This paper proposes a gradient tracking algorithm based on artificial harmonic potential fields, to support the platooning of a team of nonholonomic mobile robots. The main motivation is the need of dynamically changing the goal-point associated with each mobile robot, in order to guarantee the platoon string stability. Mobile obstacles are taken into account with an approach based on the so-called collision cone, and a time-varying artificial security radius is associated with each obstacle, in order to prevent collisions. In addition, the proposed method ensures recovering of the connectivity between robots forming the platoon, after that one of them goes far away from the others and loses the connection during an obstacle avoidance maneuver. Finally, the so-called interference index has been evaluated, to show the low impact of robot motion on human behaviors.