The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform

Jimoh O Pedro - One of the best experts on this subject based on the ideXlab platform.

  • evolutionary algorithm based pid controller tuning for nonlinear quarter car electrohydraulic vehicle suspensions
    Nonlinear Dynamics, 2014
    Co-Authors: Muhammed Dangor, Olurotimi Akintunde Dahunsi, Jimoh O Pedro
    Abstract:

    The basic challenge associated with the design of vehicle suspension system is the attainment of an optimal trade-off between the various design objectives. This study presents the design of proportional-integral-derivative (PID) controller for a quarter-car active vehicle suspension system (AVSS) using evolutionary algorithms (EA) such as the particle swarm optimization (PSO), genetic algorithm (GA) and differential evolution (DE). Each of the EA-based PID controllers showed overall improvement in suspension travel, ride comfort, settling time and road holding from the manually tuned controller and the passive vehicle suspension system. These improvements were, however, achieved at the cost of increased Actuator Force, power consumption and spool-valve displacement. DE-optimized PID control resulted in the best minimized suspension performance, followed by the GA and PSO, respectively. Frequency-domain analysis showed that all the signals were attenuated within the whole body vibration frequency range and the EA-optimized controllers had RMS frequency weighted body acceleration of the vehicle within allowable limits for vibration exposure. Robustness analysis of the DE-optimized PID-controlled AVSS to model uncertainties is carried out in the form of variation in vehicle sprung mass loading, tyre stiffness and speed.

  • Proportional-integral-derivative control of nonlinear half-car electro-hydraulic suspension systems
    Journal of Zhejiang University SCIENCE A, 2013
    Co-Authors: John E. D. Ekoru, Jimoh O Pedro
    Abstract:

    This paper presents the development of a proportional-integral-derivative (PID)-based control method for application to active vehicle suspension systems (AVSS). This method uses an inner PID hydraulic Actuator Force control loop, in combination with an outer PID suspension travel control loop, to control a nonlinear half-car AVSS. Robustness to model uncertainty in the form of variation in suspension damping is tested, comparing performance of the AVSS with a passive vehicle suspension system (PVSS), with similar model parameters. Spectral analysis of suspension system model output data, obtained by performing a road input disturbance frequency sweep, provides frequency response plots for both nonlinear vehicle suspension systems and time domain vehicle responses to a sinusoidal road input disturbance on a smooth road. The results show the greater robustness of the AVSS over the PVSS to parametric uncertainty in the frequency and time domains.

Michael Z. Q. Chen - One of the best experts on this subject based on the ideXlab platform.

  • multiplexed model predictive control for active vehicle suspensions
    International Journal of Control, 2015
    Co-Authors: Yinlong Hu, Michael Z. Q. Chen
    Abstract:

    Multiplexed model predictive control (MMPC) is a recently proposed efficient model predictive control (MPC) algorithm, which can effectively reduce the computational burden of the online optimisation in MPC implementation by updating the control inputs in an asynchronous manner. This paper investigates the application of MMPC in active vehicle suspension design. An MMPC controller integrated with soft constraints and a Kalman filter is proposed based on a full-car model. Ride comfort, roadholding and suspension deflection are considered in this paper, where ride comfort and roadholding are formulated as a quadratic cost function in terms of sprung mass accelerations and tyre deflections, while suspension deflection performance is formulated as a hard constraint. The saturation of the Actuator Force is also considered and formulated as a hard constraint as well. Numerical simulation is performed with respect to different choices of weighting factors, vehicle speeds and control horizons. The results show th...

Yinlong Hu - One of the best experts on this subject based on the ideXlab platform.

  • multiplexed model predictive control for active vehicle suspensions
    International Journal of Control, 2015
    Co-Authors: Yinlong Hu, Michael Z. Q. Chen
    Abstract:

    Multiplexed model predictive control (MMPC) is a recently proposed efficient model predictive control (MPC) algorithm, which can effectively reduce the computational burden of the online optimisation in MPC implementation by updating the control inputs in an asynchronous manner. This paper investigates the application of MMPC in active vehicle suspension design. An MMPC controller integrated with soft constraints and a Kalman filter is proposed based on a full-car model. Ride comfort, roadholding and suspension deflection are considered in this paper, where ride comfort and roadholding are formulated as a quadratic cost function in terms of sprung mass accelerations and tyre deflections, while suspension deflection performance is formulated as a hard constraint. The saturation of the Actuator Force is also considered and formulated as a hard constraint as well. Numerical simulation is performed with respect to different choices of weighting factors, vehicle speeds and control horizons. The results show th...

Amir Khajepour - One of the best experts on this subject based on the ideXlab platform.

  • minimum norm solution for the Actuator Forces in cable based parallel manipulators based on convex optimization
    International Conference on Robotics and Automation, 2007
    Co-Authors: M Hassan, Amir Khajepour
    Abstract:

    Cable-based parallel manipulators (CPM) are light-weight manipulators that can reach high accelerations. The difference between the design of CPM and that of rigid-link parallel manipulators is that cables can only perform while under tension. Redundant limbs, such as extra cables, springs, or cylinders, can be used for applying Forces on the mobile platform to generate cable tensions resulting in a redundantly actuated manipulator. To operate this manipulator, the Actuator-Force distribution amongst the cables and the redundant limbs needs to be determined. Actuator-Force optimization techniques developed for rigid-link manipulators are unsuitable for CPM. In this study, a numerical procedure based on convex analysis and optimization is presented to calculate the minimum-norm solution that minimizes the 2-norm of Actuator Forces. The procedure is based on convex optimization that utilizes the Dykstra's alternating projection algorithm to reach to the optimum solution. This numerical method is successfully applied to 3- and 6-degree-of-freedom (DOF) spatial CPMs to determine the optimum Actuator Forces for a given external load. This study addresses the static analysis in cable-based parallel manipulators in the language of convex analysis

Balbino Dos Santos Pereira R. - One of the best experts on this subject based on the ideXlab platform.

  • Active Stall Control of Horizontal Axis Wind Turbines: A dedicated study with emphasis on DBD plasma Actuators
    2016
    Co-Authors: Balbino Dos Santos Pereira R.
    Abstract:

    The contribution of sustainable Wind Energy (WE) to the global energy scenario has beensteadily increasing over the past decades. In the process, Horizontal Axis Wind Turbines(HAWT) became the most widespread and largest WE harvesting machines. Nevertheless,significant challenges still lie ahead of further expansion of HAWT, namely concerning systemrobustnessand cost-of-energy(COE) competitiveness. This dissertation studies aHAWTdesign concept termed modern Active Stall Control (ASC). With this concept HAWT powerregulation is achieved using flowcontrol Actuators to trim the aerodynamic loads across theoperational envelope. The underpinning idea is that as the aerodynamic loads are trimmedby flowcontrol Actuatorswithout pitching the blades, the pitch system may be mitigated. Inturn, this might lead to decreased failure-rates and down-time, and thus eventually presenta more cost-effective solution than state-of-the art HAWTs. Going specifically into ASC, ifaerodynamic load trimming is performed it is necessary to employ a flow control Actuator.From different flow control Actuator types, since the aim is to reduce the maintenance andoperational costs of ASC machines, Actuators with few mechanical parts become more interesting.As such the present research also focuses on the Alternating Current DielectricBarrier Discharge (AC-DBD) plasma Actuator, owing among other things to its absence ofmoving parts, negligible mass and virtually unlimited bandwidth of actuation.A preliminary study on the feasibility of active stall control to regulate HAWT powerproduction in replacement of the pitch system is conducted. By taking the National RenewableEnergy Laboratory 5MWturbine as reference, a simple blade element momentumcode is used to assess the required actuation authority. Considering half of the blade spanis equipped with Actuators, the required change in the lift coefficient to regulate power isestimated in ¢Cl Æ 0.7. Concerning actuation technologies, three flow control devices areinvestigated, namely Boundary Layer Transpiration, Trailing Edge Jets and Dielectric BarrierDischarge plasma Actuators. Results indicate the authority of the Actuators consideredis not sufficient to regulate power, since the change in the lift coefficient is not large enough.Especially if a pitch-controlledmachine is used as baseline case. Active stall control of HorizontalAxisWind Turbines appears feasible only if the rotor is re-designed from the start toincorporate active-stall devices.Regarding AC-DBD plasma Actuators, three specific topics are investigated. The differentstudies aim at DBD performance characterization, namely at the influence of externalflow on DBD plasma momentum transfer and on the frequency response of Actuator flowregion characteristic of DBD pulse operation. Both these topics are important to bridge thegap between academic-laboratory employment of DBD and large-size industrial applications.Finally regarding DBD plasma Actuator modeling, a method is developed to describeplasma actuation effects in integral boundary layer formulation, and coupled to a viscous-inviscid panel code (similar to XFOIL), while an experimental campaign is carried to validatethe predictions. The three DBD plasma studies are further described below.Addressing cross-talk effects between DBD plasma Actuators and external flow, a studyis carried out in which an Actuator is positioned in a boundary layer operated in a range offree stream velocities from 0 to 60m/s, and tested both in counter-flow and co-flow forcingconfigurations. Electrical measurements and a CCD camera are used to characterize theDBD performance at different external flow speeds, while the Actuator thrust is measuredusing a sensitive load cell. Results show the power consumption is constant for differentflow velocities and Actuator configurations, while the plasma light emission is constant forco-flow forcing but increases with counter-flow forcing for increasing free stream velocities.The measured Force is constant for free stream velocities larger than 20m/s, with samemagnitude and opposite direction for the counter-flow and co-flow configurations. In quiescentconditions the measured Force is smaller due to the change in wall shear Force by theinduced wall-jet. In addition to the experimental study, an analytical model is presented toestimate the influence of external flow on the Actuator Force. It is based on conservation ofmomentum through the ion-neutral collisional process while including the contribution ofthe wall shear Force. Model results compare well with experimental data at different externalflow velocities, while extrapolation to larger velocities shows variation in Actuator thrustof at least 10% for external speedU Æ 200m/s.Concerning the response of DBD Actuator region flow to pulsed operation, a methodologyis provided to derive the local frequency response of flow under actuation, in termsof the magnitude of Actuator induced velocity perturbations. The method is applied to anAC- DBD plasma Actuator but can be extended to other kinds of pulsed actuation. For thederivation, the Actuator body Force termis introduced in the Navier-Stokes equations, fromwhich the flow is locally approximated with a linear-time-invariant (LTI) system. The proposedsemi-phenomenologicalmodel includes the effect of both viscosity and external flowvelocity, while providing a system response in the frequency domain. Experimental data iscompared with analytical results for a typical DBD plasma Actuator operating in quiescentflow and in a laminar boundary layer. Good agreement is obtained between analytical andexperimental results for cases below the model validity threshold frequency. These resultsdemonstrate an efficient yet simple approach towards prediction of the response of a convectiveflow to pulsed actuation. Future application of the methodology might include actuationscheduling design and optimization for different flow control scenarios.The third study specifically addressing DBD plasma Actuators presents a methodologyto model the effect of DBD plasma Actuators on airfoil performance within the frameworkof a viscous-inviscid airfoil analysis code. The approach is valid for incompressible, turbulentflow applications. The effect of (plasma) body Forces in the boundary layer is analyzedwith a generalized form of the von Kármán integral boundary layer equations. The additionalterms appearing in the von Kármán equations give rise to a new closure relation. Themodel is implemented in a viscous-inviscid airfoil analysis code and validated by carryingout an experimental study. PIV measurements are performed on an airfoil equipped withDBD plasma Actuators over a range of Reynolds number and angle of attack combinations.Balance measurements are also collected to evaluate the lift and drag coefficients. Resultsshow the proposed model captures the magnitude of the variation in IBL parameters fromDBD actuation. Additionally the magnitude of the lift coefficient variations (¢Cl ) inducedby plasma actuation is reasonably estimated. As such, this approach enables the design ofairfoils specifically tailored for DBD plasma flow control.Transitioning into ASCrotor design, and building on the previously presented, a methodologyis introduced for designing airfoils suitable to employ actuation in a wind energy environment.The novel airfoil sections are baptized WAP (Wind Energy Actuated Profiles). Agenetic algorithm based multiobjective airfoil optimizer is formulated by setting two costfunctions, one for wind energy performance and the other representing actuation suitability.The wind energy cost function considers ’reference’ wind energy airfoils while using aprobabilistic approach to include the effects of turbulence and wind shear. The actuationsuitability cost function is developed for HAWT active stall control, including two differentcontrol strategies designated by ’enhanced’ and ’decreased’ performance. Two differentactuation types are considered, namely boundary layer transpiration and DBD plasma.Results show that using WAP airfoils provides much higher control efficiency than addingactuation on reference wind energy airfoils, without detrimental effects in non-actuatedoperation. The WAP sections yield an Actuator employment efficiency that is 2 to 4 timeslarger than obtained with reference wind energy airfoils. Regarding geometry, WAP sectionsfor decreased performance display an upper surface concave aft-region compared totypical wind energy ’reference’ airfoils,while retaining common sharp nose and S-tail (characteristicaft-loading) features. Results show there is much to gain in designing airfoils fromthe beginning to include actuation effects, especially compared to employing actuation onalready existing airfoils, which ultimately might pave theway for novelHAWT control strategies.Finally addressing the complete rotor planform design, an optimization study tailors aHAWT rotor to ASC operation, in a aero-structural-servo formulation. The study considersthe aerodynamic and structural loads are in static equilibrium, and as such no unsteady effectsare taken into account. The optimization includes planformgeometry design but alsoactuation scheduling, rated rotational speed and spanwise laminate skin thickness. Resultsshow that, compared to variable-pitch turbines, ASC planform displays increased chord atinboard stations with decreased twist angle towards the tip, resulting in increased AOA. Actuationis employed to trim the (static) loads across the operational wind speed envelopeand hence reduce load overshoots and associated costs. Comparing with state-of-the-artpitch machines, the expected COE of the ASC rotor does not indicate a significant decrease,but appears to be at least competitive with pitch-controlled HAWTs if the pitch system is effectivelymitigated. Additionally, and though not explicitly considered in the present work,it is foreseen ASC might become interesting if the actuation system allows for further OMcost reduction via fatigue load-alleviation, since the actuation trimming load system is anyhowincluded in an ASC machine

  • Active Stall Control of Horizontal Axis Wind Turbines: A dedicated study with emphasis on DBD plasma Actuators
    2016
    Co-Authors: Balbino Dos Santos Pereira R.
    Abstract:

    The contribution of sustainable Wind Energy (WE) to the global energy scenario has beensteadily increasing over the past decades. In the process, Horizontal Axis Wind Turbines(HAWT) became the most widespread and largest WE harvesting machines. Nevertheless,significant challenges still lie ahead of further expansion of HAWT, namely concerning systemrobustnessand cost-of-energy(COE) competitiveness. This dissertation studies aHAWTdesign concept termed modern Active Stall Control (ASC). With this concept HAWT powerregulation is achieved using flowcontrol Actuators to trim the aerodynamic loads across theoperational envelope. The underpinning idea is that as the aerodynamic loads are trimmedby flowcontrol Actuatorswithout pitching the blades, the pitch system may be mitigated. Inturn, this might lead to decreased failure-rates and down-time, and thus eventually presenta more cost-effective solution than state-of-the art HAWTs. Going specifically into ASC, ifaerodynamic load trimming is performed it is necessary to employ a flow control Actuator.From different flow control Actuator types, since the aim is to reduce the maintenance andoperational costs of ASC machines, Actuators with few mechanical parts become more interesting.As such the present research also focuses on the Alternating Current DielectricBarrier Discharge (AC-DBD) plasma Actuator, owing among other things to its absence ofmoving parts, negligible mass and virtually unlimited bandwidth of actuation.A preliminary study on the feasibility of active stall control to regulate HAWT powerproduction in replacement of the pitch system is conducted. By taking the National RenewableEnergy Laboratory 5MWturbine as reference, a simple blade element momentumcode is used to assess the required actuation authority. Considering half of the blade spanis equipped with Actuators, the required change in the lift coefficient to regulate power isestimated in ¢Cl Æ 0.7. Concerning actuation technologies, three flow control devices areinvestigated, namely Boundary Layer Transpiration, Trailing Edge Jets and Dielectric BarrierDischarge plasma Actuators. Results indicate the authority of the Actuators consideredis not sufficient to regulate power, since the change in the lift coefficient is not large enough.Especially if a pitch-controlledmachine is used as baseline case. Active stall control of HorizontalAxisWind Turbines appears feasible only if the rotor is re-designed from the start toincorporate active-stall devices.Regarding AC-DBD plasma Actuators, three specific topics are investigated. The differentstudies aim at DBD performance characterization, namely at the influence of externalflow on DBD plasma momentum transfer and on the frequency response of Actuator flowregion characteristic of DBD pulse operation. Both these topics are important to bridge thegap between academic-laboratory employment of DBD and large-size industrial applications.Finally regarding DBD plasma Actuator modeling, a method is developed to describeplasma actuation effects in integral boundary layer formulation, and coupled to a viscous-inviscid panel code (similar to XFOIL), while an experimental campaign is carried to validatethe predictions. The three DBD plasma studies are further described below.Addressing cross-talk effects between DBD plasma Actuators and external flow, a studyis carried out in which an Actuator is positioned in a boundary layer operated in a range offree stream velocities from 0 to 60m/s, and tested both in counter-flow and co-flow forcingconfigurations. Electrical measurements and a CCD camera are used to characterize theDBD performance at different external flow speeds, while the Actuator thrust is measuredusing a sensitive load cell. Results show the power consumption is constant for differentflow velocities and Actuator configurations, while the plasma light emission is constant forco-flow forcing but increases with counter-flow forcing for increasing free stream velocities.The measured Force is constant for free stream velocities larger than 20m/s, with samemagnitude and opposite direction for the counter-flow and co-flow configurations. In quiescentconditions the measured Force is smaller due to the change in wall shear Force by theinduced wall-jet. In addition to the experimental study, an analytical model is presented toestimate the influence of external flow on the Actuator Force. It is based on conservation ofmomentum through the ion-neutral collisional process while including the contribution ofthe wall shear Force. Model results compare well with experimental data at different externalflow velocities, while extrapolation to larger velocities shows variation in Actuator thrustof at least 10% for external speedU Æ 200m/s.Concerning the response of DBD Actuator region flow to pulsed operation, a methodologyis provided to derive the local frequency response of flow under actuation, in termsof the magnitude of Actuator induced velocity perturbations. The method is applied to anAC- DBD plasma Actuator but can be extended to other kinds of pulsed actuation. For thederivation, the Actuator body Force termis introduced in the Navier-Stokes equations, fromwhich the flow is locally approximated with a linear-time-invariant (LTI) system. The proposedsemi-phenomenologicalmodel includes the effect of both viscosity and external flowvelocity, while providing a system response in the frequency domain. Experimental data iscompared with analytical results for a typical DBD plasma Actuator operating in quiescentflow and in a laminar boundary layer. Good agreement is obtained between analytical andexperimental results for cases below the model validity threshold frequency. These resultsdemonstrate an efficient yet simple approach towards prediction of the response of a convectiveflow to pulsed actuation. Future application of the methodology might include actuationscheduling design and optimization for different flow control scenarios.The third study specifically addressing DBD plasma Actuators presents a methodologyto model the effect of DBD plasma Actuators on airfoil performance within the frameworkof a viscous-inviscid airfoil analysis code. The approach is valid for incompressible, turbulentflow applications. The effect of (plasma) body Forces in the boundary layer is analyzedwith a generalized form of the von Kármán integral boundary layer equations. The additionalterms appearing in the von Kármán equations give rise to a new closure relation. Themodel is implemented in a viscous-inviscid airfoil analysis code and validated by carryingout an experimental study. PIV measurements are performed on an airfoil equipped withDBD plasma Actuators over a range of Reynolds number and angle of attack combinations.Balance measurements are also collected to evaluate the lift and drag coefficients. Resultsshow the proposed model captures the magnitude of the variation in IBL parameters fromDBD actuation. Additionally the magnitude of the lift coefficient variations (¢Cl ) inducedby plasma actuation is reasonably estimated. As such, this approach enables the design ofairfoils specifically tailored for DBD plasma flow control.Transitioning into ASCrotor design, and building on the previously presented, a methodologyis introduced for designing airfoils suitable to employ actuation in a wind energy environment.The novel airfoil sections are baptized WAP (Wind Energy Actuated Profiles). Agenetic algorithm based multiobjective airfoil optimizer is formulated by setting two costfunctions, one for wind energy performance and the other representing actuation suitability.The wind energy cost function considers ’reference’ wind energy airfoils while using aprobabilistic approach to include the effects of turbulence and wind shear. The actuationsuitability cost function is developed for HAWT active stall control, including two differentcontrol strategies designated by ’enhanced’ and ’decreased’ performance. Two differentactuation types are considered, namely boundary layer transpiration and DBD plasma.Results show that using WAP airfoils provides much higher control efficiency than addingactuation on reference wind energy airfoils, without detrimental effects in non-actuatedoperation. The WAP sections yield an Actuator employment efficiency that is 2 to 4 timeslarger than obtained with reference wind energy airfoils. Regarding geometry, WAP sectionsfor decreased performance display an upper surface concave aft-region compared totypical wind energy ’reference’ airfoils,while retaining common sharp nose and S-tail (characteristicaft-loading) features. Results show there is much to gain in designing airfoils fromthe beginning to include actuation effects, especially compared to employing actuation onalready existing airfoils, which ultimately might pave theway for novelHAWT control strategies.Finally addressing the complete rotor planform design, an optimization study tailors aHAWT rotor to ASC operation, in a aero-structural-servo formulation. The study considersthe aerodynamic and structural loads are in static equilibrium, and as such no unsteady effectsare taken into account. The optimization includes planformgeometry design but alsoactuation scheduling, rated rotational speed and spanwise laminate skin thickness. Resultsshow that, compared to variable-pitch turbines, ASC planform displays increased chord atinboard stations with decreased twist angle towards the tip, resulting in increased AOA. Actuationis employed to trim the (static) loads across the operational wind speed envelopeand hence reduce load overshoots and associated costs. Comparing with state-of-the-artpitch machines, the expected COE of the ASC rotor does not indicate a significant decrease,but appears to be at least competitive with pitch-controlled HAWTs if the pitch system is effectivelymitigated. Additionally, and though not explicitly considered in the present work,it is foreseen ASC might become interesting if the actuation system allows for further OMcost reduction via fatigue load-alleviation, since the actuation trimming load system is anyhowincluded in an ASC machine.Wind Energ