Yanlin He

A Spherical Robot based on all Programmable SoC and 3-D Printing

As the competition and exploration on marine is going more intense, intelligent underwater robots or autonomous underwater vehicles have become important tools to accomplish tasks such as ocean geologic survey, mineral exploration, victims rescue, military reconnaissance, etc. The mechanical structure and electronic control module design, which have long been research hotspots in this field, are in direct relation to the performance, reliability, maintainability and deployment ability of underwater robots. Existing designs commonly develop the body of robots with a large quantity of components or parts and realize information processing and motion control by using multiple kinds of electronic devices. This paper proposed a novel technical solution for underwater robots design. 3-D printing technology was adopted to construct the body of our spherical amphibious robots directly, which eliminated manufacturing difficulty, shortened the production cycle and improved water-tightness. Xilinx Zynq-7000 All Programmable SoC was used to integrate motor control, sensor management, data acquisition and other functional units or circuits into a single chip. Moreover, a universal FMC slot for high speed board and four PMod sockets for low speed modules were provided on the mother board of the electronic control module to expand functions, upgrade hardware or install scientific instruments for special missions. By introducing 3-D printing and latest SoC technologies, the system complexity of the spherical robot was significantly reduced, which improved reliability. Meanwhile, the design room for intelligent robots was broadened with modular design and all programmable SoC. The design in this paper may have reference value for multipurpose underwater robots or vehicles.

Visual Detection and Tracking System for a Spherical Amphibious Robot

With the goal of supporting close-range observation tasks of a spherical amphibious robot, such as ecological observations and intelligent surveillance, a moving target detection and tracking system was designed and implemented in this study. Given the restrictions presented by the amphibious environment and the small-sized spherical amphibious robot, an industrial camera and vision algorithms using adaptive appearance models were adopted to construct the proposed system. To handle the problem of light scattering and absorption in the underwater environment, the multi-scale retinex with color restoration algorithm was used for image enhancement. Given the environmental disturbances in practical amphibious scenarios, the Gaussian mixture model was used to detect moving targets entering the field of view of the robot. A fast compressive tracker with a Kalman prediction mechanism was used to track the specified target. Considering the limited load space and the unique mechanical structure of the robot, the proposed vision system was fabricated with a low power system-on-chip using an asymmetric and heterogeneous computing architecture. Experimental results confirmed the validity and high efficiency of the proposed system. The design presented in this paper is able to meet future demands of spherical amphibious robots in biological monitoring and multi-robot cooperation.

3D Printing Technology-based an Amphibious Spherical Robot

It has long been recognized that the employment of underwater robots have important practical significance, which includes pipe survey, oceanic search, under-ice exploration, mine reconnaissance, dam inspection, ocean survey and so on. Owing to the limitation of underwater environment, some regular sized robots are not suitable for limited spaces. Thus some micro-robots appeared, while sacrificed important abilities such as locomotion velocity and enduring time to achieve compact sizes. Then a mother-son robot system was proposed in our previous researches, which included several micro-robots as sons and an amphibious spherical robot as the mother. The mother robot was adopted to make up for the shortages of microrobots. This paper mainly focused on the structure and mechanism of the mother robot. The mother robot was designed with a spherical structure, which was composed of a fixed hemisphere hull and two operable quarter spherical hulls. It was actuated by four water-jet propellers and ten servomotors, capable of moving on land and in underwater environment. We developed a prototype and evaluated its walking and swimming motions in our previous experiments. Due to some problems in the process of assembly, the motion stability and reliability performed not so well. So, in this paper, we improved the structure and mechanism of the robot based on 3D Printing, which could eliminate some manufacture difficulties, shorten the production cycle, improve water-tightness, and enhance the robots overall stability, compactness and aesthetics.

Skating motion analysis of the amphibious quadruped mother robot

Biomimetic underwater robots are of great interest for underwater monitoring operations, such as pollution detection and video mapping. However, in some restricted underwater environments, regular sized robots are not suitable for real applications. Therefore, we designed several novel types of bio-inspired microrobots, using ionic polymer metal composite (IPMC) and shape memory alloy (SMA) actuators. These microrobots possess some attributes of compact structure, multi-functionality, flexibility, and precise positioning. However, for real-world applications, they lacked the attributes of long endurance, high stable speed, and large load capacity. To implement these characteristics, we proposed a mother-son robot system, which includes several microrobots as sons and a newly designed amphibious spherical robot as the mother. Inspired by the amphibious turtle, the mother robot was designed with a spherical body and four legs. It was actuated by four water-jet propellers and ten servomotors, capable of walking motion on land and three directional moving motions in the underwater environment. We developed a prototype of the amphibious spherical robot and evaluated its walking and swimming motions experimentally. To improve the walking velocity on level or comparatively smooth terrain, we added four passive wheels on four legs with lightweight. The skating trajectory was investigated to implement high terrain adaptability of the mother robot.

A low-power SoC-based moving target detection system for amphibious spherical robots

A moving target detection and tracking system is critical important for autonomous mobile robot to accomplish complicated tasks. Aiming at application requirements of our amphibious spherical robot proposed in previous researches, a low-power and portable moving target detection system was designed and implemented in this paper. Xilinx Zynq-7000 SoC (System on Chip) was used to fabricate the image processing system of the robot for detection and tracking. An OmniVision OV7670 COMS image sensor controlled by customized IP cores in the PL (Programmable Logic) of the SoC was adopted to acquire 640×480 RGB images at 30 frames per second. The Gaussian background modeling method was implemented with Vivado HLS in the PL to detect moving targets. And a FCT (Fast Compressive Tracking) tracker with motion estimation mechanism was running in the PS (Processing System) of the SoC to track targets captured by the detection subsystem subsequently. Besides, the dynamical power management (DPM) and the dynamical voltage frequency scaling (DVFS) mechanisms were used for a higher power-efficiency. Experimental results verified the validation and performance of the detection system. The design in this paper may have reference value for vision-based mobile robots or vehicles.

A multifunctional underwater microrobot for mother-son underwater robot system

In past few years, various underwater microrobots have been developed with the micromachining technology, development of smart actuators and biomimetic applications. Most of them possess the attributes of flexibility and compact structure. However, their endurances, moving speeds, and load capacities for power supplies and sensors are limited for the small sizes. So, these microrobots are not suitable for the real-world applications. To solve these problems, we proposed a mother-son robot system, which included several microrobots as sons and a newly designed amphibious spherical robot as the mother. The mother robot was actuated by four water-jet propellers and eight servomotors, capable of providing a stable high speed and carrying the microrobots to a desired target location where tasks were to be performed. To implement the mother-son robot system, we proposed a multifunctional underwater microrobot and developed the prototype by using ionic polymer metal composite (IPMC) actuators. The microrobot could perform walking, rotating, grasping, floating, and swimming motions with the compact structure. Then we evaluated its moving speeds in the water tank. At last, we carried out the releasing experiment to demonstrate the feasibility of the mother-son robot system.

An attitude estimation system for amphibious spherical robots

As one of the most effective tools for exploring the ocean, automatic underwater vehicles have attracted a lot of attentions for years. But some key problems have not been solved properly. It is especially difficult to design underwater vehicles in small size. In this paper, three inertial sensors were adopted to fabricate an attitude estimation system, which provided posture information for our amphibious spherical robot to realize motion control and autonomous navigation. The pitch, roll and heading angel were acquired from current robot attitude matrix, which was calculated from the quaternion algorithm. And the attitude was corrected by the fusion of accelerometer and magnetic sensor. Experimental results verified the validation and precision of the robotic attitude estimation system. It has manifested that the system is effective to realize the robot control and navigation.

Numerical simulation and hydrodynamic analysis of an amphibious spherical robot

Considering that the necessity of amphibious operation in harsh environment, this paper firstly presents the structure of an amphibious spherical robot based on 3D printing technology, which can act as a carrier of reconnaissance equipment, weapons systems and communications systems, and perform a variety of tasks near the sea and beaches. Since the structure of the robot had features of amphibious characteristics and quadruped gaits. Inevitably, there are new problems in the process of kinetic mechanism analysis. It is hydrodynamic characteristic that is a critical factor for underwater robot. This paper presents the investigation of hydrodynamic performance of concept structure design of an amphibious spherical robot based on 3D printing technology with three basic motion-horizontal forward motion, ascending motion and sinking down motion in vertical plane. Firstly, the structural configuration, principle of work and performance parameter of the amphibious spherical robot based on 3D printing technology were described. Then the ANSYS WORKBENCH software was employed to establish the 3D model and meshing result of the amphibious spherical robot as well as its flow fields. For the reason that the complex structure of our amphibious spherical robot based on 3D printing technology will cause some limitations on hydrodynamic analysis, its 3D models was properly simplified and ANSYS FLUENT software was then used to analyze the impact of hydrodynamic factors according its three motion models, and compared the simulation results with the theoretical values. Finally, the pressure contours, velocity vectors and drag coefficient showed the detail of the flow field when the amphibious spherical robot is performing its three basic motion.

IPMC actuator-based a movable robotic venus flytrap

Nature is a perfect model for a robot. Besides the insects and underwater animals, some carnivorous plants which are capable of rapid movement, such as mimosa, the venus fly trap, the telegraph plant, sundews and bladderworts, are of great interest for the biomimetic robot design. Carnivorous plants, such as Venus flytrap, can be turned on in a controlled manner to capture prey by using their trigger hairs as detecting sensors. In our previous research, we designed a robotic Venus flytrap by using two ionic polymer metal composite (IPMC) actuators and one proximity sensor. To enlarge its working area in real applications, we improved it by integrating biomimetic walking and rotating motions into the previous version. First, we proposed a conceptual structure of the improved robotic Venus flytrap which consisted of two IPMC lobes, one proximity sensor, and eight IPMC legs. Then, we developed a prototype movable robotic Venus flytrap and evaluated its walking and rotating speeds by using different applied signal voltages. At last, to reduce the gaps between two IPMC lobes, we improved the robotic flytrap by using three IPMC lobes. The experimental results showed a good performance.

An adaptive compressive tracking algorithm for amphibious spherical robots

As a critical important function for autonomous mobile robots, visual tracking is a challenge work in the field of computer vision, for the reason that factors like illumination variance, partial occlusions and target appearance changes shall be carefully considered. Focus on applications of our amphibious spherical robots, an adaptive visual tracking algorithm was proposed on the basis of compressive tracking. A feature selection method was designed to choose random Haar-like feature templates in various scales by calculating Fishers criterion functions of features. On this basis, a random feature pool, which tried to preserve discriminative features at different frames, were constructed and then maintained on-line to provide candidate appearance model of the target. Moreover, an adaptive update mechanism was adopted for selectively updating feature templates and classifier parameters of the improved compressive tracking algorithm, which alleviated the drift problem. Experimental results with various image sequences demonstrated the effectiveness and robustness of the proposed tracking algorithm, which can meet practical application requirements of the amphibious spherical robots.