Gravity-compensation-driven position regulation for robotic systems under input/output delays

Yen Chen Liu, Nikhil Chopra

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


Input/output (I/O) delays in a closed-loop robotic system can significantly deteriorate both its stability and performance. In this paper, we study the position control problem for robotic manipulators under I/O delays, where the delays manifest as a result of communication with a non-collocated controller. Previous research on this topic has assumed the gravitational torque to be pre-compensated in a collocated manner. This paper studies the stability and regulation performance of the closed-loop system when the compensation for the gravitational torque is provided by a non-collocated controller. We demonstrate that simply utilizing scattering transformation for robotic systems under I/O communication delays results in position drift due to gravity compensation. Hence, a new control algorithm incorporating delayed position feedback and scattering variables is studied subsequently. Stability and performance margins dependent on the round-trip delays and the gravitational model are proposed to guarantee stable position regulation. Since the control architecture with scattering transformation does not address the stability problem due to sensing-actuation delays, a new controller is developed to cope with robotic control systems under time-varying sensing-actuation delays. The proposed control algorithms are studied in this paper via experiments on a manipulator with three degrees of freedom.

Original languageEnglish
Article number6579720
Pages (from-to)995-1005
Number of pages11
JournalIEEE Transactions on Control Systems Technology
Issue number3
Publication statusPublished - 2014 May

All Science Journal Classification (ASJC) codes

  • Control and Systems Engineering
  • Electrical and Electronic Engineering

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