振-碰耦合电子果实装置设计与试验

    Design and experiment of vibration-collision coupling electronic fruit (VCCEF) device

    • 摘要: 果实在采摘、分选及运输过程中持续承受振动、碰撞、冲击等多种机械荷载的耦合作用,这类作用是导致其品质劣变与采后损失的核心诱因。然而,现有电子果实装置多针对跌落、挤压、碰撞等单一载荷场景设计,其传感器结构与数据采集系统难以精准捕捉单果及串型果实在振动 - 碰撞耦合作用下的动态力学响应特性,进而制约了果实采后机械损伤演化机理的深入探究。为此,该研究以鲜食葡萄为试验对象,设计了一种可同步获取果实振动加速度与碰撞力动态响应的振-碰耦合电子果实(vibration-collision coupling electronic fruit, VCCEF)装置。该装置由三维振动测量系统、三维碰撞测量系统及振-碰数据同步采集系统构成,通过压电陶瓷球壳结构内部集成三轴加速度传感器,实现对碰撞冲击力、振动加速度及耦合动态响应的同步高精度采集。同时,构建了基于该装置的双梗 - 果复合系统,提出多果实振-碰数据的同步采集分析与校核方案,为探究多果-梗系统的振动-碰撞耦合演化规律提供支撑。标定试验结果表明,三维振动检测的相对误差范围在4.24%~7.27%之间,碰撞力-感应电压拟合曲线的决定系数R2为0.9933。 在偏角为 30°、45°、60° 和 75° 的双果振-碰耦合试验中,结果表明碰撞力与振动加速度峰值的时间偏差为 71 ms,同步性良好,同时加速度响应呈现明显的方向性。综上,振-碰耦合电子果实(VCCEF)可精准监测果实间的振-碰动态信息,为揭示果实非稳态碰撞的时域响应特征、动态传递规律及采运设备力学参数优化提供了装备与方法支持。

       

      Abstract: Fruits are continuously subjected to the multiple mechanical loads, such as the vibration, collision, and impact during harvesting, sorting, and transportation. The coupling scenario can often lead to the fruit quality deterioration and post-harvest losses. However, the existing electronic fruit devices have been mostly designed for the single-load scenarios, such as the dropping, extrusion, and collision. The sensors and data acquisition cannot accurately capture the dynamically mechanical response of the single and clustered fruits under vibration-impact coupling scenarios. It is required to explore the evolution mechanism of the post-harvest mechanical damage to the fruits. In this study, a vibration-collision coupling electronic fruit (VCCEF) device was developed to simultaneously acquire the dynamic response of the fruit vibration acceleration and collision force. The fresh grapes were taken as the experimental object. The device was composed of a three-dimensional vibration, a three-dimensional collision measurement, and a vibration-impact data synchronous acquisition. A triaxial acceleration sensor was integrated inside a spherical shell with the piezoelectric ceramics. The synchronous and high-precision data acquisition was then achieved in the collision impact force, vibration acceleration, and coupled dynamic responses. Meanwhile, a double pedicel-fruit composite was constructed for the data acquirement. Synchronous acquisition, analysis, and verification were realized for the multi-fruit vibration-impact data. Finally, a series of tests were also carried out to explore the vibration-impact coupling evolution of the multi-fruit-pedicel systems. Three-dimensional vibration measurement was calibrated after exploration. Test results showed that the relative error of the triaxial acceleration was ranged from 4.24% to 7.27%, fully meeting the test requirements within an acceptable range. The coefficient of determination (R²) of the collision force-induction voltage fitting curve reached 0.9957, indicating an excellent fitting. The vibration-impact coupling tests were also conducted on the double fruit under different deflection angles (30°/45°/60°/75°). The vibration-impact patterns of the fruit particles were similar among the four groups of the deflection angles. At the moment when the vibration-impact occurred, the peaks were instantaneously obtained in the collision force of the piezoelectric ceramic shell and the acceleration of the internal triaxial acceleration sensor, with a time deviation of 71 ms between the two peak moments, indicating the excellent synchrony. The collision force peak of the double pedicel-fruit device increased from 1.19 to 2.59 N, with a total increase of 117.65%. Furthermore, there was a non-linear increase in the collision force peak, as the deflection angle increased. The output signal of the piezoelectric ceramic was positively correlated with the force rate, according to the direct "mechanical-electrical energy" conversion. Its response to sudden changes in the instantaneous force then reached the microsecond level. The response of the triaxial acceleration to the collision exhibited the significant directionality, indicating the differential variations in the deflection angle. Among them, the peak value (absolute value) of the Y-axis acceleration increased by 210% in total from 30° to 75°, which was always the largest component among the three axes. There was the strongest correlation with the collision force peak. The electronic fruit was used to accurately capture the variations in the collision force under different deflection angles, fully meeting the measurement requirements of the fruit micro-collisions; Subtle differences were identified from the acceleration under various deflection angles, in order to characterize the "instantaneous loading" feature of the collisions. In conclusion, the VCCEF can be expected to accurately monitor the vibration-impact dynamic information among fruits. The finding can provide the equipment and methodological support for the time-domain response and dynamic transmission of the fruit unsteady collisions, in order to optimize the mechanical parameters of the fruit harvesting and transportation.

       

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