Rejection Of Narrow Band Disturbances Research Articles

Systematic Control Design for Adaptive Rejection of Narrow-Band Disturbances Based on a Novel Resonant Generalized Extended State Observer

In this paper, the adaptive rejection of multiple narrow-band disturbances with time-varying frequencies is investigated. A systematic control approach based on a resonant generalized extended state observer (RGESO) is proposed. The frequency response of the RGESO is shaped into a desired form to reject the total disturbance, including the wide-band uncertainties and the narrow-band disturbances. The state-space realization of the RGESO is also provided to estimate both the states and the total disturbance. To handle the time-varying frequencies of the narrow-band disturbances, a direct frequency estimation approach based on the Levenberg–Marquardt method and an online supervision strategy is presented to improve convergence and reliability, and the estimations are then used to adapt the RGESO parameters. Parameter tuning and stability robustness analysis methods are also developed for the proposed scheme to facilitate its application. Finally, extensive simulations are conducted to demonstrate the effectiveness of our method.

Parallel-filter-based observer control for unknown multiple narrow-band disturbance rejection

An observer-based control method with parallel Q-filter is proposed to reject unknown multiple narrow-band disturbances for line of sight stabilization in telescope systems. In general, wide-band or multiple narrow-band disturbances rejection of observer-based control can be transformed into designing Q-filter, which could be too high-order to achieve fully-accuracy digital implementation, resulting in degrading the closed-loop performance or even causing instability. Therefore, a new parallel type of Q-filters is proposed to flexibly adjust the number of Q-filter in the sensitivity function and effectively reduce the computational complexity. A sufficient condition of the effectiveness for the parallel Q-filter and the closed-loop stability is derived and verified through simulations. Furthermore, disturbance frequencies can be on-line identified to adaptively optimize the Q-filter parameters. The effectiveness of the proposed method is validated on the image-based stabilization subsystem of a segmented lightweight large-scaled diffractive telescope.

Adaptive rejection of narrow-band disturbances in the presence of plant uncertainties—A dual Youla–Kucera approach

The stability of adaptive disturbance rejection schemes using Youla–Kucera (YK) parametrization and the internal model principle (IMP) in the presence of plant model uncertainties is investigated. The problem is approached by using the dual Youla–Kucera parametrization for the description of the plant model uncertainties. The known disturbance case is discussed first, emphasizing the need of over parametrization of the Youla–Kucera filter used for control in order to both solving the IMP and the stability problems. Then this solution is extended for the case of unknown disturbances leading to the use of a parameter adaptation algorithm with projection. A stability analysis of the adaptive scheme is provided. Simulation results on relevant examples and experimental evaluation on an active noise attenuation system illustrate the possibilities of this approach for handling significant plant-model mismatch.

A Collaborative Sensing and Model-Based Real-Time Recovery of Fast Data Flows From Sparse Measurements

This article considers the real-time recovery of a fast time series by using sparsely sampled measurements from sensors whose sampling speeds are prohibitively slow originally. Specifically, when the fast signal is an autoregressive process, we propose an online information recovery algorithm that reconstructs the dense underlying temporal dynamics fully by systematically modulating two slow sensors, and by exploiting a model-based fusion of the sparsely collected data. We provide the design of collaborative sensing and model-based information recovery algorithm, impacts of parameter choosing and model singularity, and methods to reduce computational complexity and increase prediction robustness. The proposed method is experimentally verified in an optical beam steering platform for additive manufacturing. Application to a closed-loop disturbance rejection problem reveals the feasibility to eliminate fast disturbance signals with the slow and not fully aligned sensor pair in real time, and in particular, the rejection of narrow-band disturbances whose frequencies are much higher than that of the Nyquist frequencies of the sensors.

Youla parameterized adaptive vibration suppression with adaptive notch filter for unknown multiple narrow band disturbances

The vibration caused by the multiple narrow band disturbances exists widely in the mechanical systems. In this paper, a Youla parameterized adaptive control approach is introduced for the rejection of unknown multiple narrow band disturbances. The adaptive notch filter weighted Q (Youla) parameter is adopted to the online internal model principle-based regulator, so that the disturbances can be fully attenuated and the robustness of the closed-loop system is improved. A central controller is first designed to obtain the desired baseline loop shape. Then, the controller is augmented by a notch filter weighted Q parameter to construct a series of stable controllers and the Q parameter in the stable controllers is tuned online to obtain the desired controller. The adaptive control method is applied in a data storage system to attenuate the flying height vibration and the experimental results illustrate the effectiveness of the proposed approach in rejecting unknown multiple narrow band disturbances.

Hybrid active suspension system of a helicopter main gearbox

This paper considers experiments on the control of a helicopter gearbox hybrid electromagnetic suspension. As the new generation of helicopters includes variable engine revolutions per minute (RPMs) during flight, it becomes relevant to add active control to their suspension systems. Most active system performance derives directly from the controller construction, its optimization to the system controlled, and the disturbances expected. An investigation on a feedback and feedforward filtered-x least mean square (FXLMS) control applied to an active DAVI suspension has been made to optimize it in terms of narrow-band disturbance rejection. In this paper, we demonstrate the efficiency of a new hybrid active suspension by combining the advantages of two different approaches in vibration control: resonant absorbers and active suspensions. Here, a hybrid active suspension based on the passive vibration filter called DAVI is developed. The objective of this paper is to prove the relevancy of coupling a resonant vibration absorber with a control actuator in order to create an active suspension with larger bandwidth efficiency and low energy consumption. The simulations and experimentation achieved during this suspension system development support this hypothesis and illustrate the efficiency and low energy cost of this smart combination.

Modified direct adaptive regulation scheme applied to a benchmark problem

A direct adaptive regulation scheme using an adaptive FIR Youla–Kučera Filter has been proposed for solving the EJC Benchmark on rejection of multiple unknown and time-varying narrow-band disturbances (Castellanos Silva et al., 2013 [4]). Despite excellent results, this approach requires a careful design of the central controller in terms of selection of some of the assigned closed-loop poles. A modified scheme is proposed in this paper which will incorporate a particular adaptive IIR Youla–Kučera Filter, called ρ-notch structure (the denominator is a projection inside the unit circle of the poles of the model of the disturbance which has roots on the unit circle). The adaptive scheme estimates separately the numerator and denominator parameters of the IIR Youla–Kučera Filter. Stability and convergence proofs are given along with simulation and real-time results. Comparison with results already obtained for the EJC Benchmark is provided. The use of this approach drastically simplifies the design of the central controller and provides even better results than (Castellanos Silva et al., 2013 [4]) with the advantage to use a single central controller independent of the number of narrow band disturbances.

Multiple-Disturbance Rejection for High Precision Positioning of a VCM Servo Gantry

This paper presents an multiple disturbance rejection approach for rejecting narrow-band disturbances as well as norm-bounded random disturbances, with applications to high precision positioning of a Voice Coil Motor (VCM) actuated servo stage. An adaptive optimal phase filter design method is proposed for the rejection of frequency-varying narrow-band disturbances at unknown frequency range. With a parallel connection of the proposed adaptive filter, a robust H∞ controller can be synthesized with mixed sensitivity optimization for the purpose of both robust stability and rejection of norm-bounded random disturbances. The proposed control architecture is implemented to a VCM servo gantry to achieve high precision positioning in the presence of various disturbances.

H∞ gain-scheduled controller design for rejection of time-varying narrow-band disturbances applied to a benchmark problem

A new method for H∞ gain-scheduled controller design by convex optimization is proposed that uses only frequency-domain data. The method is based on loop shaping in the Nyquist diagram with constraints on the weighted infinity-norm of closed-loop transfer functions. This method is applied to a benchmark for adaptive rejection of multiple narrow-band disturbances. First, it is shown that a robust controller can be designed for the rejection of a sinusoidal disturbance with known frequency. The disturbance model is fixed in the controller, based on the internal model principle, and the other controller parameters are computed by convex optimization to meet the constraints on the infinity-norm of sensitivity functions. It is shown next that a gain scheduled-controller can be computed for a finite set of disturbance frequencies by convex optimization. An adaptation algorithm is used to estimate the disturbance frequency and adjusts the parameters of the internal model in the controller. The simulation and experimental results show the good performance of the proposed control system.

Direct adaptive rejection of unknown time-varying narrow band disturbances applied to a benchmark problem

The paper presents a direct adaptive algorithm for the rejection of unknown time-varying narrow band disturbances, applied to an adaptive regulation benchmark. The objective is to minimize the residual force by applying an appropriate control signal on the inertial actuator in the presence of multiple and/or unknown time-varying disturbances. The direct adaptive control algorithm is based on the internal model principle (IMP) and uses the Youla–Kučera (YK) parametrization. A direct feedback adaptive regulation is proposed and evaluated both in simulation and real-time. The robustness is improved by shaping the sensitivity functions of the system through band stop filters (BSF).

Hybrid proportional derivative/repetitive control for active vibration control of smart piezoelectric structures

This paper presents a hybrid control method for active vibration control of smart piezoelectric structures. The proposed controller consists of a proportional derivative (PD) controller for broadband disturbance rejection and a repetitive controller for narrowband disturbance rejection. The proposed design embeds the repetitive controller by solving a Bezout identity satisfying deterministic constraint into an existing PD feedback control loop. The applied method has two main advantages: (1) each controller design is modularized with an “add-on” property for performance improvement; (2) it achieves superior vibration suppression for both impulse and persistent excitation. Experimental results on a piezoelectric cantilever beam demonstrate the effectiveness of the proposed hybrid controller design method.

A peak filtering method with improved transient response for narrow-band disturbance rejection in hard disk drives

Peak filtering methods are commonly used in track-following control of hard disk drives (HDDs) to suppress narrow-band disturbances around a specific frequency. When there are significant plant dynamics within the bandwidth of the filter, the closed-loop system is prone to be unstable due to the lightly damped poles of the filter, as well as lightly damped poles of the plant. On the other hand, settling response of such peak filters during shock disturbances is slow, and increases tremendously with decreasing damping ratios. In this article, we present a novel design of peak filters with improved transient responses using a phase scheduling method in addition to varying gain and damping ratio. By doing so, the stability margin of the closed-loop systems during both transient stage and steady-state stage will be improved. The effectiveness of the proposed methodology is verified with extensive simulations and the proposed method is then applied in an integrative servo analysis platform to carry out a scaling exercise to evaluate and predict servo performance to support 10 Terabits/in2.

Reset Control for Midfrequency Narrowband Disturbance Rejection With an Application in Hard Disk Drives

A reset disturbance compensation scheme is developed to reject midfrequency narrowband disturbances, with an application to the hard disk drives (HDDs). Generally, disturbance at the midfrequency band is not effective to reject through the feedback control based on the internal-model principle or high gain control due to phase stability. This paper investigates a reset control scheme and its favorable approximate frequency response using the describing function. The reset control makes its gain-phase frequency response break through the fundamental Bode's constraint of linear time-invariant system and provides a maximal phase lead at desired frequencies without affecting gain's characteristic. With additional phase lead, the issue of phase stability can be solved. A reset midfrequency narrowband compensator is designed by incorporating the reset controller and a narrowband filter. The implementation on a real HDD servo system shows the removal of midfrequency disturbance due to disk vibration is improved by 50% compared with the linear control scheme, resulting in a track misregistration (TMR) reduction of 32%.

Adaptive regulation—Rejection of unknown multiple narrow band disturbances (a review on algorithms and applications)

The paper addresses the problem of attenuation (rejection) of unknown and time varying multiple narrow band disturbances without measuring them. In this context the disturbance model is unknown and time varying while the model of the plant is known (obtained by system identification) and almost invariant. This requires to use an adaptive feedback approach. The term “adaptive regulation” has been coined to characterize this control paradigm. Application domains include: mechanical and mechatronics systems, active vibration and noise suppression systems, some types of bio-chemical reactors. The paper reviews the various techniques proposed for solving this problem. It will focus on the presentation of the direct and indirect adaptive regulation strategies using the internal model principle and the Youla–Kucera parametrization which have been extensively used in applications. The paper also reviews a number of applications including: active suspension systems, active vibration control systems, active noise control, bio-chemical reactors, distributed flexible mechanical structures and Blu-ray disc drives. Real time results obtained on various applications will illustrate the methodology.

A Peak Filtering Method with Improved Transient Response for Narrow-Band Disturbance Rejection in Hard Disk Drives

Peak filtering methods are commonly used in track-following control of hard disk drives (HDDs) to suppress narrow-band disturbances around a specific frequency. When there are significant plant dynamics within the bandwidth of the filter, the closed-loop system is prone to be unstable due to the lightly damped poles of the filter, as well as lightly damped poles of the plant. On the other hand, settling response of such peak filters during shock disturbances is slow, and increases tremendously with decreasing damping ratios. In this paper, we present a novel design of peak filters with improved transient responses using a phase scheduling method in addition to varying gain and damping ratio. By doing so, the stability margin of the closed-loop systems during both transient stage and steady-state stage will be improved. The effectiveness of the proposed methodology is verified with extensive simulations and the proposed method is then applied in an integrative servo analysis platform to carry out a scaling exercise to evaluate and predict servo performance towards 10 Terabits/in2.

Multi-frequency disturbance rejection via blending control technique for hard disk drives

This paper is concerned with the rejection of multiple narrowband disturbances in hard disk drives (HDDs). Inspired by a control blending idea, the multi-frequency disturbance rejection is formulated as a blending control problem. Each disturbance rejection is accomplished by using the H 2 optimal control method. Based on all H 2 optimal controllers, the blending technique is applied to yield a single controller which is capable of achieving rejection of all disturbances. Rejections of two and three disturbances for a 1.8-inch HDD VCM actuator are taken as application examples in the paper. Simulation and experimental results show that the ultimate controller results in a simultaneous attenuation of disturbances with frequencies higher or lower than the closed-loop system bandwidth. Moreover, the method turns out to be able to lift phase and thus prevent phase margin loss when it is used to deal with disturbances near bandwidth.

Rejecting high frequency disturbances with disturbance observer and phase stabilized control

This paper takes into consideration the rejection of narrow-band disturbances at two frequencies higher than servo bandwidth in order to obtain good positioning accuracy for a micro-actuator. A phase stabilized feedback controller combined with a disturbance observer structure is applied to achieve the rejection of the two disturbances. A high frequency bandpass filter is adopted in the disturbance observer in order to reject the high frequency disturbance, and simultaneously the stability of the feedback control loop is remained when the disturbance observer is added on to the external stabilized controller. The effectiveness of the combined control is investigated through simulation and experiment results, which show that this control scheme can reduce position error significantly and is better than using phase stabilized feedback control only or proportional-integral-derivative (PID) controller with notch filters.

Adaptive narrow band disturbance rejection applied to an active suspension—an internal model principle approach

This paper presents a methodology for feedback adaptive control of active vibration systems in the presence of time varying unknown narrow band disturbances. A direct adaptive control scheme based on the internal model principle and the use of the Youla–Kucera parametrization is proposed. This approach is comparatively evaluated with respect to an indirect adaptive control scheme based on the estimation of the disturbance model. The comparative evaluation is done in real time on an active suspension system.

Adaptive Control of Semiactive Variable Stiffness Devices for Narrow-Band Disturbance Rejection

The present study examines the potential of using a semiactive controllable stiffness device, whose spring coefficient can be modulated in real-time, for tonal disturbance rejection applications. A frequency-domain control algorithm is developed for determining the spring coefficient variation (at twice the disturbance frequency) that minimizes the force transmitted to the support at the disturbance frequency. The effectiveness of open loop, closed loop, and adaptive controllers in rejecting the transmitted disturbances are evaluated. The results of the study indicate that when limits in stiffness coefficient variation are considered, the support force could be reduced by about an additional 30%, beyond the levels due to the passive isolation characteristics (no cyclic stiffness modulation). When the disturbance phase changes during operation, the effectiveness of the open loop controller is rapidly degraded. While the closed loop controller (with inputs based on current levels of force transmitted to the support) performed better, there was still some degradation in performance, and transmitted support forces were not reduced to levels prior to change in disturbance phase. The results show that for the semiactive system to retain its effectiveness in rejecting disturbances, a closed loop, adaptive controller (with on-line system identification) is required; even when there is only a change in disturbance, and no change in basic system properties. An explanation for this phenomenon, related to the bilinear nature of the semiactive system, is provided.

Robust disturbance rejection for improved dynamic stiffness of a magnetic suspension stage

Magnetic suspension is an attractive approach in realizing ultraprecision multiple-degree-of-freedom actuation for precision engineering. However, improving the dynamic stiffness of magnetic-suspension systems is an engineering challenge due to their noncontact nature. Two disturbance rejection algorithms that improve the dynamic stiffness of a magnetic-suspension stage (MSS) are presented in this paper. For rejection of narrow-band disturbances with unknown frequencies, an internal model principle-based control together with a frequency estimation algorithm based on adaptive-notch filtering is proposed. A chattering-free sliding mode (CFSM) disturbance rejection algorithm is developed in order to reject wide-band disturbances. The CFSM disturbance rejection scheme includes a continuous approximation of the switching function to avoid chattering, an integral control term to reduce the switching magnitude, and a derivative control term to elevate the bandwidth of disturbance rejection. Experimental results verified that the disturbances can be effectively rejected with the two developed algorithms. Consequently, the dynamic stiffness of the MSS is greatly improved.