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割台前置式果园除草机器人设计与试验

Design and testing of a cutter-front orchard weeding robot

  • 摘要: 针对果园化学除草破坏土壤生态系统、影响果树健康与果品质量,长期使用易使杂草产生抗药性,严重制约果园可持续发展的问题,本研究提出一种适用于果园机械除草的割台前置式果园除草机器人。结合果园作业环境与割草作业要求,设计了增程式混合动力驱动系统、履带行走系统、除草电机过载保护系统等。通过运动学和动力学分析,对割刀参数进行优化以提升作业效率与稳定性。利用虚拟样机技术与 EDEM 离散元法,构建基于Bonding V2粘结颗粒模型的杂草、土壤、刀具的多相耦合仿真模型。运用 Design Expert 软件设计了三因素三水平正交试验,结合响应面优化分析,探究不同刀片排列方式、割刀转速及刀轴高度及其交互作用对漏割率的影响,建立漏割率回归模型。仿真结果显示,当刀片采用双螺旋排列,转速为 2286.246 r/min,割刀轴高度为 189.823 mm时,除草效果最优,预测漏割率仅为 4.154%。进行田间试验对设计的有效性与仿真优化结果进行验证,在圆整优化参数组合下,机器人实际除草漏割率为 4.77%,与仿真预测值接近;割茬高度稳定性系数大于 90%,割幅利用系数均值高于 90%。割台前置式果园除草机器人采用Y型甩刀切割方式,对土壤扰动小,能有效保护表层结构;具备除草电机智能过载保护功能,有效降低除草电机因过载发生故障的概率;履带底盘适应复杂地形,增程系统续航能力达8~12h,在作业性能和除草效率上表现优异,可为解决果园化学除草难题提供高效环保的机械化方案,可为果园除草装备的进一步优化与应用提供理论支撑。

     

    Abstract: Conventional chemical weeding has seriously threatened the sustainable orchard in recent years, such as soil ecosystem degradation, water contamination, and herbicide-resistant weeds. In this study, a cutter-front weeding robot was designed, optimized, and evaluated for efficient, environmentally friendly, and reliable mechanical weeding. A robotic platform was also provided for the weeding practices. An extended-range hybrid system (lithium iron phosphate battery + diesel generator) was provided for the 8-12 h powertrain during operation. A crawler system with the optimal parameters was utilized for the low ground pressure and gradability. An intelligent overload protection was also featured for the weeding motor and Y-shaped flailing blades. A virtual model was developed to simulate the blade-soil-weed interactions using EDEM software. A three-factor and three-level response surface experiment was conducted to investigate the blade arrangement, cutter speed, and height versus the missed cutting rate. The analysis of variance (ANOVA) was finally evaluated on the performance under the optimal parameters. The results demonstrated that the rotational speed of the cutter shaft was the statistically most significant influencing factor on the missed cutting rate, followed by the cutter shaft height and the blade arrangement pattern. The optimal combination of the parameters was achieved to minimize the missed cutting rate: a double-helix blade arrangement, a rotational speed of 2 286.246 r/min, and a cutter shaft height of 189.823 mm. Field experiments were conducted to validate the exceptional accuracy of the model under the optimal combination. The average actual missed cutting rate was recorded as only 4.77% during field trials. There was a very close agreement with the prediction, indicating a better overall optimization after simulation. Beyond the primary metrics, the operational performance of the robot was exceptional over the rest indicators. The stubble height stability coefficient consistently exceeded 90%, indicating a highly uniform cutting height over undulating terrain. Similarly, the average cutting width utilization coefficient was measured to be greater than 90%, indicating the effective working width despite ground irregularities. The crawler chassis provided stable and reliable traction during experiments, even on the loose and uneven orchard surfaces. The intelligent overload protection system performed best during tests, such as the sudden load increase, due to the entanglement with the dense vegetation or impact with concealed solid obstacles. Current sensor data was filtered to successfully discriminate between transient fluctuations and genuine overload conditions, thus triggering the electro-hydraulic lift mechanism to raise the cutter head promptly and then prevent motor stall or damage. The robustness and autonomy of the system were significantly enhanced after optimization. Lastly, the Y-shaped blade cutting mechanism was operated with high efficiency. The clean cuts of various weed species were achieved for minimal soil disturbance, thereby effectively preserving the topsoil structure for the less damage to tree roots. In conclusion, the cutter-front orchard weeding robot demonstrated as a high-performance and ecologically sound alternative to conventional chemical weeding. There was high weeding efficiency, minimal environmental impact, and reliable operation under orchard environments. As such, the mechanical optimization, numerical simulation, and field experimental validation can be expected to develop the intelligent equipment in modern agriculture. Subsequently, a closed-loop control system can also be developed to enhance the adaptability for the very short weeds in the real-time terrain. The cutting consistency can also be improved to integrate the advanced autonomous navigation and obstacle avoidance, in order to achieve full operational autonomy.

     

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