ADVANCEMENTS IN NONINVASIVE PRESSURE SENSING IN HYDRAULIC COMPONENTS

Sensors and sensorized components are gaining for importance in hydraulics, due to increasing need for control and diagnostics. Sensors and specifically pressure sensors are widely available, but most of them are invasive and require threaded mounting holes or T-junctions, often coupled with a fluid pressure drop. The paper deals with advancements in a noninvasive pressure sensing method based on indirect pressure measurement, performed through direct acquisition of the component’s strain under pressure effect. Optimized MEMS sensors, based on micro-mechanical resonance frequency variation under mechanical stress, allow a very precise strain and pressure measurement, fully temperature compensated. The applied research shows the technology advancements in MEMS design and in the improvements of finding the best position for the sensor on the hydraulic components, as well as the sensor calibration and data management. All tests were performed at Bonfiglioli S.p.A. company R&D test bench using production hydraulic motors, and data were gathered using both the embedded test bench electronic control, the data logging system and directly from the edge unit connected to the MEMS sensors. The paper will show that not only a noninvasive pressure measurement is possible using the MEMS-DETF sensors, but also that a simple temperature compensation method is possible, available with two different methods: an experimental one and a computational one, based on metal and Silicon thermal linear expansion coefficient.