Conventional Feedforward Control Research Articles

Study on Sinusoidal Reference Strategy-Based Adaptive Feedforward Control Applied to Benchmark Wind-Excited Building

The sinusoidal reference strategy (SRS) is a new strategy developed by the present authors for adaptive feedforward vibration control. The recursive-least-squares algorithm is used and a higher frequency sinusoidal signal is adopted as the reference signal. Some shortcomings of the conventional adaptive feedforward control are overcome. Numerical simulations and experimental studies have been carried out. The results show that this strategy can reduce vibration remarkably, and can adapt in real time to dynamic uncertainties and modeling errors. In this paper, the principle of SRS-based adaptive feedforward control is briefly introduced first, then simulation studies are conducted on reducing wind-induced response of the benchmark wind-excited building. The results are also compared to that obtained from linear quadratic Gaussian control.

H∞ Control system for tandem cold mills with roll eccentricity

In order to meet the requirement for higher thickness accuracy in cold rolling processes, it is strongly desired to have high performance in control units. To meet this requirement, we have considered an output regulating control system with a roll-eccentricity estimator for each rolling stand of tandem cold mills. Considering entry thickness variation as well as roll eccentricity as the major disturbances, a synthesis of multivariable control systems is presented based onH∞ control theory, which can reflect the knowledge of input direction and spectrum of disturbance signals on the design. Then, to reject roll eccentricity effectively, a weight function having some poles on the imaginary axis is introduced. This leads to a non-standardH∞ control problem, and the design procedures for solving this problem are analytically presented. The effectiveness of the proposed control method is evaluated through computer simulations and compared to that of the conventional LQ control and feedforward control methods for roll eccentricity.

Design of a strip thickness control system for tandem cold mills using H∞ control techniques

In order to meet the requirement for higher thickness accuracy in cold-rolling mill processes, it is strongly desired to have an increasing high performance in control units. To meet this requirement, an output regulating control system with a roll-eccentricity estimator for each rolling stand of tandem cold mills was considered. Assuming entry thickness variation as well as roll eccentricity to be the major disturbances, a synthesis of multivariable control systems is presented and based on H∞ control theory, which can reflect knowledge of the input direction and spectrum of disturbance signals on design. Then, to reject roll eccentricity effectively, a weight function having some poles on the imaginary axis is introduced. This leads to a non-standard H∞ control problem, and the design procedures for solving this problem are analytically presented. The effectiveness of the proposed control method is evaluated through computer simulations and compared with the conventional linear quadratic control and feedforward control methods for roll eccentricity.

Sinusoidal reference strategy for adaptive feedforward vibration control: numerical simulation and experimental study

A new control approach named Sinusoidal Reference Strategy is developed for adaptive feedforward structural control. In this approach, the recursive-least-squares algorithm is used and a higher frequency sinusoidal signal is utilized as the reference signal. The present approach is able to overcome some of the shortcomings of the conventional adaptive feedforward control. Numerical simulations are then conducted on reducing wind-induced vibrations of the JIN MAO Building in Shanghai, China, with a height of 420 m. A multiple-degree-of-freedom (m.d.o.f.) aeroelastic model of a general super-tall building and an active mass damper (AMD) actuator are designed and manufactured. Wind tunnel tests are carried out to investigate further the control efficiency and robustness of the present approach. Both the simulation and experimental results show that the approach can reduce vibration of super-tall buildings remarkably, and can adapt to dynamic uncertainties and modelling errors of the buildings.

ON-LINE FUNDAMENTAL FREQUENCY TRACKING METHOD FOR HARMONIC SIGNAL AND APPLICATION TO ANC

In this paper, a new indirect feedback active noise control (ANC) scheme based on the fundamental frequency estimation is proposed for systems with a harmonic noise. When reference signals necessary for feedforward ANC configuration are difficult to obtain, the conventional ANC algorithms for multi-tonal noise do not measure the reference signals but generate them with the estimated frequencies [1]. However, the beating phenomena, in which certain frequency components of the noise vanish intermittently, may make the adaptive frequency estimation difficult. The confusion in the estimated frequencies due to the beating phenomena makes the generated reference signals worthless. The proposed algorithm consists of two parts. The first part is a reference generator using the fundamental frequency estimation and the second one is the conventional feedforward control. We propose the fundamental frequency estimation algorithm using decision rules, which is insensitive to the beating phenomena. In addition, the proposed fundamental frequency estimation algorithm has good tracking capability and lower variance of frequency estimation error than that of the conventional cascade ANF method. We are also able to control all interested modes of the noise, even which cannot be estimated by the conventional frequency estimation method because of the poorS /N ratio. We verify the performance of the proposed ANC method through simulations for the measured cabin noise of a passenger ship and the measured time-varying engine booming noise of a passenger vehicle.

Analysis and Implementation of the Double‐Controller Scheme

AbstractThis paper gives some insight into the double‐controller scheme proposed recently. The double‐controller scheme has good robustness as well as simultaneous fast set‐point tracking and good load rejection. Investigations show that it enhances the conventional feedforward control. The stability and robustness of the control scheme are analyzed in the frequency domain and compared with those of the Smith predictor. To further improve the performance of the double‐controller scheme, techniques are proposed to accommodate large uncertainties in process delay time and gain. Two control signals of the double‐controller scheme are employed for extraction of process parameter information and on‐line tuning of the control system. The effectiveness of the proposed techniques is verified through numerical simulations.

Adaptive Attitude Control System for Data Relay Test Satellite

This paper presents an adaptive attitude connol system for DClaRelay Test Satellite(DRTS), which has large inter-orbit link (IOL) antenna. The slew of large antenna disturbs the satellite attitude and hence requires some feed-forward compensations. The applied method appends an parameter identification capability to a conventional feed-forward control, which copes with inaccurcy of distwbance mathematical model. This paper summarizes the adaptive attitude control method and some simulation results.

Water-cooled end-point boundary temperature control of hot strip via dynamic programming

In this paper, an end-point boundary temperature control approach for runout table cooling used in hot strip mills is presented. The system relies on a linearized model for describing heat radiated to the environment and heat transferred to cooling water. At first, a conventional feedforward control design to control the temperature at the end-point boundary, the only measurable controlled parameter, is presented. Subsequently, a modified control scheme which uses dynamic programming to minimize the temperature error at the end-point boundary is discussed in detail. System performance analysis via simulation is presented for both control schemes. Simulation results show that temperature error minimization by dynamic programming improves system performance.

Actuator Dynamics and Delay Compensation Using Neurocontrollers

This study compares the performances of a conventional feedforward controller and a neurocontroller in compensating the effects of the actuator dynamics and computational phase delay in a simple digital vibration control system. The model of this system is based on an earlier experimental study where a two-degree-of-freedom dynamic system was constructed in the laboratory. This system consisted of two electrohydraulic, position-controlled actuator-mass systems, mounted one on top of the other. Bode frequency domain plots were used to identify the governing parameters of the system. Based on the identified model of the experimental setup, a conventional feedforward controller and a neurocontroller are designed to compensate for the adverse effects of actuator dynamics and computational phase delay. The identified model is used to generate training information for the neurocontroller in a frequency domain of interest. To accomplish this endeavor, a neural network simulator is developed. This software uses a modified generalized delta rule with an adaptive momentum term for its learning mechanism and has a dynamic network topology capability. Through experiments and numerical simulations, it is shown that the neurocontroller is far more effective in compensating for actuator dynamics and time delay than the conventional feedforward controller. Factors contributing to the superior performance of the neurocontroller are identified and discussed.

Adaptive attitude control for an artificial satellite with mobile bodies

Feedforward control with a parameter estimation law for an artificial satellite with antennas or manipulators is presented. The proposed method utilizes the linearity of the unknown parameters on the angular momentum. It is possible to append an estimation capability by adding a few terms to conventional feedforward control. A compensation method for the time delay in the velocity control loop of the reaction wheels is also proposed, and its effects on the parameter estimation results are analyzed. The analytical results coincide well with simulation results, and the effects of the time delay are expressed quantitatively. /«>, ke R3xl hce # 3xl

可動部を有する人工衛星の適応的な姿勢制御

Feedforward control with a parameter estimation law for an artificial satellite with antennas or manipulators is presented. The proposed method utilizes the linearity of the unknown parameters on the angular momentum. It is possible to append an estimation capability by adding a few terms to conventional feedforward control. A compensation method for the time delay in the velocity control loop of the reaction wheels is also proposed, and its effects on the parameter estimation results are analyzed. The analytical results coincide well with simulation results, and the effects of the time delay are expressed quantitatively. /«>, ke R3xl hce # 3xl

Vibrationless Access Control of a Positioning Mechanism for High-Order Natural Modes of Vibration.

This paper discusses vibrationless access control of a vibratory positioning mechanism with robustness to high-order natural modes of vibration. From the ceaseless requirement for high-precision positioning, it is desirable to eliminate residual vibration of higher-order natural modes of vibration at a target position. To obtain a feedforward access control force which does not excite high-order natural modes of vibration, a frequency-shaped cost functional whose weighting function is represented by a second-order high-pass filter is used in the optimal control theory. The control force has smaller frequency components in high frequency region as compared with the conventional feedforward control forces. The performance of the proposed vibrationless access control is demonstrated with experimental results using a flexible swing arm positioning mechanism.

Vibrationless Access Control of a Positioning Mechanism for High-Order Natural Modes of Vibration. 2nd Report. Vibrationless Velocity Control.

This paper presents vibrationless velocity control of a vibratory positioning mechanism with robustness for high-order natural modes of vibration. From the requirement for high-precision positioning, it is desirable to eliminate residual vibration of higher-order natural modes of vibration at a target position. To obtain a feedforward access control force which provides a strict final motion state without exciting higher-order natural modes of vibration, two frequency-shaped cost functionals whose weighting functions are represented by first-order and second-order high-pass filters are used in the optimal control theory. The control forces have smaller frequency components in the high-frequency region as compared with the conventional feedforward control forces. The performances of the proposed vibrationless access control methods are demonstrated with experimental results using a flexible swing arm positioning mechanism.

Active Wave Control of a Flexible Beam. On the Power Flow Control.

This paper deals with the active vibration control of a flexible beam with various kinds of boundary conditions. It is the purpose of this paper to investigate the relationship between the power flow and the vibrational energy accumulated in the beam. First, from the viewpoint of the conventional feedforward control method, the role of the power flow to suppress the vibrational energy is discussed. Next, by using a transfer matrix method, this paper derives the control law of the active sink method whose principle has been presented in the previous paper. Then, it is shown that all the vibration modes of a beam with arbitrary boundary conditions are suppressed by the active sink method. It is also shown that the power flow due to the active sink method is different from that of an infinite beam. Furthermore, this paper points out that there exist notches in the frequency characteristics of the power flow, and these are independent of vibration modes. Finally, an experiment is carried out to verify the existence of the active sink.