Synthesis and optimization of an eight-bar linkage mechanism for seat suspensions

The work presents the analysis and synthesis of an eight-link mechanism for industrial seat suspension, followed by a numerical optimization of the design under specific technical requirements. Even though the eight-bar linkage mechanism is a well-known architecture, it has few applications in seat suspensions, and it shows interesting features compared with more traditional scissor systems. It is possible to exploit this mechanism, provided that is correctly designed, to achieve a seat suspension system, which grants a large quasi-perfect vertical motion, without the need of prismatic couplers, which are often a weak point in off-highway application due to their maintenance issues and cost. Firstly, the problem was tackled analytically in order to obtain the general set of equations and verified numerically with a multibody solver. Secondly, to choose the best solution for the application, we carried out an optimization of the system, aimed at minimizing the horizontal displacement of the seat along with granting the desired vertical travel needed. The results are both a general design procedure to optimize under specific constraints the eight-bar linkage for seat suspensions problems and a detailed design and possible embodiment of a seat suspension systems with application in the agricultural field.