Optimization of cutting position and mode for cabbage harvesting

Abstract: Development of a cabbage harvester is an efficient approach to change the traditional way of harvesting cabbage in China. Since cutting is the crucial process, the cutter design is one of the key techniques for the development of cabbage harvester. In order to obtain the best cutting position and cutting combination, taking the cabbage roots as the experimental materials, cutting property tests and chemical composition detection were carried out respectively. The maximum cutting force and average cutting force were taken into consideration as cutting properties. Load-displacement curves on different diameters were sampled depending on the designed test apparatus when the cutting combination was set constantly as two-point support, vertical cutting and the cutting speed of 100 mm/min. The moisture content and crude fiber content, which are the main chemical composition of cabbage root, were measured on the same diameters according to standard process. The relationships between cutting forces and chemical composition were analyzed. The results demonstrated that the maximum cutting force and average cutting force can be fit with the quadratic polynomial of diameters, and F values of the two equations reached to 251.67 and 360.62 respectively and coefficients of determination (R2) were 0.9636 and 0.9743 respectively. Both the curves declined as the cutting diameters increased and got the lowest when the diameters ranged from 30-35 mm which would be the best cutting position. From the space structure of cabbage root, it's also the most suitable cutting position that is 10-15 mm above the bottom leaves. Multiple linear regression (MLR) was applied to establish the relationships of maximum force, average force with crude fiber content. The results proved that the main factor affecting cutting properties is crude fiber content. Mixed levels orthogonal table (22×32) was utilized to conduct the orthogonal test to obtain the best cutting position considering the factors of support mode, cutting mode, inclining mode and cutting speed which should be determined on the basis of the cabbage harvester designed previously. In the orthogonal test, there were 9 tests and 5 repetitions were conducted for each test. The maximum force and average force were obtained from the load-displacement curves. The orthogonal test results showed that: 1) Support mode and cutting speed had significant influences on maximum cutting force and average cutting force, cutting mode had significant influence on maximum cutting force but had no influence on average cutting force, and inclining mode had no influence on maximum cutting force or average cutting force. 2) Based on index minimality of maximum force and average force, the best cutting combination was under the conditions of single point support mode, sliding cutting mode, downward inclining mode and the low cutting speed (50 mm/min). This research can provide a reference for design of the cabbage harvester cutter and optimization of cutting combination.