bluuebunny/crossref_metadata_2025 huggingface dataset:
Maximum Frequency Design of Prestressed Symmetric, Cross-Ply Laminates of Hybrid Construction
Authors: Duffy K. J. , Adali S.
Published: April 2021

A symmetric, cross-ply laminate of sandwich hybrid construction is optimally designed with the objective of maximizing the fundamental frequency and the separation between two adjacent frequencies. The laminate, which is subject to an in-plane compressive load, is constructed with inner layers made of a low-stiffness material and outer layers made of a high-stiffness material. Optimal hybridization is achieved by determining the optimal ratio of the thickness of the low-stiffness layers to the overall laminate thickness. Moreover, the fibre orientations of high and low stiffness materials (0° or 90°) are determined optimally noting that the orientations of outer and inner layers affect the maximum frequency values in the case of hybrid laminates although they do not have any effect in the case of non-hybrid laminates. Comparative numerical results are given for graphite/glass hybrid and non-hybrid laminates. The optimal value of the hybridization parameter is found to depend on the level of prestress as well as on the aspect ratio. The optimal thicknesses of layers are shown to be non-unique for certain aspect ratios in the case of non-hybrid laminates of a given staking sequence.
Optimal Three Dimensional Robot Path Planning With Collision Avoidance
Authors: Jain Piyush K. , Manoochehri Souran
Published: April 2021

The study reported in this paper deals with path planning in three-dimensional space using network optimization for robotic manipulators working in the presence of obstacles and workspace singularities. To execute the algorithm, the robot design parameters, the geometry and location of the obstacles, and the initial and goal positions of the desired task are required. As a first step, the manipulator workspace is discretized and points inside forbidden regions formed by obstacles and singularities are excluded. An ellipsoidal searchspace is then selected as a part of the workspace to make the network enumeration and path synthesis more efficient. Based on an allowable deviation angle, path segments axe created to form the connectivity network. A path which is optimal with respect to the manipulator kinematic and dynamic properties is generated as a sequence of intermediate points connecting the initial and goal states using Dijkstra’s minimum cost search technique. A computer program has been developed to implement this methodology for three-axis manipulators, and results of the application of this algorithm to some industrial robots are presented.
Analysis to Avoid Interference Between the Links of a Robot With Multiple Arms
Authors: Song Ning , Xu Liju , Sandor George N. , Shieh Ching-Shyong , Weng Tzu-Chen
Published: April 2021

An analytical method to evaluate link interference for a robot with multiple arms is presented with the consideration of shape and volume of links. A simplified geometric model of the links is established. The formulations and criteria to determine link interference are derived accordingly. The algorithm and the flow charts for conducting the analysis of interference between two links are given. The algorithm is applicable to general multiple-arm robots with not only revolute joints, but also prismatic joints. Numerical examples are presented for illustration.
An Algorithm for Real-Time Obstacle Avoidance and Path Planning for Mobile Robots
Authors: Srinivas Y. Lakshmi , Kramer Steven N.
Published: April 2021

This paper presents an extremely fast and reliable sensor-based algorithm that utilizes a combination of optimization techniques and heuristics to accomplish obstacle avoidance and path planning of mobile robots in real-time. This algorithm assumes no previous knowledge of the workspace and is capable of dealing with arbitrarily shaped obstacles with arbitrary motion characteristics. The concept of feasible circle is introduced to determine an obstacle-free subspace around the robot using information which can be obtained from distance sensors. This algorithm employs a unified approach and the modified Lagrange Multiplier method of optimization. A variable penalty, based on the distance of approach is used to keep the robot away from obstacles and the concepts of artificial obstacles and virtual obstacles are introduced to simplify the representation of the known workspace and to control the path of the robot. It is shown that the algorithm is general and can handle concave obstacles, overlapping obstacles, crowded workspaces as well as convex obstacles. The flexibility of the algorithm enables it to be easily integrated with different control strategies. The computational complexity is considerably less than for many existing algorithms, which makes the algorithm attractive for real-time applications. The algorithm is further extended to dynamic obstacles of arbitrary shapes and motion characteristics. Several case studies are presented to illustrate the capabilities of the algorithm.
Modeling of a Two Arm Flexible Robot in Gravity
Authors: Oh Chaeyoun , Vanderploeg Martin J.
Published: April 2021

This paper presents techniques used to model a two arm experimental robot developed at Iowa State University. Both arms are compliant and the robot operates in a vertical plane and is therefore influenced by gravity. The robot is being built to study different control strategies for robots containing compliant members. The system is built with extremely flexible members. This limits the required bandwidth of the control electronics, and mimics the flexible motions that are observed for stiffer faster robots.

The objective of this paper is to develop a reduced order model of the robot system and to experimentally validate the model. Validation requires that the model include gravitational effects. Therefore, an assumed modes model is developed which facilitates modeling of gravitational effects. In order to select the order and mode shapes for the model, an analytical solution is derived for a linearized continuous model. This is compared to the assumed modes model to determine the number of mode shapes needed to model the system. The final model, which includes shortening effects, correlates very well with experimental results.
The Workplace of a General Geometry Planar Three-Degree-of-Freedom Platform-Type Manipulator
Authors: Pennock G. R. , Kassner D. J.
Published: April 2021

This paper focuses on the direct workspace problems of a general geometry fully-parallel-actuated, planar three-degree-of-freedom platform-type manipulator. A set of equations are presented that determine the workspace as a function of the platform orientation. The formulation is governed by the solution to the inverse position problem of the manipulator. The reachable positions of the end-effector point, for a specified platform orientation, are analyzed. To illustrate the concepts, a practical example is included where the end-effector is required to move a cup filled with water. Then the platform orientation, for a specified location of the end-effector point, is studied. If an arbitrary orientation is possible, the specified location of the end-effector point is said to be within the primary workspace. The paper includes a detailed discussion of the total and primary workspaces of the manipulator. The approach adopted here is to regard the manipulator as a combination of three planar, three-revolute open chains. For the sake of completeness, the influence of special manipulator geometry on the workspace is also discussed. Finally, the paper includes the conditions that cause stationary configurations of the manipulator. Insight into these undesirable configurations is provided by a study of the location of the absolute instant center of the platform.
Inverse Kinematic Solutions of Free-Floating Closed-Chain Planar Manipulators
Authors: Agrawal Sunil Kumar , Garimella R.
Published: April 2021

This paper deals with inverse solutions of free-floating closed-chain planar manipulators. The problem, in essence, is to compute the joint angles given the position and orientation of the end-effector. For free-floating planar manipulators, in the absence of external forces and couples, the linear and angular momentum are conserved. This makes the solution procedure and the number of inverse solutions for free-floating manipulators different from those of corresponding fixed-base manipulators.

In order to illustrate this, we present the inverse kinematics of a free-floating planar manipulator whose end-effector is coupled to a base link by two R-R-R series chains. From the analysis, we conclude that for a given position and orientation of the end-effector, the location of the center of mass of the mechanism, and the orientation of the base link, upto 16 solutions of the joint angles are possible. To contrast, a fixed base manipulator of the same structure has a maximum of four solutions.
Modeling and Analysis of Parts Mating in Vibration Assisted Compliant Assembly
Authors: Leu Ming C. , Liu Y.
Published: April 2021

This paper presents the theoretical modeling and parameter analysis of vibration assisted robotic assembly involving peg-in-hole insertion. Transitions among various mating configurations during the vibration assisted insertion are studied. Mating forces and insertion motions are analyzed and numerically simulated. Insertion failure is classified into several types, with the characteristic of each type studied. The types of insertion failure include jamming due to insufficient assembly forces, jamming due to robot deflection, jamming due to assembly geometry restriction, wedging due to compression forces, and peg sliding opposite to the insertion direction. Experiments are performed, where vibration is applied to the hole piece when a SCARA robot is performing peg-in-hole insertion, to verify the analytical results.
On the Automatic Generation of Assembly Sequences for Polyhedral Assemblies
Authors: Beranek John M. , Dutta Debasish
Published: April 2021

We consider the problem of automatically generating all sequences for assembling a product. The individual components of the product are restricted to be polyhedra. Each node of the assembly tree represents a component and every branch from a leaf node to the root of the tree represents a feasible assembly sequence. The capability to generate all feasible assembly sequences, based purely on geometry, is necessary for deriving a good sequence based upon other criteria such as robot motion, fixturing and part stability.
Orientation and Insertion of Randomly Presented Parts Using Vibratory Agitation
Authors: Moncevicz Paul H. , Jakiela Mark J. , Ulrich Karl T.
Published: April 2021

In this article, we propose a new approach to automated assembly. Currently, automated assembly is expensive and difficult because all of the machines required for its implementation impose organization on the parts being assembled. It is this organization that is costly. We investigate an approach that requires less organization and results in assembly as a bulk process. We describe an initial implementation of this approach with a particular parts presentation system. Experiments are performed to determine the part characteristics that promote the success of the implementation. The experimental results are described and future work is suggested.
A Method of Position Sensing for Precision Assembly
Authors: Gurocak H. B. , de Sam Lazaro A.
Published: April 2021

The problem of part mating and assembly with close tolerances or fits has been addressed in the past by active or passive compliance and by force/position control. In this paper a position-sensitive wrist is described. A method is offered to ascertain the position of a peg during an unsuccessful attempt at assembly. The experimental and simulated results of this approach are presented. This work is a part of a research effort in precision assembly using a fuzzy control model.
A Two-Encoder Finger Position Sensing System for a Two-Degree-of-Freedom Robot Hand
Authors: Ng Kim-Gau , Parker Joey K.
Published: April 2021

As part of a robot hand with two independently controlled fingers each having one degree of freedom, a novel two-encoder position sensing system was designed for each of the fingers. In this system, a combination of a linear encoder and a rotary encoder is used to indicate finger position. The linear encoder provides coarse measurements while the rotary encoder provides fine measurements between two adjacent linear encoder counts. This two-encoder system permits more precise measurements than a system with only the linear encoder. The two encoders are connected to an IBM PC through an interface system. This paper presents the complete design and implementation of this two-encoder position sensing system.
An Improved Kinematic Model for Robots and Spatial Mechanisms: Part I — Model Development
Authors: Bodur Ibrahim Niyazi
Published: April 2021

In this paper an improved kinematic modeling method is developed which is applicable to both open and closed kinematic chain topology mechanisms. This methodology is based on relative coordinate frames assigned to the individual links and joints, and the 4 × 4 homogenous transformation matrices between these relative coordinate frames. The homogenous transformation matrices can accommodate the full six degrees-of-freedom necessary in 3-D space. Therefore, this method enables one to develop a kinematic model that corresponds to the actual mechanism. In doing so, the effect of the links and joints are considered separately which will aid one in conceptual and actual development of the model. The method is applied to a Cincinnati-Milacron T3 robot which is a six degree-of-freedom robot with a 3-D spatial serial configuration mechanism made of binary links and one degree-of-freedom joints connecting the links. The results obtained from the methodology developed here are compared to the results of a popular method developed by another researcher.

The methodology developed in this paper is applicable to higher degree-of-freedom joints, up to the full six degrees-of-freedom. It can also be applied to multi-loop mechanisms with the accompanying increase in the complexity of the model. This method helps to reduce the complexity of the problem when one uses the kinematic model of a mechanism in an interference checking, dynamic modeling and simulation, and link flexibility problem. Finally, it is shown that the use of 4 × 4 homogenous transformation matrices do not increase the calculational complexity of the problem appreciably.
An Improved Kinematic Model for Robots and Spatial Mechanisms: Part II — An Exact Kinematic Model of PUMA 560
Authors: Bodur Ibrahim Niyazi
Published: April 2021

In this paper an exact kinematic model of the PUMA 560 is developed. This model is based on the general purpose methodology developed in part one of this paper. Both the forward and inverse kinematic solutions of the PUMA 560 were developed from the model. The values obtained from both of these solutions directly correspond to the values obtained from the controller of the PUMA 560. The complexity of both of these solutions are comparable to the previously published results. This model and solutions demonstrate the applicability of the method developed as well as the availability of both the forward and the inverse solutions from the model.
A Survey of Part Presentation, Feeding and Fixturing in Automated Assembly Systems
Authors: Yeong Mengyik , Ruff Larry , De Vries Warren R.
Published: April 2021

The development of feeding, presentation and fixturing systems are essential in achieving the integration of design and manufacture. A bibliography of over 150 items serves as the basis of this survey of trends in the development of these systems for assembly. Recent technical literature, indicative of academic research and available commercial hardware systems are reviewed. While the emphasis of this paper is on presenting primarily mechanical solutions to the part feeding, presentation and fixturing problem, many papers which focus on AI, vision and knowledge-based systems are also included in the bibliography. In reviewing this literature, it is found that while many solutions have been presented, more work is needed toward fundamental understanding of the mechanics of feeding, presenting and fixturing, so that analysis and modeling can replace some of the re-design steps. This will aid in reducing the lead time by allowing systems to be designed from CAD data, rather than having to wait for prototype parts.
A Motion Synthesis Technique for Control of Planar Robots
Authors: Shirkhodaie Amir , Soni A. H.
Published: April 2021

Planar algebraic curves (polynomial, parametric type) are frequently required to be generated to manufacture specific geometric surface characteristics of the machine parts. Precision, accuracy, and speed are in general prime requisites. However, flexibility also becomes mandatory in today’s industry environment. A planar three degree of freedom robot is designed and fabricated with a built in forward and inverse kinematic algorithm. The robot may be programmed to generate planar enveloping curves where in the generator (tool) is an infinite line. Several examples are presented in this paper to illustrate the forward and inverse design of this particular planar robot for generation of algebraic curves.
Redundancy Compensation in Control of Multiple Arms
Authors: Shirkhodaie Amir , Soni A. H.
Published: April 2021

During manipulation of an object grasped at N locations by end-effectors of N robots, relaxation of assumption on invariant grasping locations of end-effectors Is too realistic. When coordinating end-effectors take infinitesimal displacements at the contact grasping locations with a rigid object, a slippage occurs which undesirably induces some redundancy in closed form kinematics/dynamics formulation of the entire robotic system. Particularly, in force/position control of multiple coordinating robot arms such an affect produces Inevitable impulsive reaction forces/moments which need to be compensated for in global control strategy of the system. In this paper, we have presented a control strategy with a Dynamic Redundancy Compensator (DRC) for cartesian space control of the coordinating multiple robots manipulating a common object. The proposed control scheme embeds dynamics of the individual coordinating robot arms and dynamically is capable to compensate for the kinematic/dynamic redundancies while preserving optimum forces/torques distribution between the end-effectors of robot arms. The results of study has been demonstrated on control of two robot arms manipulating a common object through prescribed coordinated motions.
Distributed Piezoelectric Neurons and Muscles for Shell Continua
Authors: Tzou H. S.
Published: April 2021

Conventional shell continua are passive, which do not possess any sensation and action/reaction capabilities. In this paper, distributed piezoelectric layers coupled with conventional elastic shell distributed systems are used as distributed “neurons” (sensors) and “muscles” (actuators) for structural monitoring and actuation of shells. New theories on distributed “neural” sensation and actuation of shells are developed based on a generic shell continuum coupled with piezoelectric neurons and muscles. Open and closed loop system dynamic equations are also derived. The system equations are further transferred to state equations. The derived theories can be directly simplified to a broad class of geometries, cylindrical shells, spherical shells, conical shels, zero-curvature shells (i.e., plates: rectangular, circular, etc.), beams, etc. Applications of the theories to a cylindrical shell using four system parameters, two Lame’s parameters and two radii of curvature, are demonstrated.
Theory on Hexagonal Symmetrical Piezoelectric Thick Shells Applied to Smart Structures
Authors: Tzou H. S. , Zhong J. P.
Published: April 2021

Smart piezoelectric structures, conventional passive materials integrated with piezoelectric sensors, actuators and control electronics, have great potentials in many engineering applications. This paper is devoted to a new theoretical development of generic piezoelectric shell distributed systems. System electromechanical dynamic equations, three translational coordinates and two rotatory coordinates, and boundary conditions, electric and mechanical, for a thick piezoelectric shell continuum with symmetrical hexagonal structure (Class C6v = 6mm) are derived using Hamilton’s principle and linear piezoelectric theory. The thick shell system equations are simplified to thin piezoelectric shells using Kirchhoff-Love’s assumptions. Converse effect induced electric forces/moments and boundary conditions can be used to alter system dynamics via open or closed loop control systems. Applications of the theories to a thick plate and a spherical shell are demonstrated in case studies.
Piezoelectric Modal Sensor/Actuator Design for Monitoring/Generating Flexural and Torsional Vibrations of Cylindrical Shells
Authors: Sung C. K. , Chen C. F. , Chen S. G.
Published: April 2021

This paper presents a methodology for designing piezoelectric sensors/ actuators in an application to monitor/generate flexural and torsional vibrations of cylindrical Shells. Based upon the classical laminate theory the equations of the electro-mechanical interactions, the constitutive, and the strain-displacement relations of piezoelectric composite cylindrical shells are derived. With these relations the piezoelectric sensor and actuator equations of the cylindrical shell are then developed. The modal sensors/actuators fabricated with PVDF embedded in the composite cylindrical shell capable of monitoring and generating vibrations of a particular mode or several combined modes are also developed. Finally, an experimental rig is designed to generate both the flexural and the torsional vibrations of a. circular cylindrical shaft for examining the capabilities of the modal sensors.
Piezoelectric Devices for Vibration Control on Flexible Structures
Authors: Legrain I. , Destuynder P.
Published: April 2021

A coupled numerical and experimental study, concerning the vibration control, on flexible structures by piezoelectric devices, is presented in this paper. More precisely we studied two cases of structure, a beam and a plate, in several configurations of excitation. The implemented controls, which are closed loop controls, concern always the first vibration modes.
Deflection and Force Experimental Verification of a Semicircular Polymeric Piezoelectric Actuator
Authors: Brei Diann , Blechschmidt James
Published: April 2021

This paper describes a manufacturing technique used to produce semicircular piezoelectric prototypes and the measurement techniques and results for three types of experiments performed to confirm the theoretical models. Since the microactuator design was new, unique and new methods of manufacturing had to be developed. This technique is a four step process that produces a prototype with a thin bonding layer with no bubbles. This prototype was tested and evaluated using three experiments: deflection-voltage, force-voltage, and force-deflection experiments. These experiments verified the theoretical model are correct.
Sensor Mechanics of Distributed Shell Convolving Sensors Applied to Flexible Rings
Authors: Tzou H. S. , Zhong J. P.
Published: April 2021

Observation spillover can introduce system instability to undamped distributed structural systems. This problem can be prevented via modal filtering using distributed piezoelectric modal sensors which are spatially shaped and convoluted such that they are only sensitive to specific modal mode(s). In this paper, detailed electromechanics — sensor mechanics — of spatially distributed piezoelectric shell convolving sensors are analyzed and results presented. It is observed that sensor sensitivity can be classified into two components: 1) the transverse modal sensitivity and 2) the membrane modal sensitivity in which the former is primarily contributed by bending strains and the later is by membrane strains. Design of spatially distributed cosine-shaped convolving sensors for ring structures is proposed and evaluated. Parametric studies suggest that the transverse sensitivity increases and the circumferential sensitivity remained constant when the ring becomes thicker. Both transverse and circumferential sensitivities increase when the piezoelectric layer becomes thicker or with higher piezoelectric constants.
Colocation: Design Constraints for Distributed and Discrete Transducers
Authors: Burke Shawn E. , Hubbard James E. , Meyer John E.
Published: April 2021

Colocated sensors and actuators offer significant robustness and design benefits in distributed parameter vibration control. The concept of colocation is extended to distributed transducers, and combinations of distributed and discrete transducers, affixed to self-adjoint distributed plants. It is shown that sensors and actuators are colocated only when they have both physically coincident spatial apertures and their “spatial derivative orders” are equal: these constraints are expressed mathematically as an integral equation. In satisfying these constraints the resulting transducer-augmented plant, if open-loop stable, is minimum phase. These results are demonstrated by transducer placement studies.
Optimal Placement of Actuators in the Precision Control of Truss Structures
Authors: Das S. K. , Utku S. , Chen G. S. , Wada B. K.
Published: April 2021

Actuator placement criteria in truss structures are based on satisfying two goals: (1) precision control (displacement control) of precision points, and, (2) prestressing control (i.e., creation of initial stresses) to counteract joint looseness. It is shown that stress-free exact displacement control is possible in (a) statically determinate trusses using as many actuators (q) as the number of independent degrees of freedom at precision points (p), i.e., q = p; (b) in statically indeterminate trusses using q = p + r actuators, where r is the degree of redundancy. Using (a) q < p actuators in statically determinate trusses will allow only for approximate displacement control, and, (b) using q < p+r actuators, in statically indeterminate trusses, will allow for: (1) exact, stress-induced displacement control if q > p, with q-p actuators to relieve stress as best as possible; (2) approximate, stress-free displacement control if p > q > r, or, (3) approximate, stress-induced displacement control if q < p and q < r. For prestressing control using actuators, the structure must be indeterminate at least to degree 1. If indeterminate to degree r, it is either possible to (a) exactly control a maximum of r components of member forces (using q = r actuators), or, (b) exactly control all member forces, provided they lie in the column space of the null matrix of the coefficient matrix of bar forces in the force equilibrium equations of the joints (using q = r actuators). By using q < r actuators, it is possible to exactly control only q components of member forces. It is also shown that, with sufficient number of actuators, prestressing control with no disturbance to precision points is possible. Optimal actuator placement schemes are studied for some of the above cases of precision control and prestressing control, based on objectives which are specific to each case. In statically indeterminate truss structures the optimal placement criteria and techniques differ depending on whether the primary determinate structure is known or not. A suboptimal actuator placement solution to the global optimization problem, combining the objectives of displacement control and prestressing control, is suggested (for the case q < p and q < r) by combining the results of the separate optimization problems (displacement control, prestressing control); the suboptimal solution is improved (with respect to global optimum) by iteration.
An Experimental Study of Tendon Vibration Control System for Flexible Space Structures
Authors: Murotsu Yoshisada , Okubo Hiroshi , Senda Kei
Published: April 2021

The idea of a tendon vibration control system for a beam-like flexible space structure has been proposed. To verify the feasibility of the concept, an experimental tendon control system has been constructed for the vibration control of a flexible beam simulating Large Space Structures (LSS). This paper discusses modeling, identification, actuator disposition, and controller design for the experimental system. First, a mathematical model of the whole system of the beam and tendon actuator is developed through a finite element method (FEM). Second, to obtain an accurate mathematical model for designing a controller, unknown characteristic parameters are estimated by using an output error method. The validity of the proposed identification scheme is demonstrated by good agreement between the transfer functions of the experimental system and an identified model. Then, disposition of actuators is discussed by using the modal cost analysis. Finally, controllers are designed for SISO and MIMO systems. The feasibility of the proposed controller is verified through numerical simulation and hardware experiments.
Transient Analysis on Turbo Engine Combustion Flow
Authors: Drakatos P. A. , Giannaras G. , Argyriou A. , Andriotis T.
Published: April 2021

One of the most important technical problem is the moniroting of the combustion flow, concerning the aircraft turbo-engine during its continuous operation.

Considering the combustion process as a dynamic excitation, we measure the noise and the vibration on chosen points on the engine. By doing that we come to conclusions concerning the combustion flow. In this experimental work appear the spectra of the noise and vibration measurements as a parameters of engine revolutions (R.P.M.).

The spectra of random combustion forces and spectra of noise and vibration borne noise structure are investigates using transient analysis.

Their analysis by P.C. and the construction 3-D diagrams which combine the noise level, the vibration level and the R.P.M., give us important information about the interdependance of the above sizes and the combustion flow. The measurements take place on the F-104 G Starfighter aircraft with the General Electric-J79 turboengine, which is the oldest military aircraft in today use.
The Quantification of Internal Noise Levels and Wall Pressure Spectra in Industrial Gas Pipelines
Authors: Norton M. P. , Pruiti A.
Published: April 2021

This paper addresses the issue of quantifying the internal noise levels/wall pressure fluctuations in industrial gas pipelines. This quantification of internal noise levels/wall pressure fluctuations allows for external noise radiation from pipelines to be specified in absolute levels via appropriate noise prediction models. Semi-empirical prediction models based upon (i) estimated vibration levels and radiation ratios, (ii) semi-empirical transmission loss models, and (iii) statistical energy analysis models have already been reported on by Norton and Pruiti 1,3 and are not reported on here.
The Importance of Transient Analysis on Internal Combustion Engines Structures
Authors: Drakatos P. A. , Haidas S.
Published: April 2021

Because of difficulties of applying Transient Analysis in complex structure we use a set up of instruments by exploiting the experimental results of known structures of engines.

Considering the combustion process as a dynamic excitation, we measure the noise and teh vibration on chosen points on a Spark Ingnition (S.I) engine and a Compression Ingnition engine (C.I). By doing that we come no conclusions concerning the combustion flow.

In this experimetnal work appear the spectra of the noise and vibration measurements in connection with the R.P.M. fo the engine. From the comparison between the spectra, we extract important results concerning the chanage of the combustion flow in every different type of engine in several stages.

The mesurements have been taken on a S.I. and C.I. engine in Special Engineering Laboratory.
The Use of Noise and Vibration Analysis on the Hydraulic Networks
Authors: Drakatos P. A. , Drakatos S. P.
Published: April 2021

This paper is concerned with Analysis of Vibration and Noise in a hydraulic networks. In the analysis it is tried to find the discrete frequencies. So, we are able to recognize the damages or to redesign the system. The most important effectiveness on the system ought to the flow in the phase of vorticity.
Research on Structure Optimization of the Engine Using Noise and Vibration Analysis
Authors: Drakatos P. A. , Drakatos S. P.
Published: April 2021

One of the useful problems in the engines is its operation optimization.

During combustion we use mixture of oil and soy-oil in a stroke internal combustion engine (S.I.C.E. during its continuous operation.

Considering the combustion process as a dynamic excitation, we measure the noise and the vibration on chosen points on a S.I.C.E. By doing that we come to conclusions concerning the combustion flow.

In this experimental work appear the spectra of the noise and vibration measurements in connection with the R.P.M. of the engine. The comparison between the diagrams in the case of the simple combustion and the comubstion of the mixture give us important information about the influence of mixutre in the S.I.C.E.

So, we can have results on the structure optimization of the engines.
Research on Air-Burned Gases Compressible Flow As a Function of Engine Sound Spectrum
Authors: Drakatos P. A. , Giannaras G. , Argyriou A. , Andriotis T.
Published: April 2021

The aerodynamic flow resulting from engine combustion flow is researched.

Considering the combustion process as a dynamic excitation, we measure the noise and the vibration on chosen points on the burned-gases flow. By doing that we come to conclusions concerning the combustion flow and the after-burning.

In this experimental work appear the spectra of the noise measurements in connection with the R.P.M. of the engine. It is tried to find the function of air compressible flow concerned with mechanical situation and combustion flow of the engine.

The comparison between the spectra give us important information about the interdependance between the noise and the combustion flow in the combustion chamber and the after burner. The measurements take place on several situation engine.
Shock and Sine Response of Rigid Structures on Nonlinear Mounts
Authors: Dufour R. , Hagopian J. Der , Pompei M. , Garnier C.
Published: April 2021

The dynamic environment of embarqued structures such as radars or more generally electronic equipments consists of impacts, sine and large power spectrum excitations. Under these real conditions and amongst different kinds of isolation, the passive damper with nonlinear parameters can provide good performances. This paper is concerned with the dynamic behavior of rigid bodies on highly nonlinear mounts. The numerical simulation and the experiment carried out, show that the load-deflection behavior of the dampers have to be slightly ajusted with respect to impact vibrations to obtain a well designed behavior.
Analysis of Base Excitation As an Uncertain Function With Specified Bounds on it and its Derivatives
Authors: Elishakoff Isaac , Pletner Baruch
Published: April 2021

In this paper the uncertainty in the base excitation of a lumped parameter structure is model led_as a function with specified bounds. Namely, the bounds are imposed on base acceleration, velocity or displacement. The investigation focuses on how global knowledge on the response is modified when global information on the excitation is increased. In particular, the maximum possible response the structure may develop is evaluated under the assumption that only the bound on base acceleration is known; then the maximum response is modified under the assumption that in addition to the base acceleration bound, the bounds on base velocity and displacement are specified.
Dynamic Properties of Rigid Body and Supports From Vibration Measurements
Authors: Pandit Sudhakar M. , Yao Ying-Xian , Hu Zhi-Quan
Published: April 2021

A method is presented to get the dynamic characteristics of a multi-DOF rigid body structure from the measured vibration data. These characteristics include the mass, center of gravity, moment of inertia and the principal axes of the body, stiffness, damping, the center of stiffness in any direction, moment of stiffness, center of damping and moment of damping, and the principal axes of the supports. The method is capable of representing structures with various DOFs, from 2 up to 6. The mass M, stiffness K, and damping C (or M−1K and M−1C) matrices are obtained first based on measured vibration data by Data Dependent Systems (DDS) methodology which is accurate even for highly damped structures. Relationships between the physical characteristics and these matrices have been derived so that the physical characteristics can be obtained by solving simultaneous linear equations. It is also possible to determine the characteristics up to 5 individual springs and dashpots to provide a basis for improvement in the structure’s performance.
Dynamic Analysis of Engine-Mount Systems
Authors: Ashrafiuon Hashem , Nataraj C.
Published: April 2021

This paper examines the forced response of an airplane engine supported by an elastic foundation. It is assumed that the vibrations of the engine and the foundation are small enough such that the equations of motion are linear. The engine is modeled as a rigid body connected to the foundation by standard industrial rubber mounts which act as three dimensional springs with a significant amount of hysteresis damping. Three fundamental models of the foundation are considered: rigid, statically flexible, and dynamically flexible. In the flexible cases, the foundation is modeled as a clamped circular plate, infinite plate, or any structure identified by a finite element stiffness matrix. In all cases, the mass, stiffness, and damping matrices of the engine-mount system are constructed and the frequency response to the rotating unbalance is determined. For the infinite and clamped circular plate cases, analytical methods are used to determine the real and imaginary parts of the flexibility matrix at different frequencies in response to the harmonic forces transmitted to the plate through the rubber mounts. It is shown here that the foundation elasticity may have a significant effect on the engine vibration and the mounting forces transmitted from the engine to the structure. It is also shown that only the dynamic model of the foundation is able to capture the correct response of the system at frequencies close to the foundation’s natural frequencies.
Vibration Analysis Methods Applied to Forensic Engineering Problems
Authors: Saczalski Kenneth J. , Loverich Eugene B.
Published: April 2021

Forensic engineering problems are reviewed to demonstrate how vibration analysis methods can be utilized in certain instances to determine cause of system failures and injury mechanics associated with certain vehicular accidents. A brief overview of injury criteria and biomechanical analysis methods for evaluation of motor vehicle occupant kinematics induced by shock impact loadings is also included.
Frequencies of Elastic Oscillations of a Tether-Platform System
Authors: Misra A. K. , Modi V. J. , Torchinsky S.
Published: April 2021

The paper investigates the longitudinal and transverse oscillations of an orbiting tether connecting a flexible platform and a subsatellite. The variation of tension along the tether due to the tether mass, as well as the effect of the platform equilibrium tilt on the tether tension are taken into account. The effects of tether to subsatellite mass ratio r, nondimensionalized offset a and platform equilibrium tilt ψo on the frequencies of elastic oscillations are examined. It is observed that the frequencies of longitudinal oscillations depend mainly on r, while those for the transverse oscillations can be expressed in the form λn2 = anr−1 + bn + Cnαψo, where λn is the nondimensionalized nth natural frequency, an, bn are constants, and cn varies linearly with r−1.
Approximate Formulas for the Transient Resonance Response of Mechanical Systems With Slowly Varying Natural Frequency
Authors: Irretier H. , Leul F.
Published: April 2021

The transient vibration problem of SDOF-system with constant natural frequency during run-up and shut-down for a linearly changing speed has already been solved by a number of authors using exact methods. However, during the transition process the natural frequency in many practical cases changes with time. In the present paper, the influence of natural frequency changes with respect to time is investigated using numerical simulation. Further, considering the computation time required, the paper suggests approximate formulas to estimate the maximum resonance amplitude during this transition. To illustrate the accuracy of the formulas, numerical results are shown in graphical formats.
Transfer Function Formulation of Constrained Distributed Systems
Authors: Tan C. A. , Chung C. H.
Published: April 2021

The transfer function formulation of constrained distributed systems is presented. The methodology is illustrated for subsystems under pointwise constraints and distributed systems consisting of multiple subsystems. A general displacement method (GDM) is used to determine the eigensolution of the constrained systems. It is shown that GDM requires only the natural boundary conditions (force constraints) be imposed at the subsystem interface. The methodology is applied to two examples. Curve veering and mode localization phenomena are found in an elastic structure on an elastic foundation.
Dynamic Analysis of Flexible Multi-Body Systems With Time-Variant Mode Shapes
Authors: Amirouche F. M. L. , Xie M.
Published: April 2021

The paper extends the theory of flexible multi-body systems to include time-variant mode shapes to account for the changes of boundary conditions that a flexible body undergoes while in motion. The method presented herein makes use of finite element methods to discretize the elastic body, then the nodal coordinates are related to the modal coordinates through the mode shapes. The latter are computed separately and their rate of change is accounted for in the dynamical equations of motion. The resulting governing equations of motion are presented in a computer form and a possible application problem is proposed.
A Preprocessor for the Treatment of Elastic Bodies in Multibody Systems
Authors: Sorge Kai , Pfeiffer Friedrich
Published: April 2021

A preprocessor providing the inertia data of elastic bodies for multibody algorithms is considered. The desired capability of including stress stiffening terms leads to a high computational effort. The method presented allows a straight forward implementation of the basic formulas by starting with the development of a special purpose symbolic calculator. A rotating elastic ring serves as an example.
Free Vibration of Simply Connected Bodies of Revolution by Boundary Collocation
Authors: Houmat A. , Hutchinson J. R.
Published: April 2021

A boundary collocation method is presented for solving the problem of free vibrations of isotropic, linearly elastic simply connected bodies of revolution of arbitrary shape and arbitrary boundary conditions. The problem is formulated in terms of a series of exact solutions of the governing differential equations in spherical coordinates. Boundary conditions are satisfied at a discrete number of points on the boundary. Results are obtained for a number of simply connected bodies of revolution. For a solid sphere with stress free boundary, the results are compared with known solutions. For other shapes, the results are compared with finite element solutions obtained using ANSYS. All comparisons show that the boundary collocation method produces excellent results.
Random Mobility Variation of Disordered Periodic Structures
Authors: Cai G. Q.
Published: April 2021

Due to material, geometric and manufacturing irregularities, a structure designed to be spatially periodic cannot be exactly periodic. The departure from perfect periodicity is referred to as disorder, and it is known to cause spatial localization of normal modes and attenuation of wave propagation even if the structure is undamped. In this paper, another effect of disorder is investigated; namely, possible energy concentration near where a excitation is applied, thus, inducing higher level of structure response, A computational procedure is developed for calculating the mobility, or mechanical admittance, of deterministically disordered periodic structures based on wave propagation theory, and then extended to the case of randomly disordered periodic structures. It is shown that, given the probability distribution of the disordered parameters of a periodic structure, the mean and standard deviation of the mobility magnitude can be obtained. The results are exact if the number of the periodic cell units is not large, and approximate if the number is large. Depending on the excitation frequency, the mean mobility magnitude of a disordered system may be either greater or smaller than that of the perfectly periodic counterpart.
Shock Design Rules for the Multi-Foundation Problem
Authors: Abdelhamid Mohamed K. , Cunniff Patrick F.
Published: April 2021

Dynamic analysis of equipment attached to shock excited vehicles is greatly simplified by spectral analysis. Using the modal shock design values to provide estimates of the maximum values of critical stresses in a base driven structure is a standard procedure used by the Navy for heavy equipment. This paper presents new results for design analysis that uses shock design values for those cases where the points of attachment between the equipment and the vehicle move differently from each other. This problem is commonly labeled the multi-foundation problem. The paper adopts the modal analysis approach and links the design rules of shock design analysis to bounding solutions derived from modal analysis. The design rule proposed for the multiple foundation case in this study requires the availability of the design shock values at different points of attachment between equipment and foundation. The method is easily programmable and can accommodate various equipment foundation models. A series of numerical experiments were conducted to establish a bench mark evaluation for the newly developed design rule. Comparison between the current standard procedures and the new design rule showed that the new rule estimates critical stresses that are closer to their true maximum values thus presenting an improvement over the current standard procedures.
Linearized Dynamic Models for Robot Manipulators With Varying Link Parameters
Authors: Li Chang-Jin , Sankar T. S. , Hemami A.
Published: April 2021

In this paper, two fast computational algorithms are developed for effective formulation for the linearized dynamic robot models with varying (kinematic and dynamic) link parameters. The proposed algorithms can generate complete linearized (inverse) dynamic models for robot manipulators, taking variations (e.g., inexactness, inconstancy, or uncertainty) of the kinematic and dynamic link parameters into account. They can be applied to any robot manipulator with rotational and/or translational joints, and can be utilized, also, for sensivitity analysis of similar mechanical systems. The computational complexity of these algorithms is only of order O(n), where n is the number of degrees-of-freedom of the robot manipulator.