Desert ant navigation - a model for robotics?
Field research on Cataglyphis fortis
Step length Foraging desert ants, Cataglyphis fortis, are able to navigate without using external cues such as visual landmarks or odor-trails. Instead they perform path integration by constantly calculating the location of the nest in terms of distance and direction. In order to do so, they monitor direction, distance and inclination of each single path segment. While direction is determined by skylight cues, distance is measured by employing some kind of step counter.
The project I was part of aimed at unravelling the mechanisms that lie behind three-dimensional navigation. Therefore I performed kinematic analyses of the ants’ locomotion at different inclinations in order to elucidate the responsible mechanisms for distance estimation and inclinometry.
Surface roughness A further issue lies in characterizing the robustness of the path-integration system. I performed behavioral experiments in which the ants were confronted with surfaces of different degrees of roughness causing the ants to increase slip rate during locomotion. However, as long as the ants were able to employ a rhythmic pattern of locomotion, the system could successfully compensate for errors.
Perception of propulsion So far we have not been able to understand how the ant gets informed about the resulting propulsion of a stepping attempt. In this respect the following experiment might provide a stepping stone to answer this question: Ants are able to monitor the roughness of the surface on which they run. In the actual experiment I showed that they exploit this information as an orientational cue during their nest search behavior. But it might well be that the tactile senses not only monitor roughness but are also able to record events of foot-surface slipping, which are thenintegrated into the step counter.
Perception of barriers The visual perception of horizontal barriers in the frontal field of view of Cataglyphis was observed during other experiments. Although it was previously assumed that barriers within the frontal field of view of Cataglyphis are exclusively perceived through tactile assessment via the antennae. The high-speed recordings show clearly, that both visual and tactile mechanisms work, but the tactile ones happen at a later stage and are only used when the ants are deprived of visual input, e.g. when the upper hemisphere of their eyes are covered.
Can we learn for robotic odometry?
Navigation is an important part of exploring new uncharted areas. For rovers moving on legs instead of wheels this task is more complex. In this project we are looking for a way to navigate by mimicing the ants way of proprioceptive sensoring.
Current planetary surface exploration rovers' navigation techniques mainly focus on the visual stimulants. Typical visual navigation components (e.g. CCD-camera) are bulky and real-life tracking algorithms heavy on the processor unit.
In this project, we are trying to implement our knowledge of ants into robotics. The way ants and some other insects count their steps and measure the strain in their campaniform sensilla to navigate through the terrain. We want to come up with an navigation system that is not requiring a lot of processing power or space and is precise enough to keep track of our rovers.
As part of my work at ESA's Advanced Concepts Team we evaluated the evaluated the potential for force mediated odometry in legged robots. (
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Neuromorphic approaches to planetary landing
Neuronal systems are nothing else that animal controlers. Although the same physics apply, computation is performed funamentally different to known controlers. Here we investigate neuromorphic sensors and controlers.
Neuronal systems process visual cues using analog electronics.
Autonomous landing on unknown extraterrestrial bodies requires fast, noise-resistant motion processing to elicit appropriate steering commands. Flying insects excellently master visual motion sensing techniques to cope with highly parallel data at a low energy cost, using dedicated motion processing circuits. Results obtained in neurophysiological, behavioural, and biorobotic studies on insect flight control were used to safely land a spacecraft on the Moon in a simulated environment.
ESA’s Advanced Concepts Team has identified autonomous lunar landing as a relevant situation for testing the potential applications of innovative bio-inspired visual guidance systems to space missions. Biomimetic optic flow-based strategies for controlling automatic landing were tested in a very realistic simulated Moon environment. Visual information was provided using the PANGU software program and used to regulate the optic flow generated during the landing of a two degrees of freedom spacecraft. The results of the simulation showed that a single elementary motion detector coupled to a regulator robustly controlled the autonomous descent and the approach of the simulated moonlander. “Low gate” located approximately 10 m above the ground was reached with acceptable vertical and horizontal speeds of 4 m/s and 5 m/s, respectively. It was also established that optic flow sensing methods can be used successfully to cope with temporary sensor blinding and poor lighting conditions.
Parallel studies
This project is conducted in two parallal studies, one by the Biorobotics group of the University of Marseille, one by the Institute of Neuroinformatics, University and ETH Zurich.
Cockroaches - landing in safe mode?
Cockroaches fly only during escape reactions and specific adaption to that lifestyle are expected. Landing strategies and transitional phases during aerial descent are examined to drawn inspiration for the design of robust controlers for planetary landing.
Behavioural studies
Cockroaches – however capable of flight they are – are largely ground-dwelling insects and one can assume that flight will always be a non-preferred form of locomotion. Specific adaptations are expected to be present, allowing for optimized landing strategies and transitional phases between aerial descent and terrestrial locomotion. Although the flight apparatus is developed in most representatives, little is known of both flight abilities and aerial performance in cockroaches.
In order to validate the potential arising for future technical applications in unmanned planetary exploration, a first step toward understanding aerial performance in cockroaches was undertaken. Flight experiments were performed on individuals of Blaptica dubia, which were launched from a ramp in 2:5 m height. Three-dimensional video sequences of B. dubia were recorded for whole flight trajectories and additionally starting and landing phases were analysed using high-speed video equipment. Decisional strategies in cockroach flight were mapped as ehtogramms.
Free Flight experiments showed that male specimens of B. dubia are capable of stabilizing their aerial descent by attaining a dorso-ventral righted position and deploying their wings. The descent process mainly consists of 3 distinct phases: a ballistic phase, a body righting and wing deployment phase and a stabilized flight and landing phase. Female B. dubia only display a ballistic fall.
The aerial descent in male B. dubia seems to be controlled and directed as in other wingless arthropods as well as vertebrates. As however no highly specialized transitional phases or landing precautions were observed, it remains unclear whether or not cockroaches are appropriate model organisms for a biomimetic approach to landing control in unmanned planetary exploration.
