Design A Hybrid Micro-force Sensor Integrated Actuating & Sensing

The piezoelectric micro-force sensors offer a lot of advantages for MEMS applications such as low power dissipation, high sensitivity, and easily integrated with piezoelectric micro-actuators. In spite of many advantages above, the research efforts are relatively limited.In this thesis, in order to increase the sensitivity of the piezoelectric micro-force sensors, and integrate with the piezoelectric micro-actuators, a PVDF (polyvinylidene fluoride) thin-film micro-force sensor is systematically studied in terms of the deposition and characterization of the PVDF thin-film, design, fabrication and test of the micro-force sensors based on micro-cantilever structures. In this paper, a developed IPMC/PVDF structure together with compensation algorithm is presented. The problem of feed-through coupling from the actuation signal to the sensing signal, arising from the proximity of IPMC and PVDF, presents a significant challenge in real-time implementation. To reduce the coupling while minimizing the stiffening effect, the thickness of the insulating layer is properly chosen.In this paper, the sensing theory of micro-cantilever is systematically analysised, a white-box model for PVDF micro-cantilever between force, deformation and sensing voltage is also provided by modal analysis based on piezoelectric effect. Sensing and frequency characteristics of piezoelectric-film have been analyzed using the NI-DAQ PCI 6221 by Lab VIEW system. Based on the analysis above, sensing circuits (differential charge amplifier and micro-current amplifier) have been designed and debugged. And then, a complete testing platform is developed. Since the sensing signal is very weak, this paper designed a high-sensitivity sensor probe, including preamplifier, differential circuit limit circuit and anti interference design. In order for miniaturization, we discussed principle and implementation of real-time signal acquisition and processing with DSP. This paper built up the micro-force signal detecting system software for the piezoelectric micro-cantilever and carried out the experiments using the designed circuit and software. And further more chose curve-fitting algorithm were used to estimate the unknown parameters. The sensory system is estimated to be 6.4mV/uN and its resolution is 0.11 uN, linearity is 3.83%.The out dynamic range of the sensor is 0.4552Hz to 50Hz.