AUTORESONANT EXCITATION AND CONTROL
OF NONLINEAR VIBRATION MODES
Vladimir Babitsky
An effective use of resonant phenomena in physics and engineering demands an increase in quality of vibrating systems. However, an increase in quality leads to the appearance of control difficulties in monitoring fine resonant tuning. This is because of the strong sensitivity of resonant tuning to parameter and structural deviations. The problem of a fine resonant control is drastically complicated when nonlinear factors, unpredictable variable loads or limited excitation forces produced by the source of energy take place.
An approach has been developed to design resonant vibratory equipment as self-sustaining oscillating systems using electronic and electromechanical positive feedback and a synchronous type actuator for self-excitation of resonant vibration in combination with negative feedback for its stabilisation. This method of control is known as autoresonant [1-2].
The autoresonant control provides the possibility of self-tuning and self-adaptation mechanisms for the system to keep the resonant mode of oscillation under variation of its structure and parameters. The implementations of autoresonant control for the new nonlinear vibratory systems are described. These are a screening machine for vibro-impact transportation and separation of drilling mud [3] and an ultrasonically assisted cutting machine [4-6]. Implementation of autoresonant control allows simple program regulation of intensity of the process in these systems whilst keeping maximum efficiency at all times even for high Q-factor systems. Transient processes keep the resonant efficiency as well.
Dynamics and control strategies of the autoresonant ultrasonic systems were thoroughly investigated and the results of analysis, design and experimentation are presented. The opportunity of application of the robust and high quality nonlinear resonant system under wide deviation of processing loads results in essential increase of productivity, efficiency and improvement of design.