Design of Two‐Segment Constant‐Force Compliant Mechanisms via Stiffness‐Matched Parallel Integration

This study presents a well‐defined design paradigm for multi‐segment constant‐force compliant mechanisms (CFCMs). These CFCMs are capable of achieving dual‐stage zero‐stiffness characteristics via innovative stiffness hybridization. To tackle the critical limitation of conventional single‐range constant‐force mechanisms, we put forward two distinct configurations: a discrete two‐state CFCM equipped with reconfigurable stiffness modules, and a continuous dual‐stage architecture that employs cascaded negative stiffness elements. The core innovation is centered on the synergistic integration of positive‐stiffness structures with hierarchical negative‐stiffness mechanisms, namely bistable beams and their compensated derivatives, to establish overlapping zero‐stiffness regimes. By means of analytical modeling using elliptic integrals and pseudo‐rigid‐body approximations, combined with finite element validation, we illustrate that the mechanisms can sustain constant forces of 4 N (1.2–5.6 mm) and 20 N (12.2–15.1 mm) within continuous motion trajectories. Experimental characterization of 3D‐printed prototypes confirms that the force variation is less than 5% across the designated displacement ranges, and it attains an extension of the operational range in comparison with single‐stage counterparts. This stiffness engineering framework offers multi‐phase force regulation capabilities for applications that demand adaptive interaction forces, spanning from precision microassembly to bio‐compatible robotic manipulation.