## 1 Introduction
By doping different amounts of Nano-ZnO on PVDF-TrFE film, the piezoelectric strain constant and dielectric constant are improved, and the piezoelectric performance is improved [34]. Some scholars have studied using the fiber grating method. NASA [25] used a 38 cm \(\times\) 38 cm panel as the research object, and used 36 Bragg grating sensors to sense and locate the orbital debris impact. Using the embedded fiber Bragg grating sensor array, the health state of the composite structure was evaluated by extracting the eigenvalues [26]. Multi-channel fiber Bragg grating sensors were installed on composite materials. The proposed error-based singular value impact localization method is better than root mean square (RMS) and correlation-based positioning results, with an average error of 10.7 mm [35]. Systems based on PVDF film methods and fiber Bragg grating sensors are often complex. In aerospace applications, it is required to use as few sensors as possible for accurate impact locating. At the same time, it is required to minimize system size, quality, cost and energy consumption, and reduce unnecessary wiring. Acoustic emission has the characteristics of real-time, online, mature technology, low resource occupancy, relatively simple system and strong environmental adaptability, which is a very effective impact sensing and localization method. In this regard, some scholars have also conducted related research [36; 37; 38; 39; 40]. Through the maximum entropy linear approximation method, the four sensors were used to sense and locate the hammer impact on the aluminum plate, and compared with the artificial neural network and the support vector machine, it is found that it has better locating results and requires fewer parameters to be determined [37]. An impact recognition algorithm-based on principal component analysis and maximum entropy linear approximation was proposed to locate and quantify impact in aluminum and aluminum sandwich panels [39]. However, these methods of machine learning require the preparation of sample data for training in advance, and the workload is large. A total of six specimens of an aluminum panel, a quasi-isotropic carbon fiber reinforced polymer (CFRP) composite panel, a highly anisotropic CFRP composite panel, a stiffened aluminum panel, a stiffened quasi-isotropic CFRP composite panel, and a stiffened anisotropic CFRP composite panel were studied. The impact force was studied based on ultrasound [28], and the impact location was determined based on strain [30]. However, there are only two parallel stiffeners of smaller size in stiffened panels. The time-reversal method was used to locate the impact in the isotropic aluminum plate. It is found that the locating error gradually increased with the increase of the calibration position [41]. Array sensors were used to locate cracks in aluminum and stiffened aluminum panel based on time of flight, and the locating results were improved by optimizing the sensor network layout [42]. Taking anisotropic composite materials as the research object, the sound source localization method based on elliptic wavefront and non-elliptic wavefront of parametric curve is proposed. The sound source location is obtained respectively by calculating the wavefront direction vector based on the arrival time difference of the three sensors method [43] and by minimizing the objective function method [44]. The straight propagation path is not used, and the sound source position can be predicted without understanding the material elasticity, but the research object is a flat panel and does not have stiffener structure. The locating algorithm based on arrival time has the advantages of simple principle, easy implementation and fast locating speed. At the same time, the triangular method requires only a small number of sensors, which can further reduce resource occupation, but there are also some problems.