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

An experimental study of active control of wind-induced vibration of super-tall buildings

This thesis investigates how insects control movement using adaptive feedforward control and efference copies, and how these principles can be applied to robotic systems. A phenomenological control architecture—the fully-separable-degrees-of-freedom (FSDoF) controller—is developed to formalise efference copies in a control-theoretic context. The FSDoF architecture is used in simulation to examine control advantages of efference copy-based systems. Specifically, it enables sensors to remain within their operating range, thereby optimising sensitivity to external disturbances, and is particularly effective in systems with time delays and significant sensor noise. When combined with high-pass-filter-like sensors, the FSDoF controller also exhibits a unique robustness to changes in sensor gain and bandwidth. Furthermore, a method is introduced to design FSDoF controllers for multi-input multi-output (MIMO) systems with multiple, distinct time delays. This work formalises the efference copy hypothesis in insects from an engineering perspective, offering a functional explanation for their evolutionary advantages, and enabling the generation of experimentally testable hypotheses. One such hypothesis is that insect feedforward controllers adapt to changes in system dynamics. A series of free-flight experiments in Drosophila melanogaster supports this idea. Following unilateral wing damage, flies exhibited increased flight speeds in darkness compared to intact controls. When flying in light, with visual feedback, their speed was reduced to near-control levels. Altogether, the results indicate that the adaptation was not solely due to changes in mechanosensory feedback, but suggest adaptive feedforward control. Building on these insights, an implicit adaptive feedforward (IAFF) control strategy is proposed and implemented on a quadrotor platform. This controller uses adaptive sensitivity derivatives, so that it could, in theory, cope with an inversion of the system dynamics. IAFF control improved the reference tracking in a Parrot Mambo mini-drone within minutes of operation, starting from a randomised feedforward controller.

A multi-input multi-output adaptive feed-forward controller for vibration alleviation on a large blended wing body airliner

In this paper we focus on the adaptive control of structural acoustics using intelligent structures with embedded piezoelectric (PZT) patches and low cost digital signal processor systems. After a discussion on the adaptive feedforward control scheme, a hybrid adaptive control scheme is proposed, which takes advantage of both feedback control and adaptive feedforward control. The two schemes are realized on a low-cost, small volume, convenient and universal digital signal processing (DSP) board. A carbon fiber reinforced polymer plate with two embedded PZT patches is developed and used in two experiments. The first experiment is adaptive interior noise control using the intelligent plate, in which the adaptive feedforward control scheme is employed. Obvious noise reduction is obtained for constant frequency, swept frequency and varying amplitude harmonic disturbances. The second experiment is adaptive control of sound-induced vibration of the plate, where two embedded PZT patches are used as an actuator and a sensor, respectively, and the hybrid adaptive controller is applied. The full vibration reduction for various harmonic excitations is obtained, verifying the advantage of the hybrid adaptive control. It is demonstrated that active control of structural acoustics can be efficiently achieved by employing intelligent structures, advanced adaptive control schemes and the low-cost DSP board.

This paper focuses on a frequency-weighted hybrid adaptive control with application tosimultaneous precision positioning and vibration suppression of smart composite structures.Following the introduction of the structure and materials system of an active compositepanel (ACP) with a surface-mounted and two embedded piezoelectric ceramic patches, thesensor selection for the purpose of precision positioning or vibration control is discussed,and the function assignment of a laser displacement sensor as well as the embeddedpiezoelectric sensor is determined for the ACP. The frequency-weighted hybrid adaptivecontrol approach is then developed. The approach consists of an adaptive feedforwardposition controller for precision positioning, an adaptive feedforward vibrationcontroller for vibration suppression as well as an adaptive feedback controller for bothprecision positioning and vibration suppression. The frequency-weighted filtersintroduced in the approach realize the signal fusion of the two sensors. Finally,experiments are also performed for harmonic disturbances at the first two naturalfrequencies of the ACP and a random disturbance for both cases of with/without theadaptive feedforward vibration controller, demonstrating that the frequency-weightedhybrid adaptive control approach can provide satisfactory precision positioningand vibration suppression in both cases, and that better position accuracy canbe achieved if the adaptive feedforward vibration controller is also employed.

When prior knowledge of the plant controlled is available, feedforward control is preferred over feedback control for disturbance rejection.The stability characteristics of the system using feedforward control are the same as the original plant.Adaptive feedforward control design for gust loads alleviation of both a two degrees of freedom aerofoil with polynomial structural nonlinearity and a free flying flexible aircraft with large geometric wing deformations is investigated.Two dimensional thin aerofoil theory based on Theodorsen theory is used to perform aerodynamic analysis in the aerofoil aeroelastic model.The same aerodynamic model coupled with geometrically exact nonlinear beam is used to formulate the multi-disciplinary fluid-structure-flight framework for highly flexible aircraft.Gust loads analysis in terms of both discrete and continuous turbulence gusts are performed based on the aerofoil model and the free flying trim configuration of the highly flexible aircraft.Finite impulse response model is used to design an adaptive feedforward controller to alleviate the gust loads.Adaptive feedforward control shows good gust loads alleviation performance for both discrete and continuous gusts.Compared with adaptive feedback control, it exhibits a greater potential to reduce gust loads from the initial transient of the encounter.

The structure and performance requirements for active vibration isolation control systems motivate the use of adaptive control. This is especially true for spacecraft platforms subject to uncertainties inherent in on-orbit operation. This paper is an initial investigation into adaptive control strategies and algorithms that may have application to isolation on spacecraft platforms. Analysis of the algorithms, numerical simulation, and laboratory test data are used to evaluate adaptive feedforward control. Of particular interest are the performance characteristics and limitations of the filtered-x LMS (FXLMS) algorithm. The augmented error algorithm and combination feedback/feedforward control are two means investigated to extend the capabilities of FXLMS by desensitizing the algorithm to the specific dynamics of the plant. Several experiments were conducted on a laboratory testbed which serves as the prototype for a planned active vibration isolation flight demonstration.

A unique approach to adaptive feedforward control, namely the higher-harmonic time-averaged gradient descent algorithm (H-TAG), is presented. As opposed to the more common adaptive feedforward control method based on the filtered-x LMS algorithm, H-TAG does not require a measure of the control to error sensor transfer function for the system. Thus if the system dynamics change during the control process, H-TAG will simply adapt to the new optimal control configuration, rendering the approach model insensitive. Until now, work presented on the H-TAG algorithm has been limited to a single-input, single-output theoretical simulation. This paper describes the additional considerations involved in implementing the algorithm on an actual complex laboratory model (a de Havilland Dash 7 turbo-prop fuselage) that has multiple inputs and multiple outputs. Results from this preliminary experimental study suggest that the H-TAG algorithm is a viable alternative for adaptive feedforward control of systems with slowly time-varying parameters.

An Adaptive Feedforward Control Algorithm for Computer Control of Wastewater Neutralization

In this paper, high speed synchronization of multiple motion control axes under adaptive feedforward control is considered. The adaptive feedforward control system for one axis system consists of a proportional feedback controller and an adaptive feedforward controller. To synchronize the multiple motion control axes, the synchronizing controller, which responds to the tracking errors, is introduced. The structure of the synchronizing controller is investigated. The parameters of the adaptive feedforward controller are adjusted by the adaptation algorithm so that the tracking errors and the synchronization errors are removed. This results in the significant improvement of the tracking responses and the quick removal of the synchronization errors during transient as well as steady state. The synchronization for a four axes motion control system, of which parameters are significantly different, is investigated. Stability of the proposed synchronizing system is analyzed. Experimental results demonstrate the effectiveness of the proposed control scheme for synchronization.

This paper investigates the feasibility of adaptive control scheme for vibration suppression of flexible beam. The dynamic model of the flexible cantilever beam using finite element modeling is derived. Adaptive vibration controllers are good candidates for problems where parameters of a plant are unknown or there are uncertainties in a system. Parameters of adaptive controllers are adjusted on-line to achieve the best performance. Two adaptive vibration control schemes: adaptive feedforward control scheme using least mean square algorithm and model reference adaptive control algorithm are developed to suppress the vibration. Computer simulations are performed to verify the effectiveness of the proposed adaptive vibration control schemes and demonstrate their applications in vibration control.

Presents an approach to the design and real-time implementation of an adaptive controller for a robotic manipulator based on digital signal processors. The Texas Instruments DSP (TMS320C31) chips are used in implementing real-time adaptive control algorithms to provide enhanced motion control performance for robotic manipulators. In the proposed scheme, adaptation laws are derived from the direct model reference adaptive control principle based on the improved Lyapunov second method. The proposed adaptive controller consists of an adaptive feedforward and feedback controller and PI-type time-varying auxiliary control elements. The proposed control scheme is simple in structure, fast in computation, and suitable for real-time control. Moreover, this scheme does not require any accurate dynamic modeling nor values of manipulator parameters and payload. Performance of the proposed adaptive controller is illustrated by simulation and experimental results for an industrial robot with four joints in the joint space and Cartesian space.

Usage of frequency based error correction methods for repetitive disturbances becomes popular in data storage devices that use a rotating mechanical power plant. Two distinct disturbance cancellation methods, disturbance observer (DOB) and adaptive feed forward control (AFC) are the most popular approaches used for current drive servo integration. DOB reduces error using a predetermined function that is calculated thorough a complicated process. Generally the response to disturbance and initiation of control action of DOB is relatively fast even if the amount of error reduction is limited. Meanwhile the error elimination capability of AFC for the repetitive disturbance is normally better than DOB as it utilizes a Fourier coefficients updating feature that supports an enhanced fine adaptation of a certain frequency disturbance. Of course, AFC suffers for disturbances that have neighboring close frequencies due to the inherent fundamental frequency dependencies of AFC formulation. In the present work, an attempt for combining benefits of AFC and DOB is made. This might enables control action not only to generate fast response to disturbance but also perform an accurate error rejection. This feature also provides to the closed loop system a frequency selection for enabling a strategic selective error rejection. The proposed method named Hybrid Disturbance Observer (HDOB) is compared to the traditional AFC and DOB.

The least-mean squares (LMS) adaptive feedforward algorithm is used widely for vibration and noise cancellation. If reference signals become large enough to saturate that actuators, the filter coefficients in such algorithms can diverge. The leaky LMS method limits the controller effort by augmenting the objective function by a weighted control effort, and is known to attain good performance and avoid growth of filter coefficients for well-chosen weights. We propose an algorithm that seeks to directly minimize the mean-square cost in the presence of saturation. We derive the true stochastic gradient of the cost for systems with saturation with respect to the filter coefficients and obtain an adaptation rule very close to that of the filtered-x algorithm, but in the proposed algorithm, the reference filter is a time-varying modification of the secondary channel. In simulations of an active vibration isolation system with actuator limits subject to random ground vibration, the leaky LMS algorithm attains its best performance with actuation weights small enough to allow significant actuator saturation but large enough to prevent divergence. The proposed algorithm attains performance better that attained by the leaky LMS algorithm, and does not require the selection of weights.

This paper describes sound transmission reduction control through thin plate by using piezoelectric ceramic sensors and actuators, both of which are bonded on both surfaces of the plate. 2-DOF control system is introduced to reject the effect of bending vibration of the periodic component and continuously distributed component over the broad frequency range. The adaptive feedforward control is realized by using FIR filters and LMS system identification algorithm. The filtered epsilon with delay system is applied to cope with the non-minimum phase of the identified feedforward control systems. The internal model control is introduced to the feedback control system, which are constructed basically with the direct velocity feedback (DVFB) system. The internal model control was efficient to suppress the howling instability to occur frequently in case of high feedback gain. The substantial reduction of the sound radiation from the plate in the control experiment proves the effectiveness of the 2 DOF control system.