Multi-Criteria Optimization of a Four-Bar Linkage Vibratory Mechanism for Mechanized Uprooting of Sida (Bala)

Abstract

Harvesting of Sida (Bala), a medicinal crop with a deep taproot system, is mainly performed manually. This method requires considerable labour, results in low field efficiency, and often leads to root damage, particularly in compact or hard soils. To overcome these challenges, the present work examines the design and optimisation of a four-bar linkage-based vibratory mechanism for a mechanised Sida uprooter, with the objective of minimising soil resistance and improving uprooting efficiency. Dimensional synthesis of the four-bar mechanism was carried out using MATLAB, which produced 1,056 possible link combinations. Each combination was examined with respect to Grashof’s condition, coupler-point trajectory characteristics, and its capability to generate controlled oscillatory motion suitable for soil-tool interaction. The optimal linkage configuration consisted of a 33.0 cm fixed link, a 1.5 cm crank (centre-to-centre), a 41.0 cm coupler, and a 36.0 cm rocker. This linkage generated stable vibratory motion for effective soil loosening around the root zone. The optimised design was developed in SOLIDWORKS and examined through finite element analysis in ANSYS. The analysis indicated a maximum equivalent stress of 154.42 MPa, a maximum deformation of 0.605 mm, and a factor of safety of 2.97, indicating that the mechanism can safely withstand the expected field loads. Overall, the developed mechanism can serve as an energy-efficient solution for the mechanised harvesting of deep-rooted medicinal crops such as Sida.