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The simulation for a variable fertilization machine could help to show the fertilizing result and provide theoretical guidance in reality machine operation. EDEM (Extended distinct element method) which is a general-purpose software for simulating and analyzing particle system is widely used in simulation experiments of fertilizing machines. In order to optimal design of a variable-rate fertilizer machine. This paper uses EDEM to simulate the spread of three kinds of fertilizers which are potassium chloride, potassium sulfate and urea, commonly used in agriculture, by a centrifugal disc type variable-rate fertilizer applicator. After analysis, the variation coefficients of the lateral homogeneity of the three fertilizers are 43.34%, 26.26% and 39.21%, respectively. The result shows that simulation effect of these three fertilizers is not up to standard, and further research is needed to improve the performance of the fertilizer machine.

The performance test and parameter optimization of variable spraying liquid fertilizer machine was conducted in this research for the uniform spraying of foliar fertilizer. A crop protection of high-clearance tractor with a variable sprayer was used in the experiment. According to the parameter design, three factors and three levels of test were performed based on the Box-Behnken center-united experimental design principles. The performance tests were combined with response surface methodology to analyze spray parameters such as machine walking speed, spray flow rate and plot distance test which would influence Droplet distribution uniformity. A mathematical model was established by using Design-Expert 8.0 software, and the model was analyzed to obtain the optimal combination of spray parameters. The optimized spray parameter combination is: machine walking speed is 4.5km/h, the spray flow rate is 375L/hm 2 , and the distance between the plots is 3m. Under this condition, the minimum variation coefficient of droplet distribution is 10.759%, and the relative error is 9.1% compared with the model prediction value of 9.78%. The results of the study can provide operators with reasonable operating conditions when fertilizing.

In this study, an adaptive dynamic surface control scheme is developed for a class of nonlinear systems. The considered systems can be viewed as a class of unknown pure feedback non-affine systems with multiple constraints. One remarked advantage is that not only less adjustable parameters are used in the design but also the design structure is universal for different systems. The characteristics of the considered systems will lead to a difficult task for design a low-complexity and stable controller. To this end, the mean value theorem is employed to transform the pure feedback systems into a linear structure, but non-affine terms still exist. Then, a novel recursive design procedure is constructed to remove the difficulties of unknown model, pure feedback non-affine characteristic and multiple constraints by integrating two auxiliary elementary functions with a novel bounded estimation approach. Furthermore, based on Lyapunov stability theorem and decoupled back-stepping method, it is proved that all the signals in the close-loop system are global uniformly bounded and the tracking error satisfies prescribed transient and steady state performance indexes constraints. Finally, simulation studies clarify and verify the approach.

In this paper, the adaptive robust tracking control scheme is proposed for a class of multi-input and multi-output (MIMO) non-affine systems with uncertain structure and parameters, unknown control direction and unknown external disturbance based on backstepping technique. The MIMO non-affine system is first transformed into a time-varying system with strict feedback structure using the mean value theorem, and then the bounded time-varying parameters are estimated by adaptive algorithms with projection. To handle the possible "controller singularity" problem caused by unknown control direction, a Nussbaum function is employed, and the dynamic surface control (DSC) method is applied to solve the problem of "explosion of complexity" in backstepping control. It is proved that the proposed control scheme can guarantee that all signals of the closed-loop system are bounded through Lyapunov stability theorem and decoupled backstepping method. Simulation results are presented to illustrate the effectiveness of the proposed control scheme.