# Design and Testing of an Intelligent Control System for Maize Picking Harvest
## 2 Materials and Methods
### Software Algorithm
#### 2.2.2 Data-Based Prediction Model  
Preceding studies used experimental data-based models to gather considerable knowledge about the working principles of the maize picking process. The main influencing factors of the maize picking process are the rotational speed of the pulling rollers, operating speed, header height, clearance between the picking plates, crop characteristics, structural characteristics, and material properties of the maize picking components. Several scholars have obtained the influence degree and law of each factor through bench tests or field tests [24; 25; 26]. For plate-type mechanisms, the collision speed between the ears and picking plates directly affects the maize picking loss [27]. Thus, the most important factor that affects the maize picking process with plates is the rotational speed of the pulling rollers. Regulating the rotational speed of the pulling rollers is particularly important for the harvesting process. Second, the operating speed should match the rotational speed of the pulling rollers to ensure a proper feed rate. The header height determines not only the falling height of the ears before they collide with the picking plates but also the angle of the collision. Thus, the header height should also be adjusted. When the same variety of maize is grown in a given plot, the clearance between the picking plates is fixed and thus should not be adjusted during the harvesting process. In the present study, a data-based model was used to predict the maize picking loss rate, and the rotational speed of the pulling rollers, operating speed, and header height were optimized to minimize the maize picking loss.  
Experiments verified that the rotational speed of the pulling rollers and operating speed have the following relationship with maize picking loss rate. Figure 5a shows that the maize picking loss rate is relatively low when the rotational speed of the pulling rollers is within 900-1180 r/min. Figure 5b shows that the maize picking loss rate is relatively low when the operating speed is within 6-8 km/h. Figure 5c shows that the maize picking loss rate is relatively low when the header height is within 795-835 mm, except for low cutting mode. When the operating speed and rotational speed of the pulling rollers satisfy Equations (1)-(3), the maize picking loss rate is minimized [8]:  
\[k=\frac{v_{p}}{v_{c}\sin\theta}=[0.7,\ 1] \tag{1}\]  
\[\frac{n}{v_{c}}\geq\frac{60\times 1000}{iz_{1}p\cos\theta} \tag{2}\]  
\[\frac{n}{v_{c}}\geq\frac{L-h}{\pi dS\cdot\left(\cos\theta\right)^{2}} \tag{3}\]  
The model of maize picking loss rate was established by a central composite design (CCD) experiment, and according to the analysis of the variance of the maize picking loss rate, the rotational speed of the pulling rollers, the header height, the interaction of the rotational speed of the pulling rollers and the header height, the interaction of the operating speed and the header height have a significant effect on the maize picking loss rate. The prediction model for the maize picking loss rate is as follows:  
\[\begin{array}{c}MPL_{opt}=77.49253-0.070253n-4.60942h+1.52849\times 10^{-3} nh+0.74036v_{c}h\\ +1.94932\times 10^{-5}n^{2}+0.061976h^{2}\end{array} \tag{4}\]  
where \(k\) is the scale factor, \(v_{p}\) is the linear velocity of the pulling rollers (m/s), \(v_{c}\) is the operating speed (m/s), \(\theta\) is the header inclination (\({}^{\circ}\)), and \(n\) is the rotational speed of the pulling rollers (r/min). The transmission ratio between the speeds of the conveying chain and pulling rollers in the header gear box is \(i\), where \(z_{1}\) is the number of sprocket teeth of the conveying chain driving wheel, \(p\) is the pitch (mm), \(L\) is the height of the maize in mm, \(d\) is the diameter of the pulling roller (mm), \(S\) is the length of the pulling roller (mm), and \(h\) is the header height (mm).