Chunfeng Yue

Hydrodynamic Analysis of the Spherical Underwater Robot SUR-II

Abstract This paper describes the development of the second-generation Spherical Underwater Robot (SUR-II). The new SUR-II has an improved propulsion system structure, resulting in better performance compared with the original design. This paper focuses on the characteristics of the water-jet thruster and the spherical hull of the SUR-II. To analyse its hydrodynamic characteristics, the main hydrodynamic parameters of the SUR-II were estimated based on two reasonable assumptions and a reasonable dynamic equation was proposed to describe the relationship between force and velocity. Drag coefficients were calculated separately for vertical and horizontal motions due to the fin on the robots equator and the holes in the robots hull. The holes had a particularly adverse effect on the horizontal drag coefficient. A hydrodynamic analysis using computational fluid dynamics was then carried out to verify the estimated parameters. The velocity vectors, pressure contours and drag coefficient for each state of motion were obtained. Finally, the propulsive force was determined experimentally to verify the theoretical calculations and simulation results.

Development of an Amphibious Turtle-Inspired Spherical Mother Robot

Robots play an important role in underwater monitoring and recovery operations, such as pollution detection, submarine sampling and data collection, video mapping, and object recovery in dangerous places. However, regular-sized robots may not be suitable for applications in some restricted underwater environments. Accordingly, in previous research 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, they lack the attributes of long endurance, stable high speed, and large load capacity necessary for real-world applications. To overcome these disadvantages, we proposed a mother-son robot system, composed of several microrobots as sons and a newly designed amphibious spherical robot as the mother. Inspired by amphibious turtles, the mother robot was designed with a spherical body and four legs with two Degrees of Freedom (DOF). It is actuated by four vectored water-jet propellers and ten servomotors, and it is capable of walking on land and cruising underwater. We analysed the mother robot’s walking and underwater cruising mechanisms, constructed a prototype, and carried out a series of experiments to evaluate its amphibious motions. Good motion performance was observed in the experiments.

Preliminary concept of a novel spherical underwater robot

This paper describes the preliminary concept of a novel spherical underwater robot (SUR). The novel SUR employs a spherical hull and equipped with multiple vectored water–jet–based thrusters. This paper focuses on the preliminary design of the novel spherical underwater robots structure. Based on the structure, the finite element analysis is used to test the strength of structure and the feasibility of the concept. Meanwhile, the simulation of the robots dynamics and kinematics is also finished to verify the stabilisation and validity of the new structure. On the basis of the structural characteristics of the spherical robot, its dynamic model is derived by applying the Lagrange–Routh equations briefly. A 3D model of robot is built by CATIA and finite element method is applied base on the model. Then the model is exported to ADAMS for simulation. The results of simulation by combining MATLAB/Simulink with ADAMS are presented. The simulation results indicate that the proposed virtual prototype system has the capability of simulative demonstration and performance validation, and can provide an innovative approach for AUV graphic simulation.

ANSYS FLUENT-based modeling and hydrodynamic analysis for a spherical underwater robot

For an underwater robot, hydrodynamic characteristics are very important. This paper focuses on the research of the hydrodynamic analysis of a spherical underwater robot with three motions, horizontal motion, vertical motion and yaw motion. Firstly, the prototype of related second generation spherical underwater robot (SUR-II) was developed. In order to analyze the hydrodynamic characteristics of the spherical underwater robot exactly, CATIA software was employed to establish the 3D models of the flow field. For the complex structure of the developed underwater robot causing the limitations on meshing and hydrodynamic analysis, we simplified the 3D models properly. Finally, we used ANASYS FLUENT to analyze the three models and compare the simulation results to the theoretical values. It showed that the error was less than 3%. The pressure contours and velocity vectors showed the detail of the flow field when the robot implemented the basic motions.

Analysis and improvement of the water-jet propulsion system of a spherical underwater robot

In this paper, we present the static analysis of a water-jet propulsion system. First, some previous researches in this field are introduced. Then, the motivation of static analysis is proposed. Based on that, we analyze the original mechanism that has been completed. After analyzing disadvantages of the mechanical structure of the propulsion system, improvement is carried out. We extend the motion range of water-jet thruster to +60°~-90°. Finally, the static analysis is carried out to improve the mechanical structure and compared the results with original design. The comparison result shows that about 50% deformation is declined. The static analysis is very useful to improve the propulsive accuracy of the water-jet propulsion system.

Mechatronic System and Experiments of a Spherical Underwater Robot: SUR-II

This paper describes the structural design of the SUR-II spherical underwater robot. A spherical shape was adopted due to its outstanding shock resistance and flexibility. We designed and developed vectored water-jet thrusters to implement 4-degrees-of-freedom (4-DOF) underwater motion while saving energy. Because each thruster provided 2-DOF motion, three were sufficient for 4-DOF motion. Therefore, the propulsion system was composed of three vectored water-jet thrusters mounted on an equilateral triangular support. A master–slave structure was employed for the electrical design to realize data collection and motion control. The master side was used for the sensor data collection and control algorithm, and the slave side was used to control the propulsion system. After examining the performance of a first-generation electrical system, we chose a more powerful master processor to allow for a more complicated control algorithm. A microelectromechanical system (MEMS) inertial measurement unit replaced the original gyroscope to collect the attitude angle for the three axes. A Kalman filter was used to calibrate the data output and reduce the noise of the MEMS sensor. A series of underwater motion experiments were carried out to test the performance of the spherical underwater robot; these included surge motion, yaw motion, depth control, and multiple-depth control tests. A proportional–derivative (PD) controller was used to control the direction of the vectored water-jet thrusters for underwater motion. The experimental results demonstrated that the spherical underwater robot could realize underwater motion by controlling the direction of the thrusters. However, the robot was not very stable because the change in the propulsive force was nonlinear.

Preliminary concept and kinematics simulation of a novel Spherical Underwater Robot

This paper describes the preliminary concept of a novel Spherical Underwater Robot. The novel SUR employs a spherical hull and equipped with multiple vectored water-jet-based thrusters. This paper focuses on the preliminary design of the structure and the simulation of the robots dynamics and kinematics. On the basis of the structural characteristics of the spherical robot, its dynamic model is derived by applying the Lagrange-Routh equations briefly. The simulation model is established based on ADAMS2007 software. A 3D model of robot is built by CATIA and then exported to ADAMS2007 for simulation. The results of simulation by combining MATLAB/ SIMULINK with ADAMS are presented. The dynamic analysis and simulation are given to verify the validity of this design. The simulation results indicate that the proposed virtual prototype system has the capability of simulative demonstration and performance validation, and can provide an innovative approach for AUV graphic simulation.

Characteristics evaluation of the vertical motion of a spherical underwater robot

This paper evaluated the vertical movement characteristics of a spherical underwater robot. Firstly, the vectored water-jet propulsion system was employed to realize vertical motion. In order to facilitate the estimation of robot parameters, some simplification were proposed to estimate robot parameters based on its structure features. And then, the vertical control parameters had been calculated to achieve a high accuracy on vertical movements. In addition, the pressure sensor was used into the closed-loop control system. Finally, some experiments had been carried out to verify the result of parameter calculation and the performance of the proposed vertical control system.

Adaptive fuzzy sliding mode control for spherical underwater robots

An adaptive fuzzy sliding mode controller is proposed to deal with the depth and heading regulation of spherical underwater robots. The performance of the proposed controller is investigated in simulation. The controller can realize a better control of the spherical underwater robots. Furthermore, the designed controller can not only tolerate actuator stuck faults, but also compensate the disturbances with constant components. Also, the controller is easy for engineering realization. The controller is not specific to such a system and is applicable to a reasonably wide class of engineering systems which can, at least in an operating region of interest, be adequately represented.

Characteristic evaluation of a wireless capsule microrobotic system

In this paper, we proposed a wireless capsule microrobotic system. The wireless capsule microrobotic system consists of a 3-axes Helmholtz coils and a wireless capsule microrobot. The wireless capsule microrobot is composed of a spiral outer shell and an o-ring type magnet. The length of wireless capsule microrobot is 20 mm and the width is 8 mm. The structure of wireless capsule microrobot is simple. The robot can suitable for multiple working environments with good stability. Total, the wireless capsule microrobot realizes multiple degrees of freedom motion by changing the current of the rotational magnetic field. Based on motion experiments, the main parameters are evaluated. The experimental results show that the wireless capsule microrobot of spiral motion has a maximum speed of 10.01 mm/s at 17 Hz in the horizontal plane and a maximum speed of 3.64 mm/s at 14 Hz in the vertical plane. The wireless capsule microrobot can turn around 90o and achieves accelerated motion, retarded motion and stopping in the three-dimensional space.