Design and experiment of upright cone roller active extrusion ridge and furrow shaping device for cold waterlogged paddy field

Cold waterlogged paddy fields can be characterized by the heavy and humid soil. The challenges remain to form the well-defined ridges and furrows. However, the traditional ridging and furrowing apparatuses cannot fully meet the large-scale production using the relatively low stability of furrow configurations. In this study, an operational approach was proposed as the initial ridging of rotary tillage, followed by the secondary active extrusion. Consequently, a ridge shaping device was devised with the vertical conical roller using active extrusion. The structural parameters and installation positions of the device were determined during operation, according to the soil extrusion and ridge-furrow formation. Additionally, the force analysis was conducted on both the compartment surface pressure roller and the vertical conical roller. An optimal matching was established for the forward velocity of the machinery (ranging from 0.56 to 1.11 m/s), the rotational speed of the furrow and ridge shaping device (70 - 130 r/min), and the rotational speed of the rotary tillage cutter shaft (120 - 220 r/min). The experiments of soil bin were carried out to clarify the effects of soil moisture content, ridge angle, and tool forward speed on the stability coefficients of furrow width and ridge height. The combination of parameters was achieved in the soil moisture content of 32.97%, the ridge angle of 60°, and the tool forward speed of 0.56 m/s. A virtual soil trough was constructed with the machinery forward velocity and the rotational speed of the ridge-furrow shaping device. A quadratic, orthogonal and rotational experiment was carried out, taking as the rotational speed of the rotary tillage cutter shaft serving as the experimental variables, and the stability coefficient of the furrow top width and the soil backflow rate as the evaluation criteria. Variance analysis and regression equation analysis were then performed for the stability coefficient of the furrow bottom width and the soil backflow rate, followed by significance testing. A nonlinear mathematical model was established after optimization, according to the agronomic requirements of cold-soaked fields and the actual operations. The optimal combination of parameters was obtained after optimization in Design-Expert 12 software: A tool forward speed of 0.56 m/s, a ridge shaping device rotation speed of 92.25 r/min, and a rotary tiller blade shaft rotation speed of 194.56 r/min. Under these optimal working parameters, the stability coefficient of the furrow top width was 93.52%, and the soil return rate was 6.75%. The field furrow and ridge shaping trials were implemented to validate the operational performance of the active extrusion furrow and ridge shaping device. The results reveal that the ridge height was 186 mm, the furrow top width was 351 mm, the ridge top width was 1710 mm, the micro-furrow width was 45 mm, and the micro-furrow depth was 22 mm after operation. The stability coefficients of the ridge height, the furrow top width, the ridge top width, the micro-furrow width, and the micro-furrow depth were 95.36%, 91.90%, 92.65%, 96.52%, and 95.77%, respectively. Notably, the stability coefficient of the furrow top width was better in line with the simulation. Compared with the traditional ridge and furrow device, the stability coefficients of the ridge height, the furrow top width, and the ridge top width were increased by 6.9, 7.78 and 6.88 percentage points, respectively. All of the indices were fully met the requirements for the mechanized operations of furrow and ridge shaping in cold waterlogged paddy fields.