Abstract
We verified through experimentation on five carts connected in series by four springs that a control method for always efficiently exciting a multi-degree-of-freedom system at a resonance frequency. When an excitation point corresponds to a vibration detection point in a multi-degree-of-freedom system, a phase lag at a given resonance frequency and the phase lead at an anti-resonance frequency alternately appears in the vibration characteristics, and the phase lag is 90° at all resonance frequencies. Therefore, if a controller with a 90° phase lag and a constant gain in a wide frequency range is used, self-excited vibration is generated at all resonance frequencies. The local feedback controller for each actuator consists of a self-excited vibration controller that is the sum of the integral control of the displacement and the positive velocity feedback control, a saturation element that limits excitation force, and a negative velocity feedback controller that provides active damping. We used a four-degree-of-freedom system consisting of five carts and four springs in our experiment. Four voice coil motors controlled by the local feedback were used to generate self-excited vibration at all the resonance frequencies of a four-degree-of-freedom system. The self-excited vibration mode can be freely switched on by changing the frequency of the sine wave that is added as an electric disturbance. A system using many actuators with local feedback control, i.e., decentralized control, driven at a resonance point with a natural frequency is excellent in its adaptability to the environment, in its extendibility, and in its fault tolerance.
