This paper presents the use of a state of the art damper for high-precision motion stages as a sliding plate rheometer for measuring linear viscoelastic properties in the frequency range of 10 Hz-10 kHz. This device is relatively cheap and enables to obtain linear viscoelastic (LVE) fluid models for practical use in precision mechanics applications. This is an example of reversed engineering, i.e., turning a machine part into a material characterization device. Results are shown for a high-viscosity fluid. The first part of this paper describes the damper design that is based on a high-viscosity fluid. This design is flexure-based to minimize parasitic nonlinear forces such as hysteresis and stick-slip. In the second part of the paper, LVE fluid characterization by means of the damper setup is presented. Measurements are performed and model parameters are fitted by a non-convex optimization algorithm in order to obtain the frequency-dependent behavior of the fluid. The resulting fluid model is validated by comparison with a second measurement with a different damper geometry. This paper shows that LVE fluid characterization between 10 Hz and 10 kHz for elastic high-viscosity fluids is possible with a motion stage damper for which the undamped behavior is known.
In motion systems, high controller gains are beneficial in order to suppress disturbances acting on the system. Low-damped non-rigid body (NRB) resonances usually limit this controller gain. The result is a bound on the maximum achievable sensitivity, i.e. the suppression of low frequent position disturbances. Robust Mass Dampers (RMD’s) with a relatively high damping value have shown to be able to increase the NRB damping over a broad frequency range. The main difficulty is to determine the stiffness and damping parameters for these damper mechanisms in order to optimize the closed loop performance of the motion system. This paper proposes a modulus margin based iterative optimization procedure which includes a plant model with dampers added and a PID+ type controller. The results are optimal damper parameters — stiffness and damping — in combination with an as high as possible controller gain, which result in an improved disturbance suppression at frequencies below the bandwidth and a faster setpoint tracking.
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