Analysis of influence of drive system configurations of a four wheelled robot on its mobility

The work covers analysis of mobility of a four-wheeled robot based on its dynamics model. Several configura- tions of robot's drive system are considered: one driven axle, two independently driven axles and drive trans- mission from one axle to another by means of a toothed belt. The analysis of robot's mobility is limited to cases of its motion with constant velocity on the ground with various inclinations and mechanical characteristics. It is assumed that robot's wheels roll without sliding. In the conducted investigations of robot's mobility, limitations resulting from wheels' interaction with the ground are taken into account. Based on results of the investigations, advantages and drawbacks of each of drive system con- figurations of the robot are discussed. carried out for two principal purposes, that is, for the pur- pose of: designing and testing of robot's mechanical structure, synthesis of robot's control system. At the stage of mechanical design, the mobility analysis based on robot's dynamics model allows testing of fulfil- ment of the imposed requirements and design optimiza- tion. The analysis can be repeated on the robot's physical prototype in order to verify results of the analysis carried out using the robot's virtual model. An important assumption associated with the analysis of robot mobility is whether sliding of robot's wheels is taken into account. The problem of modelling of motion of mobile robots including wheel slip was discussed, for instance, in (6). From previous research it follows that the longitudinal slip of wheels should be taken into account mainly in case of significant accelerations and sometimes also in case of transition from one type of ground's mate- rial into another (e.g., from concrete onto ice). On the oth- er hand, side slip of wheels should be considered during negotiation of a curved path always if the robot is of the skid-steered type. Side slips tend to increase with increas- ing robot's velocity of motion and with decreasing radius of curvature of the path. In the present work, mobility of a four-wheeled robot is analysed for different configurations of the drive sys- tem and including constraints which follow from robot's dynamics and type of terrain on which the motion takes place. Aim of the analysis is discussion of advantages and disadvantages of different configurations of the ro- bot's drive system. The analysis is limited to the case of translational motion of the robot's body with constant velocity. For this reason, the occurrence of wheel slip is neglected.