Desigh And Research Of The Automatic Harvesting Machine Of Hydroponic Lettuce

Lettuce as one of the three major hydroponic vegetables,its planting area and output value have been rapidly increased under the strong support of the national government departments in recent years.At present,the harvesting of hydroponic lettuce mainly depends on manual work,which is tedious,time-consuming,labor-intensive.The cost increasing.With the continuous development of science and technology,the mechanized operation of agriculture will replace manual work gradually to increase the level of modern agricultural operations.So,it is of great scientific value and practical significance to research the automated harvesting of hydroponic lettuce.In this paper,butter lettuce cultivated by Deep Flow Technique in glass greenhouse were used as research object.In order to achieve automatic harvesting of lettuce,the following four aspects were conducted:(1)Study on the physical and mechanical property of hydroponic lettuce and the effect of different root lengths on its preservation performance.The physical parameters and mechanical properties parameters of hydroponic lettuce are the theoretical basis for the design of the harvesting machine.Firstly,the distribution of the main physical and mechanical parameters,including the unfolding degree,the overlap degree,and the plants height,root length,root diameter,total mass,and quality after root-removal were explored through field tests and mathematical statistical analysis methods.Secondly,the moisture content of roots,stems and leaves of lettuce was measured using the direct drying method.Then,the universal testing machine was used to explore the cutting force at different cutting sites and different cutting speeds,providing theoretical basis for design of the root cutting device.In order to study the effects of different root lengths on the fresh-keeping performance of hydroponic lettuce,four indexes including changes in relative chlorophyll content,changes in color of lettuce leaves,weight loss rate,and sensory quality were analyzed and studied,it is concluded that keeping the lettuce root length 9cm is good for lettuce preservation.(2)The overall plan for the automatic harvesting machine of hydroponic lettuce.The harvesting method of lettuce and the transportation method of the planting board are the key for the design of the harvesting machine.Firstly,combined with the way of artificially harvesting lettuce,some preserving-root lettuce were harvested in order to reflect the hydroponic characteristics of it.Secondly,for the transportation method of the planting board,taking into account that continuous harvesting will cause great damage to the lettuce,three major components of intermittent harvesting such as the setting board conveying mechanism,the root cutting mechanism and the lettuce pulling and carrying mechanism are carried out in detail.The analysis and program selection will eventually complete before the overall design of the automatic harvesting machine was finished.(3)Design and control system for harvest machine of hydroponic lettuce.In order to achieve automatic harvesting of hydroponic lettuce,firstly,combine the characteristics of the object to be harvested,the three major components of the harvesting machine,the planting board conveying mechanism,the root cutting mechanism and the lettuce pulling and carrying mechanism,are selected for the key parts design,with the parameter design and trials for each institution.Secondly,the control system of the machine is designed,including hardware selection and software design of the control system.Online debugging and running of hardware and software are performed according to the software and hardware work-flow of the control system,the test results show that the control system completes one recovery action every 21 s.If the sensor is not detected in the 3 cycle,the control system stops running,so the design requirements of the control system are achieved.(4)The prototype of the Hydroponic Lettuce automatic harvesting machine was completed.In order to verify the effect of the prototype and further optimization,performance evaluation tests of the prototype were carried,the test results showed that the success rate of root cutting was 82%,the success rate of pulling and carrying was 85%,the operation efficiency was 7.7s,and the prototype could meet the expected design requirements.