Real-time continuous collision detection for mobile manipulators - A general approach

Abstract

Abstract-We present a general real-time continuous collision detection algorithm for arbitrary systems of moving bodies connected to each other in a kinematic tree of joints. Here "joint" as a general term refers to the measured relative motion between two bodies, which may be physically connected or not. We provide a basic set of joints covering revolute and prismatic joints, vehicle motion, and 3d positioning which is sufficient for many applications in particular those involved with mobile manipulators, e.g. industrial and humanoid robots, intelligent transportation systems, or equipment at construction sites. Each joint implementation either operates on a motion bound (an interval covering the braking distance) or an uncertainty bound (measurement error) and computes a volume that spatially bounds the effect of that motion or uncertainty. Aggregating all joints in a kinematic tree then yields a conservative continuous collision detection for the complex and uncertain motion of the whole system.We further present an augmented reality visualization that overlays the collision volumes into the live image of a camera, which can be used to validate the collision model before bringing a system into service.

A computationally efficient safety assessment for collaborative robotics applications

“…It is also worth pointing out that, in potential field-based collision avoidance methods, obstacle geometric modeling is required. To this end, collision models like bounding volumes [4,5] or swept volumes [16,17,19] can be adopted. In our approach instead, there is no need to introduce a virtual representation of the object source of danger, since its triangular mesh can be directly exploited.…”

“…Alternative approaches include on-line re-planning [15] and realtime collision avoidance methods based on collision models. In [16,17], Täubig et al present a collision prediction approach that exploits the GJK-algorithm [18] to compute the distance between robot swept volumes. Corrales et al [19] developed a safety strategy in a real human-robot interaction task, relying on a geometric representation for human operators and robotic manipulators made of a set of bounding volumes based on swept-sphere line primitives.…”

Trajectory generation algorithm for safe human-robot collaboration based on multiple depth sensor measurements

“…where x˙and y˙are defined according to (17), while α left and α right are the joint angles vectors for the left and right arm, respectively. Once we determine, for each DOF, the T s -reachable set lower and upper bounds…”

“…Finally, in order to account for lateral walking, it is possible to extend model (17) according to [38]:…”

“…On the other hand, several collision detection (see [12]) and reaction strategies have also been proposed, like for instance [13,14]. In particular [15] discusses a comparison between different collision reaction strategies aiming at ensuring human safety in physical-HRC scenarios, while [16] and [17] introduce real-time self collision detection algorithms for both humanoid and industrial robots, based on the concept of "swept volumes". The most relevant safety standards published in the last few years [18,19] introduced "speed and separation monitoring" criteria, according to which a minimum separation distance (depending on Tool Center Point velocity and/or payload) must be kept between an industrial manipulator and a human worker.…”