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Coordinating multiple robots has attracted researchers' interests for many years. However, most of the problems being studied deal with multiple robots acted only within a single group. Coordinated robots are categorized into different groups when the coordination involves robots interchange or heterogeneous motion during the manipulation process. In such a case, coordination between robot groups has to be considered. This is required in certain types of coordinated manipulations such as passing an object, held by multiple robots, between groups of robots or rotating or rolling an object, held by multiple robots, continuously. In the former task, coordinations are made between two isotropic groups of robots whereas in the latter task, coordinations are made between non-isotropic groups of robots. This paper investigates problems related to the control and coordinating of multiple groups of robots. We analyze various kind of tasks of these types and propose a hierarchical control mechanism in achieving these coordinations. Scenarios and limitations for these tasks are presented and discussed. A hybrid force and position control principle is employed in both global and local planning and control. A hierarchical architecture is used to control different levels of the control and planning primitives. The primitives developed for controlling individual robot group can be adopted in this architecture. The primitives in one level offer services only to those in its neighboring levels and hides them from the details of actual service implementations hence reducing the system designing complexity.
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