Gotowa bibliografia na temat „Threshold acceleration sensor”

Introduction. Diagnostic systems are designed to monitor the condition of operational components (for example, on the railway). It is imperative that micro-electromechanical systems (MEMS) equipped with acceleration sensors (accelerometers) be used as part of measuring diagnostic systems. It is known that accelerometers are operated under increased vibration and repeated shock loads. This imposes a limitation both on the accelerometer design and the properties of materials from which these devices are produced.Aim. To develop a micromechanical accelerometer (MMA) for surface acoustic waves (SAW), capable of measuring shock effects.Materials and methods. The theoretical part of the study was carried out using the mathematical theory of differential equations, theoretical mechanics, finite element analysis and elements of SAW theory. In the course of the work, the following methods of mathematical processing were applied: MATLAB, Mathcad, Maple, COMSOL Multiphysics, OOFELIE: Multiphysics, Bluehill3 software, CorelDRAW. Experimental studies were also conducted using the INSTRON 5985 floor automated test system.Results. An original design of MMA on a SAW capable of measuring shock effects in hundreds of g was proposed. A sensing element (SE) of the sensor was developed. An analysis of the plate materials for their use as part of the SAW-based MMA design showed that SE from the quartz ST-cut material has a wider range of measured accelerations and a higher sensitivity threshold than SE from the YX-128˚ cut-off lithium niobate material. Requirements were developed to increase the SE sensitivity threshold. Design requirements were developed, and an interdigital transducer (IDT) topology in the form of a ring resonator was proposed. The following output characteristics were assessed: sensitivity threshold, dynamic range and scale factor. In addition, a procedure was developed for calculating MMA on a SAW with a ring resonator on an anisotropic material. It was found that the developed SE is characterized by a high sensitivity threshold, a wide dynamic range and a low transverse sensitivity.Conclusion. The technique proposed for designing a sensing element for use in solid-state linear acceleration sensors facilitates, depending on technical requirements, selection of construction materials and sensor design. Due to the originality of the design and engineering solutions, the proposed accelerometer allows measurements to be carried out across a wide range of impact loads.

A low-g triggered micro-electromechanical system (MEMS) resonant acceleration switch is designed, fabricated and tested in this paper for near-zero power wake-up applications. The switch is actuated by ambient low-g vibration, consuming zero power while waiting for vibration at its resonant frequency. A cantilever beam and proof mass structure is adopted in the switch. The patterns of spiral cantilever beams are designed for low resonant frequency and threshold. Once the vibration with resonant frequency exceeds the acceleration threshold of the switch, the movable electrode becomes sufficiently displaced to contact the fixed electrodes and causes them to trigger. The dynamic responses of the switch are tested on a piezoelectric stack. The experimental results show that the switch closes under vibration at a frequency as low as 39.3 Hz and at an acceleration threshold of 0.074 g. A wake-up sensor node connected to the switch can awaken when the switch is under vibration as an intended characteristics.

A new method is introduced by using high precision accelerometer and gyroscope micro-electromechanical sensors (MEMS), which can record Lagrangian observations of sediments and shed light into the dynamics of sediment transport processes at above threshold conditions. The sensor can be used under a range of well-controlled flow conditions and can record measurements at high frequency (200 Hz), which can be used at the field. The smart sphere performance was evaluated by comparing its rotation and acceleration readings from the sensors to the video recordings of both top and underwater high-speed camera for a range of flow rates and sphere densities. Furthermore, an initial attempt to compare the smart-sphere’s velocity is achieved, by transforming the particle’s velocity from the Lagrangian frame of reference, obtained from the inertial sensor, to its velocity at the Eularian frame, obtained from the top camera.

Smart buildings will soon be a reality due to innovative Internet of Things (IoT) applications. IoT applications can be employed not only for energy management in a building, but also for solving emerging social issues, such as inter-floor noise-related disputes in apartments and the solitary death of an elderly person. For example, acceleration sensors can be used to detect abnormal floor vibrations, such as large vibrations due to jumping children or unusual vibrations in a house where an elderly person is living alone. However, the installation of a conventional accelerometer can be restricted because of the sense of privacy invasion. In this study, a self-powered wireless sensor using a threshold-based method is studied for the detection of floor vibrations. Vibration levels of a bare slab in a testbed are first measured when a slab is impacted by a bang machine and an impact ball. Second, a piezoelectric energy harvester using slab vibration is manufactured to generate electrical power over a threshold. Next, the correlation among harvested energy, floor vibration, and impact noise is studied to check whether harvested energy can be employed as a condition detection threshold. Finally, a prototype of a self-powered wireless sensor to detect abnormal conditions in floor vibrations is developed and its applicability is demonstrated.