關于機械手的中英文翻譯--機器人控制和裝配計劃相結(jié)合的精密機械手（英文）

1、Int J Adv Manuf Technol (2007) 31: 797–804 DOI 10.1007/s00170-005-0232-5ORIGINAL ARTICLEZhiqi Liu . Tatsuya Nakamura Combination of robot control and assembly planning for a precision manipulatorReceived: 22 March 2005 /

2、 Accepted: 1 August 2005 / Published online: 15 February 2006 # Springer-Verlag London Limited 2006Abstract This paper researches how to realize the auto- matic assembly operation on a two-finger precision manip- ulator.

3、 A multi-layer assembly support system is proposed. At the task-planning layer, based on the computer-aided design (CAD) model, the assembly sequence is first gen- erated, and the information necessary for skill decompo-

4、 sition is also derived. Then, the assembly sequence is decomposed into robot skills at the skill-decomposition layer. These generated skills are managed and executed at the robot control layer. Experimental results show

5、 the feasibility and efficiency of the proposed system.Keywords Manipulator . Assembly planning .Skill decomposition . Automated assembly1 IntroductionOwing to the micro-electro-mechanical systems (MEMS) techniques, many

6、 products are becoming very small and complex, such as microphones, micro-optical components, and microfluidic biomedical devices, which creates in- creasing needs for technologies and systems for the auto- mated precisi

7、on assembly of miniature parts. Many efforts aiming at semi-automated or automated assembly have been focused on microassembly technologies [1–3]. How- ever, microassembly techniques of high flexibility, effi- ciency, an

8、d reliability still open to further research. Thispaper researches how to realize the automatic assembly operation on a two-finger micromanipulator. A multi-layer assembly support system is proposed. Automatic assembly i

9、s a complex 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; the assembly planning and the robo

10、t control. At the assembly-planning phase, the information necessary for assembly operations, such as the assembly sequence, is generated. At the robot- control phase, the robot is driven based on the information generat

11、ed at the assembly-planning phase, and the as- sembly operations are conducted. Skill primitives can work as the interface of assembly planning to robot control. Several robot systems based on skill primitives have been

12、reported [4–6]. The basic idea behind these systems is the robot programming. Robot movements are specified as skill primitives, based on which the assembly task is manually coded into programs. With the programs, the ro

13、bot is controlled to fulfill assembly tasks automatically. A skill-based micromanipulation system has been developed in the authors’ lab, and it can realize many micromanipulation operations. In the system, the assembly

14、task is manually discomposed into skill sequences and compiled into a file. After importing the file into the system, the system can automatically execute the assembly task [7]. This paper attempts to explore a user-frie

15、ndly, and at the same time easy, sequence-generation method, to relieve the burden of manually programming the skill sequence. It is an effective method to determine the assembly sequence from geometric computer-aided de

16、sign (CAD) models. Many approaches have been proposed (e.g., [8– 11]). This paper applies a simple approach to generate the assembly sequence. It is not involved with the low-level data structure of the CAD model, and ca

17、n be realized with the application programming interface (API) functions that many commercial CAD software packages provide. In the proposed approach, a relations graph among different components is first constructed by

18、analyzing the assembly model, and then, possible sequences are searched, based onZ. Liu (*) PTC Japan Company, Oji 5-2-5-617, Kita-Ku, Tokyo, 114-0002, Japan e-mail: liuzhiqi@ecomp.metro-u.ac.jp Tel.: +81-426-7711-4246 F

19、ax: +81-426-7727T. Nakamura Department of Precision Engineering, Tokyo Metropolitan University, Kita-Ku, Japanconstraint, the remaining degrees of freedom are R1= {x, y, Rotz}. For the collinear constraint, the remaining

20、 degrees of freedom are R2={z, Rotz}. R1 and R2 can also be represented as R1={1, 1, 0, 0, 0, 1} and R2={0, 0, 1, 0, 0, 1}. Here, 1 means that there is a degree of separation between the two parts. R1∩R2={0, 0, 0, 0, 0,

21、1}, 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 b

22、roken before the mating direction is calculated. Under the assumption that all parts in the CAD model are fully constrained and not over- constrained, the following simple approach is adopted. For the part t in the loop,

23、 calculate the number of 1s in Nti ¼ Ri1 \ Ri2 \ . . . \ Rin; where Rik is the remaining degrees of freedom of constraint k by part i. For example, in Fig. 2, given that the number of 1s in UPart 5, Part 7 and UPart

24、 6, Part 7 is larger than UPart 5, Part 6 and UPart 6, Part 5, respectively, then it can be regarded that the position of Part 7 is determined by constraints with both Part 5 and Part 6, while Part 5 and Part 6 can be fu

25、lly constrained by constraints between Part 5 and Part 6. We can unite Part 5 and Part 6 as one node in the relation graph, also called a composite node, as shown in Fig. 2b. The composite node will be regarded as a sing

26、le part, but it is obvious that the composite node implies an assembly sequence. 2. Calculate mating directions for all nodes in the relation graph. Again, for the example in Fig. 3, beginning at the state that the shaft

27、 and the hole are assembled, separate the part in one degree of separation by a certain distance (larger than the maximum tolerance), and then check if interference occurs. Separation in both ±x axis and ±y axi

28、s of R1 causes the interference between the shaft and the hole. Separation in the +z direction raises no interference. Then, select the +z direction as the mating direction, which is represented as a vector M measured in

29、 the coordinate system of the assembly. It should be noted that, in some cases, theremay be several possible mating directions for a part. The condition for assembly operation in the mating direction to be ended should b

30、e given. When contact occurs between parts in the mating direction at the assembled state, which can be checked simply with geometric constraints, the end condition is measured by force sensory information, whereas posit

31、ion information is used as an end condition. 3. Calculate the grasping position. In this paper, parts are handled and manipulated with two separate probes, which will be discussed in the Sect. 4, and planes or edges are

32、considered for grasping. In the case that there are several mating directions, the grasping planes are selected as G1∩G2∩...∩Gi, where Gi is possible grasping plane/edge set for the ith mating direction when the part is

33、at its free state. For example, in Fig. 4, the pair planes P1/P1′, P2/P2′, and P3/P3′ can serve as possible grasping planes, and then the grasping planes are Gmating_dir1∩Gmating_dir2∩Gmating_dir3={P1/P1′, P2/ P2′, P3/P3

34、′}∩{P1/P1′, P3/P3′}n{P1/P1′, P2/P2′}={P1/ P1′}. The approaching direction of the end-effector is selected as the normal vector of the grasping planes. It is obvious that not all points on the grasping plane can be graspe

35、d. The following method is used to determine the grasping area. The end-effector, which is modeled as a cuboid, is first added in the CAD model, with the constraint of coplanar or tangential with the grasping plane. Begi

36、nning at the edge that is far away from the Base_Part in the mating direction, move the end-effector in the mating direction along the grasping plane until the end-effector is fully in contact with the part, the grasping

37、 plane is fully in contact with the end- effector, or a collision occurs. Record the edge and the distance, both of which are measured in the part’s coordinate system. 4. Separate gradually the two parts along the mating

38、 direction, while checking interference in the other degrees of separation, until no interference occurs in all of the other degrees of separation. There is obviously a separation distance that assures interference not t

39、o occur in every degree of separation. It is called the safe length in that direction. This length is used for the collision-free path calculation, which will be discussed in the following section.2.2 Assembly sequenceSo

40、me criteria can be used to search the optimal assembly sequence, such as the mechanical stability of subassem- blies, the degree of parallel execution, types of fixtures, etc.Fig. 4 Grasping planesFig. 3 Geometric constr