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A low speed sensorless position control method for brushless DC motor based on pulse pulse high frequency voltage injection is proposed according to the characteristic that the brushless DC motor (BLDCM) which is produced at present makes the counter electromotive force waveform show sinusoidal waveform in view of the problem that it is difficult to accurately obtain the rotor position and speed of the brushless DC motor at zero and low speed. Its principle is to inject high frequency sinusoidal voltage signal on the estimated direct axis of the synchronous rotating coordinate system so that the motor can generate saturated salient effect, obtain the estimation error containing the rotor position information, and by detecting the output current of PI regulator of quadrature axis current loop, and then estimate the initial position of the rotor and judges the magnetic pole, realize the determination of the actual rotor position, finally, realize the non-position static low speed control of BLDCM by adding current and speed rings. According to the simulation test, it shows that this method can detect the position and speed of the motor rotor well at both zero speed and low speed. [ABSTRACT FROM AUTHOR]

This paper is about the use of BLDC motors in applications to the detriment of induction or brush motors. We have developed a software controller in Mathlab to control the BLDC motor in flow without hall sensors for low speeds and high power. By choosing small and precise speeds, both the stator flow and the rotor flow must be coordinated. [ABSTRACT FROM AUTHOR]

This paper presents predictions of the added resistance of a ship in waves at a low speed according to the IMO minimum propulsion power requirement by a hybrid Taylor expansion boundary element method (TEBEM). The flow domain is divided into two parts: the inner domain and the outer domain. The first-order TEBEM with a simple Green function is used for the solution in the inner domain and the zero order TEBEM with a transient free surface Green function is used for the solution in the outer domain. The TEBEM is applied in the numerical prediction of the motions and the added resistance in waves for three new designed commercial ships. The numerical results are compared with those obtained from the seakeeping model tests. It is shown that the prediction of the ship motions and the added resistance in waves are in good agreement with the experimental results. The comparison also indicates that the accuracy of the motion estimation is crucial for the prediction of the wave added resistance. In general, the TEBEM enjoys a satisfactory accuracy and efficiency to predict the added resistance in waves at a low speed according to the IMO minimum propulsion power requirement. [ABSTRACT FROM AUTHOR]

Introduction: The main objective of this study is to describe incidence rates of low-speed vehicle run-over (LSVRO) events among children aged 0-14 years residing in Queensland from 1999 to 2009. A second objective was to describe the associated patterns of injury, with respect to gender, age group, severity, characteristics (host, vehicle and environment), and trends over time in relation to geographical remoteness. Final results are hoped to inform prevention policies. Methods: In this statewide, retrospective, population-based study, data were collected on LSVRO events that occurred among children aged 0-14 years in Queensland from 1999 to 2009 from all relevant data sources across the continuum of care, and manually linked to obtain the most comprehensive estimate possible of the magnitude and nature of LSVRO events to date. Crude incidence rates were calculated separately for males and females, for fatal events, non-fatal events (hospital admissions and non-admissions, respectively), and for all LSVRO events, for each area of geographical remoteness (major cities, inner regional, outer regional, remote/very remote). Relative risks and 95% confidence interval were calculated, and trends over time were examined. Data on host, injury and event characteristics were also obtained to investigate whether these characteristics varied between areas of remoteness. Results: Incidence rates were lowest among children (0-14 years) living in major cities (13.8/100 000/annum, with the highest recorded incidence in outer regional areas (incidence rate =42.5/100 000/annum). Incidence rates were higher for children residing outside major cities for both males and females, for every age group, for each of the 11 years of the study, and consequences of LSVRO events were worse. Young children aged 0-4 years were identified as those most at risk for these events, regardless of geographical location. Differences were observed as a function of remoteness category in relation to injury characteristics (eg injury type), and host characteristics (eg sociodemographic status), but there were no observed differences in environmental characteristics (eg time of day, day of week). Heavy vehicles such as four-wheel drives, utilities, trucks and tractors were more frequently involved in LSVRO events that occurred outside major cities. Conclusion: The results confirmed that children of all ages and genders residing outside of major cities in Queensland are more at risk of being involved in an LSVRO incident, and experience more severe consequences compared to children in major cities. Future research should address the specific risk factors and focus on engaging rural communities to assist in the prevention of LSVRO incidents. [ABSTRACT FROM AUTHOR]

Abstract: When machining titanium alloys the process stability limits increase very rapidly with reduced cutting speed. The stability rise is stronger than the drop of the cutting speed and it results in growth of removal rate. The increase in removal rate results in savings of machining costs. There is definite advantage in cutter geometry with irregular pitch for increasing the limit of stability. Use of PM HSS tools at low speeds for milling titanium alloys can be the most economical option. The paper introduces the concept of load intensity for assessing tool wear in milling. [Copyright &y& Elsevier]

This paper takes part of a research contract in which the objective is to provide a monitoring process by vibration analysis of bearings on the transfer shaft, within automotive field. Presses have a specialty to work at low speed and to generate a shock type signal with very important amplitude, as a consequence of the stamp that hides the vibration signature of different mechanical components of the machine. A methodology is introduced for the acquisition and the signals treatment, outcoming from a press, with the objective to diagnose the bearings of the transfer shaft. However, the signals resulting from accelerometer sensors are the results of a mixture of sources of vibrations, sources being able to be allotted to one or more defects and are generally polluted by noise. This work presents the three principal methods of denoising and the study of their influence on the scalar parameters (kurtosis, crest factor) within the framework of the detection of defects of the chipping types of bearings on a form press. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, numerous attempts have been made to improve the performance of sensorless induction motor drives. However, parameter variations, low-speed and zero-speed operations are the most critical aspects affecting the accuracy and stability of sensorless drives. This paper presents a stable adaptive flux observer (AFO) for sensorless induction motor drives insensitive to stator resistance variations. Design of the observer feedback gain of AFO is proposed to guarantee the stability, especially at low speeds. The adaptive law parameters are designed to give quick transient response and good tracking performance. The sensitivity of AFO to stator resistance mismatch is studied. A stator resistance adaptation scheme for accurate speed estimation at low speeds is derived. The relation between the identification error of rotor speed and adaptive gains is clarified based on Lyapunov theory. Experimental setup using DSP-DS1102 control board is implemented. Simulation and experimental results confirm the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

Abstract: The dynamics of a bouncing ball undergoing repeated inelastic impact with a sinusoidally-oscillating table is studied numerically. For the ball bouncing at low speed in a weak gravitational field, we show, contrary to expectation, that the trajectories predicted by Newtonian mechanics and general-relativistic mechanics from the same parameters and initial conditions will rapidly disagree completely if the trajectories are chaotic. When the two theories predict completely different chaotic trajectories for a low-speed weak-gravity system, we expect the general-relativistic prediction is empirically correct since general relativity continues to be verified in recent high-precision experiments. [Copyright &y& Elsevier]