Enhanced delayed resonator for complete single- and multiple-frequency vibration suppression: A hybrid feedforward-feedback control approach

Delayed resonator for complete vibration suppression of primary structures with nonlinear stiffness

The delayed resonator (DR) is known for its ideal vibration suppression and simple control logic, but its operable frequency range is also known limited due to stability issues and practical hardware constraints. To extend the limited operable frequency range, we inject an additional nondelayed control term into the feedback loop of the classic DR such that the equivalent natural frequency of the DR can be real-time tuned, so the creation of DR with virtual natural frequency adjustment (DRV). Besides, we take the difference between the adjustable natural frequency of the DRV and the excitation frequency as a control parameter to further enhance the vibration suppression leading to optionally tuned parameters for a given excitation. For this, we start with the complete stability analyses of the DRV and the associated coupled system following independent and purely analytical approaches, and the obtained nonconservative stability maps reveal DRV's greatly extended operable frequency range. Given the optional tuned parameters, an optimization procedure aiming for a faster transient process and stronger robustness is proposed to determine the optimal parameter composition. Finally, three numerical case studies are prepared to demonstrate the benefits of the DRV compared with the classic DR. In addition to extending the operable frequency range of the classic DR, this work simplifies the stability analysis of the existing DR investigations and provides a guideline for the tuned control parameter design if they are optional.

To achieve proper operation of an online static uninterruptible power supply (UPS) system, feedforward and feedback (FF/FB) controls are introduced. Feedforward control is applied to reduce the low order harmonics in the output voltage due to the ripples included in the input DC voltage to the UPS inverter resulting from the controlled rectifier, while feedback control is applied mainly for stabilizing the output voltage. In this paper, a feedforward technique is selected that was found to give free ripple output, and two types of feedback techiques are compared and the most suitable one is considered. The paper gives the modeling and simulation results of the whole system, that compare the performance without and with FF/FB under different steady state and transient conditions.

The cerebellum has been hypothesized to form a crucial part of the speech motor control network. Evidence for this comes from patients with cerebellar damage, who exhibit a variety of speech deficits, as well as imaging studies showing cerebellar activation during speech production in healthy individuals. To date, the precise role of the cerebellum in speech motor control remains unclear, as it has been implicated in both anticipatory (feedforward) and reactive (feedback) control. Here, we assess both anticipatory and reactive aspects of speech motor control, comparing the performance of patients with cerebellar degeneration and matched controls. Experiment 1 tested feedforward control by examining speech adaptation across trials in response to a consistent perturbation of auditory feedback. Experiment 2 tested feedback control, examining online corrections in response to inconsistent perturbations of auditory feedback. Both male and female patients and controls were tested. The patients were impaired in adapting their feedforward control system relative to controls, exhibiting an attenuated anticipatory response to the perturbation. In contrast, the patients produced even larger compensatory responses than controls, suggesting an increased reliance on sensory feedback to guide speech articulation in this population. Together, these results suggest that the cerebellum is crucial for maintaining accurate feedforward control of speech, but relatively uninvolved in feedback control.SIGNIFICANCE STATEMENT Speech motor control is a complex activity that is thought to rely on both predictive, feedforward control as well as reactive, feedback control. While the cerebellum has been shown to be part of the speech motor control network, its functional contribution to feedback and feedforward control remains controversial. Here, we use real-time auditory perturbations of speech to show that patients with cerebellar degeneration are impaired in adapting feedforward control of speech but retain the ability to make online feedback corrections; indeed, the patients show an increased sensitivity to feedback. These results indicate that the cerebellum forms a crucial part of the feedforward control system for speech but is not essential for online, feedback control.

Feedforward (FF) control uses a priori knowledge about a given system and its disturbances to influence the system’s behavior in a pre-defined way. However, unlike feedback (FB) control, it does not adjust the control signal (or manipulated variable) in response to how the system actually reacts. In other words, FF control is proactive while FB control is reactive. Model-inversion-based FF (MIBFF) control is a specific type of FF control where the control variable is determined by inverting a model of the system to be controlled. It is very popular for its use in output tracking control problems, where the goal is to force the system’s output to follow a desired trajectory. Output tracking is critical in several different applications, e.g., in manufacturing, robotics, automotive, aerospace, and is typically achieved using a combination of FF and FB control. As motivating examples, consider MIBFF in ultra-precise wafer scanners used in photolithography (see Sidebar S1) and in desktop 3D printing (see Sidebar S2). As these motivating examples illustrate, non-minimum phase (NMP) zeros often arise in practical engineering applications due to non-collocated sensors and actuators, fast sampling, etc. MIBFF for systems with NMP zeros is arguably the most important (and certainly the most researched) issue related to MIBFF.

The Delayed Resonator (DR) is a recent active vibration absorption technique which uses time delayed position feedback to generate ideal resonance in a passive vibration absorber. This can also be achieved using proportional and feedback (PD) control. In this paper, these two techniques are compared analytically and experimentally. It is also shown that actuator dynamics must be considered in order to determine the control parameters correctly. A theoretical development is presented towards this purpose. Experimental results show that both techniques are equally effective in vibration absorption.

<div class="section abstract"><div class="htmlview paragraph">The parameters determining shift quality control in automatic transmissions are determined as part of the calibration of the transmission control. The resulting control system typically has three components: feedforward control, where the control output is determined before a gearshift; feedback control, where the control output is determined during the gearshift based on sensed feedback; and learning control (adaptation), where the feedforward or feedback controller parameters are modified after the current gearshift has ended and before the next similar gearshift begins. Gearshifts involving the same ratio change are referred to here as similar gearshifts, though such gearshifts may involve differences in other variables such as vehicle speed or engine torque. In most automatic transmissions, gearshifts are controlled by hydraulic clutches, and operating conditions for these clutches may vary widely, requiring a dedicated transmission controller involving significant calibration effort.</div><div class="htmlview paragraph">In the current work, novel model-based methods are used to accomplish feedforward control of gearshifts, involving offline calibration of fill and torque phase control parameters and learning control of the fill phase. Towards this end, a physics-based model of the oncoming clutch involved in an upshift of a production automatic transmission was developed and experimentally validated against test bench experiments for a wide variety of inputs and operating conditions. The resulting model is used to generate a feedforward controller, offline model-based calibration algorithm, and a learning controller that corrects for clutch under-fill and over-fill. The effectiveness of the resulting controller is validated by simulation studies using the experimentally validated transmission hydraulic system model, in conjunction with a powertrain model. In particular, it is demonstrated that the learning controller corrects for initial under- or over-fill error in two to three gearshifts. Convergence and robustness properties, and transient performance of the learning controller are also discussed.</div></div>

This paper presents a method for designing a controller that achieves the best positioning performance while maximizing the energy efficiency of a redundantly actuated hybrid feed drive. A two-degree-of-freedom controller, consisting of a feedforward (FF) controller for tracking and a feedback (FB) controller for regulation, is assumed. It is shown that the ideal FF controller, which achieves perfect tracking with maximum efficiency, is not always stable. Therefore, a method for designing a stable FF controller that achieves perfect tracking with near optimal efficiency is proposed. Furthermore, the optimal relationship between FB control inputs, which guarantees maximum efficiency for any specified regulation performance, is derived. Two approaches for using the derived optimal relationship to synthesize a FB controller that achieves the best positioning performance while maximizing efficiency are proposed. Simulations and machining experiments are conducted to demonstrate the effectiveness of the proposed energy-efficient FF and FB controller design methods. Significant improvements in energy efficiency (without sacrificing positioning performance) are reported.

To estimate the contributions of feedforward vs. feedback control systems in speech articulation, we analyzed the correspondence between initial and final kinematics in unperturbed tongue and jaw movements for consonant-vowel (CV) and vowel-consonant (VC) syllables. If movement extents and endpoints are highly predictable from early kinematic information, then the movements were most likely completed without substantial online corrections (feedforward control); if the correspondence between early kinematics and final amplitude or position is low, online adjustments may have altered the planned trajectory (feedback control) (Messier and Kalaska, 1999). Five adult speakers produced CV and VC syllables with high, mid, or low vowels while movements of the tongue and jaw were tracked electromagnetically. The correspondence between the kinematic parameters peak acceleration or peak velocity and movement extent as well as between the articulators' spatial coordinates at those kinematic landmarks and movement endpoint was examined both for movements across different target distances (i.e., across vowel height) and within target distances (i.e., within vowel height). Taken together, results suggest that jaw and tongue movements for these CV and VC syllables are mostly under feedforward control but with feedback-based contributions. One type of feedback-driven compensatory adjustment appears to regulate movement duration based on variation in peak acceleration. Results from a statistical model based on multiple regression are presented to illustrate how the relative strength of these feedback contributions can be estimated.

To meet stringent Euro-6 emission regulations, a lean NOx trap (LNT) catalyst should be considered to effectively abate NOx emissions. This LNT catalyst should be periodically regenerated without deteriorating driving quality and also satisfy emission constraints, such as CO, low particulate matter or smoke, and low O2 during the regeneration phase. As a means of reductant delivery, in-cylinder post fuel injection with a feedforward (FF) control has been applied due to its simple implementation in an engine management system (EMS). However, with this method, it is difficult to satisfy the driving quality and emission constraints during the transition to or out of the regeneration phase. To solve this problem, we propose a novel LNT regeneration control method using an indicated mean effective pressure (IMEP) and a combustion lambda feedback (FB) control combined with the FF control. For the precise FB control of the post injection timing, among the location of the second rate of heat release (ROHR) peak, the magnitude of the second ROHR peak, and IMEP, the IMEP was selected as a control parameter because of its lowest cyclic variation. In addition, the exhaust lambda control was applied for the accurate FB control of the post injection quantity. The proposed method was implemented in an in-house EMS. The performance in several engine tests indicated that the torque fluctuation was minimized and all emission constraints were effectively satisfied. Furthermore, this method was also robust with regard to the thermal disturbance.

Ball handling and dribbling are basics soccer techniques. Therefore, handling and dribbling mechanism becomes important component for MSL (Middle Size League) robot soccer. The implementation of active handling and dribbling systems aims to enable the robot to perform dribbling mechanism when maneuvering, while in idle position use handling mechanism. Feedforward and feedback applied as control method in active ball handling and dribbling system. Feedforward control method will give a response to the dribbler wheel based on the motion of robot movement against x , y , and θ axes. Whereas, Feedback control method applied fuzzy inference system by reading the displacement of the arm angle from sensor databased on angle reference of dribbler arm to keep the ball in an ideal position. Implementation geometric calculation for feedforward control toward x , y , and θ axes movement of the robot that it has resulted RMSE value for left motor is 5.75 and for right motor is 7.01. Fuzzy inference system method is used as a feedback control to manipulate the speed and direction of wheel’s rotation as a result ball remains in the ideal position. The value of arm angle displacement and the combination of the two-dribbler arms are used as input for fuzzy inference system. The results of this research show that the application of the combined feedforward and feedback control methods in active handling and dribbling systems can provide robot-dribbling capabilities. Consequently, the robot has a good ability in handling and dribbling mechanism.

This study proposed a combined predictive feedforward and feedback control strategy and used the predicted value as the reference value of the feedforward controller. In wind turbine with large changes in wind conditions, the pitch actuator had not changed in real time and the feedback control signal had the problem of hysteresis. The control strategy was the predictive feedforward controller combined with the feedback controller optimized by the distributed parallel firefly algorithm (DPFA). The variable pitch actuator changed pitch angle in advance to achieve the purpose of smooth power output of wind turbine. Finally, the algorithms and control strategies proposed in this article were applied to megawatt-level wind turbines and compared with traditional control strategies. The simulation results show that the predictive feedforward-feedback control strategy have a better control effect.

Nowadays, the demand for power electronics technology has increased due to the importance of its applications such as power inverters. The power inverter is required to modify the DC power from PV cells to AC power. One of the most common issues of on-grid PV systems is the high variations of the generated DC voltage. This will affect the stability of the generated AC voltage at the Point of Common Coupling (PCC) with the grid. This paper combines the Feed-Forward and Feedback (FFFB) controller in a novel way to reduce the variation of the PV cells DC voltage. This paper presents both mathematical and Simulink models of single-phase voltage source inverters VSI. Then, a case study of 15% disturbance of DC-generated voltage is considered. The static and dynamic behaviour of the single-phase H-bridge inverter is analysed under different loads. The new combination is used to reduce the effect of the disturbance on the performance of the system. Also, the proposed closed-loop controller (FFFB) can reduce the overshoot by 50% less than the feedback controller only. The settling time has been improved by 41%, 61% for RL and induction motor.

Control of manipulators during execution of tasks that require the end‐effector to come into contact with objects in its work environment represents an important class of control problem. Hybrid control, a concept which defines the architecture of a class of control laws has been proposed as a method with which to solve this control problem. One interpretation of the hybrid control method is within the framework of constrained motion control. Constrained motion occurs during contact by the manipulator end‐effector with rigid objects in the workplace, hence the motion of the manipulator is kinematically constrained. Papers have appeared in the robotics control literature addressing hybrid control within the constrained motion context which do not explicitly use the constrained dynamic formulation that correctly describes the dynamic behaviour of the manipulator. This article serves to link results from constrained motion control and the existing literature on the hybrid control method. In this article a formulation of the constrained manipulator dynamics is presented in which the hybrid control design is most naturally carried out. This formulation of the manipulator dynamics, previously proposed in the robotics literature, is such that the generalized force and position coordinates to be controlled are mutually orthogonal. Hence, the hybrid selection matrices, a key element of the hybrid control design philosophy, are implicit in this coordinate representation. A hybrid control design methodology is then formulated based on this development. Two hybrid control laws are proposed. For each hybrid control law, the global asymptotic stability is readily established due to the natural coordinate representation. One of these hybrid control laws, a constrained motion control law already proposed in the literature, is given to illustrate the equivalence of the hybrid control design and certain existing constrained motion control methods. Finally, a concrete example of a three‐degree‐of‐freedom robotic manipulator illustrates the hybrid design methodology proposed.

The present study reports on a preliminary experiment designed to experimentally verify the effectiveness of a newly developed rehabilitation support system using a torqueload wrist manipulandum. Evidence-based rehabilitation requires devices that can objectively and quantitatively evaluate motor function, yet conventional methods often rely on subjective assessments or limited clinical indicators. To overcome these limitations, we constructed a system capable of assessing two representative neural motor control strategies: feedback (FB) and feedforward (FF) control. In order to evaluate the feasibility and effectiveness of the proposed system, experimental trials were conducted with nine healthy participants. The device allows torque loads to be applied in arbitrary directions to wrist movements. Pursuit tasks were used to assess FB control, and step tasks to assess FF control. Participants performed both tasks under three leftward torque-load conditions ($0,0.9$, and 1.5 kgf.cm) simulating a resistive (pseudo-spastic) environment. Response time and positional error were analyzed as outcome measures. The results confirmed that the system could successfully differentiate neural control strategies. FB control showed delayed responses and increased positional errors, while FF control exhibited enhanced internal model formation under mild spasticity. This preliminary verification demonstrates that the proposed system can experimentally evaluate adaptive processes of FB and $F F$ control under different task environments. These findings support its potential as a platform for quantitative assessment and rehabilitation support. Future clinical studies are required to further validate the system and explore its contribution to functional recovery in stroke patients.