Study On The Design And Control Methods Of Spray Boom Suspension For Large High Clearance Sprayer

The large high clearance self-propelled sprayers with the advantages of high efficiency,environmental protection and intelligentization have been widely used worldwide.The spray boom suspension system is an important part of the large high clearance self-propelled sprayer,whose structure and performance have an important influence on the stability and life of the spray boom as well as the uniformity of spray.At present,due to the lack of basic theoretical research and related technical development of stable,efficient,low energy consumption and low cost spray beem suspension systems,most of the domestic large sprayers are not equipped with spray boom suspension,and has been unable to meet the requirements of modern agricultural production for plant protection machinery.In this paper,the scheme design,system modeling,characteristic analysis and control method of the spray boom suspension system are carried out with taking a large sprayer's spray boom suspension as the research object and improving the working stability and operation efficiency of the spray boom as the target.The main research work is as follows:(1)On the basis of consulting a large number of literatures,the development status,key technologies and research methods of the spray beem suspension system of large high-clearance sprayers at home and abroad were compared and analyzed.The key scientific problems that need to be solved in the research of spray beem suspension at present were summarized.On this basis,the research contents of this paper were determined,and the implementation scheme and technical route of the paper were formulated.(2)In order to solve the problems that the spray boom is easily affected by the body swing of the sprayer to generate harmful motions such as rotation,deflection,shaking and the like,the structure and function of the existing spray boom suspension systems were comprehensively analyzed,and a two-link trapezoidal spray boom suspension system which could realize passive vibration reduction,active balance and ground profiling was designed.Based on the D'Alembert principle,the dynamic models of spray boom's passive suspension and active suspension were established.According to the simulation results of time domain and frequency domain,the influence of suspension damping and suspension structure parameters on the performance of spray boom passive suspension was analyzed,the optimization scheme of spray boom passive suspension was put forward,and the necessity of adding spray bar active suspension was analyzed.Aiming at the established dynamic model of the active suspension of the spray beem,the dynamic characteristics of the active suspension were simulated and analyzed,which provides the basis for the selection of hydraulic cylinder actuator and the control of the active suspension.(3)In view of the problems of pressure shock and energy consumption in the hydraulic system of large inertia spray boom suspension,a spray boom suspension hydraulic system based on load feedback and dynamic pressure feedback was designed.The mechanism of dynamic pressure feedback absorbing pressure shock was analyzed,and the main parameters of dynamic pressure feedback device in surface profiling hydraulic system of spray boom were matched.The mathematical model of the ground profile control valve block was established,and its profile lifting and lowering performances wer simulated and analyzed.Combined with the mathematical model of the surface profiling control valve block,the pressure impact analysis model of the spray boom surface profiling process was established,and the vibration reduction efficiency of the dynamic pressure feedback device in the spray boom surface profiling hydraulic system was simulated and analyzed.(4)In the light of the dynamics and the hydraulic system characteristics of spray beem active suspension,aiming at the problem of insufficient low-frequency performance and inability to realize ground profiling of spray beem passive suspension,the control model of spray beem active suspension was established.The control algorithms of PID,general sliding mode and adaptive fuzzy sliding mode variable structure for spray beem active suspension were developed with the spray beem inclination angle as the control object and the control objectives of fast response,stability and accuracy.The control performances of the three algorithms were compared and analyzed in the simulation analysis of active balance control.(5)An indoor test platform of the spray bar ground profiling control valve block and a real vehicle test platform of the spray beem suspension system were built.The performance of the ground profiling control valve block,the dynamic characteristics of the active and passive suspensions of spray beem and the effect of the active balance control were tested and verified from the static and dynamic response of the ground profile control valve block,the transient response of the spray bar passive suspension,the real vehicle signal following of the active balance control algorithm and the field test,and the results were compared and analyzed with the simulation results of the model.