## 2 Materials and Methods  
### Field Vibration Data Collection and Analysis  
A test field where the surface was free of significant standing water and the rice had been recently harvested was chosen in Shaoshan, Hunan Province of China. A five-point sampling method was employed to measure the average height of rice stubble, moisture content, and soil firmness across the plot, selecting 1 m\({}^{2}\) areas from each of the four corners and the center of the field. On-site measurements revealed an average rice stubble height of 21.63 cm and a soil firmness of 864 kPa. Fresh, clean surface soil samples of about 100 g were collected from each area. The soil moisture content was determined using an oven-drying method, in which soil was dried in an oven set between 105 \({}^{\circ}\)C and 110 \({}^{\circ}\)C until its weight remained constant. The moisture content was calculated by dividing the mass of the dried soil by its pre-dried mass, and five sets of data were averaged to obtain a soil moisture content of 34.8% for the rice stubble field. The 2 BYG-220 type combined rapeseed planter [16], jointly developed by Hunan Agricultural University and Changsha Sanlaite Agricultural Machinery Equipment Co., Ltd., in Changsha, Hunan Province of China, was selected as the test equipment. The tractor matched with the seed drill had a power of 52.5 kW, overall dimensions of 160 cm\(\times\) 244 cm \(\times\) 165 cm, a working width of 220 cm, and six seeding rows. The seeding rate was 1.5-7.5 kg/ha, the fertilizer application rate was 0-1500 kg/ha, the productivity was 0.3-0.4 ha/h, and the operational speed was 0.56-0.83 m/s. As shown in Figure 1, an accelerometer firmly attached to a flat surface in the middle of the seed drill with strong adhesive glue was used to capture vibration signals perpendicular to the ground. The accelerator's BNC cable harness was secured with tape to prevent significant movement during data collection and to avoid static electricity from friction between the cable and seed drill parts, which could cause cable noise. The wireless router was placed on the side of the seed drill to ensure minimal obstruction and stable data transmission; a transmission signal should avoid mobile phone frequency bands (1.6-2.8 GHz) to prevent electromagnetic interference. Other measuring instruments were securely taped in place and a small piece of plastic foam was placed underneath the instruments for cushioning. The power inverter was installed near the seed drill's 12 V battery and converted the 12 V DC to 220 V AC to power the vibration measurement system equipment. The vibration in the rice stubble field was categorized as a random analog signal. An accelerometer was used to convert the analog signal into an electrical one. The accelerometer captured a series of discrete data points, which lacked continuity, while the field vibration signal was continuous. Therefore, to ensure that the discrete signals did not suffer from  
Figure 1: Seeder vibration test system with acceleration sensor test point location mounted on a 2 BYG-220 type combined rapeseed planter (**a**) as well as the rice stubble field for test (**b**). frequency aliasing, the accelerometer's acquisition of vibration signals had to adhere to the sampling theorem. The 2 BYG-220 type combined rapeseed planter was primarily subjected to vibrations from uneven ground and vibrations caused by the rotating components of the seed drill during operations such as rotary tilling, stubble removal, seeding, and fertilization. Given the seed drill's low advancement speed, the rotary tiller cutter shaft's rotation speed of 200-300 rpm, the machine was predominantly influenced by low-frequency vibrations; i.e., the highest frequency was less than 200 Hz. Therefore, a sampling frequency of 2000 Hz was selected to prevent frequency aliasing in the frequency domain and to avoid significant amplitude distortion in the time domain [17]. The experimental field was chosen for its uniform rice stubble height and the completeness of the field blocks in the stubble land.