Visual Detection and Tracking System for a Spherical Amphibious Robot

Preliminary study of abnormalities in saccade dynamics in patients with hyperthyroidism with no pre-existing eye damage

The present study investigated the relationship between hyperthyroidism and thyroid-associated ophthalmopathy by examining saccade dynamics to identify defects in eye tracking in patients with hyperthyroidism with no pre-existing eye damage and sensitive indicators that discriminated eye tracking ability in hyperthyroidism. A total of 33 outpatients with hyperthyroidism and 26 healthy controls participated in visually guided saccade (VGS) analysis. Patients with hyperthyroidism were divided into groups based on their medication status (medicated vs. unmedicated). Main sequence analysis was performed to identify differences in peak velocity and duration, and a general linear model (GLM) was used to identify differences in latency, peak acceleration and peak deceleration among the groups. The present study compared differences in the Spearman's correlation coefficient of the duration of saccades and the acceleration asymmetric index (R_AD) among the groups. V_max values (V_max was the asymptotic value of the PV of saccades of large amplitude) were significantly different between the healthy control and unmedicated-hyperthyroidism groups. The results of the GLM-based analysis indicated no significant differences in saccade latency among the three groups. Peak acceleration was significantly different between the healthy control and unmedicated-hyperthyroidism groups (P<0.01). Peak deceleration was significantly different between the healthy control, unmedicated- and medicated-hyperthyroidism groups (P<0.01). R_AD was significantly different between the healthy control and medicated-hyperthyroidism groups (P=0.004). The results of the present study suggested that patients with hyperthyroidism with no pre-existing eye damage exhibited significantly altered saccade dynamics during VGS. Therefore, R_AD may be used as an indicator to monitor the level of eye movement coordination.

Hydrodynamic Analysis-Based Modeling and Experimental Verification of a New Water-Jet Thruster for an Amphibious Spherical Robot

Thrusters are the bottom actuators of the amphibious spherical robot, and play an important role in the motion control of these robots. To realize accurate motion control, a thrust model for a new water-jet thruster based on hydrodynamic analyses is proposed in this paper. First, the hydrodynamic characteristics of the new thruster were numerically analyzed using computational fluid dynamics (CFD) commercial software CFX. The moving reference frame (MRF) technique was utilized to simulate propeller rotation. In particular, the hydrodynamics of the thruster were studied not only in the axial flow but also in oblique flow. Then, the basic framework of the thrust model was built according to hydromechanics theory. Parameters in the basic framework were identified through the results of the hydrodynamic simulation. Finally, a series of relevant experiments were conducted to verify the accuracy of the thrust model. These proved that the thrust model-based simulation results agreed well with the experimental results. The maximum error between the experimental results and simulation results was only 7%, which indicates that the thrust model is precise enough to be utilized in the motion control of amphibious spherical robots.

A system on chip-based real-time tracking system for amphibious spherical robots

Aiming at vision applications of our amphibious spherical robot, a real-time detection and tracking system adopting Gaussian background model and compressive tracking algorithm was designed and implemented in this article. Considering the narrow load space, the limited power resource and the specialized application scenarios of the robot, a heterogeneous computing architecture combining advanced Reduced Instruction-Set Computer (RISC) machine and field programmable gate array was proposed on the basis of Zynq-7000 system on chip.Under the architecture, main parts of the vision algorithms were implemented as software programs running on the advanced RISC machine-Linux subsystem. And customized image accelerators were deployed on the field programmable gate array subsystem to speed up the time-consuming processes of visual algorithms. Moreover, dynamic reconfiguration was used to switch accelerators online for reducing resource consumption and improving system adaptability. The word length of accelerators was optimized with simulated annealing algorithm to make a compromise between calculation accuracy and resource consumption. Experimental results confirmed the feasibility of the proposed architecture. The single board tracking system was able to provide an image processing rate of up to 89.2 frames per second at the resolution of 320 × 240, which could meet future demands of our robot in biological monitoring and multi-target tracking.