Abstract: The basic procedure of a multi-input multi-output (MIMO) random vibration test is analyzed systematically in the article. A definition of control error under logarithmic coordinates is provided, and a new proportion-integration-differentiation (PID) control strategy is introduced into the control algorithm. The law of the error-dependent arguments for the PID controller is then presented. A two-input two-output random vibration test is performed with a cantilever beam to verify the proposed control method. The experimental results show that the variable argument PID control method not only has the ability to make rapid tradeoff between the control and the reference spectra but it can also reduce effectively the errors between them as well as the control error of the total root mean square of acceleration. Therefore the accuracy of random vibration test control is improved.

Key words: MIMO, environmental testing, vibration control, PID control, variable argument