The servo press with a flywheel is able to provide flexible motions with energy-saving merit, but its true potential has not been thoroughly studied and verified. In this paper, such the “hybrid-driven” servo press is focused on, and the stamping capacity and the energy distribution between the flywheel and the servomotor are investigated. The capacity is derived based on the principle of energy conservation, and a method of using a capacity percentage plane for evaluation is proposed. A case study is included to illustrate and interpret that the stamping capacity is highly dependent on the programmed punch motions, thus the capacity prediction is always necessary while applying this kind of servo press. The energy distribution is validated by blanking experiments, and the results indicate that the servomotor needs only to provide 15% to the flywheel torque, 12% of the total stamping energy. This validates that the servomotor power is significantly saved in comparison with conventional servo presses.

View full abstract

The follower separation is a major impediment to the operating speed increase of force-closed cam mechanisms. This problem traditionally is solved by increasing the spring preload or spring rate to enlarge the return force. An alternative approach with variable cam speed is proposed to prevent follower separation and thereby to raise the average operating speed. By properly designing the cam speed to change the follower motion, the critical motion characteristics leading to follower separation can be avoided. The cam speed trajectory is expressed using the Bezier function. A mathematical model is developed for analyzing the cycle time and the critical times of follower separation. Then a design model for optimizing the critical average cam speed without follower separation is developed to specify the design parameters of this trajectory. Two design examples with different cam motion programs are given for demonstrating the feasibility of this approach.

View full abstract

The authors developed advanced haptic displays capable of stimulating the muscles and tendons of the forearms and tactile receptors in fingers to investigate tactile and force effects on simultaneous presentation. Display A is comprised of a master hand with two sets of tactile display with a 4-by-6 array of stimulus pins driven by micro-actuators and an articulated manipulator. Display B is comprised of an articulated manipulator and an 8-by-8 array type tactile display developed in a previous paper. A series of experiments was performed using the above A and B displays to verify the presentation capability of this display type. In Experiment I, subjects grasped virtual pegs and judged their diameters. In Experiment II, subjects tried to insert the pegs into holes. In Experiment III, the crossed-angle of a comparison texture was adjusted to bring it as close as possible to the standard texture fixed during experiments. Since diameter discrimination and insertion precision of the virtual peg were increased by tactile information, tactile-force presentation was effective for peg-in-hole for relatively large clearance. On the other hand, recognition capability for virtual texture was not enhanced compared to a mouse-mounted tactile display previously developed. While the pressure display is effective for instant of touch and peg rotation representations, rotation tactile imaging is not always effective for texture recognitions.

View full abstract

The photothermal effect, which changes light into heat, can be used to generate driving force from thermal stress. Micro-cantilevers, the simplest micromachine element, are driven using a modulated laser diode and the frequency response characteristics and deflection are measured. By applying photothermal driving to a micro-disk on a central pivot, a standing wave is generated. The optimum disk material parameters to maximize the driving force are investigated. The amplitude of the standing wave is found to increase as the thickness of the micro-disk is decreased and the amplitude increases with the ratio of the coefficient of thermal expansion and thermal conductivity. The amplitude also increases with laser output. It is found that stainless steel is the most suitable disk material.

View full abstract

In this paper, simultaneous five-axis control motions were newly proposed to identify the ten inherent deviations to double pivot head type five-axis machines. This motion was designed for the application of a ball bar to the measurements. The ball bar can be applied to the motion by changing the ball bar's sensitive direction in the axial, radial and tangential directions in relation to the A-axis rotation. All the three ball bar settings can be changed in a single arrangement, with a magnetic clamp fixed onto the main spindle. This leads to reduce the setting errors and setting time as well. The ten deviations are identified by using three measurements, two of which are taken in the axial direction motion while the third is extracted using the tangential or radial direction motion. From the axial direction motion, seven deviations are estimated; four of these estimations are made using the observation equation while the other three are made using simple geometric relations. The remaining three of the ten deviations are determined by using tangential or radial motion. The validity of the proposed method is confirmed by simulations.

View full abstract

This paper reports on ductile to brittle transition of hard brittle materials in nano plastic forming process. Formability of some hard brittle materials, i.e., glasses, silicon and quartz wafers, were examined through a specially designed and developed nano forming tester. A wedge type tool of single crystal diamond was indented to the specimen so that two dimensional plastic deformation was realized. Crack ratio was measured by an optical microscope. Depth of indented grooves were analyzed by FIB machining and SEM observation technique. Based on experimental data, load/depth relationship and the critical depths of hard/brittle materials, at which ductile to brittle transition in deformation occurs, were assessed. The mechanism of ductile-brittle transition is also elucidated by a theoretical model developed based on fracture mechanics. The theory explains that the critical depth depends on the fracture toughness and yield stress of the material, which agrees with experimental results. Effects of microscopical structures of material such as size distribution of micro cracks and anisotropy are discussed.

View full abstract

Mixed and fluid film lubrication characteristics of hydrostatic spherical bearings for swash-plate-type axial piston pumps and motors are studied theoretically under non-steady-state conditions. The basic equations incorporating interference and contact of surface roughness are derived fundamentally through combination of the GW and PC models. Furthermore, a programming code that is applicable to the caulked-socket-type and open-socket-type bearings is developed. Effects of caulking, operating conditions, and the bearing dimension on the motion of the sphere and tribological performance of the bearings are examined. Salient conclusions are the following: The sphere's eccentricity increases in the low supply pressure period. The time-lag of the load change engenders greater motion of the sphere. Caulking of the bearing socket suppresses the sphere's motion. The bearing stiffness increases and power loss decreases for smaller recess angles. Minimum power loss is given under the condition that the bearing socket radius nearly equals the equivalent load radius.

View full abstract

In order to help the physical activities of the elderly or physically disabled persons, we propose a new concept of a power-assist inner skeleton robot (i.e., actuated artificial joint) that is supposed to assist the human daily life motion from inside of the human body. This paper presents an implantable 2 degree of freedom (DOF) inner skeleton robot that is designed to assist human elbow flexion-extension motion and forearm supination-pronation motion for daily life activities. We have developed a prototype of the inner skeleton robot that is supposed to assist the motion from inside of the body and act as an actuated artificial joint. The proposed system is controlled based on the activation patterns of the electromyogram (EMG) signals of the user's muscles by applying fuzzy-neuro control method. A joint actuator with angular position sensor is designed for the inner skeleton robot and a T-Mechanism is proposed to keep the bone arrangement similar to the normal human articulation after the elbow arthroplasty. The effectiveness of the proposed system has been evaluated by experiment.

View full abstract

In this study, a robust topology optimization method is proposed for compliant mechanisms, where the effect that variation of the input load direction has on the output displacement is considered. Variations are evaluated through a sensitivity-based robust optimization approach, with the variance evaluated using first-order derivatives. The robust objective function is defined as a combination of maximizing the output deformation under the mean input load and minimizing variation in the output deformation as the input load is varied, where variance due to changes in load can be obtained through mutual compliance and the presence of a pseudo load. For the topology optimization, a modified homogenization design method using the continuous approximation assumption of material distribution is adopted. The validity of the proposed method is confirmed with two compliant mechanism design problems. The effect that varying the input load direction has upon the obtained configurations is investigated by comparing these with deterministic optimum topology design results.

View full abstract

In recent years, as part of the remarkable development of electronic techniques, electronic control has been applied to various systems. Many sensors and actuators have been implemented into those systems, and energy efficiency and performance have been greatly improved. However, these systems have been complicated, and much time has been required to develop system controllers. In this paper, a method of automatic controller design for those systems is described. In order to automate the design of an electronic controller, an evolutionary hardware is applied. First, the framework for applying the genetic algorithm to the automation of controller design is described. In particular, the coding of a chromosome is shown in detail. Then, how to make a fitness function is represented, with an air conditioner as an example, and the controller of the air conditioner is developed automatically using our proposed framework. Finally, an evolutionary simulation is performed to confirm our framework.

View full abstract

This paper proposes a new type of electrostatic oil filter and presents results of filtration experiments. Aiming at increasing the amount of electric charges on contaminants in oils and thus increasing the filtration speed of an electrostatic oil filter, electric charges are forcibly injected into oils by applying a high DC voltage to an electrode pair consisting of an electrode with many sharp projections on its both sides, called the emitter electrode, and of two smooth electrodes. Fourteen types of lubricating oils, into which a test powder is mixed at a fixed concentration, are used for filtration experiments. The experiments show that the filtration speed is increased to a great or some degree for most of the oils and that for the majority of the oils, the electrification polarity of a few tens to one hundred percent of powders can be inverted by injecting electric charges with the opposite polarity to the original electrification polarity of the powders. It is also shown that no definite correlation can be seen between the physical properties (conductivity and viscosity) of oils and the degree of the increase in the filtration speed due to charge injection.

View full abstract

High-speed winding of paper web sometimes leads the winding system into unstable states, interlayer slippage of wound roll, paper breakage and so on, due to the excessive air-entrainment at the roll-inlet of nip contact region. These phenomena are more frequently observed on coated paper or plastic film comparing with newspaper, because the former allows little permeation of air and their surface roughness is small. Therefore, it is of vital importance to clarify the in-roll stress of wound roll considering the effect of air-entrainment.
Generally, it is known that the amount of air-entrainment is affected by grooving shape of nip roll surface. In this paper, we focused on the grooving shape and investigated the relationship with the air-entrainment into two rolls being pressed each other and the grooving shape in order to achieve stable winding at high speed. We conducted experiments using small sized test machine. Entrained air-film thickness was evaluated applying the solution of the elasto-hydrodynamic lubrication for foil bearing with the consideration of nip profile at the grooved area. Air film thickness was measured to ensure the applicability of the above theory.
Consequently, we found that the air film thickness can be estimated considering the effect of grooves on the nip roll surface, and that the validity of the above estimations was ensured from experimental investigations. Furthermore, it became to be able to propose the optimal shape of grooves on nip roll surface to maintain the stable winding at high speed and at large-diameter in reel.

View full abstract

Circular vibration milling (CVM) is achieved by vibrating a milling cutter about the machine tool spindle axis in a circular path, in addition to its rotary motion. CVM has been proven capable of producing better surface finishes on difficult to cut materials. However, the CVM process is far slower than conventional milling process. In circular vibration planing (CVP) process, the cutting tool is clamped without rotation and fed at a speed comparable to the feed speed of conventional milling. By superimposing circular vibration motion, necessary cutting speed could be achieved keeping the feed speed at realistic values. Inconel 718 was machined by CVP and conventional milling at a similar feed rate. It was observed that CVP could reduce tool wear and hence produce better surface finishes than conventional milling. A geometric simulation showed a major difference between uncut chip shapes of the two processes. The difference of uncut chip shapes suggests that in CVP process, less rubbing occurs between tool flank face and work before the tool penetrates in to the work to form a chip. The reduced rubbing of the flank face is proposed as the reson for reduced tool wear in CVP when compared with conventional milling.

View full abstract

Friction and wear tests were conducted for two kinds of material combinations: a DLC-coated and sintered-graphite-carbon material combination, and a non-coated and sintered-graphite-carbon material combination, for comparison. DLC showed a higher friction coefficient than non-DLC materials. Carbon transfer films were only observed at certain places on the DLC surfaces, while most non-DLC surfaces were coated with those films. However, for DLC specimens, the high friction was found to be attributable to the transfer-film area but not non-transfer-film area (i.e. DLC itself). The sintered-graphite-carbon specimens having slid on DLC had little oriented surface layers due to anti-adhesion and amorphous properties of DLC while those having slid on non-DLC were strongly oriented to the sliding direction. Thus, the surface orientation was necessary for sintered carbon graphite to indicate low friction when sliding on its transfer film, and the high friction of DLC was due to the sliding between the little oriented sintered graphite carbon and the transfer film.

View full abstract

Today manufacturers of bevel gears are confronted with continuously growing demands on the cost effectiveness of the manufacturing process. To enhance the productivity of manufacturing processes, the processing time has to be reduced. Therefore maximum removal rates and reliable, reproducible processes are of crucial importance for modern production operations. In current industrial practice, however, even slight changes in the cutting parameters, tool geometry or even the gear geometry can result in significant variations in tool life behavior. The knowledge of the chip creation parameters is of crucial importance in order to analyze the manufacturing process. For this reason a new software tool for the simulation of cutting processes for bevel gears was developed. As a result the chip thickness, effective cutting velocities, effective cutting length and the process forces are calculated. With this software it is now possible to give a detailed insight into the cutting process and to estimate the load on the tool and the tool life. In this paper the calculation of the mentioned chip creation parameters is presented for different manufacturing parameters. This gives a first understanding of the different loads on the cutting edge of the tool.

View full abstract