| Tumorous stem mustard is a distinctive agricultural product of China.Every year people plant more than 1.3 millon Mu of this vegetable in Chongqing,which accounts for about half of the country's palnting area.Tumorous stem mustard can be used to make the Fuling Pickle,which is one of the top three pickles around the world along with the French sour cucumber and the sour sweet cabbage.Moreover,Fuling Pickle is also one of China's three major foods for export.The harvest of tumorous stem mustard has a very strong seasonality,usually from late December to mid-February of the next years.At present,the harvest of tumorous stem mustard in hilly and mountainous areas is entirely manual,resulting in high labor intensity,low efficiency and high cost.The difficulty of tumorous stem mustard harvest has become the biggest obstacle restricting the development of tuber mustard industry.To meet the urgent demand for the development of tumorous stem mustard industry chain in Chongqing in recent years,this research displays a tumorous stem mustard cutting device suitable for hilly and mountainous areas.The main research contents are as follows:(1)According to the investigation and analysis on the requirements of planting and harvesting tumorous stem mustard and with the combination of the features of hilly and mountainous areas,an operation to complete the cutting of tumorous stem mustard's shorten stem and the lying at one time is proposed so as to solve the problem of mechanized harvesting of tumorous stem mustard.(2)Fuza 2,the main planting species of tumorous stem mustard in Chongqing area,is selected to be the research object.Its basic geometric parameters,such as shortening stem diameter,shortening stem height,tumor diameter,tumor longitudinal diameter,tumor weight and below-the-surface root length,are measured as basis parameters for the design of the cutting device.The basic mechanical parameters such as the maximum compressive strength,elastic modulus,yield stress,dynamic friction coefficient and static friction coefficient of the stem are obtained through experiment to provide data support for numerical simulation of the cutting device.(3)According to the geometric parameters of green tumorous stem mustard and with the combination of tumorous stem mustard's harvest demand,a cutting device that can work with a micro-cultivator and has the function of automatic alignment,single-line electric cutting and reversal laying was designed,alone with the cutting device's slection,design and calculation of related components.The kinematic parameters of the circular saw blade,one of the key parts,were analyzed,and the related formulas of the cutting travel,the cutting time and the sawing productivity were obtained.The mathematical model of the blade trajectory of the circular saw blade was established,and the non-leakage cutting condition of the horizontal cutting of the circular saw blade was obtained.(4)3D laser scanning technology was introduced to reconstruct the 3D shape of tumorous stem mustard.The Geomagic Studio software was applied to process the point-cloud image and to establish the 3D model of the tumorous stem mustard.A sawing model was established in ANSYS/LS-DYNA by using the related mechanical parameters obtained through the mechanical test.The finite element method is used to do numerical simulation of circular saws cutting tumorous stem mustard,and the self-made current-and voltage-acquisition system is applied to test and verify the results of the simulation.The results show that under the condition of 0.35m/s feeding speed and 800r/min sawing speed,the simulated average power of circular saws cutting tumorous stem mustard is 52.480 W,and the tested average power of cutting is 56.870 W.The relative error is 8.37%,within the allowable range.The feasibility of using the finite element method to simulate the cutting of tumorous stem mustard is proved,which lays a solid foundation for the optimization of the motion parameters of circular saw blade.(5)The feeding speed and the sawing speed were selected as the experimental factors,and single-factor experiments were carried out respectively.By analyzing the change of sawing force,the range of feeding speed and sawing speed was preliminarily selected.With the sawing speed and the feeding speed as the test factor,the test of orthogonal combination design of binary quadratic regression was designed according to the level of the initial velocity range.The regression equation between the average sawing power and the feeding speed and the sawing speed was established through the numerical simulation of the orthogonal regression combination experiment by using the finite element method.The MATLAB Global Optimization Algorithm(GlobalSearch)is used to optimize the regression equation.The results show that when the sawing speed is 78.652rad/s(751.07r/min)and sawing speed is 0.2423m/s,the average power of the round saw bladecutting is 50.6243 W.(6)The high-speed camera technology is used to record the whole process of cutting tumorous stem mustard on the self-made bench with the optimized motion parameters of circular saw blades,and to test whether the requirements of tumorous stem mustard cutting were met.The experimental results showed that: when cutting the tumorous stem mustard with optimized parameters,the whole process was smooth,the head of tumorous stem mustard was at good posture,the incision was smooth,and the stem tumor was not damaged,which satisfied the cutting requirement.According to the current-and-voltage acquisition system,the average power of cutting vegetables heads is 53.07 W.Compared with the optimized result,the relative error is 4.83% and is within the allowable range,which shows that the optimized result is of higher accuracy.The optimized average cutting power,if compared with the initial design,decreased 11.56%,which shows obvious improvement,and reached the designed requirements of tumorous stem mustard cutting device,that is,an average power less than 60 W.At the same time,high-speed camera was used to analyze the whole process of cutting and destroying tumorous stem mustard under the condition of sawing speed 500r/min and feeding speed of 0.5m/s.The conclusion is that the inertia force of tumorous stem mustard generated by low sawing speed is not enough to resist the bending and deformation that leads to tumorous stem mustard bending before finishing cutting.Under the action of bending moment,the tumorous stem mustard has a splitting trend.The lower the sawing speed,the greater the possibility of splitting.(7)On the basis of the above research and experiment,the prototype of the tumorous stem mustard cutting device was completed,and the field experiment was carried out with the 3TGQ-4 type micro-cultivator as a power machine.The results show that the tumorous stem mustard cutting device matched with the 3TGQ-4 type micro-cultivator can almost meet the design requirements and the harvest requirements of tumorous stem mustard.It can work in the narrow-row conditions with 300 mm row spacing.Tumorous stem mustard can pass the aligning part smoothly,enter the cutting channel between the cutting-knife protection boards and then been cut by the circular saw blades.It was observed that there was no relatively big damage to the tumorous stem mustard,the incision surface of the tumorous stem mustard was smooth,and the damage rate was lower than the harvest requirement,that is 15%. |
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