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

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.