Quick and precise position control of ultrasonic motor using hybrid control

The ultrasonic motor has an excellent level of performance and many useful features, including high torque, low speed, compactness in size, and absence of electromagnetic interference. This motor has an especially large holding torque and a high response characteristic, making it ideal for use as a servomotor. The drive principle of the ultrasonic motor is, however, different from that of electromagnetic motors and its mathematical model has not been developed yet. Its speed characteristics, moreover, vary with the driving conditions. Consequently, it is difficult to control the ultrasonic motor while maintaining performance. In this paper, a position control scheme using adaptive control is proposed. The utility and validity of the proposed control scheme is tested in experiment.     

Characteristics of lithium-ion battery with non-flammable electrolyte

To improve the safety of lithium-ion batteries, we studied non-flammable electrolytes made by adding several types of phosphazene-based flame retardants to conventional electrolytes and evaluated their conductivities, electrochemical characteristics, and the effects of flame retardants in terms of safety. Cell performance tests and abuse tests were also conducted using cylindrical test cells. The conductivity of electrolytes decreased when phosphazene-based flame retardants were added to the conventional electrolytes. The reason for this decrease in conductivity may be the increase in electrolyte viscosity caused by adding flame retardants. The conductivity decrease led to a decrease in cell capacity at high current density and at low temperature. However, the cell capacities at 0.2 CA (CA = 750 mA) and at 25 °C were almost the same as those of cells using conventional electrolytes. Flame tests showed that the electrolytes with flame retardants exhibited flame resistance consistent with UL-94V0. We also carried out several abuse tests to check the safety improvements. Both overcharge tests up to 10 V and heating tests up to 200 °C were completed without any extraordinary heat generation. Heating tests using a burner revealed the self-extinguishing properties of these electrolytes which were gushed out by venting. These results indicate that electrolytes with phosphazene-based flame retardants are effective for making lithium-ion batteries safe.     

A fuzzy based method for leveling output power fluctuations of photovoltaic-diesel hybrid power system

A Photovoltaic system’s output power fluctuates as insolation varies with weather condition. Fluctuating PV power causes frequency deviations when large PV power is penetrated in the isolated utility. In this paper, a fuzzy based method for leveling the fluctuations of PV power in a PV-diesel hybrid power system is proposed. By means of the proposed method, output power control of PV system becomes possible considering power utility conditions and the conflicting objective of output power leveling and maximizing energy capture is achieved. Here, fuzzy control is used to generate the output leveling power command. The fuzzy control has three inputs of average insolation, variance of insolation, and absolute average of frequency deviation. First, the proposed method is compared with the method where captured maximum power is given to the utility without leveling. Second, the proposed method is compared with a conventional method where captured maximum power is leveled by using an energy storage system and is given to the isolated utility. Simulation results show that the proposed method is effective in leveling PV power fluctuations and is feasible to reduce the frequency deviations of the isolated power utility.     

Molten lithium sulfonimide salt having poly(propylene oxide) tail

Poly(propylene oxide) (PPO) tailed lithium(trifluoromethyl sulfonylimide)s (TFSI-PPO) were prepared as non-onium type ionic liquid polymers. Introduction of PPO chain to the TFSI salt group resulted in lower the glass transition temperature (T_g) and induce the salt dissociation. The TFSI-PPO showed relatively high ionic conductivity owing to the high dissociation degree of the TFSI salt group. The maximum ionic conductivity of 3.3×10⁻⁶ S cm⁻¹ was observed at 30 °C for TFSI salt having PPO tail with number average molecular weight of 850. On the other hand, PPOs having the same salt moiety on both chain ends ((TFSI)₂-PPO) showed higher T_g than that of TFSI-PPOs. The lithium transference number of the (TFSI)₂-PPO with PPO chain length of Mn=2000 was 0.74 in spite of slightly lower ionic conductivity.     

A new recursive neural network algorithm to forecast electricity price for PJM day‐ahead market

This paper evaluates the usefulness of publicly available electricity market information in predicting the hourly prices in the PJM day‐ahead electricity market using recursive neural network (RNN) technique, which is based on similar days (SD) approach. RNN is a multi‐step approach based on one output node, which uses the previous prediction as input for the subsequent forecasts. Comparison of forecasting performance of the proposed RNN model is done with respect to SD method and other literatures. To evaluate the accuracy of the proposed RNN approach in forecasting short‐term electricity prices, different criteria are used. Mean absolute percentage error, mean absolute error and forecast mean square error (FMSE) of reasonably small values were obtained for the PJM data, which has correlation coefficient of determination (R²) of 0.7758 between load and electricity price. Error variance, one of the important performance criteria, is also calculated in order to measure robustness of the proposed RNN model. The numerical results obtained through the simulation to forecast next 24 and 72 h electricity prices show that the forecasts generated by the proposed RNN model are significantly accurate and efficient, which confirm that the proposed algorithm performs well for short‐term price forecasting. Copyright © 2009 John Wiley & Sons, Ltd.     

A novel particle swarm optimization method based on quantum mechanics computation for thermal economic load dispatch problem

This paper presents an efficient strategy to solve the thermal economic load dispatch (ELD) problem by considering several aspects of ELD. ELD performs an important role in the economical operation of power system, which essentially involves nonlinearity according to the characteristics of the generators. The complexity is amplified when the generators' prohibited zones and valve‐point effect are considered, which makes ELD a nonconvex and nonsmooth problem. The strategy employs a mechanism involving a quantum mechanics‐inspired particle swarm optimization (QMPSO). The conventional PSO is modified by integrating quantum mechanical theory which redefines the particles' positions and velocities in a dynamic manner and therefore explores more search space. The QMPSO employs a multipopulation‐based scheme which ensures particle movement and avoids premature convergence at the same time. Moreover, in order to diversify the particles, a dynamic mutation operator is introduced in the proposed method. Such features deliver a fine balance between the local and global searching abilities. Simulations are carried out by considering several cases of thermal units of varying combinations of system configurations such as with and without the valve point, with and without network loss, and for one or several hours of load demand. The results are quite promising and effective compared with several benchmark methods. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Octithiophene on Cu(III) and Au(III): formation and electronic structure of molecular chains and films

Adsorption and electronic structure of octithiophene (8T) molecules on Cu(III) and Au(III) surfaces are investigated using scanning tunneling microscopy (STM) and spectroscopy (STS) at room temperature. We find a large difference in adsorption behavior of 8T molecules on the two surfaces. At the initial stage of adsorption, 8T molecules are stabilized in the form of molecular chain on a terrace of Cu(III), whereas neither such chain structure nor isolated 8T molecules have been observed on a terrace of Au(III). By increasing the amount of adsorbed molecules, a disordered monolayer film is formed on Cu(III) while a well-ordered monolayer film is formed on Au(III). From the spectroscopic investigations using bias-dependent STM images and STS spectra and by comparing the data with theoretical calculations, it is found that the electronic property of 8T molecules in the molecular chain on Cu(III) is different from that of a free-standing 8T molecule while that in the monolayer film on Au(III) keeps original character of the free-standing 8T molecule. The present study shows that adsorption of 8T molecules on Cu(III) results in a formation of adsorption-induced states near the Fermi level.     

Electrochemical properties of LiCoO2/nanocarbon composites fabricated from organic liquids

We fabricated LiCoO₂/carbon composites by forming helical carbon nanomaterials (HCNs) from organic liquids as carbon sources on the surface of LiCoO₂ particles by chemical vapor deposition (CVD) and estimated their electrochemical properties as cathodes of rechargeable lithium cells. By scanning electron microscopy measurements, we observed HCNs called carbon nanotwists formed on the surface of LiCoO₂ particles. X-ray diffraction measurements suggested that acetic acid supplies LiCoO₂/HCNs with less decomposition of LiCoO₂ than C₂H₂ does. However, we found that the electrochemical properties of cells containing the composites were not as good as those of cells containing acetylene black (AB).     

Monitoring of chicken houses and an attached egg-processing facility in a laying farm for Salmonella contamination between 1994 and 1998.

Two chicken houses and an attached egg-processing facility in a laying farm were sampled between 1994 and 1998 to investigate Salmonella contamination. Each of the houses was environmentally controlled and fitted with egg belts that transported eggs from the houses to the egg-processing facility. Four hundred twenty-eight Salmonella isolates were obtained from 904 environmental samples collected from the houses. Two hundred fifty-two of the 428 (58.9%) isolates yielded five serotypes as follows: Salmonella enterica subsp. enterica serovar Livingstone, Salmonella serovar Cerro, Salmonella serovar Montevideo, Salmonella serovar Mbandaka, and Salmonella serovar Corvallis. The remaining (41.1%, 176 of 428) isolates included four other serotypes and isolates that were untypeable. Salmonella isolates obtained from the drain water collected after the washing of the eggs in the egg-processing facility yielded the same serotypes as those found in the chicken houses. Strains having an identical pulsed-field gel electrophoresis (PFGE) pattern were continually recovered from a house for more than 1 year. Several strains of Salmonella Cerro, Salmonella Mbandaka, and Salmonella Montevideo obtained from both the houses and from the egg-processing facility were indistinguishable by PFGE, respectively. These results suggest that Salmonella organisms originating from a single clone colonized the chicken houses and that the egg belts are likely to be one of the means by which Salmonella organisms are spread from one house to the others.     

Output power control for large wind power penetration in small power system

Nowadays, wind turbine generator (WTG) is increasingly required to provide control capabilities regarding output power. Under this scenario, this paper proposes an output power control of WTG using pitch angle control connected to small power systems. By means of the proposed method, output power control of WTG considering states of power system becomes possible, and in general both conflicting objectives of output power leveling and acquisition power increase are achieved. In this control approach, WTG is given output power command by fuzzy reasoning which has three inputs for average wind speed, variance of wind speed, and absolute average of frequency deviation. Since fuzzy reasoning is used, it is possible to define output power command corresponding to wind speed condition and changing capacity of power system momentarily. Moreover, high performance pitch angle control based on output power command is achieved by generalized predictive control (GPC). The simulation results by using actual detailed model for wind power system show the effectiveness of the proposed method.