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多连杆串联推拉式香蕉悬挂运载方法与装置研究

Research on multi-linkage series push-pull banana suspension carrying method and apparatus

  • 摘要: 针对香蕉成熟期短、人工搬运成本高且效率低、采后不能成穗及时运抵分装转运点、现有运载小车及无人机吊运运载能力低导致难于推广应用,造成香蕉腐烂而影响产业可持续发展的问题,该研究分析了香蕉采后搬运现场的空间限制和固定要求,提出多连杆串联推拉式香蕉悬挂运输方法。利用香蕉树间距搭建支撑架和运载轨道,通过动力装置推拉多连杆串联机构运载穗蕉。基于香蕉果穗尺寸与重量、运载原理与轨道结构参数,确定不同坡度下的运载装置驱动力和运载速度,建立了运载轨道及支撑架受力和稳定性分析模型,分析了运载不同穗重时的轨道倾斜角度、不同加载时间时支撑变形量及支反力、轨道运载速度范围,开展了多连杆串联推拉式香蕉悬挂运载试验。结果表明,对于3.30 kW驱动的30根连杆串联推拉式香蕉悬挂运载装置,运载穗重45 kg香蕉30穗1350 kg时,坡度25º线路上最大运载速度可达1.53 km/h。运载最大穗重70 kg香蕉30穗时,运载轨道支撑连接强度较好且轨道倾斜角度低于支撑失稳的临界角度,运载轨道承受载荷远低于发生非线性屈曲的临界失稳载荷。运载速度是影响轨道运载平稳性的关键因素,运载速度高于0.58 km/h有利于减小香蕉穗承受的机械振动损伤,但会增大轨道及支撑的振动。运载速度0.98、1.16、1.49和2.21 km/h时,运载轨道最大振动加速度分别为43.89、130.92、43.61和165.54 m/s2,运载载荷激励频率与轨道及支撑的固有频率相近导致的激振强化会急剧增大轨道振动加速度,调整运载速度使运行载荷激振频率避开轨道固有频率,能够有效降低运载轨道运行振动加速度。

     

    Abstract: Fast-ripening banana are often required to be harvested in a timely manner at full maturity in the sustainable industry. However, manual handling after harvesting cannot fully meet the large-scale transportation to central processing points, due to its high cost and low efficiency. The lifting and transport of existing transport carts and drones can also result in delays with the delivery of bunches to processing, packaging, and transshipment points. Delays in manual transportation to the destination have also caused the banana to rot. It is often required to suspend banana bunches during transport. In this study, the push-pull suspension device was developed for banana conveyance using tandem multi-link assemblies. A systematic investigation was made to examine the gradients when transporting banana from the harvest site to the processing plant, and the spatial constraints between banana trees. The space between banana trees was utilized for the support frames and transport tracks. A power unit was used to drive a series of multi-link mechanisms, pushing and pulling them in sequence. Two-link mechanisms were connected via a joint mechanism with banana suspension hooks fixed below the joint. The banana were then suspended from these hooks. The series-connected multi-link mechanism then moved to transport the suspended banana, due to the pushing and pulling action of the drive unit. The driving force and transport speed of the transport device were determined under different gradients, according to the size and weight of the banana bunches, the transport, and the structural parameters of the track. Models were then established to determine stress in the transport track and support structure, as well as the stability of the support. An optimal combination of the parameters was determined as the inclination angle of the track for different bunch weights, support deflection, and reaction forces at various loading times and transport speeds. Additionally, experimental tests were conducted on a multi-link series push-pull transport system for banana suspension. The results show that the maximum transport speed on a 25° gradient track was 1.53 km/h using a 3.30 kW drive unit to power a push-pull banana transport with 30 connecting rods, when carrying 1,350 kg of banana in 30 bunches of 45 kg each. Furthermore, there was a high strength of the track support connection when transporting 30 bunches of banana with a maximum weight of 70 kg per bunch. The inclination angle of the track was less than the critical stability angle for the track and its supports. The transport load on the carrier track was significantly lower than the ultimate load at which the transport track and its supports, indicating the critical nonlinear buckling. Theoretical and experimental results further confirm that the transport speed was a key factor influencing the stability of rail transport. Transporting banana at speeds exceeding 0.58 km/h reduced mechanical damage to bunches. Excessively high speeds also increased mechanical vibrations in the track and its support. Additionally, the maximum vibration acceleration of the transport track was 43.89, 130.92, 43.61, and 165.54 m/s², respectively, at the transport speeds of 0.98, 1.16, 1.49, and 2.21 km/h. This sharp increase in vibration acceleration was attributed to the excitation amplification, whereby the load excitation frequency was close to the natural frequencies of the track and supports. Therefore, the transport speed of the device was adjusted for the load excitation frequency during operation. The natural frequency of the track was then avoided to minimize vibration acceleration for transporting banana in the device.

     

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