Advancements in the field of autonomous underwater vehicle

Swarm Robotics (SR) is an extension of the study of Multi-Robot Systems that exploits concepts of communication, coordination and collaboration among a large number of robots. The massive parallelization yielded by the robots working together can make a task faster than in the case of the usage of a single complex robot. One of the main aspects in robotic swarms is that the control is decentralized by definition and distributed among the robots of the swarm, improving the system robustness and fault-tolerance. Furthermore, this characteristic often allows the emergence of collective behaviors from the robot's interaction with each other and with the environment through their embodied sensors and actuators. In most cases, the number of inputs from sensor readings turns analytical solutions hard or even impossible. Thus, many ad-hoc approaches are contributed to deal with the situation at hand. The main goal of this review is to find out, through the study of existing research works of the field, the reason behind the lack of exploitation of swarm robotic systems in real-world applications. For this purpose, we first review the different possibilities of study in SR: physical and simulated robotic platforms, development methodologies and the variety of basic tasks and collective behaviors. We then briefly describe some fields related do SR that have a big impact on the development of SR. After that, based on existing taxonomies found in literature, we categorize existing research works regarding SR in two large main groups: those that deal with SR design and those that deal with tasks as required in SR. The review of both existing robots and techniques in the literature show a diversity of approaches to discuss SR issues. Nonetheless, it is easily noticeable from these works that there is a clamant absence of solid real-world applications of SR. An analysis of the interests and bottlenecks of this field indicates that the number of research works is smaller than those in other related areas. This suggests that, even though with many research studies, the field of SR is not yet mature enough, mainly due the absence of a universal methodology and generic robots that can be used in any, or at least in many, applications. Thus, we emphasize, discuss and analyze the urgent need for standardization of many aspects in SR, including hardware and software, as to allow a possible flourishing of SR applicability to real-world applications. This standardization could accelerate a great deal the field of SR, thus facilitating the development of SR solutions for applications that impact our daily life.

Review of methodologies and tasks in swarm robotics towards standardization

This paper describes an improved three-dimensional (3D)-printed, low-cost, multi-functional, high-maneuverability, high-concealment, turtle-inspired mobile amphibious spherical robot for environmental monitoring and data collection. The major challenge in developing such a robot lies in its limited physical size and compact structure that allows for only one type of propulsion system to be used both on land and in water. This paper focuses on the optimization of the kinematic and hydrodynamic model of the amphibious spherical robot, so as to improve the control accuracy and stability of the robot. In order to optimize some kinematic and dynamic modeling parameters of the robot, such as the drag coefficient of robot, the angular velocity and swing angle of each joint, a solid model of the 3D-printed robot was built by SolidWorks. Our simulation results and theoretical calculations confirmed the validity of the virtual model and facilitated identification of key parameters in the design. The correctness of the modeling was demonstrated by the stability of consecutive crawling and underwater movements, providing a basis for driving and controlling methods for this amphibious robot, as well as guidance for the robot's gait trajectory. Combining the robot's crawling mechanism with related simulation results, an optimized prototype of the 3D-printed amphibious spherical robot was constructed. A series of crawling experiments on a common floor were performed with the improved robot prototype, which was also done using the previous robot. The results were evaluated by a novel optical positioning system, NDI Polaris. Moreover, several experiments were carried on land crawling and underwater swimming to verify the performance of the improved amphibious spherical robot. Comparison of experimental and simulation results demonstrated the improved robot had better amphibious motion performance, as well as more potentiality and applicability to the real structures.

Modeling and experimental evaluation of an improved amphibious robot with compact structure

A visual tracking system is essential as a basis for visual servoing, autonomous navigation, path planning, robot-human interaction and other robotic functions. To execute various tasks in diverse and ever-changing environments, a mobile robot requires high levels of robustness, precision, environmental adaptability and real-time performance of the visual tracking system. In keeping with the application characteristics of our amphibious spherical robot, which was proposed for flexible and economical underwater exploration in 2012, an improved RGB-D visual tracking algorithm is proposed and implemented. Given the limited power source and computational capabilities of mobile robots, compressive tracking (CT), which is the effective and efficient algorithm that was proposed in 2012, was selected as the basis of the proposed algorithm to process colour images. A Kalman filter with a second-order motion model was implemented to predict the state of the target and select candidate patches or samples for the CT tracker. In addition, a variance ratio features shift (VR-V) tracker with a Kalman estimation mechanism was used to process depth images. Using a feedback strategy, the depth tracking results were used to assist the CT tracker in updating classifier parameters at an adaptive rate. In this way, most of the deficiencies of CT, including drift and poor robustness to occlusion and high-speed target motion, were partly solved. To evaluate the proposed algorithm, a Microsoft Kinect sensor, which combines colour and infrared depth cameras, was adopted for use in a prototype of the robotic tracking system. The experimental results with various image sequences demonstrated the effectiveness, robustness and real-time performance of the tracking system.

http://www.guolab.org/Papers/2015/SENSORS2015.pdf

A Kinect-Based Real-Time Compressive Tracking Prototype System for Amphibious Spherical Robots

We describe the novel, multiply gaited, vectored water-jet, hybrid locomotion-capable, amphibious spherical robot III (termed ASR-III) featuring a wheel-legged, water-jet composite driving system incorporating a lifting and supporting wheel mechanism (LSWM) and mechanical legs with a water-jet thruster. The LSWM allows the ASR-III to support the body and slide flexibly on smooth (flat) terrain. The composite driving system facilitates two on-land locomotion modes (sliding and walking) and underwater locomotion mode with vectored thrusters, improving adaptability to the amphibious environment. Sliding locomotion improves the stability and maneuverability of ASR-III on smooth flat terrain, whereas walking locomotion allows ASR-III to conquer rough terrain. We used both forward and reverse kinematic models to evaluate the walking and sliding gait efficiency. The robot can also realize underwater locomotion with four vectored water-jet thrusters, and is capable of forward motion, heading angle control and depth control. We evaluated LSWM efficiency and the sliding velocities associated with varying extensions of the LSWM. To explore gait stability and mobility, we performed on-land experiments on smooth flat terrain to define the optimal stride length and frequency. We also evaluated the efficacy of waypoint tracking when the sliding gait was employed, using a closed-loop proportional-integral-derivative (PID) control mechanism. Moreover, experiments of forward locomotion, heading angle control and depth control were conducted to verify the underwater performance of ASR-III. Comparison of the previous robot and ASR-III demonstrated the ASR-III had better amphibious motion performance.

Hybrid Locomotion Evaluation for a Novel Amphibious Spherical Robot

Amphibious micro-robots are being developed for complicated missions in limited spaces found in complex underwater environments. Therefore, compact structures able to perform multiple functions are required. The robots must have high velocities, long cruising times, and large load capacities. It is difficult to meet all these requirements using a conventional underwater micro-robot, so we previously proposed an amphibious spherical father---son robot system that includes several micro-robots as son robots and an amphibious spherical robot as a father robot. Our father robot was designed to carry and power the son robots. This paper discusses improvements to the structure and mechanism of the father robot, which was designed to have a spherical body with four legs. Based on recent experiments in different environments, we have improved the father robot by adding four passive wheels, and we have redesigned its structure by means of three-dimensional printing technology, resulting in greatly improved velocity and stability. Moreover, due to the complexity and uncertainty of many underwater environments, it is essential for the father robot to have adequate structural strength. We analyzed the movement mechanisms and structural strength using finite element analysis to obtain the deformation and equivalent stress distributions of the improved robot. The results provide support for further analysis of the structural strength and optimal design of our amphibious spherical father robot.

http://www.guolab.org/Papers/2015/he1.pdf

Preliminary mechanical analysis of an improved amphibious spherical father 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 micro- robots. 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 robot's overall stability, compactness and aesthetics.

http://www.guolab.org/Papers/2014/ICMA2014-240.pdf

3D Printing Technology-based an Amphibious Spherical Robot

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 re- search hotspots in this field, are in direct relation to the perfor- mance, reliability, maintainability and deployment ability of un- derwater 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 univer- sal FMC slot for high speed board and four PMod sockets for low speed modules were provided on the mother board of the elec- tronic 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.

http://www.guolab.org/Papers/2014/ICMA2014-026.pdf

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

The invention relates to a robot, in particular to a multi-degree-of-freedom amphibious spherical robot. The multi-degree-of-freedom amphibious spherical robot comprises a spherical shell, four mechanical legs and a control driving system. According to the technical scheme, the spherical shell comprises a semispherical upper cover, two quarter spherical shell bodies and a round partition plate; the four mechanical legs are symmetrically installed on the bottom face of the round partition plate at 90-degree intervals; the control driving system is installed in the semispherical upper cover and is sealed through a waterproof inner shell. According to the multi-degree-of-freedom amphibious spherical robot, land propelling, underwater propelling and the spherical appearance structure are effectively combined, and the underwater robot is made to have the high maneuvering capability in the land, water and transition environments.

Multi-degree-of-freedom amphibious spherical robot

Considering the complicated disturbance in amphibious circumstance, usually it is difficult to solve the control problem for a complex system of an amphibious robot. This paper proposes a neutral network PID controller which has a great advantage on processing online for an amphibious spherical robot due to their nonlinear dynamics. We overcome the difficulties by combining the neutral network method and traditional PID control to reach the goal of tracking online fast. The stability of our controller is analyzed according to the Lyapunov method. The performance of the proposed controller is investigated in simulation. The controller can be easily realized in hardware as for its simple structure. The linear velocity of the spherical robot can be controlled to precisely track any desired trajectory in robot-fixed coordinate system. The effectiveness of the controller is verified by simulation results based on neutral network PID. It realizes a better control on spherical amphibious robot by heading experiments in water.

http://www.guolab.org/Papers/2014/ICMA2014-331.pdf

Zhe Wang

Papers

Preliminary mechanical analysis of an improved amphibious spherical father robot

3D Printing Technology-based an Amphibious Spherical Robot

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

Multi-degree-of-freedom amphibious spherical robot

The Application of PID Control in Motion Control of the Spherical Amphibious Robot