Adaptive impact mitigation and bifurcation analysis in clearance-containing mechanisms using an adjustable force element

Servo presses play a critical role in the fabrication of metal bipolar plates for hydrogen fuel cells. However, kinematic pair clearances lead to significant degradation in their dynamic performance, compromising operational stability and manufacturing precision. To address this issue, this study introduces an adjustable force element into the six-bar mechanism of servo presses to mitigate clearance-induced impacts. The system dynamic equations, incorporating a clearance impact model, are systematically derived using the Lagrangian approach. The contact forces at clearance joints are modeled by the Lankarani-Nikravesh method, enabling accurate representation of the nonlinear dynamics caused by clearances. Based on the proposed adjustable force model, a new performance indicator is developed, with the clearance penetration rate defined as the key evaluation criterion, optimizing model parameters. Results show a 98.7% reduction in impact disturbances and a 61.3% decrease in the maximum driving torque amplitude. Moreover, the velocity-acceleration phase portraits of the slider and bifurcation diagrams of displacement deviation are meticulously analyzed to comprehensively characterize the control effect on the system’s motion accuracy. In essence, the findings underscore the substantial potential of the adjustable force method in suppressing impacts and enhancing the dynamic accuracy of multi-body systems with clearances.