Abstract Efficient propulsion has been a central focus of research in the field biomimetic underwater vehicles. Compared to prevalent fish-like reciprocating flapping mode, sperm-like helical mode features higher efficiency and superior performance high-viscosity environments. Based on previously developed sperm-inspired robot, this paper focuses its dynamic modeling depth control research. The robot is analyzed by resistance-theory-based force analysis, followed application Kirchhoff rod...

Fish tunes fishtail stiffness by coordinating its tendons, muscles, and other tissues to improve swimming performance. For robotic fish, achieving a fast online fishlike adjustment over large-scale range is of great significance for performance improvement. This article proposes an elastic-spine-based variable which adopts spring steel emulate the fish spine, adjusted tuning effective length elastic spine. The can be switched in maximum adjustable within 0.26 s. To optimize motion adjusting...

Undulation regulation in a robotic fish propelled by passive flexible tail is more similar to that of natural than with rigid tail, owing the smooth curvature tail. Moreover, it has been observed change stiffness their bodies adapt various swimming states. Inspired this, optimization scheme explored for novel elastic which can improve performance fish. Spring steels are used as joints fishtail; these be easily expanded into multi-joint structures and joint altered changing size. In this...

The complex and continuous undulation of fishtail facilitates extraordinary underwater motion performance for natural fish. For the widely used Multi-Joint robotic fish, a lot joints are to simulate continuum fishtail, resulting in some challenges, e.g., mechanism complexity, friction losses adjacent joints, load disequilibrium unsmooth servomotor output power. To overcome these intractable hurdles, motivated by this letter proposes wire-driven elastic which simulates fish muscle through...

The extraordinary swimming performance of fish benefits from the complex motion continuum fishtail, which is difficult for robotic to replicate. common approach adopting a large number discrete joints, introduces some challenges, e.g., redundant degrees freedom, friction loss adjacent etc. Hence, this article presents equipped with wire-driven dual elastic fishtail energy storing and passive flexibility. This consists an active flexible joint, both periodically store due deformation,...

This paper proposes a modeling method for robotic fish with elastic tail, which is driven by motor in head and uses spring steel sheet as passive flexible joint, followed rigid caudal fin. The pseudo-rigid-body model (PRBM) firstly used to analyze the then fluid force acting on divided into pressure links cross-sectional resistance. Further, dynamic established Lagrangian solve movement of fish. And utilized investigate influence joint stiffness propulsion performance. For different...

The robotic fish with high propulsion efficiency and good maneuverability achieves underwater fishlike by commonly adopting the motor to drive fishtail, causing significant fluctuations of power due uneven swing speed fishtail in one cycle. Hence, we propose a wire-driven spring-steel-based active-segment elastic spine. This bionic spine can produce deformation store energy under action wire driving for responding power. Further, analyze effects energy-storing on smoothness Based developed...

The high speed and low energy cost are two conflicting objectives in the motion optimization of bio-inspired underwater robots, but playing a very important role. To this end, paper proposes an strategy for swimming power using improved NSGA-II flexible robotic fish. A dynamic model involving deformation is established prediction with hydrodynamic parameters identified. back propagation (BP) neural network applied to perform compensation model's as input. In particular, NSGA-II-AMS method...

The development of biomimetics and the demand for higher propulsion efficiency lead to more research in helical robots. This letter presents a novel sperm-inspired robot that utilizes flexible tail as analyzes motion performance. Firstly, robot's system is center-fixed rotation mechanism can accurately mimic sperm tail. Secondly, based on resistance theory Kirchhoff's rod theory, dynamic model established analyse propulsive More importantly, it found be divided into two models: roll spin,...

This paper presents a novel wire-driven fish tail with two joints, using spring-steel-sheet to mimic spine, which makes the whole compliant and can simulate real better. mechanism also achieve C-shape S-shape swing similar natural tail. To predict attitude of tail, kinematics model is established theoretically in this paper. The simulation experiments show that maximum error between amplitude predicted by expected at end 5 mm, indicating correctness proposed model. In order solve control...

In an experimental environment with limited conditions, it is always hard to achieve precise positioning of robotic fish. A combined indoor self-positioning method in this paper introduced solve the problem. For short-distance range, coordinates are calculated by fusing measured distances and angles. medium-distance a clustering-grid supervision (CGS) algorithm proposed adopted correct obtained four-point method. An ostracion-like fish used as object centimeter-level average error 4.492 cm...

Accurate localization of robots in a specific environment often requires the cooperation multiple sensors, and how to establish more general data fusion model is always difficult problem. For robot fish an indoor pool environment, this paper proposes adaptive fusional algorithm based on fuzzy inference dynamic weights. This firstly constructs confidence probability table sensors' signals calibration sets BLE UWB nodes at different distances, as basis for updating weights or nodes; secondly,...