Structure Optimization of a Litchi Vibrator Based on Vibrational Detachment Characteristics
In order to optimize the vibrator structure based on the vibrational detachment characteristics of litchi fruit,the litchi vibrational detachment tests were carried out under different vibration distances,frequencies and amplitudes using a reciprocating vibration harvesting device.The MATLAB was used to process the litchi motion videos recorded by a high-speed camera to obtain litchi movement parameters(trajectory,speed,acceleration,etc).In order to determine the opti-mal working parameters of the vibration mechanism,the test data was processed by Design-Expert to obtain the regression model,and the effect of vibration frequency,amplitude and vibration distance on the detachment characteristics of litchi(separation time,number of collisions and inertial force)was analyzed through the response surface of influence.The re-sults from the optimized regression model showed that a short detachment time and a low mechanical damage of the fruit could be achieved when the vibration frequency,the amplitude and the vibration distance were respectively of 9.7 Hz,80 mm and 29.4 mm.In order to optimize the structure of the vibrator based on the optimal working parameters,a multi-ob-jective optimization model was established taking high harvesting efficiency and small harvesting damage as objectives,and size constraints,angle constraints and strength constraints as constrained conditions.The results showed that the optimized vibrator is a centric slider crank mechanism.Its shaker crank length,connecting rod and angular velocity were respective-ly 56 mm,127 mm,and 62 rad/s.The optimized vibrator can improve the harvesting efficiency and reduce the fruit dam-age,which lays a good foundation for the design of litchi vibrational harvesters.
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