| The trimming and maintenance of hedgerows is the focus of today’s urban landscaping work,however,it mainly relies on manual pruning at present,with large workload and high labor intensity.Therefore,it is necessary to improve the automation level of hedge pruning machinery,which can not only save labor cost and achieve efficient operation,but also meet the requirements of industry 4.0 and made in China 2025.The paper analyzed the functional requirements of the manipulator firstly,and on the basis of previous studies,combined with the structural characteristics of industrial robots,five degree freedom trimming manipulator mechanism is proposed,and has completed the 3-D model of the pruning machine through Solidworks 3-D design software.Then,the linkage coordinate system has been established based on modified D-H matrix theory,and the forward and inverse kinematics equations of the hedge trimming manipulator were deduced.Furthermore,the results of the forward and inverse analysis were verified via the Robotics Toolbox in MATLAB,the results prove the correctness of the kinematics analysis.In addition,the simulation analysis of the manipulator’s workspace was carried out by means of Monte Carlo method.The simulation results show that the manipulator has a wide coverage and a large pruning range,and its workspace is consistent with the functional requirements summarized above.and there is not cavity and void in workspace,which testify the design of manipulator mechanism is reasonable and feasible,and it also could satisfy the needs of hedge trimming maintenance.The modeling characteristics of hedgerow plants in different environments were summarized through field investigation of urban roads,park districts and expressway greenbelts.Firstly,the paper studied the transmission mode of the cutting tool,and putted forward two transmission schemes.Through comparative analysis and reference to practical pruning experience,from the perspective of cutting quality and motor heat dissipation,we choose one of them as a feasible scheme.Next,according to the characteristics of the hedgerow modeling summarized previous,two sets of modeling tool rest mechanism were designed,and the design scheme of the tool rest with changeable modeling is finally determined through analysis and comparison.Then the test platform was built based on the designed modeling tool rest.According to the mechanism characteristics of the modeling tool rest and the actual situation of hedge pruning,the orthogonal tests of five factors and four levels were carried out.Through the test,we obtained the primary and secondary order of the factors affecting the pruning effect,as well as the optimal combination of each factor level.Under the optimal condition,the parameter information of cutting force of the cutter in the pruning process have been measured by use of the tension and pressure sensor and Donghua DH3818 Y stress tester.The rigid body dynamics simulation analysis of the whole machine is carried out via ADAMS software.It is mainly through the simulation of the pruning process of the mechanism in the horizontal,sphere,and high hedgerow to obtain the force and moment of each joint of the mechanism in different postures,which provides data support for the selection of driving elements in the following chapters.At the same time,no interference phenomenon was found in the simulation process,indicating that the design of the mechanism is reasonable and reliable,which can meet the actual requirements of the hedge pruning.Then,the load condition of the trimmer under the three shapes pruning process was analysised.On this basis,the sliding platform,base,boom,tilting mechanism,rotation mechanism,and tool rest had structural statics analysis through ANSYS Workbench,to ensure that the trimmer has sufficient stiffness and strength under different pruning attitudes.Mechanical analysis to ensure that the mechanism has sufficient stiffness and strength in different postures.Next,on the basis of statics analysis,the steady-state response analysis of the modeling tool post mechanism under the action of sinusoidal excitation load has been carried out,and its frequency response curve was obtained,and according to the results of harmonic response analysis the tool post mechanism was optimized.Then a fatigue analysis was carried out on the drive shaft of the tool to ensure that it would not suffer fatigue damage during high-speed rotation.Finally,the rotor dynamics analysis of the drive shaft system is carried out to analyze its critical speed to ensure that the tool will not be damaged by resonance during the trimming process.According to the results of the previous analysis,the drive components of the pruning machine have had been selected,and the actual physical prototype have been processed and assembled,and then the three shapes of horizontal,sphere,and high hedgerow were tested and verified.The results suggest that the manipulator moved flexibly and coherently during the pruning process,with a large working space,and can fulfill the functional requirements summarized in Chapters 2 and 3.Compared with manual pruning,the work efficiency has been greatly improved,which can meet the actual needs of hedge trimming,and also provide a reference for subsequent related research. |
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