Tianjin Key Laboratory of Intelligent Robotics

Tianjin, China

Tianjin Key Laboratory of Intelligent Robotics

Tianjin, China

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Sun M.,Nankai University | Sun M.,Tianjin Key Laboratory of Intelligent Robotics | Xu H.,Nankai University | Xu H.,Tianjin Key Laboratory of Intelligent Robotics | And 4 more authors.
PLoS ONE | Year: 2017

There are various fantastic biological phenomena in biological pattern formation. Mathematical modeling using reaction-diffusion partial differential equation systems is employed to study the mechanism of pattern formation. However, model parameter selection is both difficult and time consuming. In this paper, a visual feedback simulation framework is proposed to calculate the parameters of a mathematical model automatically based on the basic principle of feedback control. In the simulation framework, the simulation results are visualized, and the image features are extracted as the system feedback. Then, the unknown model parameters are obtained by comparing the image features of the simulation image and the target biological pattern. Considering two typical applications, the visual feedback simulation framework is applied to fulfill pattern formation simulations for vascular mesenchymal cells and lung development. In the simulation framework, the spot, stripe, labyrinthine patterns of vascular mesenchymal cells, the normal branching pattern and the branching pattern lacking side branching for lung branching are obtained in a finite number of iterations. The simulation results indicate that it is easy to achieve the simulation targets, especially when the simulation patterns are sensitive to the model parameters. Moreover, this simulation framework can expand to other types of biological pattern formation. © 2017 Sun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Guo Y.,Nankai University | Sun M.,Nankai University | Sun M.,State Key Laboratory of Robotics | Garfinkel A.,University of California at Los Angeles | And 2 more authors.
PLoS ONE | Year: 2014

Recent experimental work in lung morphogenesis has described an elegant pattern of branching phenomena. Two primary forms of branching have been identified: side branching and tip splitting. In our previous study of lung branching morphogenesis, we used a 4 variable partial differential equation (PDE), due to Meinhardt, as our mathematical model to describe the reaction and diffusion of morphogens creating those branched patterns. By altering key parameters in the model, we were able to reproduce all the branching styles and the switch between branching modes. Here, we attempt to explain the branching phenomena described above, as growing out of two fundamental instabilities, one in the longitudinal (growth) direction and the other in the transverse direction. We begin by decoupling the original branching process into two semi-independent sub-processes, 1) a classic activator/inhibitor system along the growing stalk, and 2) the spatial growth of the stalk. We then reduced the full branching model into an activator/inhibitor model that embeds growth of the stalk as a controllable parameter, to explore the mechanisms that determine different branching patterns. We found that, in this model, 1) side branching results from a pattern-formation instability of the activator/inhibitor subsystem in the longitudinal direction. This instability is far from equilibrium, requiring a large inhomogeneity in the initial conditions. It successively creates periodic activator peaks along the growing stalk, each of which later on migrates out and forms a side branch; 2) tip splitting is due to a Turing-style instability along the transversal direction, that creates the spatial splitting of the activator peak into 2 simultaneously-formed peaks at the growing tip, the occurrence of which requires the widening of the growing stalk. Tip splitting is abolished when transversal stalk widening is prevented; 3) when both instabilities are satisfied, tip bifurcation occurs together with side branching. © 2014 Guo et al.


Lu H.,Nankai University | Fang Y.,Nankai University | Ren X.,Tianjin Key Laboratory of Intelligent Robotics | Zhang X.,Tianjin Key Laboratory of Intelligent Robotics
Mechatronics | Year: 2015

For a piezoelectric tube scanner (PTS), this paper proposes an improved direct inverse tracking control algorithm and apply it to an atomic force microscope (AFM) to accomplish high-speed scanning tasks. That is, to enhance the high-speed tracking control performance of a PTS, an improved direct inverse rate-dependent Prandtl-Ishlinskii (P-I) model is firstly constructed, which includes a polynomial module to eliminate the structure nonlinearity. Based on the model, a practical feedforward control law is then designed to implement high-speed tracking control for a high-frequency trajectory with strong robustness, which presents the advantages of high-speed response, simple structure and convenient implementation. Subsequently, the designed feedforward law is combined with a feedback component, and the combined control strategy is employed in an AFM to accomplish fast imaging tasks. Numerous experimental results are then collected, which convincingly demonstrate the superior performance of the proposed practical model/control scheme. © 2015 Elsevier Ltd.


Yuan J.,Nankai University | Yuan J.,Tianjin Key Laboratory of Intelligent Robotics | Liu G.-D.,Nankai University | Sun Q.-X.,Nankai University
Kongzhi Lilun Yu Yingyong/Control Theory and Applications | Year: 2016

Moving target tracking with mobile robots in the indoor environments is addressed. A method to localize the robot and estimate the moving target's states is proposed based on information fusion of a laser scanner and a monocular camera. First, moving target detection, robot self-localization and map building of the environment are simultaneously accomplished using the laser data. Then, a monocular vision-based scheme to detect the target's location is developed for measuring the range and bearing of the target. To achieve effective fusion between two kinds of sensor information, the laser scanner and the monocular camera are jointly calibrated to obtain the relative coordinate transform between them. Finally, a particle filter (PF) with the optimal importance function and importance weights is designed to fuse the measurements of the target's range and bearing from the laser scanner and the monocular camera. The experimental results show that the proposed method can achieve satisfactory tracking performances. © 2016, Editorial Department of Control Theory & Applications South China University of Technology. All right reserved.


Yuan X.,Nankai University | Yuan X.,Tianjin Key Laboratory of Intelligent Robotics | Fang Y.,Nankai University | Fang Y.,Tianjin Key Laboratory of Intelligent Robotics | And 2 more authors.
Proceedings of the World Congress on Intelligent Control and Automation (WCICA) | Year: 2016

When atomic force microscopy (AFM) systems are employed for scanning tasks in liquid, unexpected nonlinearity caused by laser refraction leads to the distortion of AFM images. A novel liquid imaging method is proposed for high-speed AFM systems. Specifically, imaging signal compensation based on liquid force curve analysis is obtained to remedy the distortion from refraction nonlinearity; and then considering the dynamic characteristics of piezo scanner, which limits the performance of high-speed imaging, the dynamic model of piezo scanner in Z-axis is utilized to improve the AFM's imaging accuracy during high-speed scanning. Experimental results are provided to illustrate the efficacy of proposed liquid imaging method. © 2016 IEEE.


Lv L.,Nankai University | Lv L.,Tianjin Key Laboratory of Intelligent Robotics | Sun L.,Nankai University | Sun L.,Tianjin Key Laboratory of Intelligent Robotics
Chinese Control Conference, CCC | Year: 2016

Since target points could be generated quickly and accurately by off-line programming in the industrial robot machining, it is used widely in industrial robots. Due to installation error and mismachining tolerance which causes the offset of processing paths in the actual machining process, the registration algorithms for path calibration would be involved. While the traditional approach would converge to local optimal solution, an improved registration algorithm based on geometric properties of point clouds is proposed in the paper. Firstly, feature point sets are acquired by the curvature of point clouds and matched by traditional PCA algorithm, an initial value for precise registration is provided. Secondly, the improved ICP algorithm by curvature is utilized to modify the former result and reduce the execution time of precise registration, the path calibration can be achieved. The experimental result of the approach is validated in this paper which is significative for calibration of processing paths. © 2016 TCCT.


Yuan J.,Nankai University | Yuan J.,Tianjin Key Laboratory of Intelligent Robotics | Chen H.,Nankai University | Sun F.,Nankai University | Huang Y.,Nankai University
IEEE Transactions on Instrumentation and Measurement | Year: 2015

People tracking based on multisensor information fusion is addressed. A framework is presented for fusing the laser range finder (LRF) data and the monocular camera data. Based on this framework, an LRF-based detection algorithm is proposed to identify the pairs of human legs, by combining motion information and metric features. Moreover, a geometric observation model is developed for the camera to extract both the range and bearing measurements of the target person by focusing the target's shoes with the camera. Then, a near-optimal particle filter is designed to fuse the measurements from the LRF and the camera. To prevent the sample impoverishment, a procedure of sample diversity improvement is used after the resampling step. The full occlusion problem is solved using image matching based on speeded up robust feature. Note that either of the LRF and the camera can work independently, since both the range and bearing are simultaneously acquired from the LRF or the camera. As a result, flexible and robust tracking can be achieved. Extensive experiments demonstrate that the proposed approach achieves high tracking accuracy and robustness. Especially, only a very small number of particles suffice to maintain good tracking performance. © 1963-2012 IEEE.


Lin X.,Nankai University | Lin X.,Tianjin Key Laboratory of Intelligent Robotics | Kunpeng G.,Nankai University | Kunpeng G.,Tianjin Key Laboratory of Intelligent Robotics
Proceedings of the 2015 27th Chinese Control and Decision Conference, CCDC 2015 | Year: 2015

The continuous blood pressure values can be calculated by the pulse wave transmission velocity. The accuracy of measuring human blood pressure using pulse wave transmit velocity is significantly influenced by the accuracy of the pulse wave feature point. This paper designs a pulse waveform quality evaluation function to calculate the pulse wave quality index. The reliability evaluation of photoplethysmography (PPG) feature point selection can be evaluated by the pulse wave quality index automatically. The fusion of blood pressure value calculated by different pulse wave feature point is calculated by the Kalman filter. Thus a more accurate continuous blood pressure measurement result is got. This method is evaluated by the MIMIC database. Compared with SBP calculated by single PPG feature point, this method has the least extreme errors and the smallest root mean square error (rMSE) of systolic blood pressure(SBP). © 2015 IEEE.


Lin X.,Nankai University | Lin X.,Tianjin Key Laboratory of Intelligent Robotics | Anqi F.,Nankai University | Anqi F.,Tianjin Key Laboratory of Intelligent Robotics
Proceedings of the 2015 27th Chinese Control and Decision Conference, CCDC 2015 | Year: 2015

From the perspective of the limited energy in wireless visual sensor networks, based on the lifting wavelet transform method run in the elimination mode and SPECK coding by skipping some high-frequency sub-bands, an energy effective image compression coding method is proposed according to the adaptive requirement of the image quality and energy consumption. The experiments show that the method has a good effect on energy conservation, which is more obvious in the image transmission at low bit rate. © 2015 IEEE.


Lu H.,Nankai University | Lu H.,Tianjin Key Laboratory of Intelligent Robotics | Fang Y.,Nankai University | Fang Y.,Tianjin Key Laboratory of Intelligent Robotics | And 4 more authors.
2014 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale, 3M-NANO 2014 - Conference Proceedings | Year: 2014

To enhance the performance for high-speed tracking control of a piezoelectric tube actuator (PTA), an improved direct inverse rate-dependent PI model is obtained in this paper, and then adopted to design a practical feedforward controller achieving high-speed tracking control for a high-frequency trajectory with strong robustness. Specifically, based on the Prandtl-Ishlinskii (PI) model, an improved direct rate-dependent inverse model is set up for the PTA, with a polynomial function module introduced to eliminate the influence caused by the structure nonlinearity. Then, considering the features of the PTA structure, some preprocessing procedure is proposed to handle the collected experimental data, with the results utilized to identify all the unknown parameters over a wide bandwidth. Based on the obtained model, a practical feedforward controller, which presents the advantages of high-speed response, simple structure and convenient implementation, is then designed to enable the PTA to track high-frequency trajectories with satisfactory precision. Some experimental results are provided, which clearly demonstrate the high precision of the constructed/identified model, and the satisfactory performance of the proposed practical feedforward tracking control law. © 2014 IEEE.

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