Robust control of torsional oscillations in high speed servo drive systems using a shaft angle control loop

Abstract

This paper proposes the use of a torsional angle control loop as an effective method to cancel torsional oscillations in two-mass (2M) high speed servo drives. First, an ideal evaluation assuming known the shaft angle and load torque shows the effectiveness of the proposed control. Then, a fullorder observer of the unavailable states is developed. Final evaluations using the full-order observer and including the effect of digital implementation and error in the estimated states, show the robustness of the proposed shaft angle control. NOMENCLATUREinertia K c Converter gain K E BEMF constant K dd Derivative gain of torsional angle loop K rd Feedback gain from torsional angle loop K ri Current loop feedback gain K rv Speed loop feedback gain K sh Shaft stiffness coefficient K T Torque constant R Resonant ratio coefficient t rcv Delay due to speed calculation t ri Delay due to current loop t rc Delay due to compensation scheme t rv Delay due to velocity loop T L Load torque T m Motor torque ω ar Anti-resonant frequency ω m Motor speed ω L Load speed ω r Resonant frequency

Control of a two-mass structure driven by a ball-screw stage

“…Such a system represents a simplified model for many practical systems, such as a disk drive, an electric motor driving a low-stiffness load, or in high-speed maneuvers of mechanical arms and machine tools. Many control techniques were employed to tackle vibrations in a two-mass system, including model predictive control ([1]- [4]), Kalman filters ( [3], [5], [6]), full-order state observers [7], a sliding-mode structure combined with a linear controller [8], notch filters or bi-quad filters ([9]- [11]), and PID controllers [12]. In [13] the two-mass system was formulated in a framework of disturbance rejection control.…”