Journal of Jilin University(Engineering and Technology Edition) ›› 2021, Vol. 51 ›› Issue (5): 1908-1918.doi: 10.13229/j.cnki.jdxbgxb20200434

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Rollover stability of zero turning radius lawn mower based on parametric model

Xin-yan WANG(),Quan JIANG,Feng LYU,Zheng-yang YI   

  1. College of Mechanical Engineering,Jiangsu University of Science and Technology,Zhenjiang 212001,China
  • Received:2020-06-17 Online:2021-09-01 Published:2021-09-16

Abstract:

In response to frequent rollover safety accidents on the transverse slope of the zero turning radius lawnmower in recent years, based on the quasi-static dynamics theory, a parametric mechanical model that can predict and analyze the instability of the ZTR lawn mower under ramp conditions is established. According to the actual working state of the mower, the driver factor and the influence of different specifications of cutting tools on the vehicle rollover stability under the suspension and traction state are added. The theoretical rollover prediction equation was solved using Matlab, and the relationship between the lateral load transfer rate of the lawnmower (M-LTR) and its rollover sensitive parameters was analyzed under different working conditions. Using ADAMS to conduct multiple sets of simulation experiments on the lawnmower, further verify the accuracy of the parameterized model. Through experiments, it is found that the traction cutter at the bottom of the lawn mower has stronger anti-rollover performance than the suspension cutter: the critical roll angle of the 1.2m and 1.8m suspension cutters is increased compared with the bare car about 7% and 10%; with 1.2m and 1.8m and specifications of the vehicle with traction cutting the critical roll angle are improved compared with naked car about 9% and 21%. According to this characteristic, it is recommended that when designing working instruments for agricultural or garden vehicles, priority is given to the bottom center traction structure to improve the safety of various vehicles working on slopes.

Key words: agricultural engineering, zero turning radius lawnmower, parametric mechanical model, rollover prediction equation, mower cutter, anti-rollover performance

CLC Number: 

  • S224.1

Fig.1

Lateral diagram of ZTR lawn mower"

Fig.2

Simplified mechanical model mower rollover"

Table 1

Interpretation of related symbols"

符号参数含义

FMFl/N

FMFr/N

FMRl/N

FMRr/N

Fr/N

Ff/N

Fc1/N

Fc2/N

Gm/N

Grx/N

Gfx/N

Gc/N

Gp/N

左前轮与地面接触力

右前轮与地面接触力

左后轮与地面接触力

右后轮与地面接触力

车体施加在后轴上的总力

车体施加在前轴上的总力

割具右侧小轮与地面接触力

割具左侧小轮与地面接触力

车体所受重力

后轴所受重力

前轴所受重力

割具所受重力

驾驶员所受重力

Fig.3

Schematic diagram of centroid projection"

Fig.4

Main frame simplified force model"

Fig.5

Theoretical rear axle simplified force model"

Fig.6

Theoretical front axle simplified force model"

Fig.7

Center of mass relationship between cutting tool and car body"

Fig.8

Ramp traction mower with cutting conditions"

Fig.9

Schematic diagram of equivalent slope angle"

Fig.10

Displacement trend of hanging cutter on COG"

Fig.11

Effect of α-Lx-M-LTR change on 1.2 m mower"

Fig.12

Effect of α-h1-M-LTR change on 1.2 m mower"

Fig.13

Traction cutters influence the trend of α-Gc-M-LTR"

Fig.14

Comparison of M-LTR values of various mowers"

Table 2

Structure parameter table of lawn mower"

参数符号含义数值

L/m

a/m

b/m

Ly/m

Lx/m

L′/m

Lp/m

h1/m

hp/m

Ra/m

Rb/m

β/(°)

Grx/N

Gfx/N

Gm/N

Gp/N

Gc/N

车体前、后轴之间距离

前车轴轴长的一半

后车轴轴长的一半

y向车架质心到后轴中心距离

x向车架质心到后轴中心距离

x向割具质心到前轴的距离

x向人体质心到后轴的距离

z向车架质心到后轴中心距离

z向人体质心到后轴中心距离

前轮半径

后轮半径

前、后轴差角

后轴所受重力

前轴所受重力

车体所受重力

驾驶员所受重力

割具所受重力

1.27

0.43

0.46

0.02

0.23

0.49

0.35

0.67

0.85

0.15

0.24

1.39

708.54

271.46

2669.52

761.46

962~1425

Fig.15

Real vehicle test model of lawn mower"

Fig.16

Experimental model of lawn mower rollover platform"

Fig.17

Comparison of theoretical prediction curve and experimental curve"

Fig.18

Curve of contact force of front wheel of car body with cutter head suspended"

Fig.19

Curve of contact force of rear wheel of car body with cutter head suspended"

Fig.20

Contact force curve of car body front wheel under cutting tool traction"

Fig.21

Contact force curve of car body rear wheel under cutting tool traction"

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