Vincent Lebastard

Model for a Sensor Inspired by Electric Fish

This paper reports the first results from a program of work aimed at developing a swimming robot equipped with electric sense. After having presented the principles of a bioinspired electric sensor that is now working, we will build the models for electrolocation of objects that are suited to this kind of sensor. The produced models are in a compact analytical form in order to be tractable on the onboard computers of the future robot. These models are tested by comparing them with numerical simulations based on the boundary elements method. The results demonstrate the feasibility of the approach and its compatibility with online objects electrolocation, i.e., another parallel program of ours.

Underwater Reflex Navigation in Confined Environment Based on Electric Sense

This paper shows how a sensor inspired by an electric fish could be used to help navigate in confined environments. Exploiting the morphology of the sensor, the physics of electric interactions, as well as taking inspiration from passive electrolocation in real fish, a set of reactive control laws encoding simple behaviors, such as avoiding any electrically contrasted object, or seeking a set of objects while avoiding others according to their electric properties, is proposed. These reflex behaviors are illustrated on simulations and experiments carried out on a setup dedicated to the study of electric sense. The approach does not require a model of the environment and is quite cheap to implement.

Underwater robot navigation around a sphere using electrolocation sense and Kalman filter

The aim of this paper is to perform the navigation of an underwater robot equipped with a sensor using the electric sense. The robot navigates in an unbounded environment in presence of spheres. This sensor is inspired of some species of electric fish. A model of this sensor composed of n spherical electrodes is established. The variations of the current due to the presence of the sphere is related to the model of Rasnow [3]. Unscented Kalman Filter is used to localize the robot with respect to the sphere and to estimate the size of the sphere. We show that bio-inspired motions improve the detection of the spheres. We illustrate the efficiency of the method in two cases: a two electrodes sensor and a four electrodes sensor.

Environment reconstruction and navigation with electric sense based on a Kalman filter

Electric fish sense the perturbations of a self-generated electric field through their electro-receptive skin. This sense allows them to navigate and reconstruct their environment in conditions where vision and sonar cannot work. In this article, we use a sensor inspired by this sense to address both problems of locating and estimating the size of small objects (electrolocation) and navigating in a tank. Based on a Kalman filter, any small object in the surroundings of the motion-controlled sensor can be modeled as an equivalent sphere whose location is well estimated by the filter. As a first application to the problem of navigation, the filter is included into a closed feedback loop in order to achieve wall following in a tank. Our experimental results demonstrate the feasibility of this approach.

Underwater navigation based on passive electric sense

In underwater robotics, several homing and docking techniques are currently being investigated. They aim to facilitate the recovery of underwater vehicles, as well as their connection to underwater stations for battery charging and data exchange. Developing reliable underwater docking strategies is a critical issue especially in murky water and/or in confined and cluttered environments. Commonly used underwater sensors such as sonar and camera can fail under these conditions. We show how a bio-inspired sensor could be used to help guide an underwater robot during a docking phase. The sensor is inspired by the passive electro-location ability of electric fish. Exploiting the electric interactions and the morphology of the vehicle, a sensor-based reactive control law is proposed. It allows the guidance of the robot toward the docking station by following an exogenous electric field generated by a set of electrodes fixed to the environment. This is achieved while avoiding insulating perturbative objects. This control strategy is theoretically analysed and validated with experiments carried out on a setup dedicated to the study of electric sense. Though promising, these results are but a first step towards the implementation of an approach to docking in more realistic conditions, such as in turbid salt water or in the presence of conductive perturbative objects.

Electrolocation Sensors in Conducting Water Bio-Inspired by Electric Fish

This article presents the first research into designing an active sensor inspired by electric fish. It is notable for its potential for robotics underwater navigation and exploration tasks in conditions where vision and sonar would meet difficulty. It could also be used as a complementary omnidirectional, short range sense to vision and sonar. Combined with a well defined engine geometry, this sensor can be modeled analytically. In this article, we focus on a particular measurement mode where one electrode of the sensor acts as a current emitter and the others as current receivers. In spite of the high sensitivity required by electric sense, the first results show that we can obtain a detection range of the order of the sensor length, which suggests that this sensor principle can be used for robotics obstacle avoidance as it is illustrated at the end of the article.

Multi-physics model of an electric fish-like robot: Numerical aspects and application to obstacle avoidance

The paper deals with the modeling of a fish-like robot equipped with the electric sense, suited to study sensorimotor loops. The proposed multi-physics model merges a swimming dynamic model of a fish-like robot with an electric model of an embedded electrolocation sensor. Based on a TCP-IP and threaded framework, the resulting simulator works in real time. After presenting the modeling aspects of this work, this article focuses on two numerical studies. In the first, the interactions between body deformations and perception variables are studied and a current correction process is proposed. In the second study, an electric exteroceptive feedback loop based on a direct current measurement method is designed and tested for obstacle avoidance.

Estimation of Absolute Orientation for a Bipedal Robot: Experimental Results

This paper deals with a planar biped. The aim of this paper is the estimation, during the imbalance phases of a walking cyclic gait, of its absolute orientation by only using the measurement of the actuated joint variables. The main contribution is the experimental evaluation of an original finite-time convergent-posture observer.

Underwater electro-navigation in the dark

This article proposes a solution to the problem of the navigation of underwater robots in confined unstructured environments wetted by turbid waters. The solution is based on a new sensor bio-inspired from electric fish. Exploiting the morphology of the sensor as well as taking inspiration from passive electro-location in real fish, the solution turns out to be a sensory-motor loop encoding a simple behavior relevant to exploration missions. This behavior consists in seeking conductive objects while avoiding insulating ones. The solution is illustrated on experiments. It is robust and works even in very unstructured scenes. It does not require any model and is quite cheap to implement.

An underwater reconfigurable robot with bioinspired electric sense

Morphology, perception and locomotion are three key features highly inter-dependent in robotics. This paper gives an overview of an underwater modular robotic platform equipped with a bio-inspired electric sense. The platform is reconfigurable in the sense that it can split into independent rigid modules and vice-versa. Composed of 9 modules, the longer entity can swim like an eel over long distances, while once detached, each of its modules is efficient for small displacements with a high accuracy. Challenges are to mechanically ensure the morphology changes and to do it automatically. Electric sense is used to guide the modules during docking phases and to navigate in unknown scenes. Several aspects of the design of the robot are described and a particular attention is paid to the inter-module docking system. The feasibility of the design is assessed through experiments.