Real-Time Self Collision Avoidance for Humanoids by means of Nullspace Criteria and Task Intervals

We describe a new method for real-time collision avoidance for humanoid robots. Instead of explicitly modifying the commands, our method influences the control system by means of a nullspace criteria and a task interval. The nullspace criteria is driven by a virtual force acting on a joint center vector that defines the minimum of a potential function in joint space. The task interval defines the target constraints in task coordinates and allows the avoidance system to specify deviations from the given target position. The advantages of this indirect method are that smooth trajectories can be achieved and the underlying motion control may use any trajectory generation method that is able to satisfy the constraints given by the collision avoidance. It is most useful for highly redundant robots like typical humanoids. The method is able to assure smooth collision free movement on the humanoid robot ASIMO in real time interaction even in cases where the dynamical constraints of legged walking apply