Effective Test Procedures for Evaluating Force Characteristics of Magneto-Rheological Dampers

2003 ◽  
Author(s):  
Mehdi Ahmadian ◽  
James C. Poynor
Keyword(s):  
Relative Velocity ◽  
Test Procedure ◽  
Mr Damper ◽  
Electrical Current ◽  
Test Results ◽  
Test Procedures ◽  
Vehicle Suspensions ◽  
Mr Dampers ◽  
Magneto Rheological ◽  
Force Characteristics

This paper will provide a new test procedure for determining the force characteristics of magneto rheological (MR) dampers that are commonly used for vehicle suspensions. Force characteristics of a damper, in this case, refers to establishing the amount of force that the damper can provide at different relative velocities across the two ends of the damper, Force characteristics of a damper, which are commonly presented as a plot of force versus relative velocity—commonly known as force-velocity curve—are established in a shock (or damper) dynamometer in which one end of the damper is kept fixed and the other end is moved in a cyclical manner at a prescribed displacement and frequency. The peak damper force at each velocity is measured and plotted as discrete data points versus relative velocity across the damper. This is a well-understood and commonly used procedure for passive shock absorbers or dampers. For magneto rheological dampers, however, our study shows that such procedures do not necessarily provide an accurate assessment of the force characteristics of MR dampers in all damping conditions. The damping condition of MR dampers can be changed by a small amount of electrical current that can be provided to the damper. The inaccuracies are mainly due to the changing dynamics of the MR fluid inside the damper at different damping conditions. This paper will provide the test results for a MR damper, using the new and the conventional test procedures. The test results indicate that the use of the new test procedure will procedure will allow for an accurate representation of the MR damper force at all velocities, within the range of the currents that the damper is designed for.

Application of Magneto Rheological Dampers for Controlling Shock Loading

1999 ◽  
Author(s):  
Mehdi Ahmadian ◽  
James C. Poynor ◽  
Jason M. Gooch
Keyword(s):  
Dynamic System ◽  
Shock Loading ◽  
Closed Loop ◽  
Shock Absorber ◽  
Mr Damper ◽  
Test Results ◽  
Closed Loop System ◽  
Mr Dampers ◽  
Shock Dynamics ◽  
Magneto Rheological

Abstract This study will examine the effectiveness of magneto-rheological (MR) dampers for controlling shock dynamics. Using a system that includes a 50-caliber rifle and a magneto-rheological damper, it is experimentally shown that MR dampers can be quite effective in controlling the compromise that commonly exists between shock forces and strokes across the shock absorber mechanism. A series of tests are conducted to demonstrate that different damping forces by the MR damper can result in different shock-force/stroke profiles. The test results further show that MR dampers can be used in a closed-loop system to adjust the shock loading characteristics in a manner that fits the dynamic system constraints and requirements.

A Non Parametric Model for Magneto Rheological Dampers

1999 ◽  
Author(s):  
Mehdi Ahmadian ◽  
Xubin Song
Keyword(s):  
Test Data ◽  
Mr Damper ◽  
Parametric Model ◽  
Parametric Models ◽  
Magnetic Saturation ◽  
Mr Dampers ◽  
Electro Magnetic ◽  
Magneto Rheological ◽  
Force Characteristics ◽  
Non Parametric

Abstract A non-parametric model for magneto-rheological (MR) dampers is presented. After discussing the merits of parametric and non-parametric models for MR dampers, the test data for a MR damper is used to develop a non-parametric model. The results of the model are compared with the test data to illustrate the accuracy of the model. The comparison shows that the non-parametric model is able to accurately predict the damper force characteristics, including the damper non-linearity and electro-magnetic saturation. It is further shown that the parametric model can be numerically solved more efficiently than the parametric models.

Design and Development of Magneto Rheological Dampers for Bicycle Suspensions

1999 ◽  
Author(s):  
Mehdi Ahmadian
Keyword(s):  
Dynamic Performance ◽  
Mr Damper ◽  
Test Results ◽  
Design And Development ◽  
Damping Force ◽  
Mr Fluid ◽  
Performance Improvements ◽  
Mr Dampers ◽  
Force Velocity ◽  
Magneto Rheological

Abstract The design and fabrication of a magneto rheological (MR) damper for bicycle suspension applications is addressed. Two 1998 Judy® Dampers are retrofitted with MR valves, to achieve the damping force adjustability that the MR fluid offers. One design attempts to use as many of the Judy® Damper components as possible. The second design significantly modifies the Judy® Damper, to better accommodate the MR valve and ease of fabrication and assembly, although fitting into the same envelope as the Judy® damper for a direct retrofit. The two MR dampers are fabricated and assembled for force-velocity characterization testing. The test results show that properly-designed MR dampers can provide significant dynamic performance improvements, as compared to conventional passive bicycle dampers.

Improving Vehicle Performance and Operator Ergonomics: Commercial Application of Smart Materials and Systems

2011 ◽  
Author(s):  
Douglas Ivers ◽  
Douglas LeRoy
Keyword(s):  
Smart Materials ◽  
Mr Damper ◽  
Electrical Current ◽  
Step Response ◽  
Commercial Application ◽  
Material Technology ◽  
Mr Fluid ◽  
Mr Dampers ◽  
Magneto Rheological ◽  
Scale Step

This paper will discuss how controllable material technology, such as the use of active magneto-rheological (MR) dampers, improves vehicle primary and secondary suspensions. Although relatively new to the marketplace, semi-active suspensions in commercial automobiles and off-highway vehicles have been proven through the use of active MR dampers since 1998. In fact, MR suspension dampers are found today on the commercial vehicles of an increasing number of automotive OEMs and leading off-highway OEMs. MR fluid dampers are simple in design and have the advantage of no moving parts. The resistive force from an MR damper is generated as iron particles, suspended in the magneto-rheological fluid (MR fluid); pass through a magnetic field controlled by the electrical current passing through an electric coil contained within a moving piston surrounded by fluid. By adjusting the current to the damper coil in response to feedback from vehicle sensors and a controller, the damping response of the suspension can be optimized and controlled in real time to provide optimal operator comfort. The MR Damper System has a full-scale step response of less than 10 milliseconds. Sophisticated control algorithms adapt to large changes in payload, enabling the vehicle to meet ride metrics without pneumatic load leveling. Other benefits of the MR damping system include higher speed in NATO double-lane change tests, reduced risk of roll-over, improved accuracy of mounted weapons, and improved vehicle durability and readiness.

scholarly journals An Evaluation of Magneto Rheological Dampers for Controlling Gun Recoil Dynamics

2001 ◽  
Vol 8 (3-4) ◽  
pp. 147-155 ◽  
Author(s):  
Mehdi Ahmadian ◽  
James C. Poynor
Keyword(s):  
Closed Loop ◽  
Mr Damper ◽  
Single Shot ◽  
Test Results ◽  
Closed Loop System ◽  
Damping Force ◽  
Mr Dampers ◽  
Recoil Force ◽  
Magneto Rheological ◽  
Potential Use

The application of magneto rheological dampers for controlling recoil dynamics is examined, using a recoil demonstrator that includes a single-shot 50 caliber BMG rifle action and a MR damper. The demonstrator is selected such that it can adequately represent the velocities that commonly occur in weapons with a recoil system, and can be used for collecting data for analyzing the effects of MR dampers on recoil dynamics. The MR damper is designed so that it can work effectively at the large velocities commonly occurring in gun recoil, and also be easily adjusted to reasonably optimize the damper performance for the recoil demonstrator. The test results show that it is indeed possible to design and use MR dampers for recoil applications, which subject the damper to relative velocities far larger than the applications that such dampers have commonly been used for (i.e., vehicle applications). Further, the results indicate that the recoil force increases and the recoil stroke decreases nonlinearly with an increase in the damping force. Also of significance is the fact that the adjustability of MR dampers can be used in a closed-loop system such that the large recoil forces that commonly occur upon firing the gun are avoided and, simultaneously, the recoil stroke is reduced. This study points to the need for several areas of research including establishing the performance capabilities for MR dampers for gun recoil applications in an exact manner, and the potential use of such dampers for a fire out of battery recoil system.

A Reliability Assessment Model for MR Damper Components within a Smart Structural Control Scheme

2008 ◽  
Vol 56 ◽  
pp. 218-224
Author(s):  
Maguid H.M. Hassan
Keyword(s):  
Structural Control ◽  
Inverse Dynamics ◽  
Mr Damper ◽  
Assessment Model ◽  
Resistance Force ◽  
Mr Dampers ◽  
Control Scheme ◽  
Smart Control ◽  
Control Devices ◽  
Magneto Rheological

Smart control devices have gained a wide interest in the seismic research community in recent years. Such interest is triggered by the fact that these devices are capable of adjusting their characteristics and/or properties in order to counter act adverse effects. Magneto-Rheological (MR) dampers have emerged as one of a range of promising smart control devices, being considered for seismic applications. However, the reliability of such devices, as a component within a smart structural control scheme, still pause a viable question. In this paper, the reliability of MR dampers, employed as devices within a smart structural control system, is investigated. An integrated smart control setup is proposed for that purpose. The system comprises a smart controller, which employs a single MR damper to improve the seismic response of a single-degree-of-freedom system. The smart controller, in addition to, a model of the MR damper, is utilized in estimating the damper resistance force available to the system. On the other hand, an inverse dynamics model is utilized in evaluating the required damper resistance force necessary to maintain a predefined displacement pattern. The required and supplied forces are, then, utilized in evaluating the reliability of the MR damper. This is the first in a series of studies that aim to explore the effect of other smart control techniques such as, neural networks and neuro fuzzy controllers, on the reliability of MR dampers.

Passenger Comfort Analysis in an Automotive Considering a Magneto-Rheological Damper based Suspension

2017 ◽  
Vol 8 (4) ◽  
Author(s):  
R.B. Soujanya ◽  
D.D. Jebaseelan ◽  
S. Kannan
Keyword(s):  
Ride Comfort ◽  
Mr Damper ◽  
Nonlinear Behaviour ◽  
Passive Damping ◽  
Damping Force ◽  
The Road ◽  
Mr Dampers ◽  
Moving Vehicles ◽  
Magneto Rheological ◽  
Multi Body

Passenger’s comfort in moving vehicles depends on the quality of the ride. The major cause of discomfort is the vibration transmitted to passengers due to the road irregularities. For a comfortable ride on a vehicle, vibration must stay within prescribed standards. In the present work, an attempt was made to show that, the vibrations can be limited with the use of Magneto-rheological (MR) dampers for varying road profiles than the passive damping methods. MR dampers are semi-active control devices that use MR fluids to produce controllable damping force as they are known to exhibit nonlinear behaviour. Multi body dynamic studies were done to study the response of the system using a quarter car model. In this paper, passive damping (viscous damping) was considered at natural frequency of 1.012Hz, the response of damping was observed after 10s and the acceleration was found to be 6m/s2. When MR damper is employed as the magnetic force increases, the response of the damping was better than the passive damping, at 1.2A it comes down to 0.55m/s2, and the vibration gets dampened after 1.75s. Hence, from this study it is concluded that the MR damper can be employed in automobile for better ride comfort.

Investigation of the CoreLok for Maximum, Aggregate, and Bulk Specific Gravity Tests

2005 ◽  
Vol 1907 (1) ◽  
pp. 135-144 ◽  
Author(s):  
Gregory A. Sholar ◽  
Gale C. Page ◽  
James A. Musselman ◽  
Patrick B. Upshaw ◽  
Howard L. Moseley
Keyword(s):  
Specific Gravity ◽  
Test Procedure ◽  
High Porosity ◽  
Test Results ◽  
Test Procedures ◽  
Coarse Aggregates ◽  
Fine Aggregates ◽  
Florida Department ◽  
Plastic Bag ◽  
Apparent Reason

The Florida Department of Transportation uses long-established test procedures to determine the maximum specific gravity (Gmm) and bulk specific gravity (Gmb) of asphalt mixtures and the bulk specific gravity (Gsb) of aggregates. The CoreLok, a vacuum-sealing device that can be used to determine these properties, was evaluated by the department for these test procedures. With respect to the Gmm test procedure, for mixtures containing nonabsorptive granites, the CoreLok determined results equivalent to those of the department's test procedure. However, for mixtures containing absorptive limestones, the CoreLok determined higher Gmm values than did the department's test procedure. The apparent reason for the discrepancy is that the CoreLok does not determine a saturated surface dry condition of the sample. With respect to the aggregate specific gravity test procedures, the CoreLok provided test results equivalent to the department's test procedure for the nonabsorptive fine aggregates only. For the absorptive fine aggregates and all of the coarse aggregates, the CoreLok determined Gsb test results significantly different from those of the department's test procedures. The CoreLok may be suitable for determining Gmb for coarse-graded compacted specimens with high porosity and air voids. There are concerns with the accuracy of the CoreLok results because of the bridging effect of the plastic bag over the large surface voids and because of the CoreLok's significant underestimation of the specific gravity of a solid aluminum cylinder.

Experimental Study on Multi-Mode Vibration Control of a Stay Cable with a Passive Magnetorheological Damper

2013 ◽  
Vol 361-363 ◽  
pp. 1402-1405
Author(s):  
Zhi Hao Wang
Keyword(s):  
Vibration Control ◽  
Mr Damper ◽  
Magnetorheological Damper ◽  
Test Results ◽  
Stay Cable ◽  
Mr Dampers ◽  
Stay Cables ◽  
Modal Damping ◽  
Mode Vibration ◽  
Multi Mode

Effective vibration control technology for stay cables is extremely critical to safe operations of cable-stayed bridges. For super-long cables, passive linear damper cannot provide sufficient damping since it can be only optimum for a given mode of cable, while a long cable may vibrate with several modes. This paper focuses on multi-mode vibration control of stay cables with passive magnetorheological (MR) dampers. Firstly, a 21.6m-long model cable was designed and established in the laboratory.Then, control performance of the cable with a passive MR damper was tested. The test results show that modal damping ratios of the cable in the first four modes can be improved significantly with the MR damper. It is further demonstrated that optimal tuned passively operated MR damper can outperform the passive viscous damper.

Experimental Approach for Finding the Response Time of MR Dampers for Vehicle Applications

2003 ◽  
Author(s):  
Fernando D. Goncalves ◽  
Jeong-Hoi Koo ◽  
Mehdi Ahmadian
Keyword(s):  
Response Time ◽  
Time Constant ◽  
Constant Velocity ◽  
Mr Damper ◽  
Initial State ◽  
Final State ◽  
Mr Dampers ◽  
Automotive Suspension ◽  
Magneto Rheological ◽  
Time Required

This paper offers a method and an experimental example of determining the response time of Magneto-Rheological (MR) dampers. The response time of MR dampers for automotive suspension applications is valuable information because it is one of the key factors that determine the practical effectiveness of the use of MR dampers in vehicles. However, a detailed description of the response time of MR dampers is seldom given in the literature. Furthermore, the methods of computing the response time are not discussed in detail. Therefore, this study intends to develop a method for experimental determination of the response time of MR dampers for automotive suspensions. A triangle wave that maintains a constant velocity across the damper is proposed as the input to use in experiments. This triangle wave ensures a constant velocity across the damper in order to accurately evaluate the response time of the MR damper. The response time was defined as the time required to make the transition from the initial state to 63.2% of the final state, or one time constant. The time constant is a measure of how long it takes a system to respond to a given input. In other words, the response time is the time necessary for the damper to achieve the desired force upon activation. To demonstrate the method, the response time was found for an MR damper particularly designed and fabricated for vehicle applications. Two cases were considered: activation response time of the damper and deactivation response time of the damper. Both cases were studied during the rebound stroke of the damper. It was found that the response time of the MR damper under activation and deactivation was 15.4 ms and 13.9 ms respectively. The results are comparable to those found in the literature.

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