Remote control structural exciters for structural data acquisition system calibrations

The Air Force invented a new calibration technique, which allows one person to perform multiple end-to-end mechanical calibrations of structural dynamics measurement systems. An end-to-end calibration means a full calibration of instrumentation from the physical input to the transducer to the output where the analog or digital signal is normally analyzed. It is difficult to stimulate mounted and embedded transducers with known physical inputs. Normally two people calibrate-one at the transducer holds or attaches the exciter and one operates the recorder. This new technique uses remote control structural exciters to stimulate measurement transducers contained in structures, with a measurable input level, and the output signal is communicated to a data recorder. The Air Force demonstrated this patented technique by using accelerometers in the laboratory. A commercial off-the-shelf vibration paging system sends a signal from a master control unit to individual exciters that stimulate accelerometers mounted on structures. A reference accelerometer measures the input. Engineers validated the technique using eight different exciters in a completely randomized block design experiment consisting of three 2-level factors: material, structural thickness and excitation mode. The engineers measured amplitude, frequency and transfer function between the accelerometers. This paper describes the invention and looks at potential field applications to insure data integrity in structural data acquisition systems on aging commercial and military vehicles.