Design of a Novel Compliant Constant-Force Mechanism with High Lateral Stiffness

Compliant constant-force mechanisms (CCFMs) are widely used in overload protection, surgical manipulation and polishing/deburring to provide a near constant-force output over a range of displacement. This work proposes a novel CCFM that comprises a diaphragm mechanism and a bistable mechanism using the building block method. The diaphragm mechanism and bistable mechanism are employed to provide the positive and negative stiffness over the range of the displacement, respectively. The positive and negative stiffness modules are connected in parallel so that to output a constant-force in a large range of displacement with less variation. The chained spatial beam constraint model (CSBCM) is developed to model the spatial deflection of the initially curved beams in the diaphragm mechanism and the chained beam constraint model (CBCM) is used to derive the load–displacement relation and stress properties of the bistable mechanism. To eliminate the force variation, the realized optimization of the geometric parameters, and the optimal geometric parameters are employed to form the CCFM to output a constant-force in a large range of displacement with very small variation.