bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Purposeful and Incidental Interactions
Authors: Liedholm Ulf
Published: February 2021

Within a product there exist interactions between the sub-systems. Some interactions are purposeful others might be incidental and even detrimental. The interactions are termed purposeful interactions and incidental interactions.

A classification of general inputs and outputs is presented. Different approaches for establishing purposeful interactions, especially during conceptual design are discussed in the paper.

It is important to find and identify incidental interactions as early as possible during design. In this paper an approach for finding incidental interactions, estimating the consequence of them and describing the countermeasures to them is presented.
Clarifying the Fuzzy Front End of New Product Development: Teaching Engineering and Industrial Design Students Ethnographic Methods to Foster Interdisciplinary Inquiry Into Consumer Needs
Authors: Cagan Jonathan , Vogel Craig
Published: February 2021

A unique approach to teaching new product development is discussed. The methodology emphasizes interdisciplinary collaboration between engineering and industrial design, and includes ethnographic techniques as a means to tie the early product development process directly to the user. The methodology builds on emerging trends in industry and the insights of the authors gained from teaching Integrated Product Development over a five year period. The approach emphasizes qualitative methods to help understand the fuzzy, early stages of the product development cycle, and the more traditional quantitative tools at the back end of the cycle. The goal is to create new products that enhance the experiences of consumers and connect with their lifestyles. The experiences discussed in this paper, while primarily formed through an academic setting, may lend new insights into product development processes for use within industry.
Towards Unambiguous Specifications: Five Alternative Job Control Models for an Object-Oriented, Hierarchical Shop Control System
Authors: Flater David , Barkmeyer Edward , Wallace Evan
Published: February 2021

In a distributed, object-oriented, hierarchical shop control system, there are many ways of organizing the interactions between supervisory controllers and subordinate controllers. Depending on what model of job control is used, objects will be allocated differently among the levels of control, and the interactions between controllers will vary considerably. This paper describes five models of job control that are equally functional, but use different paradigms for managing jobs. Although each is attempting to serve the same purpose in the same context, the five ways of viewing the system lead to distinct implementations that cannot interoperate. This demonstrates the importance of specifying the control model when designing an object-oriented manufacturing system.
An Intelligent Concrete Mix Design System
Authors: Dagnino Aldo
Published: February 2021

This paper describes the development and implementation of a computerized knowledge-based system (SmartMix) that provides assistance to concrete mix designers by automatically generating designs of concrete mixes. These concrete mixes can be used for the construction of power plants, buildings, bridges, etc. The generation of designs by SmartMix is based on current design practices and heuristic rules. SmartMix incorporates current empirical data and its knowledge base can be expanded to include data gathered in the future. SmartMix is a fully operational system and has been designed taking into account the existence of several concrete plants geographically distributed that produce concrete mixes. This is an important consideration because different materials will be available depending on the geographic location of a particular plant. The mix design provided by SmartMix addresses the specific requirements and characteristics of the concrete plant that is to produce it.

SmartMix was built using a knowledge-based systems environment called Smart Elements from Neuron Data. The system’s domain expertise consists of heuristic knowledge, statistical information and intelligent objects. The system has improved the reliability and consistency of the new concrete mix designs and has reduced dramatically the time and cost associated with the design of concrete mixes with respect to the manual process. The development of SmartMix was completed in 1995 as a result of a Joint Research Venture project between Pildysh Engineering Inc. and the Alberta Research Council. SmartMix has been in use since the fall of 1995 and is currently being used by Pildysh Engineering Inc. as a primary tool for the design of concrete mixes. Substantial cost savings and quality improvement have been achieved as a result of the implementation of SmartMix.
Evaluating a Change Process Product Data Model for an Analysis Driven Supply Chain Case Study
Authors: Cohen Tal , Peak Russell S. , Fulton Robert E.
Published: February 2021

This paper introduces a change management case study using Product Data-Driven Analysis scenarios from TIGER [TIGER, 97] — a supply chain case study — and an associated mapping to a STEP data model, a standard format product data model terminology. The case study describes supply chain scenarios that involve prime with contractors, subcontractors and consulting entities. The core activity within these scenarios is an engineering analysis of Printed Wiring Boards (PWB) with a focus on modeling product analysis data. Analysis of PWB can involve an iterative process that translates to changes to the product data. Application protocol 208 [STEP, Part 208/CD] is an underdeveloped part of the STEP standard and deals with product life cycle and change management. These changes are incorporated into the case study scenarios and the capability of AP 208 to capture them is evaluated.
UML-Based Mapping of the Product Structure Data Between CAD and PDM Systems
Authors: Oh Youchon , Han Soon-Hung , Lee Seung-Kuh , Shin SooHyun
Published: February 2021

Product data exchange between heterogeneous CAD/CAM/PDM systems is an issue for the integration of production systems. STEP offers a mechanism of product data exchange between heterogeneous systems. This paper introduces a UML-based mapping methodology for the product data exchange. The suggested mapping methodology has been applied to two different mappings. One is a mapping for the data exchange between a CAD and a PDM system. The other is the STEP to XML mapping for the information communication on the Internet.
Decentralized Control of a Tower Crane
Authors: Takagi Kiyoshi , Nishimura Hidekazu
Published: February 2021

This paper deals with modeling and control of a crane mounted on a tower-like flexible structure. A fast transfer of the load causes the sway of the load rope and the vibration of the flexible structure. Our object is to control both the sway and the vibration by the inherent capability of the tower crane. This paper makes its three-dimensional models for simulation and reduced-order-model in order to design the decentralized control system. Then, we design the decentralized H∞ compensator and verify the efficiency by simulations and experiments.
Liquid Dynamic Absorbers for Ropeway Carriers and Ships
Authors: Matsuhisa Hiroshi , Honda Yoshihisa
Published: February 2021

After Matsuhisa proved that the wind-induced swing of ropeway carriers could be reduced by dynamic absorbers in 1993, many absorbers have been installed in ropeway carriers. In the actual use of dynamic absorbers composed of a steel moving mass on a arc-shaped track, the tunings of natural frequency and damping coefficient are not easy. Liquid-type dynamic vibration absorbers have advantages of ease of tuning the natural frequency and the damping coefficient.

In this study, dynamic absorbers composed of liquid (water or viscous liquid) in V-shaped or U-shaped pipes were investigated. The natural frequency can be easily adjusted by the amount of water. The damping coefficient can be adjusted by nozzles at the terminals of pipe, an orifice or a net in liquid and by the viscosity of liquid. The reduction of rolling of gondola lifts, ships and cable suspension bridges by the liquid dynamic absorbers were investigated theoretically. The formula to predict the effectiveness of the absorber was derived. The relationship between the effectiveness of the absorber and its location and shape was discussed. The experimental investigations on the swing of pendulum, the roll of ships and flutter of cable suspension bridges were carried out by means of small models. It was found that the absorbers could reduce the rolling very well and it would be possible to install to the real gondolas, ships and cable suspension bridges.
Estimation of Frequency Response Function on Rotational Degrees of Freedom of Structures
Authors: Hosoya Naoki , Yoshimura Takuya
Published: February 2021

In conventional vibration testing, measurement of frequency response function (FRF) has been limited to translational degrees of freedom (DOF). Rotational DOFs have not been treated in experimental analysis. However, the rotational DOF is indispensable in further analysis, such as substructure synthesis, prediction of structural dynamics modification, etc. Hence, measurement of FRFs on rotational DOF is essential for expanding applicability of experimental modal analysis. This paper proposes a new method for FRF estimation on rotational DOF of structures. The following is the estimation procedure: A rigid block is fixed on the measurement point of the structure; the block is excited by conventional impact hammer; the inner force and the response of the connection point including rotational DOFs are estimated; and lastly, the FRF including rotational DOF at the connection point of the structure is obtained. The feasibility of the method is investigated experimentally by applying it to a beam structure.
Analysis of Noncontact Conveyance Using Manipulator and Permanent Magnet
Authors: Oka Koichi , Higuchi Toshiro
Published: February 2021

It is known that a magnetic suspension system can be made with a permanent magnet and a linear actuator. The linear actuator is used to control the air gap and makes a suspension system stable. By the application of this suspension mechanism, we can develop the robot manipulator with the function of noncontact conveyance using a permanent magnet. The object carrying capability and system stabilization are combined. Noncontact conveyance may be useful for clean or vacuum environments.

This paper describes analysis when a manipulator picks, carries, and places an object without mechanical contact. First, the principle of the suspension mechanism and the concept of the noncontact conveyance are explained. An experimental manipulator system which has two degrees of freedom of movement is introduced. This system is theoretically analyzed providing information necessary to suspend the object without contact. Control schemes of the states of picking, carrying, and placing are proposed, and an experimental result of noncontact conveyance is shown. Control parameters of states of picking and placing arc analyzed by numerical simulation, and it is shown that there exist optimal parameters.
Control of a Suspended Load Using Inertia Rotors
Authors: Yoshida Yasuo , Yajima Miyoka
Published: February 2021

Rotational control and swing suppression of a crane suspended load model are studied. A rotational free rigid body suspended by a single rope is controlled using three inertia rotors. Control angles and angular velocities are derived from measured data of fiber optic gyros installed on the suspended load. Rotor angular velocities controlling the suspended load are obtained by integrating the computed regulator control feedback accelerations based on the coupling system’s dynamics. Experiments and simulations investigate simultaneous control of the load’s rotational orientation and swing suppression.
Vibration Reduction and Isolation Using on-Off Control at Spring Support Joint: Application to Multi-Degrees-of-Freedom System
Authors: Yamaguchi Hideya , Yashima Masahito , Yoshikawa Takao
Published: February 2021

In order to achieve vibration isolation and reduction for a multi-degrees-of-freedom system, this paper develops the on-off control that has been proposed on the single-degree-of-freedom system by the authors. The method introduces an additional spring and mass system, and the additional mass is designed to control the clamping friction force by the friction joint switching mechanism. The non-linear control law for the single-degree-of-freedom system is applied to a multi-degrees-of-freedom system by incorporating the idea of the independent modal space control (IMSC) method. Numerical simulations and experiments demonstrate the effectiveness of the method.
Semi-Active Base Isolation for a Building Structure
Authors: Yoshida Kazuo , Fujio Tadahiro
Published: February 2021

Semi-active control methods, where coefficient of viscous damping or spring constant are changed effectively according to the state of control object, have received much attention from control performance and energy consumption. This study deals with the application of semi-active control method to base isolation control. Semi-active damper is classified into a bilinear system which belongs to a nonlinear system. The bilinear optimal control theory using feedforward control of disturbance is applied to a base isolation control problem of building structure. The variable damper used in this study is a discrete type of coefficient and it takes delay to switch the coefficient. By taking account of these characteristics, the control performance is investigated in the numerical calculation. As a result, it was shown that the method has high control performance in a wide frequency range, and it is effective for the vibration base isolation of building structures.
Partial Model Based Walking Control of Quadruped Locomotion Robot With Self Renovation Control Function
Authors: Uchida Hiroaki , Nonami Kenzo , Iguchi Yoshihiko , Jiu Huang Qing , Yanai Takaaki
Published: February 2021

It is considered that locomotion robots are aggressive under the circumstances where human hardly work, for example, in the nuclear power plant, in the bottom of the sea and on a planet. The injury and the fault of the robot might occur frequently under those circumstances. It is very important problem that the robot can realize the walking with the fault. This is very difficult problem for biped and quadruped robot to realize a stable walking in the case that actuator or sensor is broken. And, in walking of mammal, gait pattern is generated by neural oscillator existing in the spinal cord. In the case that a lower neural system is injured, mammal realize a walking by a higher neural system. Thus, mammal has a self renovation function. In this study, in order to realize the stable walking of the quadruped robot with fault, we discuss the control method with self renovation function for the fault of the decentralized controller and the angular sensor. First, we design the centralized controller of one leg by sliding mode control for the fault of decentralized controller. Second, Sky Hook Suspension Control is applied for the fault of the angular sensor. The proposed methods are verified by 3D simulations by CAD and experiments.
A Modal Filtering Approach for Active Vibration Control of High-Rise Structures Using Smart Sensors
Authors: Sivrioglu Selim , Kikushima Yoshihiro , Tanaka Nobuo
Published: February 2021

In most real structures such as buildings, bridges and others, the fundamental frequency is lower than 1 Hz, and it is generally enough to control such mode or modes to avoid damages of earthquakes. The well-known approach using point sensors and active mass dampers is employed to control vibration in high-rise structures. The effectiveness of this conventional approach can be disappointing when earthquake-like excitations are in question. Therefore, the development of actuators and sensors are particularly important for effective structural control.
Experiments of Active Tendon Control of Space Trusses
Authors: Bossens Frédéric , Preumont André
Published: February 2021

After a brief review of the strategy for damping cable structures with active tendons and a summary of the linear theory allowing to predict the closed-loop poles with a root locus technique, the paper presents experimental results obtained with two trusses. The first one is an active truss, clamped at its base and equipped with three guyed cables with active tendons; the second one is a free floating truss of geometry similar to the JPL Micro-Precision Interferometer; the three elementary trusses are connected by cables with active tendons. The experimental results tend to confirm the root locus predictions of the closed-loop poles.
Optimal Control of a Flexible Mechanism Using a Combined Feedforward-Feedback Strategy: Simulation and Experiment
Authors: v. Stein Hubertus , Ulbrich Heinz
Published: February 2021

Due to the elasticity of the links in modern high speed mechanisms, increasing operating speeds often lead to undesirable vibrations, which may render a required accuracy unattainable or, even worse, lead to a failure of the whole process. The dynamic effects e.g. may lead to intolerable deviations from the reference path or even to the instability of the system. Instead of suppressing the vibration by a stiffer design, active control methods may greatly improve the system performance and lead the way to a reduction of the mechanism’s weight. We investigate a four-bar-linkage mechanism and show that by introducing an additional degree of freedom for a controlled actuator and providing a suitable control strategy, the dynamically induced inaccuracies can be substantially reduced. The modelling of the four-bar-linkage mechanism as a hybrid multi body system and the modelling of the complete system (including the actuator) is briefly explained. From the combined feedforward-feedback optimal control approach presented in (v. Stein, Ulbrich, 1998) a time-varying output control law is derived that leads to a very good system performance for this linear discrete time-varying system. The experimental results show the effectiveness of the applied control strategy.
Finite Element Modeling of a High Speed Optical Depth Scanner
Authors: Szydlo J. , Lehmann R. , Lassen T. , Bleuler H.
Published: February 2021

A rotational high-speed depth scanner for an optical low-coherence reflectometer used for 3-D retina scanning has been developed and analyzed. A rotational speed of 427’000 rpm (in the range between the 4th and 5th critical speed) has been reached for the 5 × 5 × 2 mm3 BK7 glass cube, resulting in a record scan rate for this kind of instrument. This paper reports on our experimental results as well as the FE-modeling of the rotor and the internal-reflection glass cube under centrifugal stress, and on the interplay of mechanical deformation and optical performance. The scanner is mounted on air bearings and driven by an air turbine.
Developments of the Hydraulic Driving System of the Control Rods for Nuclear Reactors
Authors: Wu Yuanqiang
Published: February 2021

The developments of a new hydraulic driving system of the control rods for nuclear reactors are introduced in this paper. Compared with other driving systems of the control rods, this new hydraulic driving system can be set within the reactor pressure vessel. Under any serious condition, the control rods will not be ejected from the reactor core. Its structure is very simple and the mechanic chain is very short, and thus it is very reliable. It can reduce the height of the nuclear reactor by one-third, and thus dramatically reduce the cost of the reactor. It uses the dynamic hydraulic pressure to control the motion of the control rods. Under extreme conditions, such as the failure of control power supply, the control rods will drop into the reactor core because of their self-weight to shut down the nuclear reaction. Because of these features, International Atomic Energy Agency (IAEA) is very interested in this safe and economical new control rod driving system. A brief history of the developments of the hydraulic driving system is given. Three configurations, the orifice hydraulic step cylinder, the groove-orifice hydraulic step cylinder, and the piston-groove hydraulic step cylinder, are introduced and their working principles are explained. The reliability and safety of the new system are validated by two experimental works: hydraulic step cylinder (HSC) under seismic and rocking conditions. Results from these experiments are presented.
Tension and Speed Regulation of Axially Moving Materials
Authors: Nagarkatti Siddharth P. , Zhang Fumin , Rahn Christopher D. , Dawson Darren M.
Published: February 2021

In this paper, the tension and speed of an axially moving material system are regulated using control torques applied to rollers at each end of a controlled span. Given a distributed parameter model, Lyapunov-type arguments produce a model-based boundary control law that exponentially stabilizes the material tension and speed at the desired setpoints. Dynamic simulation results compare the tension and speed setpoint regulation provided by the proposed control strategy with standard PID approaches.
Monte Carlo Simulation of Grain Growth at Heat Affected Zone (HAZ) of Weldment
Authors: Jahanian S. , Lei Wen
Published: February 2021

Average grain size and grain size distribution at HAZ is the dominant microstructural features of weldment. Such features may govern many properties of the weldment, such as strength, ductility, toughness, corrosion resistance and so forth. Accordingly, prediction of the final grain size and grain distribution is crucial to a welding engineer. The nature of grain growth in the weldment is known to be stochastic. Hence, using a deterministic method for predicting the final grain size of weldment should be reconsidered.

In this paper Monte Carlo simulation of grain growth at Heat Affected Zone (HAZ) of a 0.5 Mo-Cr-V steel is presented. The technique used for this simulation is discussed. We also use a methodology to obtain a one-to-one correlation between Monte Carlo (MC) and real parameters of grain size and time. The results are compared with the experimental results and a reasonable agreement is observed.

To carry out the simulation, we generate a random 200*200 matrix. Each element of this matrix represents a grain site with a unique grain orientation at the beginning of the simulation. We run the simulation for both bulk heating situation and HAZ zone to decide the thermal pinning effect. In the case of HAZ. zone, the center of this matrix represents the fusion zone of the HAZ. Periodic boundary conditions are used so that the grains wrapping around are at the same temperature. To make a comparison, we look at a HAZ location about 120 microns from the fusion zone and compare it with the grain size obtained in an actual weld HAZ at an identical location.

The simulation result shows a near match with the experimental data for bulk heating. The grain structure of the simulation result in the weld HAZ also has a reasonable accuracy. It can be concluded that the MC technique could effectively capture the thermal pinning existing in the weld HAZ. The difference between the simulation result and the experimental data suggest the effect of thermal pinning is higher than the effect based on the thermal gradient alone.
One Decade of Holospectral Technique: Review and Prospect
Authors: Qu Liangsheng , Xu Guanghua
Published: February 2021

The holospectrum is a FFT based spectrum. It integrates the spectra of the vibration signals in one or more bearing sections of a rotor. This paper summarizes the experience in application of the holospectral technique to diagnose the potential faults of large rotating machinery, its key technique, recognition ability and other advantages. Further potential applications of this technique in rotor balancing, performance evaluation and long range forecasting of large rotating machinery are envisaged.
Accumulator Roll Analysis Using the Finite Element Method
Authors: Pierson Hazel M. , Suchora Daniel H. , Viviano Anthony V.
Published: February 2021

The purpose of this study was to develop a method to analyze various designs of non-driven accumulator rolls using a static finite element software package. This would allow the engineer to determine how the various components of the roll design contribute to or lessen the deflection of and stresses in the roll body when it is loaded by sheet metal passing over o under it. The method outlined is intended mainly for use when an advanced dynamic finite element package that incorporates contact elements is not available and when a comparison of various roll designs is desired.

First, an approximation of the pressure on the roll body caused by the force of the sheet metal as it wrapped over or under the roll was determined. Then using the finite element package ALGOR, an FEA model of a standard accumulator roll design was loaded with this pressure and the stresses and deflections were calculated. Next, components of this basic roll design were varied in the FEA model. These were the location of the stiffeners and the thickness of the roll body, the end plates, and the stiffeners. A comparative approach was then used to assess the impact each of these variations in roll design had oh the deflection of and the stresses in the roll.
Commercial Walk-Behind Lawn Mower Failure Analysis Case Study
Authors: Brickman Dennis B.
Published: February 2021

A failure modes and effects testing program was conducted to analyze the cause of a mid-size commercial walk-behind lawn mower accident in which the operator’s foot came in contact with the rotating blade. Systematic analysis showed that the accident was caused by improper mower service and operator misuse of the mower. Testing results reveal that an alternative design proposal does not preclude this random event. Accident prevention countermeasures are explored.
Minimally Invasive Suturing Device
Authors: Fudge Brian M. , Verkade Drew
Published: February 2021

The design of an intracorpeal suturing device that will assist surgeons in placing an internal suture through a small incision. Performing surgical procedures through a small incision greatly reduces patient trauma and rehabilitation time, both of which are proportionally related to medical costs. Medical devices exists today that allow surgeons to perform procedures through small incisions, unfortunately, it is difficult to place sutures deep in the body using minimally invasive techniques. A device that enables surgeons to place sutures minimally invasively will facilitate surgeons by increasing the scope of procedures that can be preformed using this technique.
Patents: Restoring Safety
Authors: Barnett Ralph L.
Published: February 2021

The law punishes manufacturers who embrace safely innovation and product improvement. The “new” is literally the enemy of the “old” in the sense that a new safety design may be used by the law to show that all past and current designs are defective. On the other hand, if the new design is patented, a special attribute precludes its invocation as a remedial measure for a safety problem which predated the patent.
Ladder Slide Out: First Order Analysis
Authors: Barnett Ralph L.
Published: February 2021

One of the more important collapse modes for straight, combination, and extension ladders is base slide out; the top of the ladder slides down the support wall as the base slips away from it. Various fundamental models have been used to study this behavior. This paper revisits the analytical solutions associated with these models and describes their implications for the analysis, design, and testing of ladders.
Trencher: Impingement on Buried Objects
Authors: Brickman Dennis B. , Barnett Ralph L.
Published: February 2021

There is a resemblance between the digging chain of a trencher and the folklore chain saw. The safety of trenchers requires that the similarities and differences between these two machines be understood so that appropriate warning signs can be formulated. There is a notion that the trencher can be suddenly thrust rearward in the direction of the digging chain in the manner associated with the chain saw. There is also a notion that the kickback characteristic of the chain saw is also characteristic of a trencher digging chain. This paper shows that these rearward thrust and kickback notions for the trencher are false. On the other hand, contact with moving teeth is hazardous on either machine.
Symmetrical Motions of Tensegrity Structures: A Reconfiguration Procedure
Authors: Sultan Cornel , Skelton Robert E.
Published: February 2021

In this paper we derive the nonlinear equations of motion for tensegrity structures and cast them in vector second order form. For certain tensegrity structures a particular class of motions, coined symmetrical motions, is defined. The corresponding equations of motion are presented and the conditions under which symmetrical motions occur are established. A reconfiguration procedure through symmetrical motions is proposed and examples of its application are given.
Coupling Finite Element Method and Perturbation Techniques for Non Linear Vibrations of Plates
Authors: Azrar L. , Benamar R. , Potier-Ferry M.
Published: February 2021

The effectiveness of the coupling of the perturbation techniques and the finite element method has been demonstrated using a method called Asymptotic-Numerical Method (ANM). This concept eliminates the major difficulties of the classical perturbation methods namely the complexity of the right hand sides and the limitation of the validity of the solution obtained. In this paper we present the development of this method and its applicability for large amplitudes free vibrations of plates. The displacement and the frequency are expanded into power series with respect to a control parameter. The nonlinear governing equation is transformed into a sequence of linear problems having the same stiffness matrix. Needing one matrix inversion, a large number of terms can be computed with a small computation time. Taking the starting point in the zone of validity, the method is reapplied in order to determine a further part of the nonlinear solution. In order to increase the zone of validity, the Pade approximants are incorporated. Iterations of this method lead to a powerful incremental method. Numerical tests for large amplitudes free vibrations of plates with various shapes and boundary conditions are reported. Recent improvements in the basic ANM algorithm as well as applications to various structural problems are added in order to exhibit the effectiveness and the applicability of this method.
Stabilization of Mechanical Structures With Distributed Sensors and Actuators: A Hamiltonian Approach
Authors: Schlacher Kurt , Kugi Andreas
Published: February 2021

Intelligent mechanical structures based on piezoelectricity form an important new group of actuators and sensors for active vibration control. Since this technology allows to construct spatially distributed devices, new design possibilities for the control systems open up. Now the design of the spatially distributed sensors and actuators becomes part of the controller design itself. Several well established approaches, like the PD-, H2- and H∞-design are adapted to solve this problem. They are based on infinite dimensional Hamiltonian systems in conjunction with collocated actuator and sensor pairing. Since this approach is based on the so called Poisson bracket only, one can unify the controller design for finite and for infinite dimensional systems. Of course, the stability investigations are much more complicated in the latter case. Finally, applications to beams and plates demonstrate the power and effectiveness of the proposed methods.
Design of Dynamical Controllers for Linear Hamiltonian Systems
Authors: Haas Werner , Krommer Michael , Irschik Hans
Published: February 2021

Linear Hamiltonian control systems with collocation of sensor and actuator are considered. Based on a frequency domain approach a controller design algorithm is stated. The design leads to a controller with internal dynamics which uses the output of the system and its first time derivative. The presence of internal dynamics in the controller is an extension of the usual PD–control law and a main result of the work. The design is based on the special properties of the proposed class of systems. In particular, these Hamiltonian systems are passive. It is shown that the design leads to strictly passive controllers for a certain choice of the design parameters. This is another significant result and offers a way for robust ℒ2–stabilization even in the case of infinite dimensional systems. Some features of the controller design are discussed with respect to an application, the control of a composite circular plate.
Effects of Harmonic Intentional Mistuning on the Free Response of Bladed Disks
Authors: Brewer Michael E. , Castanier Matthew P. , Pierre Christophe
Published: February 2021

In this paper, the free response of bladed disks with intentional mistuning is considered in detail. A simple lumped-parameter model of a bladed disk is employed. Intentional mistuning is included by applying a sinusoidal variation to the nominal blade stiffnesses. It is shown that if the intentional mistuning harmonic number and the number of blades have a common integer factor greater than one, then the eigenvalue problem reduces to a set of smaller problems. It is found that the ratio of intentional mistuning strength to the interblade coupling strength is a key parameter for the free response. As this ratio increases, the modes become localized. More importantly, the modes of the intentionally mistuned system have several non-zero nodal diameter components, in contrast to the tuned system which has pure nodal diameter modes. Furthermore, if only random mistuning is present, each mode of the bladed disk assembly still retains a strong nodal diameter component. However, the modes of the system with intentional mistuning and random mistuning tend to have more evenly distributed nodal diameter components. This shows why intentional mistuning can be effective in reducing the maximum blade forced response for engine order excitation.
Analog Simulation of Phase Locked Modes of Diffusively Coupled van der Pol Oscillators
Authors: Low Lesley Ann , Reinhall Per G. , Storti Duane W.
Published: February 2021

Limit cycle oscillators arise in a wide variety of mechanical, electrical and biological systems. Recently, emphasis has been placed on the study of systems of coupled limit cycles, such as cardiac oscillations. Synchronization criteria have remained a focus of most investigations.

One area of investigation in the field of coupled limit cycles is studying the behavior of a pair of linearly coupled van der Pol oscillators (Low, 1998; Rand, 1980; Sliger, 1997). Previous investigations (Storti, 1993; Storti, 1996) found the stability regions of the coupled oscillators for their in-phase and out-of-phase modes numerically.

The coupled oscillators can be viewed as a mechanical system, where the coupling parameters are equivalent to a spring and damper attached between two masses. With positive coupling (positive damping) a region was found (Storti, 1993; Storti, 1996) where the in-phase mode is unstable. This counter intuitive result is yet to be discovered in a physical system of two coupled limit cycle oscillators. This research focuses on finding the region with positive coupling parameters where the in-phase mode is unstable using a physical model of two linearly coupled van der Pol oscillators. The coupled van der Pol oscillators were modeled using an analog electric circuit.
A Non Parametric Model for Magneto Rheological Dampers
Authors: Ahmadian Mehdi , Song Xubin
Published: February 2021

A non-parametric model for magneto-rheological (MR) dampers is presented. After discussing the merits of parametric and non-parametric models for MR dampers, the test data for a MR damper is used to develop a non-parametric model. The results of the model are compared with the test data to illustrate the accuracy of the model. The comparison shows that the non-parametric model is able to accurately predict the damper force characteristics, including the damper non-linearity and electro-magnetic saturation. It is further shown that the parametric model can be numerically solved more efficiently than the parametric models.
Static and Dynamic Characterization of Tensegrity Modules
Authors: Murakami Hidenori , Nishimura Yoshitaka
Published: February 2021

A set of procedures was presented for characterizing static and dynamic response of tensegrity modules. The procedures were applied to two tensegrity modules: a six-bar spherical module and a two-stage cylindrical module with three bars at each stage. The singular value decomposition of the initial equilibrium matrix revealed pre-stress and infinitesimal mechanism modes. The pre-stress stiffening effect of mechanism modes was found to be isotropic at each node. In the initial quasi-static loading, infinitesimal mechanisms exhibited soft response. As the deformation advanced, the stiffness of tensegirty modules increased almost quadratically with infinitesimal mechanism-mode amplitudes. Modal analyses revealed that the lowest modes were those of mechanism modes and their natural frequencies were an order of magnitude smaller than those of higher deformation modes.
Application of Robust Two Degree-of-Freedom Control Using μ-Synthesis to the Vibrations in Vehicle Engine-Body System
Authors: Yang J. , Suematsu Y. , Shimizu S. , Okumura Y.
Published: February 2021

This paper presents a robust active control for the vehicle engine-body system. The robust two degree-of-freedom (2DOF) controller is formed by combining a feedback (FB) controller with a feedforward (FF) controller. The feedback controller is designed by μ-synthesis to attenuate the effect of engine vibration disturbance by modeling the vehicle engine-body system as a nominal four degree-of-freedom vibration system with the parameter variations and the unmodeled dynamics. Based on filtered-X LMS algorithm, an active vibration controller is used as a feedforward controller to improve control performance further. To demonstrate the effectiveness of the control scheme, we have made some experiments in an experimental device, which is designed to imitate real vehicle engine-body system.
Theoretical and Experimental Finite Forced Dynamics of a Cantilever Beam: Dynamic Instability and Modal Coupling
Authors: Benedettini Francesco , Di Egidio Angelo
Published: February 2021

The 3-d dynamics of a cantilever beam undergoing large displacements under a sinusoidally varying, concentrated, vertical force at its free end is analyzed. The pde’s of the motion are obtained by using the Hamilton principle and then a reduced 3 degree-of-freedom model is obtained using in a Galerkin discretization, three eigenfunctions of the linearized model. A path following procedure is used to describe the global dynamic behavior in the excitation control parameter plane. The results obtained using the simple 3 d.o.f. analytical model are then compared with those of an experimental steel model of the cantilever. The regions of instability of the unimodal planar solution in which the nonlinear modal coupling excites the torsional component are studied; the planar motion usually looses stability via Hopf bifurcations after which quasi-periodic and/or chaotic motions are found. Inside the regions in which the system shows a complex time-evolution the complexity-level of the response is analyzed using, for the experimental model, a time series analysis tool.
Sine Sweep and Steady-State Response of a Simplified Solar Array Model With Nonlinear Support
Authors: Fey Rob H. B. , Winter Berend , Wijker Jaap J.
Published: February 2021

In this paper the dynamic behaviour of a multi degree of freedom beam model of a solar array structure is investigated both experimentally and numerically. The beam is supported by one nonlinear element, a so-called snubber. This snubber can only take compressive forces. Two types of excitation are applied and compared: sine sweep excitation (with different sweep rates and directions) and steady-state excitation. Emphasis lies on the investigation of the dynamic behaviour of the system under prestress, which implies softening behaviour at the time when snubber and beam loose contact. The system displays rich nonlinear dynamic behaviour: multiple solutions (hysteresis loop), superharmonic resonances and subharmonic, quasi-periodic and chaotic solutions. Good correspondence between experimental and numerical results has been found.
Reflexive Control of Slipping in an Anthropomorphic Bipedal Locomotion Robot
Authors: Healy T. A. , Reisinger K. D.
Published: February 2021

To be successful a bipedal locomotion system will be required to robustly traverse terrain with unknown and varying surface conditions. Even in made-for-human environments a broad range of surface conditions may be encountered and slipping is a very real and serious concern. Since a priori detection and avoidance is not practical, a robust system must detect and respond to the unexpected event after it has occurred and before control is lost. This must be accomplished in an extremely limited time frame. This paper proposes the use of human-like reflexes to enable robust recovery from slipping. The proposed algorithm seamlessly integrates reflexive responses into the nominal control system. Effectiveness of the algorithm is demonstrated via simulation results.
Post-Critical Response of an Axially Moving Beam
Authors: Pellicano Francesco , Vestroni Fabrizio
Published: February 2021

In this paper the dynamic response of a simply supported traveling beam, subjected to a pointwise transversal load, is investigated. The motion is described by means of a high dimensional system of ordinary differential equations with linear gyroscopic part and cubic nonlinearities obtained through the Galerkin method. The system is studied in the super-critical speed range with emphasis on the stability and the global dynamics that exhibits special features after the first bifurcation. A sample case of a physical beam is developed and numerical results are presented concerning bifurcation analysis and stability, and direct simulations of global postcritical dynamics. In the supercritical speed range a regular motion around a bifurcated equilibrium position becomes chaotic for particular values of frequency and force. The bifurcation diagram for varying force intensity is shown, it can be noticed that a chaotic motion occurs in a wide range of the forcing parameter, co-existing with a 3T periodic solution in a limited window.
Global Analysis of the Double Impact Oscillator Dynamics
Authors: Peterka František
Published: February 2021

The double impact oscillator represents two symmetrically arranged single impact oscillators. It is the model of a forming machine, which does not spread the impact impulses into its neighbourhood. The anti-phase impact motion of this system has the identical dynamics as the single system. The in-phase motion and the influence of asymmetries of the system parameters are studied using numerical simulations. Theoretical and simulation results are verified experimentally and the real value of the restitution coefficient is determined by this method.
Control of a Quarter-Car Model With Variable Damping
Authors: Verros G. , Natsiavas S. , Stepan G.
Published: February 2021

Dynamics of a strongly nonlinear quarter-car model is investigated. The nonlinearity is due to a control strategy which selects the damping coefficient of the car suspension in a way that the resulting semi-active system approximates the performance of an active suspension system designed to produce sky-hook damping. According to this control strategy, the damping coefficient switches between two different positive values, leading to a piecewise linear dynamical model. For this model, the equation of motion is first presented in a general normalised form. Then, an appropriate methodology is applied for obtaining exact periodic motions for the case of forcing resulting from a road with harmonic profile. This methodology is based on employing the exact solution form within response intervals where the damping coefficients remain constant. The unknowns of the problem are then determined by imposing a set of periodicity and matching conditions. The stability analysis of the located motions is also performed by applying a method which is suitable for piecewise linear systems. Next, this analysis is applied and representative numerical results are obtained. Namely, response diagrams are presented, showing the effect of the important system parameters on the existence, amplitude and stability properties of various branches of periodic solutions. The results are also compared to those of the conventional suspension systems, including passive bilinear shock absorbers.
Influence of Bearing Compliance on Long-Term Nonlinear Rotordynamics
Authors: van de Vrande Bram L. , de Kraker Bram
Published: February 2021

This paper presents the influence of bearing liner compliance on the long-term dynamics of a symmetric rigid rotor on short journal-bearings. Both balanced and unbalanced rotors are investigated for different values of the compliance, using the (nondimensional) rotor speed as the bifurcation parameter. The results show a decrease in the onset speed of instability of the balanced rotor, and a considerable influence on the 1/2-subharmonic solutions in case of unbalance excitation.
Nonlinear Vibro-Acoustic Response of a Metal Sample With a Discontinuity-Like Defect As Related to Damage Detection Problems
Authors: Zaitsev Vladimir Yu. , Sas Paul
Published: February 2021

The nonlinear vibro-acoustic response of solid samples containing quite a small amount of defects can be anomalously high in magnitude compared to the case of undamaged intact solids. Functional dependencies of the nonlinear effects exhibit rather interesting behavior. In this paper, experimental results on nonlinearity-induced cross-modulation of a high-frequency (HF) f = 15...30 kHz signal by a low-frequency (LF) F = 20–60 Hz vibration in an aluminium plate with a small single crack are reported. Comparison with a reference sample (the identical plate without a crack) has proven that the presence of such a small defect can be easily detected due to its nonlinear manifestations. It is demonstrated that under proper choice of the sounding signal parameters, the effect level can be so pronounced that the amplitude of the modulation side-lobes originated due to the nonlinearity exceeds the amplitude of the fundamental harmonic of the HF signal. Main physical features of the observed phenomena are pointed out, their physical explanation is suggested and some simulation results are also presented.
Slowly Modulated Traveling Waves in Circular Plates Spinning Near Critical Speed
Authors: Raman Arvind , Mote C. D.
Published: February 2021

Motivated by observations of low-frequency “snaking” motions of circular sawblades encountered during cutting operations, we study the large amplitude transverse vibrations of an imperfect, flexible, lightly damped, circular plate spinning near a critical speed resonance. Of particular interest are the effects of imperfection and the conditions under which low-frequency, amplitude and phase modulated traveling waves, that is snaking motions, can arise in this system. This is accomplished through a local bifurcation analysis of the first-order averaged equations governing the nonlinear interaction, under conditions of a 1 : 1 internal resonance, of a pair of backward and forward traveling waves. Experiments are performed at reduced ambient pressure on a rotating steel disk with imperfection induced through attached point masses, to confirm qualtitatively the analytical predictions. The experiments also indicate an unexplained, additional superposed slow motion on all solution branches.