A multi-frequency MIMO control method for the 6DOF micro-vibration exciting system

A multiple-input multiple-output (MIMO) control method for a micro-vibration exciting system is proposed in this paper. The controlled system is designed as Hexapod configuration to provide six-degree-of freedom (6DOF) micro-vibration excitation under the power input through 6 leg actuators. Aiming at the typical MIMO problem, a decoupling approach is introduced by using the frequency response matrix and its inverse, which can transfer the coupled MIMO system into 6 independent single-input single-output (SISO) systems in wide frequency band. For each of the decoupled SISO system, the adaptive disturbance cancellation (ADC) method with the least mean square algorithm is used to control the sinusoidal excitation output in time domain. Furthermore, the decoupling approach and ADC method are extended to meet the requirement on simultaneous multi-frequency excitations. Experiments show that high control precision can be reached in the frequency band of 300 Hz with the micro-vibration exciting system. And finally the excitation outputs including the multiple frequencies in same degree of freedom (DOF) and different frequencies in different DOFs are realized by the system.