This paper presets the specification and implementation of the control system of the mobile platform Rex. The presented system structure and the description of its functioning result from the application of a formal method of designing such systems. This formalism is based on the concept of an embodied agent. The behaviours of its subsystems are specified in terms of transition functions that compute, out of the variables contained in the internal memory and the input buffers, the values that are inserted into the output buffers and the internal memory. The transition functions are the parameters of elementary actions, which in turn are used in behaviour patterns which are the building blocks of the subsystems of the designed control system. Rex is a skid steering platform, with four independently actuated wheels. It is represented by a single agent that implements the locomotion functionality. The agent consists of a control subsystem, a virtual effector and a virtual receptor. Each of those subsystems is discussed in details. Both the data structures and the transition functions defining their behaviours are described. The locomotion agent is a part of the control system of the autonomous exploration and rescue robot developed within the RobREx project.
 K. Sacha, Software Engineering, PWN, Warszawa, 2010, (in Polish).
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