International Journal of Applied Electromagnetics and Mechanics - Volume 52, issue 3-4

Authors: Cao, Sheng | Kazuki, Nishida | Quan, Changqin | Luo, Zhiwei

Article Type: Research Article

Abstract: Upper limbs cooperative movement functions are very important for us in our everyday life. Due to many kinds of brain diseases, people usually reduced or even lost their half side of body's motion activities, which made it difficult to realize cooperative movements between right and left limbs and in turn greatly reduced their quality of live. In this research, we developed a novel robot system which integrates with virtual reality technologies to perform rehabilitation of upper limbs' cooperative movement functions, such as to realize simultaneous upper limbs' motions or to cooperatively catch and setting a common object in a 3 …D work space. Three types of rehabilitation movements are designed so that the subject can train their each arm along as well as cooperative movements in a game style. The motion trajectories as well as the contact forces with objects are automatically recorded which can be used to evaluate the performance of rehabilitation, effectively. Show more

Keywords: Cooperative movement, rehabilitation, robot, virtual reality

DOI: 10.3233/JAE-162088

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 943-950, 2016

Authors: Okuyama, Takeshi | Kobayashi, Kohei | Otsuki, Manabu | Tanaka, Mami

Article Type: Research Article

Abstract: This paper aims to develop a measurement system for the finger joint angle by using a flexible polymer sensor. In rehabilitation, it is important to evaluate human motions quantitatively for effective treatment. In this study, we focus on hand's grasping motion, which is important motion for eating and drinking. About the flexible polymer sensor, in the previous studies, it has been elucidated that the outputs from the flexible polymer sensor are proportional to the average curvature of measuring surface. Therefore, using the sensor, finger bending motion can be measured by attaching the sensor on finger surface. Firstly, the relationship between …the average curvature of finger surface and finger joint angle is theoretically investigated. Then, in order to obtain the relationship between sensor outputs and finger joint angles, sensor outputs and finger joint angles during grasping acrylic cylinders are measured. From the results, it was found that the developed system is useful to measure the finger joint angles. Show more

Keywords: Finger joint angle, measurement, flexible polymer sensor, human motion analysis, grasping motion

DOI: 10.3233/JAE-162091

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 951-957, 2016

Authors: Xu, Jia | Kong, Yingxiao | Zhu, Zhiwen

Article Type: Research Article

Abstract: A kind of magnetic shape memory alloy (MSMA) gripper is proposed in this paper, and its nonlinear dynamic response in bounded noise and harmonic magnetic fields is described. The traditional SMA gripper has slow response limited to the response characteristics of SMA. In this paper, MSMA film is applied in gripper to substitute the traditional SMA film to improve the response speed. Nonlinear differential items are introduced to interpret MSMA's hysteretic phenomena, and the nonlinear dynamic model of the MSMA gripper in bounded noise and harmonic magnetic fields is developed. The dynamic response of the system is obtained, and the …bifurcation characteristics of the system are analyzed. The results of numerical simulation and experiments show that the stochastic noise intensity has important influence on the system's dynamical response, and the heteroclinic orbit occurs with the stochastic noise intensity variety. The results of this study are helpful for the application of MSMA gripper in engineering fields. Show more

Keywords: Magnetic shape memory alloy (MSMA), gripper, hysteretic nonlinear characteristics, bifurcation

DOI: 10.3233/JAE-162046

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 959-966, 2016

Authors: Ma, Guoliang | Xu, Minglong | An, Zengyong | Wu, Chengsong | Miao, Weikai

Article Type: Research Article

Abstract: In this paper, the vibration characteristics and active vibration control of axially moving cantilever structure are investigated. The free vibration equation of axially moving cantilever beam with different lengths and tip masses is derived from the Hamilton's principle, and the natural frequency and modal function are calculated by using complex modal analysis. Macro Fibre Composite (MFC) patches are utilized as actuator and sensor in combination with proportional plus derivative (PD) control and Fuzzy control to establish the closed-loop feedback system, aiming to control the transverse vibration of the axially moving cantilever structure. And then, the active vibration control experiment is …implemented. The numerical example illustrates that length and tip mass affect vibration characteristics significantly. The experimental results suggest that the MFC actuator and sensor are effective on suppressing the vibration. Show more

Keywords: Active vibration control, MFC, axially moving cantilever structure, PD control, fuzzy controls

DOI: 10.3233/JAE-162113

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 967-974, 2016

Authors: Tang, Jianfei | Yan, Gang | Cai, Chenning

Article Type: Research Article

Abstract: This paper proposes a probabilistic approach to localize acoustic emission (AE) source in plate-like structures using particle filter (PF) with consideration of uncertainties from modeling error and measurement noise. The AE signals acquired by piezoelectric sensors are first processed by a complex wavelet transform to extract the time of arrival (TOA) information. Then localization of the AE source is formulated as a Bayesian state estimation problem with the source location and the wave velocity as unknown state parameters. A PF procedure is developed to iteratively estimate the unknown parameters simultaneously by using the TOA data. Experimental studies on a stiffened …aluminum panel with AE events simulated by pensile lead breaks (PLBs) are conducted to demonstrate the effectiveness of the PF-based AE localization method. Show more

Keywords: Acoustic emission, source localization, particle filter, uncertainty

DOI: 10.3233/JAE-162188

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 975-981, 2016

Authors: Wang, Jianying | Wang, Cheng | Zhong, Bineng | Wang, Tian | Guo, Wangping | Chen, Weibin | Sun, Chengzhu

Article Type: Research Article

Abstract: Due to ill-conditioned inverse characteristics of linear time invariant dynamic system uncorrelated multi-sources load identification in frequency domain, it have large condition number and errors for classic least-squares of generalization method. In order to overcome these shortcomings, an improved Tikhonov regularization method is put forward in this paper. This method uses minimization maximum relative error of identification multi-sources load as criterion to determine the optimal regularization parameter. At the same time, combination of improved Tikhonov regularization and least square of generalized matrix inverse method can reduce the time overhead of determining the best value of regularization parameter. Only when condition …number in a frequency is larger than a threshold value, must the improved Tikhonov regularization is used. Uncorrelated multi-sources vibration load identification in frequency domain results on cylindrical shell simulation datasets shows that this new method works much better than classic least-squares of generalized matrix inverse when measurement noise exists and could basically meet the engineering precision requirement of ± 3 dB. Show more

Keywords: Uncorrelated multi-sources load identification, frequency domain, Tikhonov regularization, least-square of generalized matrix inverse, minimization maximum relative error

DOI: 10.3233/JAE-162199

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 983-990, 2016

Authors: Zhang, Yu | Huang, Songling | Wang, Shen | Wei, Zheng | Zhao, Wei

Article Type: Research Article

Abstract: This work proposes an EMD-based STFT flight time extraction method to recognize the different modes of overlapped Lamb wave detecting signals (OLWDS) in aluminum plate due to its dispersion and multi-modes property. Firstly, empirical mode decomposition (EMD) is performed on the OLWDS and several intrinsic mode functions (IMFs) are obtained, which turn out to be capable of clearly separating the OLWDS of different modes. Secondly, the flight time is extracted from one of the IMFs by implementing short-time Fourier transform (STFT) on the selected IMF, and extracting the energy density distribution based on the center frequency component of Lamb waves. …The experimental platform for different modes of OLWDS recognition in aluminum plate is established. The results show that this method can extract more accurate flight time values compared with the Hilbert-Huang transform (HHT) method and can accurately recognize the overlapped Lamb waves of different modes. Show more

Keywords: Lamb waves, mode recognition, empirical mode decomposition (EMD), short-time Fourier transform (STFT)

DOI: 10.3233/JAE-162216

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 991-998, 2016

Authors: Guan, Wei | Wang, Cheng | Chen, D.S. | Luo, Xiangyu | Su, F.F.

Article Type: Research Article

Abstract: To update the model on-line and track the changing instantaneous modal shapes and modal frequencies of slow time-varying systems under unobservable random excitation operating conditions, a novel time-domain on-line operational modal analysis (OMA) algorithm based on recursive principal component analysis (RPCA) with forgetting factor is addressed. The algorithm is to update the covariance matrix with forgetting factor, and eigenvalues and eigenvectors tokened system properties are acquired. Finally, numerical simulations with three-degree-of-freedom system with time-varying mass are used to illustrate this method.

Keywords: Operational modal analysis (OMA), linear time-varying system, instantaneous modal parameters, recursive principal component analysis (RPCA), forgetting factor, on-line

DOI: 10.3233/JAE-162187

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 999-1006, 2016

Authors: Wu, Jianbo | Fang, Hui | Wang, Jie | Kang, Yihua

Article Type: Research Article

Abstract: Eddy current effect essentially occurs when relative movement happens between steel pipe and axial magnetization coil in Hi-speed MFL (magnetic flux leakage) testing. Based on the forming mechanism of eddy-current, the eddy-current magnetic field distributions in different parts were obtained, and it was found that the eddy-current magnetic field and the original magnetizing field in pipe tail have the same direction, resulting in the increase of the magnetization intensity; however, the direction of the eddy-current magnetic field is opposite to the one of the original magnetizing field in pipe head, which brings about the reduction of magnetization intensity; and that …the eddy-current magnetic field in pipe body nearly has no influence on the magnetization. Due to the different magnetization intensity in different parts of the steel pipe, sensitivity difference is formed, lowering the accuracy of MFL testing. Further, the elimination method for sensitivity difference by building extending magnetic pole was proposed. Lastly, the relevant experiments for steel pipe were conducted to verify the influence of the eddy-current magnetic field and the effectiveness of elimination method. Show more

Keywords: MFL (Magnetic flux leakage), steel pipe, eddy-current magnetic field, sensitivity difference, extending magnetic pole

DOI: 10.3233/JAE-162150

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1007-1014, 2016

Authors: Cai, Chenning | Yan, Gang | Tang, Jianfei

Article Type: Research Article

Abstract: This paper presents an experimental study for detecting fatigue cracks near a hole in an aluminium coupon under complex environment effects using guided waves and a Bayesian statistical inference method. Experimental set-up is established to simulate the combined conditions of temperature, load and vibration. PZT transducers are mounted on the coupon to excite and receive guided waves, and random samples of guided wave signals under different environmental conditions before and after cracking are recorded. After features of the guided wave signals in the frequency domain are extracted, a Bayesian interval hypothesis testing is employed to assess the feature differences of …the two states to make inference that whether fatigue cracks exist or not and give a confidence level. Experimental results have demonstrated the effectiveness of the proposed method. Show more

Keywords: Crack detection, guided waves, Bayesian inference, environmental effects

DOI: 10.3233/JAE-162189

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 3-4, pp. 1015-1021, 2016