Improving The Static Stability Of A Mobile Manipulator Using Its End Effector In Contact With The Ground

This paper describes the measurement of a stability index in a mobile robot when moving on sloping ground using an arm as an additional support point to avoid tipping when the inclinations of the ground are large enough to produce an unstable situation. The use of additional support point is provided at the arm\´s end-effector which consists of an swivel caster wheel that allows arm rolling contact with the ground while the robot is moving, or changing the arm position. Using the additional contact is defined a "support polygon expanded" whose shape depends on the position of the arm, since the initial articulation (rotational) will be oriented in the same direction having the maximum slope on the instantaneous plane which moves the robot in a given time instant. The second joint\´s arm (screw) maintains contact of the end-effector with the ground, respect to changes of inclination. The models were validated by simulation; it was found that the use of additional support point supplied by the arm in contact with the ground improves the longitudinal stability index of the robot when it moves on ground with different slopes, especially in those configurations where the slope of the ground is predominantly in one direction.