Flow sensing is an essential technology used in marine science. Fish live in fluid environments. Therefore, it is not surprising that fish have developed abilities to sense flow. We designed an artificial lateral line sensor for oscillatory flow sensing by mimicking the lateral line organ of a fish. This sensor is composed of an artificial cupula that mimics the cupula of neuromasts, cantilever beam that mimics hair-like cilia, and perception unit that mimics hair cells. We designed four different cupula shapes and discussed the influence of the artificial cupula shape on the sensing performance. We analyzed the structure of the cantilever beam to determine its length. The perception unit uses a polyvinylidene fluoride (PVDF) membrane as the piezoelectric sensing element. To protect the sensor from harsh fluid environments, a well-designed waterproofing scheme was proposed. Finally, a dipole stimulus was chosen for experimental validation. An experimental setup was constructed, and several experiments were conducted to prove the different abilities of the proposed sensor. The proposed sensor demonstrated a threshold sensing limit of 3.4 mm/s in oscillatory flow sensing.

The rapid evolution of the Unmanned Aerial Vehicle (UAV) industry has significantly increased interest in UAV design with trans-domain capabilities. It is still a major challenge to achieve miniaturization and enhance the maneuverability and underwater reliability of trans-domain UAVs. In this paper, a novel bullet shape Trans-Domain Amphibious Vehicle (TDAV) is proposed which achieves free trans-domain motion and has the advantages of small size, high maneuverability and high reliability for both rotary-wing UAV and Autonomous Underwater Vehicle (AUV) operation. Compared with traditional amphibious machines, the TDAV design is streamlined and thus inherits the advantages of both the Bamboo Dragonfly and underwater AUVs. The proposed TDAV has a coaxial counter-propeller-tilting platform which satisfies the power and small diameter fuselage requirements, and the blades fold to reduce underwater drag and facilitate transportation. Further, a stable and efficient trans-domain attitude adjustment system is presented which effectively realizes trans-domain attitude switching. Based on the characteristics of the symmetric TDAV body, a rudder blade allocation algorithm is proposed to realize free movement in water. Finally, an improved particle swarm optimization algorithm is used to obtain suitable hierarchical fractional-order PID parameters. Both simulation and outdoor tests were performed and the results demonstrate that the proposed TDAV achieves outstanding performance in terms of lift altitude, trans-domain attitude switching time, and free trans-domain movement in both water and air.

Direction-of-arrival (DOA) mismatch can degrade the performance of adaptive beamforming algorithms. Thus, a projection method is proposed to correct this mismatch. In a beamforming algorithm, the DOA error is usually regarded as a steering vector error which is corrected using a steering vector optimization algorithm. This approach can provide an optimal steering vector but ignores the actual DOA estimate. The proposed algorithm provides correction after DOA estimation but before beamforming to improve both the DOA estimation accuracy and beamforming gain. First, the signal-to-noise ratio (SNR) of the signal is estimated and used to regularize the covariance matrix. Then, an estimated steering vector with DOA close to the true value is determined based on a minimum number of projections. Numerical results are presented to verify the effectiveness of the proposed method for DOA estimation correction. In most cases, this method improves the performance of the beamforming algorithms without changing them.

When we experimented on the sound source localization, if the interference and noise in the environment are influential, CBF (Conventional Beam-Forming) algorithms will hardly locate the sound source precisely. In certain situations, the sound source signal could be covered by interference. Consequently, we determine to restrain the effects of noise and interference on sound source localization with the MVDR (Minimum Variance Distortionless Response) algorithm. In the context of a fewer number of array elements and lower snapshots, the MVDR algorithm still sustains loftier resolution. The weight coefficient acquired by the algorithm can minimize the array output power in the anticipant direction. By means of simulation experiments, we broke down the capability of this algorithm including the ability of improving system performance, resolution and interference immunity. Eventually, we use the ICP (Inductively Coupled Plasma) MPA201 microphones and USB-2406 DAQ (Data Acquisition) device to constitute a signal acquisition system to gather the sound source signal. We performed MVDR processing on the factual test data and verified the resolution and interference suppression attribute of the algorithm.