Original papers
Implementation of a magnetorheological damper on a no-till seeding assembly for optimising seeding depth

https://doi.org/10.1016/j.compag.2018.05.024Get rights and content

Highlights

  • A development of MR damper system and its implementation into the seeding assembly.

  • Correctness of the sensor-frame for capturing the profile and dynamics.

  • Dynamic performance evaluation of the no-till seeding assembly with the MR damper.

Abstract

No-till seeding requires a seeder that can effectively cope with the untilled soil and place the seeds at an optimum depth in order to achieve a reliable germination and rapid plant emergence. This aim is more challenging due to the inappropriate response of the machine dynamics to harsh soil conditions, such as the compacted soil undulations and the presence of the stubble. In this paper, a seeder main frame carrying a seed dose mechanism and two no-till seeding assemblies was developed and designed with multiple sensors, to capture the dynamics of the assemblies together with the corresponding surface profile. A magnetorheological (MR) damper was implemented into one of the seeding assemblies to optimise its dynamics for better seed placement. A number of strain gauges were used to measure the dynamics of the seeding assemblies, like vertical and impact forces during seeding operation at a travelling speed of 10 km h−1. The accuracy of the surface profile sensing system was validated by obtaining the profile of trapezoidal bumps with georeferenced dimensions resulting in a root mean squared error of 9.6 mm and 9.9 mm for the damped and undamped seeding assembly, respectively.

Experiments were performed seeding wheat (Triticum aestivum L.) operation with a target depth of 40 mm with different damping parameters set on the MR damper by feeding its coil with different current values. The position of each single seed within nine 2 m sections was georeferenced using a total station, to calculate the seeding depth for both seeding assemblies. The seeding assembly with the MR damper, excited with 0.5 A, resulted in a better seeding depth variation with a mean value of 39.8 mm, standard deviation of 5.8 mm and 95th percentile of 49.8 mm over that of other current values applied on the MR damped and the original seeding assembly. The dynamics were improved with a reduction of 21.34% and 67.69% in the amplitude of the vertical and impact forces, respectively. The seeding depth error compared to the target depth for the damped seeding assembly (at 0.5 A) was less than 11.9 mm for 95% of the samples, while this figure was equal to 21.3 mm for the undamped seeding assembly.

Introduction

The aim in no-till seeding is to disturb the soil as less as possible, to preserve the surface residues, and to place the seeds at a proper depth (Derpsch et al., 2014), which will result in a reliable seed germination and plant emergence. However, harsh soil conditions, like soil undulation and crop residues, increase the difficulty in achieving a constant seeding depth. By measuring the forces that are developed at the interface of the coulter tine, and the vertical movements of the coulter during a seeding operation, the dynamic response of the seeder to the untilled soil undulations and the existing stubble can be determined (Sharipov et al., 2017a, Hasimu and Chen, 2014). Taking into account these forces when controlling the vertical displacement of the coulter and optimising the dynamics, the dynamic performance of the seeder can be significantly improved in order to have a better seed placement. Optimising the dynamics of the seeding assembly by implementing a semi-active magnetorheological (MR) damper, which could reduce the amplitude of those forces leading, thus, to a decrease in vertical displacements of the seeding assembly, would result in a better seed placement.

The soil reaction forces resulted from the profile undulations and soil resistance, which are effected by the soil physical properties, influence the mean seeding depth across the coulter width (Fountas et al., 2013). Since the reaction forces describe the dynamics of the seeding component of the seeder, the responses of the seeder to the profile undulations can be expressed by the developed forces (Loghin et al., 2012). In our study, due to the focus on the vertical dynamics of the seeder seeding assemblies, the vertical components of the reaction forces were determined by the vertical and impact forces acting on the coulter tine and the packer wheel, respectively.

Since no-tillage appeared as a part of conservation farming systems, in where the proper seed placement was required while placing the seeds into undisturbed soil (Koller, 2003), many researchers worked on controlling the seeding mechanism for achieving an optimal seeding depth. An early investigation by Lawrance (1969) introduced an analysis of the dynamic response of a semi-mounted seeding implement to the profile undulations and adjusting the seeding depth based on the dynamic responses. This was followed by Morrison, 1978, Morrison, 1988 where an automatic seeding depth control was achieved by adjusting the downforces with a hydraulic down pressure system for no-till planters and grain drills. In addition, Morrison and Gerik (1985) presented a depth control for individual furrow-opener units on planters for conservational farming. An advanced control technique for seeding depth was developed and a seeder performance for accuracy and speed response was optimised by Weatherly and Bowers (1997). Burce et al. (2013) adjusted a conventional seeder configuration to a zero tillage and evaluated its performance by implementing an active control system on independent furrow-openers. An automatic control system to assess the performance of a seed drill with disc coulters was developed by Suomi and Oksanen (2015). However, there have been very limited studies on developing a control model of vertical movements of a no-till direct seeder with a semi-active MR damper using the corresponding actual surface profile and the measured reaction forces.

Semi active MR dampers, which are suspensions of magnetically responsive particles in a magnetorheological fluids (Zhu et al., 2012), have rapidly grown in vehicle and civil engineering due to their advantages in design and control. The MR dampers can offer unique dynamic features such as fast response, low and high force capacity, low power consumption, and a simple interface between the electronic input and the mechanical output (Ahamed et al., 2016, Eshkabilov, 2016). Other advantages of the MR dampers are that they produce high yield stress up to 100 kPa, depended on the magnetic field stress, and are very stable within a wide range of temperature (40–150 °C). Despite their aforementioned advantages, there has been no application of an MR damper in no-till seeders aiming to optimise the dynamic responses of the seeder, in terms of a better performance in seed placement.

A previous work by Sharipov et al. (2017b) resulted in a correlation value of 0.6 between the seeder performance, in terms of seeding depth variation, and the dynamic response of the seeder to harsh soil conditions. This value can be regarded as sufficient for this type of complex systems with high in-field dynamics. Data fusion of modern sensors, such as highly accurate robotic total stations, whose accuracy has been tested under realistic conditions (Paraforos et al., 2017), inertial measurement units (IMU), and laser pointers, could provide the means to assess the seeder dynamic performance together with the corresponding seeding depth. Based on the analysis of the correlation between the seeder dynamic response (forces) and the seeding depth variation, the performance of a seeding assembly with a semi-active MR damper was modelled and simulated in our previous study (Sharipov et al., 2017a). The simulation analyses demonstrated significant reduction in the amplitude of the developed forces which could result in a reduced seeding depth variation. Consequently, the next step forward would be the implementation of the semi-active MR damper into a seeding assembly.

The aim of this paper is to optimise the performance of the seeding assembly, in terms of better seed placement, by implementing an MR damper. The contribution of the present work is the application of an MR damper in no-till seeders, which can reduce the amplitude of the reaction forces resulting in a better performance in seed placement. The seeding depth variation when supplying the MR damper with different supply currents should be compared since an important technical objective is to define the optimum damping parameter (current value) for the MR damper that the seeding assembly achieves its best performance. The dynamics improvement, in terms of amplitude reduction of the vertical and impact forces resulted from the original assembly compared to the produced damped forces by the MR damped implemented assembly should be assessed. In order to validate the performance improvement of the seeding assembly with the MR damper, this should be compared to that of the original seeding assembly under the same operating conditions.

Section snippets

Developed no-till seeding prototype

A machine prototype was developed comprising a metal frame that carried a Green Drill 200 seed dosing mechanism and two ConTeC Schare no-till seeding assemblies (both from AMAZONEN-Werke H. Dreyer GmbH & Co. KG, Hasbergen, Germany) (Fig. 1a). The frame had two side-wheels in a parallelogram assemblage while the height from the ground could be manually configured. The seed dosing mechanism consisted of a 200 l volume hopper and a seed shaft located inside the metering unit below the hopper. The

Determination of forces and surface profiles

The recorded strains at the three points of the seeding assembly were used to calculate the vertical forces and draught forces acting on the point of coulter interacting with soil, and the profile impact forces at the impact point of the packer wheel. The detailed formulas of calculating all these forces are given in Sharipov et al. (2017b). To extract the surface profiles, the required transformations from the prism, tracked by the total station, to the ground impact point of the packer wheels

Profile sensing system validation

The elevation profiles of the seeding assemblies traversing the trapezoidal bumps were calculated by implementing the Eqs. (4), (6). In Fig. 6. the profile of the trapezoidal bumps and the obtained profiles of seeding assemblies for the speed of 10 km h−1 are presented. Using Eq. (1), the RMS errors between the elevation profiles and the profiles of the bumps profile were evaluated. The profile of the seeding assembly with the MR damper as it was compared to the profiles of the bumps indicated

Conclusions

A no-till seeder was constructed consisting of an automatic seed dose mechanism and two seeding assemblies with and without semi-active MR damper. The developed profile sensing system indicated sufficient accuracy for obtaining the field surface profiles during seeding operation in absolute geo-referenced coordinates. The performances as seeding depth variation and the dynamics of both seeding assemblies were evaluated. Compared to the dynamics of the original seeding assembly, the seeding

Acknowledgements

The financial support of GA nr 213-2723/001–001–EM Action2 TIMUR (Training of Individuals through Mobility to EU from the Uzbek Republic) project is gratefully acknowledged. The authors are very thankful to Dr. R. Resch and Ch. Gall from AMAZONEN-WERKE H. Dreyer GmbH & Co.KG (Osnabrück, Germany) for providing the seed dose mechanism and the seeding assemblies and to Ch. Schwarze for the assistance building the seeder main frame and performing the field experiments. The authors are also grateful

References (21)

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