Dissertation > Industrial Technology > Automation technology,computer technology > Automation technology and equipment > Robotics > Manipulator

Coordinated Motion Planning and Control for Omni-directional Wheeled Mobile Manipulators

Author DuBin
Tutor ZhaoJing
School Beijing University of Technology
Course Mechanical Engineering
Keywords omni-directional wheeled mobile manipulator coordinating motionplanning dimension unity double quaternion
Type PhD thesis
Year 2013
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Compared to mobile manipulators, the omni-directional wheeled mobilemanipulator has omni-directional mobility to achieve free operation and better controlof the operating property and precision of manipulators in more narrow and crowdedspace. Consequently, there is very important theoretical value and practicalsignificance to study the planning and control problems of this kind of systems. Theprincipal research contents are as follows:(1) The construction of an experimental platform for omni-directional wheeledmobile manipulator. Develop a mobile platform on the analytical basis of thecharacteristics of omni-directional wheeled mobile manipulator and useomni-directional wheel as the driving wheel. We design the rotating and steeringmechanism of the wheel. Select the driving motor on the analysis of motioncharacteristics and load. Build motion model according to the specific parameter ofthe omni-directional wheeled mobile manipulator. Use Pmac multi-axis motioncontroller to take control of movement of the omni-directional wheeled mobilemanipulator. Adopt Plus location system based on ultra wideband to locate and guidethe movement of the omni-directional wheeled mobile manipulator.(2) Study on the dimension unity of robot Jacobian matrix. The dimensiondifference of Jacobian matrix coursed by various freedom types of subsystem needs tobe considered in the kinematic performance evaluation of omni-directional wheeledmobile manipulator. In view of the fact that the dexterity evaluation on robots cannotbe made due to the dimensional inhomogeneity of Jacobian, a new approach toformulate the dimensional homogeneous Jacobian and kinematic dexterity measurefor the robot with mixed joints is proposed. According to the double quaternion, therotation and translation in three-dimensional Euclidean spaces converts to the purerotation in four-dimensional Euclidean spaces. The universal transformationalexpression of the link coordinate system is derived based on double quaternion. Thenthe kinematics model of the robot is developed and the non-dimensional Jacobian isobtained by this approach.(3) Study on the optimal motion of the subsystem. A mobile manipulatortypically consists of a mobile platform and a robotic manipulator mounted on the platform. The base placement of the platform has a great influence on whether themanipulator can perform a given task. In the current study of base placement ofmobile manipulators, most only evaluate the candidate base placement in the feasiblearea of base (FAB), regardless of the quality of the implementing task. Firstly, theworkspace of a redundant manipulator is investigated. The manipulation capability ofthe redundant manipulator is maximized based on the manipulability index throughthe joint self-motion of the redundant manipulator. Next, the relative manipulabilityindex (RMI) is defined for analyzing manipulation capability of the manipulator in itsworkspace, and the global manipulability map (GMM) is presented based on theabove measure. Moreover, the feasible area for the installation of the manipulatorbase is analysed. Indices are defined dependent on the joint movements to evaluatethe kinematic performance of manipulators. RRT and RRT*algorithm is analyzedbriefly while indices mentioned in the last section are regarded as the cost function ofthe latter. Finally we study the optimization method of manipulator base placementproposed in this dissertation by means of simulation research based on severalkinematic performance criteria. At last, conclusions are obtained through the analysisof the simulation results.(4) Study on the overall coordinated motion of omni-directional wheeled mobilemanipulator. The unified analysis of omni-directional wheeled mobile manipulator(OWMM) through the dimensionally nonhomogeneous Jacobian matrix may lead tounreliable results. We present a new approach to formulate the dimensionallyhomogeneous Jacobian matrix and a new index for OWMM. The integrated modelingof OWMM is established based on double quaternion, and the non-dimensionalJacobian matrix is obtained from the above matrix. Next, by examining the concept ofdirectional manipulability, we propose a new index to evaluate the directionalmanipulability of OWMM along the specified task direction. Furthermore, thekinematic performance of the fixed base operation of manipulator and the operation ofOWMM are analyzed by numerical simulation. The results suggest that the proposedapproach is equivalent to the method of traditional kinematic modeling, and the newindex is more effective to reflect the variation of the task direction.(5) Experimental study on omni-directional wheeled mobile manipulator. Avirtual and prototype experimental platform of omni-directional wheeled mobilemanipulator has been developed by means of calling interface function of relatedsoftware on the basis of existing hardware platform. This platform has functions including environment modeling, robot motion planning, motion control, location andguidance, which enables the implementation of series motion control experiments ofomni-directional wheeled mobile manipulator. To study experiments of typical trackmovement, motion planning and obstacles avoidance navigation is a way to test thecomprehensive properties of robots. And the experiments of optimal motion planningof subsystem and coordinated motion planning of omni-directional wheeled mobilemanipulator provide evidence of the algorithm effectiveness mentioned.The study above has developed a set of theory and method of global motionmodeling, coordinated planning, motion evaluation, simulation and experiment, tooffer theoretical basis and method support for the structural optimization design andcoordination motion control of omni-directional wheeled mobile manipulator.

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