基于动力学的双稳态机构驱动特性分析

Analysis of Driving Characteristic of Bistable Mechanism based on Dynamics

柔性双稳态机构是一种在无外部输入的情况下,可以保持两个稳定平衡位置的机构,在MEMS和机械传动领域中有广泛的应用。对柔性机构稳态的判别一般使用能量法,但能量法无法对柔性机构的驱动特性进行分析。为此提出一种基于动力学的柔性四杆机构稳态分析方法,对只含一个柔性关节的四杆机构的驱动特性进行分析,并根据驱动特性曲线对柔性机构的稳态特性进行判断。首先,建立柔性四杆机构的伪刚体模型,利用拉格朗日方程建立动力学模型,解算出主动杆件旋转360°时驱动力的变化曲线;然后,在ADAMS中建立对应的柔性四杆机构模型,将仿真结果与动力学解算结果进行对比,验证动力学模型的准确性;最后,通过一个算例将提出的动力学分析方法与传统能量法的分析结果进行对比,证明动力学分析方法的有效性,同时还可以得到机构在稳态位置与非稳态位置转换过程中驱动力的临界值,为柔性稳态机构的设计提供一种新的方法。提出的基于动力学的双稳态驱动特性,在双稳态开关、双稳态传感器中都可以被设计和应用。

A compliant bistable mechanism is a device that can maintain two distinct positions without power input. There is a wide range of applications in the field of MEMS and mechanical transmission. Usually,the energy method is used for judging the steady state of compliant mechanism,but the driving characteristic of compliant mechanism can＇t be analyzed. A new method for the steady state analysis of four bar mechanism based on dynamics is presented to analyze the driving characteristic of four bar mechanism with only a compliant joint.And according to the drive characteristic curve,the steady state characteristics of the flexible mechanism are judged. Firstly,the pseudo- rigid body model of the compliant four bar mechanism is established by using pseudo- rigid body method,and the dynamic equations are listed by using the Lagrange equation of the second kind. The change curve of driving force is calculated when the active member is rotated 360°. Then the corresponding flexible four bar mechanism model is established in ADAMS,and the simulation results are compared with the results of the dynamics calculation to verify the accuracy of the dynamics model. Finally,a numerical example is given to compare the dynamics analysis method with the traditional energy method. The results show that the dynamics analysis method is effective. At the same time,the critical value of the driving force in the process of steady state and non steady state position conversion are obtained,and a new method for the design of the flexible steady state mechanism is provided. At the same time,based on the dynamics characteristic of bistable state,the bistable switches and sensor can be designed and used.