关键词: 植树机, 挖穴机构, 运动学仿真, 动态性能

Abstract:

Objective: China's mechanized afforestation equipment was often ignored in soil and water conservation, vegetation protection and operation energy consumption, resulting in large surface soil breaking area, simple and extensive operation and other problems. This paper proposed a series 2-DOF tree planting and digging mechanism for big seedlings, which could realize continuous dynamic driving and interrupt digging hole afforestation. Method: According to the afforestation technical regulations and the mechanism motion rules, the kinematic model of series multi closed chain mechanism was established. Taking the driving speed, the running speed of floating cylinder and the running speed of digging cylinder as independent variables and aiming at five indexes to evaluate the shape of hole, the single factor motion performance simulation test based on ADAMS software was carried out. The motion track of digging parts was analyzed by high-speed photography. Based on the simulation test results, the field experimental research was carried out. Taking the factors in the simulation test as independent variables and taking longitudinal length of the upper end of the planting hole, the front inclination angle of the upper part of the hole and the rear inclination angle of the upper part of the hole as response values. Using three dimensional optical phase measurement technology and Box-Behnken were used for central composite design, and the interaction between various factors was analyzed. The optimization solver in Design-Expert software was used to solve the problem under the optimization criterion. Result: 1) The longitudinal length of the upper part of the hole and the inclination angle of the hole increased with the increase of the driving speed. Effect of floating cylinder running speed on the front inclination angle α, the front inclination angle of upper part of the hole αㄥ, the longitudinal length of the upper part of the hole had a great influence, and had no obvious influence on the rear inclination angle. The parameters of hole shape decreased with the increase of the running speed of digging cylinder. In the experiment, the front inclination angle of the hole was significantly greater than the rear inclination angle, and the change of independent variable had little effect on the longitudinal length of the bottom of the hole. The running speed of floating cylinder had the greatest contribution to change the longitudinal length of the upper part of the hole, followed by the running speed of digging cylinder. 2) The high-speed photography analysis result showed that the motion trajectory of the digging cutter head was consistent with the simulation trajectory, the mechanism had the characteristics of deceleration digging, and the obvious soil return phenomenon occured at the rear of the hole when the inclination angle was small. 3) The regression model of the test target was established, and the interaction of various factors on the response value was consistent with the analysis of variance. The optimization solution showed that the best operating parameters were the driving speed of 108 mm·s^-1, the running speed of floating cylinder of 19 mm·s^-1 and the running speed of digging cylinder of 80 mm·s^-1. The verification test showed that the longitudinal length of the upper part of the hole L₁ was 669 mm and the rake angle of the upper part of the hole α′ was 33.1°, and the caster angle of the upper part of the hole β′ was 24.5°. Conclusion: All indexes met the relevant requirements of afforestation regulations. This study provides a new method for big seedling mechanized afforestation and a reference for the development of ecoplanter.

Key words: tree planter, digging mechanism, kinematics simulation, experiments