Research On Multi-state Rollover Stability Of ZTR Mower Cutting Tool Based On Parametric Model

In recent years,due to the increasingly frequent rollover safety accidents of agricultural work vehicles,their operators have caused great harm.In view of the many hidden safety hazards,this thesis selects the Zero turning Radius Mower（ZTR）as The research carrier and the test object,combined with the special working equipment equipped with the ZTR lawn mower and other factors,have conducted an in-depth study on the rollover stability of the vehicle slope,and carried out the following work:In order to accurately obtain the spatial position parameters of the center of mass of the vehicle when the ZTR lawn mower is equipped with various cutting tools of different specifications,this thesis uses the mass response method to measure and calculate the actual center of mass parameters of the ZTR lawn mower,and obtain the original parameters of the center of mass of the ZTR lawn mower;Taking several states of the ZTR lawn mower when working on a lateral ramp as an example,using modular modeling ideas,based on the quasi-static dynamics theory,a kind of predictive analysis of ZTR lawn mower instability under ramp conditions is established The parameterized mechanical model of the mower has solved the independent rollover prediction expressions of the four-wheel contact force F_MFr,F_MFl,F_MRr,F_MRlof the bare mower on the lateral slope,and the whole vehicle under different conditions is given.The establishment method of rollover prediction model.This thesis uses MATLAB to conduct a bivariate analysis of the above-mentioned theoretical rollover prediction equation,and at the same time introduces the rollover degree evaluation index—the lateral load transfer rate of the mower,and further analyzes the influence of several types of sensitive parameters on the M-LTR value.Through analysis,it is known that when the cutting tool is suspended,the change in the height of the overall center of mass h₁caused by the rising/falling of the cutting tool has a certain impact on the M-LTR trend;In the cutting tool traction state,the quality of the cutting tool G_chas a greater impact on the critical value of the vehicle M-LTR.In order to verify the accuracy of the above theoretical rollover prediction equations,based on the multi-body dynamics software ADAMS,this thesis establishes a 1:1 virtual prototype model of the lawn mower in different states and a rollover experiment platform to verify the theoretical rollover prediction model.Accuracy,and further obtained the impact of different specifications of the ZTR lawn mower on the rollover stability of the vehicle under different conditions:When the cutting tools are suspended,the critical rollover angles of the complete vehicle equipped with 1.2m and 1.8m suspension cutting tools are 41.5°and 42.6°,respectively,which are 7%and 10%higher than that of the bare car;When the cutting tool is in the traction state,the critical roll angle of the whole vehicle equipped with 1.2m and 1.8m traction type cutting tools is 42.3°and 46.8°,respectively,which are 9%and 21%higher than that of the bare car.The anti-rollover effect is more obvious than that of the suspension cutting tool,and this working condition does not affect the overall load distribution of the vehicle.Therefore,it is recommended that when designing work equipment for light agricultural or garden vehicles,priority should be given to the bottom-mounted traction structure to improve the safety of all types of vehicles working on slopes.In order to further reduce the probability of continuous rollover when the vehicle rolls over in an emergency situation,to ensure the life safety of the ZTR lawn mower driver as much as possible.In this thesis,the traditional fixed ROPS is optimized,and an ejection roll protection system is designed,and the threshold is set according to the rollover evaluation index M-LTR proposed above.Finally,based on MATLAB/Simulink-Stateflow,the realization method of its overall system logic action is proposed.