No abstract

The electromagnetic shakers (also known as voice coil actuators) are commonly utilized for computer controlled force applications. When the force trace becomes harmonic, however, the devices which use rotating eccentric masses are more feasible to operate. If, on the other hand, one wishes to vary three descriptors, the amplitude, frequency and the phase angle of these harmonics the design and the operation of the structure become more challenging. A novel design and control are presented in this paper to achieve this objective with a very favorable ratio between the peak force and the weight. The variation in the force amplitude is taken from zero to Fmax, while the frequency range varies about ±10% around the nominal operating frequency. Indefinite variations of relative phase angle (i.e., zero to 2π) with respect to a given harmonic signal can be achieved using this new device. The transition from a set of the tree descriptors to another set is achieved under an open loop control of the device. On a prototype experimental setting we demonstrate a successful deployment of the control. Such a structure can be used in some cases for generating desired harmonic force excitations, and in some mission critical application, for canceling vibration caused by quasi static harmonic forcing.