Motion Planning with Pulley, Rope, and Baskets

  • Authors:
  • Christian E. Eggermont;Gerhard J. Woeginger

  • Affiliations:
  • Department of Mathematics and Computer Science, TU Eindhoven, Eindhoven, Netherlands 5600 MB;Department of Mathematics and Computer Science, TU Eindhoven, Eindhoven, Netherlands 5600 MB

  • Venue:
  • Theory of Computing Systems
  • Year:
  • 2013

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Abstract

We study a motion planning problem where items have to be transported from the top room of a tower to the bottom of the tower, while simultaneously other items have to be transported in the opposite direction. Item sets are moved in two baskets hanging on a rope and pulley. To guarantee stability of the system, the weight difference between the contents of the two baskets must always stay below a given threshold.We prove that it is $\varPi_{2}^{p}$-complete to decide whether some given initial situation of the underlying discrete system can lead to a given goal situation. Furthermore we identify several polynomially solvable special cases of this reachability problem, and we also settle the computational complexity of a number of related questions.