This paper developed a dynamic voltage scaling (DVS) technique for the power management of the OLED display on mobile devices in video streaming applications. An optimal voltage control scheme is proposed under input constraints. Fine-grained DVS technique is applied to maximize the power saving by leveraging the locality of the display content. The display quality is retained by monitoring structural-similarity-index (SSIM) during the optimization, subject to the hardware constraints like voltage regulator response time. Simulation results on four typical video test benchmarks show that the proposed technique saves 19.05%~49.05% OLED power on average while maintaining a high display quality (SSIM > 0.98) all the time. The power saving efficiency of the proposed technique varies at different display resolutions, refresh rates, and display contents.

Ball screw mechanisms (BSMs) are used as accuracy transmission components in a wide range of industries and are characterized by their high accuracy. More specifically, the positioning accuracy of BSM has a significant effect on the accuracy of machine tool. Based on the macro-micro multiscale method, an exponential prediction model for the BSM positioning accuracy was developed considering time-varying working conditions (load and rotational speed) and feed modes. Since the accuracy degradation is mainly caused by wear, a microscopic approach was proposed to describe the positioning accuracy retention and the microscopic wear process was investigated. The sliding contact of the asperities between the ball and raceway was analyzed, and the microscopic wear behavior of the asperities was determined. Considering the time-varying working conditions, the BSM positioning accuracy characteristics were obtained under the normal feed mode by conducting suitable tests. The exponential wear model used the wear index to describe the wear status based on the positioning accuracy measurement. The accuracy loss value and the prediction index of positioning accuracy were determined based on an exponential model, and the effective lifetime of the BSM was predicted. Finally, the exponential prediction model was used in negative/positive skew feed distribution, and the effective lifetime determined.

In this paper, 30-slot/24-pole five-phase PMSM with hybrid single/double layer (HL) fractional-slot concentrated winding (FSCW) is designed for wheel-driving application in electric vehicles (EVs). Third harmonic current injection in different operating stages of the machine is investigated, including normal operation and fault-tolerant operation. HL FSCW machine is validated to be suitable for injecting third harmonic current to enhance torque by both theoretical analysis and finite-element analysis (FEA), and compared with 20-slot/24-pole single-layer (SL) and double-layer (DL) FSCW machine under constant rms and peak harmonic injection. Besides, a novel flux weakening control method with third harmonic current injection is proposed, which improves torque and efficiency of HL FSCW machine. The influence of nonlinearity caused by stator core saturation and higher order harmonics contained in back electromotive force (EMF) is included in flux weakening operation with harmonic injection. Finally, fault-tolerant control of HL FSCW machine with one-phase open-circuit fault is investigated, and two compensatory strategies with and without third harmonic current injection are proposed. Torque ripple caused by one-phase opencircuit fault is suppressed effectively by the proposed strategies.INDEX TERMS Permanent-magnet synchronous machine (PMSM), five-phase, fractional-slot concentrated winding (FSCW), third harmonic injection, flux weakening, fault-tolerant control, open-circuit.

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The combination of sliding/rolling motion can influence the degree of precision degradation of ball screw. Precision degradation modeling and factors analysis can reveal the evolution law of ball screw precision. This paper presents a precision degradation model for factors analysis influencing precision due to mixed sliding-rolling motion. The precision loss model was verified through the comparison of theoretical models and experimental tests. The precision degradation due to rolling motion between the ball and raceway accounted for 29.09% of the screw precision loss due to sliding motion. Additionally, the total precision degradation due to rolling motion accounted for 21.03% of the total sliding precision loss of the screw and nut, and 17.38% of the overall ball screw precision loss under mixed sliding-rolling motion. In addition, the effects of operating conditions and structural parameters on precision loss were analyzed. The sensitivity coefficients of factors influencing were used to quantitatively describe impact degree on precision degradation.

Transverse-flux with high efficiency has been applied in Stirling engine and permanent magnet synchronous linear generator system, however it is restricted for large application because of low and complex process. A novel type of cylindrical, non-overlapping, transverse-flux, and permanent-magnet linear motor(TFPLM) is investigated, furthermore, a high power factor and less process complexity structure research is developed. The impact of magnetic leakage factor on power factor is discussed, by using the Finite Element Analysis(FEA) model of stirling engine and TFPLM, an optimization method for electro-magnetic design of TFPLM is proposed based on magnetic leakage factor. The relation between power factor and structure parameter is investigated, and a structure parameter optimization method is proposed taking power factor maximum as a goal. At last, the test bench is founded, starting experimental and generating experimental are performed, and a good agreement of simulation and experimental is achieved. The power factor is improved and the process complexity is decreased. This research provides the instruction to design high-power factor permanent-magnet linear generator.