Optimum Design of Impact Sensors With Array Structure Polyvinylidene Fluoride (PVDF) Films

Highlights The impact sensors protected by shells and integrated with process circuits were proposed. Simulations and collision tests were performed to optimize the structure of the sensor. Accessories that can improve sensors’ detection accuracy were proposed. Multi-grain impact tests in a laboratory showed the RMSEs of two sensors were less than 1.67%. Abstract. Impact sensors are widely used to detect grain loss in harvesters, and the impact sensors with array structure polyvinylidene fluoride (PVDF) films have been proven to significantly increase the detection efficiency. However, uneven sensitivity and clutters from non-impacted sensitive units seriously affect the detection accuracy. This article proposes a protective shell for the impact sensors with array structure PVDF films. To improve the performance of this kind of sensor, we optimized the structure through finite element simulations and particle impact tests. The vibration modes under three pasting methods of sensitive units were analyzed. The relationship between the hardness of the elastic layer and response performances was investigated. To suppress the clutters, a method of splitting the elastic layer was proposed. Then, we manufactured two optimized impact sensors with one layer and two crossed layers of PVDF films and tested their performances. The results demonstrated that the sensitivities of the gaps between the PVDF films are poor. But when excluding the gaps’ data, the two sensors can meet the detection requirement. Accessories were proposed based on that characteristic to prevent particles from colliding with the gaps. After assembling the accessory, multi-grain impact tests showed that the root-mean-square errors (RMSEs) of the impact sensors with one layer and two crossed layers of PVDF films were 1.67% and 1.63%, respectively. Keywords: Grain loss detection, Particle impact test, Protective shell, Sensor accessory, Structure optimization.