Harnessing elastic energy to overcome singularity issues in four-bar mechanisms with a crank link

• Published in: Mechanism and machine theory 2023-05, Vol.183, p.105274, Article 105274
• Main Authors: van den Doel, Gregor J., Herder, Just L., Farhadi, Davood
• Format: Article
• Language: English
• Subjects: Elastic potential energy; Four-bar linkages; Kinematic singularity; Mechanisms
• ISSN: 0094-114X; 1873-3999
• DOI: 10.1016/j.mechmachtheory.2023.105274

The ability to convert reciprocating, i.e., alternating, actuation into rotary motion using linkages is hindered fundamentally by their poor torque transmission capability around kinematic singularity configurations. Here, we harness the elastic potential energy of a linear spring attached to the coupler link of four-bar mechanisms to manipulate force transmission around the kinematic singularities. We developed a theoretical model to explore the parameter space for proper force transmission in slider-crank and rocker-crank four-bar kinematics. Finally, we verified the proposed model and methodology by building and testing a macro-scale prototype of a slider-crank mechanism. We expect this approach to enable the development of small-scale rotary engines and robotic devices with closed kinematic chains dealing with serial kinematic singularities, such as linkages and parallel manipulators. [Display omitted] •A method is proposed to obviate kinematic singularity problems in four-bar linkages.•The approach enables to convert reciprocating actuation into rotary motion.•Design parameter space is explored for four-bar mechanisms with a crank link.•The proposed method is applicable over a range of length scale.