Showing papers on "Rotational speed published in 2009"

System for restarting internal combustion engine when engine restart request occurs

Abstract: In a system, a starter includes a motor for rotatably driving an output shaft with a pinion and an actuator that shifts the pinion toward a ring gear to be engaged with the ring gear. A monitor unit monitors a rotational speed of the internal combustion engine. The rotational speed of the internal combustion engine drops after an automatic control for stop of the engine. When an engine restart request occurs with the rotational speed being within a preset range during the rotational speed of the internal combustion engine dropping by the automatic control for stop of the engine, a drive unit drives the actuator to shift the pinion toward the ring gear to be engaged with the ring gear. The drive unit rotatably drives the motor with the pinion being engaged with the ring gear to thereby crank the crankshaft.

Thermohydrodynamic Analysis of Bump Type Gas Foil Bearings: A Model Anchored to Test Data

Abstract: The paper introduces a thermohydrodynamic (THD) model for prediction of gas foil bearing (GFB) performance. The model includes thermal energy transport in the gas film region, and with cooling gas streams, inner or outer, as in typical rotor-GFBs systems. The analysis also accounts for material property changes and the bearing components’ expansion due to temperature rises and shaft centrifugal growth due to rotational speed. Gas inlet feed characteristics are thoroughly discussed in bearings whose top foil must detach, i.e., not allowing for subambient pressure. Thermal growths determine the actual bearing clearance needed for accurate prediction of GFB forced performance, static and dynamic. Model predictions are benchmarked against published measurements of (metal) temperatures in a GFB operating without a forced cooling gas flow. The tested foil bearing is proprietary; hence its geometry and material properties are largely unknown. Predictions are obtained for an assumed bearing configuration, with bump-foil geometry and materials taken from prior art and best known practices. The predicted film peak temperature occurs just downstream of the maximum gas pressure. The film temperature is higher at the bearing middle plane than at the foil edges, as the test results also show. The journal speed, rather than the applied static load, influences more the rise in film temperature and with a larger thermal gradient towards the bearing sides. In addition, as in the tests conducted at a constant rotor speed and even for the lowest static load, the gas film temperature increases rapidly due to the absence of a forced cooling air that could carry away the recirculation gas flow and thermal energy drawn by the spinning rotor, Predictions are in good agreement with the test data. A comparison of predicted static load parameters to those obtained from an isothermal condition shows the THD model producing a smaller journal eccentricity (larger minimum film thickness) and larger drag torque. A rise in gas temperature is tantamount to an increase in gas viscosity, hence the noted effect in the foil bearing forced performance.Copyright © 2009 by ASME

Vibration suppressing method and vibration suppressing device for machine tool

Abstract: A vibration suppressing method and a vibration suppressing device are disclosed. After a tool is attached to a main spindle, a modal parameter of the tool or a workpiece is computed. Thereafter, a relation between chatter frequency and phase difference is calculated as an approximation formula based on the obtained modal parameter and machining conditions. If chatter vibration occurs after initiation of the machining, a chatter frequency corresponding to a target phase difference is obtained using the approximation formula, and based on the obtained chatter frequency, the number of tool flutes and the main spindle rotation speed, the optimum rotation speed is calculated. The rotation speed of the main spindle is then changed in accordance with the obtained optimum rotation speed.

Mechanical properties of friction stir butt-welded Al-5086 H32 plate

Abstract: Al-5086 H32 plates with a thickness of 3 mm were friction stir butt-welded using different welding speeds at a tool rotational speed of 1600 rpm. The effect of welding speed on the weld performance of the joints was investigated by conducting optical microscopy, microhardness measurements and mechanical tests (i.e. tensile and bend tests). The effect of heat input during friction stir welding on the microstructure, and thus mechanical properties, of cold-rolled Al- 5086 plates was also determined. The experimental results indicated that the maximum tensile strength of the joints, which is about 75 % that of the base plate, was obtained with a traverse speed of 200 mm/min at the tool rotational speed used, e.g. 1600 rpm, and the maximum bending angle of the joints can reach 180o. The maximum ductility performance of the joints was, on the other hand, relatively low, e.g. about 20 %. These results are not unexpected due to the loss of the cold-work strengthening in the weld region as a result of the heat input during welding, and thus the confined plasticity within the stirred zone owing to strength undermatching. Higher joint performances can also be achieved by increasing the penetration depth of the stirring probe in butt-friction stir welding of Al-5086 H32 plates.

Method and apparatus for reducing stick-slip

Abstract: A method and apparatus for estimating the instantaneous rotational speed of a bottom hole assembly at the lower end of a drill string. In one embodiment, a method includes driving the drill string by a drilling mechanism at the upper end of the drill string. A fundamental frequency of stick-slip oscillations suffered by the drill string is estimated. Variations in a drive torque of the drilling mechanism are determined. Known torsional compliance of the drill string is combined with the variations in the drive torque. An output signal representing the instantaneous rotational speed is provided.

The high response and high efficiency velocity control of a hydraulic injection molding machine using a variable rotational speed electro-hydraulic pump-controlled system

Abstract: High response and high efficiency velocity control of a hydraulic injection molding machine (HIMM) is requested especially for the process of high-tech industries, such as CD and DVD disks, plastic optical lens, light guide plates, etc. Instead of the hydraulic valve-controlled systems that have the problem of low energy efficiency but have been used widely in today’s HIMMs, the paper develops a high response and high energy efficiency electro-hydraulic pump-controlled system driven by a variable rotational speed AC servo motor for achieving high response and high efficiency velocity control in HIMMs. A constant displacement axial piston pump combined with the AC servo motor is developed in this research as the high response electro-hydraulic pump-controlled system for the HIMMs. For that, the control strategy, signed-distance fuzzy sliding mode control (SD-FSMC) is developed to simplify the fuzzy rule base through the sliding surface for practical applications. The developed high response variable rotational speed electro-hydraulic pump-controlled system controlled by SD-FSMC is implemented and verified experimentally for velocity control with various velocity targets and external loading conditions. Furthermore, the energy efficiencies of different experiments are analyzed and compared precisely by the power quality recorder used to measure the electrical power consumed by the AC servo motor.

Method and device for adapting a clutch in a hybrid drive train of a vehicle

Abstract: A method for adapting torque characteristic in a disengaging clutch arranged in a vehicle hybrid drive train between an internal combustion engine and an electrical machine connected to a driven wheel, include the following steps: deciding the engine can be disconnected; switching the engine off and opening the clutch; detecting the time gradient of rotational speed of the engine with it switched off and the clutch opened; partially closing the clutch when rotational speed of the engine falls below a predetermined value, and detecting the time gradient of rotational speed of the engine with the clutch partially closed; determining the clutch torque transmitted by the partially closed clutch by evaluating detected time gradients of rotational speed of the engine; and adapting the characteristic of the clutch with the aid of the determined clutch torque transmitted by the partially closed clutch.

Constant airflow control of a ventilation system

Abstract: A ventilation system for providing a substantially constant airflow is disclosed. In one embodiment, a ventilation system includes: a duct; a fan configured to generate an airflow through the duct; a motor configured to drive the fan; an electric current detector configured to detect an electric current provided to the motor and to generate a current feedback signal; a motor speed detector configured to detect a rotational speed of the motor and to generate a speed feedback signal; and a controller configured to determine in which speed range among a plurality of speed ranges the speed of the motor is, based at least partly on the speed feedback signal. The controller is further configured to change the electric current by a compensation amount pre-assigned to the determined speed range so as to reach a target value.

Method and apparatus for controlling the tip speed of a blade of a wind turbine

Abstract: A method for controlling a tip speed of a blade of a wind turbine. The method includes determining the wind speed proximate the wind turbine; maintaining a first substantially constant rotational speed of the tip of the blade during variable wind speeds above a first predetermined nominal wind speed and below the second predetermined nominal wind speed; maintaining a second substantially constant rotational speed of the tip of the blade during variable wind speeds above a second predetermined nominal wind speed. The noise generated by wind at the second predetermined nominal wind speed is greater than noise generated by the blade at the second constant rotational speed of the tip of the blade.

A peristaltic micro pump driven by a rotating motor with magnetically attracted steel balls.

Abstract: In this paper, we present a membrane peristaltic micro pump driven by a rotating motor with magnetically attracted steel balls for lab-on-a-chip applications. The fabrication process is based on standard soft lithography technology and bonding of a PDMS layer with a PMMA substrate. A linear flow rate range ~490 μL/min was obtained by simply varying the rotation speed of a DC motor, and a maximum back pressure of 592 Pa was achieved at a rotation speed of 43 rpm. The flow rate of the pump can also be adjusted by using steel balls with different diameters or changing the number of balls. Nevertheless, the micro pump can also work in high speed mode. A high back pressure up to 10 kPa was achieved at 500 rpm using a high speed DC motor, and an utmost flow rate up to 5 mL/min was reached.

A flexible chain-based screw propeller for capsule endoscopes

Abstract: In this paper, a new type of screw propeller for capsule endoscopes is introduced whose rotation motion is enforced by magnetic forces between an armature magnet inside the capsule and an external rotating permanent magnet working like an AC stator. The screw propeller consists of flexible threads attached on the capsule body. The spiral angle of the flexible threads switches automatically due to the friction force between intestine wall and the capsule body when the rotating direction of the capsule body is reversed. Therefore, the moving direction of the capsule is independent of the rotating direction of the capsule body. This will help the capsule advance especially in curved tracts by changing its effective thread angle for reduction of friction torque. In order to investigate main parameters that influence the performance of the new screw propeller, we evaluated the speed of the capsule with various shapes and sizes of the flexible threads, changing the parameters such as rotational speed of the external permanent magnet, distance between the external magnet and the armature magnet inside the capsule, and viscosity of lubrication oil in artificial intestine tract. The speed of the capsule with the flexible screw propeller was mainly dependent on the shape of threads. Also, the distance between the magnets highly influenced the speed of the capsule since thrust force of the capsule was dependent on it. On the contrary, rotational speed and oil viscosity insignificantly contributed to the speed of the capsule. Especially in curved tracts, the effective thread angle of the screw propeller which could be changed by its rotation direction played a great role in advancing the capsule efficiently.

Control system and control method for airborne flight

Abstract: A control system and method for control of a cyclical flying system which uses lift segments, which may be airfoils, which rotate around a central hub, similar to the mechanics of an autogyro. The airfoils may achieve speeds significantly above the wind speed feeding the system. The airfoils may be linked to the central hub by flexible radial tethers which stiffen considerably as the speed of the airfoil increases. The central hub may be linked to the ground with an extendible main tether. Power generation turbines may reside on the airfoils and utilize the high apparent wind speed for power generation. The generated power may travel down the radial tethers and across a rotating power conduit to the main tether and to the ground. The airborne assembly may have the rotational speed of the airfoils, its altitude, and its attitude controlled by using control surfaces linked to the airfoils, or by control of the angle of attack of the airfoils relative to a central hub, or relative to each other. The attitude and altitude sensors and the control system may be airborne and may be part of the rotating assembly. The airborne assembly can be moved to areas of appropriate wind speed for the system using these controls.

Rotating electrical machine control system and vehicle drive system

Abstract: A rotating electrical machine control system includes a rotating electrical machine, a frequency conversion portion, a voltage conversion portion, a torque limitation portion, and an abnormality detection portion. The torque limitation portion limits generation of a positive torque in a region of less than a rotational speed lower limit threshold value where a rotational speed of the rotating electrical machine is less than zero, and sets a region in which the positive torque is generated to a region of the rotational speed lower limit threshold value or greater, and the torque limitation portion limits generation of a negative torque in a region of greater than a rotational speed upper limit threshold value where the rotational speed of the rotating electrical machine is greater than zero, and sets a region in which the negative torque is generated to a region of the rotational speed upper limit threshold value or less.

Static synchronous generators

Abstract: The invention is concerned with a device and a method for controlling an inverter associated with a power source, which typically will be a distributed power source. The role of an inverter is to modulate the electrical power output, e.g. to provide a three phase AC electrical output at suitable voltage, where the output is to be supplied to a conventional power distribution, grid. The invention involves modelling the behaviour of a synchronous electrical generator. Variables represent the angular position and rotational speed of the virtual rotor (14) of this virtual synchronous generator. The torque electromagnetically exerted on the rotor is calculated from a measured inverter output current, and from a variable representing excitation current in the rotor. Allowing for this and for a notional drive torque applied to the virtual rotor (which in the physical analogue would be supplied by some prime mover such as an engine), as well as for the virtual inertia of the rotor, the angular speed of the virtual rotor is calculated, Using the angular position and rotational speed of the virtual rotor, and allowing for the aforementioned excitation current, it is possible to obtain the cmf induced in stators of the virtual generator. On this basis a control signal is generated which causes the inverter to produce an AC output corresponding to that which would be provided by the virtual synchronous generator. A synchronous generator must be regulated, as too must the virtual synchronous generator of the present invention. To this end, the invention provides a feedback loop in which deviation of the rotational speed of the virtual generator rotor from a reference angular speed is detected and is used to adjust the virtual drive torque, thereby to regulate the rotational speed of the rotor and hence the frequency of the AC output and the real power supplied by it.

High Speed–High Quality Friction Stir Welding of Austenitic Stainless Steel

Abstract: Although several studies on the friction stir welding of high temperature materials have recently been reported, their practical use has not yet occurred due to some problems to be solved such as decreases in the corrosion resistance and joint efficiency during a high-speed joining. In this study, the effect of the welding speed on the joint efficiency was investigated in detail. As a result, it has been clarified that at a rotational speed of 600 rpm, the friction stir welding of 304 austenitic stainless steel is possible up to the joining speed of 1200 mm/min, and the tensile strength of the joint exceeds that of the parent material up to the joining speed of 1150 mm/min. In addition, the corrosion resistance is significantly improved at the higher welding speeds. No rust was observed during the salt spray testing of the 1000 mm/min joint. Thus, an increase in the welding speed can improve productivity and the product quality by decreasing corroded region. These results are expected to extend to an actual application to products by further improving the technology.

Vibration suppressing method and device

Abstract: A stable rotation speed is acquired by finely changing a rotation speed of a rotary shaft 3 based on an expected stable rotation speed, and calculating an amount of change of a k′ number, and the like. Therefore, a more accurate rotation speed can be acquired, and “chatter vibration” generated during machining can be suppressed more effectively than a conventional method. As a result, a quality of a workpiece surface can be improved, and a tool wear and the like can be suppressed.

Manufacturing method of absorbent article and manufacturing apparatus of absorbent article

Abstract: The present invention provides a method includes the steps of: conveying in a conveyance direction MD a second web in which components forming one part of an absorbent article are sequentially arranged; swinging an elastic member in a cross direction CD at a predetermined cycle by using a swing guide mechanism for guiding the elastic member; and pressing, between one pair of press rollers, the second web on which the elastic member is arranged. The swing guide mechanism has a motor with a rotational shaft, an arm member for guiding the elastic member to a predetermined position on the second web in the cross direction, and a speed reducer provided between the rotational shaft and a base of the arm member to make a rotational speed of the arm member slower than a rotational speed of the rotational shaft.

Flow Past Two Rotating Circular Cylinders in a Side-by-side Arrangement

Abstract: Measurements were performed using Particle Image Velocimetry (PIV) to analyze the modification of flow by the combined effects of the rotation and the Reynolds number on the flow past two rotating circular cylinders in a side-by-side-arrangement at a range of 425 ≤ Re ≤ 1130,0 ≤ α ≤ 4 (α is the rotational speed) at one gap spacing of T/d = 1.11 (T and d are the distance between the centers of two cylinders and the cylinder diameter, respectively). A new Immersed-Lattice Boltzmann Method (ILBM) scheme was used to study the effect of the gap spacing on the flow. The results show that the vortex shedding is suppressed as rotational speed increases. The flow reaches a steady state when the vortex shedding for both cylinders is completely suppressed at critical rotational speed. As the rotational speed further increases, the separation phenomenon in the boundary layers disappears at the attachment rotational speed. The critical rotational speed and attachment rotational speed become small as Reynolds number increases. The absolute rotational speed of cylinders should be large at same critical rotational speed and attachment rotational speed in the case of large Reynolds number. The gap spacing has an important role in changing the pattern of vortex shedding. It is very different in the mechanism of vortex shedding suppression for the flows around two rotating cylinders and single rotating cylinder.

Theoretical and experimental results of a mesoscale electric power generation system from pressurized gas flow

Abstract: In many process applications where throttling is used to reduce pressure, the potential to obtain net work output is sacrificed to the throttling process. Examples are throttling valves of gas pipelines and conventional throttles in automotive applications or turbo expanders as used in cryogenic plants. With a new pressure reduction system that produces electricity while expanding the gas, the lost potential to obtain work output can be recovered. To achieve a high power density, this energy generation system requires an increased operating speed of the electrical machine and the turbomachinery. This paper presents a miniature compressed-air-to-electric-power system, based on a radial turbine with a rated rotational speed of 490 000 rpm and a rated electric power output of 150 W. A comprehensive description including turbine, diffuser and permanent magnet (PM) generator is given. Finally, measurements of the compressed-air-to-electric-power system with a maximum rotational speed of over 600 000 rpm, a maximum electric output power of 170 W, a maximum torque of 5.2 mN m and a turbine efficiency of 52% are presented.

Method and apparatus for damping tower oscillation in a wind turbine

Abstract: A method of damping tower oscillation in a wind turbine is provided. The method includes the steps of determining a rotor rotational speed of the wind turbine and controlling the rotor rotational speed such that a critical rotor speed is avoided, characterized in that it further comprises the following steps: selecting at least one input parameter value; selecting, according to the input parameter value, an operation mode for controlling the rotor rotational speed, wherein the operation mode is selected from a set of modes comprising a mode of auto tune operation; on the condition of the selected operation mode comprising the mode of auto tune operation, performing the following steps: detecting the tower oscillation frequency; calculating the critical rotor speed based on the detected tower oscillation frequency and controlling the rotor rotational speed to avoid the calculated critical rotor speed. An apparatus and a computer program product are also provided.

Motor-generator system driven by v-belt

Abstract: A motor-generator system for a vehicle, in which power transmission between a crankshaft of an engine and a motor-generator is performed by a V-belt wound around pulleys thereof, includes a speed controller controlling the rotational speed of the V-belt within a predetermined range and provided on a crankshaft pulley mounted on the crankshaft. The motor-generator system, among others, can maintain the power transmission force of the V-belt at a high level.