An analysis of the effects of closed-loop commutation delay on stepper motor control and application to parameter estimation

Prashanth Krishnamurthy, Farshad Khorrami

Research output: Contribution to journalArticle

Abstract

The purpose of this brief is to call attention to a phenomenon that is observed when a closed-loop commutation delay is present in stepper motor control applications especially involving high-speed precision motors, e.g., precision assembly, wafer probing, coordinate measuring machines. Commutation is a popular technique used to feedback linearize the mechanical dynamics of a stepper motor by generating phase currents based on the sine and cosine of the relative position within a toothpitch. In the presence of a time delay in the closed loop, the feedback linearization is not exact and a residual term depending on incremental position remains in the closed-loop dynamics. In this brief, we show that a time delay in the closed loop results in two dynamical phenomena, viz., introduction of multiple solution trajectories with sensitive dependence on initial conditions (possibly yielding steady-state velocities with opposite signs) and saturation of velocity. We also show that these phenomena can be exploited to estimate parameters such as closed-loop delay, sensor offset, and toothpitch of the motor.

Original languageEnglish (US)
Pages (from-to)70-77
Number of pages8
JournalIEEE Transactions on Control Systems Technology
Volume16
Issue number1
DOIs
StatePublished - Jan 2008

Keywords

  • Delay effects
  • Motion control
  • Motor commutation
  • Parameter estimation
  • Stepper motors

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Electrical and Electronic Engineering

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