RT Dissertation/Thesis
T1 Modelling and optimisation of no-till seeder dynamics for precise seeding depth
A1 Sharipov,Galibjon
WP 2019/02/27
AB Achieving better seeding depth consistency in no-till seeding is a critical performance metric of the seeding machine and is of great importance due to its profound effect on reliable seed germination and seedling emergence resulting in a yield increase. Growing implementation of no-tillage in big size farms requires high-capacity seeding machines with increased operation speed and working width. Thus, the increased capacity of the seeding machine as well as harsh soil conditions like the surface undulations and the presence of previous crop residues make the desired working quality of no-till seeders challenging for both designers and manufacturers. 
The aim of this cumulative dissertation was to optimise a no-till seeder dynamics in terms of vertical motion stability for better seed placement under realistic high-capacity performance. To fulfil this aim, an approach to achieve the desired dynamic behaviour of the seeder was carried out based on three phases: (1) evaluation of the seeder dynamic performance by defining the relationship between the seeder dynamics and the corresponding seeding depth variation, (2) modelling and simulation of the seeding assembly motion dynamics to specify a control system (e.g. MR damper system) for dynamics improvement, (3) implementation of the defined system into the seeding assembly and testing of the new seeding assembly prototype. 
The present work was the first approach to optimise the dynamic motion behaviour of a no-till seeder by implementing an MR damper system into its seeding assembly for better seed placement under realistic high-capacity working conditions. The AMAZONEN no-till direct seeder was an ideal candidate for this investigation as it contains 12 identical tine type seeding assemblies where the operating depth is defined by the position of the packer wheel. Under working conditions, the maximum width is 3 m resulted from the inter-row distance of 0.25 m between the seeding assemblies. The seeding assemblies are provided with downforces using a hydraulic cylinder in order to keep the packer wheel of the assemblies on the ground and to maintain a consistent seeding depth during seeding operation. Concurrent and geo-referenced sensor data made it possible to acquire the dynamics parameters of the seeder and the corresponding soil surface profiles (the point where the packer wheel touches the ground). This together with the measured 3D geo-referenced position of the seeds gave the opportunity to define the reason of high variations in seeding depth.
A sensor-frame was developed, utilising up-to-date sensor technology, to capture the seeder dynamics and to determine the corresponding soil surface profile. A combination of strains recorded at the three corresponding points of the seeding assembly using linear strain gauges was employed to calculate the vertical forces, draught forces and the profile impact forces. A new methodology was introduced to extract the absolute seeding depth from the combination of the determined surface profile and the measured 3D position of the seeds in absolute coordinates. Geo-referenced coordinates of seed positions in combination with geo-referenced surface profile and machine dynamics parameters, offered the possibility to define the reason of seeding depth variation. To do that, the relation between the forces (i.e. vertical and profile impact forces) and the variation of seeding depth was defined by correlating the spatial frequency contents of each dataset.
An investigation of the seeder dynamics was carried out by modelling and simulating its performance based on measured data (e.g. determined surface profile and vertical forces) to define a system that can reduce the effect of the forces for better seed placement in no-till seeding. The seeding assembly together with and without a MR (magnetorheological) damper system, which was considered to be located in-between the coulter and the packer wheel, was introduced as a semi-active and passive system. Furthermore, three hysteresis models, such as Bingham, Dahl and Bounc-Wen model, were applied for the semi-active MR damper system behaviour. Among the models, the Bouc-Wen model demonstrated more significant improvements over the passive system model. Analysis of the performance of the semi-active MR damper implemented seeding assembly against the passive system proved the vertical motion dynamics of the assembly, in terms of vertical displacements (52.3%) and its affecting forces (54.1%) to be optimised for better seed placement. Testing the performance of the MR damper implemented seeding assembly compared with that of the original seeding assembly confirmed the potential of the MR damper implemented seeding assembly. The dynamics of the seeding assembly with the MR damper depicted a reduction of 67.69% in the amplitude of the impact forces compared to the original seeding assembly. Consequently, the improvement in the dynamics resulted in better seed placement. The variation of the damped seeding depth, as it was the performance of the seeding assembly with the MR damper, compared to the target seeding depth resulted in an absolute error of 11.9 mm for 95% of its samples, which is considerably less than the error with a value of 21.3 mm for the seeding depth variation resulted from the original seeding assembly. By designing the seeding assembly with the MR damper system, the dynamics of seeding machine can be significantly optimized for better seeding depth consistency.

K1 Saattiefe
K1 Maschinendynamik
K1 Direktsaat
PP Hohenheim
PB Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim
UL http://opus.uni-hohenheim.de/volltexte/2019/1589