This paper presents design and control architecture of a small mobile robot with hybrid locomotion system. It consist the combination of wheel and track type motion system resulting as a hybrid mechanism. The wheel locomotion system helps the robot to move on flat surface or path platform with high velocity, high manoeuvrability at low energy consumption. The track system is designed for rough and unstructured path, where robot need to cross irregular surface with high stability. This system works on interchangeable locomotion phenomena by means of track tensioner unit (TTU). The TTU helps the loading and unloading of track system by means of rack and pinion mechanism. This design of small hybrid mobile robot is improves robot applications and also enhance its flexibilty, verstality to work in multi type of terrains.