Integrated Motion Measurement for Flexible Structures

Abstract

Integrated navigation, as an example of integrated motion measurement systems, is typically based on inertial sensors (accelerometers, gyros) and GPS and is commonly used for vehicle guidance. Traditionally, the vehicle of integrated navigation systems is assumed to be a rigid body. However, extending these integrated systems to elastic structures is possible. The considered continuum, in particular a flexible beam, is an attempt to obtain motion measurements of an aerofoil of a flying aircraft with large structural dimensions. Integrated systems considered here in general are fusing different measuring methods by using their benefits and blinding out their disadvantages. For instance, gyros and accelerometers are used to obtain reliable signals with a good time resolution. On the other hand, aiding sensors like radar units and strain gauges are known to be long-term accurate. The kernel of the integrated systems presented in this article consists, however, of an continuous-discrete extended Kalman filter estimating the motion state of the structure. Besides the sensor signals to be amalgamated, the filter requires a kinematical model of the vehicle motion considered, which has to be developed individually. This kinematical model describes the standardised dynamics of the vehicle by means of specific forces, i.e. accelerations, and of rotational velocities. Thus, there are no dynamometers or mass and stiffness properties needed in this approach. Diverse kinematical models of the beam were developed and evaluated, using model reduction in regard of the naturalmodes. Based on simulation the paper shows this approach, appropriate sensor sets, and estimated motion results of a flexible beam.