This paper presents the design and construction of a biomimetic swimming robot inspired by the locomotion of rays. These fishes move by flapping their pectoral fins and creating a wave that moves in the opposite direction to the direction of motion, pushing the water back and giving the fish a propulsive force due to momentum conservation. While this motion is similar to other fishes in terms of efficiency, it gives better maneuverability and agility in turning. The robot's fins are molded from silicone rubber and moved by servo motors driving mechanisms inside the leading edge of each fin. The traveling wave, mimicking the movement of the fin, is passively generated by the flexibility of the material. The robot is also equipped with a tail that acts as a rudder, helpful in performing maneuvers and maintaining the desired attitude. The rigid central body of the robot is the housing for motors, electronics, and batteries. Sensors embedded in the robot allow to estimate its behavior, to compare different swimming strategies, and evaluate the best algorithm to control the robot.
This paper presents the design and realization of a bioinspired snake robot that can move on the water surface. This robot mimics the locomotion strategies of anguilliform fishes such as eels and lampreys, which have a thin, long, cylindrical body and whose movement resembles the crawling of a snake. An autonomous underwater vehicle with such a shape can pass through narrow crevices and reach places inaccessible to other swimming robots. Moreover, this locomotion entails a high energy efficiency and outstanding agility in maneuvers. The body of the bioinspired robot consists of a modular structure in which each module contains a battery, the electronic board, and a servo motor that drives the following module. The head of the robot has a different shape as it contains a camera and an ultrasonic sensor used to detect obstacles. In addition to the design of the robot, this paper also describes the implementation of the kinematic model.
This paper presents the design and construction of a biomimetic swimming robot inspired by the locomotion of rays. These fishes move by flapping their pectoral fins and creating a wave that moves in the opposite direction to the direction of motion, pushing the water back and giving the fish a propulsive force due to momentum conservation. The robot’s fins are molded from silicone rubber and moved by a servo motor that drives a mechanism inside the leading edge of each fin. The traveling wave, mimicking the movement of the fin, is passively generated by the flexibility of the rubber itself. The robot is also equipped with a tail that acts as a rudder, helpful in performing maneuvers. The rigid central body of the robot is the housing for motors, electronics, and batteries.
Fish swimming is a promising source of inspiration for novel and efficient propulsion mechanisms for autonomous underwater vehicles, as fishes swim with excellent energy efficiency and high maneuverability. Among the locomotion strategies of aquatic animals, the swimming mode of batoids is one of the most interesting, as these fishes swim with high energy efficiency, and they are capable of performing maneuvers with great agility. These advantages are mainly due to the fin geometry and the kinematics of their movement. The fish develops a traveling wave from the leading edge to the trailing edge of the fin, the amplitude of which increases towards the tip of the fin. This wave pushes the water backward, giving the fish a forward thrust due to momentum conservation. The motion of the fin of a cownose ray has been studied, and a biomimetic swimming robot inspired by the cownose ray has been designed and realized. Each fin is made of silicone sheets, and it is moved by three mechanisms whose kinematics replicate the fin deformation. Each mechanism is driven by an independent servomotor, creating a traveling wave on the fin whose frequency, wavelength, and amplitude can be modulated. The motors, battery, and electronics are housed in the central body of the robot, which is rigid. This paper describes the robot’s design and construction.
Roots are extraordinary diggers because they penetrate the soil adding new material on their tip without moving the already grown part, preventing friction from dissipating too much energy and minimising inertial forces during motion. A robot exploiting this principle can assist operations of search and rescue digging in mud or snow to find people in danger. In this work a soft pneumatic robot inspired to roots’ growth is presented. The body of the robot consists of a cylindric plastic membrane folded inside out; one extremity is kept fixed to the base, whereas the other one is folded inside itself. When air is blown from the base, the body of the robot is inflated, and its tip is everted increasing its length. Inside the tip a head is mounted, where the mechanism controlling the direction of growth is placed. On the external surface of the membrane some hooks are mounted, and tensioned wires connects them longitudinally while they are folded before being everted. These wires are cut when they pass next to the head allowing the robot to unfold; since series of hooks are distributed radially on the body of the robot, the direction of growth is controlled by selecting which wires are to be cut. On the head of the robot can be mounted an infrared sensor or a video-camera needed for the specific application.
One field in which nature outperforms current technology is fish swimming, because its efficiency, manoeuvrability and noise are far better than those of typical ship propellers. These advantages are not only due to the streamlined shape and the low-drag skin, but also and above all to the propulsion mechanism, which makes thrust generation possible with small energy dissipation in vortices. Nowadays the interest in autonomous underwater vehicles is in constant increase following the emerging needs of underwater mining and fish farming. Batoid fishes produce thrust with their pectoral fins, they essentially produce a wave travelling in the direction opposite to their motion, pushing water backwards and gaining thrust as a consequence of momentum conservation. The motion of the fin has been studied and reproduced with a series of articulated mechanisms. In this work the optimization of the mechanism’s geometry is described and the experimental results on the reconstructed fin are presented. Moreover, a bioinspired robot mimicking cownose ray locomotion has been designed and built. In this paper the functioning of this robot is shown.
Among all aquatic species, mantas and rays swim by oscillating their pectoral fins; this motion is similar to other fishes in term of efficiency, but it gives better agility in turning with respect to fishes moving their caudal fin. The fin motion is featured by a travelling wave going opposite to the forward motion, producing a force thanks to momentum conservation. Another contribution to the generation of thrust is given by the generation of a vortex in correspondence of the leading edge of the fin, which pulls the fish forward thanks to the lower pressure in its centre. In literature these contributions have been highlighted, but it remains to understand which one of these two mechanisms is prevailing according to different conditions of swimming, how they affect each other and what is the influence of the two on energetical efficiency. The object of this activity is to investigate how thrust generation is influenced by geometrical characteristics of the fin, such as size, geometry and flexibility and by parameters of motion, such as speed, amplitude and frequency of fin oscillation and velocity of the travelling wave. A CFD model of the fish has been implemented in OpenFOAM, not only confirming that both upstroke and downstroke contribute positively to the forward movement according to the momentum conservation principle, but also highlighting the formation of a leading-edge vortex enhancing thrust generation. The description of how thrust generation is linked to motion parameters is simulated also coupling the CFD with a multibody to simulate the whole motion in its complexity.
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