Dominik Kern

Resonance Tracking of Continua Using Self-Sensing Actuators

This paper proposes and develops an innovative method to solve the resonance tracking problem for actuator and sensor applications to obtain maximum power transmission or signal selectivity using a modified phase-locked loop (PLL). The tracking of a higher eigenfrequency is very useful in some cases, but it is more challenging than the excitation of the only eigenfrequency of a 1-DoF system. The resonances are identified through employing their characteristic phase difference. The conventional PLL was modified to track a certain phase difference without deviation. The closed loop is a nonlinear control system due to the conversion between harmonic signals and phase signals. However, a model simplification to linear elements allows the goal oriented determination of the controller parameters. The advantages of self-sensing in combination with resonance tracking are attractive for practical applications such as ultrasonic motors and compact force sensors. The conducted experiments approved the effectiveness of the resonant excitation of higher oscillation modes of continua using self-sensing actuators.

Guided Wave Generation and Sensing in an Elastic Beam Using MFC Piezoelectric Elements: Theory and Experiment

This article describes the results of experimental evaluation of capabilities of a pin-force mathematical model for guided wave generation and sensing in elastic beam-like structures using MFC piezoelectric elements. It is found that the model provides an adequate and convenient tool for fast parametric study of wave excitation and propagation at a frequency range of practical interest. The model is tested against both MFC and laser vibrometer-based signal measurements; the upper frequency limits of applicability for both sensing methods are demonstrated.

Control of Compliant Mechanisms with Large Deflections

Very often elastic joints are used in high precision applications. In the case of rotational joints flexure hinges do have some advantages compared to conventional ones. However, the most important disadvantages are the complicated and complex kinematics and kinetics. As consequence, the control of mechanisms comprised of flexure hinges gets more difficult. The strategy pursued here is to reduce flexure hinges to pseudo rigid-body systems that fit into the elaborated framework of multi-body dynamics, in particular pre-control in combination with a feedback controller. The inherent deviations of these reduced models are described as uncertainties. Methods from robust control are used to synthesize controllers for such systems with uncertainty. The procedure is illustrated by examining an example of a single flexure hinge (leaf spring type).