Compliant Mechanism Analysis And Experiments For A New Type Piezoelectric Inchworm Precision Actuator

Piezoelectric inchworm precision linear actuator based on the inchworm principle achieves a bidirectional large-travel and high-precision linear motion. According to existing main problems of inchworm actuators, flexure-based compliant mechanisms as the key components of inchworm actuator are systematically and deeply studied and a new walker type inchworm actuator is proposed. The main contents of this dissertation are considered of the following parts.Working principle and movement characteristics of various inchworm actuators are systematically analyzed and studied. According to the shortcomings of high processing requirements and adjustment difficulties of traditional walker type inchworm actuators, a new type inchworm actuator with a pair of parallel orientation axis as the orientation is proposed. This configuration facilitates the piezoelectric stack preload and the adjustment of the gap between friction surfaces, which reduces the processing requirements and improves system reliability. Structure scheme of this inchworm actuator is detailedly analyzed. Detailed design and analysis of the guiding shaft, copper sleeve and preload devices are conducted and the coupling characteristics between piezoelectric stack and complian mechanism are analyzed.Flexure-based compliant mechanisms as the key components of inchworm actuator are systematically and deeply studied. The accuracy characteristics of flexure hinge are studied. A rotational stiffness model for single-notch circular flexure hinge is established based on finite element method. Bridge-type compliant mechanism is proposed to be as the direct coupling mechanism of piezoelectric stack in intermediate drive mechanism and clamp mechanism. The effect of parasitic stiffness equations and the accuracy of rotational stiffness equations of flexure hinges on the overall performance are comprehensive studied. Accurate stiffness and stress model and natural frequency model based on energy method are established. The index of the error contribution rate is proposed, which facilitates the study of the effect of parasitic stiffness of flexure hinge on planar compliant mechanism. A simple optimum design procedure based on finite element method is proposed which achieves optimize static and dynamic performance of the compliant mechanism by changing geometrical dimensions according to performance requirements. The optimum results are verfied by finite element software ANSYS and the test. Accurate stiffness model of parallel-plate shifting pair is derived and the design parameters are presented, which are verfied by finite element method.According to the complex modeling and low efficiency of three-dimensional finite element model for inchworm actuator's compliant mechanism, analysis and comparison research on the euivalent beam model is carried out. Three-dimensional finite element model for circular flexure hinge as the basis of equivalent beam model is verified by comparison with experimental results. The accuracy of Timoshenko short-beam due to shear force is verified based on finite element method. The results show that the equivalent beam model has good accuracy. The equivalent beam model for a planar compliant mechanism with elliptical flexure hinges is presented and verified, which shows that the equivalent beam model can be applied to other types of flexure hinges. The equivalent beam model is also applied for the simulation optimal design of a bridge-type compliant mechanism and the results show that this modle has good accuracy and high efficiency and is suitable for the optimal design of inchworm actuator's complinat mechanisms.In order to verify the above mentioned model, special drive controller for piezoelectric inchworm actuator is designed, which is used to build the test system of inchworm actuator. Experimental tests are carried out in order to test and analysis the performance parameters of the actuator. Experiments results show that the proposed actuator is feasible and has good performance after further optimized, which provides the basis for further research.The new walker type inchworm actuator is a low-cost easy-assembly adjustable precision actuator while ensuring the travel, output force, speed and accuracy requirements and has certain positive significance for promoting the practical development and industrialization, which overcomes the shortcomings of traditional walker type inchworm actuators. The theoretical analysis method used in inchworm actuator compliant mechanism with direct coupling can also be used in planar compliant mechanism, so it has good generality...