Papers by Author: Yi Tong Zhang

Abstract: Strong coupling is one of the prominent features of the general parallel mechanisms(Par. Mec.), which has led to difficulty in the trajectory planning and precision control. To solve this problem, the designing of motion decoupled parallel mechanisms(Dec. Par. Mec.) has become a hot topic. This paper, based on the work achieved in our pre-papers, is to make an improvement on the criterion for a branch type synthesis of the rotational decoupled parallel mechanisms(Rot. Dec. Par. Mec.), which ensures the decoupling of the rotations in each limb. This paper focuses on a type synthesis of the decoupled parallel mechanisms with two degree of freedoms (DOFs). Decoupled parallel manipulators with two parallel kinematic chains, one of which is of type 2R(R represents rotation), are taken into consideration in this paper. A large number of novel decoupled architectures are already obtained, some of which have got an application for a China Patent. What has been done in this paper is carried out by means of the screw theory, which has effectively avoided complex equations by synthesis.

Abstract: Deficiencies are existed for currently formulas of mobility calculation for planar mechanism. They are not suitable for planar mechanism with virtual constraints and the number of general constraints equal to 4. To solve the problem, the new concepts of virtual loop, virtual-loop constraint and virtual pair are defined to establish a general f ormula for DOF of planar mechanism; the calculation method for virtual-loop constraint and the mobility of link-group are also given. It is proved that the new formula is correct, general, simple and effective through the mobility analysis of several different kinds of planar mechanisms.

Abstract: Deficiencies are existed for currently formulae of mobility calculation for single loop mechanism. It doesn't reflect the constraint imposed to output components by link group. By analyzing the kinematic parameters of link groups, this paper proposes a new method to calculate the mobility of link group, which is the difference of the sum of the degree of freedoms (DOFs) of all the kinematic pairs and the rank of the kinematic parameters of link groups. Also the DOF can be obtained by the total DOFs of link groups and the rank of kinematic parameters of basis point of the output link. It can be concluded that the new method can not only express the move state of the output link, but the constraint imposed to output components by link group also be reflected. The research results can provide a reference for the structural analysis of the single loop.

Abstract: In view of the special characteristics of cams grinding, some key technologies of grinding force adaptive control system are researched, including selection of inspecting parameter, modeling of grinding feed system, and design of controller. Results of simulation indicate that this system can ensure circular grinding force steady and enhance the machining quality of cams when the grinding allowance is of variety.

Abstract: The accurate calculation and the approximate calculations of the cylinder cam’s curve enveloping surface in single-tool-position-compensation are compared. It is proved that the approximate formula is enough precision for engineering purpose. Based on the analyses for the approximate formula, the calculating method of the least feeding times of the multi-tool-position-compensation is proposed. This method provides theoretical foundation for complex surface’s high efficiency and great precision grinding as well as optimal machining control.

Abstract: A basic method and characteristic of tool’s radial offset for conical enveloping surface, its structure and working theory as well as the most advanced planetary grinding head used in tool’s radial offset in the world are introduced. In order to improve the dynamic property of grinding head and method used in tool’s offset in existence, a new type of grinding head that can realize tool’s radial offset to big tool’s radial error was developed. It has the advantages of simpler structure, easier machining, lower cost, continuous and stable machining, and high efficiency, and is a new method of complex tool’s position offset.