Recent Advances in Electrical & Electronic Engineering - Volume 10, Issue 2, 2017

Background: A secure, flexible and robust intra-cluster key management framework is proposed as a general solution to establish the pairwise key between a sensor and its cluster head in sensor networks. Methods: Based on the classical low-energy key management (LEKM) protocol, this framework employs the threshold secret sharing in the key pre-distribution and pairwise key establishment phases. Results: Compared to the LEKM protocol, the framework inherits the low-energy advantage and improves the flexibility, the robustness, and the resilience against node capture attacks. Conclusion: Theoretical analysis and simulation prove that this framework has many advantages: firstly, it improves the security against node capture attack compared to probabilistic schemes; secondly, it is flexible in key revocation/renewal operations by using the threshold technique; thirdly, it is robust against CH nodes capture attack, which is achieved by guaranteeing high connectivity after node recovery. At last, it inherits the energy-efficient property of the LEKM protocol, which is optimal in saving the energy consumption of low-power sensors.

Background: Several approaches have been proposed for monitoring and diagnosis of the induction machine. Although, most of them focus on a single fault, but in a real rotator machine, two or more defects can be present simultaneously. Furthermore, one faulty condition could impair the detection of a differing fault and a wrong decision about the operational status of the machine. Method: In addition, there are several types of rotor faults as broken rotor bars and eccentricities. Different types of eccentricities (static, dynamic and mixed) at different degrees were studied in the presence of the broken rotor bars. Eccentricities of both the natures usually exist together due to necessary tolerances in the manufacturing process. This study sets out to examine the faults possibilities which can occur in the machine using the finite element method. The air-gap magnetic flux density is used to investigate rotor faults. At first, the isolated fault such as broken rotor bars, static and dynamic eccentricities are analysed. Then, combined faults (mixed eccentricity) and multiple-combined faults (both mixed eccentricity and the broken rotor bars) are treated. The finite elements method is used to create these faults. Result: These faults are monitored by internal magnetic field signature, which is used for examining the effect of the increases of static eccentricity in dynamic eccentricity and vice versa. Furthermore, the same value of ME with different rates of static and dynamic is analysed. Conclusion: The multiple-combined faults are investigated considering the effect of broken rotor bars in mixed eccentricity.

Background: Mobility management is one of the most important challenges in next generation wireless networks (NGWNs) as it enables users to move across geographic boundaries of wireless networks. Nowadays, mobile communications have heterogeneous wireless networks offering variable coverage and Quality of Service (QoS). The availability of alternatives generates a problem of occurrence of unnecessary handoff that results in wastage of network resources. To avoid this, an efficient algorithm needs to be developed to minimize the number of handoffs. Conventionally, whenever a wireless local area network (WLAN) connectivity is available, the mobile node switch from cellular network to wireless local area network (WLAN) network to gain maximum use of high bandwidth and low cost of wireless local area network (WLAN) as much as possible. But to maintain call quality and minimum number of call failure, a considerable proportion of these handovers should be determined. Our algorithm makes the handoff to wireless local area network (WLAN) only when the predicted travelling distance inside the wireless local area network (WLAN) is larger than a threshold value. Methods: A novel handoff necessity estimation approach based on travelling distance and an optimum handoff target network selection algorithm. Results: Through MATLAB simulation, we show that our algorithm minimize the probability of unnecessary handoff, probability of handoff failure, and selects an optimum target network from the available network based on bandwidth, cost, and power consumption. Conclusion: It is able to improve handover performance and user’s satisfaction level by offering the best quality of services to user all the time through optimum target network selection.

Background: It is easy to carry out a wide range of high-precision micro movement on the magnetic levitation stage which also turns to be suitable in precision manufacturing and ultra-precision measurement field. In view of the strong coupling and nonlinear characteristics of the dynamic model of the sandwich layer structure, the differential geometry soft variable structure control method is proposed. Method: Based on differential geometry theory, the study of state feedback linearization for dynamic model of the magnetic levitation movement stage is conducted, which implements the exact linearization and decoupling in the vertical and horizontal subsystems of the stage. The soft variable structure controller with variable saturation is designed according to the linear model of the subsystem. Result: The simulation results show that the control method is able to achieve better performance than the PID and sliding mode controller and satisfy the requirement of precision positioning.

Background: In state-of-the-art nanometer metal-oxide-semiconductor-field-effecttransistors (MOSFETs), threshold voltage (VT) and drain-induced-barrier-lowering (DIBL) variations are regarded as significant challenges in circuit analysis, design and characterization. Method: This paper proposes the improved analytical models to correctly describe VT and DIBL variations due to random gate length fluctuation employing the propagation of variation (POV) methodology. Result: The presented models are validated that they can accurately capture VT and DIBL’s statistical characteristics through Monte Carlo simulations for MOSFET devices with 22nm process technology. Furthermore, our models and simulations both revealed that VT and DIBL variations will increase dramatically with gate length shrinking for nanometer MOSFETs. Conclusion: The proposed statistical modeling approach provides a useful pathway for processvariation- aware circuit design.

Background: A new reflector antenna is proposed in this paper. The antenna is constructed from a semi-toroidal reflector, which is fed by a circular loop antenna (CLA). Method: The input impedance, reflection coefficient, directivity, radiation patterns, current density on the reflector and current distribution on the loop for different geometries of the proposed antenna were investigated theoretically in this paper. It was found that at resonance frequency, a larger directivity than that of a loop over a ground plane can be obtained. These antennas can give a directivity approaching 12 dB with reflection coefficient less than -10 dB. Furthermore, a reflection coefficient of about -24 dB can be obtained with directivity of 8.3 dB. Result: On the other hand, when the cross section of the semi-toroidal reflecting approached zero, the behaviour of the antenna was similar to that of two elements array of circular loops.

Background: Ultrasonic motor is a typical nonlinear system with significant time-varying characteristics. In this paper, the position control of ultrasonic motor is comprehensively studied. Method: Firstly, a Hammerstein model is established to obtain the characteristic form of the motor operation, followed by the establishment of an inverse control model aiming to handle the nonlinear characteristic of the ultrasonic motor. By canceling the nonlinear component, the motor is modeled as a linear system and the controller is also designed linearly. The direct multi-step predictive control strategy is then designed and used to realize the precise position control on the basis of stable motor operation. Conclusion: The experimental results show that the proposed control algorithm has superior tracking behavior and small steady-state error when the structure or parameters of the controlled object change.

Background: Most doctors are used to locate the vascular stenosis position first then clinically estimate vascular stenosis by the CAG images instead of using mouse, keyboard and computer during the preoperative diagnosis. Therefore, it is necessary to have an effective, intuitive and natural method to replace the existing preoperative diagnosis mode for diagnosing the coronary heart disease. Methods: This work presents the gesture interactive diagnostic method for coronary heart disease based on wavelet transform and Semi-continuous Hidden Markov Model in Augmented Reality. Firstly, the dynamic gesture trajectory is analyzed by using K-means cluster algorithm to determine the gesture trajectory plane. Secondly, the integrity of the trajectory is preserved on the sensor plane by employing trajectory projection and space rotation transformation. Thirdly, the features include the azimuth of gesture trajectory and the changes of hand shape are extracted. Meanwhile, the azimuth of gesture trajectory is analyzed by utilizing wavelet transform and the singularity of the trajectory is detected to compute the state number of SCHMM for all the dynamic gestures. The gesture training is completed by employing Baum-Welch algorithm with multi-features and multi-observation sequences. Ultimately, gesture recognition is realized by using Viterbi algorithm based on self-learning mechanism. It is then applied into the gesture interactive diagnosis of coronary heart disease and the diagnosis of the vascular stenosis are intuitively and naturally realized with augmented reality and gesture interactive techniques. Results: The number of states of dynamic gesture is determined by using wavelet transform which precisely detect singular points of gesture trajectory. The recognition rate of dynamic gesture is average of 96.1% and the semi-dynamic gesture is average of 92.6%, the total recognition rate is average of 95.6%. The dynamic gesture recognition rate of the proposed method is 7% higher than the traditional method. The intuitive and natural gesture interactive experiments and the affirmed measuring results are approved by surgeons. Conclusions: The proposed method is a feasible, usable and reliable gesture interactive diagnostic method for coronary heart disease based on wavelet transform and Semi-continuous Hidden Markov Model in Augmented Reality. The results demonstrate that the proposed method could improve the gesture recognition rate, extend the gesture manipulation space and expand the diagnostic method for coronary heart diseases.

Background: Multi-axis servo driver based on FPGA is designed and implemented for the control of multiple alternating current (AC) servo motors in one numeric control (NC) system. Owing to the parallelism of field programmable gate array (FPGA), the highly integrated architecture not only reduces the spatial volume of the control system, but also improves the harmonious ability between different motors. Method: Moreover, the proposed predictive control method for each one axis not only improved the accuracy of position tracking and speed tracking, but also reduced the current fluctuation of the motor when its speed was changed. The methods implemented in this paper improved the response swiftness of NC systems. Conclusion: The measurements of current loop, speed loop and position loop on the three-axis machine can validate this algorithm.

Background: In this paper, detection of microwave radiations at room temperature using PtSi Schottky junction sensors is studied. This is made possible by fabricating a porous substrate over which the PtSi electrode was deposited. N-type Si substrates are made porous and Pt is electrochemically deposited into the pores. Methods: Pt is annealed and the resulting PtSi/porous Si Schottky junction exhibits a breakdown type behavior at its reverse bias mode. The magnitude of the breakdown voltage depends on several factors. This breakdown voltage is sensitive to microwave radiations. When the sensor receives a microwave radiation, its breakdown voltage decreases based on the magnitude of the radiation. The sensor is highly sensitive to the power of microwave radiations even in mW range. Conclusion: The Schottky diode sensor is almost insensitive to the signal frequency in the frequency range studied in this investigation. The best responsivity is obtained for the signal with the guide wavelength of 4.8702 cm. Instead of a coplanar waveguide (CPW), a rectangular waveguide is used in the current investigation. This eliminates the need for complicated impedance matching circuits.

Background: During the process of extracting three-dimension (3D) dynamic characteristics of remote sensing image, the extraction effect is vulnerable to be influenced by gray value and gradient of remote sensing image. When the traditional algorithm is used in extracting 3D dynamic characteristics of remote sensing image, due to the changes of pixel gray value and gradient in remote sensing image, pixel weights are interfered, and the traditional algorithm is unable to tract the change of picture element, resulting in poor extraction effect of 3D characteristics. Method: For this, a method for 3D dynamic characteristics extraction of remote sensing images is proposed based on optical flow analysis. 3D space information of reflection point is extracted from remote sensing image sequence as the basis of 3D dynamic feature extraction. The change of picture element in every frame of remote sensing image is tracking, to establish the corresponding relation of picture element and remote sensing images, so as to achieve the extraction of target image 3D dynamic feature. Result: Simulation experimental results show that the improved algorithm can extract 3D dynamic characteristics from remote sensing images accurately, and the effect is satisfactory.