英文原文Research on a Novel Parallel Engraving Machine and its Key TechnologiesAbstract: In order to compensate the disadvantages of conventional engraving machine and exert the advantages of parallel mechanism, a novel parallel engraving machine is presented and some key technologies are studied in this paper. Mechanism performances are analyzed in terms of the first and the second order influence coefficient matrix firstly. So the sizes of mechanism, which are better for all the performance indices of both kinematics and dynamics, can be confirmed and the restriction due to considering only the first order influence coefficient matrix in the past is broken through. Therefore, the theory basis for designing the mechanism size of novel engraving machine with better performances is provided. In addition, method for tool path planning and control technology for engraving force is also studied in the paper. The proposed algorithm for tool path planning on curved surface can be applied to arbitrary spacial curved surface in theory, control technology for engraving force based on fuzzy neural network (FNN) has well adaptability to the changing environment. Research on teleoperation for parallel engraving machine based on B / S architecture resolves the key problems such as control mode, sharing mechanism for multiuser, real-time control for engraving job and real-time transmission for video information. Simulation results further show the feasibility and validity of the proposed methods. Keywords: parallel mechanism, engraving machine, influence coefficient, performance indices, tool path planning, force control, fuzzy neural network, teleoperation1 IntroductionConventional computer engraving machine has played an important role in industries such as machinery machining, printing and dyeing and entertainment, but it has the inherent disadvantages such as cutting tool can be fed only along the fixed guideway, lower degree-of-freedom (DOF) of cutting tool, lower flexibility and mobility for machining etc. Parallel mechanism has the merits such as high mechanical stiffness, high load capacity, high precision, good dynamic performance etc (Zhen, H.; Ling-fu, K. & Yue-fa, F., 1997). According to the characteristics of parallel mechanism, it has been a hot research topic to apply parallel mechanism to the domain of future machining. By applying parallel mechanism to engraving domain, its inherent advantages can be fully exerted and the disadvantages of conventional engraving machine can be overcome or compensated. But as the special structure of parallel mechanism, the related theory and technology during its engraving is very different from that of conventional engraving machine, and it is a undeveloped research topic by now. In addition, with the development of computer network technology, the new concept and method such as network machining and manufacturing has become hot research topic (GQ, Huang & K.L, Mak., 2001; Taylor, K. & Dalton, B., 2000; Ying-xue, Y. & Yong, L., 1999). A novel parallel engraving machine with six-axis linkage is proposed in this paper, which uses the 6-PUS parallel mechanism with 6-DOF as the prototype, and some key technologies such as size design, tool path planning, engraving force control and teleoperation are studied on this basis.2. Confirming of mechanism type and engraving machines size2.1 Selection of mechanism and coordinate systemThe selection of mechanism type is the first step for designing novel engraving machine, the following reasons make us select the 6-PUS parallel mechanism for designing our engraving machine. Comparing with traditional mechanism, 6-PUS parallel mechanism uses base platform, three uprights layout and high rigidity framework structure and has the merits such as high modularization, high accuracy and low cost. Itsmodel is shown in Fig.1.Fig. 1. The model of 6-PUS parallel mechanismAs shown in Fig.1, 6-PUS parallel mechanism consists of base platform, dynamic platform and 6 branch chains with same structure, every branch joins with base platform through prismatic pairs (P), slider of prismatic pairs joins with up end of the fixed length link through universal joint (U), down end of the fixed length link joins with dynamic platform through sphere hinge (S), so it is called 6-PUS parallel mechanism. The coordinate system of 6-PUS parallel engraving mechanism is shown in Fig. 2. In Fig.2, the geometry centers of base platform and dynamic platform plane are supposed as OB and op respectively. In every branch, the centers of prismatic pairs, universal joint and sphere hinge are marked with Ai, Bi, and Ci (i = 1,2, ., 6) respectively. Coordinate system OB-XBYBZB is fixed on base platform, taking B as briefly. The origin of B lies on geometry center of base platforms up plane, axis ZB is vertical with base platform and directs to up, axis YB directs to angle bisector of the first and second branch lead screw cen