ON THE DYNAMIC TIP-OVER STABILITY OF WHEELED MOBILE MANIPULATORS

Due to excessive maneuverability, mobile manipulators which consist of one or more manipulators mounted on a mobile base have attracted much of interest. Tipping over is one of the most important problems in mobile manipulators especially in manipulating heavy objects, also during maneuvers in unknown environment or on rugged terrains. Therefore, estimation and evaluation of dynamic stability with appropriate easy-computed measure throughout the motion of such systems is a challenging task. In this study, a new tip-over stability measure named as moment--height stability (MHS) measure is presented for wheeled mobile manipulators. The suggested MHS measure can be effectively used for both legged robots and mobile manipulators. The required computational effort of the MHS for a given system is compared to other measures, which reveals the efficiency of the MHS over the others. Finally, various case studies are presented to demonstrate the new MHS measure performance compared to the results of other measures. All calculations for system dynamics modeling have been performed using a symbolic code developed in Maple VI, and the obtained models were transferred to another code in Matlab VII to complete numerical simulations. The obtained results show the merits of the new proposed MHS measure, in terms of prediction of the exact time of instability occurrence, without extra unnecessary precautions which may confine the maneuverability of the system and its operation.