Preliminary design of straw cutting simulation test platform based on hardware-in-loop

Abstract: Straw cutting is an important process for harvesting machinery during harvest time, and the cutting performance directly determines the harvest efficiency and the maintenance cost of the machines. However, subject to the influences of the harvest time and the field terrain differences, some problems, such as nonrepeatability, poor data continuity, high difficulty, and low accuracy, exist when obtaining the cutting parameters of the harvesting machinery during experiments. Prior research has designed some experiment platforms to reduce such problems. However, these platforms require excessive consumption of the straw, and need to continuously add the experimental straw manually. This is difficult to verify the reliability of the harvesting machinery’s continuous working condition. Therefore, drawing upon these problems, an innovative spiral auger feeding system was proposed to achieve the continuous supply of materials, and a simulation analysis of material collision, movement direction and distribution inside the box was conducted using the discrete element method. Meantime, a simulation physical experimental platform was built up by combining the simulation vibration platform that simulates the field terrain differences and the vibration of the harvesting machinery and by using the hardware-in-the-loop technique. The simulation results revealed that: 1) Adding a fan-shaped blade in the bottom of the spiral auger could increase the load and perturbation area of the spiral, thus increasing the whirlpool intensity formed by materials and then facilitating the formation of continuous flow of materials. 2) The velocity of rod-shaped particles increased along with the increase in the rotation speed of the spiral auger. However, when the rotation speed of the spiral auger reaching 600 r/min, the velocity of rod-shaped particles increased sharply and unstably, which was the no-load high-speed operation situation and was inconsistent with the actual cutting process of the harvesting machinery. When the rotation speed of the spiral auger lowering 300r/min, the velocity of rod-shaped particles has not yet reached the running velocity of the harvesting machinery, which was the low-speed turning operation condition. As a result, for ideal straw feeding system, the rotation speed of the spiral auger should keep during 400-500 r/min in order to marching the harvesting machinery’s actual operation status in the field. Following these simulation results, the structure of the proposed spiral auger feeding system was optimized, and the rationality and feasibility of the design idea was also verified. In addition, according to the general vehicle traveling process simulation theory, a shaking table that simulates the walking of the harvesting machinery in the field was designed. The PLC programming software Gxworks2, the touch screen programming software SKWorkshopV5.0.2 and the configuration software kingview6.60SP1 were used for upper computer programming, and to detect and give the control and feedback signals required during the experiment. The results showed that when the speed of the spiral auger reaching 450-500 r/min and the vibration frequency of vibration table keeping 4.12?Hz, the average output torque was approximate to the actual output torque of the straw harvest in the field. That is, the working condition of the cutter was close to the real working environment of the harvesting machinery. This research can provide experimental data for the harvesting machinery design, and can also provide technical support for the current lack of agricultural machinery simulation reliability testing standards.