Impact Detection Based On in-Situ Direct Writing Piezoelectric Polymer Sensor Array

External impact on high-stiffness structures such as aircraft and wind turbine blades are a common phenomenon in engineering practice, which may cause serious security risks to the equipment. In this work, piezoelectric polymer sensor array is utilized to realize impact location by passively monitoring complex structures due to their excellent flexibility and piezoelectric response. Here, PVDF-TrFE coatings are deposited on the structure by in-situ direct writing process and directly functionalized on structural surfaces. With the aid of this fabrication process, the piezoelectric polymer sensor's robustness, coupling effect and layout work are optimized for complex surfaces. To realize the in-situ direct writing process, a piezoelectric polymer sensing system was designed and assembled, which consists of a motion control system, a spray system, and a polarization system. Four piezoelectric polymer sensors are machined on the surface of the aluminum plate. The location results are calculated by the arrival time difference based on the envelope threshold extraction method. The experimental results show that the in-situ piezoelectric polymer sensor has perfect piezoelectric response characteristics and positioning at different heights and positions. The minimum detectable impact energy is as low as $1.5\times{10}^{-4}$ J while guaranteeing the positioning performance.