Practical Implementation Issues for Active Control of Large Flexible Structures

1989 ◽  
Vol 111 (3) ◽  
pp. 283-289 ◽  
Author(s):  
D. C. Zimmerman ◽  
H. H. Cudney
Keyword(s):  
Active Control ◽  
Control Strategies ◽  
Flexible Structures ◽  
Practical Implementation ◽  
Control Law ◽  
Actuator Dynamics ◽  
Analog To Digital ◽  
Digital Implementation ◽  
Digital To Analog Converters ◽  
And Performance

Most active control strategies, whether designed in the discrete or continuous domain, will most likely be implemented using a digital control system. Therefore, it is important to study the effects of digital implementation on the desired control law. In this work, the effect of quantization due to the finite wordlength of microprocessors, analog-to-digital, and digital-to-analog converters, on the desired control law is investigated. Additionally, the practical effect of actuator dynamics on the stability and performance of the control law is addressed. Finally, an active control experiment is reported on which takes into account and demonstrates some of these practical considerations.

Robust vibration control of flexible panel: modeling and simulation

2017 ◽  
Vol 14 (5) ◽  
pp. 433-442
Author(s):  
Aalya Banu ◽  
Asan G.A. Muthalif
Keyword(s):  
Robust Control ◽  
Vibration Control ◽  
Controller Design ◽  
Control Strategies ◽  
Active Vibration Control ◽  
Flexible Structures ◽  
Parametric Uncertainty ◽  
Design Algorithm ◽  
Content Type ◽  
And Performance

Purpose This paper aims to develop a robust controller to control vibration of a thin plate attached with two piezoelectric patches in the presence of uncertainties in the mass of the plate. The main goal of this study is to tackle dynamic perturbation that could lead to modelling error in flexible structures. The controller is designed to suppress first and second modal vibrations. Design/methodology/approach Out of various robust control strategies, μ-synthesis controller design algorithm has been used for active vibration control of a simply supported thin place excited and actuated using two piezoelectric patches. Parametric uncertainty in the system is taken into account so that the robust system will be achieved by maximizing the complex stability radius of the closed-loop system. Effectiveness of the designed controller is validated through robust stability and performance analysis. Findings Results obtained from numerical simulation indicate that implementation of the designed controller can effectively suppress the vibration of the system at the first and second modal frequencies by 98.5 and 88.4 per cent, respectively, despite the presence of structural uncertainties. The designed controller has also shown satisfactory results in terms of robustness and performance. Originality/value Although vibration control in designing any structural system has been an active topic for decades, Ordinary fixed controllers designed based on nominal parameters do not take into account the uncertainties present in and around the system and hence lose their effectiveness when subjected to uncertainties. This paper fulfills an identified need to design a robust control system that accommodates uncertainties.

An Active Control Methodology to Improve Pulsatile Turbocharger Operating Conditions and Performance

2020 ◽  
Author(s):  
Yue Song ◽  
Shuiting Ding ◽  
Zheng Xu ◽  
Farong Du ◽  
Yu Zhou
Keyword(s):  
Active Control ◽  
Control Strategies ◽  
High Energy ◽  
Operating Conditions ◽  
Compressed Air ◽  
Turbine Inlet ◽  
Surge Margin ◽  
Turbocharging System ◽  
And Performance ◽  
Control Methodology

Abstract As a critical component of an Internal Combustion Engine (ICE), a turbocharger suffers highly pulsatile airflow from the exhaust pipe, which determines the turbocharger performance is very different from that under steady and quasi-steady conditions. Faced with the theoretical and computational challenges associated with the optimization of the inlet and outlet conditions of the turbocharger, this paper presents an active control methodology (ACM) to improve turbocharger operating conditions and performance based on the redistribution of air mass flow and fuel flow. Considering the poor-efficiency of constant pressure turbocharging system and high structural-dependent pulse turbocharging system, the ACM proposes 3 essential steps: extract partial compressed air from the compressor outlet, then heat the compressed air with the appropriate amount of fuel in a burner and finally supply the high-pressure and high-temperature gas to the turbine inlet. These three control steps are executed in every cycle of the engine operating period, which can achieve cycle-level active control for turbine inlet compressor outlet conditions and finally achieve the purpose of overall performance amelioration for turbocharger and engine. In this paper, a two-cylinders two-stroke turbocharged diesel engine with this active control system (ACS) is modeled using 1-D modeling software to validate the effectiveness of the methodology. System performance simulations are conducted with exemplifications of control strategies and 5 different extraction pipe diameters in the 1-D simulation model. Results show that 7mm is the optimal pipe size for the ACS corresponding to the adapted control strategies, which is supported by the 62.5% wider surge margin of the compressor and better instantaneous performance of the turbine. The presented ACM combines the features of high energy utilization for pulse exhaust and stable operating conditions for the turbocharger, which can achieve a wider surge margin and better engine performance. This paper provides an initial and rather unique insight for designing and optimizing the high-performance turbocharging system for engines.

A Novel Semi-Active Multi-Modal Vibration Control Law for a Piezoceramic Actuator

2003 ◽  
Vol 125 (2) ◽  
pp. 214-222 ◽  
Author(s):  
Lawrence R. Corr ◽  
William W. Clark
Keyword(s):  
Vibration Control ◽  
Flexible Structures ◽  
Experimental Tests ◽  
Control Technique ◽  
Practical Implementation ◽  
Control Law ◽  
Energy Rate ◽  
Piezoceramic Actuator ◽  
Control Scheme ◽  
Modal Vibration

In this paper, a novel semi-active energy rate multi-modal vibration control technique is developed for a piezoceramic actuator coupled to a switching resistor/inductor shunt. The technique works by briefly connecting a resistor/inductor shunt to a piezoceramic actuator in order to apply the necessary signed charge to allow energy dissipation. The switch timing is determined by a control scheme that observes the rate of energy change in controlled modes. The control scheme is developed in the paper, and is simplified to enable practical implementation. This new multi-modal control law is applied to both a simple numerical and an experimental test structure. The results from the numerical and experimental tests show that the energy rate multi-mode control law is able to dissipate energy from one, two and three modes of the flexible structures using a single actuator.

Active Control of Flexible Structures Submitted to Incompressible Flows

2002 ◽  
Author(s):  
C. C. Machado ◽  
A. L. De Bortoli ◽  
S. C. P. Gomes
Keyword(s):  
Incompressible Flows ◽  
Flexible Structures ◽  
Pole Placement ◽  
Flexible Structure ◽  
Control Law ◽  
Flow Induced Vibration ◽  
Robust Controller ◽  
Numerical Tests ◽  
Noise Rejection ◽  
And Performance

This work presents a survey on the control law development to actively attenuate the vibrations of a flexible structure submitted to fluid flow. Firstly, a robust controller with LQG/LTR approach was developed. Numerical tests were carried out being robustness characteristics to flow induced vibration and to noise rejection verified, for the case of equal nominal and real plants. The same robustness was not verified, when parametric variations were introduced. Therefore, another controller, based on regulator and filter pole placement approach, was developed where the direct loop obeys stability and performance robustness criterions, allowing to obtain good numerical results, even in the presence of significant parametric variations.

Effects of control strategy on the activation of unwanted intrusive thoughts

2020 ◽  
Author(s):  
Sicong Liu ◽  
Jonathan Folstein ◽  
Lawrence Gregory Appelbaum ◽  
Gershon Tenenbaum
Keyword(s):  
Control Strategies ◽  
Working Memory Capacity ◽  
Intrusive Thoughts ◽  
Control Process ◽  
Event Related Potentials ◽  
Human Beings ◽  
Opposite Pattern ◽  
Thought Control ◽  
Related Potentials ◽  
And Performance

Although the unwanted intrusive thoughts (UITs) exist widely in human beings and show similar characteristics between clinical and nonclinical forms, its control process remains unclear. Thoughts of choking under pressure, particularly among high-achieving athletes, represent a meaningful UIT type due to their psychological and performance-related impact. Taking a dynamic view of UIT control process, this study tested the effect of thought-control strategies among sub-elite to elite athletes, applied to individualized choking thoughts. Ninety athletes recollected recent athletic choking experiences prior to being randomized into one of three thought control interventions using strategies of either acceptance, passive monitoring (control), or suppression. To control for individual differences, athletes’ working memory capacity was measured and modeled as a covariate at baseline. The activation of choking thoughts during and after the intervention was gauged through multiple measurement approaches including conscious presence in mind, priming, and event-related potentials (P3b and N400 amplitudes). Results indicated that, relative to the control, suppression led to enhanced priming and reduced conscious presence of choking thoughts, whereas acceptance resulted in an opposite pattern of reduced priming and increased conscious presence of choking thoughts. In addition, thought-related stimuli elicited less negative-going N400 amplitudes and more positive-going P3b amplitudes than control stimuli. These findings advance understandings of the control mechanism underpinning UITs, and generate applied implications regarding UIT control in high-risk populations such as those with athletic expertise.

scholarly journals Accurate Power-Efficient Format-Scalable Multi-Parallel Optical Digital-to-Analogue Conversion

Photonics ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 38
Author(s):  
Moshe Nazarathy ◽  
Ioannis Tomkos
Keyword(s):  
Energy Efficiency ◽  
Direct Detection ◽  
Coherent Detection ◽  
Performance Limits ◽  
Optical Modulators ◽  
Analog To Digital ◽  
Power Efficient ◽  
Optical Signals ◽  
Digital To Analog Converters ◽  
Optical Analog

In optical transmitters generating multi-level constellations, optical modulators are preceded by Electronic Digital-to-Analog-Converters (eDAC). It is advantageous to use eDAC-free Optical Analog to Digital Converters (oDAC) to directly convert digital bitstreams into multilevel PAM/QAM optical signals. State-of-the-art oDACs are based on Segmented Mach-Zehnder-Modulators (SEMZM) using multiple modulation segments strung along the MZM waveguides to serially accumulate binary-modulated optical phases. Here we aim to assess performance limits of the Serial oDACs (SEMZM) and introduce an alternative improved Multi-Parallel oDAC (MPoDAC) architecture, in particular based on arraying multiple binary-driven MZMs in parallel: Multi-parallel MZM (MPMZM) oDAC. We develop generic methodologies of oDAC specification and optimization encompassing both SEMZM and MPMZM options in Direct-Detection (DD) and Coherent-Detection (COH) implementations. We quantify and compare intrinsic performance limits of the various serial/parallel DD/COH subclasses for general constellation orders, comparing with the scant prior-work on the multi-parallel option. A key finding: COH-MPMZM is the only class synthesizing ‘perfect’ (equi-spaced max-full-scale) constellations while maximizing energy-efficiency-SEMZM/MPMZM for DD are less accurate when maximal energy-efficiency is required. In particular, we introduce multiple variants of PAM4|8 DD and QAM16|64 COH MPMZMs, working out their accuracy vs. energy-efficiency-and-complexity tradeoffs, establishing their format-reconfigurability (format-flexible switching of constellation order and/or DD/COH).

scholarly journals Active Control of Greenhouse Climate Enhances Papaya Growth and Yield at an Affordable Cost

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 378
Author(s):  
Irene Salinas ◽  
Juan José Hueso ◽  
Julián Cuevas
Keyword(s):  
Active Control ◽  
Skin Color ◽  
Natural Ventilation ◽  
Control Strategies ◽  
Soluble Solids ◽  
Growth And Yield ◽  
Climate Control ◽  
Tropical Fruit ◽  
Greenhouse Climate ◽  
Solids Content

Papaya is a tropical fruit crop that in subtropical regions depends on protected cultivation to fulfill its climate requirements and remain productive. The aim of this work was to compare the profitability of different climate control strategies in greenhouses located in subtropical areas of southeast Spain. To do so, we compared papayas growing in a greenhouse equipped with active climate control (ACC), achieved by cooling and heating systems, versus plants growing in another greenhouse equipped with passive climate control (PCC), consisting of only natural ventilation through zenithal and lateral windows. The results showed that ACC favored papaya plant growth; flowering; fruit set; and, consequently, yields, producing more and heavier fruits at an affordable cost. Climate control strategies did not significantly improve fruit quality, specifically fruit skin color, acidity, and total soluble solids content. In conclusion, in the current context of prices, an active control of temperature and humidity inside the greenhouse could be a more profitable strategy in subtropical regions where open-air cultivation is not feasible.

Active control of flexible structures using a fuzzy logic algorithm

2002 ◽  
Vol 11 (4) ◽  
pp. 541-552 ◽  
Author(s):  
Kelly Cohen ◽  
Tanchum Weller ◽  
Joseph Z Ben-Asher
Keyword(s):  
Fuzzy Logic ◽  
Active Control ◽  
Flexible Structures ◽  
Fuzzy Logic Algorithm

Tensegrity Structures in the Design of Flexible Structures for Offshore Aquaculture

2007 ◽  
Author(s):  
O̸sten Jensen ◽  
Anders Sunde Wroldsen ◽  
Pa˚l Furset Lader ◽  
Arne Fredheim ◽  
Mats Heide ◽  
...  
Keyword(s):  
Flexible Structures ◽  
Weather Conditions ◽  
High Energy ◽  
Open Ocean ◽  
Element Analysis ◽  
Tensegrity Structures ◽  
Stiffness Properties ◽  
Offshore Aquaculture ◽  
And Performance ◽  
Open Ocean Aquaculture

Aquaculture is the fastest growing food producing sector in the world. Considerable interest exists in developing open ocean aquaculture in response to a shortage of suitable, sheltered inshore locations. The harsh weather conditions experienced offshore lead to a focus on new structure concepts, remote monitoring and a higher degree of automation in order to keep the cost of structures and operations within an economically viable range. This paper proposes tensegrity structures in the design of flexible structures for offshore aquaculture. The finite element analysis program ABAQUS™ has been used to investigate stiffness properties and performance of tensegrity structures when subjected to various forced deformations and hydrodynamic load conditions. The suggested concept, the tensegrity beam, shows promising stiffness properties in tension, compression and bending, which are relevant for development of open ocean aquaculture construction for high energy environments. When designing a tensegrity beam, both pre-stress and spring stiffness should be considered to ensure the desired structural properties. A large strength to mass ratio and promising properties with respect to control of geometry, stiffness and vibration could make tensegrity an enabling technology for future developments.

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