Mechanical analysis and parameter optimization of cabbage root cutting operation

Abstract: In order to obtain the optimal combination of cutting elements and reduce the root cutting reaction force during root cutting process, the adjustable device for root cutting was designed. The basic structure and working principle of the root cutting device were described. The device mainly consisted of connection mechanism, disconnected fixing mechanism, handle adjusting mechanism, bolt adjustment mechanism and transmission mechanism. The test platform of root cutting operation was set up. The test platform was composed of the adjustable root cutting device, the connection support frame, the chassis and the walking device, which can realize the adjustment of the cutting speed, cutting position, cutter overlap amount and pitch angle. Based on the explicit nonlinear dynamic analysis method, the numerical model of root cutting operation was established. Then, the process of cutting cabbage root with double disc cutter was numerically simulated, and the mechanical mechanism was revealed. The forces along X, Y and Z axes during root cutting were analyzed and the force Fy along Y axis was approximated to root cutting force, therefore, root cutting reaction force Fy′ was determined as the data acquisition object of tests. In order to reduce the damage of cabbage and the abrasion of disc cutter, the root cutting force Fy and the root cutting reaction force Fy′ should be reduced as much as possible. The single factor tests were carried out to obtain the influence law of single factor on the evaluation index. The second-order orthogonal rotating combination multi-factor tests were carried out to study the influence of cutter speed, cutting position, walking speed, cutter overlap amount and pitch angle on the maximum root cutting reaction force. The response surface method was used to optimize the parameters, and the mathematical model of the relationship between maximum root cutting reaction force and the factors was established. The results of the multi-factor tests showed that the optimal combination of cutting elements was cutter speed 200 r/min, cutting position 17 mm, walking speed 0.26 m/s, cutter overlap amount 22 mm and pitch angle 11°, and the maximum root cutting reaction force was -22.5 N at this time. Under the conditions of the optimal parameter combination, tests were carried out to verify the optimal results. The test results showed that the average value of the maximum root cutting reaction force was -21.8 N. The result error between the predicted value of the model and the test was 3%, which verified the credibility of the optimization model. The qualified rate of root cutting was 96%, indicating that the root cutting device and test platform designed in this paper could meet the basic requirements of root cutting. The research results can provide theoretical basis and reference for the design and improvement of root cutting device for cabbage combine harvester.