bluuebunny/crossref_metadata_2025 huggingface dataset:
A DESIGN METHODOLOGY FOR ZERO REACTION ROBOTS
Authors: Papadopoulos E. , Abu-Abed Ahmed
Published: April 2018

In many applications of advanced robotic systems, reaction forces and moments transmitted by a manipulator to its base are highly undesirable. Such reactions reduce the accuracy of high-speed manipulators, destroy zero-g environments in space, require the use of thruster fuel to stabilize free-flying space robots, or excite suspension modes in mobile robotic systems. In this paper, we analyze the problem of force and torque transmission in robotic systems, and propose design and planning methods that can reduce it, or eliminate it. It is shown that designing a force-balanced manipulator with an invariant mass matrix, and employing appropriate trajectory planning, can result in reactionless motions. Two redundant planar manipulator designs, that can be used as building blocks of more complicated systems, demonstrate the usefulness of the proposed methods. An important advantage of these methods is that if reactionless behavior is not needed, system redundancy can be recovered.
ON THE MICROMECHANICS MODELING OF MICROCRACK TOUGHENING IN CERAMIC MATERIALS
Authors: Gong S.X.
Published: April 2018

The development of advanced ceramic materials with enhanced toughness relies upon the fundamental understanding and accurate modeling of various toughening mechanisms in these materials. In this paper, a rigorous micromechanics approach is proposed to treat the microcrack toughening phenomena in ceramics. The microcracking zone is modeled as a region containing multiple discrete microcracks near the tip of a dominant crack and the main crack-microcrack interactions are studied in detail. The analysis is based upon the use of the complex potentials of Muskhelishvili and an appropriate superposition scheme. The induced stress intensity factor at the main crack is obtained in a general series form and the leading order explicit solution is utilized to investigate the associated shielding and amplification effects and to provide a quantitative analysis of the microcrack toughening. Both a stationary and a steadily growing main crack are considered and the effect of the release of residual stresses has been taken into account. The relationship between the current model and other existing ones is also discussed.
THE INFLUENCE OF TEMPERATURE ON THE DRIFT OF GYROSCOPE
Authors: Ge Zheng-Ming , Liu Ming-Yen , Lee Sann-Chie
Published: April 2018

The dynamics, especially the drift, of a gyroscope with slowly varying axisymmetrical mass distribution are studied. By the data of temperature field of the inner gimbal, the changes of the position of center of mass and moments of inertia of the inner gimbal of gyro with time are obtained through the finite element method and approximate model study. The drift of a gyroscope can be analytically investigated according to the variation of the nutation angle and the precession angle. Since the temperature varies with time, the equations of motion are nonautonomous nonlinear differential equations. The analytical approximation is obtained by multiple scales method. The nutation angle and the precession angle in some given time intervals are calculated and are compared with the numerical results, obtained by using the MATLAB software package, with satisfactory consistency.
SCALAR FORM OF DYNAMIC EQUATIONS FOR A TOPOLOGICALLY UNIFORM 3D-CHAIN
Authors: Vinogradov O.
Published: April 2018

A topologically uniform 3D-chain is defined as a system of one-dimensional links connected by spherical joints. In addition each link has an internal translational degree of freedom along its axis. Such a chain can be viewed as a generic manipulator so that any specific type of the latter can be obtained from this chain by imposing additional kinematic constraints. It is shown that for the introduced chain the dynamic equations can be derived in an explicit scalar form. The derivation is based on the D’Alembert principle, inertial coordinate system and direct utilization of the path matrix describing the system topology. An example of application of the results to a 2-DOF rigid-body manipulator is given.
STABILITY OF RATE GYRO IN A VEHICLE WITH UNCERTAIN ANGULAR VELOCITY AND ACCELERATION
Authors: Ge Zheng-Ming , Chen Heng-Hui
Published: April 2018

Using the Liapunov direct method, we study the stability of motion of a single-axis rate gyro mounted on a space vehicle which is simultaneously accelerating (ω)x(t)) with respect to the output axis and rotating (ωz(t)) about the spin axis of gyro. The analytical relations, which must be satisfied by the gyro parameters, are obtained for the asymptotical stability of the gimbal motion. In addition, by using a fourth-order Runge-Kutta numerical method, the trajectories of motions of a rate gyro are obtained to verify its stability.
INTERACTION OF WALL CONDUCTION WITH NATURAL CONVECTION FROM HEATED CYLINDERS IN A RECTANGULAR ENCLOSURE
Authors: Lacroix Marcel , Joyeux Antoine
Published: April 2018

A numerical study has been conducted for natural convection heat transfer for air from two vertically separated horizontal heated cylinders confined to a rectangular enclosure having vertical walls of finite conductances and horizontal walls at the heat sink temperature. The interaction between convection in the fluid filled cavity and conduction in the vertical walls is investigated. Results have been obtained for Rayleigh numbers, Ra, between 103 and 106, dimensionless wall-fluid thermal conductivity ratio α between 0.2 and 1000.0 and dimensionless wall thickness W between 0.25 and 1.375. Results indicate that the Nusselt number along the vertical wall-fluid interface is a complex function of both Ra and α. In general, the relative heat removal contribution by conduction in the wall through the top horizontal surface ηN decreases with Ra while that for the bottom surface ηs increases. For 0.2 ≤ α ≤ 5.0, ηs is nearly independent of Ra. Moreover, for Ra ≥ 105, 0.2 ≤ α ≤ 5.0 and 0.25 ≤ W ≤ 1.375, ηs is independent of α while ηN tends to zero with increasing α.
STATE-FEEDBACK CONTROL FOR PASSENGER RIDE DYNAMICS
Authors: Esmailzadeh E. , Taghirad H.D.
Published: April 2018

An analytical investigation of a half-car model with passenger dynamics, subjected to random road disturbance, is performed. Two different methods of defining the performance index for optimal controller design are proposed. Nondeterministic inputs are applied to simulate the road surface conditions more realistically. Results obtained illustrate that using an optimal state-feedback controller, with passenger acceleration included in the performance index, would exhibit not only an improved passenger ride comfort, but also, a better road handling and stability.
THE DEGENERATED SPHERICAL BURMESTER CURVES OF THE PP-P-P CASE
Authors: Lu Deng-Maw
Published: April 2018

In this paper an analytic method to investigate the degenerated spherical Burmester curves of the PP-P-P case is presented. (Provided that an instant centre and two poles associated with two rotation angles of a coupler are specified, a geometric construction is established to determine the spherical centre- and circle-point.) According to the geometric construction, the explicit equations of spherical Burmester curves for the PP-P-P case are thus derived, without the use of differentiation, but by using spherical cross ratio. By assigning proper parameter values to equations obtained, six types of degenerated spherical Burmester curves of the PP-P-P case are obtained directly, which include three different forms of the degenerated curve: (1) a point, (2) a great circle and a spherical Thales ellipse and (3) three great circles.
INTERNAL LOBE PUMP DESIGN
Authors: Mimmi G. , Pennacchi P.
Published: April 2018

The subject of this paper is the theoretical analysis of the internal lobe pump which is a particular type of positive displacement rotary pump. The main components of the pump are the rotors: usually the outer one is characterised by lobes with circular shape, while the inner rotor profile is determined as conjugate to the other.

For this reason the first topic presented here is the definition of the geometry of the rotors starting from the design parameters. The choice of these parameters is subject to some limitations in order to avoid inner rotor undercutting and to limit the pressure angle between the rotors.

Now we will consider the design optimisation. The first step is the determination of the instantaneous flow rate as a function of the design parameters. This allows us to calculate two performance indexes commonly used for the study of positive displacement pumps: the flow rate irregularity and the specific flow rate. These indexes are used to optimise the design of the pump and to obtain the sets of optimum design parameters.

Finally further considerations are presented regarding the calculation and the use of other performance indexes, the specific slipping and the rotor curvature, which are particularly suitable for giving more elements for the analysis of this case.
DYNAMIC DEFLECTION OF A CRACKED SHAFT SUBJECTED TO MOVING MASS
Authors: Parhi D.R. , Behera A.K.
Published: April 2018

The dynamic behaviour of a cracked shaft is greatly affected by the mass moving on it. Magnitude and the travelling velocity of the mass along with the position of the crack on the shaft are the major parameters, considered in this investigation. The local flexibility due to the crack is evaluated from the theory of fracture mechanics. Then the normal modes for the cracked shaft are found and are used for formulating the equation of the moving mass system. Runge-Kutta method is used to solve the differential equation for the dynamic deflection of a simply supported cracked shaft, subjected to a moving mass of varying magnitudes and velocities. Significant change in the dynamic behaviour of the shaft is observed from the above analysis.
LATERAL STABILITY ANALYSIS OF A RAILWAY TRUCK ON ROLLER RIG
Authors: ElMaraghy W.H. , Dukkipati R.V.
Published: April 2018

Generic linear models were developed of a freight car (with a characteristic North American three-piece truck) on tangent track. The models were developed using the generalized multi-body dynamics software MEDYNA.

Predictions were made of the theoretical linear model hunting (lateral stability) characteristics of the freight car, i.e., the critical speeds and frequencies, for five different configurations: (a) freight car on track, (b) the freight car’s front truck on the roller stand and its rear truck on track, (c) freight car on the roller rig, (d) a single truck on track and (e) single truck on the roller stand. These were compared with the Association of American Railroads’ field test data for an 80-ton hopper car equipped with A-3 ride control trucks.

Agreement was reached among all the analytical models, with all models indicating a range of hunting speeds of 2% from the highest to lowest. The largest discrepancy, approximately 8%, was indicated between the models and the field test data.
CURVATURE ANALYSIS AND SYNTHESIS OF SKEW GEAR SETS WITH KINEMATIC PARAMETRIC MODELS
Authors: Tsai Ying-Chien , Jehng Wern-Kueir
Published: April 2018

This paper proposes an effective and systematic method to design and synthesize skew gear sets in space. Based on the kinematics, the relationships of the location of instantaneous screw axes is derived, and then using the rules of coordinate transformation, the tooth surface geometry is developed. To maintain smooth conjugate action of motion transformation between the two meshing surfaces, a second order partial differential equation and its solution are proposed. According to Gaussian first and second forms, the geometric properties of the conjugate tooth surfaces are investigated. These include the principal curvature, the principal direction, the orientation of the contacting line at any contact point, and the relative series of curvature. In order to maintain smooth and silent operation at high speeds, it is important to improve gear performance with better contact, low specific sliding, low relative curvature, and better efficiency of lubrication. An example is presented to verify above mentioned procedures. The result of this work may be used to design better skew gear sets with arbitrary skewed axes.
FEM ANALYSIS OF AXISYMETRIC INDENTATION OF LAYER BONDED TO A RIGID FOUNDATION
Authors: Benabdallah H.S. , Boros I.E.
Published: April 2018

The finite element code ABACUS was used to study the behaviour of an elastic layer firmly attached to a rigid substrate when indented by a spherical elastic indenter, in terms of the induced contact stresses within its thickness and at its interface with the substrate. Various thicknesses of the layer as well as ratios of the respective stiffness of the indenter and layer were considered, when a concentrated load was applied along the centre of the indenter. The variation of the normal components of the stress at points along both indenter-layer and layer-substrate interfaces showed the development of large tensile stresses which could affect the performance of the layer. A noticeable effect of Ei/Ec, and h/R ratios on the maximum contact pressure was observed. A good model that represents this relationship is proposed. The evaluation of the maximum value of the variation of the shear stress along the layer-substrate interface has shown that a thicker and more rigid layer contributes to its increase. An empirical model that represents the relationship between this shear stress and the parameters studied was also developed, Finally, two empirical equations were formulated for a quick and accurate estimate of the half-width of the indenter-layer contact area, and the depth of the indentation.
SIMPLIFIED METHODS IN PLASTICITY, CREEP AND FRACTURE - SOME RECENT DEVELOPMENTS
Authors: Seshadri R.
Published: April 2018

Robust simplified methods are well suited for carrying out design evaluation of mechanical and structural components involving initial scoping, feasibility studies, screening of critical areas of large complex systems, and can be sometimes be the only recourse to an independent verification of the results of inelastic analysis. On the basis of no more than two linear elastic finite element analyses, lower bound limit load and reference stress are determined by the r-node method and mα multiplier technique. Furthermore, these quantities can be used to develop strategies for failure avoidance in mechanical components and structures.
FINITE ELEMENT ANALYSIS OF DYNAMIC CONTACT PROBLEMS
Authors: Xu S. , Yu S.D.
Published: April 2018

This paper presents a finite element analysis of dynamic contact between two solids with and without surface friction. The finite element solutions obtained using the linear complementary equations of incremental form for kineo-elastic displacements and contact stresses satisfy both normal boundary conditions and contact boundary conditions.

Three examples solving dynamic contact between two solids of different shapes are given. Numerical results indicate that there is excellent agreement between independent analytical solution and results obtained using CONTACT2D - a computer written in FORTRAN77 by the authors.
DISPLACEMENT ANALYSIS OF Ro-R-R-CP SPATIAL MECHANISMS WITH VECTOR ALGEBRAIC METHOD
Authors: Wong C.M. , Chan K.C. , Zhou Y.B.
Published: April 2018

This paper presents the displacement analysis of the three variants of a spatial kinematic loop containing 3R and 1CP joints using vector algebraic method. The closed-form input-output displacement equations of this mechanism are derived as forth-order polynomials. Analytical steps and expressions are laid out uniformly and simply.
SECONDARY POWER SYSTEM EVALUATIONS FOR ADVANCED AIRCRAFT
Authors: Lykins R. , Ramalingam M. , Donovan B. , Durkin E. , Beam J.
Published: April 2018

A computerized analytical program is being developed to help investigate the impact of power system requirements on aircraft performance. The program has an user interface that operates in MS-EXCEL, linking several subsystems analysis programs for execution and data transfer in the power systems analysis. The program presently includes an encoded propulsion engine cycle code, which allows the inspection of power extraction effects on engine performance. To validate the results of the encoded engine program, a study was conducted to investigate the separate effects of shaft power extraction and pneumatic bleed. The selected engine cycle was that for a standard tactical fighter, with a flight condition of varied altitude (sea level to 40,000 ft) and constant Mach Number (0.9). As expected the resultant data showed that the engine performance was more sensitive to pneumatic bleed than to shaft power extraction. The paper’s efficiency comparisons between shaft power and bleed air power helps indicate the higher efficiency for the power system of a more-electric type aircraft. Present efforts on the analytical interface are to incorporate a fuel thermal management analysis capability.
FREE CONVECTION FROM A WINDOW GLAZING WITH A VENETIAN BLIND: NUMERICAL MODEL DEVELOPMENT
Authors: Phillips J. , Naylor D. , Harrison S.J. , Oosthuizen P.H.
Published: April 2018

The present numerical study examines the influence of horizontal louvres (Venetian blinds) on the convective heat transfer from a vertical isothermal surface. A steady, laminar, two dimensional, conjugate conduction/convection solution to this problem has been obtained using the finite element method. Detailed comparisons are made with temperature field and local Nusselt number data obtained using a Mach-Zehnder Interferometer. Also, numerically predicted stream function contours are compared to streamlines obtained from flow visualization experiments. All results are obtained for Pr = 0.7, as the intended application of this study is for air. Results show that as the blind tip-to-plate spacing decreases, the difference between numerical solutions and experimental results increase. This suggests that radiation heat transfer may be a significant factor at smaller blind spacings.
A NUMERICAL AND EXPERIMENTAL STUDY OF A ONE-DIMENSIONAL SPACE BOUNDARY INVERSE HEAT CONDUCTION PROBLEM
Authors: Chen T-F. , Lin S. , Wang J.C.-Y.
Published: April 2018

Inverse Heat Conduction Problems (IHCPs) are not the same as direct heat conduction problems which are “well-posed”. The difficulty of the “ill-posed” IHCP is that a small error perturbation in the data will lead to a large error in the reconstructed solution. An inverse procedure for solving an IHCP should have the ability to handle the required information obtained from measurements containing noise. In the present work, a stable, accurate and reliable inversion solver is used with interior temperature measurements to predict surface temperatures at the both sides of a brick Numerical results in comparison with experimental data are presented.
ROUGH MACHINING FOR MULTI-SCULPTURED SURFACES
Authors: Vafaeesefat A. , EIMaraghy H.A.
Published: April 2018

This paper present a method to generate 3-axis NC programs for rough milling processes. A raster digitizing of the solid volume delimitated by sculptured surfaces to be machined is first created. This is accomplished by using the so-called Z-buffer created from a parallel projection of all surfaces. Conventional rendering software can be used to generate the Z-buffer. This volume is transformed into a 3-D mesh composed of “empty”, “full”, and “mixed” blocks. Machining is preformed from top to bottom in a sequence of horizontal cutting planes. At each level of planar machining, spiral routines are used to generate the tool path. The proposed method is valid for generating tool paths for general cavities bounded by arbitrary surfaces. One of the notable advantages of the proposed method is that the tool path generation is independent from the geometric description of bounding surfaces. An example is used to illustrate the approach and its advantages.
STUDY OF AN ENERGY DISSIPATING UNDER-RIDE GUARD USING HARDWARE-IN-THE-LOOP SIMULATION
Authors: Balike M. , Rakheja S. , Hoa S.V.
Published: April 2018

Hardware-in-the-Loop (HIL) simulation technique is implemented to analyze the performance characteristics of an energy dissipative under-ride guard system for enhancement of crashworthiness of lightweight vehicles involved in coillisions with heavy freight vehicles. The experimental setup, software and hardware interface, and the test methodology used to perform the HIL simulation are briefly described. The energy dissipating under-ride guard, while impacted by a car body, is analytically modeled incorporating nonlinearities due to asymmetric damping in compression and rebound, restoring properties and kinematics of linkages, using the principles of conservation of momentum and Lagrangian dynamics. The performance characteristics of the under-ride guard are evaluated under direct impact at different speeds, and the results obtained from the HIL simulation are compared with those derived from the nonlinear analytical model. The study revealed very good correlation between the analytical and experimental findings in terms of the amount of energy dissipated, acceleration level, rebound velocity and the magnitude of intrusion. An analysis of the results showed that significant portion of the kinetic energy can be dissipated by the under-ride guard.
POTENTIAL FLOW IN TUBE BANKS
Authors: Beale S.B.
Published: April 2018

This paper presents an analytical solution for potential cross-flow in doubly-periodic in-line and staggered tube banks. The solution, in the form of a power series for the complex potential, is consistent with the well-known solution for a single cylinder. Results are tabulated for in-line square, rotated square, and equilateral triangle geometries for pitch-to-diameter ratio 1.25 ≤ s/d ≤ 2. Pressure contours and flow nets are presented for selected cases, together with local pressure coefficient and wall velocity data.
DESIGN AND ANALYSIS OF A NEW SYMMETRICAL LINEAR ACTUATOR FOR HYDRAULIC AND PNEUMATIC SYSTEMS
Authors: Habibi S. , Goldenberg A.A.
Published: April 2018

In this paper, the performance of hydraulic actuation systems is analyzed and, it is observed that the performance of symmetrical (rotary) actuators is significantly better than their linear asymmetrical counterpart. The deficiency of linear actuators, resulting from their asymmetry, manifests itself as an undesirable dynamic effect related to the pressure characteristics of the actuator chambers. Subsequently, a new symmetrical design for linear actuators is proposed. In this design, the active areas of the two pressure chambers are made equal without the need for a dead-space on the fixed end of the piston as required by commercial double rod pistons. The paper discusses the benefits of this new design and demonstrates the advantages of its flow characteristics and its command input/force relationship. The theoretical observations are supported by experiments conducted on a large hydraulic robot. The Workmaster, formerly manufactured by Thorn EMI Robotics.
BUOYANCY EFFECTS ON UNSTEADY LAMINAR AND ROTATIONALLY SYMMETRICAL BOUNDARY LAYER
Authors: Öztürk A. , Ece M.C.
Published: April 2018

Initiai development of the laminar boundary-layer flow over an impulsively started translating and spinning isothermal body of revolution in the case of mixed convection is investigated. Velocity components and temperature are expanded in series in powers of time. Leading and first order functions are obtained analytically and second order functions are determined numerically. The general results are applied to a sphere to investigate the effects of density variations on velocity field and on the onset of separation. The buoyancy force is more effective for small rotational speeds and facilitates the onset of separation for opposing flow and retards it for aiding flow.
ON DETECTION OF DEFECTS IN BEAMS AND TRUSSES FROM DYNAMIC RESPONSES
Authors: Lukasiewicz S. , Palka K.
Published: April 2018

This paper presents an identification method to detect cracks and corroded members in vibrating structures. The mathematical identification procedure based on the least square technique uses the measured dynamic response of a structure as the source of information. The application of the Finite Element Method (FEM) for the representation of all constraints and model equations allows presentation of the identification process in a simple and very efficient mathematical form. Propagation of cracks and other failures of the members cause changes in the bending and axial stiffness of the members. One can detect the crack by observing the change in the bending stiffness caused by the closing and opening of the crack in two different configurations. The proposed identification method provides highly precise calculated results which allows detection of small changes in the bending stiffness of the members resulting from cracks and corrosion. The method was tested on simulated experimental data.
PURE SQUEEZE FILM BEHAVIOR OF LONG JOURNAL BEARINGS WITH COUPLE STRESS FLUIDS UNDER DYNAMIC LOADING
Authors: Lin Jaw-Ren , Yeon-Pun  , Kang Yuan , Cha Kuo-Chiang
Published: April 2018

On the basis of microcontinuum theory, a theoretical analysis of pure squeeze film behavior of journal bearings with couple stress lubricants operating under a dynamic load is presented. To account for the effects of couple stresses arising from the lubricant blended with various additives, the modified Reynolds equation governing the film pressure is obtained from Stokes equations of motion. Various bearing characteristics for long bearings are then calculated. According to the results obtained, the influence of couple stresses on the dynamic squeeze film motion is apparent and not negligible. Comparing with the Newtonian-lubricant case, the effects of coupe stresses provide and enhancement in the film pressure as well as a reduction in the velocity of the journal center; consequently, the maximum eccentricity ratio of the journal center is decreased. On the whole, the bearing lubricated with couple stress fluid signifies and improvement in the dynamic squeeze film performance and results in longer bearing life.
KINEMATIC AND DYNAMIC DESIGN OF FOUR-BAR LINKAGES WITH VARIABLE INPUT SPEED AND EXTERNAL APPLIED LOADS
Authors: YAN HONG-SEN , SOONG REN-CHUNG
Published: April 2018

A novel approach that integrates the kinematic synthesis, dynamic design and servo control in one design stage is presented for designing four-bar linkages with external applied loads. This approach satisfies kinematic design requirements and constraints and also attains trade-off of dynamic balance. By properly designing the speed trajectory of the input link, the balancing parameters of moving links and link dimensions of the given or desired mechanisms, the expected output motion characteristics and dynamic balancing performance are obtained. And, the input motion characteristics are designed with Bezier curves. Optimization is aided to find out optimal design parameters for achieving kinematic and dynamic design requirements and constraints. The speed trajectory of the input link could be generated by a servomotor. Examples are given to demonstrate the feasibility of this approach.
ON THE USE OF NUMERICAL OPTIMIZATION TO MAXIMIZE THE CRITICAL VELOCITY OF A SIMPLE RAIL VEHICLE
Authors: Baumal A. , McPhee J.
Published: April 2018

It is shown how numerical optimization methods can be used to obtain design parameters for a simple rail vehicle that maximize the “critical velocity”, the speed at which the response becomes unstable. To automatically calculate the critical velocity for a given set of suspension design parameters, a unique approach using gradient-based optimization is employed. The critical velocity was increased by 22 percent by modifying the suspension and inertia properties by only 10 percent The design results from the genetic algorithm are consistent with previous observations in the literature.
RECIRCULATION OF CONFINED VARIABLE DENSITY TURBULENT JETS
Authors: Benaissa A. , Bardon M.F. , Gauthier J.E.D. , Anselmet F. , Ruffïn E.
Published: April 2018

An investigation of recirculating characteristics of circular turbulent confined jets with large density variations is presented. This numerical study aims at testing analytical predictions associated with the Craya-Curtet number. It investigates also its effect on the dynamic field and recirculation. It appears that for different density (He-air, CO2-air) and geometry ratios, the non-isothermal Craya-Curtet number [1] is not sufficient to describe the flow pattern or predict its recirculation. Depending on the momentum, aspect and density ratios of the flow, the centre of the recirculating flow (the eye) tends to reach the initial (non-self-preserving) region of the jet and influences the development of the jet. As a consequence, predictions are not in agreement with theory. The reason is that initial conditions do not satisfy the hypothesis used in the prediction of recirculation theory. Calculations are performed in three configurations: CO2, air and He. These configurations are fully developed pipe jets evolving in an air secondary turbulent flow. Validations are performed using experimental data [2] obtained in similar configurations for the three gases.
DYNAMIC LOADS ON THE DRIVE SHAFT BEARINGS OF A SWASH PLATE AXIAL PISTON PUMP WITH CONICAL CYLINDER BLOCK
Authors: Khalil M.K. Bahr , Svoboda J.V. , Bhat R.B.
Published: April 2018

Variable displacement swash plate pumps are invariably used under conditions that involve heavy loads with variable flow demands. Swash plate pumps with conical cylinder blocks are now widely used in view of their good static and dynamic characteristics. However, drive shafts of these pumps experience dynamic loads due to the pressure forces transmitted through the body of the conical cylinder block to the supporting bearings. Dynamics of such rotating mechanism are quite interesting and should be considered in the design process of the drive shaft and the supporting bearings. A mathematical model is formulated for a 9-piston swash plate pump with conical cylinder block in order to evaluate the dynamic loads on the drive shaft. Results are presented and discussed.
AN APPROACH TO DESIGN A QUADRUPED WALKING MACHINE WITH A SINGLE ACTUATOR
Authors: Yan Hong-Sen , Chen Yu-Gang
Published: April 2018

This article presents a systematic approach to developing a quadruped walking machine with a single degree-of-freedom(DOF) and with statically stable locomotion. An existing path generator, based on design requirements and constraints, is selected and synthesized into a leg mechanism with a suitable foot path. The crank of the leg is then driven by a two-speed control apparatus to shift the moving speed of the foot point both in support phase and transfer phase. This variable speed control of the crank increases the value of duty factor and improves the stability of locomotion. A prototype walking machine with 8-link type legs is constructed and proved that this approach is feasible for designing various types of single-DOF legged vehicles.
KINEMATIC ANALYSIS OF ROLLER DRIVES
Authors: SHEU Kuen-Bao , LAI Ta-Shi
Published: April 2018

The roller drive is an epicyclic gearing that consists of both the planet gear and the annular sun gear with rollers as its teeth. The roller drive thus has the advantages of easy manufacturing and low cost, and also has attractive attributes including high speed reduction ratio, compact size, and light weight as an epicyclic gearing. In this paper, a mathematical modeling for the kinematic analysis based on the vector loop approach is developed. The position, velocity, and acceleration analyses for the roller drive are performed. Furthermore, an experimental test verifying the analysis results is achieved. The analysis results show that only a single pair of teeth is meshed during gearing. It also shows that the values of gear ratio are inherently fluctuated corresponding with the number of ring gear rollers. This undesirable fluctuation can be minimized if the selected values of the design parameters satisfy a specific four-linkage constraint.
POSITION STABILITY FOR PHASE CONTROL OF THE PREISACH HYSTERESIS MODEL
Authors: Cruz-Hernández Juan Manuel , Hayward Vincent
Published: April 2018

Many systems with hysteresis are adequately represented by the Preisach model. Hysteresis in these systems can be very effectively reduced using the “phaser”, an ideal frequency domain operator, in a feedback connection. The position stability of this type of control has not yet been established in spite of the experimental evidence that the resulting systems are stable. This paper shows the dissipativity for the relay operator, for the Preisach model, and then for the lead approximation to the phaser. We then give a proof of stability for the feedback connection of this phaser approximation with systems represented by the Preisach model of hysteresis.
DIGITAL REDESIGN OF A STEPPING-MOTOR DRIVER IN THE PRESENCE OF COMPUTATIONAL DELAYS AND DISTURBANCES
Authors: Shimamura Hideaki , Hori Noriyuki
Published: April 2018

A method of digital redesign that can take computational delays and disturbances into account is presented and applied to an industrial analog driver for stepping motors. The method is based on the so-called Plant-Input-Mapping (PIM) method, which guarantees the stability for any non-pathological sampling interval and is extended to the case where computational delays are present. The delay, which does not have to be integral multiple of the sampling period, is considered to be a part of the plant so that adverse effects of the delay on the digital controller performance can be taken into account. Since the effects of disturbances in the motor should also be dealt with in the driver, modifications to the PIM are incorporated such that the characteristics from the disturbance to the plant-input can be adjusted without affecting those from the reference input. The performance of the resulting PIM method is investigated experimentally and found to be very close to that of the analog original, which cannot be recreated using the commonly used Tustin’s method at a sampling rate suitable for commercial production.
A TUTORIAL PRESENTATION OF ALTERNATIVE SOLUTIONS TO THE FLEXIBLE BEAM ON RIGID CART PROBLEM
Authors: Langlois R. G. , Anderson R. J.
Published: April 2018

A classical planar problem in forward flexible multibody dynamics is thoroughly investigated. The system consists of a damped flexible beam cantilevered to a rigid translating cart. The problem is solved using three distinctly different conventional approaches presented in roughly the chronological order in which they have been applied to flexible dynamic systems. First, a modal superposition formulation based on Bernoulli-Euler beam theory is developed. Second, an alternative solution is developed drawing exclusively on methods for rigid body dynamics combined with a knowledge of the theoretical modal behaviour of continuous beams. Third, a formulation based on the conventional finite element method using four-degree-of-freedom planar beam elements is adapted to include the rigid body motion of the cart. The relative merits of the three formulations are discussed and numerical simulation results generated using each of the three formulations are compared with each other and with a solution from a general-purpose flexible multibody dynamics formulation that is briefly outlined. The relative accuracy and efficiency of the methods and the challenges associated with generalizing each formulation are discussed.
A TEST RIG FOR EXPERIMENTATION ON FAULT TOLERANT CONTROL AND CONDITION MONITORING ALGORITHMS IN FLUID POWER SYSTEMS: FROM DESIGN THROUGH IMPLEMENTATION
Authors: Sepehri Nariman , Karpenko Mark , An Liang , Karam Suha
Published: April 2018

This paper reports the relevant aspects of a novel experimental test facility for research on fault tolerant control design and condition monitoring of fluid power systems recently constructed at the University of Manitoba. Common faults and their effects on the operation of valve controlled hydraulic actuators, such as those found in aerospace applications, are summarized first. The manuscript then presents the main features of the test rig and the modifications made to simulate various faults. The design also incorporates techniques to easily simulate load conditions from viscous forces to complex dynamic loads. The significance of the test rig in the development of advanced condition monitoring and fault tolerant control strategies is also illustrated by the presentation of the results of some recent research work conducted using the test facility. By sharing their experience with other investigators in this active area of fluid power research, the authors hope to establish a national benchmark test facility for the objective evaluation of state-of-the-art monitoring and control strategies for fluid power systems.
THE USE OF FUZZY LOGIC IN THE TAGUCHI METHOD FOR THE DETERMINATION OF THE TOLERANCE OF A SIX-BAR HINGE MECHANISM
Authors: Chen Fu-Chen , Huang Hsing-Hui
Published: April 2018

In this paper fuzzy logic was applied to the Taguchi method to design the dimensional tolerances of a six-bar hinge mechanism with multiple performance characteristics (MPC). A fuzzy logic system was used to determine the relationship between the S/N (signal to noise) ratios of the position and the angle error for assessing the level of importance of each control factor in the hinge mechanism. The contribution of each control factor to the variations was also quantified through the response table and response diagram and the key dimensions found to significantly affect the quality of the mechanism were r4, β, r1 and r5, which contributed 67.77% of the total product variation. It followed therefore that in order to improve the quality of the mechanism the tolerance of these factors must be tightened. Through a series of confirmation experiments, it was revealed that tightening the tolerance resulted in an increase in the multiple performance index (MPI) by 0.094, which was an increase of 19.87% of the initial value.
FORCE-AND-MOTION-TRANSMISSION EVALUATION IN SPATIAL MECHANISMS
Authors: Chen Chao , Angeles Jorge
Published: April 2018

We propose a generalized transmission index for spatial mechanisms, based on the virtual coefficient between the transmission wrench screw and the output twist screw. Compared with other indices, ours is well defined in any case and able to evaluate the force transmission quality more precisely. We apply this index to mechanisms with higher pairs and show that the pressure angle is a special case of our index.
FORCE-UNCONSTRAINED POSES OF THE 3-PRR AND 4-PRR PLANAR PARALLEL MANIPULATORS
Authors: Firmani Flavio , Podhorodeski Ron P.
Published: April 2018

Force-unconstrained (singular) poses of the 3-PRR planar parallel manipulator (PPM), where the underscore indicates the actuated joint, and the 4-PRR, a redundant PPM with an additional actuated branch, are presented. The solution of these problems is based upon concepts of reciprocal screw quantities and kinematic analysis. In general, non-redundant PPMs such as the 3-PRR are known to have two orders of infinity of force-unconstrained poses, i.e., a three-variable polynomial in terms of the task-space variables (position and orientation of the mobile platform). The inclusion of redundant branches eliminates one order of infinity of force-unconstrained configurations for every actuated branch beyond three. The geometric identification of force-unconstrained poses is carried out by assuming one variable for each order of infinity. In order to simplify the algebraic procedure of these problems, the assumed or “free” variables are considered to be joint displacements. For both manipulators, an effective elimination technique is adopted. For the 3-PRR, the roots of a 6th-order polynomial determine the force-unconstrained poses, i.e., surfaces in a three dimensional space defined by the task-space variables. For the 4-PRR, a 64th-order polynomial determines curves of force-unconstrained poses in the same dimensional space.
USING ARTICULATED BODY ALGORITHM WITHIN SLIDING-MODE CONTROL TO COMPENSATE DYNAMIC COUPLING IN UNDERWATER-MANIPULATOR SYSTEMS
Authors: Soylu Serdar , Buckham Bradley J. , Podhorodeski Ron P.
Published: April 2018

A control scheme is presented for compensating dynamic coupling between an underwater robotic vehicle (URV) and a manipulator. During task execution the torques commanded at the manipulator joints lead to reactions at the junction point of the manipulator and vehicle. These reactions disturb the vehicle position and orientation and are the source of the vehicle-manipulator coupling. In many underwater robotic vehicle-manipulator (URVM) applications, the URV serves as a base while the manipulator performs a required task. Therefore, it is necessary to hold the URV as stationary as possible. In the current work, Slotine’s sliding mode control approach is used to compensate the dynamic effect of the underwater manipulator on the URV. The articulated body (AB) algorithm is used both for the time-domain simulation of the system and for the dynamic equations within the model-based sliding-mode controller. The AB algorithm is preferred for the time-domain system simulation, as it provides a computationally efficient simulation scheme. Finally, a three DOF manipulator mounted on a URV is considered, and results of time-domain numerical simulations of the proposed control scheme are presented.
A SLIP MODEL FOR THE SPHERICAL ACTUATION OF THE ATLAS MOTION PLATFORM
Authors: Holland J.B. , Hayes M.J.D. , Langlois R.G.
Published: April 2018

The Atlas platform represents a novel six degree-of-freedom motion platform architecture. Orienting is decoupled from positioning, and unlimited rotations are possible about every axis. The decoupling is accomplished by fixing a three degree-of-freedom spherical orienting device, called the Atlas sphere, on a gantry with three orthogonal linear axes. The key to the design is three omni-directional wheels in an equilateral arrangement, which impart angular displacement to a sphere, providing rotational actuation. The free-spinning castor rollers provide virtually friction-free motion parallel to each omni-wheel rotation axis creating the potential for unconstrained angular motion. Since the sphere directly contacts the omni-wheels, there are no joints or links interfering with its motion, allowing full 360° motion about all axes. However, the kinematic constraints are non-holonomic. This paper explores the slip at the interface between each omni-wheel and the Atlas sphere. A kinematic slip model is presented, introducing the slip ratio, which is the ratio of the kth omni-wheel’s transverse velocity component, S⊥k, which is perpendicular to the free-spinning castor wheel axis, and the tangential velocity component, Stank, which is perpendicular to the omni-wheel driving axis, parallel to the tangential velocity vector, Vk. The long-term goal is to incorporate the slip model into a control law for position level control of the sphere. Two illustrative examples are given.
ON NONLINEARITY CONTROL OF CNC FEED DRIVES
Authors: Shahin Rami M. , ElMaraghy Waguih H. , ElBeheiry EISayed M.
Published: April 2018

A Unified Reconfigurable Open Control Architecture (UROCA) aims at unifying the reconfiguration aspects and managing the interaction amongst the different operating levels of individual machining control systems that are likely to perform in reconfigurable manufacturing systems. The hierarchical control structure of UROCA demands the usage of a supervisory control scheme in order to manage operations of supervisory and servo controllers altogether into a reconfigurable control process. The main function of the supervisory unit is to serve as a switching/reconfiguring logic amongst different available controllers, according to need, in order to maintain motion output within the permitted limits. Due to backlash, efficiency of machine tools will be undesirably turned down causing higher vibrations, lower contouring accuracy, and may draw the whole system into instability region. A Switching control scheme designated to manage the control process where two different controllers with two different control functionalities, acting differently in two vital zones - one of them where the backlash lies, and the other when moving past the backlash - is the main topic of this paper. The proposed switching schemes emphasize a reconfiguration aspect on the control process level for machine tools as perceived, investigated and resolved by the physical and control layers located at the deliberative part of the UROCA architecture.
LOAD AND STRESS ANALYSIS OF CYLINDRICAL WORM GEARING USING TOOTH SLICING METHOD
Authors: Falah A.H. , Elkholy A.H.
Published: April 2018

A method for the determination of load and stress distributions of the instantaneously engaged teeth of cylindrical worm gears is represented in this paper. The method is based on the assumption that both the worm and gear can be modeled as a series of spur gear slices. The exact geometry and point of load application of each slice depends on its location within the mesh. By calculating the applied load and stress for each slice, the same can be determined for the entire worm gear set. The method takes into consideration tooth stiffness variation from root to tip, tooth bending deflection, local contact deformation, tooth foundation deformation and, the influence of gear parameters on load and stress. Calculated results were found to be in agreement with experimental and analytical ones obtained from literature under given operating conditions.
LASER HEATING AND THERMAL STRESSES TIME EXPONENTIALLY HEATING PULSE CASE
Authors: Yilbas B.S. , Naqvi I. Z.
Published: April 2018

Model studies of laser heating process minimize the experimental time and cost and give insight into the laser workpiece interaction mechanism. In the present study laser pulse heating is modelled and the governing equation of heat transfer, including phase change process, and thermal stresses are solved numerically using a control volume approach. In order to account for the time variation of the laser heating pulse, time exponentially varying pulse intensity is employed in the analysis. Since the heating conditions are considered to be axisymmetric, two dimensional case is introduced in the analysis. The temperature and stress fields are simulated for steel. It is found that temperature level attains considerably high values in the melt zone and pulse parameter (β/γ) with small values (1/2) results in large evaporated zones. Equivalent stress level increases rapidly in the region close to the melt surface and two stress peaks are developed in the radial direction. The location of stress peaks remains same with progressing heating period; however, the magnitude of second peak reduces with advancing heating periods.
COUPLED FINITE ELEMENT ANALYSIS OF A PIEZO-CERAMIC FORCE TRANSDUCER
Authors: Shiari Behrouz , Wild Peter M.
Published: April 2018

The coupled finite element method is used to design a novel miniaturized piezoelectric force transducer for the pulp refiners. The analysis focuses on a proposed transducer design using commercially available piezoelectric sensing element and a steel assembled housing. The software ANSYS was used to create a finite element model in order to improve transducer electromechanical behaviour. The primary goal of modeling is to design a transducer with a frequency response higher than a lab-scale refiner. Thus, modal and harmonic responses of the transducer model are studied. A coupled electromechanical model is used for prediction the output of the transducer. In order to enhance the performance of the transducer, the design is studied with respect to output magnitude and a flat frequency response. The modeling results are used for fabrication a prototype force transducer. The experimental results showed good agreement with the modeling.