机器人路径规划毕业论文外文翻译.docx

1、机器人路径规划毕业论文外文翻译(此文档为word格式，下载后您可任意编辑修改！)外文文献：Space Robot Path Planningfor Collision AvoidanceYuya Yanoshita and Shinichi TsudaAbstract This paper deals with a path planning of space robot which includes a collision avoidance algorithm. For the future space robot operation, autonomous and self-contai

2、ned path planning is mandatory to capture a target without the aid of ground station. Especially the collision avoidance with target itself must be always considered. Once the location, shape and grasp point of the target are identified, those will be expressed in the configuration space. And in thi

3、s paper a potential method.Laplace potential function is applied to obtain the path in the configuration space in order to avoid so-called deadlock phenomenon. Improvement on the generation of the path observed by applying path smoothing method, which utilizes the spline function interpolation. This

4、 reduces the computational load and generates the smooth path of the space robot. The validity of this approach is shown by a few numerical simulations.Key Words Space Robot, Path Planning, Collision Avoidance, Potential Function, Spline InterpolationI. INTRODUCTIONIn the future space development, t

5、he space robot and its autonomy will be key features of the space technology. The space robot will play roles to construct space structures and perform inspections and maintenance of spacecrafts. These operations are expected to be performed in an autonomous. In the above space robot operations, a b

6、asic and important task is to capture free flying targets on orbit by the robotic arm. For the safe capturing operation, it will be required to move the arm from initial posture to final posture without collisions with the target.The configuration space and artificial potential methods are often app

7、lied to the operation planning of the usual robot. This enables the robot arm to evade the obstacle and to move toward the target. Khatib proposed a motion planning method, in which between each link of the robot and the obstacle the repulsive potential is defined and between the end-effecter of the

8、 robot and the goal the attractive potential is defined and by summing both of the potentials and using the gradient of this potential field the path is generated. This method is advantageous by its simplicity and applicability for real-time operation. However there might be points at which the repu

9、lsive force and the attractive force are equal and this will lead to the so-called deadlock.In order to resolve the above issue, a few methods are proposed where the solution of Laplace equation is utilized. This method assures the potential fields without the local minimum, i.e., no deadlock. In th

10、is method by numerical computation Laplace equation will be solved and generates potential field. The potential field is divided into small cells and on each node the discrete value of the potential will be specified. In this paper for the elimination of the above defects, spline interpolation techn

11、ique is proposed. The nodal point which is given as a point of path will be defined to be a part of smoothed spline function. And numerical simulations are conducted for the path planning of the space robot to capture the target, in which the potential by solving the Laplace equation is applied and

12、generates the smooth and continuous path by the spline interpolation from the initial to the final posture.II. ROBOT MODELThe model of space robot is illustrated in Fig.1.The robot is mounted on a spacecraft and -plane motion of the end-effecter. In this case we additional freedom of the spacecraft

13、attitude angle and this will be considered the additional rotary joint. This means that the space robot is three linked with 3 DOF (Degree Of Freedom). The length of each link and the angle of each rotary joint are given byand (i = 1,2,3) , respectively. In order to simplify the discussions a few as

14、sumptions are made in this paper:-the motion of the space robot is in-plane,i.e., two dimensional one.-effect of robot arm motion to the spacecraft attitude is negligible.-robot motion is given by the relation of static geometry and not explicitly depending on time.-the target satellite is inertiall

15、y stabilized.In general in-plane motion and out-of-plane motion will be separately performed. So we are able to assume the above first one without loss of generality. The second assumption derives from the comparison of the ratio of mass between the robot arm and the spacecraft body. With respect to

16、 the third assumption we focus on generating the path planning of the robot and this is basically given by the static nature of geometry relationship and is therefore not depending on the time explicitly. The last one means the satellite is cooperative.Fig.1 Model of Two-link Space RobotIII. PATH PL

17、ANNING GALGORITHMA. Laplace Potential GuidanceThe solution of the Laplace equation (1) is called a Harmonic potential function, and its and minimum values take place only on the boundary. In the robot path generation the boundary means obstacle and goal. Therefore inside the region where the potenti

18、al is defined, no local minimum takes place except the goal. This eliminates the deadlock phenomenon for path generation. （1）The Laplace equation can be solved numerically. We define two dimensional Laplace equation as below: （2）And this will be converted into the difference equation and then solved

19、 by Gauss -Seidel method. In equation (2) if we take the central difference formula for second derivatives, the following equation will be obtained: （3）where， are the step (cell) sizes between adjacent nodes for each x, y direction. If the step size is assumed equal and the following notation is use

20、d:Then equation (3) is expressed in the following manner: （4）And as a result, two dimensional Laplace equation will be converted into the equation (5) as below: （5）In the same manner as in the three dimensional case, the difference equation for the three dimensional Laplace equation will be easily o

21、btained by the following: （6）In order to solve the above equations we apply Gauss-Seidel method and +1 )-th iterative calculations of the potential. In the above computations, as the boundary conditions, a certain positive number is defined for the obstacle and 0 for the goal. And as the initial con

22、ditions the same number is also given for all of the free nodes. By this approach during iterative computations the value of the boundary nodes will not change and the values only for free nodes will be varying. Applying the same potential values as the obstacle and in accordance with the iterative

23、computational process, the small potential around the goal will be gradually propagating like surrounding the obstacle. The potential field will be built based on the above procedure.Using the above potential field from 4 nodal points adjacent to the node on which the space robot exists, the smalles

24、t node is selected for the point to move to. This procedure finally leads the space robot to the goal without collision.B. Spline InterpolationThe path given by the above approach does not assure the smoothly connected one. And if the goal is not given on the nodal point, we the cells into much more

25、 smaller cells. This will increase the computational load and time.In order to eliminate the above drawbacks we propose the utilization of spline interpolation technique. By assigning the nodal points given by the solution to via points on the path, we try to obtain the smoothly connected path with

26、accurate initial and final points.In this paper the cubic spline was applied by using MATLAB command.C. Configuration SpaceWhen we apply the Laplace potential, the path search is assured only in the case where the robot is expressed to be a point in the searching space. The configuration space(C-Spa

27、ce), where the robot is expressed as a point, is used for the path search. To convert the real space into the C-Space the calculation to judge the condition of collision is performed and if the collision exists, the corresponding point in the C-space is regarded as the obstacle. In this paper when t

28、he potential field was generated, the conditions of all the points in the real space, corresponding to all the nodes, were calculated. The judgment of intersection between a segment constituting the robot arm and a segment constituting the obstacle at each node was made and if the intersection takes

29、 place, this node is treated as the obstacle in the C-Space.IV.NUMERICAL SIMULATIONSBased on the above approach the path planning for capturing a target satellite was examined using a space robot model. In this paper we assume the space robot with two dimensional and 2 DOF robotic arm as shown in Fi

30、g.1.The length of each link is given as follows:l1 =1.4m, l2 = 2.0m, l3 = 2.0m ,and the target satellite was assumed 1m square. The grasp the geometrical relation between the space robot and the target satellite. When we consider the operation after capturing the target, it is desirable for the spac

31、e robot to this paper the end-effecter will reach the target when the manipulability is maximized. In the 3DOF case, not depending on the spacecraft body attitude, the manipulability is measured by. And if we assume the end-effector of the space robot should be vertical to the target, then all of th

32、e joints angles are predetermined as follows:As all the joints angles are determined, the relative position between the spacecraft and the target is also decided uniquely. If the spacecraft is assumed to locate at the origin of the inertial frame (0, 0), the goal is given by (-3.27, -2.00) in the above case. Based on these preparations, we can search the path to the goal by moving the arm in the configuration space.Two simulations for path planning were carried out and the results are shown below.A. 2 DOF RobotIn order to simplify the situation, the attitu