Multiphase electrical machines have gained increased attentions recently due to its fault tolerance capability which is of great importance for more-electric aircraft application. This paper studies sensorless control of a highspeed dual three-phase electrical machine for turboprop aircraft green taxiing motor and engine generator applications. After introduction of a detailed mathematical model of a dual three-phase permanent magnet machine, two different types of back EMF based sensorless control are compared in this paper. The first method uses a phase-locked-loop (PLL) type speed and rotor position estimator and the other uses a Luenberger observer estimator. The effectiveness of these two different methods is demonstrated using simulations in the Matlab/Simulink environment. The comparison studies show that Luenberger type estimator has better dynamic performance but suffers high frequency noise in the estimated speed error and requires the use of machinal parameters. In contrast, PLL type estimator has inferior but acceptable performance. Its low-pass characteristics frees it from the high frequency noise. Moreover, it does not require the use of mechanical parameters.

This paper presents a decoupled modeling method for asymmetrical dual three phase (DTP) permanent magnet synchronous machine (PMSM). Due to the special structure of this machine, traditional decoupled method cannot be applied on it. This paper proposes a new method that applying inverse voltage to two sets of windings and transferring 6 phase model to a symmetrical 3 phase model, which d-q decoupled control can be used. Simulation result shows the equivalent symmetrical model has exact the same dynamic and steady performance with the asymmetrical dual three phase model.

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We consider the synthesis of discrete finite-alphabet inputs for secure communications in multiple-input-single-output wiretap channels. We aim that the source with the synthesized transmissions can communicate with a legitimate receiver and degrade the performance of a potential eavesdropper. To this end, we formulate an optimization problem to minimize the Euclidean distance between the reference inputs and the synthesized inputs. We devise an iterative algorithm to tackle the non-convex design problem with constant-envelope constraints. Moreover, we extend the proposed methodology to deal with low peak-toaverage-power ratio transmissions. The numerical examples demonstrate that the proposed algorithms can achieve the requirement of secrecy communications efficiently. INDEX TERMS Transmission design, secrecy communication, constant-envelope, peak-to-average-power ratio (PAPR), MISO wiretap channel.

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