S.A.A. Moosavian and A. Pourreza


Wheeled mobile robot, parallel manipulators, dynamics modelling,control–object manipulation


In this study, dynamics and control of a compounded serial-parallel wheeled mobile robot is elaborated. The proposed system is made of a differentially-driven wheeled platform, a planar parallel manipulator, which is called here as star-triangle (ST) mechanism, and a serial Puma-type manipulator arm attached to the moving star-plane of the parallel manipulator. The suggested structure adopts the advantages of both serial and parallel robots, which will guarantee stable manoeuvres for heavy object manipulation by a mobile robotic system. To develop a comprehensive kinematics model of the robot; it is divided into three modules: i.e., a mobile platform, a parallel ST mechanism, and a serial manipulator. Next, a closed-form dynamics model is derived for the whole hybrid system based on a combined Newton-Euler and Lagrange formulation. The proposed method presents the mutual dynamic interaction wrenches between the integrated platform and the serial manipulator which can be exploited for the tip-over stability analysis of the mobile robotic system. Finally, the multiple impedance control (MIC) law is adopted to control the overall system in either free of contact missions or interactive tasks. The MIC law as a model-based algorithm enforces a desired impedance law on the platform, ST parallel mechanism, and the serial manipulator itself. Obtained results reveal a good tracking performance of the system, i.e., a smooth motion of the manipulator and the moving base, even in the presence of impacts due to contact with an obstacle.

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