Positive Velocity Feedback Control Research Articles

Identification of the parameters of the Maxwell model using self-excited oscillation

In the present paper, a method for identifying the parameters of the Maxwell model using self-excited oscillation is proposed. Viscoelastic materials have the properties of both elasticity and viscosity and are generally used in dynamic systems to reduce vibration and noise. We herein focus on the measurement of linear viscoelasticity and investigate the widely used Maxwell model. The conventional measurement method for obtaining the dynamic mechanical properties of viscoelastic materials is easily affected by the friction and inertia of the measurement instrument. The proposed method uses the positive velocity feedback control to produce the self-excited oscillation, and the measurement results are not affected by these effects. The validity of the proposed method is confirmed experimentally using a prototype measurement system.

Networked active vibration control of structural systems: A nonsmall input delay approach

This paper investigates the networked active vibration control for a multi-degree-of-freedom structural system subject to modeling uncertainties, stochastic sensor faults, and earthquake excitations. By adopting a positive velocity feedback controller and introducing a communication network that produces proper network-induced delays and packet dropouts in the feedback control loop, the closed-loop system is first modeled by an uncertain stochastic system with a nonsmall interval time-varying input delay. Then a delay-dependent criterion is derived by employing a complete Lyapunov–Krasovskii functional such that the stochastic system with the proper nonzero input delay is stochastically stable with L2-gain performance, but unstable without delay. An iterative algorithm is presented to design the networked controller. A three-storey shear-beam building model subject to the El Centro 1940 earthquake is given to validate the proposed approach.

Vibration reduction in aerospace structures via an optimized modified positive velocity feedback control

In this paper, an optimized positive feedback based control approach is developed for unwanted resonant vibration attenuation of flexible lightweight aerospace structures. A modified form of the positive velocity feedback control (MPVF) is implemented, where the resonant compensator of each mode is enhanced with a parallel lossy integrator. For multi-mode control purpose and to control n-modes, n sets of parallel compensators are required. A focus of this paper is on development of effective gain optimization methods in order to improve the multi-mode suppression performance of the vibration controller. The optimization problem is addressed via the M-norm optimization method and the Linear Quadratic Regulator (LQR). A flexible clamped-free beam is considered as a sample aerospace structure, and the controller verification is performed experimentally. Results show that vibration velocity is well reduced, which is important in preventing fatigue failures in aerospace structures. The LQR-optimized MPVF provides a compensated result between vibration amplitude reduction and the consumed control power. The M-norm approach, on the other hand, aims to directly suppress each mode based on the assigned weighting coefficients. Since an M-norm-optimized MPVF controller focuses on modes with higher amplitudes of velocity, it provides a higher level of vibration suppression than LQR-optimized method.

Self-excited vibrational viscometer for high-viscosity sensing

A method for vibrational viscometers capable of high-viscosity measurements using self-excited oscillations is proposed and assessed both theoretically and experimentally. Such viscometers are well-known for their rapid response and miniaturization. Unlike conventional methods based on Q-value estimations obtained experimentally from the frequency response or resonance curve, we describe the use of self-excited oscillations in viscosity measurements using positive velocity feedback control without relying on the frequency response curve. Such measurements become possible even for high viscosities where the peak of the frequency response curve is ambiguous or does not exist, i.e., the Q-value cannot be estimated from such curves. Furthermore, the validity of the proposed method is experimentally tested using a prototype self-excited viscometer. Downsized oscillators such as micro- or nanoscale cantilevers can be self-excited following a straightforward application of the method. They are expected to enable not only localized monitoring of changes in high viscosity with time but also spatial high-viscosity measurements by the distributed arrangement of the devices.

Driving at Resonance Point of Multi-Degree-of-Freedom System by Decentralized Control

A control method has been developed to always excite a multi-degree-of-freedom system efficiently at a resonance frequency. When an excitation point corresponds to a vibration detection point in the multi-degree-of-freedom system, a phase lag at a resonance frequency and a phase lead at an anti-resonance frequency alternately appear in the vibration characteristics, and the phase lag becomes 90° at all the resonance frequencies. Therefore, if a controller that has a phase lag of 90° and a constant gain in a wide frequency range is used, self-excited vibration is generated at all the resonance frequencies. The self-excited vibration controller can be expressed as the sum of the positive velocity feedback control with a high gain in a high frequency domain and the integral control of the displacement with a high gain in a low frequency domain. A local feedback controller for each actuator consists of a self-excited vibration controller, a saturation element that limits excitation force, and a negative velocity feedback controller that provides damping. A driving at a resonance point system using many actuators with local feedback control, that is, decentralized control, is excellent in its adaptability to the environment, in its extendibility, and in its fault tolerance. In addition, the self-excited vibration mode can be freely switched on by changing the frequency of the sine wave that causes the self-excited vibration.

1B24 Driving at Resonance Point of Multi-Degree-of-Freedom System by Decentralized Control : Experiment Using Five Carts Connected in Series by Four Springs

We verified through experimentation on five carts connected in series by four springs that a control method for always efficiently exciting a multi-degree-of-freedom system at a resonance frequency. When an excitation point corresponds to a vibration detection point in a multi-degree-of-freedom system, a phase lag at a given resonance frequency and the phase lead at an anti-resonance frequency alternately appears in the vibration characteristics, and the phase lag is 90° at all resonance frequencies. Therefore, if a controller with a 90° phase lag and a constant gain in a wide frequency range is used, self-excited vibration is generated at all resonance frequencies. The local feedback controller for each actuator consists of a self-excited vibration controller that is the sum of the integral control of the displacement and the positive velocity feedback control, a saturation element that limits excitation force, and a negative velocity feedback controller that provides active damping. We used a four-degree-of-freedom system consisting of five carts and four springs in our experiment. Four voice coil motors controlled by the local feedback were used to generate self-excited vibration at all the resonance frequencies of a four-degree-of-freedom system. The self-excited vibration mode can be freely switched on by changing the frequency of the sine wave that is added as an electric disturbance. A system using many actuators with local feedback control, i.e., decentralized control, driven at a resonance point with a natural frequency is excellent in its adaptability to the environment, in its extendibility, and in its fault tolerance.

分散制御による多自由度振動系の共振点駆動 : 直列結合形ばね連結台車を用いた実験(機械力学,計測,自動制御)

We verified through experimentation on five carts connected in series by four springs a control method for always efficiently exciting a multi-degree-of-freedom system at a resonance frequency. When an excitation point corresponds to a vibration detection point in a multi-degree-of-freedom system, a phase lag at a resonance frequency and a phase lead at an anti-resonance frequency alternately appear in the vibration characteristics, and the phase lag is 90° at all resonance frequencies. Therefore, if a controller with a 90° phase lag and a constant gain in a wide frequency range is used, self-excited vibration is generated at all resonance frequencies. The local feedback controller for each actuator consists of a self-excited vibration controller that is the sum of the integral control of the displacement and the positive velocity feedback control, a saturation element that limits excitation force, and a negative velocity feedback controller that provides active damping. We used a four-degree-of-freedom system consisting of five carts and four springs in our experiment. Four voice coil motors controlled by the local feedback were used to generate self-excited vibration at all the resonance frequencies of a four-degree-of-freedom system. The self-excited vibration mode can be freely switched on by changing the frequency of the sine wave that is added as an electric disturbance. A system using many actuators with local feedback control, i.e., decentralized control, driven at a resonance frequency is excellent in its adaptability to the environment, in its extendibility, and in its fault tolerance.

Time-Delayed Positive Velocity Feedback Control Design for Active Control of Structures

In this paper we present and propose a design methodology that uses intentional time delays for the active control of structures. We use here positive velocity-feedback, time-delayed control and show that its performance is, in general, superior to the previously developed methodology of using time delayed, negative velocity-feedback control. A detailed study carried out in this paper of the nonsystem poles and their interaction with the system poles reveals the reasons for this. Analytical results related to performance and stability of the new method are presented. We apply the time delayed positive velocity feedback active control methodology to a multidegree-of-freedom system subjected to the S00E component of ground acceleration recorded during the El Centro 1940 earthquake. The excellent behavior in terms of stability, performance, and control efficiency that is demonstrated by our time-delayed control design as well as its facile implementation makes it attractive for earthquake hazard mitigation in a practical sense.