QFT-based robust and precision motion control system for a high speed direct-drive XY table positioning mechanism

In this paper, a new quantitative feedback theory (QFT) based robust and precision control system is proposed for a high speed direct-drive XY-table positioning mechanism in semiconductor wire-bonding applications. The most difficult control problems of the systems, caused by mechanical resonances, are solved by the use of a robust velocity feedback controller in the inner loop of the cascaded control structure. The resulting velocity controller and the outer loop position controller are used in combination with auto-tuning feedforward controller to assure consistent and high tracking performance of the motion system with good stability, robustness, disturbance rejection and sensor noise suppression. Validation and implementation of the motion profile with a maximum acceleration of 6.8 g (1g=9.81 m/s/sup 2/) are carried out on tens of mass produced wire-bonding machines in order to confirm the effectiveness of the control strategy.