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The physical and mechanical parameters of the rotten rice straw (RRS), rice husk biochar (RHB), and the mixture of the two materials (the substrate) were calibrated by Plackett-Burman and Box-Behnken experiments to obtain the parameters for simulation of the forming of the Gentiana seedling substrate mat (GSSM). The particle contact parameters were calibrated, and the repose angle was taken as the response value based on the Hertz-Mindlin approach with the JKR contact model of discrete element method (DEM). A quadratic regression model was established and optimized using Design-Expert software. The parameters that most affected the substrate repose angle were the restitution coefficient of RRS of 0.20, the rolling friction coefficient of RRS of 0.04, the surface energy of RRS for JKR of 0.53, and the surface energy of RHB-RRS for JKR of 2.11. The simulated repose angle of the substrate and the bending strength of GSSM were compared with that of the verified experimental values respectively based on the optimal parameters. The relative errors of repose angles and bending strengths between the values of the simulation and the measurement were 0.71% and 1.39% respectively, indicating that the parameters obtained in this study can provide a reliable reference for the forming of GSSM.

Transplanting is the prime growing pattern for rice production, and seedling raising is an essential step of the process. However, the massive soil source and the complicated treatments needed for seedling raising are major issues. This study explored the possibility of using compressed-decomposed rice straw and biochar from rice husk into a seedling-raising mat, to replace the soil and simplify the seeding process. A quadratic rotation-orthogonal combination experiment was conducted to investigate the effect of moisture content, pressure, and residence time on the formation of seedling-raising mat. The regression models between the compressing indicators and the process factors were established. The results showed that the following factors had significant effect on bending strength of the formed mat (P < 0.01): the pressure and residence time have extreme effects on dimensional stability (P < 0.01); but the influence of moisture content was insignificant (P > 0.05). The process parameters for compression were optimized and verified using Design-Expert software 8.0.6. The optimized parameters were moisture content of 33%, pressure of 23.0 MPa, and residence time of 61 s. The prediction error is less than 6% under this condition. The results may provide a reference for biomass seedling-raising mat compression.

To improve wheel trafficability in soft and muddy soils such as paddy fields, a bionic walking wheel is designed based on the structural morphology and movement mode of the feet of waders living in marshes and mudflats, similar to the muddy soil of paddy fields. The bionic walking wheel adopts the arrangement of double-row wheel legs and staggered arrays to imitate the walking posture of waders. The two legs move alternately, cooperate with each other, and improve the smoothness of movement. The cam inside the bionic walking wheel is used to control the movement mode of the feet. The flippers open before touching the ground to increase the contact area and reduce sinking, and the toes bend and grip the ground while touching the ground to increase traction. Multi-rigid-body dynamics software (Adams View 2020) is used to simulate the movement of the wheel during the wading process, and the movement coordination and interference between the wheel legs are analyzed. The simulation results show that there is no interference between the parts and that the movement smoothness is good. The interaction between the bionic walking wheel and muddy soil was analyzed via coupled EDEM–ADAMS simulation, and the simulation analysis and experiments were conducted and compared with those for a common paddy wheel. The results showed that the bionic walking wheel designed in this paper improved the drawbar pull by 113.56% compared with that of a common paddy wheel and had better anti-sinking performance. By analyzing the effect of toe grip on traction, it was found that the soil under the feet can be disturbed to provide greater traction when the toe is bent downward. This study provides a reference for improving the trafficability of walking mechanisms in soft and muddy soils, such as paddy fields.

The application of fertilizer is necessary for the growth and yield of crops, especially for paddy rice. Precision application is important for the fertilizer utilization rate and sustainable development of agriculture. However, the crushing of fertilizer grains will reduce the quality of fertilization, for the decrease in the size and mass of the fertilizer particles and the degree of crushing mainly depend on the physical and mechanical properties of the fertilizer grains. In this study, the compression strength and critical impact speed of four typical commonly used fertilizer grains, a compound fertilizer of nitrogen, phosphorus, and potassium (NPK compound fertilizer), organic fertilizer, large granular urea, and small granular urea, were measured and analyzed. The static compression test was carried out using a TMS-Pro texture analyzer and the results show that the four kinds of fertilizer grains are brittle materials, and their elastic moduli are 208 MPa, 233 MPa, 140 MPa, and 107 MPa, respectively; the theoretical impact model of fertilizer granules is established based on the compression test result and Hertz elastic contact theory, the theoretical formula for the critical impact speed of fertilizer grains is derived, and the theoretical critical impact strength and speed are worked out. An image capture system for the impact process of fertilizer grains was developed, and the impact test was conducted. The results show that the critical impact speed of the four kinds of fertilizer grains decreases with the increase in granule size, while the variance analysis shows that the effect is not significant. The comparison of the experimental results with the theoretical values shows that the theoretical formula could be used to predict the trends of the critical impact speed of fertilizer grains. The model was optimized with the MATLAB 2018 function fitting tool based on the test and analysis. The goodness of fit of the formula is 0.824, which is 13.43% greater than that of the original theoretical formula, indicating that the modified formula based on the compression test data might estimate the critical impact speed of the granular fertilizer with brittle material properties more accurately. The results may provide a reference for the parameter design of a precision fertilization machine.

To improve the environment perception ability of wheeled mobile robots (WMRs), the visual behavior mechanism of the negative-correlation motion of chameleons is introduced into the binocular vision system of WMRs, and a shifty-behavior-based environment perception model with chameleon-inspired active vision for WMRs is established, where vision–motor coordination is achieved. First, a target search sub-model with chameleon-inspired binocular negative-correlation motion is built. The relationship between the rotation angles of two cameras and the neck and the camera’s field of view (FOV), overlapping angle, region of interest, etc., is analyzed to highlight the binocular negative-correlation motion compared with binocular synchronous motion. The search efficiency of the negative-correlation motion is doubled compared with binocular synchronous motion, and the search range is also greatly improved. Second, the FOV model of chameleon-inspired vision perception based on a shifty-behavior mode is set up. According to the different functional requirements of target searching and tracking stages, the shift of the robot visual behavior is analyzed from two aspects, measuring range and accuracy. Finally, a chameleon-inspired active-vision-based environment perception strategy for mobile robots is constructed based on the shifty-behavior mode, and experimental verification is deployed, which achieves the reproduction of the visual behavior of chameleons in the vision system of mobile robots with satisfactory results.

Pelleting experiments were carried out in this study to clarify the influence mechanism of wet-fermented soybean dregs on the forming of corn stover. The effects of addition of water or wet fermented soybean dregs on the forming quality of corn stover were comparatively studied under different corn stover particle sizes and compression displacement. The fermented soybean dregs significantly affected the relaxed density, dimensional stability coefficient, and hardness of feed pellets. The relaxed density, dimensional stability coefficient, and hardness of feed pellets increased first and then decreased with the increase of fermented soybean dregs. The forming quality of corn stover added with fermented soybean dregs was higher than that of corn stover added with the same amount of water. The mechanism allowed soybean dregs to strengthen the bonding between corn stover particles and thus improved the quality of feed pellets. A certain amount of water was favorable for corn stover pelleting, but excessive water may decrease the quality of pellets. The comprehensive analysis showed that the addition of 5–10% fermented soybean dregs to the corn stover improved the relaxed density, dimensional stability coefficient, and hardness of feed pellets by 10.76–23.51%, 7.32–15.74%, and 33.39–454.47%, respectively.

To explore the drying characteristics of soybean dregs and a nondestructive moisture content test method, in this study, soybean dregs were dried with hot air (80 °C), the moisture content was measured using the drying method, water status was analyzed using low-field nuclear magnetic resonance (LF-NMR) and the moisture content prediction models were built and validated. The results revealed that the moisture contents of the soybean dregs were 0.57 and 0.01 g/g(w.b.), respectively, after drying for 5 and 7 h. The effective moisture diffusivity increased with the decrease in moisture content; it ranged from 5.27 × 10−9 to 6.96 × 10−8 m2·s−1. Soybean dregs contained bound water (T21), immobilized water (T22) and free water (T23 and T23’). With the proceeding of drying, all of the relaxation peaks shifted left until a new peak (T23’) appeared; then, the structure of soybean dregs changed, and the relaxation peaks reformed, and the peak shifted left again. The peak area may predict the moisture content of soybean dregs, and the gray values of images predict the moisture contents mainly composed of free water or immobilized water. The results may provide a reference for drying of soybean dregs and a new moisture detection method.

Pressed condensation is a key process before the reclamation of loose corn straws. In this study, the effects of stabilization time on the relaxation density and dimensional stability of corn straws were studied firstly, and then the stabilization time was determined to be 60 s by comprehensively considering the compression effect, energy consumption, efficiency and significance. On this basis, the effects of the water content (12%, 15%, 18%), ratio of pressure maintenance time to stabilization time (0, 0.5, 1), maximum compression stress (60.4, 120.8, 181.2 kPa) and feeding mass (2.5, 3, 3.5 kg) on the relaxation density, dimensional stability coefficient, and specific energy consumption of post-compression straw blocks were investigated by the Box−Behnken design. It was found that the water content, ratio of pressure maintenance time to stabilization time, maximum compression stress, and feeding mass all very significantly affected the relaxation density, dimensional stability coefficient and specific energy consumption. The interaction between water content and maximum compression stress significantly affected both relaxation density and specific energy consumption. The interaction between the ratio of pressure maintenance time to stabilization time and feeding mass significantly affected the dimensional stability coefficient. The factors and the indices were regressed by quadratic equations, with the coefficients of determination larger than 0.97 in all equations. The optimized process parameters were water content of 13.63%, pressure maintenance time of 22.8 s, strain maintenance time of 37.2 s, maximum compression stress of 109.58 kPa, and raw material feeding mass of 3.5 kg. Under these conditions, the relaxation density of cold-pressed straw blocks was 145.63 kg/m3, the dimensional stability coefficient was 86.89%, and specific energy consumption was 245.78 J/kg. The errors between test results and predicted results were less than 2%. The low calorific value of cold-pressed chopped corn straw blocks was 12.8 MJ/kg. Through the situational analysis method based on the internal and external competition environments and competition conditions (SWOT analysis method), the cold-pressed chopped corn straw blocks consumed the lowest forming energy consumption than other forming methods and, thus, are feasible for heating by farmers. Our findings may provide a reference for corn straw bundling, cold-press forming processes and straw bale re-compressing.

Transplanting is the prime growing pattern for rice production, and seedling raising is an essential step of the process. However, the massive soil source and the complicated treatments needed for seedling raising are major issues. This study explored the possibility of using compresseddecomposed rice straw and biochar from rice husk into a seedling-raising mat, to replace the soil and simplify the seeding process. A quadratic rotation-orthogonal combination experiment was conducted to investigate the effect of moisture content, pressure, and residence time on the formation of seedling-raising mat. The regression models between the compressing indicators and the process factors were established. The results showed that the following factors had significant effect on bending strength of the formed mat (P < 0.01): the pressure and residence time have extreme effects on dimensional stability (P < 0.01); but the influence of moisture content was insignificant (P > 0.05). The process parameters for compression were optimized and verified using Design-Expert software 8.0.6. The optimized parameters were moisture content of 33%, pressure of 23.0 MPa, and residence time of 61 s. The prediction error is less than 6% under this condition. The results may provide a reference for biomass seedling-raising mat compression. [ABSTRACT FROM AUTHOR]