# Multibody Dynamics Simulation and Vibration Test for High Clearance Orchard Sprayer
## 2 Materials and Methods  
### Machines and Modeling  
The large across-rows orchard sprayer was designed to improve the efficiency of grape orchard operations. In this paper, the safety of the sprayer was tested by finite element simulation test and vibration test. The large-scale orchard sprayer is mainly composed of a frame, spray boom, engine, cab and spray system, as shown in Figure 1. The machine size is 4600 \(\times\) 2600 \(\times\) 3000 mm, the wheelbase is 2200-3400 mm, the water tank on the left and right of the frame has a capacity of 600 L and the clearance from the ground is more than 2200 mm. The orchard sprayer adopts liftable cab, engine in the middle, spray rod in the rear, medicine box installed on both sides of the frame. The sprayer adopts 100 horsepower engine, mechanical four-wheel drive, equipped with hydraulic four wheels steering system, reducing the turning radius. The orchard sprayer adopts a gantry frame and can adjust wheelbase freely through hydraulic cylinder.  
Due to the large number of components and complex structure of the sprayer frame, it is necessary to simplify the imported model. In order to reduce the computational effort, the model is processed by extracting mid-surface and converting solid units to face units.  
The frame of a sprayer machine is an assembly composed of parts connected to each other, and there are mutual motion relationships between the parts, and the mutual motion relationship between the parts has a very important influence on the results of stress and strain. Therefore, when building the finite element model of the sprayer frame, it is necessary to consider the relative motion relationship existing between the parts of the frame assembly. The main structure of the frame is mainly connected by welding, and the contact method between each member is set to bond, and the parts with rotating relation are set to revolute, and the friction coefficient is set to 0.02.  
The mechanical movement of the whole sprayer frame is mainly controlled by the hydraulic boom. However, in the process of sprayer movement, the hydraulic boom is in the locked state and there is no relative movement at both ends of the hydraulic boom. Therefore, the hydraulic boom in the frame is simplified to a large stiffness spring of 20,000 \(\mathrm{N/mm}\). The material of the frame studied in this paper is Q345 structural steel, and the specific parameters are shown in Table 1.  
The frame of the sprayer belongs to a thin-wall structure. That is, the characteristic size thickness, and length differ greatly. The main analysis parts of the frame were extracted and the solid element was converted into the shell element. The final simplified finite element model of the sprayer frame is shown in Figure 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Materials** & **Density** & **Elasticity Modulus** & **Poisson’s Ratio** & **Yield Strength** & **Elastic Limit** \\ \hline Q345 & 7850 kg/m\({}^{3}\) & \(2.06\times 10^{11}\) Pa & 0.3 & 345 MPa & 470-630 MPa \\ \hline \end{tabular}
\end{table}
Table 1: Material properties of Q345.  
Figure 1: High Clearance Sprayer solid diagram and mapped 3D diagram. (**a**) is the high clearance spray machine prototype; (**b**) is the high clearance spray machine model.  
Figure 2: The color structure in the Figure is the part where the shell element is used in the simulation analysis of the sprayer.  
As the bearing structure of the sprayer, the main parts of the sprayer are installed on the frame. The sprayer in the operation of the driving process of the working conditions is mainly full load bending, extreme twisting two.  
The load of the sprayer frame mainly includes the weight of the cab, the weight of the power system, the weight of the front and rear axles, the weight of the diesel tank, the weight of the hydraulic tank, the weight of the liquid tank (full liquid), etc. The details of the individual parts of the chassis are shown in Table 2.