Design of a dynamic sonar emitter inspired by hipposiderid bats

Abstract

The ultrasonic emission of the biosonar systems of bats, such as Old World leaf-nosed bats (family Hipposideridae) and the related horseshoe bats (family Rhinolophidae), is characterized by a unique dynamics where baffle shapes ('noseleaves') deform while diffracting the outgoing wave packets. As of now, nothing comparable to this dynamics has been used in any related engineering application (e.g. sonar or radar). Prior work with simple concave baffle shapes has demonstrated the impact of the dynamics on the emission characteristics, but it has remained unclear whether this was simply due to the change in aperture size or also influenced by the geometrical shape detail. Hence, it has also remained unclear whether it would be possible to further enhance the time-variant effects reported so far through different static and dynamic geometries. To address this issue, we have created a dynamic emission baffle with biomimetic shape detail modeled after Pratt's roundleaf bats (Hipposideros pratti). The impact of the dynamic deformation of the shape on the time-variant emission characteristics was evaluated by virtue of the gradient magnitude and the entropy in the gradient orientation. The results have shown that the dynamics results in much larger gradients in signal representation, which change jointly over direction and time.

A biomimetic soft robotic pinna for emulating dynamic reception behavior of horseshoe bats

“…The independently controlled actuators used in the present design were able to produce eight visibly unique bending profiles providing a level of control over the pinna deformation that is significantly greater than what has been achieved in previous versions of the sonar head [19][20][21]. Additionally, interactions between the simultaneous inflations of different elastomeres were observed that could be the result of changes to the load of one actuator through the action of another.…”

“…Here we introduce a biomimetic robotic sensor system for active information encoding, in which we have realized a complete perception-action loop inspired by bats. This design is the latest in a sequence of prototypes we have designed and built to understand the impact of moving noseleaves and/or pinnae [16][17][18][19][20]. Previous prototypes have demonstrated how changing conformation states [21] and fast moving pinnae [15] can create observable changes in the acoustic characteristics of the sensory system.…”

Eavesdropping like a bat: Towards fusing active and passive sonar for a case study in simultaneous localization and mapping

“…They can balance sensor range, opening angle, and spatial resolution using techniques such as modulating sound frequency [19], temporal shape of the sound wave signal [20], or sound direction [21]. To create and analyze acoustic signals, they may also actively move their nose leaves and pinnae, which has inspired engineers to build biomimetic emitters and receivers [22][23][24]. With multiple receivers, it is possible to localize a sound source based on the time difference of arrival of the sound to different receivers, as shown in the literature [25][26][27].…”

Differential Entropy Analysis of the Acoustic Characteristics of a Biomimetic Dynamic Sonar Emitter

“…Besides relying on the static geometry of their noseleaves, both rhinolophid and hipposiderid bats also have the ability to alter their noseleaf shapes during pulse emission through muscular actuation [6]. Numerical and biomimetic robotic studies have suggested that these dynamic noseleaf deformations can alter the shape of the emission beam and hence, add a time-dependence to the emission characteristics which hence becomes a function of direction, frequency, and time [5,7,8]. Information-theoretic analysis has shown that the time dimension could support the encoding of additional, useful sensory information [9][10][11].…”

“…If the time and frequency dimension are of similar importance to the biosonar sense, we would expect them to be similar in terms of their information coding capacity. Since representing a function of three independent variables requires more data than could be obtained from a behaving animal under controlled conditions, we have used a biomimetic reproduction of a hipposiderid noseleaf ( Figure 1a-c, [7]) to collect the experimental data. Based on this data, we have assessed the information coding capacity using differential entropy because it is a good match for our continuous data and does not require an arbitrary discretization [12].…”