ISSN 0253-2778

CN 34-1054/N

2015 Vol. 45, No. 7

Display Method:
Research Articles
A dynamics control scheme of uncalibrated visual servoing systems
SONG Caiwen, KUANG Sen
2015, 45(7): 537-545. doi: 10.3969/j.issn.0253-2778.2015.07.001
For an uncalibrated visual servoing system with dynamic uncertainties of a robot, a joint torque controller was designed based on robot dynamics by selecting several feature points on the end-effector, which made the selected feature points converge to their desired positions on the image plane. On the basis of a depth-independent image Jacobian matrix and a set of robot dynamics parameters properly selected, linear parametric models of the camera and robot dynamics were established. Then, the online adaptive updating laws the camera parameters and the robot dynamics parameters were designed, and the stability of the closed-loop system was analyzed. Finally, simulation experiments on a three joint manipulator show good performance of the control scheme.
Catenary model and dynamic analysis of a 6-DOF cable-driven parallel robot
YAN Yujiao, SHANG Weiwei
2015, 45(7): 546-564. doi: 10.3969/j.issn.0253-2778.2015.07.002
For the catenary effect on the large-scale of 6-DOF cable-driven parallel robot, the straight-line model and the catenary model of the cables were established, respectively, on the basis of which, the dynamic model of the cable-driven parallel robot was derived and the models were compared at the same time. In order to solve the inverse dynamics of the cable-driven parallel robot, a nonlinear optimization method with constraints was chosen to obtain the cable tension that satisfies the force constraints. Simulation experiment demonstrated that when considering the catenary model, the inverse dynamical solution differs noticeably between the straight line model and the catenary model of the parallel robot. Thus the catenary effect cannot be ignored and the catenary model should be considered in the dynamic analysis.
Regularization and robust stabilization of uncertain descriptor fractionalorder systems
2015, 45(7): 555-560. doi: 10.3969/j.issn.0253-2778.2015.07.003
The robust stability and stabilization of uncertain descriptor fractional-order systems are investigated. In such systems parameter uncertainty is assumed to be time-invariant and norm-bounded in the state matrix. First, a predictive controller was used to regularize the uncertain descriptor fractionalorder systems, and then an output feedback controller was designed to stabilize the regularized system. The sufficient conditions for robustly stabilizing such systems with the fractional order alpha in [1,2) are derived. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed approach.
A robust background modeling algorithm for shadows
FAN Zhihui, LU Zhaoyang, LI Jing, JIANG Wei, YAO Chao
2015, 45(7): 561-567. doi: 10.3969/j.issn.0253-2778.2015.07.005
To remove shadows from foreground objects, an algorithm for background subtraction based on scale-invariant model of local pattern (SILTP) was proposed. The algorithm was designed by fusing three levels of information from the frame, region and pixel levels. The frame level detects sudden, global changes between frames by the global mean gray value. At the region level, the SILTP operator was utilized to get the texture images. Then the texture histograms were used to model background, so as to quickly find contours of moving objects in the frame sequence. The pixel-level obtains object contours accurately using similar-ViBe algorithm. Exhaustive experimental evaluations on complex scenes show efficiency of the proposed method.
An algorithm for correcting susceptibility induced breast temperature imaging during microwave ablation
ZHU Ruimin, DU Hongwei
2015, 45(7): 568-574. doi: 10.3969/j.issn.0253-2778.2015.07.006
During the interventional thermal therapy of beast caner by the hepatic microwave ablation (WMA), magnetic resonance (MR) thermal imaging can obtain accurate temperature together with a reduction in the influence on the accuracy of the temperature caused by the change in the susceptibility of the WMA area. Because susceptibility is very sensitive to temperature change, a new temperature mapping correction method was proposed to reduce the influence of the temperature imaging by susceptibility change. Firstly, the temperature was calculated by the water proton resonance frequency (PRF) method. Secondly, because breast tissue contains lots of fat, the temperature was calculated by means of the water-fat separating method based on differences in the susceptibility changes between water and fat. Lastly, the temperature mapping correction method was evaluated by the temperature difference. The simulation results show that for a tissue model containing both water and fat, when the power of the WMA is 15W, the temperature mapping accuracy can reach 0.34℃ at the 300th second. All the results demonstrated the validity and feasibility of the temperature mapping correction method and its suitability for other tissues containing water and fat.
Vocal tract length aligning based mandarin age voice conversion
LI Jinzhong, LI Xian WANG, Zengfu
2015, 45(7): 575-581. doi: 10.3969/j.issn.0253-2778.2015.07.007
Vocal tract length aligning was proposed for mandarin age voice conversion which transforms age speech into some required target age speech. In the method, the speech spectrum which has been pitch marked was warped in the frequency domain based on the warping factor and warping function while pitch was converted by linear transformation. The experimental results show that the effect of transforming old age speech into a young one is better than otherwise and that the average spectra distance of the former is markedly reduced.Meanwhile, age voice conversion is better for female voice than for male voice in effectiveness and naturalness.
Design of circularly polarized microstrip antenna with bandwidth broadening
ZHOU Dong, SUN Yufa, HU Shaoqi, YANG Ming, LIU Weiwei
2015, 45(7): 582-587.
In order to improve the performance of the bandwidth of the microstrip antenna, a novel method for broadening bandwidth of the circularly polarized microstrip antenna is presented. Coaxial feeding loaded microstrip matching section is used to achieve impedance matching. The impedance and the axialratio bandwidths are improved by placing four sequentially rotated split-ring resonators around the patch of the antenna and embedding a defeated ground structure on the center of the ground plane. Experimental results show that the impedance and the axialratio bandwidths of the antenna are increased by 68.2% and 56.6%, respectively.
Construction of optimal codes with Homogeneous distance
DING Jian, LI Hongju
2015, 45(7): 588-593. doi: 10.3969/j.issn.0253-2778.2015.07.013
Based on the torsion codes of a (1+λu) constacyclic code with arbitrary length over R(pm,k)=Fpm [u]/< uk >, a bound for the homogeneous distance of a (1+λu) constacyclic code with an arbitrary length over R( pm ,k) is obtained and the exact homogeneous distances of some (1+λu) constacyclic codes over R( pm ,k) are determined, where λ is a unit of R( pm ,k). Furthermore, a new distance-preserving Gray map from RN(pm ,k) (Homogeneous distance) to F pm(k -1) N pm (Hamming distance) is defined. It is proved that the Gray image of a linear (1+λu) constacyclic code of arbitrary length over R(pm ,k) is a linear code over Fpm, and some optimal linear codes over F2, F3, and F4 are constructed under this Gray map.
Study on TZ compact routing schemes based on the coverage of landmark
QIN Xiaowei, ZHOU Mingyang, ZHUO Zhao, FU Zhongqian
2015, 45(7): 594-600. doi: 10.3969/j.issn.0253-2778.2015.07.010
TZ compact routing algorithm guarantees the scalability of routing system by the mechanism of selecting landmarks, but though it does not limit the coverage of landmark or analyse whether the landmarks with small coverage are beneficial for the message transfer. It was found that the landmarks with small coverage go against the performance of compact routing, so landmarks were deleted whose coverage was less than the threshold to keep the coverage of landmarks. Also, its relationships with the average stretch and the average routing table size were analyzed systematically. Applying TZ compact routing algorithm to the snapshots of the AS graph spanning a 10 year period, it was found the average stretch decreases first and then increases gradually, the average routing table size decreases first and then keeps invariant. When choosing an approximate threshold, the improved algorithm shows lower average stretch, lower average routing table size and which effectively improves the performance of TZ compact routing.
A source code oriented static detection method for integer overflow defects
HUANG Hui, LU Yuliang, LIU Lintao, ZHAO Jun
2015, 45(7): 601-607.
Limited by incomplete call graph analysis and path feasibility analysis, current static integer overflow defect detection methods generally return results with high false positives. To reduce this inefficiency, aiming at automatic exploration of the external input triggering integer overflow defects, a new source code oriented detection method was proposed combining call graph analysis, static taint analysis and static symbolic execution, in which a fieldsensitive and flowsensitive pointer analysis method was proposed for constructing an over-approximation of the target program’s real call graph, with a static taint-sink propagation analysis carried out for calculating the potential external input reachable integer overflow defects, on which flowsensitive static symbolic execution is conducted to reduce the false positives introduced by the detection system through justifying the satisfiability of the corresponding defect constraint. Experiments prove the effectiveness of the methodin real-world integer overflow defect detection and false alarm reduction.
An in-place FFT algorithm for high data parallelism architecture
WANG Xiangqian, ZHENG Qilong, WANG Hao, HONG Yi, ZHANG Lei
2015, 45(7): 608-613. doi: 10.3969/j.issn.0253-2778.2015.07.012
The on-chip memory in DSP is small, and applications for DSP are often data-intensive, which requires that space complexity as well as time complexity must be considered when algorithms are designed. So a in-place bit reverse algorithm was proposed. Then, to take advantage of memory bandwidth offered by DSP, an effective in-place FFT algorithm with part bit reverse was designed and implemented on BWDSP. Experiment result shows that, compared with the out-of-place FFT algorithm, its space complexity is significantly reduced,while the loss of time efficiency for the proposed in-place FFT algorithm is acceptable.
Non-fragile stabilization for networked control systems with input delay and randomly occurring gain uncertainties
JANG Shun, PAN Feng
2015, 45(7): 614-622.
The problem of non-fragile stabilization is investigated for a class of nonlinear networked control systems with time-varying input delay and randomly occurring gain uncertainties. A binary switching sequence obeying a conditional probability distribution is introduced to govern the randomly occurring gain fluctuation in controller implementation, which could better reflect the random nature of network-induced phenomena. Attention is focused on the design of a non-fragile static output feedback controller such that the closed-loop systems is mean-square asymptotically stable in the presence of network-induced delay and gain uncertainties. Intensive stochastic analyses and novel inequality bounding techniques are carried out to achieve the existence condition of the stabilization controller, and the desired controller gain can be derived by solving a nonconvex feasibility problem via a modified cone complementary linearization algorithm. Finally, a numerical example is provided to illustrate the effectiveness and superiority of the proposed stabilization method.