Statistical models expressing relations between soil moisture, aggregate speed, and tillage depth at plowing and cultivation

The study is based on a one-year field experiment (2019) in the land of the Chirpan region located in central Bulgaria. The agrotechnical operations of plowing and cultivation, applied in technology for the production of sunflower, are studied. Four models (Linear, Exponential, Logarithmic, and Quadratic) were compared at p < 0.05, defining the relation between soil moisture, aggregate speed, and the uniformity of the soil index Tillage depth during plowing and cultivation. It was found that in plowing at a speed of 4 km/h the Quadratic model described the relation between soil moisture and tillage depth with the highest coefficient of determination (R2 = 0.682). Relating to plowing at a speed of 4.5 km/h the most suitable is the Exponential model (R2 = 0.729), i.e. about 68.2% and 72.9% of the variations in tillage depth are due to the influence of the moisture of the soil. The coefficients of determination, calculated when cultivating at speeds of 8 km/h (R2 = 0.526) and 9 km/h (R2 = 0.557), show that the Quadratic model most strongly (52.6% and 55.7%) determines the relation between soil moisture and tillage depth. The developed models could be used to optimize the control systems of agricultural machinery.

DESIGN AND TEST EVALUATION OF THE SUBSOILER EQUIPPED WITH TILLAGE DEPTH MONITORING AND CONTROL SUBSOILING ASSEMBLIES

Aiming at solving problems that the variation of tillage depth between rows and within rows caused by the surface undulation was great, the lateral stability of tillage depth obtained by the method of adjusting at the three-point suspension was poor, and lack of subsoilers with the function of accurate detection and adjustment of single row tillage depth, a method of independent control of single row tillage depth based on ultrasonic sensor detection and hydraulic adjustment was proposed. And the tillage depth monitoring and control subsoiling assembly and the subsoiler equipped with subsoiling assemblies were designed. The key structural parameters of the hydraulic cylinder and the model of the three-position four-way magnetic exchange valve were determined. The subsoiling quality and performance comparison tests were conducted, and the results showed that the mean value of the variable coefficient of soil hardness, looseness of soil and coefficient of soil disturbance were 52.23%, 32.55% and 62.15%, respectively, and the stability coefficient of tillage depth was 92.43%, which all met the subsoiling operation requirements. The standard deviation of tillage depth belonged to the method of independent adjustment of single row and unified adjustment of each row were 38.315mm and 51.521mm, respectively. The subsoiler equipped with tillage depth monitoring and control subsoiling assemblies designed in this paper was capable of significantly improving the stability of tillage depth between rows and within rows.

DEVELOPMENT AND TESTING OF BED FORMER IMPLEMENT POWERED BY HAND TRACTORS

Soil tillage, like making raised beds, is time-consuming and labour-intensive if it is done without the help of mechanization. Therefore, this study aims to develop and test a bed former powered by a hand-tractor for upland. It was carried out in the experimental field (sandy clay loam texture) at a furrower depth of 15 cm and 20 cm with a tractor forward speed of 0.5 m/s. The bed's former design results have dimensions of length, width, and height of 1200x1000x 820 mm. The performance test results showed an increase in tillage depth resulted in increased bed height, bed width, bed width, and slip. However, field capacity decreases with increasing tillage depth. The bed former's performance was found to be satisfactory in general.

A Tillage Depth Monitoring and Control System for the Independent Adjustment of Each Subsoiling Shovel

Subsoiling can break the compacted hardpan without turning or mixing soil layers. It has significant advantages in improving soil structure, promoting rainwater infiltration, and increasing air permeability of soil. The soil compacted hardpan will not be completely broken and more power consumption will be generated unless the desired tillage depth is obtained. However, due to uneven surface between and within each row of subsoiling shovel in the field, the existing adjustment methods, adjusting via the lifting device of the whole machine or a group of tillage components, cannot ensure each subsoiling shovel avoiding undesired tillage depth. Therefore, a tillage depth monitoring and control system for the independent adjustment of each subsoiling shovel was developed, and the methods of detecting, adjusting, displaying, and recording tillage depth were described. Field experiments were conducted to evaluate detecting accuracy, stability of tillage depth, transient response time, and advantages. The results showed that the value obtained by sensor differed from manual measurement at the speed of 3 km/h, 4 km/h, and 5 km/h averagely by 8.28%. The mean value of the coefficient of the tillage depth stability at three speeds were all greater than 94%. The mean transient response time was 0.6 s. The standard deviation of tillage depth obtained under system control was 38.31, which was less than the 51.52 obtained by only adjusting on the three-point suspension. The subsoiler equipped with this system was capable of obtaining a desired tillage depth of each subsoiling shovel in every second.

RESEARCH ON PLC SYSTEM DESIGN OF A NEW TYPE OF ROTARY TILLER CONTROL PARAMETERS (Programmable Logic Controller)

The purpose of this paper is to design a rotary tiller control system based on programmable controller technology, and verify the application of this control system. In this paper, the traction and depth control of rotary tiller are transformed into the control of piston rod displacement of hydraulic cylinder, and the intelligent fuzzy control of axial extension displacement of rotary tiller and output torque of piston rod is realized. According to the characteristics of the mathematical model, the objective function is determined and the motion parameters are optimized by the steepest descent method, which provides a reliable calculation model for the optimization design of the overall parameters of the rotary tiller. The rotary tiller control system based on PLC (Programmable Logic Controller) can realize the effective control of rotary tillage depth and speed, and the error of rotary tillage depth can be guaranteed within 4.5%. When the soil resistance of the rotary tiller suddenly increases, the fuzzy control of the comprehensive tillage depth value of the stressed position can effectively improve the rotational speed stability of the hydraulic motor for tillage depth control. PLC technology puts the digital control of rotary tiller on a higher technical platform, thus reducing the labour required for agricultural planting, providing a good growth environment for crops and realizing the intelligence of rotary tiller.