Sliding mode control of multi-degree-of-freedom structure by means of sensorless active dynamic vibration absorber

The advantages of applying sensorless control to mechanical systems are cost reduction, maintenance of stability of a control system by collocation, noise reduction, decrease of breakdown frequency, increase of reliability, and space saving. In order to realize such a control system, robust performances are required in the state estimation in addition to the control law, so we combined a VSS observer and sliding mode controller and constructed a sensorless nonlinear robust control system. We used a four-degree-of-freedom tower structure with a hybrid dynamic vibration absorber (hybrid DVA) using a linear motor as a control object. It is possible to estimate the state of the system by means of an observer from the coil current of the linear motor for the mutual interaction on the dynamics in the state equation of the system. Then we applied a VSS observer/sliding mode control combination type sensorless nonlinear robust control system to the vibration control system of the structure. Moreover, we investigated performances with regard to vibration suppression.