In this article we develop a new approach to control an omnidirectional mobile manipulator. The robot is considered as an individual agent aimed to perform robotic tasks described in terms of displacement and force interaction with the environment. A reactive architecture and impedance control are used to ensure reliable task execution in response to environment stimuli. The mechanical structure of our holonomic mobile manipulator is built from two joint manipulator mounted on an holonomic vehicle. The vehicle is equipped using three motorized axles with two spherical orthogonal wheels. The dynamics of the mobile manipulator robot is defined tacking into account the dynamical interaction between the base and the manipulator. Then we design a nonlinear controller for the robot using input-state linearization method. The control structure of the robot is built in order to demonstrate the main capabilities in navigation and obstacle avoidance. Several simulations were conducted to prove the effectiveness of our concept.