变幅振动式林果采摘机激振机构的解析与仿真

Theoretical analysis and simulation of fruit-picking machine’s vibrator with adjustable amplitude

文中自行设计了一种新型的变幅振动式林果采摘机激振机构,即通过改变摇杆1夹角α调节振幅,以及通过改变液压马达转速ω调节激振频率,从而使林果采摘机适于采摘多种多样的林果。并且,通过解析与仿真的方法建立其运动学与动力学模型,分析了关键结构参数杆L_(2)(即曲柄长度),α和ω对臂杆的影响规律。结果表明:通过解析与仿真两种方法分别获得的位移s、速度v、加速度a及受力曲线高度吻合,表明结构设计的准确性。L_(2)过大将导致采摘臂杆出现静止不动时刻与受力急剧增大,而L_(2)过小将减小采摘臂杆的振幅调整范围,综合考虑认为L_(2)=200 mm为最优参数。通过在15°~75°范围内调整α,可以在19~371 mm范围内调节采摘臂杆的振幅,从而成功实现林果采摘机激振机构的变幅振动。当林果采摘需要大振幅时则减小α,反之则增大α。随着ω的增大,采摘臂杆的振幅不发生变化,而v,a及受力都快速增大,因此采收率达到一定程度即可,不能为了采摘极少数固有频率较大的果实而一味增大ω。

In this article,a new vibrator for fruit-picking machines with adjustable amplitude is designed.The amplitude can be adjusted by changing the rocker 1 angleα,and the vibration frequency can adjusted by changing the hydraulic motor’s rotational speedω,so that the fruit-picking machine is suitable for various fruits.Besides,the kinematic and dynamic models are set up by means of theoretical analysis and simulation,and the influence of L_(2)(crank length),αandωon the picking arm is explored.It’s shown that displacement s,velocity v,acceleration a and the force curve obtained from theoretical analysis are highly consistent with those obtained from simulation,which indicates the structural design is accurate.If L_(2) is too large,the picking arm will be stationary at a certain moment,and the force would increase significantly.If L_(2) is too small,the amplitude adjustment range of the picking arm will decrease.It’s concluded in a comprehensive manner that L_(2)=200 mm is the optimal parameter.By adjustingαin the range of 15°~75°,the amplitude of the picking arm can be adjusted in 19~371 mm,so the variable amplitude vibration of the fruit-picking machine will be achieved.The ever-decreasingαwill ensure the rising amplitude,and the everincreasingαwill cause the amplitude to decline.With the ever-increasingω,the amplitude of the picking arm remains unchanged,and v,a and the force will increase rapidly.Therefore,the picking rate should remain at a certain level;ωcannot be increased blindly in order to pick a few fruits with great natural frequency.