Robotic Mowing of Tall Fescue at 90 mm Cutting Height: Random Trajectories vs. Systematic Trajectories

Tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.) is often managed with a cutting height ranging from 70 to 100 mm in ornamental lawns. Some autonomous mowers have been specifically designed to maintain mowing height in the same range. Generally, autonomous mowers operate by following random trajectories, and substantial overlapping is needed to obtain full coverage of the working area. In the case of tall grass, this may cause lodging of grass plants, which in turn may reduce turf quality. The introduction of a navigation system based on systematic trajectories has the potential to improve the performances of autonomous mowers with respect to machine efficiency and turf quality. With the aim of determining the effects of reduced mowing frequency and systematic navigation systems on turf quality and mower performances in terms of working time, energy consumption and overlapping, the performances of two autonomous mowers working with random and systematic trajectories were tested on a mature tall fescue lawn at 90 mm cutting height. The working efficiency was approximately 80% for the systematic trajectories and approximately 35% for the random trajectories; this was mainly due to the lower overlapping associated with systematic trajectories. Turf quality was slightly higher for the mower working systematically (a score of 8 using a 1–9 score with 1 = poor, 6 = acceptable and 9 = best) compared to the one working randomly (quality of 7 and 6 on a 1–9 scale with 1 = poor and 9 = best). No appreciable lodging was observed in either case. For tall, managed lawns, systematic trajectories may improve autonomous mowers’ overall performances.

Design and experiment of self-propelled straw forage crop harvester

The harvesting straw feed crops (silage corn, alfalfa, herbaceous mulberry, etc.) was tedious, high-labor-cost, and large-nutrient-loss. A self-propelled straw forage crop harvester, which could realize the integration of cutting, flattening and modulating, chopping, and throwing straw forage crops, was designed. The cutting angle could freely be adjusted between 0° and 8°. The max rotation speed of the flattening roller could reach 590 r/min and could be adjusted consecutively by the hydraulic control device. To verify the performance of this machine, several harvesting experiments of alfalfa, silage corn, and herbaceous mulberry with different moisture, were carried out on this machine. During the experiment, the average working speed of the machine was 1.6 m/s, the cutting height was 40–80 mm, and the flattening rate was 97.14%. It is determined that the suitable cutting speed for harvesting alfalfa is 2131 r/min; the suitable cutting speed for harvesting silage corn is 836 r/min; the suitable cutting speed for harvesting herb mulberry is 1045 r/min. The design of the machine can not only improve labor productivity and reduce the nutrient loss of forage crop but also support the silage harvesting machinery and equipment for forage crop.

Determination of the appropriate level of manure fertilisation for Moringa oleifera grown for animal feed

The purpose of this study is to determine the appropriate level of chicken manure for the green fodder M. oleifera grown for leaf meal production as a supplement into poultry diet to improve poultry product quality (i.e., meat and egg). The experiment was conducted at Thai Nguyen University of Agriculture and Forestry, Vietnam, for two years from 2018 to 2019. The experiment consisted of four treatments (NT) represented by four different levels of chicken manure, namely, 0 tons (NT1), 10 tons (NT2), 20 tons (NT3) and 30 tons/ha/yr (NT4). Each treatment was carried out over an area of 24 m2 with 5 replicates. The experiment was the complete randomised block design. Other factors such as plantation density, nitrogen, phosphate, potassium fertiliser levels, cutting height, and cutting intervals, etc., were similar among treatments. The results showed that the leaf dry matter yield of NT1 through NT4 was 6.919, 8.131, 8.975, and 9.494 tons/ha/yr, respectively. That of the leaf crude protein was 2.244, 2.694, 3.073, and 3.357 tons/ha/yr, respectively. Increasing manure levels from 0 to 30 tons/ha/yr decreased the dry matter content in the leaves by 1.43%, increased the crude protein in leaf dry matter basic by 2.93%, and decreased crude fibre in the leaf dry matter basic by 2.24%. Based on these results and data from statistical analysis, the most appropriate level of chicken manure application for M. oleifera was at 20 tons/ha/yr.

Novel Application of the Roof-Cutting-Type Gob-Side Entry Retaining in Coal Mine

In this study, the roof-cutting-type gob-side entry retaining is introduced, and its application in medium-thickness coal seams is studied. Based on the analysis of the construction procedure and principle, the mechanical model of the retained roadway structure and cantilever beam formed by roof cutting was established, and the support resistance and roof deformation were obtained. In addition, through technological design analysis and numerical simulation, the parameters of roof cutting were determined. The roof-cutting height and angle were designed to be 9 m and 15°, respectively. Flac3 D was used to analyze the stress evolution law under different mining conditions. The stress on the integrated coal side and roof subsidence was lower when the roof-cutting height was 8∼10 m and the cutting angle was 15°. Through field monitoring, the roof pressure, gob-side lateral gangue retaining pressure, anchor cable stress, and deformation of the surrounding rock eventually reached a stable state. This indicates that the roof cutting can effectively cut down the overlying strata over the gob and form a stable entry structure to meet the requirements of the next working face.

Determination of Reasonable Width of Filling Body for Gob-Side Entry Retaining in Mining Face With Large Cutting Height

When gob-side entry retaining is adopted in mining face with large cutting height, due to large stope space, strong dynamic pressure and other reasons, the filling body is usually broken and unstable due to improper width of filling body, and the stability of surrounding rock of roadway is poor. Therefore, this paper will take Shaqu mine as the engineering background to study the reasonable filling body width of gob-side entry retaining in mining face with large cutting height. Firstly, the stability factors of gob-side entry retaining in mining face with large cutting height are analyzed, and the mechanical model of bearing structure of gob-side entry retaining is established based on the lateral pressure and overlying load of filling body, and the reasonable width of filling body is obtained quantitatively; Numerical simulation is used to analyze the evolution of vertical stress, vertical displacement and plastic zone of working face with the change of filling body width. Finally, combined with the deformation observation results of 24207 gob-side entry retaining roof, two sides and filling body, the rationality of filling body width is verified. The results show that: the setting of the width and strength of the filling body plays an important role in the stability of gob-side entry retaining. According to the mechanical model, the minimum width of the filling body is 2.2m in the lateral direction and 3.9m in the vertical direction; Numerical simulation shows that when the width of filling body is too small, with the increase of filling body width, the vertical stress of filling body increases gradually. When the width of filling body reaches a certain value, the vertical stress decreases with the increase of width, and the stress concentration area will change from symmetrical type to eccentric load type, from the middle of filling body to the side of filling body near gob. If the width of the filling body is too small, the filling body will be too broken to bear the load, resulting in too small vertical stress and too large vertical displacement of the roadway roof. The larger the width of the filling body is, the greater the cutting resistance is, the more timely the side roof of the gob can be cut off, the less the stress of the roadway and the filling body, and the more stable the retained roadway is. Finally, through the observation of 24207 gob-side entry retaining, the total deformation of two sides and roof and floor of roadway tends to be stable after 665mm and 597mm respectively. The roof of roadway does not appear severe subsidence and obvious cracking, and the floor does not appear too large floor heave. The effect of roadway retaining is good, which indicates that 4m support can meet the needs of practical engineering.

Forage yield of Urochloa brizantha [(Hochst. Ex A. Rich.) R.D.] cv. Insurgente at different cutting heights

Objective: Evaluate the forage yield of Urochloa brizantha cv. Insurgente at differentcutting heights.Design/ methodology/ approach: the experiment was carried out at the Universidaddel Papaloapan, Loma Bonita, Oaxaca, Mexico. Four cutting heights were evaluated (5,10, 15, and 20 cm) during the rainy, norther, and dry seasons. The experiment followeda randomized block design with four replicates. We evaluated plant height (PH), greenmatter yield (GMY), dry matter yield (DMY), growth rate (GR), and morphologicalcomponents, such as leaf yield (LY), sheath yield (SY), and stem yield (StY).Results: the cutting height and season interaction was significant for all the evaluatedvariables (P?0.01). The highest PH (42 cm) was obtained with a cutting height of 20 cmduring the rainy season. The highest GMY and DMY (2,484 and 606 kg ha -1 ,respectively) were obtained with cutting heights of 15 cm during the rainy season. Thesevalues were similar (P>0.05) to those obtained at 20 cm (2,410 and 582 kg ha -1 ,respectively). The highest LY, SY, and StY values were obtained with cutting heights of15 and 20 cm during the rainy season. The highest GR (31 kg MS ha -1 day -1 ) wasobserved during the rainy season, regardless of cutting height.Findings/ conclusions: for each of the evaluated seasons, cutting heights of 15 and 20cm resulted in the highest forage yields of U. brizantha cv. Insurgente.