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.

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.

A minimum transmitted load control method for shock isolation mounts with magnetorheological energy absorbers

2021 ◽  
pp. 1045389X2110643
Author(s):  
Zhongqiang Feng ◽  
Dong Yu ◽  
Zhaobo Chen ◽  
Xudong Xing ◽  
Hui Yan
Keyword(s):  
Control Method ◽  
Selection Criterion ◽  
Soft Landing ◽  
Damping Force ◽  
Single Degree Of Freedom ◽  
Bingham Number ◽  
Optimal Control Method ◽  
Shock Isolation ◽  
Energy Absorbers ◽  
The Relationship

This paper proposed a minimum transmitted load (MTL) control method for drop-induced shock isolation mounts (SIM) with magnetorheological energy absorbers (MREAs). MTL control method consists of two parts of maximum damping force (MDF) control and one part of constant acceleration (CA) control, which can make the payload stop after fully utilize MREA stroke (soft landing) with minimum transmitted load. The control algorithm of MTL control method is derived in a single-degree-of-freedom (SDOF) system. The relationship between the controllable velocity range of MTL control method and parameters of shock isolation mounts is also derived. An optimal control method selection criterion between Bingham number (BN) control method and MTL control method is developed. The performance of MTL control method and selection criterion are shown by applying to the SIM system with variable drop velocities and system parameters. Results shows that MTL control method has the minimum transmitted load and the selection criterion is feasible.

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.

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.

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.

An improved constant deceleration control method with extended shock velocity range for magnetorheological energy absorber

2021 ◽  
pp. 1045389X2110572
Author(s):  
Zhongqiang Feng ◽  
Dong Yu ◽  
Zhaobo Chen ◽  
Xudong Xing ◽  
Hui Yan
Keyword(s):  
Control Algorithm ◽  
Control Method ◽  
Velocity Range ◽  
Damping Force ◽  
Isolation System ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Shock Mitigation ◽  
Energy Absorbers ◽  
Feasible Solutions

This paper proposed an extended constant deceleration (ECD) control method that can be used in the shock mitigation system with magnetorheological energy absorbers (MREAs). The ECD control method has three sections: zero controllable force (ZCF) section, constant deceleration (CD) section, and maximum damping force (MDF) section. Under the control of ECD, the system can stop at the end of MREA stroke without exceeding the maximum allowable deceleration. The ECD control algorithm is derived in a single-degree-of-freedom (SDOF) system. The controllable velocity range and the required controllable damping force of ECD control method are also derived, which can provide feasible solutions for the design of shock isolation system with MREAs. The performance of ECD control method is shown by applying to the drop-induced shock mitigation system with different drop velocities, different maximum controllable damping force, and MREA stroke. The results shows that the ECD control method not only has a large controllable velocity range and small controllable damping force requirement, but also can minimize the load transmitted to the system.

A Constant Stroking Load Regulator for Shock Absorption

2011 ◽  
Author(s):  
Gang Wang ◽  
Gregory Hiemenz ◽  
Wei Hu ◽  
Norman M. Wereley
Keyword(s):  
Impact Velocity ◽  
Input Parameter ◽  
Control Input ◽  
Soft Landing ◽  
Shock Absorption ◽  
Energy Absorber ◽  
Seat Suspension ◽  
Drop Tests ◽  
Payload Mass ◽  
The Impact

The goal of this study is to provide shock mitigation in an active (or semi-active) shock absorption system, typically comprising of a spring, and an adjustable stroking load element, such as an adaptive energy absorber (EA) or semiactive damper element, in which the stroking load can be electronically adjusted in real-time. Typically, there is a maximum limiting stroking load that can be accommodated by a payload. Thus, a Constant Stroking Load Regulator (CSLR) is developed that accepts sensor feedback, and then selects control gains that result in the energy absorber (EA) providing the required controllable stroking load. A key benefit of this regulator is that it is capable of adapting to a varying range of payload mass, impulse types, and impulse excitation levels. The payload mass is measured and used as a control input parameter. The measured impact velocity is used to determine the impulse acceleration level by assuming an impulse profile, which tends to be application-specific. Finally, the required constant stroking load is determined using a physics-based model. The CSLR is designed to achieve a “soft landing” such the payload comes to rest when the available stroke is used completely, in order to minimize the stroking load and thereby minimize the potential for payload damage. The CSLR methodology was then experimentally validated for a representative occupant protection system consisting of a seat suspension with an adaptive stroking element, which in this case was a magnetorheological energy absorber (MREA). A MREA was used as the stroking element because its stroking load can be adjusted electronically. To validate the CSLR strategy, experimental drop tests were conducted for two different payloads. The impact velocity was 10.3 ft/s (3.15 m/s) and the acceleration profile was a 50 ms duration half-sine pulse. The constant stroking load was pre-calculated as a function of payload mass and initial velocity. During each drop test, the required stroking load was supplied to the MREA in order to achieve a “soft landing.” The CSLR was successfully demonstrated under laboratory conditions. These tests demonstrated feasibility of using the CSLR, in conjunction with a MREA as the stroking element.

Stability and Hopf Bifurcation of Impact Dynamics Considering Delay in a Semi-Active Energy Absorbing Suspension System

2011 ◽  
Author(s):  
Xiaomin Dong ◽  
Wei Hu ◽  
Miao Yu ◽  
Norman M. Wereley
Keyword(s):  
Hopf Bifurcation ◽  
Time Delay ◽  
Impact Velocity ◽  
Suspension System ◽  
Impact Dynamics ◽  
Ground Vehicles ◽  
Payload Mass ◽  
Energy Absorbers ◽  
Energy Absorbing ◽  
The Impact

In a crash event, such as the crash of an aircraft or the collision of two ground vehicles, the impact dynamics are a function of the impact velocity and payload mass. A typical bumper system on a ground vehicle has passive viscous energy absorbers (PVEAs) that are optimally designed for a specific impact velocity and payload, so that off-design performance may be suboptimal, and may even be unacceptable for large perturbations in sink rate and payload mass from the designed values. This is because the load-stroke profile of the energy absorbing suspension system (EASS) is passive in that spring stiffness and damping of the energy absorbers is fixed. Therefore, in this study, the PVEA in an EASS is replaced by an active or semi-active energy absorber (SAEA), and the effects of time delay in achieving controllable semi-active damping is analyzed in the context of impact dynamics. To accomplish this, a three degree-of-freedom dynamic model of an EASS is presented, and the effect of the time delay in commanding the controllable force of the EA is analyzed. The asymptotic stability and Hopf bifurcation of the trivial steady state response are analyzed for a range of time delay. A technique to stabilize the impact dynamic is developed, and it is shown that the impact dynamics can be stabilized using appropriate feedback control.

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.

A General Superelement Model on a Moving Reference Frame for Planar Multibody System Dynamics

1991 ◽  
Vol 113 (1) ◽  
pp. 43-49 ◽  
Author(s):  
O. P. Agrawal ◽  
R. Kumar
Keyword(s):  
Differential Equations ◽  
Reference Frame ◽  
Inverse Dynamics ◽  
Equations Of Motion ◽  
Mathematical Formulation ◽  
Computational Time ◽  
Single Degree Of Freedom ◽  
Generalized Force ◽  
Time Required ◽  
Energy Relations

This paper presents a mathematical formulation for a superelement on a moving reference frame. A group of constrained elements, forming a single degree-of-freedom with respect to some reference frame, is represented by one element. The configuration of a typical superelement is determined with respect to the reference frame using one parameter only. This reduces the number of generalized coordinates needed to define the configuration of the entire system. Energy relations and generalized force expressions are developed in terms of the reference coordinates and superelement parameters. An inverse dynamics approach is used to obtain the functions associated with a superelement. The differential equations of motion of a system consisting of one reference frame and several superelements are derived. Constraints internal to the superelements do not appear in the resulting differential equations. This reduces the dimensions of the problem and the computational time required to solutions. Two examples are considered to demonstrate the feasibility and the efficiency of the method.

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