Optimal Control of Vertically Stroking Crew Seats Employing Magnetorheological Energy Absorbers

2009 ◽  
Author(s):  
Harinder J. Singh ◽  
Young-Tai Choi ◽  
Norman M. Wereley
Keyword(s):  
Optimal Control ◽  
Impact Velocity ◽  
Vibration Isolation ◽  
Viscous Force ◽  
Bingham Number ◽  
Shock Mitigation ◽  
Feasible Range ◽  
Shock Event ◽  
Damper Design ◽  
Energy Absorbers

Nondimensional analyses of vertical stroking crew seats with adaptive nonlinear magnetorheological energy absorbers (MREA) and magnetorheological shock isolation (MRSI) were addressed in this study. Under consideration were single-degree-of-freedom vertically stroking seat systems consisting of a rigid occupant mass falling with prescribed initial impact velocity (sink rate). The governing equations of the vertical stroking crew seats were derived using nondimensional variables such as nondimensional stroke, velocity, acceleration and time constant, as well as nondimensional Bingham number (i.e., the ratio of MR yield force to viscous force). The critical Bingham number was defined as that Bingham number for which the available stroke was fully utilized and the seat reaches zero velocity at the end of stroke. This was done in order to maximize shock mitigation performance. Two cases were studied: (1) the MREA problem, or the case where no spring was employed in the suspension, so that the seat was used for a single shock event, (2) the MRSI problem, or the case where a spring was employed in the suspension, so that after the initial shock event, the suspension could be used for either vibration isolation or mitigation of subsequent shock events. Nondimensional displacement, velocity and acceleration were analyzed for MREA and MRSI vertical stroking crew seats for three different payload masses of 47, 77 and 97 kg corresponding to 5th percentile (%tile) female, 50th %tile and 95th %tile male, respectively, with initial impact velocities of 4, 5 and 6 m/s. An optimal control solution was derived for both the MREA and MRSI cases. The effects of payload mass and initial impact velocity on the optimal responses of the vertical stroking crew seats were analyzed for a feasible range of Bingham number based on a realistically constrained (in diameter and volume) MR damper design.

Optimal control of drop-induced shock mitigation using magnetorheological energy absorbers considering quadratic damping

2021 ◽  
pp. 1045389X2199392
Author(s):  
Mukai Wang ◽  
Zhaobo Chen ◽  
Hui Yan ◽  
Young-Tai Choi ◽  
Norman M Wereley
Keyword(s):  
Optimal Control ◽  
Control Algorithm ◽  
Control Method ◽  
Soft Landing ◽  
Minimum Duration ◽  
Single Degree Of Freedom ◽  
Bingham Number ◽  
Shock Mitigation ◽  
Energy Absorbers ◽  
Quadratic Damping

The optimal control of a magnetorheological energy absorber (MREA) shock mitigation system is investigated considering quadratic damping in the MREA. To this end, the equation of motion of a single-degree-of-freedom (SDOF) shock suspension system using an MREA with quadratic damping is analyzed. To achieve a soft landing and to maintain stroking load below a maximum allowable value, it is required that the payload comes to rest after fully utilizing the available stroke. For low sink rates, a generalized Bingham number (quadratic) or GBN-Q control algorithm is developed that achieves a soft landing by selecting an initial magnetorheological (MR) force level or generalized Bingham number (GBN) for the quadratic damping at the initial sink rate. To cope with the cases above a critical sink rate, where the deceleration exceeds a maximum allowable threshold when using the GBN-Q control only, a minimum duration deceleration exposure-quadratic (MDDE-Q) controller is developed. This controller seeks to maintain the stroking load at its maximum allowable threshold until the payload slows such that the GBN-Q controller can be used to achieve the soft landing condition. The switching methodology between the GBN-Q controller and the MDDE-Q controller is discussed. Each control method relies on an optimal GBN that is computed to ensure a soft landing. Results show that the MDDE-Q controller can successfully minimize the exposure of the payload to the maximum allowable stroking load.

Drop-Induced Shock Mitigation Using Adaptive Magnetorheological Energy Absorbers Incorporating a Time Lag

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Young-Tai Choi ◽  
Norman M. Wereley
Keyword(s):  
Equations Of Motion ◽  
Time Lag ◽  
Soft Landing ◽  
Single Degree Of Freedom ◽  
Bingham Number ◽  
Shock Mitigation ◽  
Payload Mass ◽  
Energy Absorbers ◽  
Time Required ◽  
The Impact

This study addresses the nondimensional analysis of drop-induced shock mitigated using magnetorheological energy absorbers (MREAs) incorporating a time lag. This time lag arises from two sources: (1) the time required to generate magnetic field in the electromagnet once current has been applied and (2) the time required for the particles in the magnetorheological fluid to form chains. To this end, the governing equations of motion for a single degree-of-freedom (SDOF) system using an MREA with a time lag were derived. Based on these equations, nondimensional stroke, velocity, and acceleration of the payload were derived, where the MREA with a time lag was used to control payload deceleration after the impact. It is established that there exists an optimal Bingham number that allows the payload mass to achieve a soft landing, that is, the payload comes to rest after utilizing the available stroke of the MREA. Finally, the shock mitigation performance when using this optimal Bingham number control strategy is analyzed, and the effects of time lag are quantified.

An adaptive shock mitigation control method for helicopter seat system with magnetorheological energy absorbers

2021 ◽  
pp. 1045389X2110387
Author(s):  
Zhongqiang Feng ◽  
Zhaobo Chen ◽  
Xudong Xing
Keyword(s):  
Control Method ◽  
Selection Criterion ◽  
Threshold Value ◽  
Damping Force ◽  
Comparative Performance ◽  
Bingham Number ◽  
Control Stage ◽  
Shock Mitigation ◽  
Energy Absorbers ◽  
Maximum Deceleration

This research presents a minimal maximum deceleration (MMD) control method which can be used in the shock mitigation system with magnetorheological energy absorbers (MREAs). The proposed control method can make the payload stop at the end of the available MREA stroke with the lowest maximum deceleration, which does not exceed the deceleration threshold value and lead to the lowest occupant injury probability. The shock mitigation system controlled by MMD will experience constant deceleration control stage and maximum damping force control stage while making full use of the available MREA stroke. The comparative performance of the MMD control method with Bingham number (BN) control, constant deceleration (CD) control and minimum duration deceleration exposure (MDDE) control is shown. Then, the controllable drop velocity range and the required maximum MREA controllable damping force range of MMD control method is calculated. Subsequently, the optimal control method selection criterion among BN control method, CD control method and MMD control method is developed. Finally, the optimal selection criterion is applied to the drop induced shock mitigation system with varying payload velocity, payload mass (occupant type) and the maximum controllable damping force of MREA.

Adaptive Control of a Sliding Seat Using Magnetorheological Energy Absorbers

2010 ◽  
Author(s):  
Min Mao ◽  
Norman M. Wereley ◽  
Alan L. Browne
Keyword(s):  
Adaptive Control ◽  
Degrees Of Freedom ◽  
Adaptive Controller ◽  
Degree Of Freedom ◽  
Lumped Mass ◽  
Adaptive Controllers ◽  
Bingham Number ◽  
Control Objective ◽  
Payload Mass ◽  
Energy Absorbers

Feasibility of a sliding seat utilizing adaptive control of a magnetorheological (MR) energy absorber (MREA) to minimize loads imparted to a payload mass in a ground vehicle for frontal impact speeds as high as 7 m/s (15.7 mph) is investigated. The crash pulse for a given impact speed was assumed to be a rectangular deceleration pulse having a prescribed magnitude and duration. The adaptive control objective is to bring the payload (occupant plus seat) mass to a stop using the available stroke, while simultaneously accommodating changes in impact velocity and occupant mass ranging from a 5th percentile female to a 95th percentile male. The payload is first treated as a single-degree-of-freedom (SDOF) rigid lumped mass, and two adaptive control algorithms are developed: (1) constant Bingham number control, and (2) constant force control. To explore the effects of occupant compliance on adaptive controller performance, a multi-degree-of-freedom (MDOF) lumped mass biodynamic occupant model was integrated with the seat mass. The same controllers were used for both the SDOF and MDOF cases based on SDOF controller analysis because the biodynamic degrees of freedom are neither controllable nor observable. The designed adaptive controllers successfully controlled load-stroke profiles to bring payload mass to rest in the available stroke and reduced payload decelerations. Analysis showed extensive coupling between the seat structures and occupant biodynamic response, although minor adjustments to the control gains enabled full use of the available stroke.

scholarly journals Vibration Isolation Review: II. Shock Excitation

1996 ◽  
Vol 3 (6) ◽  
pp. 451-459 ◽  
Author(s):  
F.C. Nelson
Keyword(s):  
Vibration Isolation ◽  
Shock Velocity ◽  
Shock Excitation ◽  
Shock Mitigation ◽  
Flexible Connections

This is the second part of a two part review of shock and vibration isolation. It covers three distinct categories of shock excitation—pulselike shock, velocity shock, and complex shock—and discusses the means that are available in each case to measure the effectiveness of shock mitigation by the imposition of flexible connections between the isolated system and its base.

scholarly journals Taylor state dynamos found by optimal control: axisymmetric examples

2018 ◽  
Vol 853 ◽  
pp. 647-697 ◽  
Author(s):  
Kuan Li ◽  
Andrew Jackson ◽  
Philip W. Livermore
Keyword(s):  
Magnetic Field ◽  
Optimal Control ◽  
Vector Fields ◽  
Inertial Force ◽  
Basis Set ◽  
Viscous Force ◽  
Time Step ◽  
Geostrophic Flow ◽  
Spectral Expansions ◽  
The Magnetic Field

Earth’s magnetic field is generated in its fluid metallic core through motional induction in a process termed the geodynamo. Fluid flow is heavily influenced by a combination of rapid rotation (Coriolis forces), Lorentz forces (from the interaction of electrical currents and magnetic fields) and buoyancy; it is believed that the inertial force and the viscous force are negligible. Direct approaches to this regime are far beyond the reach of modern high-performance computing power, hence an alternative ‘reduced’ approach may be beneficial. Taylor (Proc. R. Soc. Lond. A, vol. 274 (1357), 1963, pp. 274–283) studied an inertia-free and viscosity-free model as an asymptotic limit of such a rapidly rotating system. In this theoretical limit, the velocity and the magnetic field organize themselves in a special manner, such that the Lorentz torque acting on every geostrophic cylinder is zero, a property referred to as Taylor’s constraint. Moreover, the flow is instantaneously and uniquely determined by the buoyancy and the magnetic field. In order to find solutions to this mathematical system of equations in a full sphere, we use methods of optimal control to ensure that the required conditions on the geostrophic cylinders are satisfied at all times, through a conventional time-stepping procedure that implements the constraints at the end of each time step. A derivative-based approach is used to discover the correct geostrophic flow required so that the constraints are always satisfied. We report a new quantity, termed the Taylicity, that measures the adherence to Taylor’s constraint by analysing squared Lorentz torques, normalized by the squared energy in the magnetic field, over the entire core. Neglecting buoyancy, we solve the equations in a full sphere and seek axisymmetric solutions to the equations; we invoke $\unicode[STIX]{x1D6FC}$- and $\unicode[STIX]{x1D714}$-effects in order to sidestep Cowling’s anti-dynamo theorem so that the dynamo system possesses non-trivial solutions. Our methodology draws heavily on the use of fully spectral expansions for all divergenceless vector fields. We employ five special Galerkin polynomial bases in radius such that the boundary conditions are honoured by each member of the basis set, whilst satisfying an orthogonality relation defined in terms of energies. We demonstrate via numerous examples that there are stable solutions to the equations that possess a rapidly decreasing spectrum and are thus well-converged. Classic distributions for the $\unicode[STIX]{x1D6FC}$- and $\unicode[STIX]{x1D714}$-effects are invoked, as well as new distributions. One such new $\unicode[STIX]{x1D6FC}$-effect model possesses oscillatory solutions for the magnetic field, rarely before seen. By comparing our Taylor state model with one that allows torsional oscillations to develop and decay, we show the equilibrium state of both configurations to be coincident. In all our models, the geostrophic flow dominates the ageostrophic flow. Our work corroborates some results previously reported by Wu & Roberts (Geophys. Astrophys. Fluid Dyn., vol. 109 (1), 2015, pp. 84–110), as well as presenting new results; it sets the stage for a three-dimensional implementation where the system is driven by, for example, thermal convection.

Adaptive magnetorheological energy absorber control method for drop-induced shock mitigation

2020 ◽  
pp. 1045389X2095710
Author(s):  
Mukai Wang ◽  
Zhaobo Chen ◽  
Norman M Wereley
Keyword(s):  
Control Method ◽  
Selection Criterion ◽  
Soft Landing ◽  
Energy Absorber ◽  
Bingham Number ◽  
Seat Suspension ◽  
Shock Mitigation ◽  
Optimal Control Method ◽  
Control Goal ◽  
Optimal Criterion

This paper presents a minimum duration deceleration exposure (MDDE) control method for drop-induced shock mitigation system using a magnetorheological energy absorber (MREA) at high sink rates. The key MDDE control goal is that the payload should come to rest after fully using the available MREA stroke, that is, to accomplish a soft landing, without exceeding the maximum allowable deceleration and simultaneously minimizing the duration of exposure to the maximum allowable deceleration. The MDDE control algorithm is developed as follows for a given available stroke. The payload deceleration is initially set to the maximum allowable value and held constant until the remaining damper stroke and payload velocity are such that the Bingham number control can be used for the terminal trajectory to ensure a soft landing. The sink rate range of the MDDE control is calculated and the results show that the MDDE control can be utilized at high sink rates, whereas prior Bingham number control can be used only at sufficiently low sink rates without violating the maximum allowable deceleration constraint. An optimal criterion to switch from the BN control method to MDDE control method is developed. Finally, the optimal control method is applied for a helicopter seat suspension system by optimal selection criterion to automatically accommodate varying sink rate (drop velocity) and occupant weight.

Active Control for Power-Train Vibration of Automotive Using Active Mounts

2013 ◽  
Vol 330 ◽  
pp. 598-601
Author(s):  
Guo Chun Sun ◽  
Li Meng He
Keyword(s):  
Optimal Control ◽  
Vibration Isolation ◽  
Linear Quadratic Regulator ◽  
Active System ◽  
Linear Quadratic ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Engine Vibration ◽  
Active Vibration ◽  
Piezoelectric Stack Actuator

In this work, a new active mount featuring piezostack actuators and a rubber element is proposed and applied to a vibration control system. After describing the configuration and operating principle of the proposed mount, an appropriate rubber element and appropriate piezostacks are designed. Through the analysis of the property of the rubber and piezoelectric stack actuator, a mechanical model of the active vibration isolation system with the active mounts is established. An optimal control algorithm is presented for engine vibration isolation system. the controller is designed according to linear quadratic regulator (LQR) theory. Simulation shows the active system has a better consequence in reducing the vibration of the chassis significantly with respect to the ACM and the optimal control than that in the passive system.

The Research on Robust LQ Control Applied to Uncertain Vibration Isolation System

2010 ◽  
Vol 34-35 ◽  
pp. 1289-1293
Author(s):  
Qiang Hong Zeng ◽  
Qi Wei He ◽  
Jing Jun Lou
Keyword(s):  
Optimal Control ◽  
Transfer Function ◽  
Vibration Isolation ◽  
Multi Objective Optimization ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Robust Optimal Control ◽  
Result Show ◽  
Isolation Performance ◽  
Lq Control

Synthesized considering several performance target, robust optimal control was applied to uncertain double layer vibration isolation system then the transfer function was got between input disturbance and out performance. By analyzing the amplitude-frequency characteristics of transfer function, the result show that the robust LQ control can successfully improve the isolation performance of uncertain hybrid vibration isolation system, realize the multi-objective optimization.

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