Design And Test Of Lightweight Chestnut Fruit Dropping Device

As a major producer of chestnut,China has the highest planting area and yield of chestnut in the world.Currently,the harvesting of Chinese chestnut in China is mainly done manually,with low efficiency,high cost,high risk,and low mechanization being the main reasons restricting the development of the chestnut industry.Most chestnuts are planted on flat land in foreign countries,and the relevant machinery is not suitable for harvesting chestnuts in hilly and mountainous areas of China.The fruit dropping device is a key component of chestnut harvesting machinery.In response to the demand for lightweight harvesting devices for chestnut in hilly and mountainous areas of China,this study designed three types of chestnut fruit dropping devices based on the separation force characteristics of chestnut fruits.The main research content is as follows:(1)Measurement of Biomechanical Characteristics of Chestnut Trees and Fruits.The target is chestnut from Hubei region.The measured tree height is about 4m～8m,the crown diameter is 2.5m-6m,the minimum ground height of the chestnut fruit is 1.6m～1.8m,the average lateral diameter of the chestnut fruit is 40mm～60mm,and the average longitudinal diameter is 40mm～50mm.The separation force between chestnut fruit and fruit stem was measured,with a maximum value of 52.8N in the 0 °direction,46.6N in the 45 ° direction,and 34.4N in the 90 ° direction.(2)Design of a tapping type fruit dropping device.Propose an overall plan.Through Kinematics analysis of the eccentric mechanism,the key factors affecting the velocity and acceleration of the beating bar’s center of mass were obtained,and the eccentricity was set to 4.5 mm.Using Adams for motion simulation analysis,it was found that the motion states of the centroids on both sides are basically consistent,meeting the stability requirements.Perform finite element analysis on key components and obtain equivalent stresses of 15.8980 MPa,1.4929 MPa,and 1.1897 MPa for the three key components,all of which are less than the yield limit.(3)Design of a multi unit rotating fruit falling device.Choose a DC deceleratio n motor as the driving device with a power of 80 W.To prevent resonance of the rack during operation,modal analysis is conducted on the rack,and the first six vibration modes are extracted in the post-processing,with frequencies of 99.139 Hz,175.52 Hz,182.27 Hz,276.32 Hz,390.62 Hz,and 468.91 Hz respectively.Perform harmonic response analysis on the rack to obtain the maximum amplitude generated near the frequency of180 Hz,and try to avoid this frequency in practical work.(4)Design of a flexible vibration fruit dropping device.The vibration unit mainly consists of a motor,a connecting shaft,and a flexible rope nail tooth assembly.The motor drives the flexible body to rotate,and the nail teeth on the flexible rope constrain the free end of the rope to achieve vibration.Using Adams for flexible body motion simulation,the flexible rope is discretized into cylinders and connected through Bushing.According to the simulation results,the vibration state is not obvious when the speed is below 200r/min,and reaches the maximum displacement vibration state in a short time when the speed is above 500r/min.(5)Analysis of tapping force and fruit drop effect experiment.According to th e tapping force bench test,the optimal material for the symmetrical eccentric tapping device is high-pressure polyethylene(LDPE).When producing a tapping force of74.15 N,the parameters are the rotational speed of 600r/min,the total length of the tapping strip of 450 mm,and the tapping angle from inside to outside of 25 °.The optimal speed of the multi unit rotating fruit falling device is 350r/min,and the average tapping force is 36.34 N.The tapping force at the end of the nail teeth of the flexible vibration type fruit dropping device decreases as the horizontal height from the ground decreases.At 400r/min,the force generated by the top nail teeth is 35.15 N.Among the three devices,the symmetrical eccentric tapping device has a better effect.Conduct field picking experiments to verify the effectiveness,set the picking time to 15 seconds,and use the fruit drop rate as the evaluation indicator.The average fruit drop rates of the two schemes are 86.5% and 83.7%,respectively,meeting the harvesting requireme nts.