| In general, to build the dynamic equation of mechanical system, inertia parameters of the system are needed, including a set of parameters: mass, the center of mass location and inertia tensor. High-accuracy inertia parameters are essential in the dynamic analysis of complex systems for the case that they determine the dynamic behavior of the systems directly. Therefore, technique of inertia parameters measurement is widely used in field of automobile and aerospace.Nevertheless, for bodies of complex shape or quality characteristic, it is hard to obtain their inertia parameters with high precision through theoretical calculations or three-dimensional modeling, it requires some measuring equipment to measure the inertia parameters directly. In view of this, a device based on 3-URU parallel mechanism for measuring the inertia parameters of rigid bodies is designed in this paper.Firstly, on the basis of comprehensive compare of the current equipment for the measurement of inertia parameters, a passive measurement scheme based on 3-URU parallel mechanism is determined. In this scheme, the measured rigid bodies are assembled on the mobile platform. When the initial position is given, the inertia parameters can be calculated by measuring the angular velocity and the acceleration of the mobile platform as long as the tensile forces along the branches of the parallel mechanism measured by the load cells.Secondly, the whole design of the measurement device is completed and the direct kinematic model of the parallel mechanism is set up. In structure design, the degree of freedom of the mechanism is analyzed and deformation checks of important parts are processed. As to the sensor design, the type selection of key sensor components is completed. Based on the kinematic model, the kinematic analysis and simulation of the parallel mechanism is accomplished.Then based on the general nonlinear equation of motion of free rigid bodies, the identification model for measuring the mass, the center of mass location and inertia tensor is built. The validity of the theoretical identification model is verified through simulation in ADAMS.In the end, using the developed VC++ user interface, the inertia parameters measurement experiments of standard masses are carried out on the experimental device. Comparing the theoretical inertia parameters of standard masses and the measured results, results show that the measuring system is of high precision. |
