Disturbance Cancellation Research Articles

An iterative learning design for repeatable runout cancellation in disk drives

In this paper, we consider the iterative learning control (ILC) framework to design a reference signal that directly cancels periodic disturbances in a feedback measurement. Cancellation of periodic disturbances is useful in reducing undesirable repeatable tracking errors in applications such as the two-stage servo track writing process for disk drives. A general problem description is given for a linear discrete-time periodic system and convergence results for the learning system are derived. A learning filter is designed with the use of a finite-impulse response model approximation for the inverse of the closed-loop sensitivity such that convergence is achieved in learning a reference signal that provides cancellation with periodic perturbations affecting the system measurement. The ILC algorithm is applied to a disk drive system where experimental results demonstrate the effectiveness of the method in reducing periodic measurement disturbances.

Disturbance Cancellation Control and Coupling Vibration of an Elastic Supported Cylinder and Wake Oscillator (Improvement of Control Simulation by Using van der Pol Wake Oscillator Model)

This paper studies disturbance cancellation control to suppress vortex-induced vibration of a circular cylinder in a cross flow. The cylinder is supported by two pairs of elastic beams and electromagnets are used as control devices. Fluctuating lift force acting on a vortex-induced cylinder is assumed as a disturbance. An observer is constructed to estimate the disturbance. Two different types of disturbance are assumed to describe the fluctuation of vortex shedding. One is a sinusoidal wave and the other is a wake oscillator represented by van der Pol equation. Simulation and experiments are carried out for the examination of the control performance.

Integral controller design based on disturbance cancellation: Partial LTR approach for non-minimum phase plants

For non-minimum phase plants, the loop transfer recovery (LTR) design of integral controllers based on the disturbance cancellation is considered. Since the design requires an unstabilizable extended plant, the standard LTR method cannot be applied. A new partial LTR method is proposed to overcome the difficulty. The target of the proposed design is a fictitious controller including a disturbance estimator based on the measurement of the minimum phase state. It is shown that the Riccati equation including the gain matrix of the disturbance estimator in the target can be used to recover the target feedback property in the output feedback controller. A simple design example is presented to show the effectiveness of the proposed method.

Adaptive feedforward cancellation of sinusoidal disturbances in superconducting RF cavities

A control method, known as adaptive feedforward cancellation (AFC), is applied to damp sinusoidal disturbances due to microphonics in superconducting radio frequency (SRF) cavities. AFC provides a method for damping internal and external sinusoidal disturbances with known frequencies. It is preferred over other schemes because it uses rudimentary information about the frequency response at the disturbance frequencies, without the necessity for an analytic model (transfer function) of the system. It estimates the magnitude and phase of the sinusoidal disturbance inputs and generates a control signal to cancel their effect. AFC, along with a frequency estimation process, is shown to be very successful in the cancellation of sinusoidal signals from different sources. The results of this research may significantly reduce the power requirements and increase the stability for lightly loaded continuous-wave SRF systems.

ボイスコイルモータを用いた小型車両用シートの制御（外乱相殺制御を用いた実験的考察）

The purpose of this study was to examine the effectiveness of active seat suspension when it is applied to small cars, and to survey the problems associated with its practical use. A small active seat suspension, which is easy to install, was designed and manufactured for one-seat electric automobiles. In a realistic driving test, a test road was prepared in which the concavity and convexity of an actual road surface were simulated by using hard rubber. Our aim was to examine the vibration isolation effect for the driver's seat, using disturbance cancellation control. We examined the control performance with respect to the variation of the parameters for the frequency and the driver's weight. We performed experiments in several conditions, and compared the results of control performance with passive control, feedback control, feedforward control, and disturbance cancellation control. As a result, we confirmed the suppressive effect of the disturbance cancellation control.

115 弾性支持円柱と後流振動子の連成振動と外乱相殺制御

115 弾性支持円柱と後流振動子の連成振動と外乱相殺制御

Stability of the frequency adaptive control technique and its application to compact disk drives

This paper presents the stability and implementation of the frequency adaptive control technique (FACT) for periodic disturbance cancellation in compact disk drives. The compact disk drive operates at various rotating speeds and modes, which causes periodic disturbances with different fundamental frequencies. To solve this, FACT provides a suitable framework for periodic disturbance rejection in the cases where the fundamental frequencies of the disturbance are alterable. This paper shows that the convergence property of parameters in the proposed adaptive algorithm is exponentially stable. The FACT controller is also shown to be equivalent to a linear time-invariant controller, and the upper bound of adaptation gains is determined according to system dynamics for the attenuation of periodic disturbances. These results are verified by experiments using the track-following system of a high speed CD-ROM drive. It is found that the stable limits of the adaptation gains match well between analytic and experimental results. The results significantly enhance the ability to design and analyze the FACT controller for a variety of applications where periodic disturbances with various fundamental frequencies are encountered.

A simple and robust speed control scheme of permanent magnet synchronous motor

This paper presents a simple and robust speed control scheme of Permanent Magnet Synchronous Motor (PMSM). It is to achieve accurate control performance in the presence of load torque and plant parameter variation. A robust disturbance cancellation feed forward controller is used to estimate the torque disturbance. The simple and practical control scheme is easily implemented on a PMSM driver using a TMS320LF2407 DSP. The effectiveness of the proposed robust speed control approach is demonstrated by simulation and experimental results.

Periodic disturbance cancellation with uncertain frequency

This paper presents a new algorithm to cancel periodic disturbances with uncertain frequency. The disturbances are cancelled using an internal model structure with adaptive frequency, in parallel with a stabilizing controller. The time-varying internal model controller's states, in steady state, can be mapped to two time-invariant variables: the magnitude or energy of the internal model and frequency of the disturbance. An additional integral controller then can be used to reduce the difference between the internal model controller (IMC) and disturbance frequency to zero. The stability of the feedback control system with this algorithm and convergence of the algorithm to the correct frequency with exact disturbance cancellation are justified by singular perturbation and averaging theories. The algorithm is locally exponentially stable, rather than asymptotically stable. Simulations demonstrate the performance of the algorithm, the ability of this algorithm to identify the frequency of periodic disturbances and to reject periodic disturbances with uncertain frequency.

薄鋼板磁気浮上搬送システムにおける外乱相殺制御に関する基礎的検討(昇降装置・物流機械の運動と制御,OS2 交通・物流機械のダイナミクス(振動,制御を含む))

In the thin steel plates which are used in many industrial products, flaws on the plate surface and peeling during a surface treatment process are induced due to the use of many rollers in the conveyance process. These lead to the deterioration of the quality of the plate surface. Electromagnetic levitation techniques can solve many problems in the conveyance modes of sheet steel. The authors have proposed a magnetic levitation control system for maintaining the absolute distance of the plate surface and the electromagnet, and carried out an experiment on digital control. In this study, the equipment was designed so that electromagnets, which are used for the magnetic levitation of a steel plate, vibrate vertically. For basic research, a controlled object was assumed to be a single-degree-of-freedom model and disturbance cancellation control was used as the control method. The vibration isolation effect observed in the steel plate was confirmed by experimentation.

Direct adaptive cancellation of periodic disturbances for multivariable plants

A multivariable adaptive scheme is proposed that is designed to reject periodic disturbances of unknown frequency at multiple sensor locations. The case of square systems is considered, as well as the common case where there are more sensors than actuators (overdetermined systems). The disturbances are assumed to contain multiple harmonics associated with a single fundamental frequency, as is the case if the source of the disturbances is a rotating machine. Accordingly, the control inputs are selected to be periodic signals with a frequency determined by a single frequency estimate. Although the adaptive scheme is highly nonlinear, approximations yield an analysis that enables a linear time-invariant design of the algorithm. The analysis also gives useful information about the dynamic behavior of the system and the selection of the design parameters. Experimental results show that the proposed scheme is able to significantly reduce acoustic noises with constant or time-varying frequency at multiple locations in an enclosure.

Adaptive sinusoidal disturbance cancellation for precise pointing of stewart platforms

This paper combines an adaptive sinusoidal disturbance cancellation scheme with fault tolerant pointing algorithms for Stewart platforms. This results in a fault-tolerant pointing system capable of low-frequency tracking, mid-frequency rejection of large monotone disturbances, and high-frequency passive vibration isolation. Since often the frequency of the monotone sinusoidal disturbance cannot be precisely known, a phase-locked loop (PLL) algorithm is used to catch the frequency and a method for PLL design is developed. Experimental results on the University of Wyoming Stewart platform demonstrate that pointing errors caused by a monotone disturbance decrease 50-fold even in the presence of multiple actuator failures.

616 渦励振される弾性支持円柱の周波数変化に適応する外乱相殺制御

616 渦励振される弾性支持円柱の周波数変化に適応する外乱相殺制御

Quantitative speed control for SRM drive using fuzzy adapted inverse model

Quantitative and robust speed control for a switched reluctance motor (SRM) drive is considered to be rather difficult and challenging owing to its highly nonlinear dynamic behavior. A speed control scheme having two-degree-of-freedom (2DOF) structure is developed here to improve the speed dynamic response of an SRM drive. In the proposed control scheme, the feedback controller is quantitatively designed to meet the desired regulation control requirements first. Then a reference model and a command feedforward controller based on an inverse plant model are employed to yield the desired tracking response at nominal case. As the variations of system parameters and operating conditions occur, the prescribed control specifications may not be satisfied any more. To improve this, the inverse model is adaptively tuned by a fuzzy control scheme so that the model-following tracking error is significantly reduced. In addition, a simple disturbance cancellation robust controller is added to improve the tracking and regulation control performances further.

Neurointerfaces

A neurointerface is a nonlinear filtering system based on neural networks (NNs) that serves as a coupler between a human operator and a nonlinear system or plant that is to be controlled or directed. The purpose of the coupler is to ease the task of the human controller. The equations of the plant are assumed to be known. If the plant is unstable, it must first be stabilized by feedback. Using the plant equations, off-line automatic learning algorithms are developed for training the weights of the neurointerface and the weights of an adaptive plant disturbance canceller. Application of these ideas to backing a truck with two trailers under human direction is described. The "truck backer" has been successfully demonstrated by computer simulation and by physical implementation with a small radio-controlled truck and trailers.

INTEGRAL CONTROLLER DESIGN BASED ON DISTURBANCE CANCELLATION VIA PARTIAL LTR

For non-minimum phase plants, integral controller design based on disturbance cancellation is discussed. A new partial loop transfer recovery (LTR) technique is proposed. The target of the output feedback design is a minimum phase state feedback controller including a disturbance estimator. It is shown that the feedback property of the target can be recovered by a formal procedure using a Riccati equation with a fictitious disturbance term.

Disturbance Cancellation Control of a Circular Cylinder with Elastic Supports under Vortex-Induced Vibration.

This paper investigates disturbance cancellation control to suppress vortex-induced vibration of a circular cylinder in a cross flow. The controller consists of an optimal regulator and a feedforward control. The external force of the vortex shedding is assumed to be a harmonic force, and the magnitude of the disturbance is estimated by a minimal-order observer for the feedforward control. The cylinder is supported by two pairs of elastic beams, and electro-magnets are used as control devices. Experiments have shown that the present method is effective in reducing the vibration amplitude of circular cylinders. We investigate the effect of frequency error in the observer on disturbance cancellation control.

507 弾性支持された円柱構造物の渦励起振動と外乱相殺制御

507 弾性支持された円柱構造物の渦励起振動と外乱相殺制御

Positioning and Vibration Control by Electromagnetic Actuator Using Rubber Film.

This study investigates the positioning and the vibration isolation performance of a precise positioning mechanism which is composed of a electromagnetic actuator using a rubber film. The results obtained by the experiments are as follows : (1) The actuator has the hysteresis, but it has not influence on the positioning accuracy by applying PI control. (2) The rubber film plays the part of the passive vibration isolation. (3) As a result of employing the disturbance cancellation control, the vibration isolation performance improves further.

A Robust Speed Controller With VSS Tuning Of Disturbance Cancellation For An Induction Motor Drive

ABSTRACTA robust speed controller for an induction motor drive that achieves quantitative control and considers the effects of nonlinearities is presented in this paper. First, a two‐degree‐of‐freedom controller (2DOFC) is designed according to the estimated model for the nominal case and given speed specifications. Then, the control characteristics and limitations of the conventional robust controller are investigated. Accordingly, a modified robust speed controller based on disturbance cancellation is developed, wherein tuning of disturbance cancellation is performed via a variable structure system (VSS) controller. The estimated model mismatched error and its derivative are used as the driven inputs of the VSS controller. Greater robustness and flexibility in achieving a compromise between control effort and control performance can be achieved using the proposed controller. The effectiveness of the proposed controller is demonstrated by simulation and measured results.