A Multi-Loop Control Strategy for Enhanced Nanopositioning

Vibration problems are inherent in most precision positioning systems. These systems are lightly damped and highly susceptible to mechanical resonance and nonlinearity, such as hysteresis and creep. Traditional approaches use a combination of damping and tracking controllers to deal with nonlinearity and resonance respectively. The damping controller utilised in this work to damp the mechanical resonance of the nanopositioning platform is the Integral Resonant Controller (IRC). This common approach is based on sole use of the integral controller (I) or proportional integral (PI) as a tracking controller to treat nonlinearity. This paper employs a multi-loop feedback scheme as a second-order integral tracking controller in conjunction with the damping controller (IRC). The proposed multi-loop feedback scheme delivers enhanced tracking performance with better compensation for hysteresis in comparison with singleloop tracking.