An Ag-graphene layers-coated H-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor with a U-shaped grooves open structure for refractive index (RI) sensing is proposed and numerically simulated by the finite element method (FEM). The designed sensor could solve the problems of air-holes material coating and analyte filling in PCF. Two big air-holes in the x-axis produce a birefringence phenomenon leading to the confinement loss and sensitivity of x-polarized light being much stronger than y-polarized. Graphene is deposited on the layer of silver in the grooves; its high surface to volume ratio and rich π conjugation make it a suitable dielectric layer for sensing. The effect of structure parameters such as air-holes size, U-shaped grooves depth, thickness of the silver layer and number of graphene layers on the sensing performance of the proposed sensor are numerical simulated. A large analyte RI range from 1.33 to 1.41 is calculated and the highest wavelength sensitivity is 12,600 nm/RIU. In the linear RI sensing region of 1.33 to 1.36; the average wavelength sensitivity we obtained can reach 2770 nm/RIU with a resolution of 3.61 × 10⁻⁵ RIU. This work provides a reference for developing a high-sensitivity; multi-parameter measurement sensor potentially useful for water pollution monitoring and biosensing in the future.

This paper presents a novel adaptive commutation error compensation strategy for the sensorless brushless DC (BLDC) motor based on the flux linkage function. It addresses the two key challenge problems on the sensorless control of the BLDC motor. The one is presenting a novel detection method for the BLDC motor rotor position signal to filter out the interference and the noise by the high frequency. The other one is proposing a commutation error compensation strategy to improve the system efficiency. In traditional sensorless control strategy, a deep low pass filter is usually used to obtain the BLDC motor rotor position signal from the high frequency interference. However, the delayed angle caused by the low pass filter may be more than 90 electrical degrees in the high speed range. Therefore, a novel sensorless control strategy based on the speed–independent flux linkage function was proposed in this paper. The interference of the diode freewheeling was filtered by the software filter, and a closed–loop compensation algorithm based on the deviation of line–to–line voltages was illustrated to correct the commutation error in the high speed range. The stability and accuracy of the method was confirmed by a series of experiments.