Band-limited Random Signals Research Articles

LQG/LTR based robust youla parameterized adaptive vibration control for the supporting platform of rotating liquid mirror

In mechatronic systems, the vibrations which commonly consist of band-limited random signals mixed with large multiple narrow-band deterministic signals may negatively impact the system performance. For example, due to the incomplete matching of the mechanism and the rotation of the motor, random and deterministic vibration disturbance may occur in the supporting platform of the rotating liquid mirror. In this paper, a robust Youla ( Q) parameterized adaptive regulation approach has been proposed to minimize such kind of vibration signals for the rotating platform system with model uncertainties. Firstly, the inner-loop robust controller with linear quadratic Gaussian with loop transfer recovery ( LQG/LTR) is optimally designed by choosing the suitable weighting functions to achieve the trade-off between robust stability and control performance to deal with random vibration signals. Then the Youla parameter is augmented to construct a set of Q-parameterized stabilizing controllers, and the robust stability of the system is analyzed through dual-Youla parameterization of the uncertain model. The recursive least squares (RLS) adaptive algorithm is developed to tune the Q parameter online to construct a desired adaptive controller for further residual vibration elimination. An experimental evaluation of the controller in reducing the vibration of the supporting platform of a rotating liquid mirror has been carried out, and the results illustrate that the proposed adaptive robust vibration regulation approach can effectively suppress the band-limited random and narrow-band deterministic vibration signals.

Youla parameterized adaptive vibration control against deterministic and band-limited random signals

Abstract Multiple narrow band deterministic and band-limited random disturbance signals will occur during machining process, which will cause vibration and have negative effect on the cutting accuracy. For instance, in a lathe system, spindle rotation can produce narrow band deterministic vibration disturbance and turning process can lead to band-limited random vibration disturbance. In this paper, a H∞ controller with augmented Youla (Q) parameterized adaptive regulation approach is proposed to reject both random and deterministic disturbances. The parameter Q is converged to the desired value by online tune of a recursive least squares (RLS) algorithm. An experimental evaluation on a lathe system has been carried out to indicate the effectiveness of this approach. The result illustrates that the proposed adaptive control method can effectively attenuate the lathe vibrations against the unknown deterministic and band-limited random disturbances.

Comparison of Linear, Nonlinear, Hysteretic, and Probabilistic Models for Magnetorheological Fluid Dampers

Magnetorheological (MR) fluid dampers have a semicontrollable damping force output that is dependent on the current input to the damper, as well as the relative velocity. The mechanical construction, fluid properties, and embedded electromagnet result in a dynamic damper response. This study evaluates four modeling approaches with respect to predicting the multi-input single-output behavior of an experimental MR damper when the inputs are band-limited random signals typically encountered in primary suspension applications. The first two models in this study are static in the sense that there is a unique output for any given set of inputs and no dynamics is present in either model. The third model incorporates a dynamic filter with the nonlinear model to exhibit hysteretic effects, which are known to exist in actual MR dampers. The fourth model is probabilistic and illustrates the dynamic nature of an actual MR damper. The results of this study clearly show the importance of nonlinear and dynamic effects in magnetorheological damper response. This study also highlights the importance of characterizing magnetorheological dampers using excitation signals that are representative of an actual implementation.

A Key Agreement Protocol Using Band-Limited Random Signals and Feedback

Key distribution is an essential element in cryptography. In this paper, the framework of a classical key agreement protocol using band-limited random signals and feedback is presented. The secrecy is derived from masking information by privately held random signals. Critical parameters of the protocol are identified. Raw performance of the system is presented. The secrecy can be enhanced by taking advantages of measures, such as reconciliation and privacy amplification, developed for classical and quantum key agreement protocols.

Digital representations of operators on band-limited random signals

Sampling representations of bounded linear operators (BLOs) acting on extended classes of band-limited signals are derived. These are classes of deterministic signals that are not necessarily square-integrable and random signals with covariance functions that are not necessarily square-integrable on the plane. These classes consist of signals whose Fourier transforms, defined as generalized functions (or distributions), have supports that are subsets of compact sets. The merit of these representations lies in the fact that the image of a signal under an operator may be reconstructed from the samples of the original signal rather than the samples of the image. For example, the derivative of a signal, of any order, may be expressed in terms of the samples of the signal itself instead of the samples of the derivative.

LMS adaptive time delay estimation with two windows

An LMS adaptive time delay estimation method with two windows is presented. This method can reduce the superfluous calculation greatly when the time of correlation is long. It is suitable for the time delay estimation of white band-limited random signals. The feasibility and the performances of this method are also studied.

On the simulation of a class of time delay estimation algorithms

The time delay between signals received at two (or more) sensors has proven to be a useful parameter in passive sonar for estimating the location of an acoustic source. This paper presents the results of a simulation comparing the smoothed coherence transform and maximum likelihood estimation methods to the basic cross correlation technique for time delay estimation. Band-limited random signals which are corrupted by white noise and received at two sensors are considered at various signal-to-noise ratios. The variance of the time delay estimates are compared to the minimum variance obtainable in theory as given by the Cramér-Rao lower bound.

Truncated Sampling Expansions for Band-Limited Random Signals

Truncated Sampling Expansions for Band-Limited Random Signals

Polynomial Interpolation Errors for Band-Limited Random Signals

Polynomial Interpolation Errors for Band-Limited Random Signals