Abstract: A wheel-manipulator robot, as a modular robot system, is characterized by multiple degrees of freedom and relatively complex architecture of the module. Modules of the wheel-manipulator robot can be combined to form various forms of group configuration. Moreover, the group configuration will often be reconfigured to fit into different environment. Conventional methods used to model the dynamics of modular robots will lead to duplicate work, and bring the large amount of data to be updated for reconfiguration. To solve this problem, a modular modeling approach is presented to obtain the general dynamics of group configuration of wheel-manipulator robots, which can eliminate duplicate modeling work. The resulting equations are suited for topologies of serial, closed-form, and tree-form. By using lie algebra as local coordinate, the dynamics of single module is derived, which is free of singularity. Contact sets and joint models are defined based on the relationship and types of connections between modules. Equations of constraint forces are formulated to describe the interactions between modules. Because the state variables of the dynamics equations are not vectors, the geometric numerical integration method is easily implemented. An example is provided to illustrate the validity of the dynamics equations and simulation process.

Key words: dynamics, geometric integration, group configuration, singularity-free, wheel-manipulator robot