A Composite Adaptive Fuzzy Control Of Semi-active Seat Suspension For Large Tractors

Large tractor is one of the important equipment for agricultural mechanization in China.Due to the factors such as technology and cost,the vibration damping devices of the domestic large tractors are simple and crude.It is easy to produce severe vibration when it drives and works on the soil road and field for a long time,which seriously affects the drivers’ physical and mental health.The vibration of large tractors is mainly transmitted to the human body through the seat,and the use of semi-active seat suspension with good performance,high reliability,and low energy consumption is still the main research hotspot.Due to the nonlinear and uncertain factors involved in the semi-active seat suspension system of large tractors,it is easy to cause system instability during vibration,which seriously affects comfort.Therefore,establishing a reasonable semi-active seat suspension system model for large tractors,simplifying and constructing a high-precision variable damping characteristic model,and designing a robust composite adaptive fuzzy control are the key technologies to solve these problems.With the goal of improving ride comfort,this paper focuses on the design method of large tractor semi-active seat suspension system,variable damping characteristic modeling and composite adaptive fuzzy control.The main research contents are as follows:The ride comfort and constraint conditions of large tractor seat suspension system were analyzed,which provides a quantitative standard for the vibration characteristics analysis of large tractor semi-active seat suspension system based on the magnetorheological damper(MRD).The random road excitation model and the bump road excitation model were reconstructed to provide input excitations for the vibration response analysis of the semi-active seat suspension system for large tractors.Based on the spatial layout structure of a certain type of large tractor cab in China and the driving condition on the plough field,the semi-active seat suspension was designed,and a half-vehicle model of the large tractor integrated with semi-active seat suspension system was established.The parameters of the model were calculated,providing theoretical basis and data support for the selection of damper types and research on control methods for the semi-active seat suspension system of large tractors.Based on the structure and working principle of the MRD,the nonlinear dynamic characteristics test of MRD was designed and carried out.The nonlinear relationship between damping force and control current,displacement and velocity of MRD piston rod was analyzed.Aiming at the problems of multiple identification parameters,low identification accuracy,and complex identification methods of the MRD parametric model,a parameter identification method combining sensitivity analysis and fireworks algorithm was proposed.A simplified Bouc-Wen model for current control(I-BoucWen model)was established,which reduced the number of parameters to be identified by 50%,and improved the accuracy of the I-Bouc-Wen model.It lays a theoretical foundation for studying the application of MRD in the field of semi-active seat suspension vibration control for large tractors.Aiming at the problems of road uncertainty,vehicle speed uncertainty,and spring mass uncertainty in the semi-active seat suspension system of large tractors,an interval type-2 fuzzy logic control(IT2FLC)method based on acceleration driven damper control(ADDC)was proposed.The stability of the fuzzy control method was analyzed using the phase plane method.The simulation results show that with the increase of road irregularity levels,the RMS values of vertical acceleration and dynamic deflection increase parabolically.The vehicle speeds with the RMS values of vertical acceleration and dynamic deflection are concave curves,and there is a speed value with the best comfort.The spring load mass has a linear relationship with the vertical acceleration RMS values and the dynamic deflection RMS values.IT2FLC shows superior vibration reduction effect.The influence of uncertain factors on the vibration characteristics and comfort of the system is revealed,which lays a theoretical foundation for the development of composite adaptive fuzzy control.A composite adaptive fuzzy control method combining IT2FLC,sliding mode control,error specified performance control,adaptive algorithm,and model reference was proposed to ensure the robustness of the system to model uncertainties and external disturbances.The stability of the composite adaptive fuzzy control method was demonstrated using the second Lyapunov method.The simulation results show that the composite adaptive fuzzy control method has a significant vibration reduction effect on bump road excitation.Compared with passive suspension,the vertical acceleration RMS value of the seat suspension decreases by 74.03%,and the dynamic deflection RMS value decreases by 81.74%.The dynamic deflection of the suspension is greatly reduced,the probability of breakdown is fell off,the service life of the spring is improved,and the ride comfort is improved.It provides technical support for the hardware-in-the-loop simulations(HILS)validation and field trials of semi-active seat suspension systems for large tractors.The HILS test bench for large tractor semi-active seat suspension based on LinksRT was designed and developed.The feasibility and effectiveness of the semi-active seat suspension system and the composite adaptive fuzzy control method were verified.Based on the random road excitation and bump road excitation,the HILS tests of the semi-active seat suspension system was carried out.The test results show that the composite adaptive fuzzy control method shows a significant damping effect compared with the IT2FLC method and the passive suspension,reducing the vertical acceleration of the seat,the dynamic deflection of the suspension,and the probability of the suspension impacting the stop blocks.It improves the ride comfort.The effectiveness of the IT2FLC method based on ADDC and the composite adaptive fuzzy control method was verified,and the feasibility of the damping performance of the semi-active seat suspension of the large tractor equipped with MRD was tested,laying a foundation for the practical application of the semi-active control method on large tractors.