针对传统常力机构存在的运动副间隙、装配误差和摩擦磨损等问题, 设计了一种基于柔顺机构的常力微动平台。平台利用直梁正刚度和双稳态梁屈曲行为产生负刚度来实现其零刚度特性。平台由对称的直梁、双稳态梁和刚性连接块组成, 直梁和双稳态梁通过连接块并联连接。采用伪刚体法和椭圆积分法相结合的建模方法, 建立反映常力平台力学性能的理论模型。通过与有限元分析结果进行比较, 分析结果显示所建立的模型能准确反映常力平台的力学性能。基于所建立的力学模型, 提出一种提高平台常力运动范围和承载能力的优化设计方法。制作样机对该平台力学性能进行实验测试, 实验结果表明, 平台能在输出位移范围为 ［0.6~1.7］mm内能够保持约48 N常力, 证明了常力平台设计思路的可行性、所建模型的准确性和优化方法的有效性。

To address the movement pair gap, assembly error, friction, and wear of the traditional constant-force mechanism, a constant-force micro-motion stage based on a compliant mechanism was presented. The goal of the design was to acquire zero stiffness of the stage by using the positive stiffness of a straight beam and the negative stiffness caused by the buckling behavior of a bistable beam. The stage consisted of a symmetric straight flexible beam, bistable beam, and rigid connection block. The straight flexible beam and bistable beam were connected in parallel by using the rigid connection block. A method that combined the presido-rigid-body and elliptic-integral was proposed to establish a theoretical model reflecting the mechanical properties of the constant-force mechanism. The analysis results verified the appropriateness of the theoretical model by comparing the results of the finite element simulation. An optimal design method for improving the constant-force motion range was proposed based on the established mechanical model. A prototype of the stage was made, and the mechanical properties of the stage are tested experimentally. The experimental results show that the stage can maintain constant force of about 48 N in the output displacement range of ［0.6-1.7］ mm. In addition, they illustrate the feasibility of the design idea, the accuracy of the proposed model, and the effectiveness of the optimization method of the stage.