Carnegie Mellon University
An Active Z Gravity Compensation System

Greg White and Yangsheng Xu
tech. report CMU-RI-TR-92-09, Robotics Institute, Carnegie Mellon University, July, 1992

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To perform simulations of partial or microgravity environments on earth requires some method of compensation for the earth's gravitational field. This paper discusses an active compensation system that modulates the tension in a counterweight support cable in order to minimize state deviation between the compensated body and the ideal weightless body. The system effectively compensates for inertial effects of the counterweight mass, viscous damping of all pulleys, and static friction in all parts of the GC system using a hybrid PI/fuzzy control algorithm. The dynamic compensation of inertia and viscous damping is performed by PI control, while static friction compensation is performed by the fuzzy system. The system provides very precise gravity compensation force, and is capable of non-constant gravity force compensation in the case that the payload mass is not constant. The only additional hardware requirements needed for the implementation of this system on a passive counterweight balance system are: a strain gauge tension sensor, and a torque motor with encoder. (23 pages)

Grant ID: NAGW-2998
Number of pages: 23

Text Reference
Greg White and Yangsheng Xu, "An Active Z Gravity Compensation System," tech. report CMU-RI-TR-92-09, Robotics Institute, Carnegie Mellon University, July, 1992

BibTeX Reference
   author = "Greg White and Yangsheng Xu",
   title = "An Active Z Gravity Compensation System",
   booktitle = "",
   institution = "Robotics Institute",
   month = "July",
   year = "1992",
   number= "CMU-RI-TR-92-09",
   address= "Pittsburgh, PA",