青贮玉米收获机平板式动刀自动磨削装置及控制系统设计与试验

针对目前国产青贮玉米收获机手动磨削动刀操作复杂,耗时耗力,磨削精度与质量不理想等问题,该研究设计了一种由“油缸双向移动+链轮链条”组合增程移动机构和“棘轮+磨石”微量进给机构（磨石机构）组成的自动磨刀装置,开发了基于多传感器信息融合的自动磨刀控制系统,实现磨石自动均匀往复磨削及微量进给。以人字形平板式动刀为研究对象,搭建了青贮玉米收获机的自动磨刀试验台,阐述了工作原理。以磨削周期用时、滚筒转速和周期磨削量为试验因素,以滚筒平均功耗和平均磨削力为试验指标,采用Ansys workbench开展响应面磨削仿真试验,并利用Design-Expert 10.0进行多目标寻优。仿真结果表明,对滚筒平均功耗和磨石平均磨削力影响由大到小的因素依次均为滚筒转速、周期磨削量和磨削周期用时;最优参数组合为磨削周期用时15.33 s,滚筒转速515.68 r/min,周期磨削进给量0.045 mm;各影响因素变化对磨石平均磨削力的影响较小。圆整磨削周期用时、滚筒转速、周期磨削进给量为15.5 s、516 r/min、0.044 mm进行台架试验,得到滚筒平均功耗为5.53 kW,与仿真优化结果的相对误差为7.86%,表明仿真模型可靠;磨石往复运动控制准确性试验表明,该装置最高磨削周期控制相对误差为4.25%。台架试验验证了自动磨刀装置的合理性、控制系统的精确性以及磨削仿真试验的准确性。该研究填补了国产青贮玉米收获机自动磨刀技术的空白,研究结果可为自动磨刀装置的优化设计提供参考。

Design and experiments of the automatic grinding device and control system for the flat moving blade of silage maize harvesters

The silage industry has been greatly developed under the promotion of national policies and healthy demand in recent years. However, the key technology of self-grinding is still lacking in a silage harvester, as the development of mature markets increases significantly in China. A manual blade grinding device at present cannot fully meet the harsh requirement of silage harvesters in precise agriculture. In this study, an automatic self-grinding device with a precise control system was designed to grind the moving blades in a silage harvester with a plate-type chopping cylinder, indicating the lower power consumption, higher efficiency, and accuracy during operation. Two components were divided into the combined range extension and moving mechanism with a two-way cylinder and chain drive, and the micro feed mechanism with a ratchet and grindstone. A moving pulley was adopted to shorten the two-way cylinder block travel, where a pair of sprockets were mounted on the cylinder block, and the upper chain was fixed on the frame. As such, the micro feed mechanism that fixed on the chain was driven to move back and forth, when the sprockets moved with the two-way cylinder block. The ratchet of the micro feed mechanism impacted each time on the pawl that mounted on the side plate, where the grindstone fed a tooth downward, according to the threaded feed. A systematic investigation was also made to explore the technology and theory of reciprocating grinding motion and micro uniform feed. The external dimension and motion parameters of the self-grinding device were evaluated accurately, according to the structure and movement characteristics of the plate-type chopping cylinder. Three main factors were determined on the power consumption and grinding force, according to the movement and force action of the grindstone mechanism. The specific range of each factor was also calculated for the key experimental parameters during the actual operation. A three-factor quadratic regression orthogonal rotation design was applied to simulate the grinding process using the finite element method (ANSYS), where the experimental factors were the grinding cycle time, the rotation speed of chopping cylinder, and periodic grinding capacity, whereas, the indicators were the cylinder average power consumption, and average grinding force. Design Expert 10.0.1 software was used to analyze the significance of the regression model on simulation experimental data. A regression model was established between the cylinder average power consumption and average grinding force under experiment factors. The results showed that the primary and secondary order of experiment factors affecting the cylinder average power consumption and average grinding force was the rotation speed of the chopping cylinder, the periodic grinding capacity, and the grinding cycle time. An optimal combination of operation parameters was achieved when taking the minimum power consumption and grinding force as the optimization target. Specifically, the cylinder average power consumption and average grinding force reached the minimum of 5.02 kW and 618.28 N, respectively, when the grinding cycle time was 15.5 s, the rotation speed of the chopping cylinder was 516 r/min, and the periodic grinding capacity was 0.044 mm. A self-grinding test bench in a silage harvester plate-type chopping cylinder was constructed to verify the structural reliability of the self-grinding device, grinding optimization, and the accuracy of grindstone reciprocating motion control. A control system of the self-grinding device using multi-sensors was then designed to real-time adjust the rotation speed of the chopping cylinder, grinding cycle number, and cycle time. Data acquisition was designed to collect, storage and real-time analyze the signals of chopping cylinder torque using a dynamic torque sensor. A validation test was carried out under the optimal working parameters, where the cylinder average power consumption was 5.53 kW, while the relative error was 7.86% between the simulated and experimental values. It infers that the bench experiment was basically consistent with the simulation. Correspondingly, the maximum grinding control relative error was 4.25% in the control system of grindstone reciprocating motion, when the grinding cycle time was 8 s,. The finding can provide strong theoretical and technical support for the optimal design of a self-grinding blade device in a silage harvester.