Variable Notch Filter Research Articles

Powerline interference reduction in ECG signals using variable notch filter designed via variational mode decomposition

Powerline interference reduction in ECG signals using variable notch filter designed via variational mode decomposition

Motion control of industrial robots by considering serial two-link robot arm model with joint nonlinearities

This paper presents a model based motion control approach for industrial robots by considering a serial two-link robot arm model with joint nonlinearities. In order to achieve the desired performance using the model based control approaches, it is important to obtain relevant models of both kinematics and dynamics including nonlinear characteristics. Main nonlinear components that lead to trajectory tracking errors of typical multi-axis industrial robot are joint nonlinearities in each axis and dynamic coupling effects between different axes. In this paper, a parametric modeling approach is introduced to reproduce behaviors of a serial two-link robot arm with joint nonlinearities. Nonlinear stiffness, angular transmission errors, and friction in these two links are directly identified as joint nonlinearities. This approach is applied for the serial two-link arm of a typical multi-axis industrial robot, which has low frequency vibration modes and significantly affects to the trajectory performance. Effectiveness of the modeling is verified by comparative studies with numerical simulations and experiments. Finally, a 2-DOF control scheme with the identified two-link dynamic model and a feedback loop-shaping with a variable notch filter are applied to improve the performance of trajectory tracking and residual vibration suppression.

Vibration Suppression for Angular Transmission Errors in Harmonic Drive Gearings and Application to Industrial Robots

This paper presents a vibration suppression approach for precision positioning mechanisms including harmonic drive gearings (HDGs), using a variable notch filter to suppress mechanical vibrations due to angular transmission errors (ATEs) in HDGs. Mechanisms with HDGs excite resonant vibrations, especially in the condition that the frequency of synchronous components of ATE correspond to the critical mechanical resonant frequency. In the proposed approach, therefore, a variable notch filter with free parameters of frequency and damping is designed to suppress the resonant vibrations during transient response, considering the sensitivity characteristics of the feedback system. The proposed approach has been applied to motion control of an actual industrial 6-axis robot and verified by numerical simulations and experiments.

가변 노치필터에 의한 능동형 AC 전자부하의 3상 전류 불평형 저감

In this paper, the test bed using three-phase PWM converter connected with single phase inverter in series is set up to configure an active AC electric load. Since the two topologies, three-phase PWM converter and single-phase inverter, can be operated bidirectionally, the system not only re-generates surplus power to grid but also prevents power dissipation. However, the construction of system has a drawback. That is, ripple components two times of inverter operation frequency occur at DC-Link due to cascade connection, it can be cause of three phase unbalance Since the operational characteristic of the active AC electric load, the power frequency entered into the electric load can be varied, and the ripple of DC-Link is changed as well. In this paper, the three-phase PWM converter using a variable notch filter is proposed, and the reduction of three-phase current unbalance is presented. the validity of the proposed PWM converter using a variable notch filter is verified by the simulation and experimental results.

波動歯車の角度伝達誤差に起因する共振振動の可変ノッチフィルタによる制振制御

This paper presents a vibration control using a variable notch filter to suppress mechanical vibrations due to angular transmission errors (ATEs) in harmonic drive gearings (HDGs). Mechanisms including HDGs excite resonant vibrations due to ATEs, especially in the condition that the frequency of synchronous components of ATE correspond to the ones of critical mechanical resonant vibration. In the proposed approach, therefore, a variable notch filter with free parameters of frequency and damping is designed to suppress the resonant vibrations during transient response, considering the sensitivity characteristics of the feedback system. The proposed control has been verified by numerical simulations and experiments for a uni-link robot arm.

Discussion on: “H∞ Control for Networked Control Systems with Limited Communication”

This article describes the design of a high performance 2-DOF controller for an electromechanical system consisting of a rotary flexible spindle hovered by Active Magnetic Bearings (AMB). The purpose of such a controller is to achieve the better positioning possible of the spindle by means of a good stabilization mechanism and by counteracting the vibrations generated naturally by the rotation. The implementation of this controller is based on three main blocks, a stabilization block, a vibration minimization block and, if needed, a dynamics decoupler block between the previous ones. The stabilization controller is designed utilizing a MIMO decoupling technique. With the aim of proving its effectiveness, two different stabilization controllers (PID and H∞) are presented. On the other hand, an adaptive feedforward algorithm which is in charge of the vibration minimization is implemented. In order to not feedback the vibration and, therefore, to decouple the controller's dynamics, the implementation of a variable Notch filter is discussed. It is demonstrated that this optional block can enhance or impoverish the behavior of the system depending on several factors such as resonances or rotational speed measurement.Experimental results and simulations are provided to show the effectiveness of the complete design process.

2-DOF Controller Design for Precise Positioning a Spindle Levitated with Active Magnetic Bearings

This article describes the design of a high performance 2-DOF controller for an electromechanical system consisting of a rotary flexible spindle hovered by Active Magnetic Bearings (AMB). The purpose of such a controller is to achieve the better positioning possible of the spindle by means of a good stabilization mechanism and by counteracting the vibrations generated naturally by the rotation. The implementation of this controller is based on three main blocks, a stabilization block, a vibration minimization block and, if needed, a dynamics decoupler block between the previous ones. The stabilization controller is designed utilizing a MIMO decoupling technique. With the aim of proving its effectiveness, two different stabilization controllers (PID and H ∞ ) are presented. On the other hand, an adaptive feedforward algorithm which is in charge of the vibration minimization is implemented. In order to not feedback the vibration and, therefore, to decouple the controller's dynamics, the implementation of a variable Notch filter is discussed. It is demonstrated that this optional block can enhance or impoverish the behavior of the system depending on several factors such as resonances or rotational speed measurement. Experimental results and simulations are provided to show the effectiveness of the complete design process.

Construction and Performance of “Inverse Monochromator” as Wavelength Variable Notch Filter for Raman Spectroscopy

A monochromator called “Inverse monochromator” has been designed and constructed, and its performance as a wavelength variable notch filter has been examined. Two single monochromators of small size are put in back to back configuration to make a monochromator with zero-dispersion. The 0.7-mm-diameter vertical rod at the center of the intermediate aperture is used to reject a narrow wavelength band selected with the wavelength scale knob. The rejection factor is measured to be 2.5×10-3 for central wavelength and quasi white light, being about 90 nm wavelength bandwidth, is obtained from the intermediate aperture with 12 mm width. The newly designed monochromator acts as wavelength variable notch filter and can be effectively used in Raman spectroscopy with optional excitation wavelength.