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Helmut Hoyer

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4 papers

1 author row

IROS Conference 1995 Conference Paper

Fuzzy collision avoidance for industrial robots

Michael Gerke 0001
Helmut Hoyer

An advanced concept to solve the collision avoidance problem in multi-robot workcells is presented which holds realtime conditions for industrial robot controllers. The approach is based on a fuzzy set description of critical configurations between robots in a common workspace. The authors' strategy assumes a careful offline path planning to unburden the algorithm from online path planning but to handle extraordinary events, which can not be treated offline. Though the authors' collision avoidance strategy is local, in general it switches towards the preplanned trajectory with decreasing degree of conflict and finally reaches planned goal positions. To handle the collision avoidance problem in realtime, the complex kinematic chain of any industrial robot with six degrees of freedom is replaced by a drastically reduced actual robot (RAR). Fuzzification of the actual RAR position in a workspace provides a fuzzy membership vector to sectors, which subdivide the robots' cylindrical workspace. A practical fuzzy-rulebase is given to evaluate the degree of conflict between the actual fuzzy membership vectors of two RARs and to propose secure fuzzy-membership vectors. Defuzzification gives crisp locations of a collision-free trajectory which are restricted by the preplanned trajectory locations if the conflict is small. The efficiency of this strategy is illustrated by an example with two PUMA 562 robots in decoupled motion.

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ICRA Conference 1994 Conference Paper

Online Collision Avoidance for Industrial Robots with Six Degrees of Freedom

Helmut Hoyer
Michael Gerke 0001
Ulrich Borgolte

An online collision avoidance strategy is presented for two industrial robots sharing a common workspace. The algorithm can be computed very fast to provide secure trajectories within the cycle time of industrial robot controllers. Substitution of the complex kinematics of any industrial robot with six degrees of freedom by the more convenient kinematics of the reduced actual robot (RAR) and computation of a virtual hinderance robot (VHR), which describes the most dangerous joint angle position of the RAR with regard to another RAR in the workcell leads to a degree of danger in each component of the RAR's cylindrical frame and results in the evaluation of a secure trajectory. An online decision is made between each component of the preplanned trajectory and the corresponding component of the secure trajectory. The collision-free trajectory is transformed back to the 6D-workspace of the industrial robot. The efficiency of the authors' strategy is illustrated in an example with two PUMA 562 robots. >

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IROS Conference 1993 Conference Paper

Online collision avoidance for two robots in 3D-space

Ulrich Borgolte
Helmut Hoyer
Friedhelm Wrosch

Previously presented methods for online collision avoidance for robots in a two-dimensional space are extended to the third dimension. Even if global planning and programming are done in multi-robot workcells, in real-world applications it is important to supervise the actual movements and to influence them if necessary, due to sensor-driven changes of the trajectories, incomplete information on the environment, and possible failures in mechanical or electrical devices. Therefore, precautions have to be taken for online collision detection and avoidance. Besides the considerations of dynamics for online collision avoidance in 3-D space, attention is given to the online computing of the algorithms and their execution on parallel hardware.

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ICRA Conference 1986 Conference Paper

Pathfinding in multi-robot systems: Solution and applications

Eckhard Freund
Helmut Hoyer

In the paper a general approach is given to the solution of the findpath problem in multi-robot systems based on a suitable structuring of the hierarchical overall system. The method developed uses a systematic design procedure for multi-robot systems which includes the design of the hierarchical coordinator for on-line collision avoidance. The efficiency of this new approach is demonstrated by several cases like the interaction of three stationary robots with different obstacles as well as by the interaction of mobile robots and moving obstacles.

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