Research On Design Methods And Characteristics Of Independent Strut Type Air Suspension System For High Clearance Sprayer

Large-scale high clearance self-propelled sprayer plays a very important role in promoting the food security production and stable development of agriculture in China.Due to the lack of systematic research,especially the lack of basic theoretical research of chassis suspension,the sprayer designed in China has such disadvantages as low speed,poor comfort,and low working quality and efficiency.Therefore,this research has done lots of work to improve the independent strut type air suspension system for the large-scale high clearance self-propelled sprayer,such as the designing process,model establishment,characteristic analysis and control method.The research has been done based on the operating characteristics of the plant protection machinery,considering the requirements of the domestic and foreign suspension systems in the sprayer chassis as well as the difference from other types of vehicle suspension.The main research work of this paper are as follows:(1)Firstly,the development trend,key technologies and research methods about the large-scale high clearance self-propelled sprayer at home and abroad were analyzed,according to a large amount of literature.Then the technical parameters of their suspension systems were summarized.Following this,the main problems in designing and researching process of the sprayer suspension were proposed.Finally,the research contents and the main technical route of this paper were put forward.(2)Based on the complex operating conditions and unique operating characteristics of the large-scale high clearance self-propelled sprayer,two kinds of independent strut type air suspension system were designed.The comparison of their advantages and disadvantages was carried on,and their main components were selected and mechanically analyzed.In addition,to meet the adjusting requirements of the clearance and wheel-track,the adjustable track structure and the suspension system were preliminarily designed and discussed.Subsequently,the overall layout of the sprayer was designed and analyzed,establishing the foundation for the follow-up development of the sprayer.(3)With the theoretical analysis of the suspension,the model of air spring with auxiliary chamber,analysis model for air spring height adjustment,nonlinear time domain model under road irregularity excitation for wheels,mathematical model of independent strut type air suspension and vertical dynamics model of the overall machine were established,according to the designed independent strut type air suspension system with auxiliary chamber.It provided support for the further research of vertical vibration characteristics and the design of controllers.(4)Based on the established model of air spring with auxiliary chamber,the relationship between its static stiffness and chamber volume was simulated and analyzed.Then the influence of the parameters such as excitation amplitude,frequency,orifice diameter and chamber volume on the dynamic stiffness and damping was researched.Considering the variable sprung quality,the damping and frequency of the air suspension with auxiliary chamber were identified,and some methods and advices were provided for the damping controlling.Finally,through the comparison of simulation and experiment,the vibration characteristics of independent strut type air suspension system with forms of air damping and friction damping were studied,and it was proved that the suspension system with auxiliary chamber based on the air damping was more suitable for the vibration requirements of the large-scale high clearance self-propelled sprayer.(5)With the traditional suspension control methods,both the vehicle road-friendliness and the ride comfort could not be taken into account.Moreover,the machine load was varied in a wide range during the processes of drug loading and spraying.At the same time,the load might be unbalanced when the sprayer was running.To deal with the above problems,the control strategy and algorithm of the air suspension in the sprayer were developed,with the target of promoting the ride comfort,handling stability and road friendliness,considering the control objects as suspension damping,body height,body posture and etc.Simultaneously,the control strategy and algorithm were simulated and verified.The research plays an important role in improving the ride comfort of the sprayer and reducing the vibration of body and spray bar caused by the uneven ground.Therefore,the spraying quality could be ensured and the service life of spraying arm could be extended.Meanwhile,the research can serve as a technical reference for the further design and development of the sprayer suspension system in China.