Self-tuning integral force feedback

A self-tuning procedure is proposed for an active structural element with collocated sensing and actuation (a so-called ‘Smart Disc’). The procedure aims at optimal active damping by means of Integral Force Feedback control. In case the behavior of the structure to be damped may be described by a single dominant vibration mode, self-tuning is realized in two fairly simple steps: (1) recursive estimation of three system parameters and (2) determination of the optimal controller parameters. However, if the assumption concerning a single dominant vibration mode does not hold, both steps in the selftuning procedure may easily fail

Optimal integral force feedback and structured PI tracking control : application for objective lens positioner

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Active damping of rotating platforms using integral force feedback

peer reviewedThis paper investigates the use of Integral Force Feedback (IFF) for the active damping of rotating mechanical systems. Guaranteed stability, typical benefit of IFF, is lost as soon as the system is rotating due to gyroscopic effects. To overcome this issue, two modifications of the classical IFF control scheme are proposed. The first consists of slightly modifying the control law while the second consists of adding springs in parallel with the force sensors. Conditions for stability and optimal parameters are derived. The results reveal that, despite their different implementations, both modified IFF control scheme have almost identical damping authority on the suspension modes

Active Damping of Rotating Platforms using Integral Force Feedback

This paper investigates the use of Integral Force Feedback (IFF) for the active damping of rotating mechanical systems. Guaranteed stability, typical benefit of IFF, is lost as soon as the system is rotating due to gyroscopic effects. To overcome this issue, two modifications of the classical IFF control scheme are proposed. The first consists of slightly modifying the control law while the second consists of adding springs in parallel with the force sensors. Conditions for stability and optimal parameters are derived. The results reveal that, despite their different implementations, both modified IFF control scheme have almost identical damping authority on suspension modes

Prediction and improvement of the maximum achievable damping with collocated control

Active damping can be realised robustly through the use of a position actuator, a collocated force sensor, and control based on ‘Integral Force Feedback’ (IFF). Instead of a pure integrator, it is also possible to use a first-order lowpass-filter in the feedback loop (‘leaking IFF’). For both cases, the maximum achievable relative damping for a certain vibration mode can easily be predicted. If the achievable damping is too low, it is possible to improve this by means of ‘crosstalk-compensation’. A close look at these strategies reveals that there is a one-to-one relation between ‘leaking IFF’ and ‘crosstalk-compensation’. The presented theory is verified by means of active damping experiments within the lens support of a wafer stepper

Comparative Study of Different Active Control Systems of High Rise Buildings under Seismic Excitation

Large number of active vibration control systems existing in the literature has brought lot of confusion for engineers and junior researchers. This study deals with the comparison of different active control systems of a 20-storey building under seismic excitation for three control devices: Active Mass Damper (AMD), Active Bracing System (ABS) and Connected Building Control (CBC). Two different control configurations are considered to add active damping to the building. The first one employs force actuator and displacement sensor and is examined with first and second order Positive Position Feedback, Lead compensators and Direct Velocity Feedback. The second configuration employs a displacement actuator collocated with a force sensor and an Integral Force Feedback control law. A total number of 15 control cases are compared from the point of view of stability, robustness, performance and control effort

Smart Disc - Application in an ASML wafer stepper

High-precision machines typically suffer from small, but annoying, badly damped vibrations. In case such a vibration problem can not be solved passively, a solution may be found in active vibration control. In this respect, research at the Drebbel Institute is aimed at the development of a device called SMART DISC (SD). It is envisioned as an active structural element, consisting of a piezoelectric position actuator co-located with a piezoelectric force sensor, and control and amplifier electronics. As an industrial, three-dimensional test set-up for evaluation of the performance of SD’s, the lens support of an ASML wafer stepper has been chosen. By inserting SD’s in the lens support, and applying Integral Force Feedback control, the relative tilt of the lens relative to the main plate has been reduced by more than a factor 3. The absolute acceleration level of the top of the lens at its dominant resonance frequency has been successfully reduced to less than 10% of the original level

Butterworth Pattern-based Simultaneous Damping and Tracking Controller Designs for Nanopositioning Systems

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