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The present article focuses on suppressing mode-coupling instability in frictional systems, which can cause unwanted vibrations such as squeal in braking systems. Mode-coupling instability occurs when two or more modes of a system approach each other. This article proposes the use of resonant velocity feedback control to eliminate friction-induced oscillations generated by mode-coupling instability. A two degree-of-freedom linear model is used to capture the instability due to friction-induced mode coupling. The efficacy of the control is demonstrated through linear stability analysis, and by optimizing control parameters using pole crossover method to minimize the transient time of the response. The robustness analysis demonstrates the ability of the control to effectively mitigate the instability even under parametric perturbations. The controlled system is simulated in MATLAB Simulink to validate analytical results. The effects of time delay, which is commonly present in feedback systems, are also investigated. Finally, the effectiveness of the control is studied in the presence of nonlinearity in the system. The nonlinear dynamics are analyzed by creating bifurcation diagrams with different bifurcation parameters. [ABSTRACT FROM AUTHOR]

In order to reduce the influence of environment on the flow rate of lubricating oil and improve the accuracy of dripping oil, this paper developed an optimized proportional integral differential (PID) precision lubrication controller for railway switch locking hooks. The system models the temperature-dependent flow dynamics of biodegradable lubricants. An improved PID algorithm is proposed, which uses velocity feedback to enhance setpoint tracking and disturbance suppression. The simulation results show that the flow control accuracy is improved by 0.8% compared with the traditional PID method. Field tests over a temperature fluctuation range of –3 °C to 35 °C validate the effectiveness and robustness of the method for maintaining a constant drop rate. This research enables adaptive, environmentally friendly lubrication to reduce friction and ensure the operability of railway switch.

Vibration isolation is a crucial technology in precision manufacturing. With the rapid development of smart sensors, smart actuators, and microprocessors, active vibration isolation has emerged as a viable approach to improve the performance of manufacturing equipment. In integrated skyhook active vibration isolation, the cut-off frequency limits the controller gain. Base on the repeated poles technique, this paper reveals the simple analytical forms of the optimal cut-off frequency and controller gain of the integrated skyhook active isolation. The analytical formula is useful in the design of active isolation. Numerical calculations are performed to show the good performance of the optimal design. An experiment is carried out to show the existence of the optimal controller gain.

The control of decentralized velocity feedback on curved aircraft plates under turbulent boundary layer excitations is numerically investigated in this paper. Sixteen active control units are set on the plate to reduce the vibration and sound radiation of the plate. The computational results from the two methods are compared to verify the accuracy of the numerical model. The plate kinetic energy and the radiated sound power under turbulent boundary layer and control unit excitations are analyzed. The influences of control unit distribution, plate thickness and curvature on radiated sound are discussed. Unlike a flat plate, the control of the lower-order high radiation modes of a curved plate under TBL excitations is critical since these modes predominate the sound radiations. The control of these modes, however, is sensitive to the ratio of the stiffness associated with the membrane tensions to the stiffness associated with the bending forces. This ratio implies that the plate curvature and the thickness play an important role in the control effect. When the plate is thinner and the radius is smaller, the control is less effective.

The control of decentralized velocity feedback on curved aircraft plates under turbulent boundary layer excitations is numerically investigated in this paper. Sixteen active control units are set on the plate to reduce the vibration and sound radiation of the plate. The computational results from the two methods are compared to verify the accuracy of the numerical model. The plate kinetic energy and the radiated sound power under turbulent boundary layer and control unit excitations are analyzed. The influences of control unit distribution, plate thickness and curvature on radiated sound are discussed. Unlike a flat plate, the control of the lower-order high radiation modes of a curved plate under TBL excitations is critical since these modes predominate the sound radiations. The control of these modes, however, is sensitive to the ratio of the stiffness associated with the membrane tensions to the stiffness associated with the bending forces. This ratio implies that the plate curvature and the thickness play an important role in the control effect. When the plate is thinner and the radius is smaller, the control is less effective. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results of a new proof mass actuator for the implementation of velocity feedback control loops to reduce the flexural vibration of a thin plate structure. Classical proof mass actuators are formed by coil–magnet linear motors. These actuators can generate constant force at frequencies above the fundamental resonance frequency of the spring–magnet system, which can be used to efficiently implement point velocity feedback control loops. However, the dynamics of the spring–magnet system limit the stability and control performance of the loops when the actuators are exposed to shocks. The proof mass actuator investigated in this paper includes an additional flywheel element that improves the stability of the velocity feedback loop both by increasing the feedback gain margin and by reducing the fundamental resonance frequency of the actuator. This paper is focused on the stability and control performance of decentralized velocity feedback control loop [ABSTRACT FROM AUTHOR]

This paper presents the experimental results of a new proof mass actuator for the implementation of velocity feedback control loops to reduce the flexural vibration of a thin plate structure. Classical proof mass actuators are formed by coil–magnet linear motors. These actuators can generate constant force at frequencies above the fundamental resonance frequency of the spring–magnet system, which can be used to efficiently implement point velocity feedback control loops. However, the dynamics of the spring–magnet system limit the stability and control performance of the loops when the actuators are exposed to shocks. The proof mass actuator investigated in this paper includes an additional flywheel element that improves the stability of the velocity feedback loop both by increasing the feedback gain margin and by reducing the fundamental resonance frequency of the actuator. This paper is focused on the stability and control performance of decentralized velocity feedback control loops.

In this paper, an improved car-following model is raised by taking the preceding vehicle's velocity feedback and desired inter-vehicle distance into account. The asymptotic and local stability criteria are obtained via control theory method to analyze the effect of the preceding vehicle's velocity feedback and desired inter-vehicle distance on dynamic characteristics of traffic flow. In addition, numerical simulations are constructed on vehicle starting and traffic flow evolution processes, which show that the proposed car-following model can better present the characteristics of traffic flow. The preceding vehicle's velocity feedback and desired inter-vehicle distance play a vital role on vehicle starting process and the stability of traffic flow. [ABSTRACT FROM AUTHOR]

We estimated the effectiveness of using velocity feedback to regulate resistance training load on changes in muscle strength, power, and linear sprint speed in apparently healthy participants. Academic and grey literature databases were systematically searched to identify randomised trials that compared a velocity-based training intervention to a 'traditional' resistance training intervention that did not use velocity feedback. Standardised mean differences (SMDs) were pooled using a random effects model. Risk of bias was assessed with the Risk of Bias 2 tool and the quality of evidence was evaluated using the GRADE approach. Four trials met the eligibility criteria, comprising 27 effect estimates and 88 participants. The main analyses showed trivial differences and imprecise interval estimates for effects on muscle strength (SMD 0.06, 95% CI −0.51–0.63; I2 = 42.9%; 10 effects from 4 studies; low-quality evidence), power (SMD 0.11, 95% CI −0.28–0.49; I2 = 13.5%; 10 effects from 3 studies; low-quality evidence), and sprint speed (SMD −0.10, 95% CI −0.72–0.53; I2 = 30.0%; 7 effects from 2 studies; very low-quality evidence). The results were robust to various sensitivity analyses. In conclusion, there is currently no evidence that VBT and traditional resistance training methods lead to different alterations in muscle strength, power, or linear sprint speed. [ABSTRACT FROM AUTHOR]

In this article, vibration analysis of a beam-fluid coupled system was performed and then, employing magnetostrictive layers, vibration amplitude of the cantilever beam was controlled according to a closed-loop velocity proportional feedback control (CLVPFC) approach. The beam was composed of functionally graded carbon nanotube-reinforced sandwich composite (FGCNTRC) materials. The fluid was assumed to be incompressible, inviscid, and irrotational. The equation of motion of coupled fluid-structure system was solved by combining two analytical and Galerkin methods. To verify the stability and accuracy of solution procedure, convergence and comparison studies were presented. The effects of various parameters such as fluid depth, length of the beam, and distribution type of the carbon nanotubes (CNTs) on controlled and uncontrolled vibration amplitudes were investigated. [ABSTRACT FROM AUTHOR]

This study concerns the out-of-plane motion of a vertically disposed string with one end fixed and the other subjected to a harmonic excitation. Excited in its primary resonance, the string can vibrate in the direction orthogonal to the excitation direction through nonlinear coupling effects and has out-of-plane motion. To suppress this out-of-plane motion, we propose a boundary control method that modifies the boundary condition of the fixed upper end, i.e., we move the fixed upper end in the direction orthogonal to the external excitation. The unstable range for trivial steady state motion in this direction, which exists in the neighborhood of the primary resonance condition, changes to a stable range under suitable feedback gain. The out-of-plane motion is then suppressed for any excitation frequency. Experiments conducted using a simple apparatus confirmed the validity of the proposed method adopting boundary control. [ABSTRACT FROM AUTHOR]

The objective of this study is to increase the efficiency of an initial passive Tuned Mass Damper (TMD) by adding an active control unit. A critical issue in many engineering domains is the design of fail-safe active systems. The proposed hybrid system aims to address this issue and realizes the said objective. It emulates the behavior of a skyhook damper parallel to a passive TMD. Skyhook dampers acts like viscous dampers connected to the ground, reducing the vibration amplitudes without any overshoot. It can be difficult to design a specific control law to obtain a desired dynamical behavior. The paper presents two ways to understand and design the hyperstable control law for Hybrid Mass Damper (HMD) (also called Active TMD), using the power flow formulation or the mechanical impedance analysis. These approaches are illustrated through the synthesis of this hybrid device and the emulation of the Skyhook damper. It is shown that a well-designed control law for this kind of system may result in high damping performance, ensuring stability and a fail-safe behavior. In addition, the amplitude of the primary system's response is reduced over the entire frequency range which is not the case for the usual active or hybrid systems. Robustness is analyzed and compared to that of the classical active mass damper, and an experimental set up validates the proposed hybrid system. [ABSTRACT FROM AUTHOR]

In an active vibration isolation system using velocity feedback, the phase-lead due to high-pass filter and the phase-lag due to time delay limit the controller gain. This paper extends and applies a simple frequency range selector to increase the critical control gain. The selector uses the isolated mass's acceleration, velocity, and displacement and is tuned by two knobs. Our proposed approach has simple static switching law, suppresses both low and high frequency control, and does not add additional phase-lead or phase-lag. A simple expression of the effective gain is presented to give insight into the influence of two tuning knobs. Numerical simulations and a simple experiment are performed to illustrate the controller's effectiveness under harmonic and random disturbances. [ABSTRACT FROM AUTHOR]

This study proposes a novel model-free robot manipulator joint position and velocity tracking controller with a simple structure for controlling a robotic manipulator with human-like reaching motion according to human movement characteristics. The proposed design guarantees the responses of the tracking error within preset bounds using velocity feedback. A structurally and computationally natural logarithmic controller is designed to achieve joint position and velocity tracking of a desired trajectory of a reaching motion profile with prescribed performance (PP) bounds. Simulations of a three-degree-of-freedom spatial manipulator with the PP controller confirm the conclusions even in case of typical input disturbances. Results show that the PP controller outperforms the traditional position and derivative (PD) trajectory tracking controller without requiring excessive control effort. The proposed controller that uses sole velocity feedback achieves the control objective with bell-shaped joint velocity profiles and joint consistency. Thus, the proposed controller outperforms the traditional PD trajectory tracking controller that uses position and velocity feedback with comparable control effort. The experiment with a KUKA robot manipulator demonstrates that the control algorithm of sole velocity feedback can be used to achieve smooth reaching movements within a short travelling time of less than 1 s. The movements are characterised by bell-shaped joint velocity profiles and joint position consistency similar to human movements. [ABSTRACT FROM AUTHOR]

Highlights • Tuning of velocity feedback control units through power absorption maximisation. • Experimental measure of the power flow in each control unit. • Numerical validation of the experimental results with a mobility/impedance model. • General methodology to assess performance with respect to control effort. Abstract This paper discusses the tuning of multiple decentralised velocity feedback units for broadband vibration control on a plate using inertial actuators. An analysis of the performance is presented in terms of maximising the mechanical power absorbed and of the control effort, defined by the electrical power in the control units, and the results are validated numerically. Two inertial actuators are mounted on an experimental plate, and driven with control currents proportional to the measured local velocities of the plate, collocated with the actuators. Tuning is compared by using either the measurement of kinetic energy of the plate, or the mechanical power absorbed by the control units from the plate. It is found that the mechanical power absorbed can be used as a local cost function to tune the control units, as an alternative to the kinetic energy, not only when reactive actuators are used, but also when inertial actuators are in use. In this way, the tuning process is greatly simplified, since the mechanical power absorbed can be measured directly from the feedback velocity signal and a knowledge of the actuators dynamics, without further information on the plate dynamics. The optimal gain for each unit is found to be reasonably independent of the gain implemented on the other unit. This implies that the system is robust against failure of a unit, since the other would still be optimally tuned. However, this tuning process depends on many factors, such as the type, position and number of control units implemented, and a comparison between different active control solutions, with respect to the optimal feedback gains only is not practical. For this reason, the measure of the electrical power, required by the control system, is suggested as a direct estimation of the control effort. To give an example of the proposed approach, the performance of the two control units is compared with the case in which only one unit at the time is active. The two-channel architecture is found not only to outperform the single-channel one in terms of vibration reduction, but also in terms of consumed electrical power. When the two channels are active, more than 8 dB broadband reduction is measured, and the consumed electrical power is found to be similar to the one consumed when only one unit is operating, which is optimally tuned. [ABSTRACT FROM AUTHOR]

The paper presents a new dual transducer and its associated control law. It aims to increase the efficiency of a traditional passive damped electromagnetic resonator by controlling its mass response actively. The design aspects of the so-called Dual-Loop Controller (DLC) for Hybrid Mass Damper (HMD) are presented and discussed. The control law attempts to modify a Tuned Mass Damper (TMD) to use it as an Active Mass Damper (AMD), with the objective of combining the best of the two technologies by actively increasing the performance of the passive device. Based on an optimally tuned passive device, the resulting system is fail-safe. The conception of the new dual transducer used as an HMD, designed specifically for this control law, is detailed. The hybrid device is experimentally validated both on a laboratory setup and on a real helicopter. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an active control method for reducing the lateral vibration transmission in a shaft-hull coupled system of submerged vehicles under the excitation of propeller forces. In this method, a 6-DOF (degree of freedom) active stern support and the local velocity feedback control strategy are employed to suppress vibration transmission from the shaft to the hull. The dynamic model of the shaft-hull system embedded with the active stern support is established with the FRF (frequency response function)-based synthesis method and the FEM/BEM (finite element method/boundary element method). The six-channel local velocity feedback control strategy is employed to suppress vibrations of the strut-hull interface. Numerical results indicate that a noticeable attenuation of vibration and sound radiation can be achieved by the active stern support. In addition, the combination control at the stern support and the thrust bearing is able to obtain better attenuation at some critical frequencies. Suppression of the mean square velocity and radiated sound power of the hull surface are observed. Highlights • A novel active control method is proposed to suppress the lateral vibration transmission of the shaft-hull system. • A FRFSM/FEM/BEM method is adopted to analyze vibration characteristics under control. • A numerical implementation of the dynamic model validates the control performance. • A significant attenuation is obtained through the active stern support. • A combination control is able to achieve better attenuations of vibration and sound radiation. [ABSTRACT FROM AUTHOR]

Abstract A variation of direct velocity feedback, often referred to as skyhook damping, is discussed in this paper. Skyhook damping cannot be regarded as collocated control method since only the action force component is collocated with the velocity sensor mounted onto the receiving part of the structure. The reaction control force component reacting off the source part of the structure does not have a collocated sensor. Depending on the characteristics of the passive structure under control, the feedback loop may be quite insensitive to the effects produced by the non-collocated reaction control force component, and maintain stability properties that are otherwise characteristic only for collocated control. Moreover, there exist additional effects related to the response of structures activated by the application of skyhook damping. It is shown in this paper that the structure subjected to such active control, although exhibiting stable response and linear input-output relationships, no longer complies with the reciprocity principle. The absence of reciprocity is interesting given the recent efforts in developing metamaterial cloaks, where one of the critical issues is how to design material structures or systems that demonstrate non-reciprocal behaviour. [ABSTRACT FROM AUTHOR]

Abstract The present paper is concerned with active vibration control of functionally graded piezoelectric material (FGPM) plate using the piezoelectric material component as actuator. Using the classical laminated plate theory, the equation of motion for the FGPM plate is deduced based on Hamilton's principle and Rayleigh-Ritz method. A velocity feedback control method is used to obtain an effective active damping in the vibration control. The influences of distribution type, volume fraction index and total volume fraction of piezoelectric material on the vibration control of FGPM plate are investigated. The calculation results show that the vibration control result is strongly affected by the distribution of piezoelectric materials in FGPM plate. It is also found that the total volume fraction, especially the volume fraction index play an important role in the vibration control. Furthermore, under the non-uniform electric field the effect of external voltage position on active vibration control is studied. The results show that one can obtain an excellent control effect by optimizing the structure of FGPM plate and the position of external control voltage. [ABSTRACT FROM AUTHOR]

• Dynamics inversion algorithms yield a very accurate force tracking by the actuator. • These algorithms are capable of compensating actuator-structure interaction. • Application to classical vibration control techniques enhances their performance. • Dynamics inversion may be applied to any force-based vibration control approach. • Practical guidelines are given for similar implementations. It is common that excessive vibrations problems arise in modern slender, low-damping, lightweight structures such as footbridges or long-span floors subjected to human actions. The integration of inertial vibration controllers has been extensively used to mitigate the problems associated with vibration serviceability of such structures. Among them, the active vibration absorber constitutes the most sophisticated and effective alternative. Nonetheless, the inherent dynamics of the actuators used in the practical implementations of these systems may negatively affect their performance, compromising the overall system stability and performance. In this work, the practical application of dynamics inversion techniques to the force control of electrodynamic proof-mass actuators employed as active vibration absorption systems in lightweight structures subjected to human-induced vibrations is presented. The main idea behind the dynamics inversion approach is to find an approximate inverse of the actuator system which, upon implementation on a real-time controller, approximately cancels out actuator dynamics leading to an improved force tracking, with the subsequent enhancement in the performance of any force-based vibration control algorithm. The dynamics inversion has been applied to the classical direct velocity feedback approach, leading to a novel vibration control algorithm denominated velocity feedback with dynamics inversion. Additionally, the stability of the suggested method has been studied and practical guidelines, including a step-by-step design procedure, have been provided for researchers willing to apply the proposed algorithm. The goodness of the suggested method has been assessed by means of a tests campaign carried over an existing glass fiber reinforced polymer footbridge, which fulfills the static requirements at Serviceability and Ultimate Limit States, but exhibits excessive vibrations when its first resonance frequency is excited. Two types of tests have been performed: a walking load and a vandal bouncing excitation exerted at the midspan of the footbridge. In both cases, the experimental results show that the new procedure outperforms the classical velocity feedback approach thanks to the enhanced force tracking, leading to a remarkable reduction in the vibrations experimented by the structure under study. [ABSTRACT FROM AUTHOR]

A simple control law, dedicated to improving the performance and stability of hybrid mass dampers, is investigated. The resulting hybrid device is based on decentralized velocity feedback techniques. Two poles and two zeros are added to the initial control law, in order to interact with the dynamics of the structure and the actuator. The interest of these interactions is to change the poles of the closed loop system so as to make the controlled system hyperstable. The margins of gain and phase are therefore infinite. Consequently, the proposed hybrid system controller is fail-safe but also unconditionally stable in theory. Experimentation, using a tuned voice coil actuator, illustrates the performance and robustness of this hybrid control device. [ABSTRACT FROM AUTHOR]

In this paper, three controllers are investigated for active vibration control of a pedestrian walkway structure. They comprise direct velocity feedback, observer-based and independent modal space controllers that are implemented in single-input single-output (SISO), multi-SISO and multiple-input multiple-output (MIMO) configurations. The objective of the SISO controller schemes is to compare vibration mitigation performances arising from global control versus selective control of structural resonant frequencies in a given frequency bandwidth. The objectives set out for the multi-SISO and MIMO controllers are to realize global control within the same frequency bandwidth considered in the SISO studies. A novel aspect of these latter studies is the independent control of selected resonant frequencies at different locations on the structure with the aim of imposing global control.Vibration mitigation performances are evaluated using frequency response function measurements and uncontrolled and controlled responses to a synthesized walking excitation force. In the SISO studies, selective control of specific resonant frequencies has a slight degradation in the global vibration mitigation performance, although it reflects better performance around the target frequencies. For the multi-SISO and MIMO controller studies, the selective control of the two lowest and dominant frequencies of the structure at two different locations still offers comparative vibration mitigation performances with the controllers considered as global in the sense that they target both structural frequencies at both locations. Attenuations of between 10 and 35 dB are achieved. [ABSTRACT FROM AUTHOR]

A mass measurement method in viscous environments using self-excited oscillation is proposed theoretically and experimentally. The utilization of the natural frequency shift in a resonator has attracted many researchers due to the high sensitivity. Small mass measurement with the order of fg and ag has been reported. In the conventional methods, the natural frequency shift is detected from the shift of the excitation frequency at which the frequency response curve takes the peak value. However, it is not applicable to the measurement in high viscous environments, i.e., the observation of the chemical reaction and the mass sensing for biological samples because the peak is ambiguous or does not exist. In this research, as a mass measurement method applicable in viscous environments, we propose the utilization of self-excited oscillation to measure the shift of the natural frequency caused by an sample added to the resonator. The resonator is actuated by positive velocity linear feedback. Self-excited oscillation occurs when the linear feedback gain exceeds a critical value depending on the viscosity in measurement environments. Also, by applying the nonlinear feedback the divergence of the self-excited oscillation is suppressed and the response amplitude is kept constant. The self-excited resonator vibrates at the natural frequency regardless of the viscosity in measurement environments because the velocity feedback compensates for the viscous effect. Then, not relying on a frequency response curve, the method using natural frequency shift becomes applicable even in high viscous environments. We fabricated a theoretically proposed self-excited mass sensor and conducted mass measurements experimentally in air, in water, and in a liquid with 1.17 x 10 4 mPa . s viscosity. As a result, the mass of 0.0091 kg was detected in the respective viscous environments. The ratio of the additional mass to the mass of the sensor is 0.59 %. [ABSTRACT FROM AUTHOR]

This paper presents four new proof mass actuators to be used in velocity feedback control systems for the control of vibrations of machines and flexible structures. A classical proof mass actuator is formed by a coil–magnet linear motor, with either the magnet or the armature-coil proof mass suspended on soft springs. This arrangement produces a net force effect at frequencies above the fundamental resonance frequency of the springs–proof mass system. Thus, it can be used to implement point velocity feedback loops, although the dynamic response and static deflection of the springs–proof mass system poses some stability and control performance limitations. The four proof mass actuators presented in this study include a flywheel element, which is used to augment the inertia effect of the suspended proof mass. The paper shows that the flywheel element modifies both the dynamic response and static deflection of the springs–proof mass system in such a way as the stability and control performance of velocity feedback loops using these actuators are significantly improved. [ABSTRACT FROM AUTHOR]

In this paper, a self-sensing model of an electromagnetic vibrator is analyzed to pick up linear velocity directly without any extra sensors. A feedback control system is then established based on the self-sensed velocity. As a result, the bandwidth of the constant-velocity segment of the vibrator can be expanded and the total harmonic distortion (THD) of the output waveform is decreased in the low-frequency range. The influence of different parameters in the feedback control system on the THDs is experimentally analyzed. Comparing with the conventional feedback control system with an extra displacement sensor, the proposed control system is more powerful in reducing the THDs of acceleration waveform to be lower than 1% at the frequencies from 0.1 to 10 Hz, but without any other feedback sensors. [ABSTRACT FROM PUBLISHER]

Transient response such as ringing in a control system can be reduced or removed by velocity feedback. It is a useful control technique that should be covered in the relevant engineering laboratory courses. We developed velocity feedback experiments using two different low cost technologies, viz., operational amplifiers and microcontrollers. These experiments can be easily integrated into laboratory courses on feedback control systems or microcontroller applications. The intent of developing these experiments was to illustrate the ringing problem and to offer effective, low cost solutions for removing such problem. In this paper the pedagogical approach for these velocity feedback experiments was described. The advantages and disadvantages of the two different implementation of velocity feedback were discussed also. [ABSTRACT FROM AUTHOR]