Showing papers in "Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing in 1993"

Evaluation of the Strength of Carburized Spur Gear Teeth Based on Fracture Mechanics

Abstract: A method is developed to simulate fatigue crack growth in a carburized gear tooth based on two-dimensional linear fracture mechanics. In the simulation, the stress intensity factor is calculated by means of a finite-element method (FEM) which takes into account the effect of residual stress. The fatigue crack growth rates in the case layer are estimated experimentally, and they are expressed by an experimental formula. A strength evaluation procedure for carburized gears is then proposed on the basis of the developed method of simulation. In the procedure, the critical length of the initial crack which is obtained from the fatigue strength is assumed to be equal to the crack length evaluated from the threshold stress intensity factor, and the basic load capacity is estimated. The critical lengths are evaluated for variously treated gears and illustrated as a function of surface condition.

Recent Researches on Active Suspensions for Ground Vehicles

Abstract: The increasing demand for safety and ride comfort, especially at high speeds, has led to the development of actively controlled suspensions in ground vehicles such as automobiles, railways and maglev vehicles. The active or semi-active suspension replacing passive elements with controlled actuators or variable elements can theoretically and practically improve vehicle vibration isolation properties, dynamical responses of pitch, roll and yaw motions, and road holding and guideway tracking performances. This paper reviews basic suspension problems, suspension control types, theoretical approaches to active suspension control and applications to practical systems.

Automation of Polishing Work by an Industrial Robot : System of Polishing Robot

Abstract: This study deals with the automation of polishing work by use of an industrial robot with 6 degrees of freedom. Since polishing work, which takes much time, requires experience, patience and skill, it is manually performed by skilled workers. This study aims at rationalizing such difficult polishing work by introducing a robot and CAD technology. The arm of the robot can be equipped with two kinds of polishing tools, i.e., a rotational tool or an ultrasonic vibrational one, to cope with various cofigurations of the workpiece surface. In addition, the system allows collision-free polishing paths derived from the CAD system to be expressed in the robot coordinate system by use of a touch sensor. The system is found to be effective for obtaining a smooth workpiece surface, based on several experimental results.

Study of Ultraprecision Orthogonal Microdiamond Cutting of Single-Crystal Copper

Abstract: The results of experimental study of ultraprecision orthogonal microdiamond cutting of single-crystal copper are presented. The orthogonal cutting tests were carried out on an ultraprecision fly-cutting machine at various nominal depths of cut from 3.0μm down to 0.01μm (10nm). The machinability in microcutting and the influence of crystal orientation on the microcutting process are discussed from the standpoints of chip formation, cutting force and surface integrity. It is confirmed that continuous chips are formed under all cutting conditions examined. The magnitude of the cutting force and the shear angle are substantially influenced by the crystal orientation at depths of cut of 1μm or more, while they are not notably influenced with depths of cut below 1μm.

A Wall-Climbing Robot Using Propulsive Force of a Propeller : Mechanism and Control in a Mild Wind

Abstract: Use of a wall-climbing robot for such purposes as rescue, wall inspection and fire-fighting in high-rise buildings has been anticipated for a long time. Three different types of models have been developed in our laboratory. The present one can move on a wall using the thrust force of propellers, which are inclined slightly toward the wall to produce the frictional force between the wheels and wall surface. It has a long and lightweight body for climbing an irregular wall surface, and its mechanism and the control system by which it can move in calm or mild wind conditions are discussed briefly.

The Operational Space Framework

Abstract: Robot dynamics has been traditionally viewed from the perspective of a manipulator's joint motions, and significant effort has been devoted to the development of joint space dynamic models and control methodologies. However, the limitations of joint space control techniques, especially in constrained motion tasks, have motivated alternative approaches for dealing with task-level dynamics and control. The operational space formulation, which falls within this line of research, has been driven by the need to develop mathematical models for the description, analysis, and control of robot dynamics with respect to task behavior. In this article, we review the operational space task-level models and discuss the various control methodologies that have been developed in this framework. These include : the unified motion and force control approach ; the notion of dynamic consistency in redundant manipulator control ; the reduced effective inertia property associated with macro-/mini-manipulator systems and the dextrous dynamic coordination strategy proposed for their control ; and the augmented-object model for the control of robot systems involving multiple manipulators.

Dynamic Analysis of a Rotor-Journal Bearing System with Large Dynamic Loads : Stiffness and Damping Coefficient Variations in Bearing Oil Films

Abstract: This paper describes the variations in stiffness and damping coefficients in bearing oil films under the influence of large dynamic loads. A rotor-journal bearing system in which large dynamic loads act on the rotor is nonlinear, so it is analyzed as a coupled problem of the equations of motion for the rotor combined with Reynolds equations for all the bearings. By making use of the displacements and velocities of the rotor center obtained through analysis, the stiffness and damping coefficients have been numerically calculated as an unsteady state along the locus of the rotor center. The variations in these coefficients over one rotor revolution are shown for the journal bearings in a rotary compressor. Our results demonstrate that most of the coefficients for all the bearings vary by more than one order of magnitude, and that oil film nonlinearities seriously influence the rotor motion.

Infeed Grinding of Straight Conical Involute Gear

Abstract: The greatest possibility of the conical involute gear is in the use of straight conical involute gears in place of bevel gears. However, the key for realizing this usage is to establish the method of grinding straight conical involute gears which have a comparatively large cone angle. In this study, three grinding methods to finish such a gear are developed : Niles-type infeed ginding, table sliding infeed grinding, and inclining work-arbor infeed grinding. The principles and the available machines are described, the test results are discussed, and it is concluded that the most practical method is table sliding infeed grinding.

Position Control of a Flexible Arm Using a Dither Signal

Abstract: In this paper, we present the feedback control of a one-link flexible arm having reduction gear friction. Tip position control was very difficult when large friction was treated as an equivalent viscous friction. Experiments showed that tip position feedback control was possible using the dither signal. We investigated the influence of the dither amplitude on linearizing the nonlinear friction and the response of feedback control. The acceleration signal from the accelerometer at the arm tip, like the signal from the strain gauge at the arm root, could use feedback control for the fundamental vibration mode.

An Analysis Using Offset Curves for Profiles, Manufacturing and Errors of Plane Cams

Abstract: This paper presents a convenient analysis method for plane cams. This method is based on the principle of the offset curve of a plane curve and has the features of conceptual clarity and simplicity of computation. Almost the same methods can be used for the calculation of both the cam profile and the tool coordinates in manufacturing and for the influence analysis of the errors which occur in the manufacturing and assembling of cams, because the cam contour, the pitch curve and the path of the tool center are the offset curves each other. The validity of the method is confirmed with some examples. This method can be effectively applied for CAD/CAM of plane cam mechanisms.

Repetitive Control for a Class of Nonlinear Systems

Abstract: A repetitive control scheme which is applicable to a class of nonlinear systems with periodic reference signals is proposed. The nonlinear terms in the systems are assumed to be polynomially bounded. Sliding mode control is applied to an augmented system in which an integrator and a repetitive controller are combined in order to obtain a linear input-output relation. The stability condition for the repetitive control system realized by the proposed method is derived. It is shown that this system satisfies the internal model principle for a given frequency bandwidth. The frequency bandwidth is given by the stability condition. An illustrative example is given.

Stability of a Speed Ratio Control Servo-mechanism for a Half-Toroidal Traction Drive CVT

Abstract: A continuously variable power transmission, CVT, has potential for the improvement of fuel economy and cruising comfort as an automotive propulsion system. A traction drive CVT changes its speed ratio by the control of side slip force on the Hertzian contact. This mechanism has the features of equal torque transmission of every rolling element and low wasted power for the speed ratio change, but sometimes falls into self-excited vibration at higher rotating speed. This paper describes the principle of the speed ratio changing mechanism of a half-toroidal traction drive CVT and offers a compensatory measure for stabilizing the electrohydraulically operated speed ratio control servomechanism.

Basic Study on Cutting Forces in Gear Cutting : Theory of Cutting with Two Continuous Symmetrical Cutting Edges

Abstract: In hobbing, the hob cutter has many cutting teeth, and moreover each hob tooth has three cutting edges. When a hob cuts a gear, each of the cutting edges of one tooth produces one chip simultaneously. Then the chips resulting from those cutting edges interfere with further cutting, and the specific cutting forces become larger than those in orthogonal cutting. In this paper, the interference of chips is theoretically investigated. A basic and simple model of chip interference is the cutting of full-depth or non-full-depth triangular cuts. Thus, the specific cutting forces in non-full-depth triangular cuts made with a point nose straight tool are theoretically investigated in terms of various included angles. The result shows that the specific cutting forces become large when the included angle of the tool is small. The specific cutting forces with an included angle of 90 degrees are about 1.3∼1.35 times those produced by a flat tool.

Digital Control of Electrohydraulic Servo System Operated by Differential Pulse Width Modulation

Abstract: In the preceding papers, the authors proposed a new method of differential PWM for a hydraulic actuator operated by two 3-way solenoid valves. An arbitrary pulse width of the pressure difference across both sides of the actuator piston was realized by adjusting the switching time of each valve. The actuator operated by differential PWM shows good linearity as a control element, achieving accurate positioning. This study, as an application, deals with a hydraulic servo system composed of a 4-way spool valve and a load cylinder, where the spool valve is driven directly by the differential PWM actuator. The servo system is designed based on the optimal regulator method of the state variable model. The system performance is investigated through simulations and experiments. Consequently, it is shown that the actuator, operated by differential PWM, plays the role of a linear control element, and that the servo system is well designed by the optimal regulator.

Design Optimization of Spirally Grooved Thrust Air Bearings for Polygon Mirror Laser Scanners

Abstract: Polygon mirror laser scanners have been widely used in computer peripheral equipment and office automation systems, and improvement in scanning quality has been desired. In light of this, the use of self-acting air bearings has been recommended in spindle design to realize superior performance in terms of rotational speed and rotational errors. This study concerns the analysis of characteristics of spirally grooved thrust air bearings. Namely, it reports the rigidity, load capacity, power loss and critical damping factors. Employed in this study are the finite element method (FEM) and the computer simulation method in order to obtain a numerical solution to the Reynolds equation. Based on calculation results, the load characteristics and the effects of various design parameters of the bearing are discussed, and optimization principles for designing the bearing are proposed. The proposal may be summarized as follows. ( 1 ) The bearing rigidity and load capacity are closely related to the spiral groove width, depth, length in the radial direction and spiral groove pump-in angle, and the number of grooves should be as large as possible. ( 2 ) Decrease in the bearing clearance and increase in the bearing outer radius together achieve the best damping characteristics.

Dynamic stability criterion for reed valves in refrigerant compressors

Abstract: One of the most significant vibration sources of higher-frequency noises in refrigerant compressors used for air conditioners or refrigerators is the reed valve which controls the refrigerant gas flow from the discharge port. In order to examine the higher-frequency vibrations of the reed valve exposed to compressed gas flow, we conducted a vibration test for a simple axisymmetrical model consisting of a valve, valve plate, cylinder and piston. First, compressed air entered the flow chamber through a capillary tube at the piston center, and the valve was excited to induce a forced vibration over as wide a frequency range as possible. Then, the fluid pressure in the flow chamber was measured for different cylinder volumes to determine the amplitude and the phase lag relative to the valve vibration, thus making it possible to obtain a dynamic stability criterion for self-excited vibration of the reed valve. Secondly, a free vibration test was performed on the reed valve to verify that the reed valve actually experiences self-excited vibration when the dynamic stability criterion obtained from the forced vibration test is not satisfied. In addition, the vibration frequency and self-excitation level of the reed valve were examined.

Rotational Vibration of a Helical Gear Pair with Modified Tooth Surfaces : Modified Tooth Surface and Its Equivalent Tooth Profile

Abstract: Modified tooth profiles and their deflections cause a gear pair to contact away from the theoretical line of action and result in transmitting inconstant rotational motion. Those actual points of contact and their tooth actions can be described using tangential-polar coordinates by giving the measured single flank error and the tooth-spring constant. From this point of view, the rotational motion is analyzed to obtain the dynamic increment of tooth load in this series of papers. In this first paper, the engagement between modified tooth surfaces of a helical gear pair is replaced with that between eqivalent tooth profiles of a spur pair with the same single flank error. The equivalent profile is expressed algebraically as an involute curve with an instantaneous base circle whose radius varies, the tooth actions of which are analyzed geometrically. By giving the tooth-pair spring constant, the equivalent profile under load, its instantaneous base circle and the equivalent tooth-pair spring constant in the region of both single- and multiple-tooth-pair mesh are also analyzed.

Evaluation of Limiting Shear Stress of Lubricants by Roller Test

Abstract: A method for determining the parameters of the rheological properties which express the model of the limiting shear stress of lubricants is proposed. The relationships between the traction coefficients of the roller tests and the mean film temperature rises of lubricants are calculated. The maximum traction coefficients are revised to those of the isothermal condition by the traction coefficient-temperature relationships and analyzed using an approximate formula which estimates a maximum traction coefficient based on the limiting shear stress. The zero pressure value of limiting shear stress To and slope of the limiting shear stress-pressure relationship m are presented for two traction fluids Santotrac 50 and Daphne 7074 at temperature 313 K. Maximum traction coefficient and limiting shear stress at high temperature are predicted using the traction coefficient-temperature relationships.

Development of High-Concentration Lapping Discs with Low Bonding Strength and their Application to Mirror Finishing of Brittle Materials

Abstract: High concentration of active grains and low bonding strength are important features for increasing the removal rate and reducing the subsurface damage in lapping of brittle materials. Thus, high-concentration lapping discs with low bonding strength have been developed. First, the finishing characteristics using the lapping discs were investigated, varying the concentration of bonding agents and thereby determining that a high removal rate could be obtained at a low concentration. Next, soft abrasives, which may undergo a mechanochemical reaction with workpiece materials, were adopted as the abrasive material of the lapping discs, and colloidal silica which may undergo a chemomechanical reaction with workpiece materials was applied as a coolant in finishing. A mirror-surface finish of less than 10 nm Ra was obtained for various brittle materials, and a smooth-surface finish with no dropout of grains was achieved for aluminum nitride substrates.

New Measuring Method of Circular Movement of NC Machine Tools : Development of Alternative Method for Standardization

Abstract: In this paper, we describe an alternative method based on a new idea for measuring the circular movement of machining centers. ISO has employed three methods for the acceptance tests of machine tools : the first is a rotating one-dimenional probe method, the second utilizes a two-dimensional probe and a master circular ring, and the third utilizes a kinematic ball bar. At present, it is necessary to develop an alternative method with no relation to the latter two methods because their patents are pending. We have developed an alternative method by improving the rotating one-dimensional probe method. The newly developed method is superior to the other two methods ; the rotation angle can be detected and the rotation radius is variable. The effectiveness of the developed method is confirmed experimentally.

A Robustness Measure of Eigenvalue Distribution in Complementary Regions for Perturbed Systems

Abstract: In this paper, we present some results on robustness of eigenvalue distribution in specified complementary regions for perturbed systems. If some eigenvalues of the nominal system are located in a specified region, the proposed sufficient conditions guarantee that the same number of eigenvalues of the perturbed system lie inside the same region. The characteristics of a linear time-invariant system are influenced by the eigenvalue location of the system matrix. Due to uncertainty or parameter variation, all mathematical descriptions of dynamic systems are approximate models at best. The effect of uncertainty will move the eigenvalues of a real system away from the designed ones. Therefore, it is significant to guarantee that the same number of eigenvalues of the perturbed system lie inside the same region as that of the nominal system. By the analysis of eigenvalue distribution, we can explore the locations of dominant eigenvalues, specified eigenvalues or even individual eigenvalues of perturbed systems. Consequently, more properties of perturbed systems such as stability margin, performance robustness and so on can be examined. The proposed theorems can be applied to both continuous- and discrete-time systems. In addition, the analysis of stability robustness can be dealt with as a special case in our study. Two examples are given to show the applicability of the proposed theorems. Finally, some conclusions are presented.

Communication Architecture for Cellular Robotic System

Abstract: This paper describes one approach for the communication architecture of a "cellular robotic system (CEBOT)", which consists of a large number of autonomous robotic units or "cells." The strategy is based on the selection of a "master cell, " where the master cell is assumed as a coordinator in the system. The selection is made using "network energy" as an evaluation function, which is proposed in this paper and is based on the probability of the information flow in the network. We describe a mastering method which implies the determination of a master cell, and show the mastering method using the local sensitivity of the network energy, called "local energy sensitive estimation." The local sensitivity is defined as local network energy which takes only the influence of a cell adjacent to the master cell into consideration. The search for a master cell can be performed effectively. We show the simulation results of mastering.

Studies on the Unsteady Boundary Layer on a Flat Plate Subjected to Incident Wakes. Forced Transition Models of the Boundary Layer.

Abstract: Detailed studies are conducted to investigate the effects of the incident wakes generated by rotating circular cylinders on the characteristics of the transitional boundary layer developing on a flat plate. In this report, the primary concern is to measure the time-averaged heat transfer distribution along the flat plate under several conditions of wake characteristics and cylinder speeds. The obtained data are then utilized in the development of a simple but accurate model for an intermittency factor of the transitional boundary layer subjected to the incoming wakes. Two transition models, the Mayle-Dullenkopf model and a geometrical intermittency factor model, i. e., a modified Pfeil model, are employed for comparison with the measured heat transfer data, and it is found that the latter model, which only considers evolution of the turbulent spot in the space-time domain, yields a better prediction.

Isothermal Simulation with Decoupled Losses for Kinematic Stirling Engine Design.

Abstract: Dimensional analysis has been employed to review the isothermal or quasi-static simulation of kinematic Stirling engines and to study the influence of the engine and drive mechanism types, and other parameters, on the thermodynamic engine cycle. The use of isothermal simulation with decoupled losses to obtain reliable predictions at practical levels of rpm is experimentally justified. The method seems to be an adequate tool to study a large number of configurations, which the engineer needs at the initial design stage. At the same time it provides a intuitive knowledge of and similarity criteria for the thermodynamic engine performance.

Sensitivity Analysis of Complex Dynamic System Modelling

Abstract: This paper presents a method for sensitivity analysis of undamped, viscously damped and proportionally damped structural systems based on modal parameters. The method involves the usage of eigenvalues, eigenvectors and theory of adjoint structures to enable the study of the sensitivity of complex mechanical structures. The modal parameters are determined from the experimentally measured vibrational data, and later will be used to select the optimal locations for structural modification to reduce the vibration. They can also be used to determine the dynamic behavior of the structure before and after modification. In the present study, an example is provided to demonstrate the applicability and validity of the method.

Plant Layout Design System using a Hybrid Approach with a Constraint-Directed Search and a Mathematical Optimization Technique

Abstract: A plant layout design system is proposed using a hybrid approach with a constraint-directed search procedure and a mathematical optimization technique. In layout design, a plant must be arranged to satisfy spatial constraints imposed by its components. In our approach, the whole space of a plant building is divided into finite compartments with a modular size in order to separate the description of the layout into the combinational part and the dimensional part. According to this, the approach consists of two steps. In the first step, a constraint-directed search procedure is applied for fixing the combinational relations among plant components so as to satisfy the spatial layout conditions. In the second step, an optimization technique is applied for determining the actual dimensions of compartments so as to minimize the size of a plant building taking the size of components into consideration. In the optimization, mixed-integer programming and sequential linear programming are combined and the mathematical model is formulated automatically from the result of the first step. The system using this hybrid approach has been applied to the design of a nuclear power plant in order to check its validity and effectiveness.