Hou Zhenxiu

GPU based real-time SLAM of six-legged robot

Vision and AHRS (attitude and heading reference system) sensors fusion strategy is prevalent in recent years for the legged robot’s SLAM (Simultaneous Localization and Mapping), due to its low cost and effectiveness in the global positioning system. In this paper, a new adaptive estimation algorithm is proposed to achieve the robot SLAM by fusing binocular vision and AHRS sensors. A novel acceleration algorithm for SIFT implementation based on Compute Unified Device Architecture (CUDA) is presented to detect the matching feature points in 2D images. All the steps of SIFT were specifically distributed and implemented by CPU or GPU, according to the step’s characteristics to make full use of computational resources. The registration of the 3D feature point cloud is performed by using the iterative closest point (ICP) algorithm. Our GPU-based SIFT implementation can run at the speed of 30 frames per second (fps) on most images with 900 × 750 resolution in the test. Compared to other methods, our algorithm is simple to implement and suitable for parallel processing. It can be easily integrated into mobile robot’s tasks like navigation or object tracking, which need the real-time localization information. Experiments results showed that in the unknown indoor environments, the proposed algorithm‘s operation is stable and the positioning accuracy is high.

Hydrodynamic performance and flow control of two flexible bodies in fish schooling-like configuration

Swimming in side-by-side configuration is common in the schooling of fish. In this work, the hydrodynamic performance of two flexible plates in side-by-side configuration is modelled and simulated. The simulations are implemented by an in-house parallelized algorithm, which fully coupling the lattice Boltzmann method (LBM) and immersed boundary (IB) mathematically. The Reynolds number scaled by the plates length and incoming velocity is 200 to 500 in our study, the transverse gap distance is varied from 0 to 5. The results show that the systems coupling motions and hydrodynamics properties are highly depended on the gap distance. Based on the evolutions of wake pattern, the motion modes can be classified as four types, which are single-plate mode, in-phase mode, anti-phase mode and decoupled mode. Also, we find that the drag coefficient for one plate are always equal to another, and the drag reduction is happened when the distance is in the regime corresponding to in-phase mode. This work may help us to develop the novel underwater robots inspired by fish locomotion.

Hydrodynamic interactions between a cylinder and an attached elastic plate

An elastic plate behind a rigid cylinder in viscous flow is modeled numerically by an immersed boundary-lattice Boltzmann method (IB-LBM). The hydrodynamic interactions of a upstream cylinder and a adjacent passively flapping plate are studied by varying the length and bending stiffness of the plate. Two patterns of the plate are found in the simulation results, if the plate is short enough, it would curl up because of the attraction of the suction zone behind the cylinder. With the increase of the plates length, it will stretch and flap in a stable period. The cylinder has a strong influence on the dynamics of the plate and the plate also changes the vortex shedding of the cylinder and the shape of suction zone. With a downstream adjacent plate, the cylinder can always enjoys a drag reduction, longer the plate is, less drag the cylinder experiences. The vortex shedding frequency of the cylinder is larger than that of the single cylinder and equal to the plates flapping frequency. This study may help to understand the energy saving of flexible bodies stay in the wake of a rigid structure and the hydrodynamic interactions between them.

AC electric field enhanced rapid serum immunoassay for Johne’s Disease

Early immunoassay is essential at the beginning of human/animal disease diagnosis. Due to limited concentration of antibody and slowly nature diffusion, it takes hours or more time to detect the disease specific antibody in serum using traditional diagnosis methods. A novel approach is proposed to enhance the convection and mass transfer in the micro channel based on AC electroth- ermal effect and dielectrophoresis, improving the antigen-antibody specific binding efficiency greatly, even the antibody in the serum at low concentration level. A platform with interdigited electrode array on silicon wafer and PDMS micro channel is developed for bovine paratuberculosis(Johnes Disease) rapid diagnosis. It only takes 2 minutes to distinguish positive serum from negative ones by measuring the change of electrode/serum interfatial electrical double layer capacitance at real time. Ac electric field enhanced rapid serum immunoassay diagnosis mechanism is presented based on AC electrolthermal and dielectrophoresis theory. Convection and mass transfer is greatly enhanced by AC electric field, leading to a rapid specific binding. The change of disease specific antibody concentration in the micro channel is simulated, showing validity of the novel rapid immunoassay diagnosis method.