【正文】 onto the Base_Part. Operation describes how the Assembly_Part is assembled with the Base_Part。 徐州工程學院畢業(yè)設計 外文翻譯 學生姓名 學院名稱 專業(yè)名稱 指導教師 20**年 5 月 27 日 COMBINATION OF ROBOT CONTROL AND ASSEMBLY PLANNING FOR A PRECISION MANIPULATOOR Abstract This paper researches how to realize the automatic assembly operation on a twofinger precision manipulator. A multilayer assembly support system is proposed. At the taskplanning layer, based on the puteraided design (CAD) model, the assembly sequence is first generated, and the information necessary for skill deposition is also derived. Then, the assembly sequence is deposed into robot skills at the skilldeposition layer. These generated skills are managed and executed at the robot control layer. Experimental results show the feasibility and efficiency of the proposed system. Keywords Manipulator Assembly planning Skill deposition Automated assembly 1 Introduction Owing to the microelectromechanical systems (MEMS) techniques, many products are being very small and plex, such as microphones, microoptical ponents, and microfluidic biomedical devices, which creates increasing needs for technologies and systems for the automated precision assembly of miniature parts. Many efforts aiming at semiautomated or automated assembly have been focused on microassembly technologies. However, microassembly techniques of high flexibility, efficiency, and reliability still open to further research. Thispaper researches how to realize the automatic assembly operation on a twofinger micromanipulator. A multilayer assembly support system is proposed. Automatic assembly is a plex problem which may involve many different issues, such as task planning, assembly sequences generation, execution, and control, etc. It can be simply divided into two phases。 Operation ∈ {Insertion_T, screw_T, align_T,...}. The structure of microparts is usually unplicated, and they can be modeled by the constructive solid geometry (CSG) method. Currently, many mercial CAD software packages can support 3D CSG modeling. The assembly model is represented as an object that consists of two parts with certain assembly relations that define how the parts are to be assembled. In the CAD model, the relations are defined by geometric constraints. The geometric information cannot be used directly to guide the assembly operation—we have to derive the information necessary for assembly operations from the CAD model. Through searching the assembly tree and geometric relations (mates’ relations) defined in the assembly’s CAD model, we can generate a relation graph among parts, for example, In the graph, the nodes represent the parts. If nodes are connected, it means that there are assembly relations among these connected nodes (parts). Mating direction In CSG, the relations of two parts, geometric constraints, are finally represented as relations between planes and lines, such as collinear, coplanar, tangential, perpendicular, etc. For example, a shaft is assembled in a hole. The assembly relations between the two parts may consist of such two constraints as collinear between the centerline of shaft Lc_shaft and the centerline of hole Lc_hole and coplanar between the plane P_Shaft and the plane P_Hole. The mating direction is a key issue for an assembly operation. This paper applies the following approach to pute the possible mating direction based on the geometric constraints (the shaftinhole operation of Fig. 3 is taken as an example): 1. For a part in the relation graph, calculate its remaining degrees of freedom,also called degrees of separation, of each geometric constraint. For the coplanar constraint, the remaining degrees of freedom are ? ?zRotyxR ,1 ? . For the collinear constraint, the remaining degrees of freedom are ? ?zRotzR ,2 ? . 1R and 2R can also be represented as ? ?1,0,0,0,1,11 ?R and ? ?1,0,0,1,0,02 ?R . Here, 1 means that there is a degree of separation between the two parts. ? ?1,0,0,00,021 ，?? RR , and so, the degree of freedom around the z axis will be ignored in the following steps. In the case that there is a loop in the relation graph, such as parts Part 5, Part 6, and Part 7 in Fig. 2, the loop has to be broken before the mating direction is calculated. Under the assumption that all parts in the CAD model are fully constrained and not overconstrained, the following simple approach is adopted. For the part t in the loop, calculate the number of 1s in ??? iniiti RRRN ...21? 。 some other parts may have been assembled with the base part) in the workspace so that the mating direction is kept upside. 4. In the CAD model, move the assembly part to the base part in the possible mating direction, while checking if interference (collision) occurs. If interference occurs, mark the base node as an inactive node and go to step 2, whereas select the Operation type according to parts’ geometric features. In this step, an Obstacle Box is also puted. The box, which is modeled as a cuboid, includes all parts in the workspace. It is used to calculate the collisionfree path to move the assembly part, which will be introduced in the following section. The Obstacle Box is described by a position vector and its width, height, and length. 5. Record the assembly sequence with the Operation type, the mating direction, and the grasping position. 6. If all nodes have been searched, then mark the first base node as an inactive node and go to step 2. If not, select a node connected with the assembly node. Mark it as an assembly node, and the assembly node is updated as a base node. Check if there is one of the mating directions of the assembly node that is same as the mating direction of the former assembly node. If there is, use the former mating directi