This paper presents a Center of Mass (CoM) based manipulation and regrasp planner that implements stability constraints to preserve the robot balance. The planner provides a graph of IK-feasible, collision-free and stable motion sequences, constructed using an energy based motion planning algorithm. It assures that the assembly motions are stable and prevent the robot from falling while performing dexterous tasks in different situations. Furthermore, the constraints are also used to perform an RRT-inspired task-related stability estimation in several simulations. The estimation can be used to select between single-arm and dual-arm regrasping configurations to achieve more stability and robustness for a given manipulation task. To validate the planner and the task-related stability estimations, several tests are performed in simulations and real-world experiments involving the HRP5P humanoid robot, the 5th generation of the HRP robot family. The experiment results suggest that the planner and the task-related stability estimation provide robust behavior for the humanoid robot while performing regrasp tasks.
The stability of a given state is computed using the CoM of the robot-object system and the robot support polygon, this provides a means to measure how stable the robot-object system is. By determining the CoM of the system and its projection over the robot support polygon plane, we can determine if the robot is stable @cite_16 . For this work, it is assumed that the robot is standing on an even and flat surface while performing regrasp tasks. This enables the planner to evaluate the states of the robot without extra sensors and complicated calculations.
@cite_16
2005805981
Abstract While the total number of theoretically possible quadruped gaits is quite large, only six gaits have the property that they can be executed while keeping at least three feet on the ground at all times. These gaits, called creeping gaits, seem to be well suited for low-speed locomotion since they permit a quadruped to remain statically stable during most of a locomotion cycle. A mathematical analysis shows, however, that for only three of the six creeping gaits it is possible to place the feet of an animal or machine so that it is statically stable at all times. Furthermore, among these three, there exists a unique optimum gait that maximizes static stability. This gait corresponds to the normal quadruped crawl favored by most animals for very low-speed locomotion.