Modular robotic systems with no fixed mechanical contacts have the ability to adopt and reconfigure very rapidly, but are very difficult to control dynamically. Moving module solely with electromagnetic or-static forces can lead to unwanted slipping or even loss of contact. This paper presents a strategy to design controller for such modules based on the limits derived by combining the contact constraints and the actuator saturation. We demonstrate the design of a simple but effective controller for two module motions. We also present guidelines for the design of the modules based on the controller limitations.