Dissertation > Industrial Technology > Automation technology,computer technology > Automation technology and equipment > Robotics > Robot > Intelligent robots

Study on Obstacle Avoidance Ability and Motion Planning of 8-dof Wheeled Mobile Manipulator

Author YaoYuFeng
Tutor CaiHeGao;SunLiNing
School Harbin Institute of Technology
Course Mechanical and Electronic Engineering
Keywords wheeled mobile manipulator obstacle avoidance path planning motion planning self-motion manifold
CLC TP242.6
Type PhD thesis
Year 2009
Downloads 171
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Mobile manipulator, a kind of robot system, is composed of mobile platform and manipulator installed on the platform, and can be widely used in elderly and disabled aid, disaster rescue, and explosives disposal, etc. The structural features of 8D-WMM show the characteristics of nonholonomic redundancy, so the problems of its motion planning are more complicated than mobile robot and traditional redundant robot. Furthermore, because 8D-WMM generally works in complicated environments with obstacles, it is meaningful to enhance its operating ability by use of the redundancy in non-structural environment full of obstacles. Nowadays, it is lack of systematic study in framework integration of WMM and inverse kinematics optimization facing obstacle avoidance throughout this field, which can not fully exert the flexible operating ability of this kind of robot in complicated environment. Therefore, this thesis focuses on theoretical exploration on motion planning method of 8D-WMM including kinematics, path planning, obstacle avoidance, and end effector operation. Besides, the 8D-WMM system was built for elderly and disabled aid, and experiments were carried out to testify theories.Because the 8D-WMM includes nonholonomic constraint, it is difficult to obtain analytical solution of self-motion manifold. Therefore, based on the theory of movement equivalence, this thesis carried through study on its kinematics and solved 8D-WMM self-motion manifold by combining geometric distribution characteristics of 8D-WMM joint axes and using the tool such as vector algebra. And it also got Jacobian matrix by using the speed superposition principle through regarding mobile platform as Generalized Kinematic Pair.To easily evaluate the obstacle avoidance capabilities of a redundant robot, this thesis proposed and established obstacle avoidance ability index of redundant robot which has intuitive geometric meaning in virtue of space measurement of pole self-motion trajectory-obstacle avoidance activity, whose solution is obtained through a planar 3-DOF robot, and further analyzes the influence of 8D-WMM framework size on its obstacle avoidance ability by using the index. In the aspect of path planning study, the typical operating environment and obstacle of 8D-WMM were analyzed firstly. Then the avoidable criterion of various obstacles such as flat top, slant, and dome, etc, was given by using the results of 8D-WMM self-motion analysis and combining the characteristics of arms joint configuration and the solution to the mobile manipulator’s obstacle avoidance area was analyzed. Finally, the path planning algorithm of the mobile platform facing obstacle avoidance area and manipulator facing the outline of obstacles were presented.In the study on inverse kinematics optimizing method for obstacle avoidance, from the perspective of self-motion, the thesis puts forward inverse kinematics optimizing method which is more suitable for redundant robot performing obstacle avoidance based on self-motion manifold in virtue of the results of self-motion manifold, which solved the deficiency of the present method in displacement accuracy and calculation quantity. Through the trajectory tracking of a planar 3-DOF robot and the simulation examples of 8D-WMM implementation window, the algorithm feasibility is validated.Finally, by use of the analysis results of obstacle avoidance ability, this thesis built 8D-WMM system experimental platform including the completion of the mechanical body design, the control system hardware, and software design aiming at the task of the elderly and disabled aid. With help of this platform, the thesis completed self-motion manifold experiments, avoidable obstacle direction field experiments, avoidable obstacle direction field algorithm verification experiments, and motion planning algorithm experiments of redundant robots based on self-motion manifold. The experimental results verified the correctness and availability of the theories.

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