Stiffness Analysis and Experimental Test of Planar Flexible Hinge Guide Mechanism_Hinge Knowledge_Ta

A flexible hinge is a mechanical mechanism that utilizes reversible elastic deformation of materials to transmit motion and energy. It finds applications in various fields such as aerospace, manufacturing, optics, and bioengineering. In recent years, there has been an increasing use of flexible hinges in engineering technology fields like micro-positioning, measurement, optical platforms, micro-adjustment mechanisms, and large-scale antenna space deployment mechanisms.

The key advantage of a flexible hinge is its integrated design that allows for motion and energy transmission without any backlash, friction, gap, noise, wear, and with high motion sensitivity. One specific type of flexible hinge is the planar flexible hinge, which is typically made using ordinary leaf springs. The planar flexible hinge offers a simple structure assembly and low processing cost, making it especially suitable for precision mechanical design.

There are four common structural forms of flexible hinge guide mechanisms, namely Type I, Type II, Type III, and Type IV. These mechanisms are often used for high-precision guidance in various applications. Among them, Type I is a semi-straight circular flexible hinge guide mechanism known for its compact structure and stability. However, it can be prone to fatigue. Type II is a parallel reed guide mechanism with a reinforcing plate, which offers more parts but has reduced fatigue resistance compared to Type I. Type III is a simpler parallel reed guide mechanism but lacks overall stability. Type IV, the planar flexible hinge guide mechanism, overcomes the weaknesses of Type I and is more stable than Type III. It has great potential for various applications.

While the first three types of flexible guide mechanisms have been extensively discussed in the literature, the planar flexible hinge guide mechanism (Type IV) is not commonly used in practice, and there is a lack of relevant design theory in current literature. This paper aims to bridge that gap by providing a theoretical derivation of the bending stiffness of the planar flexible hinge and the stiffness analysis formula of the guiding mechanism. It also includes experimental testing to validate the analytical formula's accuracy.

The bending stiffness of the planar flexible hinge is derived based on the bending moment equation of material mechanics. The structure of the planar hinge part is analyzed, considering the dimensions and properties of the stainless steel plate used. The derived analytical formula provides a theoretical basis for understanding the stiffness of the hinge.

To verify the analytical formula, a set of parallelogram guide mechanisms employing planar flexible hinges is designed and processed. Experimental testing is conducted using a spring tension and compression instrument to measure the force-displacement relationship of the mechanism. The test results are compared to the analytical formula's calculations, and a good agreement is found, albeit with a small relative error of 4.7%. The discrepancy is attributed to the fact that the analytical formula only considers the deformation of the hinge part and not the entire reed.

The practical application of the planar flexible hinge guide mechanism is demonstrated through the design of a one-dimensional measuring head anti-collision device for a CNC gear measuring center. This device combines a one-dimensional TESA probe, a planar flexible guide mechanism, and a position sensor to ensure the safety protection of the probe.

In conclusion, this study provides a theoretical derivation and experimental validation of the stiffness of the planar flexible hinge guide mechanism. The analytical formula shows good accuracy, albeit with slight discrepancies due to the simplifications made in the formula. Future research should consider the deformation of the entire reed and other influencing factors to improve the calculation accuracy of the hinge's stiffness. The practical application of the planar flexible hinge guide mechanism demonstrates its potential for various engineering applications.