Maximum load-carrying capacity of autonomous mobile manipulator in an environment with obstacle considering tip over stability

In order to increase the efficiency of wheeled mobile manipulators (WMM), it is preferred to carry the maximum payload, but in the case of a small-sized platform, which is desirable in applications, it may cause dangerous tip over, especially in the presence of obstacles. So, it is necessary to consider stability constraint in the determination of robot motion planning. This paper presents a novel approach for the determination of the maximum payload-carrying capacity of a coordinated mobile manipulator in an environment with presence of obstacle, based on stability. The proposed method considers the tip over stability on zero moment point criterion, which must be considered when the path of the end-effector is predefined but the position of the mobile platform is free, because tipping over in this condition is probable. Hence, the full dynamic model of WMM (including the coordinating vehicle and manipulator) is used, the obstacle avoidance scheme is implied based on potential functions, and the maximum payload path for a specified payload is generated using the optimal control approach. Then, an iterative method based on the stability criterion and motor restriction, including torque and jerk, was implied to calculate the maximum payload capacity. To the best of our knowledge, this is the first paper reporting on some simulation results as well as successful experiments of implementing the algorithm. The proposed approach has been implemented and tested on a nonholonomic WMM consisting of a differential-drive mobile base and a robotic arm to demonstrate the efficiency and effectiveness of the proposed approach.