Robust adaptive control of Sawyer motors without current measurements

P. Krishnamurthy, F. Khorrami

Research output: Contribution to journalArticlepeer-review


We address nonlinear robust adaptive dynamic output feedback of voltage-fed dual-axis linear stepper (Sawyer) motors using a detailed motor model with electrical dynamics and significant uncertainties and disturbances. A coordinate transformation is proposed to decouple the model into three third-order subsystems along with an appended fifth-order subsystem. The controller utilizes only position and velocity measurements in each axis and achieves practical stabilization of position tracking errors. Adaptations are utilized so as not to require any knowledge of electromechanical system parameters. The controller is robust to load torques, friction, cogging forces, and other disturbances satisfying certain bounds. The controller corrects for the yaw rotation to achieve synchrony of motor and platen teeth.

Original languageEnglish (US)
Pages (from-to)689-696
Number of pages8
JournalIEEE/ASME Transactions on Mechatronics
Issue number4
StatePublished - Dec 2004


  • Adaptive control
  • Position control
  • Robustness
  • Sawyer motor
  • Sensorless control

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Computer Science Applications
  • Electrical and Electronic Engineering


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