Flexibility calculation and performance analysis of a new single-sided straight-circle-ellipse hybri

Abstract:

Flexible hinges have gained significant popularity in the field of micro-electromechanical systems (MEMS). This paper introduces a novel type of flexible hinge, namely the single-sided straight-circle-ellipse hybrid flexible hinge. Leveraging Karl's second theorem, a computational formula for the flexibility of circular and elliptical hybrid flexible hinges is proposed. The derived formula is validated through finite element analysis and comparative analysis. The impact of each structural parameter of the unilateral hybrid flexible hinge on its flexibility is analyzed. Furthermore, a comparison is made with the double-sided straight-circle-ellipse hybrid flexible hinge to demonstrate the superior rotation capacity and load sensitivity of the unilateral design. The proposal of unilateral hybrid flexible hinges presents a new avenue for engineering applications requiring compact structures and large displacements.

The advent of micro-electromechanical technology, aerospace engineering, and biological engineering has highlighted the limitations of traditional rigid mechanisms in meeting design and usage requirements. Flexible mechanisms offer numerous advantages such as small size, absence of mechanical friction, no gaps, and high motion sensitivity. This has led to their extensive use in various disciplines, including machinery, robotics, computers, automatic control, and precision measurement. The key component of flexible mechanisms is the flexible hinge, which eliminates lost motion and mechanical friction through elastic deformation and self-recovery properties, allowing for higher displacement resolutions. Single-axis flexible hinges are classified into various shapes, such as arc, lead angle, ellipse, parabola, and hyperbola. Among them, the straight-round and lead angle types are widely employed due to their simple structures. However, in certain applications where space is limited, single-sided flexible hinges have emerged as a preferred choice, finding utility in precision measurement and positioning.

Methods:

Building upon the aforementioned research, this study proposes a new type of flexible hinge called the unilateral hybrid flexible hinge, which combines the advantages of hybrid and unilateral flexible hinges. The flexibility calculation formula for this hinge is derived based on Karl's second theorem, and its performance is verified through finite element analysis. The study also examines the influence of various structural parameters on the flexibility of the hinge.

Results and Discussion:

The flexibility calculation formula for the unilateral straight-circle-ellipse hybrid flexible hinge indicates that flexibility is dependent on both material and structural parameters. The derived formula demonstrates that flexibility parameters are inversely proportional to the hinge's width, while parameters such as straight-circle radius, ellipse semi-major axis, semi-minor axis, and minimum thickness also influence flexibility. Through analysis, it is observed that flexibility decreases with an increase in the semi-minor axis of the ellipse, increases with a decrease in the minimum thickness, and changes non-linearly with varying thickness. The influence of minimum thickness on flexibility is found to be more significant compared to other parameters.

A comparison is drawn between the unilateral straight-circle-ellipse hybrid flexible hinge and the double-sided straight-circle-ellipse hybrid flexible hinge proposed in prior literature. Flexibility is identified as the most vital characteristic of flexible hinges, and a relative flexibility ratio, denoted as Cday, is introduced to compare the two hinge designs. The analysis reveals that the unilateral hybrid flexible hinge exhibits greater rotation capacity and load sensitivity compared to the bilateral design. The flexibility of the unilateral hybrid flexible hinge is approximately 1.37 times higher than that of the bilateral design.

This study presents a comprehensive analysis of the unilateral hybrid flexible hinge, an innovative flexible hinge design that offers compact structures and large displacements. The derived flexibility calculation formula is validated through finite element analysis, demonstrating an error within 8%. The influence of structural parameters on flexibility is analyzed, with the minimum thickness of the hinge identified as the most influential parameter. Furthermore, a comparison with the bilateral hybrid flexible hinge highlights the superior performance of the unilateral design in terms of rotation capacity and load sensitivity. The proposed unilateral hybrid flexible hinge opens up new possibilities for the engineering application of flexible hinges in various industries.