a b s t r a c tMethod of manual removal of produce from the field has been a bottle-neck for lettuce production in Japan. In order to reduce the production cost of this fresh commodity, a prototype harvester has been developed for head lettuce production. The harvester consists of a cutting component to slice the lettuce head at the desired location and a lifting component that transports the harvested produce from the cutting site onto elevating conveyor and trimming station. A cutting component with reciprocating blade was proposed.Laboratory tests were performed to verify ability of reciprocating blade to slice lettuce stump at forward cutting speed of 0.1 m/s, reciprocating stroke of 18 mm, and different reciprocating frequencies of 2, 4 and 6 Hz. In addition, power requirement for reciprocating the cutting knife as slicing two lettuce stumps was measure. Tests in lettuce fields were also conducted at different working speed to investigation the cutting and lifting performances of the harvester mounted with the reciprocating-blade cutting component. The results of laboratory tests indicated that the cutting component could smoothly cut lettuce stumps and the maximum cutting torque and cutting power requirement were 0.73 Nm and 27.7 W, respectively at 6 Hz reciprocating frequency. Field test results showed that the harvester could cut and lift the lettuce heads without damaging and blemishing the produce at working speed of 0.04 m/s and the commercial head percentage was 94.5%. At higher working speed of 0.08 m/s, the head damage rate was 12.8% reducing the percent of commercially accepted heads to 87.2%.
In order to high work performant for compliant mechanism about motion scope, work long term and high frequency. Therefore, in this investigation displacement, maximum principal stress and the first modal shape frequency were analyzed by Finite element analysis (FEA) for a magnification mechanism to find out effects of design variables on magnification ratio of this mechanism. The FEA outcomes indicated that design variables have significantly affected on magnification ratio, maximum principal stress and the first modal shape frequency of a magnification mechanism. The magnification ratio obtained 42.83 times thereby maximum principal stress is equal to 132.79 MPa and the first modal shape frequency is equal to 377.44 Hz, respectively. The forecast results by the Taguchi method achieve a displacement of 0.4392 mm, and according to this method the optimal structure has a displacement of 0.4451 mm with the dimensions of the following variables: variable A is 0 mm, variable B is 23 mm and C is 60 mm, the parameters combine at the levels A1B2C1. This structure amplified 44.51 times, this result is a good agreement compared with the forecast results, the error compared to the forecast is 1.33%.the forecast results, the error compared to the forecast is 1.33%.
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