Welcome to Journal of Beijing Institute of Technology

2016 Vol. 25, No. 4

Mechanical Engineering
Longitudinal speed control algorithm to improve the vehicle stability and mobility on a sharp curve
REN Hong-bin, CHEN Si-zhong, ZHAO Yu-zhuang
2016, 25(4): 441-447. doi:10.15918/j.jbit1004-0579.201625.0401
Abstract:
A new longitudinal speed control strategy is proposed. It used the lateral jerk information as the feedback to predict the longitudinal acceleration and deceleration, which is especially beneficial to a sharp curve turning at a high driving speed. The performance of the controller is validated with Matlab/Simulink. The simulation results indicate that compared with the traditional vehicle, the G-vector controller can reduce the turning radius and improve the vehicle stability and agility obviously. And the proposed longitudinal speed control strategy could trade-off the longitudinal and lateral acceleration by using the tire force during the turning.
Obstacle avoidance technology of bionic quadruped robot based on multi-sensor information fusion
HAN Bao-ling, ZHANG Tian, LUO Qing-sheng, ZHU Ying, SONG Ming-hui
2016, 25(4): 448-454. doi:10.15918/j.jbit1004-0579.201625.0402
Abstract:
In order to improve the ability of a bionic quadruped robot to percept the location of obstacles in a complex and dynamic environment, the information fusion between an ultrasonic sensor and a binocular sensor was studied under the condition that the robot moves in the Walk gait on a structured road. Firstly, the distance information of obstacles from these two sensors was separately processed by the Kalman filter algorithm, which largely reduced the noise interference. After that, we obtained two groups of estimated distance values from the robot to the obstacle and a variance of the estimation value. Additionally, a fusion of the estimation values and the variances was achieved based on the STF fusion algorithm. Finally, a simulation was performed to show that the curve of a real value was tracked well by that of the estimation value, which attributes to the effectiveness of the Kalman filter algorithm. In contrast to statistics before fusion, the fusion variance of the estimation value was sharply decreased. The precision of the position information is 4.6.cm, which meets the application requirements of the robot.
Continuous and smooth gait transition in a quadruped robot based on CPG
NA Qi, HAN Bao-ling, LI Hua-shi, LUO Qing-sheng, JIA Yan
2016, 25(4): 455-462. doi:10.15918/j.jbit1004-0579.201625.0403
Abstract:
To improve the smoothness of motion control in a quadruped robot, a continuous and smooth gait transition method based on central pattern generator (CPG) was presented to solve the unsmooth or failed problem which may result in phase-locked or sharp point with direct replacement of the gait matrix. Through improving conventional weight matrix, a CPG network and a MATLAB/Simulink model were constructed based on the Hopf oscillator for gait generation and transition in the quadruped robot. A co-simulation was performed using ADAMS/MATLAB for the gait transition between walk and trot to verify the correctness and effectiveness of the proposed CPG gait generation and transition algorithms. Related methods and conclusions can technically support the motion control technology of the quadruped robot.
Informatics and Electronic Engineering
Stable walking of quadruped robot on unknown rough terrain
HE Yu-dong, WANG Jun-zheng, KE Xian-feng, WANG Shou-kun
2016, 25(4): 463-472. doi:10.15918/j.jbit1004-0579.201625.0404
Abstract:
Quadruped robot is considered to be the most practical locomotion machine to negotiate uneven terrain, and shows superb stability during static walking. To improve the ability to go over rough terrain, this paper is focused on the stable walking and balance control of quadruped robots. 24 kinds of walking gaits are analyzed in order to derive the most stable and smoothest walking gait. Considering the inefficiency to model a terrain by its specified appearance, a uniform terrain model is established and by means of kinematic analysis, a method to adjust the body posture and center of gravity (COG) height is presented. Simulations demonstrate the effectiveness of the proposed method and the improvement of the adaptation of quadruped robots on rough terrain.
Localization and mapping in urban area based on 3D point cloud of autonomous vehicles
WANG Mei-ling, LI Yu, YANG Yi, ZHU Hao, LIU Tong
2016, 25(4): 473-482. doi:10.15918/j.jbit1004-0579.201625.0405
Abstract:
In order to meet the application requirements of autonomous vehicles, this paper proposes a simultaneous localization and mapping (SLAM) algorithm, which uses a VoxelGrid filter to down sample the point cloud data, with the combination of iterative closest points (ICP) algorithm and Gaussian model for particles updating, the matching between the local map and the global map to quantify particles' importance weight. The crude estimation by using ICP algorithm can find the high probability area of autonomous vehicles' poses, which would decrease particle numbers, increase algorithm speed and restrain particles' impoverishment. The calculation of particles' importance weight based on matching of attribute between grid maps is simple and practicable. Experiments carried out with the autonomous vehicle platform validate the effectiveness of our approaches.
Effective approach for outdoor obstacle detection by clustering LIDAR data context
WANG Jun-zheng, QIAO Jia-nan, LI Jing
2016, 25(4): 483-490. doi:10.15918/j.jbit1004-0579.201625.0406
Abstract:
A method of environment mapping using laser-based light detection and ranging (LIDAR) is proposed in this paper. This method not only has a good detection performance in a wide range of detection angles, but also facilitates the detection of dynamic and hollowed-out obstacles. Essentially using this method, an improved clustering algorithm based on fast search and discovery of density peaks (CBFD) is presented to extract various obstacles in the environment map. By comparing with other cluster algorithms, CBFD can obtain a favorable number of clusterings automatically. Furthermore, the experiments show that CBFD is better and more robust in functionality and performance than the K-means and iterative self-organizing data analysis techniques algorithm (ISODATA).
Hand gesture tracking algorithm based on visual attention
FENG Zhi-quan, XU Tao, LÜ Na, TANG Hao-kui, JIANG Yan, LIANG Li-wei
2016, 25(4): 491-501. doi:10.15918/j.jbit1004-0579.201625.0407
Abstract:
In the majority of the interaction process, the operator often focuses on the tracked 3D hand gesture model at the "interaction points" in the collision detectionscene, such as "grasp" and "release" and objects in the scene, without paying attention to the tracked 3D hand gesture model in the total procedure. Thus in this paper, a visual attention distribution model of operator in the "grasp", "translation", "release" and other basic operation procedures is first studied and a 3D hand gesture tracking algorithm based on this distribution model is proposed. Utilizing the algorithm, in the period with a low degree of visual attention, a pre-stored 3D hand gesture animation can be used to directly visualise a 3D hand gesture model in the interactive scene; in the time period with a high degree of visual attention, an existing "frame-by-frame tracking" approach can be adopted to obtain a 3D gesture model. The results demonstrate that the proposed method can achieve real-time tracking of 3D hand gestures with an effective improvement on the efficiency, fluency, and availability of 3D hand gesture interaction.
Design and implementation of path planning algorithm for vehicle parking
YANG Yi, QU Xin, ZHU Hao, ZHANG Lu, LI Xing-he
2016, 25(4): 502-511. doi:10.15918/j.jbit1004-0579.201625.0408
Abstract:
Parking is an important and indispensable skill for drivers. With rapid urban development, the automatic parking assistant system is one of the key components in future automobiles. Path planning is always essential for solving parking problems. In this paper, a path planning method is proposed for parking using straight lines and circular curves of different radius without collisions with obstacles. The parking process is divided into two steps in which the vehicle reaches the goal state through the intermediate state from the initial state. The intermediate state will be selected from the intermediate state set with a certain criterion in order to avoid obstacles. Similarly, an appropriate goal state will be selected based on the size of the parking lot. In addition, an automatic parking system is built, which effectively achieves the parking lot perception, path planning and performs parking processes in the environment with obstacles. The result of simulations and experiments demonstrates the feasibility and practicality of the proposed method and the automatic parking system.
Adaptive micro-extended-analog-computer array with a linear Lukasiewicz function
ZHU Yi-lin, PAN Feng, REN Xue-mei, GAO Qi, CHANG Yan-chun
2016, 25(4): 512-520. doi:10.15918/j.jbit1004-0579.201625.0409
Abstract:
A micro-extended-analog-computer (uEAC) is developed on the basis of Rubel's extended analog computer(EAC) model. Through the uEAC mathematical model, the resistance properties of the conductive sheet, several feedback uEAC models,and a more flexible uEAC cell structure with a multi-level hierarchy are discussed. Futhermore,for the dynamic uEAC array with a linear Lukasiewicz function, a nonlinear differential equation description is presented, and then a sufficient global asymptotic stability condition is derived by utilizing a Lyapunov function and a Lipchitz function. Finally, comparative simulations for a cam servo mechanism system are conducted to verify the capability of the uEAC array as an adaptive controller.
Filtering algorithm of line structured light for long-distance obstacle detection
SHAO Hai-yan, ZHANG Zhen-hai, LI Ke-jie
2016, 25(4): 521-525. doi:10.15918/j.jbit1004-0579.201625.0410
Abstract:
Since unmanned ground vehicles often encounter concave and convex obstacles in wild ground, a filtering algorithm using line structured light to detect these long distance obstacles is proposed. For the line structured light image, a ranked-order based adaptively extremum median (RAEM) filter algorithm on salt and pepper noise is presented. In the algorithm, firstly effective points and noise points in a filtering window are differentiated; then the gray values of noise points are replaced by the medium of gray values of the effective pixels, with the efficient points' gray values unchanged; in the end this algorithm is proved to be efficient by experiments. Experimental results demonstrate that the proposed algorithm can remove noise points effectively and minimize the image blur, resulting into protecting the edge information as much as possible.
Adaptive leader follower control for multiple quadrotors via multiple surfaces control
ABBAS Rabah, WU Qing-he
2016, 25(4): 526-532. doi:10.15918/j.jbit1004-0579.201625.0411
Abstract:
Based on the multiple surface and fixed undirected communication topology, the adaptive leader follower control for multiple quadrotors is discussed. Our approach is based on leader follower architecture. Multiple surface control (MSC) is used to design consensus controller to make multiple quadrotors construct a formation during flying with the presence of uncertainty item caused by the ground effect during landing or taking off. Simulation results are presented to validate the effectiveness of the proposed controller.
Spatially dispersive model of wire medium for scattering
KONG Bei-bei, SONG Wei, SHENG Xin-qing
2016, 25(4): 533-539. doi:10.15918/j.jbit1004-0579.201625.0412
Abstract:
The electromagnetic properties of wire medium are studied by analyzing its transmission coefficient, and a homogeneous uniaxial effective permittivity tensor with one spatially dispersive component is obtained. In order to evaluate the validity of the equivalent model for scattering problems, the bistatic and monostatic radar cross sections (RCS) of a block of wire medium are investigated with the finite-difference time-domain (FDTD) method. The difference of RCS from the physical wire medium and the corresponding equivalent model has been compared and analyzed under various parameters of wire medium, which clearly demonstrates the accuracy of the equivalent model of wire medium.
Sparse channel estimation for MIMO-OFDM systems using distributed compressed sensing
LIU Yi, MEI Wen-bo, DU Hui-qian, WANG Hong-yu
2016, 25(4): 540-546. doi:10.15918/j.jbit1004-0579.201625.0413
Abstract:
A sparse channel estimation method is proposed for doubly selective channels in multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Based on the basis expansion model (BEM) of the channel, the joint-sparsity of MIMO-OFDM channels is described. The sparse characteristics enable us to cast the channel estimation as a distributed compressed sensing (DCS) problem. Then, a low complexity DCS-based estimation scheme is designed. Compared with the conventional compressed channel estimators based on the compressed sensing (CS) theory, the DCS-based method has an improved efficiency because it reconstructs the MIMO channels jointly rather than addresses them separately. Furthermore, the group-sparse structure of each single channel is also depicted. To effectively use this additional structure of the sparsity pattern, the DCS algorithm is modified. The modified algorithm can further enhance the estimation performance. Simulation results demonstrate the superiority of our method over fast fading channels in MIMO-OFDM systems.
Quality of experience based scheduling algorithm in LTE network with various traffics
WU Zhi-kun, FEI Ze-song, WANG Fei, GONG Shi-qi, LI Na
2016, 25(4): 547-552. doi:10.15918/j.jbit1004-0579.201625.0414
Abstract:
Quality of experience (QoE) based scheduling algorithm of long term evalution (LTE) network with various traffics is studied. Utility functions are adopted to estimate mean opinion score (MOS) for different traffics and a new MOS metric called normalized MOS is defined. A scheduling algorithm based on normalized MOS and greedy algorithm is proposed, aiming at maximizing the entirety MOS level of the whole users in the cell. We compare the performance of the proposed algorithm with other typical scheduling algorithms and the simulation results show that the algorithm proposed outperform other ones in term of QoE and fairness.
Evaluate mobile video quality with LTE radio access network parameters
WANG Fei, CHEN Liang, DENG Xiao-lin, FEI Ze-song, HAN Guang-lin, WAN Lei
2016, 25(4): 553-561. doi:10.15918/j.jbit1004-0579.201625.0415
Abstract:
To evaluate the video quality, we tested sample videos delivered using HTTP adaptive streaming (HAS) in LTE network. In order to establish a correlation between radio access network (RAN) performance and quality of experience (QoE), we set up a testbed under different radio impairment conditions with three parameters: signal to interference and noise ratio (SINR), an amount of available network resource and a round trip latency. End users graded each video in a mobile equipment with their QoE Mearnwhile, we used a nonlinear model to simulate the comprehensive predicted mean opinion score (pMOS). Our results show that the nonlinear model can predict the enduser's feedback. The pearson correlation coefficient (PCC) of the model is larger than 0.9. This demonstrate that the output of the model has a high correlation with the end users' ratings and can reflect the QoE accurately. The method we developed will help mobile network operators evaluate the RAN performance of its QoE. It can also be used for HAS service to optimize LTE network and improve its QoE.
Modified SIFT descriptor and key-point matching for fast and robust image mosaic
HE Yu-qing, WANG Xue, WANG Si-yuan, LIU Ming-qi, ZHU Jia-dan, JIN Wei-qi
2016, 25(4): 562-570. doi:10.15918/j.jbit1004-0579.201625.0416
Abstract:
To improve the performance of the scale invariant feature transform (SIFT), a modified SIFT (M-SIFT) descriptor is proposed to realize fast and robust key-point extraction and matching. In descriptor generation, 3 rotation-invariant concentric-ring grids around the key-point location are used instead of 16 square grids used in the original SIFT. Then, 10 orientations are accumulated for each grid, which results in a 30-dimension descriptor. In descriptor matching, rough rejection mismatches is proposed based on the difference of grey information between matching points. The performance of the proposed method is tested for image mosaic on simulated and real-world images. Experimental results show that the M-SIFT descriptor inherits the SIFT's ability of being invariant to image scale and rotation, illumination change and affine distortion. Besides the time cost of feature extraction is reduced by 50% compared with the original SIFT. And the rough rejection mismatches can reject at least 70% of mismatches. The results also demonstrate that the performance of the proposed M-SIFT method is superior to other improved SIFT methods in speed and robustness.
New LED light source system with uniform illumination for line-scan CCD imaging systems
ZHANG Lian-lian, HUANG Qing-mei, LI Xin-yi, HU Wei-gui, LIU Nan-bo, LU Ai-min
2016, 25(4): 571-574. doi:10.15918/j.jbit1004-0579.201625.0417
Abstract:
A system with uniform light reflection in the inner surface within a horizontal 2/3 cylindrical structure for line-scan CCD of the print testing was designed. The design was based on diffuse reflection uniformity of the integrating sphere and requirement of the strip uniform illumination region. This system was called dome light. White light LED array light sources were used for uniform illumination. The LEDs were filtrated to composite array light source based on coefficient of variation of a single LED. The standard white board and SG color checkers were used in the line-scan CCD imaging experiments under the dome light and ordinary illumination light source. The average color difference (ΔE) of SG color checkers in CIELAB space was 2.091 under the dome light and 2.286 under ordinary illumination light source respectively. Experimental results indicate that the dome light can satisfy illumination uniformity and color rendering consistency for line-scan CCD and provide a standard light source for uniform calibration of different cameras.
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