Yueri Cai

Design and Experiments of a Robotic Fish Imitating Cow-Nosed Ray

The cow-nosed ray is studied as natural sample of a flapping-foil robotic fish. Body structure, motion discipline, and dynamic foil deformation of cow-nosed ray are analyzed. Based on the analysis results, a robotic fish imitating cow-nosed ray, named Robo-ray II, mainly composed of soft body, flexible ribs and pneumatic artificial muscles, is developed. Structure and swimming morphology of the robotic prototype are as that of a normal cow-nosed ray in nature. Key propulsion parameters of Robo-ray II at normal conditions, including the St Number at linear swimming, thrust coefficient at towing are studied through experiments. The suitable driving parameters are confirmed considering the efficiency and swimming velocity. Swimming velocity of 0.16 m·s−1 and thrust coefficient of 0.56 in maximum are achieved in experiments.

Design of a robotic fish propelled by oscillating flexible pectoral foils

This paper proposed a new method of designing a flexible biomimetic fish propelled by oscillating flexible pectoral fins. The molding soft body is adopted in the robotic fish. Pneumatic artificial muscles are utilized as driving sources and two ribs with distributed flexibility as main parts of the propulsive mechanism. The leading edge locomotion profile of the flexible pectoral fin in air is studied experimentally, and the flapping locomotion in water is observed too. Finally, the effectiveness of the proposed method is illustrated by the experiment. It shows that the robotic fish can realize self-driven, and it can swim at a speed of 0.18m/s∼0.20m/s after optimization.

Design Optimization of a Bionic Fish with Multi-Joint Fin Rays

This paper aims to design a novel bionic fish propelled by oscillating paired pectoral fins. Flapping motion deformation of the nature sample, the cow-nosed ray, is realized with simple mechanical structure through optimization. Locomotion analysis of the nature sample under linear cruise swimming conditions is carried out. Simplified mathematical models of the pectoral fin are obtained to be the design foundation of the bionic fin rays and the bionic fish. The number of fin rays is decided according to the passing kinematic wave shape and number. Distance and structure parameters are optimized, and determined by the minimum area error method. A novel two-stage slide–rocker mechanism is designed to fulfill the driving requirements with only one servo motor. System design of a new bionic fish robot is presented, including the mechanical design and the control method. Main bionic characteristics extracted from the cow-nosed ray are fulfilled by the prototype and verified by experiments.

Design and optimization of a robotic fish mimicking cow-nosed ray

The paper is aimed at establishing a platform of robotic fish propelled by paired pectoral fins, so as to research pectoral fin propulsion. Locomotion of nature sample, cow-nosed ray, was analyzed before simplified mathematical model was obtained for design of the robotic fish. Locomotion of the pectoral fins is equivalent to the pass of oscillating motion from front to back in the form of cubic function in one plane. Tridimensional flexible skin was made according to the shape of cow-nosed ray. Mechanism with three fin rays was designed to meet the mathematical model, that is, to mimic the pass of locomotion wave on pectoral fin. A novel two stage rocker-slide mechanism was designed, which can drive the flexible skin to realize the ideal profile approximately with only one motor. In order to mimic the locomotion better, key dimension parameters were optimized based on the mathematical model of locomotion. Primary experiment was done for the two stage rocker-slide mechanism, which showed the design was valid.

Development and depth control of a robotic fish mimicking cownose ray

A robotic fish mimicking cownose ray is developed and a fuzzy depth control method is presented in this paper. With dosoventrally flattened body wich is disigned by imitating body shape of cownose ray, the robotic fish has preferable pitch stability. A tail-unit, which consists of a pair of horizontal tails and a vertical tail, is used to realize turning motion in the horizontal plane and up-and-down motion in the vertical plane. By adjusting rotation angles of the horizontal tail, the robotic fish can swim upward or downward. Due to the complex hydrodynamics and uncertaintyies exist in the environment, fuzzy logic method is applied to realize automatic depth control of the robotic fish. The experimental results on the prototype verify that the fuzzy logic depth control method is effective in design and implemention.

Posture analysis and application of a bionic pectoral foil

Biological fish propelled by wide paired pectoral foils is attractive for the special characteristics as their nature samples. Advantages and limitations of two groups of the bionic flatten pectoral foils classified by actuation arrangement are summarized. Key flapping properties of cow-nosed ray affecting its driving performance are obtained. Simplified driving method and typical theoretical postures for the designed bionic wide pectoral foil is analyzed and verified through experiments. A bionic fish based on this kind of foil has been developed and tested in air and water. Various postures designed imitating cow-nosed ray in air have also been verified. Furthermore, the swimming performance tests in water show that the bionic fish can achieve maximum forward swim speed of 0.7 times of body length per second and an excellent turning maneuverability with a small radius.

A biomimetic cownose ray robot fish with oscillating and chordwise twisting flexible pectoral fins

Purpose The paper aims to develop a cownose ray-inspired robotic fish which can be propelled by oscillating and chordwise twisting pectoral fins. Design/methodology/approach The bionic pectoral fin which can simultaneously realize the combination of oscillating motion and chordwise twisting motion is designed based on analyzing the movement of cownose ray’s pectoral fins. The structural design and control system construction of the robotic fish are presented. Finally, a series of swimming experiments are carried out to verify the effectiveness of the design for the bionic pectoral fin. Findings The experimental results show that the deformation of the bionic pectoral fin can be well close to that of the cownose ray’s. The bionic pectoral fin can produce effective angle of attack, and the thrust generated can propel robotic fish effectively. Furthermore, the tests of swimming performance in the water tank show that the robotic fish can achieve a maximum forward speed of 0.43 m/s (0.94 times of body length per second) and an excellent turning maneuverability with a small radius. Originality/value The oscillating and pitching motion can be obtained simultaneously by the active control of chordwise twisting motion of the bionic pectoral fin, which can better imitate the movement of cownose ray’s pectoral fin. The designed bionic pectoral fin can provide an experimental platform for further study of the effect of the spanwise and chordwise flexibility on propulsion performance.

Improvement and testing of a robotic manta ray (RoMan-III)

Manta Ray generates thrust force by flapping two pectoral fins, which inspires the parametric study of the fin that affects the swimming performance. In this paper, the design of a robotic manta ray (RoMan-III) will be presented. A biomimetic flapping fin model will be discussed. The forward flapping motion, turning and gliding motions are considered in the study of Manta Rays locomotion. Parameters related to thrust generation include the fin flapping amplitude, frequency, fin area, and fin shape. The fin model is derived based on a simplified model by Bernoulli equation. A scheme of motion control is also suggested for the fish locomotion. Experimental results have been obtained to demonstrate the validity of the proposed model.

Design and implication of a bionic pectoral fin imitating cow-nosed ray

Pectoral foil structure and motion discipline of cow-nosed ray as nature prototype is analyzed. A bionic pectoral fin is designed according to the analysis results. Propulsion performance of the bionic fin at sinusoidal motion law is studied experimentally on a towing platform, at the oscillating frequency from 0.2 Hz to 2 Hz and amplitude from 2.5° to 30°. Well driving ability is obtained, and maximal average thrust of 2.75N is achieved by a single bionic fin expressed at towing speed of 10 cm/s. A biomimetic fish utilizing the kind of bionic fin is developed, and swimming speed of 0.9BL (body length) in maximum can be reached.

Design and motion analysis of tetrahedral rolling robot

A novel robot mechanism-tetrahedral rolling robot is introduced in the paper. The robot comprises of six extension struts and four node flats. When the COG of tetrahedron exceeds the stability region, the robot will roll. The structure of the tetrahedral rolling robot is described. Designing method of the robot is given, and it is proved correct and feasible through experiment. Kinematic model in different motion phase is analyzed in the paper, and the rolling critical condition is formulated. The effectiveness of the method is testified through simulation. The study of the paper will provide important reference for the dynamic analysis, optimization design and control of the tetrahedral rolling robot.