## 2 Materials and Methods
### Test Bench and Method  
The vibration fundamental of the seed drill working in a rice stubble field was identified as a sinusoidal wave based on the data collected. Consequently, this study employed an eccentric wheel mechanism to convert rotary motion into reciprocating motion at the equilibrium position, thereby generating vibrations.  
Figure 3: Curve diagram of vibration displacement of the seed drill at under different speed.  
The driven component maintained close contact with the eccentric wheel through the restoring force of a return spring. The rotation of the eccentric wheel drove the driven component in sinusoidal motion. The displacement, velocity, acceleration, and vibration frequency of the driven component were determined by the following equations:  
\[S=e(1-\cos\omega t) \tag{2}\]  
\[v=e\omega\sin\omega t \tag{3}\]  
\[a=e\omega^{2}\cos\omega t \tag{4}\]  
\[f=\frac{n}{60}=\frac{\omega}{2\pi} \tag{5}\]  
where \(S\) is the displacement of the driven component, \(v\) is its velocity, \(a\) is its acceleration, \(e\) is the eccentricity, \(f\) is the vibration frequency of the driven component, and \(n\) is the rotational speed of the eccentric wheel.  
Analysis of the motion laws of the driven component revealed that the amplitude of the vibration A = \(e\); therefore, changing the eccentricity of the eccentric wheel can alter the amplitude of the driven component, and adjusting the rotational speed of the eccentric wheel can change its vibration frequency.  
Considering that the vibration frequency experienced by the seed drill during field operations ranged from 0 to 25 Hz and the amplitude from 0 to 3 mm and that the mass of the driven component (the seed metering device) was 1.8 kg, numerical calculations performed using Matlab indicate that the stiffness of the return spring must be greater than 25.15 N/mm and that the maximum torque for the eccentric wheel shaft was 17.58 N-m.  
As shown in Figure 4, The device consists of an eccentric wheel shaft with two pulley assemblies, which are connected to the shaft via return springs. The shaft is driven by a variable frequency motor, which rotates the eccentric wheels, causing the pulley assemblies to vibrate in a sinusoidal pattern. The amplitude and frequency of the vibrations can be adjusted by changing the settings of the variable frequency motor and the return springs. The distance between the two eccentric wheels can be adjusted using set screws, which affects the amplitude of the vibrations. The rotation speed of the variable frequency motor I can be changed to adjust the frequency of the vibrations.  
During the bench test, we added about 96 g of rapeseed in the seed box, adjusted the speed of the seed shaft, placed the inoculation box in the seed filter outlet and timed it  
Figure 4: Structure diagram of **(a)** the whole structure and **(b)** the exploded structure of the vibration test bench. 1. base frame; 2. variable frequency motor I; 3. timing belt; 4. timing belt; 5. top block I; 6. bearing; 7. coupler; 8. top block II; 9. steel wire flexible shaft; 10. variable frequency motor II; 11. limit switch; 12. return spring; 13. pulley assembly; 14. square head stud; 15. eccentric wheel shaft; 16. eccentric wheel; 17. slide slot; 18. the double-row hole-wheel-type seed metering device; 19. top plate; 20. seedmeter shaft.  
with the stopwatch at the same time, vaccinated continuously for 5 min, used ME203E/02 balance quality (precision 0.001 g), repeated each test condition for 10 times, averaged the test results, and obtained the displacement of the seed filter per unit time per minute; this served as the data for subsequent analysis.