In this brief, a global finite-time adaptive attitude control algorithm is investigated for flexible spacecraft with slosh structure under model uncertainty, external disturbance, and actuator fault. First, the arctangent function (AF) surface is designed to realize the faster convergence time of quaternion-descripted attitude control system. Then, based on AF, an adaptive fault-tolerant control (FTC) algorithm is proposed to realize global finite-time attitude control of coupled spacecraft. The merit of the designed control algorithm is that it assumes that the upper bound of the lumped uncertainty (including model uncertainty related to angular velocity) is less than the combination of a positive constant, angular velocity, and control torque, rather than just less than a positive constant. The Lyapunov technique is used to prove the stability of whole closed-loop system. Numerical examples are performed to prove the efficiency of the designed control algorithm.

The Dual-Redundancy Permanent Magnet Synchronous Motor (DRPMSM) with weak thermal coupling and no electromagnetic coupling among phase windings has two sets of three-phase symmetrical windings. Under normal conditions, two sets of windings can operate simultaneously, and once one set has an inter-turn short circuit fault (ISCF), the other set will operate alone, so a DRPMSM can be applied in fields with high reliability requirements. According to the equivalent circuit principle, a simplified model of a DRPMSM when ISCF occurs is established in this paper, and mathematical equations for the equivalent resistance, inductance and induction electromotive force (EMF) are derived. Based on the simplified circuit principle and instantaneous power theory, combined with the analysis of the fundamental wave in the two sets, an online diagnosis method of the ISCF for DRPMSM is proposed based on the reactive power difference and the feasibility of the method is verified by experiments.

An online detection method for the inter‐turn short‐circuit fault (ISCF) of a dual‐redundancy permanent magnet synchronous motor (DRPMSM) is proposed. First, the electromagnetic relationships in a DRPMSM without mutual inductances are analysed theoretically upon the occurrence of the ISCF. Then, a simulation model of the motor with ISCF is established, and the arithmetic mean for the ratio of the squared amplitude difference between two sets of space voltage vectors to squared frequency is used to identify the faulty winding by the difference between the back electromotive force and impedance of the dual winding. It is shown to be valid even with variations in the load, speed, contact resistance, and number of short‐circuit turns. The simulation and experimental results thus verify the effectiveness of the proposed method.

The dual-redundancy permanent magnet synchronous motor (DRPMSM) has high reliability in its applications. Compared with the traditional permanent magnet synchronous motor (PMSM), small teeth were added to the stator in DRPMSM and its vibration has new characteristics. This paper derived the analytic expression of the radial electromagnetic force for PMSM in the air gap based on the Maxwell stress equation and summarized its sources. The simplified stator teeth model of the traditional PMSM and DRPMSM were established in 12-slot/10-pole (12s10p), and the analytical expression and Fourier expansion of radial electromagnetic force on the teeth were given. The electromagnetic and structural finite element models of the motor were established, and analyses of modal and harmonic response were carried out. The simulation results show that the stator vibration amplitude of DRPMSM is smaller than that of traditional PMSM at no-load and is also bigger under rated load. Furthermore, in order to guarantee the low amplitude of stator vibration under rated load for DRPMSM, the width of the small teeth should be smaller.

In this brief, a global finite-time attitude control algorithm is proposed for flexible spacecraft without angular velocity measurement. First, a global finite-time observer is designed to estimate unknown angular velocity, eliminating the assumption that the derivative of attitude angle or initial angular velocity is bounded. Based on the proposed observer, a non-overestimated adaptive terminal sliding mode control (ATSMC) algorithm is designed to realize global finite-time attitude control. The main feature of this brief is that the upper bound of lumped uncertainty considered in this brief is related to angular velocity rather than constant, which is more practical. The stability of entire closed-loop system is guaranteed by Lyapunov function. Finally, numerical simulations are given to illustrate the efficiency of the proposed control algorithm.

A novel dual-redundancy permanent magnet synchronous motor (DRPMSM) with small teeth is proposed, which combines the advantages of fault-tolerant permanent magnet synchronous motor (PMSM) and multi-phase PMSM. When fractional slot concentrated winding (FSCW) is used in PMSM, no electromagnetic coupling can be realized by selecting a reasonable slot-pole (SP) combination and using single-layer (SL) winding. However, the goal of no electromagnetic coupling can also be achieved by adding small teeth in the common slot center between two adjacent phase windings under appropriate SP combination and double layer (DL) winding. Compared with the former method, the latter has smaller eddy current loss and a lower saturation level of the magnetic field caused by lower-order harmonics. In addition, the influence of small teeth on electromagnetic properties is analyzed. The correctness of the theoretical derivation is verified by simulation and experiment.