Research On Vibration Characteristics Of Multi-dof Mechanism Based On Screw Theory

Multi-DOF shake table is the effective tool of structural reliability test，seismiccertification and vibration isolation test. It will be expensive to manufacture theearthquake table that is mainly studied. This paper tries to study vibration simulation withlow-cost electric motor units to meet some small devices.The shake table could generate shock waves of different frequencie and must avoidthe natural frequency. Because of the kinematics and dynamics of parallel mechanism isdifferent in different pose, it is necessary to establish the vibration model and obtainnatural frequency in different pose. This article studies dynamics, vibration model and thenatural frequencies of parallel mechanism. The main research contents are as follows:(1) According to the theoretical mechanics, the vibration model of single and twodegrees of freedom serial mechanism are established.The dynamic model and simplifiedvibration model of plane serial RRP mechanism are built based on screw theory, and thenatural frequencies is calculated. The natural frequencies in a variety of parameters werevalidated by Adams.(2) Dynamics model and vibration modeling of Stewart agency are built based onscrew theory, and the natural frequencies and mode shapes of regular are calculated. Thenatural frequency in each direction has been verified by Adams. The vibrationcharacteristic of Stewart institutions under different parameters is studied.(3)Two vibration models are sum up and the accuracy is compared base on theinherent frequency. Evaluation of vibration model is obtained with branch inertial forceOmited. Institutions parameter is optimized based on first natural frequency of themechanism, and the system response is obtained under the excitation force.(4) A6-RPC and a3-RRS mechanism are selected as vibration simulation platformconfiguration. The dynamics modeling agencies and vibration modeling are calculated.The natural frequency and driving forces under different pose are obtained.