The distortion of air gap magnetic field caused by the rotor eccentricity contributes to the electromechanical coupling vibration of the brushless DC (BLDC) permanent magnet in-wheel motor (PMIWM) in electric vehicles (EV). The comfort of the BLDC in-wheel motor drive (IWMD) EV is seriously affected. To deeply investigate the electromechanical coupling vibration of the PMIWM under air gap eccentricity, the PMIWM, tyre and road excitation are analyzed first. The influence of air gap eccentricity on air gap magnetic density is investigated. The coupling law of the air gap and the unbalanced magnetic force (UMF) is studied. The coupling characteristics of eccentricity rate, air gap magnetic density, UMF, phase current and vibration acceleration are verified on the test bench in the laboratory. The mechanism of the electromechanical coupling vibration of the BLDC PMIWM under air gap static eccentricity (SE), dynamic eccentricity (DE) and hybrid eccentricity (HE) is revealed. DE and HE deteriorate the vibration acceleration amplitude, which contributes the electromechanical coupling vibration of the PMIWM. The research results provide a solid foundation for the vibration and noise suppression of the PMIWM in distributed drive EV.

There exists a need in a quality and accuracy of a three-dimensional laser metrology operating in numerically controlled automatic machines. For this purpose, one sends three laser beams mutually perpendicular. These three beams of the wavelength λ = 0.6328 μm are generated by the same laser and are directed along three independent, orthogonal, mutually perpendicular, optical paths with a given light polarization plain. Using these beams, constituting the frame of coordinates, three independent laser rangefinders are able to determine spatial coordinates of a working tool or a workpiece. To form these optical pulses, a special refractive index matched Half-Wave Plate with nematic Liquid Crystal (LCHWP) was applied. The presented half-wave plate is based on a single Twisted Nematic (TN) cell (with the twist angle Φ = π/2) of a rather high cell gap d ~15 μm filled with a newly developed High-Birefringence Nematic Liquid Crystal Mixture (HBLCM) of optical anisotropy as high as Δn ~0.40 at λ = 0.6328 μm, where the Mauguin limit above 5.00 ~ Δnd >> λ/2 = 0.32 is fulfilled.