With the development of mobile technologies, mobile applications are increasingly designed and developed. In the field of science, technology, engineering, and mathematics education, the idea of using mobile devices for teaching and learning has gradually gained popularity and gained in-depth research. Owing to the advantages of convenience, portability, and excellent interactive abilities, mobile devices are a good choice for accessing remote laboratories. In propose of promoting the massive online experimentation of control education, a mobile application with framework based on react-native is implemented in this article. The overall remote laboratory architecture adopts front-end and back-end separation scheme, which benefits the mobile application focusing on the construction of front-end interface and user experience. Various functional modules and technologies are applied in the mobile application, allowing users to access various experiment test rigs in the remote laboratory with intuitive experimental immersion. Moreover, a complete laboratory management system to manage the massive users from different universities has also been integrated into the mobile application. At the end, a remote networked control experiment has been conducted to prove the practicability of the mobile application.

Doubly salient electromagnetic generator (DSEG)is a new type of high reliability DC generator. This paper gives a brief introduction to the fault-tolerant control strategy for the excitation fault of DSEG, once the fault of excitation part occurs, the energy storage capacitor on the load side acts as excitation power and directly provides excitation for the armature windings through the switches on the converter when the rotor is in the specific position, and completes fault-tolerant operation. And two different winding current waveforms under the fault-tolerant control and their different reasons are analyzed with simulation and experiment results.

The influences of current amplitudes on four-phase 24/18-pole doubly salient electro-magnetic motor(DSEM) under fault-tolerant operation are studied in this paper. Taking average output torque, output torque ripple and stator copper losses into consideration, the optimal fault-tolerant current amplitude (FTCA) range is obtained. A four-phase full-bridge converter with two bilateral switches is applied to the fault-tolerant drive system. Once the fault of one phase open-circuit occurs, the bilateral switch connected to the faulty phase is switched on and the FTCA of the remaining three phases are adjusted to obtain the same excitation torque as that of normal operation. And the stator copper loss is analyzed as well. The relationship of average output torque, output torque ripple and FTCA are validated through co-simulations of Maxwell and Simplorer. At last, an optimal FTCA range, which ensures high output torque, low output torque ripple and low stator copper loss, is obtained.

This paper proposes a novel rotor angular position estimation method based on self-inductance rectangle for doubly salient electro-magnetic motor (DSEM). It starts with injecting three test voltage pulses A+C-, B+A- and C+B-with the same width in order. At the end of each test pulse, the response currents iac, ibaand icbare sampled and detected to identify the two-phase series inductances Lac, Lbaand Lcb, respectively. Thus the rotor sector is estimated by comparing Lac, Lbaand Lcb. In further, with finding the geometrical proportional relation in self-inductance rectangle which is composed of two-phase series inductances, the expression of rotor angular position is achieved. Compared with the traditional rotor position estimation method, rotor angular position rather than rotor sector is estimated under the proposed method, higher-accurate commutation with no lag is achieved, so DSEM sensorless startup performance is desired to be improved. Finally, the experiments on a 12/8-pole DSEM validate the correctness and flexibility of the proposed rotor position estimation method.

Advanced angle commutation is an effective approach to suppress the commutation torque ripple for doubly salient electromagnetic machine (DSEM). In this paper, the commutation process under “three-phase three-state” conduction mode is analyzed in detail at first. On this base, a novel self-optimizing control strategy of advanced commutation angle for DSEM is proposed, it starts with setting an initial disturbance of advanced commutation angle, then according to the feedback of command current, the output of outer speed loop, the advanced commutation angle is continuously regulated with the aim of decreasing command current. Therefore, the output torque/current ratio is increased, DSEM is desired to operate at the steady state with the smallest current, so the output torque performance as well as system efficiency are enhanced. With no requirement for system parameters, this proposed method can be easily implemented in any other quasi-square current motor systems with outer speed and inner current loops control. Finally, the experiments on a 12/8-pole DSEM validate the correctness of the proposed methods.

Full bidirectional switches two stage matrix converter (FBS-TSMC), which can be effectively used in critical applications, is presented. Comparing with traditional two stage matrix converter, it adds six additional switches to inverter stage as redundancy hot backup. Meanwhile, its bidirectional switches structure in inverter stage makes it possible to reverse dc bus voltage polarity. The above two features provide FBS-TSMC fault-tolerant capacity in the presence of faults. From the view of modulation, this paper proposes two fault-tolerant strategies for FBS-TSMC to deal with single switch short circuit failure and bidirectional switch open circuit failure in inverter stage respectively. By utilizing the characteristics of fault switch and increasing additional switch times in healthy phases, the proposed fault-tolerant strategies can ensure FBS-TSMC's satisfactory performance without modifying the control technique. A simulation model of FBS-TSMC has been built in Matlab/Simulink and the verification of the proposed fault-tolerant modulation strategy is confirmed using extensive simulation results.

In order to detect open-circuit fault in rectifier stage, a fault diagnosis method applied to indirect matrix converter (IMC) is proposed in this paper. Firstly, the theory and feature of space vector modulation (SVM) are introduced. Then, detailed circuit analysis of IMC under fault condition is fully studied, and from the view of energy transfer, the influence of open-circuit fault on output voltage is analysed. Based on the circuit analysis, this paper presents a fault diagnosis technology to detect and locate faulty switch by combining the corresponding relationship between the rectifier stage sector and bidirectional switch. The proposed method has the advantages of being easy to understand, locating faulty switch accurately, requiring no additional sensor in dc-link side. Simulation results are presented to verify the proposed fault detection technology.

This paper firstly proposes a novel sensorless control method for doubly salient electro-magnetic motor (DSEM) based on line-voltage difference. The commutation instants are estimated by comparing proper line-voltage difference and commutation threshold value, which is preset according to the varying feature of excitation back electromotive force (EMF) with motor speed, excitation current and rotor position. Then, the commutation lags caused by reluctance EMF and low-pass filter are analyzed in detail, and the quantitative relations of motor speed, armature current, excitation current and phase lags are obtained. On this basic, a direct uniform compensation strategy through adjusting the commutation threshold value is presented. Compared with traditional compensation methods, it has the merits of easy implementation and no extra hardware needed. The experimental results verify the correctness and feasibility of the proposed methods over a wide range of speed and load conditions.

In this correspondence, we give an average sampling theorem for bandlimited stochastic processes which shows that many average sampling theorems have their counterparts for stochastic signals.

The sampling theorem says that every band-limited signal is uniquely determined by its sampled values provided the sampling points satisfy certain conditions. However, sampled values obtained in practice may not be the exact values of a signal at sampling points, but only averages of the signal near these points. Grochenig (1992) proved that band-limited signals can be reconstructed exactly from local averages if the sampling density is large enough. We study the reconstruction of band-limited signals from local averages with symmetric averaging functions. We study the aliasing error arising when a non-band-limited signal is reconstructed from local averages and give explicit error bounds. Since the classical "point sampling" can be viewed as a limiting case of average sampling, we indeed give new aliasing error bounds for both regular and irregular sampling.