The "timed elastic band" approach optimizes robot trajectories by subsequent modification of an initial trajectory generated by a global planner. The objectives considered in the trajectory optimization include but are not limited to the overall path length, trajectory execution time, separation from obstacles, passing through intermediate way points and compliance with the robots dynamic, kinematic and geometric constraints. "Timed elastic bands" explicitly consider spatialtemporal aspects of the motion in terms of dynamic constraints such as limited robot velocities and accelerations. The trajectory planning operates in real time such that "timed elastic bands" cope with dynamic obstacles and motion constraints. The "timed elastic band problem" is formulated as a scalarized multi-objective optimization problem. Most objectives are local and relate to only a small subset of parameters as they only depend on a few consecutive robot states. This local structure results in a sparse system matrix, which allows the utilization of fast and efficient optimization techniques such as the open-source framework "g2o" for solving "timed elastic band" problems. The "g2o" sparse system solvers have been successfully applied to VSLAM problems. This contribution describes the application and adaptation of the g2o-framework in the context of trajectory modification with the "timed elastic band". Results from simulations and experiments with a real robot demonstrate that the implementation is robust and computationally efficient.
In the field of service robotics, robots serve and assist human beings. It is natural for humans to directly interact with the robot via tactile intelfaces. This paper introduces several kinds of tactile interactions between a user and the robot as well as interactions of the robot with the environment. All interactions are implemented in a single paradigm: Forces measured from tactile sensors result in motion vectors at the contact points. The motion vectors ffom diperent sensors are superimposed and then determine the robot's joint velocities. We present results from our experimental setup consisting of an 8 degrees of freedom manipulator ann mounted on a mobile platform. In the illustrated example, a human interacts with the robot using only the tactile inte~ace.
Service robots seme and assist human beings sharing a common environment. Therefore fast responding and robust planners generating collision-free motions are required to guarantee a safe and convenient manmachine interaction. I n most cases the working environment is partially known or perceived by a sensor system. To reduce planning time, this work presents a motion planner interacting with reactive plan execution systems. Dividing the work space into subspaces appropnate motion plans are determined. Based on an environment model collisions are avoided by interacting with an obstacle avoidance system. Tactile sensors are used to detect collisions of the robot arm, e.g. due to an incomplete knowledge of the environment or enforced by a human touching the robot. Experimental results of our 8 degree of freedom manipulator arm mounted on a mobile platfonn are presented. I n these eqeriments the robot acts as a barkeeper.
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