Indirect Pressure Measurement on Hydraulic Components Through New MEMS Strain Sensors

Abstract

Sensors are playing a more important role in the modern hydraulic systems. Increasing needs for closed loop controls, high precision measurement, power control and energy monitoring, diagnosis and safety concerns, ask for both pressure and flow acquisition in both industrial and mobile applications. Traditional pressure sensors need specific bored screw for mounting, and both pipes and components must be modified in order to apply pressure sensors. Traditional pressure sensors are related to mini-mess and to oil flow modification in the sensor area. Sensors position in hydraulic circuits or components must be defined at design phase, in order to design the proper screw in desired circuit positions. Most of times sensors result in a efficiency loss in the circuit. Last but not least, the cost of traditional sensors, the need for proper connections for sensors installation and the work needed for sensor placement in machines production phase, could be avoided if sensors could be integrated in smart components. Modern Silicon based technologies offer new solutions for a less invasive pressure measurement. Micro Electro-Mechanical Systems (MEMS) Technology is suitable to design new sensors for indirect pressure measurement. Also traditional technologies, coupled with modern electronics could offer solutions that were not enough precise 10 years ago, but presenting some tricks to be solved accurately. The paper presents the first experimental results of the early stage of application of a MEMS strain gauge sensor application on components, where hydraulic pressure is measured through the component strain due to internal pressure force and component deformation. New sensors called Double Ended Tuning Fork (DETF) MEMS Resonant Extensometer sensor, based on a silicon diapason made in void environment in a system on chip will be applied at components due to the sensor’s sensitivity and precision that can reach the 0,15 nε/ε. At the same time the paper will show that pipes offer a deformation function of the mechanical characteristics and that the pressure effect is causing a deformation that can be even too high for the MEMS sensor. The strain position sensor and component deformation are also proved by the FEM analysis in order to validate both pressure measurement and FEM analysis in respect to test bench results applied to the sensor strain acquisition.