A Human Body Pressure Distribution Imaging System Based on Wavelet Analysis and Resistance Tomography

Active Body Pressure Relief System with Time-of-Flight Optical Pressure Sensors for Pressure Ulcer Prevention

A body pressure relief system was newly developed with optical pressure sensors for pressure ulcer prevention. Unlike a conventional alternating pressure air mattress (APAM), this system automatically regulates air flow into a body supporting mattress with adaptive inflation (or deflation) duration in response to the pressure level in order to reduce skin stress due to prolonged high pressures. The system continuously quantifies the body pressure distribution using time-of-flight (ToF) optical sensors. The proposed pressure sensor, a ToF optical sensor in the air-filled cell, measures changes in surface height of mattress when pressed under body weight, thereby indirectly indicating the interface pressure. Non-contact measurement of optical sensor usually improves the durability and repeatability of the system. The pressure sensor was successfully identified the 4 different-predefined postures, and quantitatively measured the body pressure distribution of them. Duty cycle of switches in solenoid valves was adjusted to 0–50% for pressure relief, which shows that the interface pressure was lower than 32 mmHg for pressure ulcer prevention.

Coal Mine Inclined Shaft Advanced Detection Method and Physical Model Test Based on Shield Cutterhead Moving Array Electrodes

Using tunnel boring machine (TBM) to construct inclined shafts in coal mines has become the main way for large-scale coal mines to enter deep mining faces. However, some engineering disasters such as water in rush and rock burst will occur when TBM crosses the aquifer and weak broken rock strata. For the sake of efficient tunneling and advanced optimization of the safety plan and supporting measures, it is critically important to detect the anomalous geological conditions in front of the driving face during the service of TBM. Based on the bore-tunneling electrical ahead monitoring (BEAM) system, this paper proposes a coal mine inclined shaft advanced detection method based on shield cutterhead moving array electrodes. First, as the BEAM system cannot image owing to its low utilization rate on spatial distribution information, a diversified excitation and measurement mode with the cutters on the cutterhead as the exciting electrode and measuring electrode is proposed to provide a calculation condition for inversion imaging of the geological condition in front of the driving face. Then, in order to improve the speed of inversion imaging, a virtual grounding electrode equivalent model is proposed to replace the original guard electrode model. Finally, in order to verify the effectiveness of the method, the influence of the virtual grounding electrode on the inversion results at different positions is studied through a physical model test and a numerical inversion test. The results show that the method can better reflect the position of anomalous body.

Three Dimensional Distribution of Sensitive Field and Stress Field Inversion of Force Sensitive Materials under Constant Current Excitation

Force sensitive conductive composite materials are functional materials which can be used as the sensitive material of force sensors. However, the existing sensors only use one-dimensional electrical properties of force sensitive conductive materials. Even in tactile sensors, the measurement of contact pressure is achieved by large-scale arrays and the units of a large-scale array are also based on the one-dimensional electrical properties of force sensitive materials. The main contribution of this work is to study the three-dimensional electrical properties and the inversion method of three-dimensional stress field of a force sensitive material (conductive rubber), which pushes the application of force sensitive material from one dimensional to three-dimensional. First, the mathematical model of the conductive rubber current field distribution under a constant force is established by the effective medium theory, and the current field distribution model of conductive rubber with different geometry, conductive rubber content and conductive rubber relaxation parameters is deduced. Secondly, the inversion method of the three-dimensional stress field of conductive rubber is established, which provides a theoretical basis for the design of a new tactile sensor, three-dimensional stress field and space force based on force sensitive materials.