Multi–Input Multi–Output Hybrid Active Vibration Control for High Frequency Random Vibration

Electromagnetic shakers and closed loop control systems are commonly used in qualification tests for environmental vibration conditions. However, shakers have resonances and anti-resonances at high frequencies. Resonances can be beneficial in that the shaker needs to exert less force to achieve the desired environment, but they can make it more challenging for the control system to match the desired environment. Anti-resonances are more problematic because they represent frequencies where the voltage input to the shaker causes little motion (at some locations on the slip table or adapter plate). Hence, these can cause the system to require driver voltage levels above the controller capacity and cause the test to abort and could even cause damage to the shaker. This paper proposes and characterizes a hybrid shaker system that uses piezoelectric actuator(s) in addition to the electromagnetic shaker to create a MIMO control system. It is hoped that the additional control effort introduced by the piezoelectric actuator can eliminate anti-resonances, expanding the frequency range over which the desired environment can be achieved. Furthermore, the actuators have very different capabilities as a function of frequency, and this is found to significantly reduce the control effort needed by the primary electromagnetic shaker.