We consider the DOA estimation problem by using adaptive nulling antenna technology and bias-compensated adaptive filtering framework. The adaptive nulling antenna array consists of one reference antenna element and multiple auxiliary antenna elements, which is capable of forming nulls in certain directions. By defining the reciprocal of array pattern as the spatial spectrum, the DOA estimation problem is considered as the peak searching for it. In this paper, we present an efficient bias-compensated adaptive filtering algorithm for DOA estimation, which is based on the adaptive nulling array. First of all, considering that both signals of interest (SOI) and noises are present at the auxiliary elements, we provide the noise-free mean square error (NF-MSE) cost function associated with the adaptive nulling array. Secondly, the proposed algorithm, called variable step-size bias-compensated least mean square (VSS-BC-LMS) algorithm, can be derived by minimizing the NF-MSE. Due to the noise compensation, the bias of the estimated weight vector is canceled and we can obtain a global optimal solution of the weight coefficients in connection with the auxiliary elements. More importantly, in order to resist the unsatisfactory DOA estimation performance when using the fixed step-size, a variable step-size scheme is introduced. And then, its mean stability, steady-state mean square performance and computational complexity are discussed. Additionally, we also explore a noise variance estimation method for calculating the bias term. Simulation results indicate that the proposed algorithm achieves an improved DOA estimation performance compared with other adaptive methods.

This letter proposes a set‐membership normalised least M‐estimate algorithm based on Wiener spline adaptive filter (SAF). The proposed algorithm combines the set‐membership framework and least‐M estimate scheme, thus achieving faster convergence rate and effective suppression of impulsive noise on the filter weight and control point adaptation. Simulation results demonstrate that the proposed one exhibits more robust performance compared to the conventional SAF algorithms in an impulsive noise environment.

In this study, a novel field-oriented control (FOC) algorithm was proposed in a 60° coordinate system for controlling the speed of permanent magnet synchronous motors. The FOC algorithm consists of several parts in which the reference currents and feedback currents are transformed into the representation form in a 60° coordinate system. Current regulators are typically used in a 60° coordinate system to directly obtain the reference voltage vector. The proposed FOC structure was established by incorporating the space vector pulse width modulation algorithm in a 60° coordinate system. The proposed FOC structure simplified the FOC algorithm and reduced its computational burden. The feasibility of the proposed method was verified through simulations and experiments.