A New Excitation Technique for MIMO FRF Estimation using Multiple, Pneumatic, Random Impact Inputs

As an alternative to traditional shaker and impact excitation, a new excitation technique using single acting pneumatic cylinders is being investigated. In this technique, the structure is excited at multiple locations by successive impacts from the piston of pneumatic cylinders. Solenoid valves regulate air flow through the cylinders, thus controlling the timing and duration of impacts. An electrical circuit consisting of a transistor switch is used to actuate the solenoid valves. A system of independent, random duration and interval pulses (digital time series) is sent to each exciter system to be able to estimate multiple input frequency response functions (FRFs). Since, the random pulse sequences sent to each exciter system are uncorrelated, and the exciters and structure are not connected, it will be always possible to uncouple the forces involved. In order to validate this method, tests are conducted on a rectangular steel plate and trimmed truck body and the FRFs are compared with those obtained from traditional excitation methods.