Adaptive fuzzy sliding mode control of spray boom active 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. 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 was designed. In view of the problems of poor performance of isolated interference body swing of spray boom passive suspension, a hydraulic cylinder is added on the spray boom passive suspension to obtain an active suspension, which can not only take advantage of the input of external energy to actively adjust the spray boom posture, but also retain the high-frequency isolation performance of the spray boom passive suspension to avoid the high frequency response of the active suspension that consumes a lot of energy. In the light of the dynamics and the hydraulic system characteristics of spray boom active suspension, the control method based on adaptive fuzzy sliding model control algorithm of boom active suspension were developed with the spray boom inclination angle as the control object and the control objectives of fast response, stability and accuracy. On the basis of the established dynamic model of the spray boom active suspension, the dynamic characteristics of the active suspension were simulated and analyzed by Matlab/Simulink, which provides the basis for the effectiveness of the control method. A real vehicle test platform of the spray boom suspension system based on high clearance self-propelled sprayers developed by the research group were built. The dynamic characteristics of the active and passive suspensions of spray boom were tested by the actual vehicle following test and field test, and the results were compared and analyzed with the simulation results of the model. The test result shows that: when adopting the active boom suspension control method based on adaptive fuzzy sliding mode control algorithm, the step response time and the following error of the boom dip angle is 2 s and 0.002 rad, which are decreased compared to PID control. In the field test, the spray boom active suspension can keep the inclination angle of the boom in the range of -0.005-0.005 rad. The results show that the active suspension control method proposed in this paper has good responsiveness, stability and accuracy, and can effectively isolate the disturbing body swing and keep the spray rod stable. The study promote the development of theory for the spray boom active suspension in China, and it is conducive to the development of the large high clearance sprayer in China. © 2018, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.