Showing papers on "Rotational speed published in 2003"

Factors influencing the fracture of nickel‐titanium rotary instruments

Abstract: Aim To evaluate the effect of rotational speed and the angle and radius of curvature of root canals on the fracture of two types of nickel-titanium rotary instruments: K3 and ProTaper. Methodology A total of 240 root canals of extracted human maxillary and mandibular molars were divided into two groups of 120, according to the angle of the canal curvature (group A: 30 degrees). Each group was then divided into two subgroups of 60 canals in order to perform instrumentation using K3 and ProTaper rotary instruments at three different rotational speeds: 150, 250 and 350 r.p.m. (20 canals at each rotational speed). Each instrument was used a maximum of 20 times and at one rotational speed only. The angle and radius of canal curvature were measured in the only group in which fractures actually took place (group B). Results There were a total of 22 instrument fractures; all of these occurred in canals with curves >30 degree. In a multivariate analysis, it was demonstrated that the files used at a rotational speed of 350 r.p.m. were more likely to fracture than those used at 250 r.p.m. (OR: 1113.88; 95% CI: 2.36-526420.05) and than those used at 150 r.p.m. (OR: 13531.33; 95% CI: 5.37-34120254.00). A decrease in the angle of curvature of the canal also significantly reduced the likelihood of fracture (OR: 0.2083; 95% CI: 0.068-0.6502). These relationships remained significant after being adjusted for the potential interactions between the remaining variables. No significant differences were found between the files or the radii of the canals. Conclusions Instrument fracture was associated with rotational speed and the angle of curvature of the canal.

Effect of welding parameters on nugget zone microstructure and properties in high strength aluminium alloy friction stir welds

Abstract: Theeffects ofthemainwelding variables,apart form tool design,on themicrostructureandproperties ofthenugget zone in friction stir welds have been investigated for a typical high strength Al alloy (AA7010). It has been found that there is an optimum rotational speed, for a given travel speed, that gives the highest strength and ductility for the nugget zone. As the travel speed is increased, it is necessary to increase the spindle speed to maintain this condition, although the optimum condition does notdirectlyrelatetoa constantratioof rotationalto travel speed. This condition coincides with a heat input, for a given travel speed, that gives the maximum level of solute in solution in the nugget and the lowest density of coarse second phase particles. For low travel speeds, this is limited at excessive heat inputs by reprecipitation occurringduringtheweldcoolingcycles,whereas for high travel speeds incipient melting within the nugget appears to be an important factor.

Drilling in bone: Modeling heat generation and temperature distribution

Abstract: Thermo-mechanical equations were developed from machining theory to predict heat generation due to drilling and were coupled with a heat transfer FEM simulation to predict the temperature rise and thermal injury in bone during a drilling operation. The rotational speed, feed rate, drill geometry and bone material properties were varied in a parametric analysis to determine the importance of each on temperature rise and therefore on thermal damage. It was found that drill speed, feed rate and drill diameter had the most significant thermal impact while changes in drill helix angle, point angle and bone thermal properties had relatively little effect.

Smart fan modules and system

Abstract: A fan module including: two or more individual fans, each fan having an air movement means and a motor engaged with the air movement means for accelerating air entering each of the two or more individual fans; a temperature sensor for sensing a temperature associated with the two or more fans and for outputting a first signal corresponding to the temperature; rotational speed sensor for outputting a second signal corresponding to a rotational speed of each of the two or more fans; and a processor for receiving the first and second signals and controlling the two or more individual fans based on the first and second signals.

Hybrid drive system and vehicle equipped therewith

Abstract: An output of an internal combustion engine is transmitted to an output shaft by controlling a control motor to change a rotation speed output from the engine without speed steps via power distribution planetary gear. An output of a drive motor is input to the output shaft by changing the speed into two-step decelerated rotation by means of an automatic transmission. The transmission produces a desired torque by decelerating the speed by a large degree when a vehicle speed is low, and produces a desired number of revolutions by decelerating the speed by a small degree when the vehicle speed is high.

Dip-spin coater

Abstract: A dip-spin coating apparatus and method is described. A disk is partially immersed into a coating liquid and rotated while the disk is maintained in a substantially vertical plane. Once the disk is coated, the disk is removed from the coating liquid where excess material is spun off at a higher rotational speed while the disk is maintained in the vertical plane.

Electric power steering device

Abstract: A reduction gear ratio n of a reduction gear is multiplied by a steering angular speed by a multiplier, and the deviation e achieved by subtracting a motor rotational speed from the multiplication value is integrated and then multiplied by an integration gain to achieve a current target value The current target value is added with the multiplication value of the deviation e and a proportional gain in a phase compensator to perform phase compensation The phase-compensation result is added with the value achieved by differentiating the motor rotational speed and multiplying the differential value thus achieved by a control gain in an inertia compensator to perform inertia compensation Further, the value achieved by multiplying the motor rotational speed by a control gain is subtracted from the inertia-compensation result in a damping controller to perform damping control, and a final current target value It is achieved from an adder

Centrifugal fluid pump assembly

Abstract: A centrifugal fluid pump assembly 1 includes a body section 5 and a control mechanism 6. The body section 5 includes a housing 20, an impeller 21 rotatable within the housing 20, and a motor 34 for rotating the impeller 21. The pump assembly 1 includes a motor current flow rate-related data storage section 60 for storing, for a plurality of different predetermined viscosities, predetermined viscosity-related flow rate data formed from a plurality of motor current flow rate relation data at a plurality of different impeller rotational speeds at predetermined fluid viscosity, a fluid measurement data inputting section 57, an impeller rotational speed measurement function, a motor current measurement function, and a flow rate calculating section 58 for using a fluid viscosity value, an impeller rotational speed value, a measured motor current and data stored in the motor current flow rate-related data storage section 60 to calculate a fluid flow rate.

Magneto-optical rotational speed sensor

Abstract: A new passive and wireless magneto-optical rotational velocity sensor is described. It is based on measuring the intensity oscillations of linearly polarized light transmitted through an orthoferrite plate and an analyzer. The plate is subjected to the action of the magnetic field of a disc whose angular velocity has to be measured. Thanks to the high velocity and smooth reproducible character of the domain wall motion in the orthoferrite plate, one can continuously measure angular velocities in a very wide range—from ultralow to the MHz range.

Operating temperatures of oil-lubricated medium-speed gears: numerical models and experimental results

Abstract: This paper investigates the effects of gear geometry, rotational speed and applied load, as well as lubrication conditions on surface temperature of high-speed gear teeth. The analytical approach and procedure for estimating frictional heat flux and heat transfer coefficients of gear teeth in high-speed operational conditions was developed and accounts for the effect of oil mist as a cooling medium. Numerical simulations of tooth temperature based on finite element analysis were established to investigate temperature distributions and variations over a range of applied load and rotational speed, which compared well with experimental measurements. A sensitivity analysis of surface temperature to gear configuration, frictional heat flux, heat transfer coefficients, and oil and ambient temperatures was conducted and the major parameters influencing surface temperature were evaluated.

Analysis of the Flow Through a Vented Automotive Brake Rotor

Abstract: Particle image velocimetry (PIV) was used to measure air velocities through a high solidity radial flow fan utilized as an automotive vented brake rotor. A brake rotor is a somewhat unusual fan in that its sole purpose is not to pump air but to dissipate thermal energy, it has no conventional inlet or outlet housing and it has a continuously varying rotational speed. For three typical rotational speeds, the flow characteristics were captured at the inlet and exit of the rotor, as well as internally through the cooling passages. Inlet measurements showed a swirling entry, flow condition with significant misalignment of flow onto the vanes. As a result large regions of flow separation were found in the internal vane-to-vane passages on the suction side surfaces, which would lead to poor heat transfer conditions. The main flow exiting the rotor consisted of a series of jets corresponding to the individual rotor passages

Investigation of the Granular Behaviour in a Rotating Drum Operated over a Wide Range of Rotational Speed

Abstract: Rotating drums are extensively used in the chemical and process industries as mixers, dryers, granulators and reactors for processing granular materials. As a result, granular behaviour in rotating drums has attracted numerous research efforts from both engineering and physics communities over the past few decades. Most of these studies have been focused on drums operated in or close to the rolling mode. However, there are many industrial cases where drums are operated in other modes, e.g. the cascading and cataracting modes, which forms the main motivation for this work. Comprehensive experiments have been carried out to investigate granular behaviour in a drum operated over a wide range of rotational speed with solids motion across the rolling, cascading and cataracting modes. A digital recording device was used to capture images of the transverse plane of the material bed. Analyses of the images were carried out to extract the bed behaviour as a function of rotational speed, drum fill level and particle size. This has led to three relationships between the surface shape expressed in terms of three characteristic lengths, operating conditions, as well as the friction properties of both particles and drum wall. These relations are found to apply approximately to the whole range of rotational speed used in this work. The generality of these relationships and possible application of them for drum scaling are discussed.

Detecting load unbalance and shaft misalignment using stator current in inverter-driven induction motors

Abstract: This paper examines the effect of changing the input frequency of the induction motor with an adjustable speed drive on the detection of mechanical fault conditions, such as load unbalance and shaft misalignment. The mechanical force resulting from these fault conditions is highly dependent on the rotational speed of the motor. When the motor is run at low speeds, the mechanical fault produces less force, resulting in smaller frequency harmonics in the stator current. Nevertheless, results show that the fault signatures are evident in the stator current spectrum even when the drive input frequency is very low. In addition, the drive frequency harmonics do not affect the fault detection, since the frequency components of interest are much lower than the drive frequencies. It is shown that the tested fault conditions are detected in an induction motor running at a rotational speed of as low as 150 rpm. Mechanical fault conditions are detected using a simple, low-cost algorithm that utilizes a single phase of the stator current The employed algorithm could be easily incorporated into the drive at no additional cost.

TEHD lubrication of Mechanical Face Seals in stable tracking mode. Part 2: Parametric study

Abstract: In this paper the influence of the design and operating parameters on the TEHD behavior of Mechanical Face Seals (MFS), in steady dynamic tracking mode, is analyzed for two different types of applications First, an extensive parametric analysis of a typical MFS with very low leakage is presented Then, the influence of rotational speed, sealed fluid temperature and pressure, rings materials, shape, waviness and misalignment of the rotor, are successively examined The use of an original dimensionless parametric analysis leads to a very simple and overall description of the results It is shown that ignoring the thermoelastic distortions of the rings could be misleading as far as the evaluation of MFS performance is concerned In the final part, a hydrostatic MFS with a very large gap and flow rate is studied The increase of the rotational speed induces a progressively turbulent radial flow In this case, it is shown that neither thermal effects nor fluid flow regime significantly affect seal behavior

Effects of Mechanical Parameters on CMP Characteristics Analyzed by Two-Dimensional Frictional-Force Measurement

Abstract: The effects of mechanical parameters on the characteristics of chemical mechanical polishing ~CMP! were evaluated by directly measuring frictional force acting on a wafer in terms of two components, i.e., the tangential and axial components of the platen’s rotation. It was found that, when the platen and the wafer were rotated at the same speed, the tangential component of the frictional force was dominant. Also, frictional force was in linear proportion with removal rate. Though frictional force increased in linear proportion to down force when mechanical-effect-dominant CMP for silicon ~Si! or silicon dioxide (SiO2) was carried out, it decreased gradually as platen rotational speed was increased. Copper ~Cu! polishing using abrasive-free polishing solutions, a typical example of chemical-effect-dominant CMP, showed much more complex behavior. Namely, dependence of frictional force on down force and on platen rotational speed showed nonlinear characteristics. Even when a nonlinear characteristic slurry was used, it was found that removal rate and frictional force were almost linearly correlated. It can thus be considered that frictional force is a basic parameter to determine CMP characteristics. From these results, an experimental equation was proposed to describe CMP characteristics by modifying Preston’s empirical equation.

Practical Strategies for Controlling Railway Wheelsets Independently Rotating Wheels

Abstract: This paper presents the development of an active control strategy for railway vehicles with independently rotating wheels. The proposed control scheme is intuitively formulated with a simple control structure and adaptiveto vehicle speed. It does not require basic guidance measurements (e.g., wheel-rail deflection and angle of attack) that are expensive and impractical to implement. Speed sensors are used to measure the relative rotational speed of the two wheels on a same axle and sensors are also used to measure the relative yaw velocity of the wheelset and the body it is connected. Both curving performance and passenger ride comfort of the actively controlled vehicle are compared with that of a typical passive vehicle and an optimal control scheme.

Advanced high-temperature ultracentrifuge apparatus for mega-gravity materials science

Abstract: An ultracentrifuge apparatus, which can generate an ultra-strong gravitational field even >1 000 000 (1 million) G (1 G=9.8 m/s2) over a wide temperature range up to >500 °C with high stability control, was developed for new materials science research. The system consists of an air turbine motor with ceramic ball bearings and dumper section, a sample rotor with an outer diameter of up to 160 mm, a vacuum chamber, and a heating system. The nonbored rotor and the double-structural dumper bushing are used to raise the maximum rotational speed and to improve the stability. The samples can be heated by radiant heat. A maximum rotational speed of 190 000 rpm using a 70 mm diam rotor was recorded despite a short time where the maximum gravitational field was >1 2000 000 G. Long and high-temperature ultracentrifuge experiments using 70 and 80 mm diam rotors made of titanium alloy with rotational speeds of up to 170 000 rpm even at temperatures of over 200 °C for 100 h with ripples of <0.05% and <1°, respectively,...

Wind power generation device

Abstract: PROBLEM TO BE SOLVED: To provide a wind power generation device very efficiently generating electric power while controlling output fluctuation due to wind speed fluctuation in a wind power generation system in quick responses, and simplifying speed control and a structure of the windmill. SOLUTION: A difference between efficient rotating speed corresponding to wind speed detected by a wind speed detector 21 and rotating speed of the windmill detected by a rotating speed detector 11 is entered into a rotation speed controller 12. A difference between effective electric power command from the rotating speed controller and effective electric power from a synchronous generator 2 is entered into, for example, the electric power controller 13. The electric power controller 13 controls output of the synchronous generator 2 according to the effective electric power command to control rotating speed of the windmill 1 according to increase and decrease of output of the synchronous generator 2.

Compensation of rotor imbalance for precision rotation of a planar magnetic bearing rotor

Abstract: Magnetic bearings provide an alternative for achieving precision rotation. But the rotational accuracy is sensitive to rotor imbalance. The system we study is a planar rotor supported by aerostatic suspension and positioned by a radial magnetic bearing of nanometer precision. We present compensation designs and experiment results for precision rotation about the geometric center and the mass center, respectively. In the former case, the base harmonic component at each sensor output is removed by explicit trigonometric compensation signals that are constructed in real time. In the latter case, a new double-loop compensation design is given. Each compensation loop is similar to that in the former case. The compensation, aided by a variable rotational speed that is changed up and down repeatedly, is shown to push the rotational center to approach the mass center. Once the mass center is reached, the rotor remains to rotate about the mass center at variable rotational speed without transient. Compared with the existing methods, which find the mass center or inertial axis at a fixed rotational speed and rely on exact values of plant parameters, our method may locate the mass center more accurately. Experiment data indicate that the mass center is located with an error of tens of nanometers.

Wind driven electrical power generating apparatus

Abstract: A wind driven electrical power generating apparatus includes a rotor rotating by receiving wind force, a gear assembly having an input shaft connected to the rotor, a generator connected to an output shaft of the gear assembly, a sensor for detecting generating capacity of the generator and a controller for varying gear ratio of the gear assembly based on a signal from the sensor. In this construction, the controller controls so that the generator keeps rotating at around the lowest rotational speed within a range of rotational speed, the range being determined so as to include a maximum power operation region of the generator. Alternatively, the controller controls so that rotational speed of the output shaft of the gear assembly is adjusted to at around the lowest rotational speed within a range of rotational speed, the range being determined so as to include a rated power region as an upper operational limit.

Engine turbocharger control management system

Abstract: A method of controlling a compressor includes measuring a pressure of fluid entering the compressor, measuring a pressure of fluid exiting the compressor, and measuring a rotational speed of the compressor. Signals indicative of the measured pressure of fluid entering the compressor, measured pressure of fluid exiting the compressor, and measured rotational speed of the compressor are sent to an electronic control unit. The operation of the compressor is controlled in response to at least the signal indicative of the measured rotational speed of the compressor received by the electronic control unit.

Tire pressure and parameter monitoring system and method using accelerometers

Abstract: Method for monitoring an operating condition of a vehicle including determining a longitudinal, a lateral, and/or a vertical acceleration, as well as a wheel rotation speed. Determining from the wheel rotation speed and the longitudinal, the lateral, and/or the vertical acceleration a tire condition, a wheel condition, and/or a suspension condition. Device including an accelerometer at a wheel of a vehicle, a wheel rotation speed sensor, and a microprocessor for determining an operating condition. The accelerometer determining a longitudinal, a lateral, and/or a vertical acceleration. The wheel rotation speed sensor determining a rotation speed of the wheel. The microprocessor electrically coupled to the accelerometer and the wheel rotation speed sensor. System for monitoring an operating condition of a vehicle including an accelerometer for each wheel of the vehicle at an axle-end. Each accelerometer determining a longitudinal, a lateral, and/or a vertical acceleration. Wheel rotation speed sensor for each wheel of the vehicle arranged at an axle-end and determining a rotation speed for each wheel. Microprocessor determining the operating condition including a tire condition, a wheel condition, and/or a suspension condition. The microprocessor electrically coupled to each accelerometer and each wheel rotation speed sensor.

Rotating stream sprinkler with speed control brake

Abstract: A rotating stream sprinkler of the type having a rotatable deflector for sweeping small streams of irrigation water in a radially outward direction to irrigate adjacent vegetation, wherein the sprinkler includes a speed control brake for maintaining a substantially constant deflector rotational speed throughout a range of normal operating pressures and flow rates. The deflector includes an array of spiral vanes engaged by one or more water jets for rotatably driving the deflector which converts the jets into a plurality of relatively small irrigation streams swept over the surrounding terrain. A friction plate rotatable with the deflector engages a brake pad retained against a nonrotating brake disk. The brake pad includes tapered contact faces for varying the friction contact radius in response to changes in water pressure and/or flow rate to maintain deflector rotational speed substantially constant.

Vacuum pump control device, and vacuum device

Abstract: A vacuum pump control device capable of suppressing a power consumption by a vacuum pump by varying the speed of the vacuum pump according to the operating conditions of a vacuum device, wherein a condition set part (4) sets a relation between the operating conditions of the vacuum device (10) and the rotational speed of the vacuum pump (2) for vacuating the vacuum device (10) to a proper value so that the rotational speed of the vacuum pump (2) does not reach a rotational speed more than that required, a control part (6) inputs external signals such as S1 to Sn in correspondence with the operating conditions of the vacuum device (10), reads the rotating speed of the vacuum pump (2) in correspondence with the external signals from the condition set part (4), and outputs the rotational speed, and an inverter (8) controls the rotational speed of the vacuum pump based on the output from the control part (6).