For an electrical six-degree-of-freedom Stewart platform, it is difficult to compute the equivalent inertia of each motor in real time, as the inertia is time-varying. In this study, an analysis using Kane’s equation is undertaken of the driven torque of the movements of motor systems (including motor friction, movements of motor systems along with the actuators, rotation around axis of rotors and snails), as well as driven torque of the platform and actuators. The electromagnetic torque was calculated according to vector-controlled permanent magnet synchronous motor (PMSM) dynamics. By equalizing the driven torque and electromagnetic torque, a model was established. This method, taking into consideration the influence of counter electromotive force (EMF) and motor friction, could be applied to the real-time dynamic control of the platform, through which the calculation of the time-varying equivalent inertia is avoided. Finally, simulations with typically desired trajectory inputs are presented and the performance of the Stewart platform is determined. With this approach, the multi-body dynamics of the electrical Stewart platform is better understood.

A low-cost fiber Bragg grating (FBG) sensing system for coal-mine security monitoring is proposed in this paper. Based on the coherence multiplexing (CM) and spatial division multiplexing (SDM) techniques, this hybrid sensing network can support more than 40 sensors for quasi-distributed detection. It is demonstrated experimentally that the multiplexed sensing signal of each sensor can be clearly distinguished by an optical low-coherence reflectometry (OLCR). Methane concentration is detected with maximum sensitivities of an intensity variation of 10.92% and a concentration variation of 1%, using a well-designed sensor structure. Strain and temperature are also detected by this system, which also exhibits good results in the experiment.

A suitable initial value of a good (close to the optimal value) scheduling algorithm may greatly speed up the convergence rate. However, the initial population of current scheduling algorithms is randomly determined. Similar scheduling instances in the production process are not reused rationally. For this reason, we propose a method to generate the initial population of job shop problems. The scheduling model includes static and dynamic knowledge to generate the initial population of the genetic algorithm. The knowledge reflects scheduling constraints and priority rules. A scheduling strategy is implemented by matching and combining the two categories of scheduling knowledge, while the experience of dispatchers is externalized to semantic features. Feature similarity based knowledge matching is utilized to acquire the constraints that are in turn used to optimize the scheduling process. Results show that the proposed approach is feasible and effective for the job shop optimization problem.

Unsupervised anomaly detection can detect attacks without the need for clean or labeled training data. This paper studies the application of clustering to unsupervised anomaly detection (ACUAD). Data records are mapped to a feature space. Anomalies are detected by determining which points lie in the sparse regions of the feature space. A critical element for this method to be effective is the definition of the distance function between data records. We propose a unified normalization distance framework for records with numeric and nominal features mixed data. A heuristic method that computes the distance for nominal features is proposed, taking advantage of an important characteristic of nominal features—their probability distribution. Then, robust methods are proposed for mapping numeric features and computing their distance, these being able to tolerate the impact of the value difference in scale and diversification among features, and outliers introduced by intrusions. Empirical experiments with the KDD 1999 dataset showed that ACUAD can detect intrusions with relatively low false alarm rates compared with other approaches.

For multiple-relay cooperative networks with multiple antennas deployed at source and destination nodes, we investigate the outage performance of selection based semi-blind amplify-and-forward (AF) relaying, where transmit beamforming (TB) is conducted at source transmission and maximum ratio combining (MRC) at destination reception. Based on the Kolmogorov-Smirnov test, we analyze the impact of the configuration of destination antennas on the outage performance under arbitrary Nakagami-m fading channels. Results reveal that increasing the number of destination antennas is not necessary for an improvement of outage performance with any Nakagami-m parameter. Inspired by this fact, an approximation is proposed for the optimal selection. Simulation results show that the approximation is an efficient selection method.

A novel semiconductor laser which can achieve mode-hop-free tuning is proposed. The device consists of an etched diffraction grating (EDG) as a dispersive element to provide the mode selection function and an active waveguide to provide optical gain for the laser. The slab waveguide region of the EDG contains a tuning section covered by an electrode to inject a tuning current, and thus changes the refractive index. Mode-hop-free tuning is achieved by specially designing the shape of the tuning section, so that the tuning rate of the central wavelength reflected by the EDG and the tuning rate of the resonant wavelength of the laser cavity are equal. An optimized tuning section shape is designed to obtain the largest tuning range within a limited current range. Numerical simulation is presented to demonstrate the mode-hop-free tuning operation.

We propose an efficient low bit error rate (BER) and low complexity multiple-input multiple-output (MIMO) multiuser detection (MUD) method for use with multiuser MIMO orthogonal frequency division multiplexing (OFDM) systems. It is a hybrid method combining a multiuser-interference-cancellation-based decision feedback equalizer using error feedback filter (MIMO MIC DFE-EFF) and a differential algorithm. The proposed method, termed ‘MIMO MIC DFE-EFF with a differential algorithm’ for short, has a multiuser feedback structure. We describe the schemes of MIMO MIC DFE-EFF and MIMO MIC DFE-EFF with a differential algorithm, and compare their minimum mean square error (MMSE) performance and computational complexity. Simulation results show that a significant performance gain can be achieved by employing the MIMO MIC DFE-EFF detection algorithm in the context of a multiuser MIMO-OFDM system over frequency selective Rayleigh channel. MIMO MIC DFE-EFF with the differential algorithm improves both computational efficiency and BER performance in a multistage structure relative to conventional DFE-EFF, though there is a small reduction in system performance compared with MIMO MIC DFE-EFF without the differential algorithm.

This paper proposes an analytical model for predicting the maximum vibration reduction level in a four-phase 8/6 switched reluctance machine (SRM) by employing active vibration cancellation (AVC), one of the most effective and convenient methods for reducing the vibration and acoustic noise produced by SRMs. Based on the proposed method, the factors that influence the vibration reduction level are analyzed in detail. The relationships between vibration and noise reduction levels at resonance frequency and rotor speed are presented. Moreover, it is shown that a large damping factor will lead to smaller vibration reduction level with AVC while, in contrast, a large resonance frequency will increase the vibration reduction level. Both finite element analyses and experiments were carried out on a prototype 8/6 SRM to validate the proposed method.

This paper deals with an improved direct power control (DPC) strategy for the pulse width modulation (PWM) voltage source converter (VSC) under unbalanced grid voltage conditions. In order to provide enhanced control performance for the VSC, the resonant controllers tuned at the double grid frequency are applied in the DPC design to eliminate the power pulsations and dc link voltage ripples produced by the transient unbalanced grid faults. In this way, the output power and dc link voltage of the VSC can be directly regulated without positive and negative sequential decomposition. As a result, and as has been verified by experiment, the proposed method can provide fast dynamic response with easy implementation.

In underwater applications of contactless power transmission (CLPT) systems, high pressure and noncoaxial operations will change the parameters of electromagnetic (EM) couplers. As a result, the system will divert from its optimum performance. Using a reluctance modeling method, we investigated the gap effects on the EM coupler in deep-sea environment. Calculations and measurements were performed to analyze the influence of high pressure and noncoaxial alignments on the coupler. It was shown that it is useful to set a relatively large gap between cores to reduce the influence of pressure. Experiments were carried out to verify the transferring capacity of the designed coupler and system for a fixed frequency. The results showed that an EM coupler with a large gap can serve a stable and efficient power transmission for the CLPT system. The designed system can transfer more than 400 W electrical power with a 2-mm gap in the EM coupler, and the efficiency was up to 90% coaxially and 87% non-coaxially in 40 MPa salt water. Finally, a mechanical layout of a 400 W EM coupler for the underwater application in 4000-m deep sea was proposed.