The Force is With You - The Apparent Vertical Filter Concept

Abstract

Supplying aircraft pilots with adequate motion cues in flight simulators is still an important issue. The main problem is the limited space envelope of motion systems that makes an ideal replication of accelerations impossible. As a consequence those translational acceleration signals cannot be provided directly and need to be transformed to angular attitudes or scaled down depending on the time in which they appear. State-of-the-art motion drive algorithms like the classic washout filter algorithm are using sets of high- and low-pass filters in combination with gain factors to achieve such a response. But those control methods do not distinguish between the causes of accelerations with respect to flight maneuvers. The Apparent Vertical Filter developed by the German Aerospace Center provides a different approach to this problem. The current paper gives an overview of how the problem of false motion cues could be adessed within a number of idealized maneuvers. As an example the filter input data of a coordinated turn maneuver will be defined. The constraints of current filter methods using the classic washout filter will be discussed. The paper gives an overview of how the apparent vertical filter deals with the problem and how it is structured. Finally, the responses of both filter methods, the AVF anf the CWA, to aircraft model data are compared.