JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Inverse Kinematics Analysis of a 7-DOF Space Manipulator for Trajectory Design

2017, 26(3): 285-291. doi:10.15918/j.jbit1004-0579.201726.0301

[Abstract](1418) [PDF 1415KB](1156)

Abstract:
To solve the inverse kinematics problem for redundant degrees of freedom (DOFs) manipulators has been and still continues to be quite challenging in the field of robotics. Aiming at trajectory planning for a 7-DOF space manipulator system, joint rotation trajectories are obtained from predetermined motion trajectories and poses of the end effector in Cartesian space based on the proposed generalized inverse kinematics method. A minimum norm method is employed to choose the best trajectory among available trajectories. Numerical simulations with the 7-DOF manipulator show that the proposed method can achieve the planned trajectory and pose under the circumstances of minimum angular velocities. Moreover, trajectory results from the proposed kinematics model and inverse kinematics method has the advantages of simple modelling, low computation cost, easy to solve and plan trajectory conveniently. The smooth and continuous joint rotation functions obtained from the proposed method are suitable for practical engineering applications.

Experiment Study on Shock Induced Reaction Process of Ti+Si Reactive Powder

Naifu Cui, Pengwan Chen, Qiang Zhou, Bingbing Zhou

2017, 26(3): 292-296. doi:10.15918/j.jbit1004-0579.201726.0302

[Abstract](730) [PDF 1729KB](727)

Abstract:
A phenomenon of shock wave reacceleration was studied when Ti+Si reactive powder is loaded by a high-speed flyer. The self-propagating reaction in the Ti+Si reactive powder was triggered by the high speed impaction of the flyer launched by a two-stage gas gun. In the process of self-propagating reaction, a strand of optical fiber and the electric pins were used to measure the velocity of shock wave propagation. The experimental results showed that the initial velocity of shock wave in the reactive powder was a few hundred meters per second, and then it decreased obviously with the increase of propagation distance. This phenomenon was also verified in the process of a pure Si powder loaded by a shock, while the phenomenon of shock wave reacceleration was not observed in the Ti+Si reactive powder.

Modeling and Analysis of a Random Excited Double-Clamped Piezoelectric Energy Harvester

Xiaoya Zhou, Shiqiao Gao, Haipeng Liu

2017, 26(3): 297-303. doi:10.15918/j.jbit1004-0579.201726.0303

[Abstract](791) [PDF 796KB](701)

Abstract:
A double-clamped piezoelectric energy harvester subjected to random excitation is presented, for which corresponding analytical model is established to predict its output characteristics. With the presented theoretical natural frequency and equivalent stiffness of vibrator, the closed-form expressions of mean power and voltage acquired from the double-clamped piezoelectric energy harvester under random excitation are derived. Finally theoretical analysis is conducted for the output performance of the double-clamped energy harvester with the change of spectrum density (SD) of acceleration, load resistance, piezoelectric coefficient and natural frequency value, which is found to closely agree with Monte Carlo simulation and experimental results.

Optimization of Out-of-Plane Vibration Energy Harvesters Employing Electret

Chunhui Gao, Shiqiao Gao, Haipeng Liu, Lei Jin, Junhu Lu

2017, 26(3): 304-310. doi:10.15918/j.jbit1004-0579.201726.0304

[Abstract](663) [PDF 1335KB](575)

Abstract:
This paper investigated the dependence of out-of-plane electret-based vibration energy harvesters' output power, frequency bandwidth, and resonance frequency on surface charge density and load resistance. As the external acceleration amplitude and electret size were held constant, the following results are predicted by the numerical investigation:① An optimum value exists in the surface charge density to maximize the output power. As the surface charge density is increasing,electrostatic forces are enhanced, which emphasizes that the soft spring effect widens the frequency bandwidth and lowers the resonance frequency. ② Different surface charge densities correspond to different optimum initial air gaps, resonance frequency, and optimum load resistance. ③ With the attenuation of the surface potential, the output power, frequency drift, and frequency bandwidth decreased. ④ An optimum value exists in the load resistance to maximize the output power. As the load resistance is decreasing, electrostatic force is enhanced, which lowers the resonance frequency. ⑤ A maximum frequency bandwidth exists with further load resistance increasing, and the initial air gap is smaller, the greater the frequency bandwidth.

Thermal Behavior, Sensitivity, Detonation Velocity and Pressure of a Nitrogen-Rich Compound

Zhiyue Han, Yupeng Zhang, Zhiming Du, Zengyi Li, Yuezhen Yang

2017, 26(3): 311-317. doi:10.15918/j.jbit1004-0579.201726.0305

[Abstract](741) [PDF 399KB](796)

Abstract:
The nitrogen content of tetrazolo triazines is 68.9%. In this paper, tetrazolotriazines was synthetized. The TG-DSC test indicated its decomposition process in detail. The non-isothermal kinetic parameters were speculated by Kissinger and Ozawa methods. It revealed the mechanism function of thermal decomposition. The impact and friction sensitivity were tested. The detonation pressure and velocity were calculated. It has a wide range of potential applications as a kind of energetic material.

Sealing of Ejection Hole at the Bottom of Projectile for Wired Transmission System of Penetration Data

Huiming Ma, Ya Zhang

2017, 26(3): 318-323. doi:10.15918/j.jbit1004-0579.201726.0306

[Abstract](721) [PDF 1954KB](501)

Abstract:
It is difficult to find the projectile when people want to get the penetration data in a hard recovery method, so a recovery system of penetration data is designed based on an ejection mode from the projectile base and a method of wired transmission, at the same time, the system was sealed with a designed sealing device, the working principle of which was introduced. Using Fluent as the simulation platform, the transient pressure of seal cavity was simulated based on the change of chamber pressure, and steady-state pressure of seal clearance and seal cavity were simulated based on the maximum chamber pressure. The sealing performance was tested by a pressure test system. The results of simulation and experiment show that the maximum pressure of seal cavity is 139.4.kPa when the maximum chamber pressure is 242.9.MPa and the maximum temperature of gunpowder explosive gas is 2.166.5.K, so the sealing performance can be assured. The sealing device can be taken as a reference in sealing research on gunpowder gas at the bottom of projection.

Vibration Effect and Damage Evolution Characteristics of Tunnel Surrounding Rock Under Cyclic Blasting Loading

Guosheng Zhong, Yongzhong Lou, Yuhua Fu

2017, 26(3): 324-333. doi:10.15918/j.jbit1004-0579.201726.0307

[Abstract](834) [PDF 2493KB](685)

Abstract:
Model test studies based on the similarity theory were conducted to investigate vibration effect and damage evolution characteristics of tunnel surrounding rock under push-type cyclic blasting excavation. The model was constructed with a ratio of 1:15. By simulating the tunnel excavation of push-type cyclic blasting, the influence of the blasting parameter change on vibration effect was explored. The damage degree of tunnel surrounding rock was evaluated by the change of the acoustic wave velocity at the same measuring point after blasting. The relationship between the damage evolution of surrounding rock and blasting times was established. The research results show that:① In the same geological environment, the number of delay initiation is larger, the main vibration frequency of blasting seismic wave is higher, and the attenuation of high frequency signal in the rock and soil is faster. The influence of number of delay initiation on blasting vibration effect cannot be ignored; ② Under push-type cyclic blasting excavation, there were great differences in the decreasing rates of acoustic wave velocity of the measuring points which have the same distance to the blasting region at the same depth, and the blasting damage ranges of surrounding rock were typically anisotropic at both depth and breadth; ③ When blasting parameters were basically kept as the same, the growth trend of the cumulative acoustic wave velocity decreasing rate at the measuring point was nonlinear under different cycle blasting excavations; ④ There were nonlinear evolution characteristics between the blasting cumulative damage (D) of surrounding rock and blasting times (n) under push-type cyclic blasting loading, and different measuring points had corresponding blasting cumulative damage propagation models, respectively. The closer the measuring point was away from the explosion source, the faster the cumulative damage extension. Blasting cumulative damage effect of surrounding rock had typically nonlinear evolution properties and anisotropic characteristics.

Dynamic Motion Resistance for Tracked Vehicle

Kai Zhao, Mingming Dong, Zhiguo Sang, Feng Liu, Liang Gu

2017, 26(3): 334-339. doi:10.15918/j.jbit1004-0579.201726.0308

[Abstract](845) [PDF 395KB](779)

Abstract:
Based on previous achievements, a dynamic pressure-sinkage equation for saturated clay is established. First, a quasi-static penetration rate is selected, and the ratio of the dynamic penetration rate to the quasi-static rate is used to characterize the degree of dynamic effect, then theβth power of the ratio is used to quantify the dynamic effect of sinkage. The dynamic effect exponentβis obtained using penetration tests with different penetration rates. Then, a dynamic motion resistance equation for a tracked vehicle is established based on the dynamic pressure-sinkage equation. The equation incorporates both penetration and bulldozing resistance.Finally, a series of simulation experiments with varying travel speeds and slip rates is carried out. The results show that an increase in the speed leads to stronger terrain stiffness, resulting in a decrease in sinkage and motion resistance.However, the enhancement effect becomes weaker with an increase in the travel speed.

Modeling and Simulation of Diaphragm Spring Clutch

Hui Jin, Fanjing Meng

2017, 26(3): 340-348. doi:10.15918/j.jbit1004-0579.201726.0309

[Abstract](917) [PDF 629KB](913)

Abstract:
A model was developed to simulate a vehicle diaphragm spring clutch with the evaluation indicators of jerk degree and friction work. First, the pressing load characteristic of the driven plate of the diaphragm spring clutch was analyzed. Then, the clutch dynamic characteristic under each state was studied according to the basic principles of tribology. Finally, the mathematical model of the clutch was developed. Based on the model, the performance of a vehicle was simulated. The simulation results show that the model can predict the dynamic characteristic of the clutch correctly and evaluate the performance of the clutch engagement effectively. The model can be used for theoretical research of automatic clutch control and can be easily applied to simulate vehicle longitudinal dynamics.

Optimization of Waste Gate Drive Circuit of Two-Stage Turbocharging System

Fujun Zhang, Jiahang Chang, Tao Cui, Meng Xia

2017, 26(3): 349-356. doi:10.15918/j.jbit1004-0579.201726.0310

[Abstract](776) [PDF 660KB](574)

Abstract:
A two stage turbocharging control system was proposed, in which the pressure regulator valve with a close-loop pressure adjusting function instead of a high speed on-off solenoid valve, is used as a driving mechanism of waste gate. A digital-analog (DA)conversion circuit based on pulse width modulation (PWM) generates one analog voltage signal required by the pressure regulating valve control. The principle of the DA conversion circuit was analyzed, meanwhile, the performance of the conversion circuit was improved by adopting a speed-up capacitor, which helps to increase the stability and responsiveness of the control voltage generated by the conversion circuit; the structure parameters of the circuit was optimized by simulation. After the optimization, the ripple wave of circuit output voltage was kept within 16.mV under the 12.bit conversion accuracy, the conversion time of the circuit could be reduced to 4.ms. The engine bench test show that the turbocharging boost pressure control system which adopted the circuit had a rather good stable control accuracy(the steady state within 0.8%) and dynamic response(the regulation time is less than 4.s).

Block Compressed Sensing Image Reconstruction Based on SL0 Algorithm

Juan Zhao, Xia Bai

2017, 26(3): 357-366. doi:10.15918/j.jbit1004-0579.201726.0311

[Abstract](927) [PDF 4746KB](1432)

Abstract:
By applying smoothedl₀norm (SL0) algorithm, a block compressive sensing (BCS) algorithm called BCS-SL0 is proposed, which deploys SL0 and smoothing filter for image reconstruction. Furthermore, BCS-ReSL0 algorithm is developed to use regularized SL0 (ReSL0) in a reconstruction process to deal with noisy situations. The study shows that the proposed BCS-SL0 takes less execution time than the classical BCS with smoothed projected Landweber (BCS-SPL) algorithm in low measurement ratio, while achieving comparable reconstruction quality, and improving the blocking artifacts especially. The experiment results also verify that the reconstruction performance of BCS-ReSL0 is better than that of the BCS-SPL in terms of noise tolerance at low measurement ratio.

Effective Sea Clutter Spectrum Extraction Method for HFSWR in Adverse Conditions

Yiming Wang, Xingpeng Mao, Jie Zhang

2017, 26(3): 367-374. doi:10.15918/j.jbit1004-0579.201726.0312

[Abstract](699) [PDF 1496KB](586)

Abstract:
An effective approach in solving the sea clutter spectrum extraction problem is studied in the paper. Different from the conventional signal to noise ratio (SNR) method based on Doppler frequency or range domain information, a method is developed to characterize the differences between the sea echo and those interferences are by signal to interference plus noise ratio (SINR) which jointly utilizing the range, Doppler frequency and azimuth domain information. Furthermore, these differences can be adaptable to adverse conditions by forming the necessary boundaries and constraints in searching of the maximum SINR, which greatly promotes the extraction of sea clutter spectrum. The real high frequency surface wave radar (HFSWR) data demonstrate that the proposed method is less influenced by those interferences and can effectively extract the sea clutter spectrum even under the adverse conditions. Furthermore, it has been shown as an effective method for ship detection and sea state remote sensing of HFSWR.

Pseudo-Random Coding Side-Lobe Suppression Method Based on CLEAN Algorithm

Liyu Tian, Lianjuan Zhang, Jiaying Li

2017, 26(3): 375-380. doi:10.15918/j.jbit1004-0579.201726.0313

[Abstract](798) [PDF 527KB](741)

Abstract:
A pseudo-random coding side-lobe suppression method based on CLEAN algorithm is introduced. The CLEAN algorithm mainly processes pulse compression results of a pseudo-random coding, and estimates a target's distance by a method named interpolation method, so that we can get an ideal pulse compression result of the target, and then use the adjusted ideal pulse compression side-lobe to cut the actual pulse compression result, so as to achieve the remarkable performance of side-lobe suppression for large targets, and let the adjacent small targets appear. The computer simulations by MATLAB with this method analyze the effect of side-lobe suppression in an ideal or noisy environment. It is proved that this method can effectively solve the problem due to the side-lobe of pseudo-random coding being too high, and can enhance the radar's multi-target detection ability.

Optimal Periodic Pulse Jamming Signal Design for QPSK Systems

Jie Yang, Bingyang Han, Jingying Xu

2017, 26(3): 381-387. doi:10.15918/j.jbit1004-0579.201726.0314

[Abstract](914) [PDF 544KB](1021)

Abstract:
The problem of optimal periodic pulse jamming design for a quadrature phase shift keying(QPSK) communication system is investigated. First a closed-form bit-error-rate (BER) of QPSK system under the jamming of pulse signal is derived. Then the asymptotic performance of the derived BER is analyzed as the signal-to-noise ratio (SNR) grows to infinity. In order to maximize the BER of the QPSK system, the optimal parameters of periodic pulse jamming signal, including the duty cycle and signal-to-jamming power ratio (SJR), are found out. Numerical results are presented to verify our analytical results and the optimality of our design.

Anticipating Degradation in State Estimation Accuracy via Online Nonlinear Observability Analysis

Zheng Rong, Shun'an Zhong, Nathan Michael

2017, 26(3): 388-395. doi:10.15918/j.jbit1004-0579.201726.0315

[Abstract](766) [PDF 3560KB](594)

Abstract:
A methodology is proposed to enable real-time evaluation of the observability of local motions, and generate a local observability cost map to enable informed local motion planning in order to avoid potential degradation or degeneracy in state estimator performance. The proposed approach leverages efficient numerical techniques in nonlinear observability analysis and motion primitive-based planning technique to realize the local observability prediction with real-time performance. The degradation of the state estimation performance can be readily predicted with the local observability evaluation result. The proposed approach is specialized to a representative optimization-based monocular visual-inertial state estimation formulation and evaluated through simulation and experiments. The experimental results demonstrated the ability of the proposed methodology to correctly anticipate the potential state estimation degradation.

Blog Opinion Retrieval with Generation Model and Mixture Model

Jie Chen, Zhendong Niu, Xi Li, Lizhe Song

2017, 26(3): 396-403. doi:10.15918/j.jbit1004-0579.201726.0316

[Abstract](724) [PDF 304KB](527)

Abstract:
Blog opinion retrieval aims to find blogs with opinionated information related to a given topic. Its main problem is to compute the opinion score, which balances topic relevance and opinion relevance. To deal with this problem a generative model deduced by a Bayesian approach is pro-posed, and an improved mixture model is proposed to estimate the opinion relevance between a blog and a given topic in our retrieval framework. Moreover, pointwise mutual information is used to expand sentiment words for different topics based on a general sentimental lexicon. The correlation between topic and candidate words is applied in the process of both expanding sentiment words and estimating sentence opinion scores. Experimental results show that the proposed approaches improve upon the state-of-the-art opinion retrieval method on TREC2010 dataset.

Coupled Attribute Similarity Learning on Categorical Data for Multi-Label Classification

Zhenwu Wang, Longbing Cao

2017, 26(3): 404-410. doi:10.15918/j.jbit1004-0579.201726.0317

[Abstract](705) [PDF 260KB](1425)

Abstract:
In this paper a novel coupled attribute similarity learning method is proposed with the basis on the multi-label categorical data (CASonMLCD). The CASonMLCD method not only computes the correlations between different attributes and multi-label sets using information gain, which can be regarded as the important degree of each attribute in the attribute learning method, but also further analyzes the intra-coupled and inter-coupled interactions between an attribute value pair for different attributes and multiple labels. The paper compared the CASonMLCD method with the OF distance and Jaccard similarity, which is based on the MLKNN algorithm according to 5 common evaluation criteria. The experiment results demonstrated that the CASonMLCD method can mine the similarity relationship more accurately and comprehensively, it can obtain better performance than compared methods.

Method Based on Time Randomization to Resist Fault Sensitivity Analysis

Yingjian Yan, Jijun Xu, Shoucheng Wang, Zhong Wang, Min Liu

2017, 26(3): 411-417. doi:10.15918/j.jbit1004-0579.201726.0318

[Abstract](744) [PDF 2256KB](458)

Abstract:
A fault sensitivity analysis (FSA)-resistance model based on time randomization is proposed. The randomization unit is composed of two parts, namely the configurable register array (R-A) and the decoder (chiefly random number generator, RNG). In this way, registers chosen can be either valid or invalid depending on the configuration information generated by the decoder. Thus, the fault sensitivity information can be confusing. Meanwhile, based on this model, a defensive scheme is designed to resist both fault sensitivity analysis (FSA) and differential power analysis (DPA). This scheme is verified with our experiments.

Sliding Mode Control of Fractional-Order Memristive System

Dawei Ding, Shujia Li, Nian Wang

2017, 26(3): 418-426. doi:10.15918/j.jbit1004-0579.201726.0319

[Abstract](838) [PDF 617KB](734)

Abstract:
A sliding mode controller for a fractional-order memristor-based chaotic system is designed to address its problem in stabilization control. Firstly, a physically realizable fractional-order memristive chaotic system was introduced, which can generate a complex dynamic behavior. Secondly, a sliding mode controller based on sliding mode theory along with Lyapunov stability theory was designed to guarantee the occurrence of the sliding motion. Furthermore, in order to demonstrate the feasibility of the controller, a condition was derived with the designed controller's parameters, and the stability analysis of the controlled system was tested. A theoretical analysis shows that, under suitable condition, the fractional-order memristive system with a sliding mode controller comes to a steady state. Finally, numerical simulations are shown to verify the theoretical analysis. It is shown that the proposed sliding mode method exhibits a considerable improvement in its applications in a fractional-order memristive system.

2017 Vol. 26, No. 3