This paper presents for the first time the embedded stand-alone version of the bio-inspired M2APix (Michaelis-Menten auto-adaptive pixels) sensor as a ventral optic flow sensor to endow glider-type unmanned aerial vehicles with autonomous landing ability. Assuming the aircraft is equiped with any reliable speed measurement system such as a global positionning system or an inertial measurement unit, we can use the velocity of the glider to determine with high precision its height while landing. This information is robust to different outdoor lighting conditions and over different kinds of textured ground, a crucial property to control the landing phase of the aircraft.

To avoid crashing onto the floor, a free falling fly needs to trigger its wingbeats quickly and control the orientation of its thrust accurately and swiftly to stabilize its pitch and hence its speed. Behavioural data have suggested that the vertical optic flow produced by the fall and crossing the visual field plays a key role in this anti-crash response. Free fall behavior analyses have also suggested that flying insect may not rely on graviception to stabilize their flight. Based on these two assumptions, we have developed a model which accounts for hoverflies´ position and pitch orientation recorded in 3D with a fast stereo camera during experimental free falls. Our dynamic model shows that optic flow-based control combined with closed-loop control of the pitch suffice to stabilize the flight properly. In addition, our model sheds a new light on the visual-based feedback control of fly´s pitch, lift and thrust. Since graviceptive cues are possibly not used by flying insects, the use of a vertical reference to control the pitch is discussed, based on the results obtained on a complete dynamic model of a virtual fly falling in a textured corridor. This model would provide a useful tool for understanding more clearly how insects may or not estimate their absolute attitude.

In an outdoor autonomous navigational context, classic compass sensors such as magnetometers have to deal with unpredictable magnetic disturbances. In this paper, we propose to get inspiration from the insect navigational abilities to design a celestial compass based on linear polarization of ultraviolet (UV) skylight. To compute the solar meridian relative orientation, our 3D-printed celestial compass uses only two pixels created by two UV-light photo-sensors topped with linear polarizers arranged orthogonally to each other, in the same manner that was observed in insects' Dorsal Rim Area ommatidia. The compass was then embedded on our hexapod walking robot called Hexabot. We first tested the UV-polarized light compass to compensate for yaw random disturbances. We then used the compass to maintain Hexabot's heading direction constant in a straight-forward task, knowing the robot has important yaw drifts. Experiments under various meteorological conditions provided steady state heading direction errors from 0.3° under clear sky conditions to 1.9° under overcast sky, which suggests interesting precision and reliability to make this optical compass suitable for robotics.

This paper presents a new minimalist bio-inspired artificial eye of only 24 pixels, able to locate accurately a target placed in its small field of view (±10°). The eye is mounted on a very light custom-made gimbal system which makes the eye able to track faithfully a moving target. We have shown, that our gimbal eye can be embedded on a small quadrotor to achieve accurate hovering with respect to a target placed onto the ground. Our aiborne eye was enhanced with a bio-inspired reflex in charge of locking efficiently the robot's gaze onto a target and compensate for the robot's rotations and disturbances. The use of very few pixels allowed to implement a visual processing algorithm at a refresh rate of 400 Hz. This high refresh rate coupled to a very fast control of the eye's orientation allowed the robot to track a target moving at a speed up to 200° · s-1.

Here we present an example of a novel bio-inspired active vision system with a vibrating eye that can rotate freely by means of a miniature rotary piezo motor. Active micro-vibrations were applied to the eye by using an innovative micro-mechanism based on a tiny stepper motor. The hyperacuity of this inexpensive position-sensing device, which results from the active micro-vibrations, makes it capable of measuring the angular position of a contrasting edge. Among the many miniature rotary actuators available, piezomotors are often used when small size, low mass, great accuracy and high dynamics are required. The newly off-the-shelf miniature ultrasonic piezomotor presented in this study along with its position servo control system is supplied ready-integrated into a printed circuit board (PCB). The PCB Piezomotor (or PCBMotor) has many advantages, such as high torque (it requires no reducer), fast dynamics (the mechanical time constant is 3 ms), a low mass (1 gram) and a compact size (it is only 20 mm in diameter and 2.6 mm thick). The results of the tests conducted show that the performances of the PCBmotor connected to a custom-made miniature electronic driver make it a good alternative to the actuators classically used in robotic applications. In addition we present a simple visual processing, implemented onto a tiny microcontroller, composed of simple linear filtering and arithmetic operations. We show that our visual scanning sensor is a genuine position sensing device able to measure the relative angular position of a visual object with only two pixels and very few computational resources.

Hovering flies are capable of achieving outstanding performances when hovering above flowers for several minutes. A new insect-based hovering control strategy is presented here for accurately stabilizing the position of a sighted twin-rotor equipped with a decoupled eye with a narrow field-of-view of only a few degrees. The main aim of this paper is to describe how accurately hovering flight above a target can be achieved by means of this fundamental bio-inspired mechanical decoupling system between the eye and the body. The simulated gaze control system implemented on-board the aerial robot has several advantages : - it enables the robot's gaze to be stabilized on the basis of three bio-inspired oculomotor reflexes (ORs) : a visual fixation reflex (VFR), a translational reflex and a rotational vestibulo-ocular reflex (tVOR and rVOR), - it makes the eye compensate quickly and accurately for any sudden, untoward disturbances caused by the vagaries of the supporting head or body, - it provides a reference visual signal to compensate for the rate gyro drift used to implement the VORs and to stabilize the hovering robot, - it greatly improves the stability of the robot's roll during voluntary lateral displacements with respect to the target. Close comparisons were made between two simulated robots with and without a decoupled eye, which were both subjected to strong lateral and roll disturbances. The simulations show that the robot with a decoupled eye can reject disturbances twice as fast as that with a fixed eye. This innovative bio-inspired hovering control method stabilizes the robot's attitude without any need for accelerometers, magnetometers or classical inertial measurement units.

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.

OSCAR II is a twin-engine aerial demonstrator equipped with a monocular visual system, which manages to keep its gaze and its heading steadily fixed on a target (i.e., a dark edge or a bar) in spite of the severe random perturbations applied to its body via a ducted fan. The tethered robot stabilizes its gaze on the basis of two oculomotor reflexes (ORs) inspired by studies on animals: 1) a visual-fixation reflex (VFR) and 2) a vestibulo-ocular reflex (VOR). One of the key features of this robot is that the eye is decoupled mechanically from the body about the vertical (i.e., yaw) axis. To meet the conflicting requirements of high accuracy and fast ocular responses, a miniature (2.4 g) voice-coil motor (VCM) was used, which enables the eye to make a change of orientation with an unusually short rise time (19 ms). The robot, which was equipped with a high-bandwidth (7 Hz) ¿VOR,¿ which is based on an inertial microrate gyro, is capable of accurate visual fixation as long as there is light. The robot is also able to pursue a moving target in the presence of erratic gusts of wind. Here, we present the two interdependent control schemes driving the eye in the robot and the robot in space with no knowledge of the robot's angular position. This ¿steering-by-gazing¿ control strategy, which is implemented on this lightweight (100 g) miniature aerial robot, demonstrates the effectiveness of this biomimetic visual/inertial heading control strategy.

Autonomous guidance of micro-air vehicles (MAVs) in unknown environments is a challenging task because these artificial creatures have small aeromechanical time constants, which make them prone to be disturbed by gusts of wind. Flying insects are subject to quite similar kinds of disturbances, yet they navigate swiftly and deftly. Flying insects display high- performance visuo-motor control systems that have stood the test of time. They can therefore teach us how vision can be used for immediate and vital actions. We built a 50-gram tethered aerial demonstrator, called OSCAR II, which manages to keep its gaze steadily fixating a target (a dark edge), in spite of nasty thumps that we deliberately gave to its body with a custom-made "slapping machine". The robot's agile yaw reactions are based on: (1) a mechanical decoupling of the eye from the body, (2) an active coupling of the robot's heading with its gaze, (3) a Visual Fixation Reflex (VFR), (4) a Vestibulo-Ocular Reflex (VOR), (5) an accurate and fast actuator (voice coil motor, VCM). The actuator is a 2.4-gram voice coil motor that is able to rotate the eye with a rise time as small as 12 ms, that is, much shorter than the rise time of human oculo-motor saccades. In connection with a micro-rate gyro, this actuator endows the robot with a high performance "vestibulo ocular reflex" that keeps the gaze locked onto the target whatever perturbations in yaw affect the robot's body. Whenever the robot is destabilized (e.g., by a slap applied on one side), the gaze keeps fixating the target, while being the reference to which the robot's heading is servoed. It then takes the robot only 0.6 s to realign its heading with its gaze.

For any sighted mobile creature, whether it be natural or artificial, stabilizing the visual system is a much more crucial issue than that of preventing a snapshot from being blurred by the unsteadiness of a human photographer. The more immune the eye of an animal or a robot is to various kind of disturbances such as body or head movements of all kinds, the less troublesome it will be for the visual system to carry out its many information processing tasks when walking or flying in unknown environments. The gaze control system that we describe In this work takes a lesson from the vestibulo ocular reflex (VOR) that is known to contribute to the stabilization of the human eyes. The originality and performances of the control system arise from the merging of two sensory modalities: (a) a retinal position signal is yielded by a novel piezo-based visual sensor called OSCAR (optical sensor for the control of autonomous robots); and (b) a VOR reflex is merged with a visual smooth pursuit reflex. Our gaze controller involves a feedforward eye control based on measurements of the angular head speed by a rate gyro. The performances of the gaze controller were tested on-board a miniature (5 grams) oculomotor system, which makes use of the OSCAR visual sensor. The combined visual/inertial sensory-motor controller enables the gaze to be stabilized within a 12-times smaller range than the perturbing head movements, which were applied here at frequencies of up to 3 Hz with an amplitude of 6/spl deg/ peak-to-peak. This is a relatively high standard of performance in terms of rejecting head movement disturbances; in any case, these performances are comparable to those which the human visual system is capable of.

Describes a sensor designed to ensure the non-contact stabilization of a craft and especially to deal with disturbance problems such as those resulting from slow speed angular drift. A low-cost, low-complexity active vision system is described, which is based on the specific eye movements occurring in the compound eye of the fly. In our system, motion is detected and processed by a local motion detector circuit (LMD). First, the rotation of two photosensors at a constant angular speed was simulated, which emphasized motion processing as a useful means of detecting variably contrasted objects, however far ahead they are located. Secondly, we reasoned that if the pair of photosensors turns at a varying angular speed the signal delivered by the LMD will vary depending on the position of the contrast feature located in the sensor's visual field. The validity of this reasoning was then tested by constructing a miniature scanning sensor, the output voltage of which turned out to be a quasi-linear function of the position of the contrast feature present in the visual field and to be largely independent of the distance and the level of contrast. This output can therefore be used to generate the appropriate motor commands for stabilizing a sensory platform subject to yaw, pitch, or roll in relation to environmental features and/or for tracking contrasting objects.