![]() However, most previous research with respect to the radial field piezoelectric diaphragm has focused on actuating or high frequency sensing. Besides, there are also some studies which design a piezoelectric diaphragm bearing double side spiral electrodes. reported a bulk PZT diaphragm with a ring shaped interdigitated electrode. released a thin film PZT diaphragm by ring shaped interdigitated electrodes. It can be poled by inter-circulating electrodes or interdigitated ring electrodes. realized an equivalent d 33 mode radial field diaphragm which can solve the problem. For micromachined piezoelectric circular diaphragms, it is usually hard to do in-plane poling because the radial scale is much bigger than the thickness. The PZT elements of the sensors work in d 31 mode which is not efficient compared with d 33 mode because usually the d 33 parameter of PZT is two times larger than the d 31 parameter. The PZT layer was fabricated by a sol-gel method and patterned electrodes were completed by microfabrication techniques. have conducted some studies on micromachined piezoelectric sensors for flow sensing. When a piezoelectric material is utilized to sense, it is self-powered. Charges will be induced on the surface when it is exposed to a deformation so one can collect these charges to get information about the excitation. They have been widely used in applications such as energy harvesters and accelerometers. Piezoelectric materials are a good solution to this problem. However, these flow sensors are piezoresistive devices which need a power supply to bias them. ![]() also designed a few sensors with a standing pillar which can extend into the ambient flow. fabricated polymer MEMS sensors with a membrane structure to detect the moving of underwater objects. utilized SU-8 standing structures on thin silicon cantilever beams. The sensing elements of the devices typically consist of deformable flexural elements, such as cantilever beams, diaphragms and bridges. The inspiration has led to the design of novel sensors. Though it is blind, the blind fish is still capable of perceiving its surroundings and avoiding obstacles by relying on its lateral line. The lateral line of blind fish is the most studied one. Recently, researchers have been paying attention to eliminating the issues of AUVs mentioned above by taking advantage of sensing principles inspired by Nature. Besides, they usually have a large size and heavy weight. Optical imaging will fail to work in dark and turbid water. However, sonar technology has a blind zone and the intense sound waves can be fatal to aquatic animals. Traditionally sensing strategies of AUVs to perceive their surroundings are sound navigation and ranging (SONAR) and optical imaging. Nowadays, autonomous underwater vehicles (AUVs) which can travel underwater without requiring input from an operator play an important role in underwater exploration and military applications. The present work provides a good application prospect for the underwater sensing of AUVs. Further, this sensor can work well under a disturbance with low frequency. Experimental results show that the sensitivity of the sensor is up to 1.16 mV/(mm/s), and the detectable oscillatory flow velocity is as low as 4 mm/s. By imitating the underwater disturbance and generating the oscillatory flow velocities with a vibrating sphere, the performance of the sensor in detecting the oscillatory flow was tested. The dynamic behaviors of the piezoelectric diaphragm were examined by the impedance spectrum. Sensor prototypes were fabricated by microfabrication technology. Finite element analysis was conducted to estimate the sensor behavior. This sensor is self-powered, does not need an external power supply, and works efficiently in d 33 mode by using inter-circulating electrodes to release the radial in-plane poling. This paper presents a new sensor based on a radial field bulk piezoelectric diaphragm to provide energy-efficient and high-performance situational sensing for autonomous underwater vehicles (AUVs).
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