蹄蝠科（Hipposideridae）和菊头蝠科（Rhinolophidae）蝙蝠的超声声纳发射系统具有独特的动态特性,即鼻孔周围具有复杂挡板形状的结构（“鼻叶”）在特定肌肉的控制下可以在声纳信号发射期间发生主动动态形变。数值模拟和仿生研究表明这种动态特性可以显著改变发射声场分布并引入时变特性,使得发射声场成为时间、空间角度和载波频率的函数,而且新增加的时间维度可以为蝙蝠编码额外有用的传感信息。但是这种动态特性带来的时变传感效应的机理尚不清楚,故而到目前为止,类似的动态特性还没有被用于相关的工程应用（如声纳或雷达）,而且蝙蝠仿生机器人中几乎所有的声纳发射器都是静态的,但现有动态仿生声纳发射器所基于的蝙蝠种类（马铁菊头蝠）比较单一,缺少对比模型。因此,针对发射器动态特性的时变传感效应,本文从仿生学角度出发,将普氏蹄蝠的动态声纳发射系统与工程技术相结合,设计并搭建了一种新型仿生动态声纳发射器,并以此为模型对发射器动态特性产生的时变特征及其编码的传感信息进行了系统研究。本文以普氏蹄蝠鼻叶结构为对象设计了一种可真实重现鼻叶运动的新型仿生动态声纳发射器,丰富了仿生蝙蝠种类并为现有动态发射器构造了对比模型;基于该动态发射器对时变特征及其影响因素进行了定量和定性分析,为优化工程声纳发射器参数提供了实验依据和方法;分析了时变发射声场的固有维度,证明了鼻叶运动增加的时间维度可以对传感信息的编码产生独立的影响;提出了基于信息理论微分熵和相对熵的声场传感信息评价方法,分析并比较了时间、空间角度和载波频率三个维度在传感信息编码能力上的差异;引入了基于微分熵的互信息算法,分析了时变声纳信号发射期间因鼻叶运动而新增的传感信息,同时弥补了现有基于离散熵的互信息算法的缺陷。本文的研究一方面能够帮助生物学家更好地理解蝙蝠在声纳信号发射期间鼻叶动态形变对其“视野”范围的影响,从而推动蝙蝠动态传感信息编译机制的研究;另一方面能够帮助工程人员更好地理解动态工程声纳发射器的可行性,从而促进新型工程传感系统的研发。本文的主要研究内容和结论如下:一、基于普氏蹄蝠的鼻叶结构和运动模式设计并搭建了一种新型仿生动态声纳发射器。利用高速相机阵列和超声麦克风阵列等搭建了一个实验平台,同步采集了真实普氏蹄蝠的鼻叶运动数据和发射的超声声纳信号数据,重建了声纳信号发射期间蝙蝠鼻叶的运动轨迹和发射声场分布,通过相关性分析研究了鼻叶动态形变对发射声场的影响。结果显示:普氏蹄蝠鼻叶的动态形变主要表现为叶冠、上鼻叶、下鼻叶和鼻孔两侧叶瓣的闭合-开启运动,这些动态特性能够影响发射声场的声学特性:当鼻叶张开较大时,发射声场的波束宽度随鼻叶张开而变窄,但鼻叶张开较小时,发射声场分布有很多局部变化,有待进一步研究。基于这些生物实验数据,设计了柔性仿生鼻叶模型、驱动装置、控制系统和超声发射系统,进而组建了仿生动态声纳发射器,以模拟真实普氏蹄蝠的鼻叶动态形变,用于后续时变特征与传感信息的研究。二、基于仿生动态声纳发射器,利用梯度定量表征了鼻叶动态形变在发射声场产生的时变特征,分析了载波频率、鼻叶结构和运动模式三个因素对时变特征的影响。结果显示:鼻叶动态形变可以为发射声场引入时变特征,如声瓣宽度和方向随时间的变化、新旁瓣的出现等;载波频率、鼻叶结构和运动模式都会显著地影响时变特征的分布,其中,载波频率对时变波束图中梯度幅值分布的影响较为显著,鼻叶结构和运动模式的影响相对较小,而对于梯度方向分布,载波频率和鼻叶运动模式的影响略大于鼻叶结构;鼻叶动态形变对时变特征的最大影响表现为梯度方向分布的显著变化,对所研究的72种载波频率-鼻叶结构-运动模式组合,鼻叶动态形变时梯度方向上的信息熵都高于鼻叶处于静止状态的相应值,两者之间的差异最大约为鼻叶静止时的9.4倍,而两者在平均梯度幅值上的差异最大约为鼻叶静止时的53%;与基于马铁菊头蝠鼻叶的高度简化凹形挡板模型相比,本文的仿生鼻叶模型能产生更多的时变特征,这表明时变特征不仅取决于发射器孔径尺寸的增大或减小,还取决于发射器挡板结构的几何形状细节。三、利用该仿生动态声纳发射器,建立了沿时间、空间角度和载波频率三个维度采样较为密集的发射声场数据集,利用Isomap算法分析了该发射声场的固有维度,结果显示:发射声场中波束增益沿时间、空间角度和载波频率三个维度具有不同的分布;Isomap算法估计的固有维度总是大于或等于时变发射声场独立物理维度（时间、空间角度和载波频率）的数目,即无法对三个物理维度再降维,这表明鼻叶运动增加的时间维度与空间角度和载波频率两个维度相互独立,可以对传感信息的编译产生独立影响。四、利用微分熵和相对熵定量表征并比较了时变发射声场中时间、空间角度和载波频率三个维度对传感信息的编码能力,结果显示:每个维度编码的传感信息（微分熵）沿另两个维度的分布均可近似为均匀分布,特别是时间维度和载波频率维度编码的传感信息在很大空间角度范围内都近似相等,这表明蝙蝠声纳发射系统与人的听觉系统相似,不仅能够识别正前方目标,还可以识别周围各个方位的目标;时间维度编码的传感信息（均值为2.55 bits）明显小于空间角度维度和载波频率维度（均值分别为4.5 bits和4.24 bits）,但时间维度在少数空间角度和载波频率组合处编码的传感信息（3.2～4.5 bits）可以到达另两个维度编码的传感信息（3.2～5 bits）;空间角度和载波频率维度上的微分摘可以通过标准差预测（相关系数r分别为0.96和0.86）,而时间维度上的微分熵与标准差的分布较为离散（r=0.78）;对所研究的1040个空间角度,载波频率维度相对于时间维度的平均相对熵（约为3±0.7 bits）总是高于时间维度相对于载波频率维度的平均相对熵（约为1.4±0.3 bits）,但两者的差异较小（1.6±0.5 bits）,这表明时间维度的传感信息编码能力稍弱于载波频率维度。五、利用基于离散熵和基于微分熵的两种互信息算法,分析了整个鼻叶闭合运动期间任意两个时刻波束图共同拥有的传感信息,其中基于微分熵的互信息算法精度更高,但两种算法的分析结果非常相似,都显示出:任意两个时刻波束图之间互信息总是随其时间间隔的增大而减少,而且在鼻叶闭合运动期间互信息总能在15 ms内衰减到70%,这表明鼻叶的动态形变可以在一个声纳信号发射期间为蝙蝠提供多种近乎独立的“视野”,即传感信息可以在整个声纳信号期间连续不断地累积。

普氏蹄蝠的声呐系统具有显著的动态特性,包括声呐结构的动态形变(鼻叶运动、耳廓运动)和超声脉冲序列的动态调整(脉冲数目、激发时刻等)。为了研究这两种动态特性之间是否存在耦合关系,通过生物实验同步采集普氏蹄蝠的鼻叶运动、耳廓运

The flapping flight of many bat species is characterized by a high degree of maneuverability and provides fertile ground for biomimetic design. However, there has been little prior work toward understanding bat flight maneuvers, particularly using a coupled kinematic and aerodynamic framework. Here, wing kinematic data of a large insectivorous bat (Hipposideros armiger) in straight and turning flight is investigated. Fundamental to turning flight are asymmetries in the wing kinematics and consequently asymmetries in the aerodynamic forces. Forces were calculated from the wing kinematics using aerodynamic numerical simulations. Aspects of the wing kinematics in the turn that were distinguishable from straight flight were an increase in stroke plane deviation angle, nominal increase in flapping amplitude, and a decrease in the horizontal stroke plane angle of the wing inside the turn. While prior work on the mechanics of turning flight in animals has focused on classifying a turn as either banking or yawing, in the present work we show evidence of simultaneous and synergistic banking and yawing mechanisms. During the initiation of the turn, the bank angle was low, and elevated thrust by the outside wing generated a significant yaw rotational moment during both the upstroke and downstroke. Later in the turn, the bank angle increased to approximately 25 degrees tilting the net force vector toward the inside of the turn providing centripetal acceleration thereby turning the bat. Understanding the details of the turning mechanism-combined yaw and bank-provides useful design and control principles for biomimetic flapping MAVs.

Bats possess wings comprised of a flexible membrane and a jointed skeletal structure allowing them to execute complex flight maneuvers such as rapid tight turns. The extent of a bat's tight turning capability can be explored by analyzing a 180-degree U-turn. Prior studies have investigated more subtle flight maneuvers, but the kinematic and aerodynamic mechanisms of a U-turn have not been characterized. In this work, we use 3D optical motion capture and aerodynamic simulations to investigate a U-turn maneuver executed by a great roundleaf bat (Hipposideros armiger: mass = 55 g, span = 51 cm). The bat was observed to decrease its flight velocity and gain approximately 20 cm of altitude entering the U-turn. By lowering its velocity from 2.0 m/s to 0.5 m/s, the centripetal force requirement to execute a tight turn was substantially reduced. Centripetal force was generated by tilting the lift force vector laterally through banking. During the initiation of the U-turn, the bank angle increased from 20 degrees to 40 degrees. During the initiation and persisting throughout the U-turn, the flap amplitude of the right wing (inside of the turn) increased relative to the left wing. In addition, the right wing moved more laterally closer to the centerline of the body during the end of the downstroke and the beginning of the upstroke compared to the left wing. Reorientation of the body into the turn happened prior to a change in the flight path of the bat. Once the bat entered the U-turn and the bank angle increased, the change in flight path of the bat began to change rapidly as the bat negotiated the apex of the turn. During this phase of the turn, the minimum radius of curvature of the bat was 5.5 cm. During the egress of the turn, the bat accelerated and expended stored potential energy by descending. The cycle averaged total power expenditure by the bat during the six wingbeat cycle U-turn maneuver was 0.51 W which was approximately 40% above the power expenditure calculated for a nominally straight flight by the same bat. Future work on the topic of bat maneuverability may investigate a broader array of maneuvering flights characterizing the commonalities and differences across flights. In addition, the interplay between aerodynamic moments and inertial moments are of interest in order to more robustly characterize maneuvering mechanisms.

Old-World leaf-nosed bats (Hipposideridae) are echolocating bats with peculiar emission-side dynamics where beamforming baffles ("noseleaves") that surround the points of ultrasound emission (nostrils) change shape while diffracting the outgoing biosonar pulses. While prior work with numerical and robotic models has suggested that these noseleaf deformations could have an impact on the output characteristics of the bat's biosonar system, testing the hypothesis that this is the case in bats remains a critical step to be taken. The work presented here has tested the hypothesis that the noseleaf dynamics in a species of hipposiderid bat (Pratt's roundleaf bat,H. pratti) leads to time-variant acoustical properties on the output side of the bats' biosonar emission system. The time-variant effects of the noseleaf motion could be detected even in the presence of other sources of variability by comparing the distribution of pulse energy over the angle at different points in time. Furthermore, a convolutional neural network was able to classify the noseleaf motion state based on microphone array recordings with 85.3% accuracy. These results hence demonstrate that these nose-emitting bats have access to a substrate for behavioral flexibility on the emission-side of their biosonar systems.

Active noseleaf deformations during pulse emission observed in hipposiderid and rhinolophid bats have been shown to add a time dimension to the bats' acoustic emission characteristics beyond the established dependencies on frequency and direction. In this study, a dense three-dimensional acoustic characteristics were obtained by the time series of smoothed signal amplitudes at different directions and frequencies collected by a biomimetic dynamic sonar emitter. These data have been analyzed using differential entropy which was used as a measure to compare the encoding capacity for sensory information between the three different dimensions. The capacity for sensory information encoding measured in this way along time dimension was found to be similar to that along the frequency dimension. But both of them provided less information than provided by the direction dimension.

Bats have been reported to adjust the energy of their outgoing vocalizations to target range (R) in a logarithmic fashion close to 20log(10)R which has been interpreted as providing one-way compensation for increasing echo levels during target approaches. However, it remains unknown how species using high-frequency calls, which are strongly affected by absorption, adjust their vocal outputs during approaches to point targets. We hypothesized that such species should compensate less than the 20log(10)R model predicts at longer distances and more at shorter distances as a consequence of the significant influence of absorption at longer ranges. Using a microphone array and an acoustic recording tag, we show that the output adjustments of two Hipposideros pratti and one Hipposideros armiger do not decrease logarithmically during approaches to differentsized targets. Consequently, received echo levels increase dramatically early in the approach phase with near-constant output levels, but level off late in the approach phase as a result of substantial output reductions. To improve echo-to-noise ratio, we suggest that bats using higher frequency vocalizations compensate less at longer ranges, where they are strongly affected by absorption. Close to the target, they decrease their output levels dramatically to mitigate reception of very high echo levels. This strategy maintains received echo levels between 6 and 40 dB re. 20 mu Pa-2 s across different target sizes. The bats partially compensated for target size, but not in a oneto-one dB fashion, showing that these bats do not seek to stabilize perceived echo levels, but may instead use them to gauge target size.

Many bat species, e.g., in the rhinolophid and hipposiderid families, have dynamic biosonar systems with highly mobile pinnae. Pinna motion patterns have been shown to fall into two distinct categories: rigid rotations and non-rigid motions (i.e., deformations). In the present work, two questions regarding the rigid rotations have been investigated: (i) what is the nature of the variability (e.g., discrete subgroups or continuous variation) within the rigid motions, (ii) what is its acoustic impact? To investigate the first question, rigid pinna motions in Pratt's leaf-nosed bats (Hipposideros pratti) have been tracked with stereo vision and a dense set of landmark points on the pinna surface. Axis-angle representations of the recorded rigid motions have shown a continuous variation in the rotation axes that covered a range of almost 180 degrees in azimuth and elevation. To investigate the second question, the observed range of rigid pinna motions has been reproduced with a biomimetic pinna. Normalized mutual information between acoustic inputs associated with every pair of the rigid pinna motions showed that even small changes in the rotation axis resulted in more than 50% new sensory information encoding capacity (i.e., normalized mutual information less than 50%). This demonstrates a potential sensory benefit to the observed variability in the rigid pinna rotations.

蝙蝠对仿生扑翼飞行器研究具有重要启发价值。通过计算机视觉方法分析蝙蝠运动需要大量特征标记,因此准确提取、追踪标记是蝙蝠飞行研究的关键。常用的底层特征提取方法将局部极值作为特征点容易导致较高的标记错检率。提出一种基于图

本研究将探索仿生声呐在自然环境中的传感效应，其灵感来自蝙蝠的具有超声传感能力的生物声呐系统。首次通过仿生传感雏形比对蝙蝠在其最先进的生物声呐系统中发射和接收超声波时使用动态挡板来衍射超声波脉冲的现象进行深入研究。挡板的形变使其传感系统添加动态特性，其功能可为(1)加强传感系统的一般感知信息的编码能力,(2)提高某些编码的特定特征,(3)调整系统以适应不同的感测情况，这些功能将通过仿生声呐系统进行证实。该系统将构建模拟耳廓和鼻翼的可改变形状的人工智能挡板及声呐头雏形以发射以及接收超声的波脉冲信号，感测任务的感知信息的动态编码，通过用数值模拟和信息理论的方法对随机天然生物声纳场景和将所得的回声信号的处理进行分析。本研究可验证蝙蝠在复杂的天然环境中基于在两个耳朵接收到的两个时间信号这一简洁的信号输入满足感应需求来实现高性能导航的关键因素，为下一代人工智能声呐导航提供物理基础和应用前景。