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2020, 40(11): .

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2020, 40(11): .

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Dynamic Model of 6-DOF Underwater Manipulator and Its Influence of Flow Resistance

WANG Yi, ZHANG Ai-xia, GUO Rui-yan, ZHANG Cheng-liang

2020, 40(11): 1143-1149. doi:10.15918/j.tbit1001-0645.2019.207

Abstract(1188) PDF(546)

Abstract:
In this paper, a dynamic modeling method was carried out for the flow resistance influence analysis of a six-degree-of-freedom (6-DOF) underwater manipulator applied in deep water environment. Considering the influence of fluid resistance, a dynamic model of underwater manipulator was established based on iterative Newton-Euler vector mechanics method and Morison equation. According to the obtained analytical expression of the hydrodynamic moment for the base joint and append mass moment, the driving torque and water resistance moment of the base joint were derived for the 6-DOF manipulator. A simulation test was completed with Matlab software. The results show that, the influence of water resistance on the control moment of the manipulator can rise up to 8.69%, meaning that the influence of water resistance on the manipulator can not be ignored. In some cases of underwater high-precision operation, the application of the proposed 6-DOF underwater manipulator dynamic model, considering the influence of water resistance, can achieve higher control accuracy.

Optimal Design and Dynamic Performance Analysis of Single Coil Magnetorheological Damper Based on DOE and RSM

HU Guo-liang, YI Feng, ZHANG Jia-wei, YU Li-fan

2020, 40(11): 1150-1160. doi:10.15918/j.tbit1001-0645.2019.210

Abstract(1065) PDF(411)

Abstract:
A single coil magnetorheological damper (MRD) was designed, and the mathematical model of damping force was also deduced. In order to obtain an optimal performance of the MRD under a fixed external dimension, the approximate response function of magnetic field density and design variables was obtained based on design of experiments (DOE) and response surface methods (RSM). The objective function was established to obtain the optimal geometric parameters of MRD. The electromagnetic field simulation and dynamic performance simulation was carried out, and the dynamic test rig was set up. The dynamic performances were investigated under different currents, frequencies, amplitudes and damper velocities. The experimental results show that the output damping forces can be continuously adjusted, which show a better dynamic performance. The maximum output damping force of the optimized MRD can reach 560 N, while the value of the initial MRD is only 253 N; the maximum adjustable range of the optimized MRD is 4.8, and the adjustable range of the initial MRD is only 3.7. The optimized MRD can achieve a better dynamic performance.

A Fault Diagnosis Method for Planetary Gearbox Based on GAF-CNN

PANG Xin-yu, TONG Yu, WEI Zi-han

2020, 40(11): 1161-1167. doi:10.15918/j.tbit1001-0645.2020.064

Abstract(1153) PDF(515)

Abstract:
In order to apply the advantages of deep learning to recognize 2D images for the fault diagnosis of planetary gearboxes, a fault diagnosis model of planetary gearboxes based on gram angle field-convolution neural network (GAF-CNN) was proposed. Using two methods, gram angle difference field (GADF) and Gram angle sum field (GASF) in the gram angle field (GAF), the planetary gearbox vibration signal was converted into a 2D image, and the image features were extracted and input into the optimized CNN model, and the ideal recognition accuracy was finally obtained. Analyzing the influence of network parameters and different network layers on the fault diagnosis model, an optimal model combination was carried out. The test and comparison analysis results show that GADF-CNN can provide higher recognition accuracy than GASF-CNN; GADF-CNN is superior to other intelligent algorithms in the faults diagnosis of planetary gearbox.

The Critical Man-Rifle Characteristics of Shooting Process with Typical Rifle

WANG Yuan, WANG Ya-ping, XU Cheng

2020, 40(11): 1168-1173,1189. doi:10.15918/j.tbit1001-0645.2019.196

Abstract(820) PDF(410)

Abstract:
The purpose of this paper is to study the dynamic response characteristics and regularity of the man-rifle system in the whole shooting process. The three-dimensional motion capture system, surface electromyography test system and plantar pressure test system were used to obtain some data, including the motion of the rifle, the response of the upper limb muscles and joint angles, man-rifle system pressure center and three-round burst dispersion. The results show that, the decrease of the right elbow angle can lead to the fatigue of the medial deltoid muscle, resulting in the decrease of first shot accuracy in the aiming stage. Also the decrease of the angle between the right arm and the trunk can get it hard for the biceps muscle of right arm to exert, making the triceps brachii muscle compensate weak for the instability during the shooting process. These are the reasons that the shooting dispersion becomes worse when the buttstock is too short. The analysis results indicate that the iEMG value of right arm's triceps brachii muscle is the best characteristic to reflect the shooting dispersion when the buttstock length changes.

Torsional Vibration Characteristics of Shafting Based on MRD

LI Yun-qiang, CHEN Cui-cui, CHEN Xiang-chun, WU Bin, ZHANG Jun-hong

2020, 40(11): 1174-1181. doi:10.15918/j.tbit1001-0645.2019.240

Abstract(916) PDF(432)

Abstract:
Due to the narrow tuning range and match difficulty of the traditional passive silicone oil damper, a magneto-rheological damping (MRD) was proposed and designed for the semi-active control of sh afting torsion vibration based on the rheological effect of magneto-rheological fluid (MRF). According to the designed MRD structure, a mechanical model was derived and the magnetic field simulation was carried out. After that, introducing the proposed MRD into a crankshaft system, and a coupling model of the MRD-crankshaft system was established. Finally, numerical simulation was carried out based on Newmark method to obtain the torsion vibration response of the crankshaft system. And the influence of the current applying on the MRD on the torsion vibration characteristics was analyzed. The results show that the magnetic flux leakage and magnetic pressure drop outside the plate of MRF are small, and the designed magneti c circuit is effective. Though the traditional silicone oil damper has a better effect on suppressing the 6 harmonic amplitude of the crankshaft, but the effect on suppressing the 4.5 harmonic torsion vibration is not ideal, and the torsion amplitude is increased. Compared with the traditional silicone oil damper, the MRD can make crankshaft system possess obvious characteristics of variable stiffness and variable damping. Supplying a suitable current, the torsion amplitude of the crankshaft system can be minimized over the entire operating speed range.

Dynamic Response Characteristics of Hydraulic Rotary System for Azimuth Thruster of Dynamic Positioning Ship

GAO Song, GUO Yan, LI Xin-fei, YUAN Li-hao

2020, 40(11): 1182-1189. doi:10.15918/j.tbit1001-0645.2019.278

Abstract(978) PDF(462)

Abstract:
In order to study dynamic response characteristics of hydraulic rotary system for azimuth vector thrusters,the composition and working principle of an azimuth thruster were analyzed,studying the pumping-controlled hydraulic motor drive gear reduction mechanism. A mathematical model was established for the rotary dynamics system of vector thrusters. An improved control method was proposed for the vector thrusters to achieve a desired azimuth angle tracking. An asynchronous control frequency simulation system was established for the vector thrusters to analyze the azimuth angle,angular velocity and the dynamic response characteristics of hydraulic rotary system under different azimuth angle. Based on the simulation analysis,the physical constraints of the rotary response were established for the vector thrusters. Simulation results show that,the proposed dynamic model can realistically simulate the dynamic characteristics of azimuth dynamics,and can achieve fast and accurate control of the azimuth angle. Compared with the actual propeller response parameters,the efficiency of the rotary control of an azimuth thruster is improved,and the research on thrust allocation method of dynamic positioning ships and the control of azimuth thrusters has important theoretical significance and engineering value.

Structural Design and Experimental Research of Airborne Equipment Framework

GUO Lei, LIU Jian-hua, XING Li-hua, YUAN Qian, XIA Huan-xiong

2020, 40(11): 1190-1194. doi:10.15918/j.tbit1001-0645.2019.208

Abstract(787) PDF(330)

Abstract:
In order to improve the accuracy of simulation model of complex framework-type equipment support and meet the requirements of high strength and light weight, a static loading test was performed to discover the weak links on the basis of finite element analysis. Then, a structural mechanics model was established to obtain the failure mechanism and an improvement scheme was proposed. Finally, the failure mechanism was obtained to improve the local design. The static loading test results show that the improved equipment support has no obvious plastic deformation and the local design improvement is effective, meeting the requirements of aviation limit overload. Therefore, the design method, combining simulation, experiment and theoretical model, can improve the product strength with little material increment, which can provide an effective way to improve the design of framework-type equipment supports.

Study on Fixation Effect of Human Eye to Calibration Interface

BAI Ke-meng, WANG Jian-zhong, WANG Hong-feng, ZHANG Sheng

2020, 40(11): 1195-1202. doi:10.15918/j.tbit1001-0645.2019.233

Abstract(855) PDF(460)

Abstract:
To aim precisely at the target through eye tracking will become an important control method for unmanned weapons. Calibration is an important part of eye tracking, and different calibration interfaces will produce different fixation effects due to human eye observation and physiological characteristics. By changing the background of the calibration interface and such elements of the fixed point as color, shape, size, and so on, the least-squares regression method was used to establish the line of sight to estimate mapping model calibration, 5×5 evenly distributed 25 points were tested, the fixation accuracy and precision of 27 groups of calibration interfaces were compared and analyzed, and the best calibration interface was selected, to research the human eye fixation effect of calibration interface. The experimental results showed that the fixation accuracy of interface #1 was the best (0.69°±0.43°), and the fixation precision of interface #24 was the best (0.270°±0.083°). According to the criterion of fixation accuracy and precision, calibration interface No. 1 was the best calibration interface.

Design and Realization of OOK-Based Unified Laser TT&C System

ZHU Hong-quan, XING Qiang-lin, FU Yi-wen, HAN Hang-cheng

2020, 40(11): 1203-1206. doi:10.15918/j.tbit1001-0645.2018.235

Abstract(975) PDF(404)

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Unified laser TT&C system can achieve duplex high speed communication, high precision range measurement and clock synchronization between two terminals simultaneously. To achieve the unified laser TT&C system, a prototype of laser communication system was developed based on on-off keying (OOK) and realized to simulate the space terminals. It was arranged with two set simulation terminals, used to send laser modulated signal separately, record the transmitting and arriving time of data frames, and based on the data to calculate the range, time transfer error and frequency transfer error of the measurement results. The terminals were linked via single-mode fibers with length of about 22 km. Along with the duplex laser communication demonstration with data rate of 2.5 Gbit/s, the high measurement precision can achieve 6.2 mm for ranging random error, 1.3 mm for ranging systematic error, 27 ps for time transfer error, 2.7×10^-13for frequency transfer error. The prototype provides a technical base for the development and upgrade of the unified laser TT&C equipment in the future.

An Unambiguous Tracking Method Based on Combination of Sub Cross-Correlation Functions for BOC Signals

FU Qiang, CHEN Xiao-qian, JI Yuan-fa, SUN Xi-yan, WEI Bao-guo

2020, 40(11): 1207-1215. doi:10.15918/j.tbit1001-0645.2018.197

Abstract(945) PDF(376)

Abstract:
Since the auto-correlation function of binary offset carrier (BOC) signal has multiple peaks, there is a false tracking problem in BOC signal. In order to solve this problem, a concept of sub cross-correlation function and an unambiguous tracking method based on combination of sub cross-correlation functions were proposed in this paper. By analyzing and comparing the sub-correlation functions, a correlation function with only a single correlation peak and the narrow correlation characteristics of BOC were created. Taking BOC (1, 1) and BOC (10, 5) as examples, simulation analysis was carried out. The results show the effectiveness of de-ambiguity. Compared with ASPeCT and BPSK-like, the proposed method can remove side peaks and maintain narrow correlation. The phase discrimination curve shows that, compared with BPSK-like for BOC (1, 1) and BOC (10, 5), the linear region slope gain of the proposed method is 5.2 dB and 7.2 dB, respectively. In the anti-multipath performance, compared to ASPeCT and BPSK-like, the multipath error of this method is least. In the anti-noise performance, compared with BPSK-like for BOC (1, 1) and BOC (10, 5) respectively, the code tracking error standard deviation of the method is reduced by 0.046Tc and 0.030Tc.

Joint DOA and Polarization Parameter Estimation of COLD Sensors Based on Resampling Technique

MA Hui-hui, TAO Hai-hong

2020, 40(11): 1216-1222. doi:10.15918/j.tbit1001-0645.2018.113

Abstract(824) PDF(397)

Abstract:
Focusing on the performance degradation of parameter estimation at low signal-to-noise ratio (SNR), a new method of direction of arrival (DOA) and polarization parameters estimation was proposed for COLD arrays in this paper. Combining the ROOT-MUSIC algorithm with a modified resampling technique, the proposed method was designed to reduce the computational complexity and improve estimation accuracy. Besides, the parameter feasibility determination method was used to preserve the correct values while removing the outliers after resampling. Results show that, the proposed algorithm can improve the accuracy of DOA and polarization parameter estimation, especially in the case of low signal-to-noise ratios. Computer simulations verify the effectiveness and demonstrate high-accuracy of the proposed DOA estimation algorithm, especially in the case of low SNR.

A Mask RCNN Based Algorithm for the Ships' Number and the Shape Detection

NIE Zhen-gang, REN Jing, LU Ji-hua

2020, 40(11): 1223-1229. doi:10.15918/j.tbit1001-0645.2019.213

Abstract(1210) PDF(401)

Abstract:
A ship detection algorithm based on Mask region-convolutional neural network (Mask RCNN) was proposed to detect both the position and the ship flow in the satellite image. The proposed algorithm was designed to automatically detect and locate the vessel positions in the observed sea area. Based on the data set generated, the Mask RCNN model was built and trained. According to the position and accuracy of the outputs, the model parameters were modified to further improve the detection accuracy. Then, the trained model was applied to testing the image of the data set, quantitatively evaluating the model. The testing results show that, when the intersection over union (IOU) is 0.5, the accuracy of boundary frame position can reach 85.4% and the accuracy of ship number detection can reach up to 89.9%. The simulation results reveal that Mask RCNN can be used to detect the ship flow precisely.

Out-of-Band Multi-Frequency Interference Prediction Method and Verification for Communication Station

WANG Ya-ping, WEI Guang-hui, SHANG Zai-fei, PAN Xiao-dong, WAN Hao-jiang

2020, 40(11): 1230-1237. doi:10.15918/j.tbit1001-0645.2018.125

Abstract(828) PDF(386)

Abstract:
Communication station will restart when they are irradiated by out-of-band interference strongly. When they are exposed to a complex external electromagnetic environment, communication station may still be disturbed and restarted within the safety area divided by the existing electromagnetic sensitivity test method. Considering the interconnect cable outside the station as the main coupling channel of interference, two assumptions about the sensitive type of the restart effect were made for the communication station, relating to the effective value of the interference signal, relating to the peak-to-peak value of the interference signal. In order to determine the sensitive type of the equipment under test, a sine wave and an amplitude modulation wave with 100% modulation deep were taken as interference sources. Test results show that, when the critical interference state is reached, if it is related to the effective value, the ratio of the amplitude between the two interference signals is about 0.61; if it is related to the peak-to-peak value, the ratio between them is 1. Considering multiple interference sources existing at the same time, corresponding prediction models were established to be selected to calculate the prediction coefficient, named asS. It was arranged that, whenS≥ 1, the communication station would restart, and vice versa. Finally, taking a certain type communication station with interconnect cable as test object, the feasibility of the above method was verified through experiment.

Periodically Nonuniform Averaging and Reconstruction of Signals in Function Spaces Associated with the Linear Canonical Transform

WANG Wei-jiang, CAI Xue-ying, WANG Jia-tong

2020, 40(11): 1238-1244. doi:10.15918/j.tbit1001-0645.2019.055

Abstract(806) PDF(371)

Abstract:
Several sampling theorems, which aid in the reconstruction of periodically nonuniform sampled signals in the linear canonical transform (LCT) domain, have high sidelobe and slow-decayed synthesizing functions. Focusing on this issue, the reconstruction theorem of a nonstationary signal was investigated in function spaces associated with the LCT. Periodically nonuniform averaging model and reconstruction algorithm were proposed based on the theories of multi-rate signal processing and multi-channel perfect reconstruction filter banks. Introducing window functions with high degree of freedom, the method was arranged to establish the reconstruction functions with compactly supported synthesizing capability, and to make the number of integral channel unconstrained from the range of function space, being suitable for those applications with limited sampling spots and hardware. Simulation results show that, compared with other conventional methods, the proposed method possesses the advantages with less interpolation error and fewer consumptions of hardware resources.

Online Protest Prediction with Time-Series Text and High-Order Interactive Topology

LUO Sen-lin, LI Dong-chao, WU Zhou-ting, PAN Li-min, WU Qian

2020, 40(11): 1245-1252. doi:10.15918/j.tbit1001-0645.2019.079

Abstract(915) PDF(393)

Abstract:
Aiming at the problem of neglecting user text timing differences and high-level interactive topologies among users in online protest prediction, combining temporal text and high-order interactive topology, an online protest prediction method was proposed. Modeling the influence of the text information published by users at different moments on their current protest tendency based on a self-attention mechanism, the user text representation vector was constructed. At the same time, the similarity of the neighbor nodes was used to construct the user interaction topology representation vector, maintaining the second-order similarity. Synthesizing the user text representation vector and the interactive representation vector, the user protest tendency was predicted. The results of the Twitter dataset show that the accuracy of the method can reach 93.9%, providing technical support for protest prediction.

An Improved Model for GaN HEMTs with Kink Effect

HOU Yan-fei, LIU Yi-jing, LI Hao, HE Wei, LÜ Yuan-jie, LIU Jun, YANG Song-yuan, WANG Bo-wu, YU Wei-hua

2020, 40(11): 1253-1258. doi:10.15918/j.tbit1001-0645.2019.119

Abstract(1031) PDF(385)

Abstract:
An improved model for AlGaN/GaN HEMTs including Kink effect was presented in this paper. This large signal model was constructed based on the symbolically defined device (SDD) form of advanced design system (ADS). The improvedI-Vexpression was proposed to complete nonlinear fitting accurately by contrasting the measure results of the on-wafer AlGaN/GaN HEMT with two gate fingers each being 90 nm long and 40 μm wide. The model can accurately fit the 0~110 GHzS-parameter and DC characteristics of the device. The convergence of the model is great during the harmonic balance simulation. So this modeling method can be applied to millimeter-wave GaN HEMTs.

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