imprecision in Engineering Design Calculations
Authors: Law William S. , Antonsson Erik K.
Published: March 2021

The Imprecise Design Tool (IDT) presented in this paper is a working computer implementation of the method of imprecision, a formal theory that represents preferences among design alternatives. An aircraft engine design example indicates how the IDT may be applied to support engineering design decisions, using the Engine Development Cost Estimator provided by General Electric Aircraft Engines, Cincinnati, Ohio.
The Roles of Features and Abstraction in Mechanical Design
Authors: Taylor LeRoy E. , Henderson Mark R.
Published: March 2021

This paper describes the roles of features and abstraction mechanisms in the mechanical design process, mechanical designs, and product models of mechanical designs. It also describes the relationship between functions and features in mechanical design. It is our experience that many research efforts exist in the areas of design and product modeling and, further, that these efforts must be cataloged and compared. To this end, this paper culminates with the presentation of a multi-dimensional abstraction space which provides a unique framework for (a) comparing mechanical engineering design research efforts, (b) relating conceptual objects used in the life cycle of mechanical products, and (c) defining a product modeling space.
Testing Design Methodology Through Task Performance
Authors: Rückert Carsten , Springer Johannes
Published: March 2021

While design methodology is well accepted at universities, it is rarely used for industrial design work. This rift is caused by widespread skepticism regarding methodology in the industry. At the Technical University of Berlin, 13 mechanical engineers performed a design task in a laboratory experiment. The study has provided some results that can help to dissipate criticism of methodology. Furthermore, specifications for improving methods have been derived.
Analyzing Inter and Intra Group Information Exchanges in Conceptual Collaborative Design
Authors: Waldron Manjula B. , Brooks Regina L.
Published: March 2021

This paper reports preliminary results from a technique used to study inter and intra group information exchanges which occur in the conceptual stages of collaborative group design. In the early stages of conceptual design, there is little information to guide the designers and they find themselves groping to find pertinent information which may help them. In collaborative group design the members are able to pool in both their knowledge as well as knowlwdge from other groups. Currently there are no techniques, which exist, to help track this group information exchange. In this paper, we use the sense-making theory to guide us in assessing the information needs of the designers engaged in group collaborative design. In this study, the sense-making theory is described and adapted for applications in the engineering design domain. The analysis technique is a two step process. First the records are transcribed and labeled and then interpreted. The technique allows one to obtain a chronological map of the information seeking, helps obtained, and the decisions made. Results from the first design session show that during the early phases of group design, the most needs arose in establishing the knowledge base and in identifying the design process. There was a strong need for inter and intra group information exchange.
Critical Thinking: Evolution of a Freshman Graphics Course
Authors: Sanchez Lilia A. , Hight Timothy K. , Gainen Joanne
Published: March 2021

We have redefined the goals of the Freshman course in Engineering Graphics at Santa Clara University to emphasize graphic communication skills as a vehicle to introduce the design process and a design experience. Integration of the critical thinking component into the course has led to our own iterative, interactive design process of a more effective teaching methodology.
Determination of the Interference Distance Between Two Objects Using Optimization Techniques
Authors: Nahon Meyer
Published: March 2021

The determination of the interference distance between objects is a problem encountered in the off-line simulation of robotic systems. It is similar to the problem of finding the minimum separation distance between two bodies — a problem which, at present, is commonly solved using optimization techniques. This paper presents an analogous optimization formulation for the quick and accurate determination of the interference distance between two interfering objects. The optimization problem consists of finding the maximum amount by which the boundaries of two interfering object can be moved back while still maintaining a non-empty interference volume. Since the approach used is similar to that used in the minimum separation problem, a single algorithm has been implemented which, given the position and orientation of two objects, will return the separation or interference distance between the objects, as appropriate.
Path Planning for Spheres in Three Dimensional Environments With Low Interference Index
Authors: Storti Duane W. , Dutta Debasish
Published: March 2021

We consider the path planning problem for a spherical object moving through a three-dimensional environment composed of spherical obstacles. Given a starting point and a terminal or target point, we wish to determine a collision free path from start to target for the moving sphere. We define an interference index to count the number of configuration space obstacles whose surfaces interfere simultaneously. In this paper, we present algorithms for navigating the sphere when the interference index is ≤ 2. While a global calculation is necessary to characterize the environment as a whole, only local knowledge is needed for path construction.
An Octree Method for Interference Detection in Computer Aided 3-D Packing
Authors: Dai Zuo , Cha Jianzhong
Published: March 2021

In simulating the three dimensional packing process with arbitrary shaped objects, the task of detecting interference between objects is important and very difficult. This paper, representing the three dimensional packing space and objects with an octree, presents an effective interference detection algorithm, which can overcome the performance shortcomings that the conventional methods have in terms of real-time response, computer memory and computational accuracy. By recording the distribution status of packing space in the “bits” of short integers, the data space can be compressed to 1/16 of that used by conventional algorithms.
Robust Concurrent Concept Selection and System Synthesis
Authors: Chen Wei , Allen Janet K. , Mistree Farrokh
Published: March 2021

In this paper, we introduce a concurrent approach to preliminary system design by using a modification of Taguchi’s method of robust design. It is possible to model interactions among component concept selections and synthesis of system variables. This approach also can improve computational efficiency and provide more design knowledge for the conceptual design of complex engineering systems. This technique is effective in dealing with both discrete and continuous variables simultaneously in design. We illustrate our approach by the preliminary design of a solar powered irrigation system. The selections of critical component concepts are integrated with the determination of system variables, i.e., the thermodynamic operating parameters.
Concurrent Designing of Airframes: State of the Art and Trends
Authors: Petiau Christian
Published: March 2021

We will first recall that the organization of airframe designing stands in direct relation to the performance capabilities of available tools, which is, in fact, what determines the number and the nature of project iterations.

We then present and analyze an organization type which can nowadays be recommended in view of the currently available CAD, computation and mathematical optimization means.

This leads to a first design which is followed by experimental verification, with a key role for flight tests. The final design is checked with the aid of computation models that have been calibrated with the results of the performed tests.

We will then examine new tools, since they are factors in the future evolution of the design methodology, including:

• availability of the “design history”, as a set of all data of the whole process,

• structure optimization with parametric CAD and multidisciplinary optimization

• “feature” modeling

• enhancement of the computation methods

As a conclusion, we show that significant gains in terms of productivity and quality can be expected from these new products, both at design and at production level. What remains, however, to be found, are the most appropriate concurrent engineering organizations that are best suited to these new tools.
Monotonicity and Goal Interaction Diagrams for the Compromise Decision Support Problem
Authors: Smith Warren F. , Mistree Farrokh
Published: March 2021

Our approach in this paper is an introspective one with respect to modeling. Rather than examining what can be done with a model and how it can be built up or synthesized, we focus on the mathematical characteristics and how a model might be broken down or analyzed. Firstly, using monotonicity principles, this culminates in the identification of the nonlinear constraint and goal functionality and variable monotonicity, and secondly, in the development of the Goal Interaction Diagram. As various scenarios are examined, this information leads to improved efficiency and effectiveness within the design process through enhanced understanding. The case study we use to illustrate our approach deals with a real world example, namely, the preliminary design of a naval frigate. A working knowledge of naval architecture, however, is not required to understand the concepts being discussed.
Parametric Volume Models for Interactive Three-Dimensional Grid Generation
Authors: Mokhtar Jawad D. , Oliver James H.
Published: March 2021

A method based on non-uniform rational B-spline (NURBS) curve, surface, and solid technology is presented for interactive grid generation of three-dimensional flow fields encountered in turbomachinery applications. The method allows construction of several types of multi-block grids including H-, O-, and C-grids for two-dimensional grids, and strict H-grids for three-dimensional grid generation. Automated two-dimensional block construction is facilitated via a traversal method that searches four-sided regions in the initial block structure. A NURBS surface is then constructed on each block by transfinite interpolation of the boundary curves themselves, and various point distribution options may be applied. Three-dimensional grid generation is an extension of the two-dimensional procedure. Tri-parametric hyperpatches (NURBS solids) are constructed from the two-dimensional block surfaces and grids may be generated via several point distribution functions. This method exploits existing geometric design data via Initial Graphics Exchange Specification (IGES) input of NURBS-based component geometry. It provides an efficient and robust method for complex grid generation to support a variety of analysis functions. Several example applications are presented to demonstrate the capabilities of the technique.
Impact Analysis of Plates Using Quasi-Static Approach
Authors: Shivaswamy Shashishekar , Li Jianmin , Lankarani Hamid M.
Published: March 2021

Impact calculations suffer from several practical limitations which limit their application to establishing the approximate magnitude of the various phenomena involved. The transient force deformation response of a body subjected to impact can be explained accurately using stress wave propagation theory. As this approach is very complicated, a simpler quasi-static approach with non-linear force deformation Hertz relations can be employed for impact analysis. However, these relations can not explain the energy absorption and permanent deformations encountered during the impact. This necessitates independent non-linear force-deformation relations for compression and restitution phases of impact.

In the present paper, impact tests conducted on Aluminum and Steel plates have been reported. The impact response of the system was compared with the various theoretical quasi-static force models. Considering the assumptions made in the quasi-static force models, the experimental results matched very well with the theoretical results. Non-linear force-deformation model with independent relations for compression and restitution phases was found to be the best approach to analyze impact problems. The value of the index in the non-linear force-deformation relations was found to be approximately 1.71 and 1.78 for Aluminum and Steel respectively. The values of impact parameters for a given material were found to depend on impact velocity.
Evaluation of Factors Affecting the Simulation of Structural Vibrations in Rolling Bearings
Authors: Mehra Kapil , Datta Jayanta , Farhang Kambiz
Published: March 2021

An analytical model is developed for studying in-plane structural vibrations in rolling element bearings. A lumped parameter approach is employed in developing the model. The mass and moment of inertia of the components comprising the bearing are lumped at their respective centers of mass. The localized stiffnesses due to contact deformation phenomenon are treated as nonlinear springs. The variable spring rates are obtained by application of Hertz equation for elastic contact deformation.

Effects of preload, ball rotational speed, and damping are studied using the formulation. An interesting observation is made as to the influence of preload. It is found that in the presence of preload, irrespective of the load magnitude, contact is maintained with both the inner and the outer races. Hence, responses obtained with and without the check for ball/inner race and ball/outer race interferences are identical. In addition, no appreciable change is observed in the responses when the preload value is varied from 10 N to 1N. At high speed of operation, the balls are found to maintain contact with the outer ring, whereas intermittent contact with the inner ring occurs for brief periods of time. Introduction of lubricant is found to dampen the oscillations considerably.
A Simplified Model for Structural Vibrations in Ball Bearings
Authors: Farhang Kambiz , Mehra Kapil , Datta Jayanta
Published: March 2021

More often than not, in studies involving dynamics and vibration of rotor systems, the bearings within a rotor system are treated as linear components. However, it is well understood that bearing systems are nonlinear due to both their geometrical properties and Hertzian contact between their components. This paper develops a linear formulation to approximate the vibration behavior of rolling bearings. A study of the approximation in the linear representation for rolling bearings is presented in which the effects of preload, lubricant viscosity and outer ring mass on the accuracy of the linear representation are determined.

The equations of motion governing the vibrations of rolling element bearing are found to be a set of second-order, nonlinear ordinary differential equations with position periodic coefficients. These equations are linearized about nominal values of the position vectors of the rolling element and the outer ring center. The linearized equations of motion are solved to obtain the small perturbations (displacements) from the nominal positions.

The results show that the linear model representation is applicable for bearings with preload. Existence of damping and/or greater outer ring mass enhance the approximation provided by the linear model. Most importantly, the linear representation provides a conservative estimate of the rolling element motion and very accurate estimate of the outer ring motion.
Structural Shape Optimization Wth Error Control
Authors: Duysinx Pierre , Zhang WeiHong , Zhong HaiGuang , Beckers Pierre , Fleury Claude
Published: March 2021

A robust and automatic shape optimization procedure is presented in this paper, which incorporates recent developments in the field of computer-aided design (CAD) of mechanical structures, such as geometric modelling, automatic selection of independent design variables, sensitivity analysis using reliable mesh perturbation schemes, error estimation and adaptive mesh refinement. A numerical example is given to show the efficiency of the procedure.
Generation of Conceptual Design for Structural Shapes and Functional Elements of Machine Systems Having no Preconceptions Concerning the Design
Authors: Yoshimura Masataka , Nose Kohji
Published: March 2021

This paper presents a methodology for generating conceptual designs of structural shapes and functional elements of machine systems from initial conditions having no preconceived information. Firstly, a feasible design region initially containing nothing is defined. The whole feasible region which is uniformly filled up with finite elements having an extremely low rigidity is here assumed to be a region containing nothing. Then, a seed element grows into a whole structural system in the feasible design region by conducting both the creation of external shapes and the growth of the inner structures. Next, the design method is advanced so that a functional element of a rotational joint is also generated with the structural shapes simultaneously. Finally, the proposed conceptual design method is applied to design of industrial robots.
Derivation of Multiple Assembly Sequences From Exploded Views
Authors: Rivero Andres , Kroll Ehud
Published: March 2021

The original exploded view method of assembly planning (Mohammad and Kroll, 1993b) attempts to automatically generate the “simplest” assembly plan for a product. Criteria for optimal assembly sequences, however, are sometimes unclear and dependent on specific circumstances. It may therefore be advantageous to present the designer with more than one solution to the assembly planning problem, or allow him or her to select the appropriate criteria. This paper introduces an extension to the original method, where all possible assembly sequences are generated. This completely automatic capability is demonstrated by manually applying the method to a simple example and then comparing the results to those generated by the algorithmic procedure of the C. S. Draper Lab.
A Hybrid Approach of Heuristic and Neural Network for Packing Problems
Authors: Dai Zuo , Cha Jianzhong
Published: March 2021

Artificial Neural Networks, particularly the Hopfield-Tank network, have been effectively applied to the solution of a variety of tasks formulated as large scale combinatorial optimization problems, such as Travelling Salesman Problem and N Queens Problem [1].

The problem of optimally packing a set of geometries into a space with finite dimensions arises frequently in many applications and is far difficult than general NP-complete problems listed in [2]. Until now within accepted time limit, it can only be solved with heuristic methods for very simple cases (e.g. 2D layout).

In this paper we propose a heuristic-based Hopfield neural network designed to solve the rectangular packing problems in two dimensions, which is still NP-complete [3]. By comparing the adequacy and efficiency of the results with that obtained by several other exact and heuristic approaches, it has been concluded that the proposed method has great potential in solving 2D packing problems.
Genetic Algorithm-Based Structural Topology Design With Compliance and Manufacturability Considerations
Authors: Chapman Colin D. , Jakiela Mark J.
Published: March 2021

The genetic algorithm, a search and optimization technique based on the theory of natural selection, is applied to structural topology design problems with compliance and manufacturability considerations. After describing the genetic algorithm and reviewing previous research in structural topology design, we detail the chromosome-to-design representation which enables the genetic algorithm to perform structural topology optimization. Extending our prior investigations, this article details the use of our genetic algorithm-based technique to minimize a structure’s compliance, subject to a maximum volume constraint. The resulting structure is then directly compared with a solution obtained using a mathematical programming technique and material homogenization methods. We also demonstrate how our technique can generate structures which combine high stiffness-to-weight ratio with high manufacturability. After a brief discussion of our findings, we describe potential future work in genetic algorithm-based structural topology design.
Practical Experience With and Extensions to the SAM Algorithm for Structural Optimization
Authors: Stander Nielen , Snyman J. A.
Published: March 2021

This paper deals with a second order successive approximation optimization method SAM, which is based on the authors’ recently published feasible descent cone algorithm SSOPT. In particular, the paper reviews the success that has been achieved in the practical application of SAM to structural optimization problems, both with reference to results already published and new results, presented here. In addition extensions to the underlying feasible descent cone method is proposed with the view to improving the generality and efficiency of the embracing SAM algorithm.
Parallelization of Evolution Strategy on a Workstation-Cluster and its Application to Discrete Structural Optimization
Authors: Cai Jianbo , Thierauf Georg
Published: March 2021

Evolution strategies (ESs) imitate biological evolution and have two characteristics that differ from other conventional optimization algorithms: (a) ESs use randomized operators instead of the usual deterministic ones; (b) instead of a single design point, the ESs work simultaneously with a population of design points in the space of variables. The second characteristic allows for an implementation in a parallel computing environment. In this paper the application of ESs for the solution of discrete optimization problems and its parallelization are described.
A Design Methodology for Tracked Vehicles Using Experimentally Identified Modal Parameters and the Finite Element Method
Authors: Sarwar M. K. , Shabana A. A. , Nakanishi Toshikazu
Published: March 2021

The objective of this study is to develop a design procedure that integrates multibody techniques, the finite element method, and experimental modal analysis techniques. Multibody techniques and the finite element method are first used to develop and numerically test the performance of the proposed design. Based on this computer analysis, a prototype model can be built. The vibration modal parameters of this model can be determined experimentally and used with general purpose multibody computer programs to evaluate the performance of the design. The obtained numerical results can be compared with the results obtained previously using multibody techniques and the finite element method. Adjustments can then be made in the finite element description in order to obtain a more realistic model that compares well with the experimental data. Using the more realistic finite element model, design modifications can be made in order to improve the performance of the design model. The use of the design methodology proposed in this paper is demonstrated using a flexible tracked vehicle model that consists of fifty four interconnected bodies. In this model, the nonlinear contact forces that describe the interaction between the track links and the vehicle components and the ground are developed. The nonlinear dynamic equations of the vehicle are developed in terms of a coupled set of reference and chassis elastic modal coordinates. The flexibility of the chassis of the tracked vehicle is described using the finite element method and experimentally identified modal parameters. The results obtained using the finite element model are compared with the results obtained using experimentally identified modal parameters.
Effect of Modeling for Automatic Design on Lightweight Structural Shape
Authors: Itou Motomichi , Ohkouchi Teiichi
Published: March 2021

This paper discusses importance of modeling for automatic design of lightweight structural shape, using a successive approximation method to modify the shape of the structure which is constructed by discrete elements. Four modeling parameters, (1) the number of discrete elements, (2) the magnitude of loading force, (3) the displacement constraint condition and (4) the restriction of design domain are investigated and it is turned out that the modeling causes large effects to topology, volume and rigidity of the structure which is calculated by the shape generation method for lightweight design.
Generating Swept Volumes With Instantaneous Screw Axes
Authors: Hu Zeng-Jia , Ling Zhi-Kui
Published: March 2021

The instantaneous screw axis is used in the generation of the swept volume of a moving object. The envelope theory is used to determine the boundary surfaces of the swept volume. Specifically, the envelope surfaces generated by a plane polygon, cylindrical and spherical surfaces are presented. Furthermore, the ruled surfaces generated by edges of the moving object are discussed.
A Dual Iterative Method for Displacement Analysis of Spatial Mechanisms
Authors: Thompson Sean , Cheng Harry H.
Published: March 2021

A dual iterative method for displacement analysis of a spatial mechanism is presented in this paper. The algorithm and formulation based upon 3 × 3 dual transformation matrices are succinct. They can be easily implemented in the CH programming language. The algorithm has been numerically verified by dual iterative displacement analysis of an RCCC four-link spatial mechanism.
A Method for Type Synthesis of Mechanisms Using Phase Diagrams
Authors: Lei Sio-Hou , Tsai Ying-Chien
Published: March 2021

A method for synthesizing the types of spatial as well as planar mechanisms is expressed in this paper by using the concept of phase diagram in metallurgy. The concept represented as a type synthesis technique is applied to (a) planar mechanisms with n degrees of freedom and simple loop, (b) spatial mechanisms with single degree of freedom and simple loop, to enumerate all the possible mechanisms with physically realizable kinematic pairs. Based on the technique described, a set of new reciprocating mechanisms is generated as a practical application.
Methodology for the Design of Compliant Mechanisms Employing Type Synthesis Techniques With Example
Authors: Murphy Morgan D. , Midha Ashok , Howell Larry L.
Published: March 2021

Type synthesis of rigid-link mechanisms provides a means to determine mechanism topologies before considering link dimensions. The formulation of design procedures for rigid-body mechanisms has benefited from the application of type synthesis techniques. Therefore, type synthesis is seen as a useful tool in the development of design procedures for compliant mechanisms as well. The focus of this paper is to propose and exemplify a design procedure for compliant mechanisms that employs the type synthesis techniques developed for compliant mechanisms.
Analysis and Synthesis of Overconstrained Mechanism
Authors: Mavroidis Constantinos , Roth Bernard
Published: March 2021

This paper presents a new systematic method for dealing with overconstrained mechanisms, and describes how the method was used to discover new overconstrained mechanisms and correct errors in several previously published overconstraint conditions. With this one method we are able to verify all previously known overconstrained mechanisms. In addition, this method yields the input-output equations of any single-loop overconstrained mechanism. For all new and corrected overconstrained mechanisms, numerical examples of input-output curves are presented.
Rectified Synthesis of Six-Bar Mechanisms With Well Defined Transmission Angles for Four-Position Motion Generation
Authors: Bawab S. , Kinzel G. L. , Waldron Kenneth J.
Published: March 2021

This paper describes a rectified synthesis method where a rigid body of a six-bar linkage with well-defined transmission angles is guided to pass through four precision positions. The procedure includes the elimination of circuit, branch, and order defects. This is achieved by decomposing the six-bar mechanism into groups of vector pairs called dyads and groups of three vectors called triads which are rectified using the algebraic method of synthesis. The procedure has been implemented for a Watt I crank-driven six-bar linkage in the interactive synthesis package RECSYN.
Recent Enhancements to the LINCAGES-6 Synthesis Package, Including Circuit Rectification
Authors: Nelson Lori , Erdman Arthur G.
Published: March 2021

LINCAGES-6 is a computer program that synthesizes four- and six-bar linkages based on Burmester Theory using complex numbers. Recent enhancements to the user interface and the added ability to rectify certain Burmester curves for the circuit problem have increased the ease of use and allowed the user to discard unworkable solutions at an early stage in the design process.
Computer Aided Synthesis of Adjustable Robotic Mechanisms
Authors: Chuenchom Thatchai , Kota Sridhar
Published: March 2021

Conventional hard automation such as linkage mechanisms or cam-driven mechanisms provide high speed capability at a low cost (using typically one actuator), but fail to provide the flexibility required in many industrial applications. Manufacturers are increasingly turning to multi-axis robots to fulfill flexibility demands. In many cases, however, the flexibility requirements are limited; i.e. a given pick-and-place unit may be required to perform only a handful of different operations. Therefore, the expensive robots are under-utilized. By incorporating flexibility in conventional linkage-type mechanisms, we are developing adjustable robotic mechanisms (ARMs) to serve as a middle ground between hard automation and overly flexible serial-jointed industrial robots.
Displacement Analysis of the R0-2R-2C Spatial Linkage Mechanisms
Authors: Zhou Y. B. , Buchal R. O. , Fenton R. G.
Published: March 2021

Closed form input-output displacement equations are derived for the R0-2R-2C mechanisms using the vector algebraic method. As compared to previous works, the proposed method is characterized by its standardized analysis steps, compact expressions and simplicity.
Notes on Screw Product Operations in the Formulations of Successive Finite Displacements
Authors: Huang Chintien
Published: March 2021

Geometrical interpretations of two line-based formulations of successive finite displacements in terms of screw product operations is discussed. The pitch of the screw product of two unit line vectors is shown to be the ratio of the distance to the tangent of the projected angle between the two lines. Finite twists in Dimentberg’s formulation are interpreted as the screw product of unit line vectors divided by the scalar product of the same unit line vectors. Finite twists in the linear representation are the screw product of unit line vectors divided by the scalar product of the direction-cosine vectors of the same lines.
An Alternative Method for the Numerical Solution of Spatial Linkage-Loop Equations
Authors: Jiyuan Zhang , Shoufan Shen
Published: March 2021

This paper deals with three problems in finding numerical solutions of spatial linkage-loop equations, which have not yet been thoroughly solved. Four means have been adopted in order to solve these problems. An alternative method has been proposed. Compared with present numerical methods, the method suggested by the authors is characterized by a complete theoretical foundation, easy programming, and powerful adaptability. The effectiveness of this method is demonstrated with the kinematic analysis of a general spatial 7H linkage.
Estimation of Critical Damping in Robot Joints and Identification of the Joint for Design With Most Effective Damping Enhancement
Authors: Smaili Ahmad A. , Sannah Muhammad
Published: March 2021

A major hindrance to dynamics and control of flexible robot manipulators is the deficiency of its inherent damping. Damping enhancement, therefore, should result in lower vibration amplitudes, shorter settling times, and improvement of system stability. Since the bulk of robot vibrations is attributed to joint compliance, it is a prudent strategy to design joints with sufficient inherent damping. In this article, a method is proposed to estimate critical damping at each joint and identify the joint that should be targeted for design with sufficient built-in damping. The target joint identification process requires that a n-joint robot system is divided into n-subsystems. Subsystem i includes the compliance of joint i and the inertia of the succeeding links, joint mechanisms, and payload. An equivalent single degree of freedom torsional model is devised and the natural frequency and critical damping is evaluated for each subsystem. The estimated critical damping at the joints are used to determine the elastodynamic response of the entire robot system from a model that includes joint compliance, shear deformation, rotary inertia, and geometric stiffness. The response revealed the following conclusion: The joint of the manipulator that would result in lower amplitudes of vibrations and shorter settling times when designed with sufficient built-in damping is the one that renders a subsystem whose natural frequency is the lowest of all subsystems comprising the robot.
Application of Learning Control Theory to Mechanisms: Part 1 — Inverse Kinematics and Parametric Error Compensation
Authors: Chew M. , Phan M.
Published: March 2021

Fundamental concepts of learning control theory are applied to problems in mechanisms. The theory provides an integrated approach that can simplify the numerical solution of inverse kinematics of mechanisms as well as the practical problem of inverse kinematics in the presence of parametric errors. The procedure makes repeated use of forward kinematics that can be carried out analytically for off-line computation, or experimentally for on-line tuning of mechanisms, to arrive at the correct inverse kinematic solution. With repetitive learning, learning control theory will identify the appropriate input function to a mechanism so that its output will track a given desired output function. The learning process is based on the output error alone, without accurate or explicit knowledge of the physical system, so that the analytical algebraic inverse is avoided. This is achievable even in the presence of geometric nonlinearities as well as parametric errors in mechanisms modeling as long as measurements of the output relative to the given desired output function, are available. A general formalism is presented to explain the applicability of such repetitive learning to mechanism problems. Several examples will illustrate the important benefits of the learning approach using very simple learning rules.
Experimental Verification of the Closed Solution for the Dynamics of a Press Feed Mechanism
Authors: Xu Tao , Lowen Gerard G.
Published: March 2021

An experimental verification of a new linearized two-degree of freedom model of a press feed mechanism, which is presented in a companion paper (Xu and Lowen, 1994), is given. An associated parametric study shows insights pertaining to the relationship between the system and component frequencies and allows the formulation of certain design rules regarding the magnitudes of the coupler and clutch windup angle deflections.
Pressure Angle Characteristics of Radial Cams With Offset Reciprocating Roller Followers
Authors: Suchora Daniel H. , Werner Brian C. , Paine Waid A.
Published: March 2021

The pressure angle characteristics of radial cams with offset reciprocating roller followers are presented. Maximum pressure angle values for simple harmonic, cycloidal, and modified harmonic motion have been plotted on nomograms for both full rise and full return motions. The nomograms enable the designer to compare several tentative designs to arrive at an optimum design quickly and easily. An example is given to demonstrate the use of the nomograms.
A Dynamic Model for Addendum Modified Gear Pair
Authors: Kuang Jao-Hwa , Yu John
Published: March 2021

This investigation presents a dynamic tooth load analysis of spur gear pair with addendum modification. The time varying mesh stiffness and Dowson’s tooth friction model are employed in this dynamic tooth load modeling. The effects of various magnitudes of the addendum modification on the fundamental resonance frequency and dynamic load response of the engaged gear pair are analyzed. A particular emphasis has been placed on the effect of addendum modification on the dynamic load of spur gears.
Steady-State Rigid-Body Dynamic Response of Cam-Follower Mechanisms
Authors: Mahyuddin Andi I. , Midha Ashok
Published: March 2021

The camshaft of a cam-follower mechanism experiences a position-dependent moment due to the force exerted on the cam by the follower, causing the angular speed of the camshaft to fluctuate. In this work, a method to expediently predict the camshaft speed fluctuation is developed. The governing equation of motion is derived assuming that the cam-follower system is an ideal one wherein all members are treated as rigid. An existing closed-form numerical algorithm is used to obtain the steady-state rigid-body dynamic response of a machine system. The solution considers a velocity-dependent moment; specifically, a resisting moment is modeled as a velocity-squared damping. The effects of flywheel size and resisting moment on camshaft speed fluctuation are studied. The results compare favorably with those obtained from transient response using a direct integration scheme. The analytical result also shows excellent agreement with the camshaft speed variation of an experimental cam-follower mechanism. The steady-state rigid-body dynamic response obtained herein also serves as a first approximation to the input camshaft speed variation in the dynamic analysis of flexible cam-follower mechanisms in a subsequent research.