Herein, a broadband ultrasensitive acoustic sensor based on an optical nanofiber coupler (ONC) attached to a diaphragm is designed and experimentally demonstrated. The ONC is sensitive to axial strain and works as the core transducing element to monitor the deformation of the diaphragm driven by acoustic waves. We first theoretically studied the sensing property of the ONC to axial strain and the deformation of the diaphragm. The results reveal that ONC working at the dispersion turning point (DTP) shows improved ultra-sensitivity towards axial strain, and the largest deformation of the circular diaphragm occurs at the center. Guided by the theoretical results, we fabricated an ONC with a DPT at 1550 nm, and we fixed one end of the ONC to the center of the diaphragm and the other end to the edge to construct the acoustic sensor. Finally, the experimental results show that the sensor can achieve accurate measurement in the broadband acoustic wave range of 30~20,000 Hz with good linearity. Specifically, when the input acoustic wave frequency is 120 Hz, the sensitivity reaches 1923 mV/Pa, the signal-to-noise ratio is 42.45 dB, and the minimum detectable sound pressure is 330 μPa/Hz^1/2. The sensor has the merits of simple structure, low cost, and high performance, and it provides a new method for acoustic wave detection.

To solve the technical problem that wheeled vehicles are prone to skidding on complex ground, due to poor adhesion performance, a tire-tread-structure design method based on the bionic principle is proposed in this paper. The 3D model of a goat’s foot was obtained using reverse engineering technology, and the curve equation was fitted by extracting the contour data of its outer-hoof flap edge, which was applied to the tire-tread-structure design. The bionic and herringbone-pattern rubber samples were manufactured, and a soil-tank test was carried out using an electronic universal tensile-testing machine, in order to verify the simulation results. The results showed that the overall adhesion of the bionic tread-pattern was greater than that of the normal tread-pattern with the same load applied and the same height and angle of the tread-pattern structure, and the maximum adhesion was increased by 14.23%. This research will provide a reference for optimizing the pattern structure and thus improving the passing performance of wheeled vehicles.

The necks of birds that possess complex structures, graceful curves, and flexible movements are perfect natural motion actuators. Studying their structural features, mechanic characteristics, and motion rules can provide valuable references for imitating such actuators and motion functions artificially. Previous studies have analyzed the influence of two-dimensional motion geometric features and anatomical structure of the neck on motion efficiency and motion stability. However, the mechanism of motion flexibility from the perspective of neck structure has not been investigated. This study investigates the general law of the relationship between the structural parameters and motion characteristics of birds’ necks using tomography technology and 3D reconstruction technology. The results show that the structural characteristics of geese and ducks are similar, and there are significant differences in joint motion characteristics. Geese obtains complex neck postures through active intervertebral joints and highly flexible facet joints and possesses higher neck flexibility than ducks. This study provides a generic measuring method for obtaining birds’ cervical spinal vertebral structural dimensional parameters and offers a new theoretical concept for bionic robotic structural design and manufacture.

In order to improve the slope movement stability and flexibility of quadruped robot, a theoretical design method of a flexible spine of a robot that was based on bionics was proposed. The kinematic characteristics of the spine were analyzed under different slopes with a Saanen goat as the research object. A Qualisys track manager (QTM) gait analysis system was used to obtain the trunk movement of goats under multiple slopes, and linear time normalization (LTN) was used to calibrate and match typical gait cycles to characterize the goat locomotion gait under slopes. Firstly, the spatial angle changes of cervical thoracic vertebrae, thoracolumbar vertebrae, and lumbar vertebrae were compared and analyzed under 0°, 5°, 10°, and 15° slopes, and it was found that the rigid and flexible coupling structure between the thoraco–lumbar vertebrae played an obvious role when moving on the slope. Moreover, with the increase in slope, the movement of the spine changed to the coupling movement of thoraco–lumbar coordination movement and a flexible swing of lumbar vertebrae. Then, the Gaussian mixture model (GMM) clustering algorithm was used to analyze the changes of the thoraco–lumbar vertebrae and lumbar vertebrae in different directions. Combined with anatomical knowledge, it was found that the motion of the thoraco–lumbar vertebrae and lumbar vertebrae in the goat was mainly manifested as a left–right swing in the coronal plane. Finally, on the basis of the analysis of the maximin and variation range of the thoraco–lumbar vertebrae and lumbar vertebrae in the coronal plane, it was found that the coupling motion of the thoraco–lumbar cooperative motion and flexible swing of the lumbar vertebrae at the slope of 10° had the most significant effect on the motion stability. SSE, R², adjusted-R², and RMSE were used as evaluation indexes, and the general equations of the spatial fitting curve of the goat spine were obtained by curve fitting of Matlab software. Finally, Origin software was used to obtain the optimal fitting spatial equations under eight movements of the goat spine with SSE and adjusted-R² as indexes. The research will provide an idea for the bionic spine design with variable stiffness and multi-direction flexible bending, as well as a theoretical reference for the torso design of a bionic quadruped robot.

The goose’s neck is an excellent stabilizing organ with its graceful neck curves and flexible movements. However, the stabilizing mechanism of the goose’s neck remains unclear. This study adopts a dynamic in vivo experimental method to obtain continuous and accurate stable motion characteristics of the goose’s cervical vertebra. Firstly, the results showed that when the body of a goose was separately moved back and forth along the Y direction (front and back) and Z direction (up and down), the goose’s neck can significantly stabilize the head. Then, because of the limitation of the X-ray imaging area, the three-dimensional intervertebral rotational displacements for vertebrae C4–C8 were obtained, and the role that these five segments play in the stabilization of the bird’s neck was analyzed. This study reveals that the largest range of the adjacent vertebral rotational movement is around the X-axis, the second is around the Y-axis, and the smallest is around the Z-axis. This kinematic feature is accord with the kinematic feature of the saddle joint, which allows the flexion/around X-axis and lateral bending/around Y-axis, and prevents axial rotation/around Z-axis.

In this study we explored the methods and effects of spectral resistance reduction for soil-engaging surface of self-excited resonant bulldozing plates with a plane base on the basis of resonance effects. In the acquisition of the low-order vibration frequency f₀ of the bin soil, centering around frequency point f₀, eight spatial geometric wave frequency points n_i of soil-engaging surfaces and three amplitudes were selected; by superimposing with soil-engaging surfaces of plane-based bulldozing plates, 24 spectral structures of the soil-engaging surface of bulldozing plates and model samples were combinatorically designed. Resistance reduction characteristics of each model sample were tested using an indoor soil bin test. Near the resonance point f₀, the structures of the self-excited vibrating frequency spectrum of the soil-engaging surface obtain a preferable inhibitory effect on working resistance. At a 4 mm amplitude resonance point, model samples achieved the best resistance reduction effect, with a maximum relative resistance reduction rate of 22.67%, and the soil desorption effect of the relevant model sample was also good. On the other hand, away from the resonance point, whether the frequency increased or decreased, the corresponding working resistance of the model sample surfaces increased relatively. This is in good agreement with the law that the resonance point amplitude of the theoretical resonance curve is higher and the amplitude on both sides is lower. This paper provides a reference for the parameter design and related product development for various forced or self-excited vibration soil cutting tools.