Enhanced 6D Measurement by Integrating an Inertial Measurement Unit (IMU) with a 6D Sensor Unit of a Laser Tracker

Six-degree-of-freedom (6D) sensors enhance the measurement capability of traditional three-degree-of-freedom (3D) laser trackers. However, the classical 6D measurement techniques still have shortcomings in actual use, such as the problem of line of sight and relatively low data acquisition rate. The proposed approach by integrating an Inertial Measurement Unit (IMU) with a 6D sensor unit of a laser tracker is effective to overcome these limitations. The error is corrected by the combination of a Kalman filter and a backward smoothing algorithm. The Kalman filter only works when the 6D sensor's data is being sent through, while the backward smoothing algorithm works during the whole process. The experiments are performed to compare the error in three positions and three rotational orientations between the proposed method and the Kalman filter and evaluate the effects of different rates and IMU frequencies on the algorithm. The simulations are also performed to estimate the maximum outage time. The results verify that the proposed method can solve the problem of line of sight and low data acquisition rate effectively.</p

Low-Cost, Water Pressure Sensing and Leakage Detection Using Micromachined Membranes

This work presents the only known SOI membrane approach, using Microelectromechanical systems (MEMS) fabrication techniques, to address viable water leakage sensing requirements at low cost. In this research, membrane thickness and diameter are used in concert to target specific stiffness values that will result in targeted operational pressure ranges of approximately 0-120 psi. A MEMS membrane device constructed using silicon-on-insulator (SOI) wafers, has been tested and packaged for the water environment. MEMS membrane arrays will be used to determine operational pressure range by bursting.Two applications of these SOI membranes in aqueous environment are investigated in this research. The first one is water pressure sensing. We demonstrate that robustness of these membranes depends on their thickness and surface area. Their mechanical strength and robustness against applied pressure are determined using Finite Element Analysis (FEA). The mechanical response of a membrane pressure sensor is determined by physical factors such as surface area, thickness and material properties. The second application of this device is water leak detection. In devices such as pressure sensors, microvalves and micropumps, membranes can be subjected to immense pressure that causes them to fail or burst. However, this event can be used to indicate the precise pressure level that malfunction occurred. These membrane arrays can be used to determine pressure values by bursting. We discuss the background information related to the proposed device: MEMS fabrication processes (especially related to proposed device), common MEMS materials, general micromachining process steps, packaging and wire bonding techniques, and common micromachined pressure sensors. Besides, FEA on SOLIDWORKS simulation module is utilized to understand membrane sensitivity and robustness. In addition, we focus on theories supporting the simulated results. We also discuss the device fabrication process, which consists of the tested device’s fabrication process, Deep Reactive Ion Etching (DRIE) for membrane formation, two different realizable fabrication technique (depending on sensing material) of sensing element, metal contact pads, and connectors deposition. In addition, a brief description and operation procedures of the device fabrication tools are provided as well. We also include detailed electrical and mechanical testing procedures and the collected data