Maoxun Li

Design and performance evaluation of an amphibious spherical robot

This paper presents an amphibious spherical robot that consists of a sealed upper hemispheroid, two quarter spherical shells, and a plastic circular plate. It has a plastic shelf for carrying the micro-robots, and four actuating units for movement. Each unit is composed of a water-jet propeller and two servomotors, each of which can rotate 90? in the horizontal and vertical directions. The robot is capable of motion on land, as well as underwater. The robot is capable of three walking gaits; therefore, we describe experiments on various terrains to evaluate the walking motion performance, including stability and velocity. Additionally, plenty of underwater experiments are conducted to evaluate the underwater performance, containing horizontal and vertical motions, and to verify the fixture and deployment mechanism for the micro-robot. We describe an amphibious spherical robot, which is capable of motion on land, as well as underwater.The amphibious robot has two actuation systems: a quadruped walking actuation system and a water-jet actuation system.The amphibious robot can move with a relatively high velocity and for a relatively long period of time on land and underwater.The amphibious robot can carry the micro-robot, which is used as a manipulator underwater.

A Novel Soft Biomimetic Microrobot with Two Motion Attitudes

A variety of microrobots have commonly been used in the fields of biomedical engineering and underwater operations during the last few years. Thanks to their compact structure, low driving power, and simple control systems, microrobots can complete a variety of underwater tasks, even in limited spaces. To accomplish our objectives, we previously designed several bio-inspired underwater microrobots with compact structure, flexibility, and multi-functionality, using ionic polymer metal composite (IPMC) actuators. To implement high-position precision for IPMC legs, in the present research, we proposed an electromechanical model of an IPMC actuator and analysed the deformation and actuating force of an equivalent IPMC cantilever beam, which could be used to design biomimetic legs, fingers, or fins for an underwater microrobot. We then evaluated the tip displacement of an IPMC actuator experimentally. The experimental deflections fit the theoretical values very well when the driving frequency was larger than 1 Hz. To realise the necessary multi-functionality for adapting to complex underwater environments, we introduced a walking biomimetic microrobot with two kinds of motion attitudes: a lying state and a standing state. The microrobot uses eleven IPMC actuators to move and two shape memory alloy (SMA) actuators to change its motion attitude. In the lying state, the microrobot implements stick-insect-inspired walking/rotating motion, fish-like swimming motion, horizontal grasping motion, and floating motion. In the standing state, it implements inchworm-inspired crawling motion in two horizontal directions and grasping motion in the vertical direction. We constructed a prototype of this biomimetic microrobot and evaluated its walking, rotating, and floating speeds experimentally. The experimental results indicated that the robot could attain a maximum walking speed of 3.6 mm/s, a maximum rotational speed of 9°/s, and a maximum floating speed of 7.14 mm/s. Obstacle-avoidance and swimming experiments were also carried out to demonstrate its multi-functionality.

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.

Development of an amphibious mother spherical robot used as the carrier for underwater microrobots

Nowadays, smart materials actuated microrobots are widely used when dealing with complicated missions in limited spaces. But problems still exist in this kind of solutions, such as low locomotion speed and short operating time. To solve these problems, we propose a mother-son multi-robots cooperation system, named GSL system, which included several microrobots as son robots, and a novel designed amphibious spherical robot as the mother robot. The mother robot, called GSLMom, was designed to be able to carry microrobots and provide power supply for them. This paper will talk about the structure and mechanism of the GSLMom robot. The GSLMom robot was designed as an amphibious spherical one. The robot was equipped with a 4 unit locomotion system, and each unit consists of a water-jet propeller and two servo motors. Each servo motor could rotate 90° in horizontal and 120° in vertical direction respectively. When moving in water, servo motors controlled the directions of water jet propellers and the 4 propellers work to actuate the robot. In the ground situation, propellers were used as legs, and servo motors actuated these legs to realize walking mechanism. After discussed structures, experiments were conducted to evaluate performance of the actuators.

Design and kinematic analysis of an amphibious spherical robot

Nowadays, microrobots are being widely researched in order to deal with complicated missions in limited spaces. But important abilities such as locomotion velocity and enduring time are usually sacrificed in order to realize compact sizes. To solve these problems, we proposed a mother-son multi-robots cooperation system, named GSL system, which included several microrobots as son robots, and a novel designed amphibious spherical robot as the mother robot. The mother robot, which was called GSLMom robot, was designed to be able to carry microrobots and provide power supply for them. This paper will mainly focus on the structure and mechanism of the GSLMom robot. The GSLMom robot, which was designed as an amphibious spherical one, was shaped by a fixed hemisphere hull, and two openable quarter ball hulls. The robot was equipped with a 4 unit locomotion system, and each unit consists of a water jet propeller and two servo motors. Each servo motor could rotate 90° in horizontal or vertical direction respectively. When moving in water, servo motors controlled the directions of water jet propellers and the 4 propellers worked to actuate the robot. With this mechanism, the robot could realize moving forward, backward, rotating, floating and sinking motion in water. In the ground situation, propellers were used as legs, and servo motors actuated these legs to realize walking mechanism, so that the robot could realize moving forward, backward, and rotating motions on the ground. After discussed structures, actuating strategies were proposed for the robot. And kinematic models of the robot were also built.

Development of a Lobster-Inspired Underwater Microrobot

Biomimetic underwater microrobots are of great interest for underwater monitoring operations, such as pollution detection and video mapping in restricted underwater environments. Generally speaking, compact structure, multi-functionality, flexibility and precise positioning are considered incompatible characteristics for underwater microrobots. Nevertheless, we have designed several novel types of bio-inspired locomotion, using ionic polymer metal composite (IPMC) and shape memory alloy (SMA) actuators. We reviewed a number of previously developed underwater microrobot prototypes that were constructed to demonstrate the feasibility of these types of biomimetic locomotion. Based on these prototypes, we summarized the implemented techniques and available results for efficient and precise underwater locomotion. In order to combine compact structure, multi-functionality, flexibility and precise positioning, we constructed a prototype of a new lobster-like microrobot and carried out a series of experiments to evaluate its walking, rotating, floating and grasping motions. Diving/surfacing experiments were performed by electrolyzing the water around the surfaces of the actuators. Three proximity sensors were installed on the microrobot to detect an object or avoid an obstacle while walking.

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.

A smart actuator-based underwater microrobot with two motion attitudes

Various microrobots were widely used in the fields of biomedical engineering and underwater operation during the last few years. By having a compact structure, low driving voltage and a simple control system, microrobots could complete a variety of underwater tasks, even in limited spaces. To realize the multifunctionality of the microrobot for adapting to complex underwater environments, we proposed a walking biomimetic microrobot with two kinds of motion attitudes, lying state and standing state. The microrobot used eleven ICPF (ionic conducting polymer film) actuators to move and two SMA (shape memory alloy) actuators to change motion attitude. In the lying state, the microrobot could implement stick insect-inspired walking/rotating motion, fish-like swimming motion, horizontal grasping motion, and floating motion. In the standing state, it could implement inchworm-inspired crawling motion along two directions and vertical grasping motion. Then we developed a prototype of multi-functional biomimetic microrobot and evaluated its walking, rotating and floating speeds experimentally. Experimental results indicated that the robot could obtain a maximal walking speed of 3.6mm/s, a maximal rotating speed of 9deg/s and a maximal floating speed of 7.14mm/s.

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.

Performance evaluation on land of an amphibious spherical mother robot in different terrains

In recent years, a variety of underwater microrobots were applied widely to underwater operations in limited spaces. The robots had some limitations of locomotion velocity and enduring time because of their compact structures. For solving these problems, we proposed a mother-son robot cooperation system and designed a novel amphibious spherical robot as the mother robot to carry the microrobots as son robots for collaboration. The spherical mother robot consisted of a sealed hemispheroid, two openable quarter spherical shells, a plastic circular plate, a plastic shelf for carrying microrobots and four actuating units. Each unit was composed of a water jet propeller and two servo motors, each of which could rotate 90° in horizontal or vertical direction respectively. The robot could implement on-land locomotion, as well as underwater locomotion. In this paper, a prototype spherical mother robot was developed and three walking gaits, decided by the duty factory, were designed for the on-land motion of the robot. Then the walking experiments were carried out in different terrains for evaluating the performance of the robot. From the results, the robot has a higher walking performance on tile floor. Under a control frequency of 3.33 Hz in Gait 3, we got a maximal walking velocity of 22.5 cm/s. For climbing performance, Gait 2 has the best performance on a steep slope with the inclination angle of 8°.