Classification and type synthesis of deficient-DOF parallel/hybrid compound load simulator with a specified load pattern

A compound load simulator has drawn increasing attention due to the growing demand for testing of critical components in mechanical devices. However, its development is still limited owning to the shortage of corresponding design principle. Accompanied with the application of parallel mechanisms in a variety of multi-axis machine tools and motion simulators, it brings new inspiration to this field. Although existing six degree-of-freedom (DOF) parallel mechanisms such as Stewart platform can output multi-dimensional loads, it also produces the complexity of force control and inevitable collaborative error. Actually, it is enough to utilize deficient-DOF mechanisms for a majority of load patterns and practical engineering applications. Therefore, this paper mainly focuses on synthesizing deficient-DOF parallel/hybrid compound load simulators. Regular load types are summarized including one-dimensional generalized force and compound of them. Based on characteristics of each load type, DOF of the moving platform connecting to the component to be tested is determined through the mapping between force and displacement in rigid body motion. Current typical deficient-DOF parallel mechanism is enumerated to evaluate its load output characteristics. What is more important, a type synthesis procedure based on the graphic approach is presented to construct the configurations of parallel/hybrid mechanism corresponding to different compound load types, which may lead to useful load simulator configurations. The procedure also verifies that the graphic approach is a concise and effective method to synthesize the load simulators associated with a specified load pattern.