High-bandwidth Control Research Articles

High-bandwidth control of the head-positioning mechanism in a Winchester disk drive

Modern disk drives use fast voice coil actuators for the positioning of magnetic heads onto desired tracks and for keeping them on track against various disturbances by closed-loop control. Problems stem from high-desired control bandwidth (∼ 1 kHz) requiring digital signal processing rates above 10 kHz and from complexity due to structural mechanics effects.

Antenna pointing systems for large communications satellites

Most of the geostationary satellites already developed operate antenna pointing through fine orientation measurement and control of the satellite main body to which each antenna is rigidly attached. The main body orientation is measured by means of infrared Earth observation. Increasing antenna size and power and, sometimes, political constraints enhance the benefit of very accurate antenna pointing (0.05 deg, 3 a at antenna electrical axis level). This typically implies direct measurement of antenna orientation through the use of radio-frequency sensors incorporated in each antenna, mechanical decoupling between antennae to allow for compensation of structural deformations, and mechanical decoupling between each antenna and the satellite main body through the use of antenna pointing mechanisms to allow for high antenna control bandwidth. Concepts of antenna pointing mechanism and associated control for such satellites are presented shortly. Pointing performances of attitude control concepts alternatives are shown for a typical payload.

Implementation of Very Fast State-Space Controllers Using Digital Signal Processors

If linear multivariate control is applied to fast systems like servohydraulic or electromechanical mechanisms, the problem of realizing high order high bandwidth controllers arises. Implementation of such controllers on general purpose microprocessors is limited by the lack of arithmetic computing speed. Sampling frequencies about one order of magnitude higher can be realized using modern digital signal processor chips instead. The paper shows how they can be used for control implementation. Hardware features as well as a novel concept of a development system dedicated to multivariable control are discussed