Abstract:
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 15.33 s, the rotation speed of the chopping cylinder was 515.68 r/min, and the periodic grinding capacity was 0.045 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.