Kinematics and dynamics of a hybrid serial-parallel mobile robot

In this study, kinematics design, dynamics modeling and verification of a compounded serial-parallel wheeled mobile robot is elaborated. The proposed novel kinematic structure is best suited to fulfill stable motion of the robotic system when handling heavy objects by manipulators mounted on mobile platforms. 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. The suggested structure adopts the advantages of both serial and parallel robots, to move the base point of the serial robot with respect to the mobile platform to fulfill the system stability after grasping heavy objects. In order to investigate the comprehensive kinematics model of the robot, after introducing its novel structure it is divided into three modules, i.e. a mobile platform, a parallel ST mechanism, and a serial robot. 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. Then, to verify the obtained mathematical model, several benchmark actuating inputs are applied to the model and the system responses are analyzed.