This paper presents the theoretical formulation of generic frequency r
esponse functions (FRFs) for continuous systems associated with variou
s forms of actuation and sensing methods. The generic actuator and sen
sor eigenfunctions are identified and interpreted physically. The FRF
can then be expressed in a conventional modal format. The testing proc
edure by roving the sensor with the fixed actuator results :in the sen
sor eigenfunction after the extraction of modal parameters. In contras
t, roving :he actuator with the fixed sensor results in the actuator e
igenfunction. The physical meanings of the extracted mode shapes are s
hown to be characterised by the form of the actuators and sensors. The
lateral vibration of a one-dimensional beam problem is illustrated to
demonstrate the applications of various forms of actuators and sensor
s to structural modal testing. Three types of actuators and three type
s of sensors are considered, and the feasibility of structural testing
for applying any combination of the actuators and sensors is shown. T
his work provides the theoretical base for applying various forms of a
ctuators and sensors to structural modal testing. (C) 1998 Academic Pr
ess.