Project Title:

Multi-Degree-of-Freedom Reaction Force Sensors Simplify theDetermination of Aircraft Weight, Balance and Inertia Properties

94-1		03.06	0001

Multi-Degree-of-Freedom Reaction Force Sensors Simplify the
Determination of Aircraft Weight, Balance and Inertia Properties

Abstract:

Accurate, six degree-of-freedom (DOF) measurement from new reaction 
force sensors will allow for precise estimation of a flight 
vehicle's rigid body properties (RBP's): mass, center of gravity 
and inertial properties. By exciting one setup of an aircraft and 
measuring all the forces involved, as well as the resulting rigid 
body motions, the RBP's can be estimated from a single measured 
data set using Newton's first and second law. 
The key to determining the RBP's through this simplified method is 
the accurate determination of each force or moment DOF. The 
summation of the reaction forces can already be measured by wiring 
different cuts of piezoelectric crystals in series to produce a 
single output signal. Recent advances in array calibration indicate 
that this force sensor can be completely calibrated for it's six 
sensitivities by attaching an instrumented mass of known RBP's. 
Technical issues relating to selection of crystal cuts, physical 
configuration, calibration fixturing and calibration methodology 
will be examined. Application of the new sensor for RBP 
determination will also be developed. Applications for a six DOF 
force sensor include simplification of aircraft, automotive and 
component RBP measurement, more accurate force 
measurement for modal analysis and machine tool cutting force 
dynamics. 

The ability to accurately measure force in all six DOF 
immediately benefits the scientific community by reducing 
measurement error introduced through previously unmeasured 
DOF's. More accurate models, and modifications resulting in 
better structural performance will result. Specific 
applications for rigid body properties are widespread and 
extended from aerospace to automotive including component 
modeling and dynamic analysis. 

Key Words

PCB Piezotronics, Inc.
3425 Walden Avenue
Depew, NY  14043-2495