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Experimental and numerical investigation on magneto rheological based semi active control suspension system for vehicle on different road condition.


Ride comfort is an essential factor that determines the quality of a car. A car is designed based on lot of additional elements like safety, comfort, speed, etc. that go with its performance and durability. While the speed and performance factors of a car is affected by the engine parameters, the comfort and safety of a car is determined by the parameter known as Ride Quality. Ride quality refers to the degree of safety offered to the passengers and additional loads (cargos)in a car during a travel preventing the discomfort produced due to the bumps and ditches on the ground. Car manufacturers have grown more cautious towards the comfort and ability their product offers to the people. The key factors that determine these ride qualities are: Whole Body Vibration and Noise. Added to this is the external factor: Road Conditions. Poor ride quality and road conditions will damage the car components.

1.1 Types of Suspension Systems:

To manage the vibrations produced due to these factors and enhance the damping factor of the car, various types of suspension systems are used. They can be broadly classified into three types: Passive, Active and SemiActive [1].

A passive control system is a predetermined system with fixed level suspension. A sudden rise or fall on the driving surface that doesn't correspond to the predetermined range will not be properly damped. This control system is not compensatory and cannot adjust to the variations of a travel accordingly. An active control system is a compensatory system which adjusts according to the conditions of the road and provides a better driving experience. A smooth and defined movement of the suspension system provides proper damping and eliminates uneven vibrations and jerks of the vehicle. Active system operates over a wide range of frequencies and has online feedback while the passive suspension system operates only over a certain frequencies and doesn't have online feedback [2].

A semi-active system is a system between active and passive systems and offers an optimal performance added to its low power consumption. This system when used with MR fluid or ER fluid has an upper hand over both passive and active types. Magneto-rheological (MR) fluids are a class of smart materials created by the suspension in a carrier fluid of micron-sized particles that can be magnetized. Their rheological properties can be quickly changed in a reversible manner using an external magnetic field [3]. MR fluids are used in many industrial areas and are being increasingly considered for various applications in automotive manufacturing, biomedical equipment, large-scale seismic control devices, and in the polishing industry. A promising device, the MR damper, can offer the advantages of a large range of damping force, highly reliable operation and good robustness with a reliable fail-safe performance while consuming very little energy. Therefore, MR dampers have received significant attention for application in semi-active control systems.

2. Literature Review:

Changsheng Zhu presented a simple disk type MR fluid damper operating in shear flow model. The effect of excitation current in the coil on the magnetic flux density in the axial gap filled with the MR fluid were studied experimentally and theoretically [4]. Wang Wei and Xia Pinqi presented an adaptive control to suppress helicopter ground resonance with magneto rheological fluid. They used adaptive inverse control method to control the output damping force of the MR fluid damper [5]. Georgios Tsampardoukas investigated the use of controlled magneto rheological fluid dampers for semi-active truck suspension and employed half truck model and measured the performance through a numerical simulation approach [6]. Sadoksassi performed theoretical and experimental studies for new MR fluid damper that used for the semi-active control of automotive suspensions. The paper investigates approaches to optimizing the dynamic response and provides experimental verification. Both experimental and theoretical results have shown that, if this particular model is filled with an 'MRF 336AG' MR fluid, it can provide large controllable damping forces that require only a small amount of energy. For a magnetizing system with four coils, the damping coefficient could be increased by up to three times for an excitation current of only 2 A. Such current could be reduced to less than 1 A if the magnetizing system used eight small cores. In this case, the magnetic field will be more powerful and more regularly distributed [7]. Gokhan Aydar focused on the design, fabrication and theoretical analysis and characterization of a small magneto rheological fluid damper. They applied the MR damper for horizontal axis front loading washing machine to reduce the noise at high speed spin cycle. They reported that test results produce good agreement with design values and theoretical predictions [8].

Seung Bok Choi presented the vibration control of a semi active seat suspension with a magneto rheological fluid damper based on Bingham model for commercial vehicles such as large size trucks. They formulated a skyhook controller to reduce the vibration level at driver seat [9]. Marin presented the study of MR damper used for seismic protectors for civil structure. They reported that external force required moving the damper increases several times in the magnetic field [10]. Shawn P. Kelso presented a field controllable, semi active magneto rheological fluid damper for high pay load, off high way vehicles. They employed Bingham plastic theory to model the nonlinear behavior of the Magneto rheological fluid [11].

Umit Drogue focused on design, development and testing of a new magneto rheological fluid damper for high mobility multi-purpose wheeled vehicle. They designed a failsafe MRF damper using Bingham plastic model and the magnetic field distribution was 3D electromagnetic finite element analysis [12]. 3

3. Methodology:

3.1 Characterization of MR Fluid:

In the absence of a magnetic field, MR fluid is free flowing with a consistency similar to motor oil. The value of these fluids is realized when a magnetic field is applied; micron sized ferrous particles suspended in the fluid align parallel to the flux path, creating particle chains. Initially, the ferrous particles are in an amorphous state, when a magnetic field is applied, the ferrous particles begin to align along the flux path. The ferrous particles aligned along the flux path creating particle chains in the fluid. These particle chains resist and restrict fluid movement. As a result, a yield stress is developed in the fluid. The degree of change is related to the magnetic field strength and may occur in a matter of milliseconds.

3.2 Squeeze mode:

Squeeze mode operates when a force is applied to the plates in the same direction of a magnetic field to reduce or expand the distance between the parallel plates causing a squeeze flow. In squeeze mode, the MR fluid is subjected to dynamic (alternate between tension and compression) or static (individual tension or compression) loadings. As the magnetic field charges the particles, the particle chains formed between the walls become rigid with rapid changes in viscosity. The displacements engaged in squeeze mode are relatively very small (few millimeter's) but require large forces.


Compression is one of the mechanisms in the squeeze mode as shown in Figure3.1. The geometric arrangement for compression is accomplished by two flat parallel solid surfaces facing each other. The two surfaces are pushed towards each other by an external force, operating at right angles to both surfaces. The liquid in the gap between them is initially free to move away from this increasingly small gap, by flowing parallel to the surfaces, and collecting in a region beyond the gap. Under the presence of a magnetic field, a magnetic dipole moment of the micron-sized particles is induced, so that dipole interactions occur between the particles. The particles form chains and coordinate according to the flux paths [13]. Consequently, this formation resists and restricts the fluid movement from repositioning out of their respective flux paths. Tension in a squeeze mode is as an operational mode where two flat parallel surfaces, standing opposite to each other, are pulled apart from each other by an external force, acting along the path of the magnetic flux lines. Yield stress produced by tension mode is greater by three to four times than shear yield stress, but lower than compressive stress under the same magnetic field strength [14].

3.3 Bingham's plastic model for MR fluid suspension under squeeze mode:

MR fluids are characterized by an increase in dynamic yield stress upon application of a magnetic field. The Bingham plastic model has proven useful in modeling flow mode dampers utilizing MR fluids. However, certain MR fluids can exhibit shear thinning behavior, wherein the fluid's apparent plastic viscosity decreases at high shear rates. The Bingham plastic model does not account for such behavior, resulting in over prediction of equivalent viscous damping. We present a Bingham bi-plastic model that can account for both shear thinning and shear thickening behaviors. This approach assumes a bilinear post yield viscosity, with a critical shear rate specifying the region of high shear rate flow. Furthermore, the model introduces non-dimensional terms to account for the additional parameters associated with shear thinning and thickening. A comparison is made between Bingham plastic and Bingham bi-plastic force responses to constant velocity input, and equivalent viscous damping is examined with respect to non-dimensional parameters.

For most engineering applications a simple Bingham plastic model is effective at describing the essential, field-dependent fluid characteristics. A Bingham plastic is a non-Newtonian fluid whose yield stress must be exceeded before flow can begin [16]. Thereafter, the rate-of-shear vs. shear stress curve is linear. In this model, the total yield stress is given by [tau] = [[tau].sub.0] (H) + [eta][??] where:

[[tau].sub.0]--yield stress caused by applied magnetic field, [Pa]

H--magnetic field strength, [A/m]

[??]--shear rate, [s-1]

[eta]--plastic viscosity, [Pa x s]

3.4 Flow Mode:

A force F is applied to the damper shaft, resulting in a pressure differential AP across an annular valve in the piston head. As a result, fluid flows through the annular valve, resulting in shaft motion of velocity V0. First, it is assumed that the annular gap, d, is very small relative to the inner radius of the annulus, R, so that the annular duct may be approximated by a rectangular duct or two parallel plates. The width of the rectangular duct is denoted by b, and is related to the circumference of the centerline of the annular duct as below:

b = 2[pi](R + d/2)

A further consequence of the small gap assumption is that the velocity profile across the annular gap in response to a linear pressure gradient must be symmetric across the valve. Thus, we make the following assumptions: (1) the gap is assumed to be small relative to the annular radius (as above), (2) the fluid is in compressible; (3) the flow is fully developed along the entire finite active length of the valve, that is, the length over which the field is applied, so that we assume a 1-D problem; (4) the flow is assumed to be steady or quasi steady, so that acceleration terms can be neglected; (5) a linear (shaft) axial pressure gradient is assumed, so that the pressure gradient is the pressure drop, AP, over the length of the valve, L. Therefore, we use a simplified form of the governing equation for Poiseuille flow in a rectangular duct as below (Wereley and Pang, 1998).

dr/dy = -[DELTA]p/L

where, [DELTA]p = pin--pout, here pin and pout are the pressure in and pressure out of the MR valve respectively.

3.5 Bingham Plastic Flow:

A Bingham plastic material is characterized by a dynamic yield stress, Ty. According to the idealized Bingham plastic constitutive relationship, if the shear stress is less than the dynamic yield stress, then the fluid is in the preyield condition. In this preyield condition the fluid is assumed to be a rigid material. Shearing does not occur until the local shear stress, t, exceeds the dynamic yield stress, [tau]y. Once the local shear stress exceeds the dynamic yield stress, the material flows with a plastic viscosity of p. Therefore, the postyield shear stress can be expressed as

[tau] = [[tau].sub.y] sin (du/dy) + [mu] (du/dy)

Thus, a Newtonian fluid can be viewed as a Binghamplastic material with a dynamic yield stress of zero [15]. For an MR fluid, the dynamic yield stress can be approximated by a power law function of the magnetic field.

Two distinct flow regions arise. The central plug region, is characterized by the local shear stress being less than the fluid yield stress [tau]y, so that the shear rate or velocity gradient is zero. This width of the pre yield region is denoted by the plug thickness, [delta], which is non-dimensionalized with respect to the gap between the two parallel plates of the valve as

[bar.[delta]] = 2L[[tau].sub.y]/d[DELTA]p

The second region is the post yield region where the local shear stress is greater than the yield stress of the fluid. The velocity profile for Bingham plastic flow between parallel plates with uniform field is (Wereley and Pang, 1998)


The total Bingham plastic volume flux is


Equating the volume flux displaced by the piston head to that through the annular duct, leads to F = [C.sub.eq][v.sub.0]

Where the equivalent viscous damping is given by

[C.sub.eq] = 1/[(1 - [bar.[delta]]).sup.2] + (1 + [bar.[delta]]/2)

4. Mr Fluid Damper


To investigate the suspension effects of MR fluid, a new damper is developed. The developed design consists of the following components: twin tube damper with a two way return valve fitted at the bottom of the inner tube. A cylindrical solenoid coil wounded over the inner tube which acts as a DC magnet; a piston attached to the inner tube which provides the reciprocating damping motion. The total system is enclosed by an oil seal and a bush at the top of the damper. The schematic and fabricated model of the MR fluid damper is shown in Figure 4.1.

The MR fluid contains MR fluid, bearing, seal and annular orifice, coil, diaphragm and accumulator. For accumulator, there is a nitrogen gas at 20 bar pressure acting on the damper. The diaphragm used to separate the nitrogen and MR fluid. Also the coil produces the electromagnetic field by the current passing through it. The bearing and the seal in used to prevent the friction. The MR fluid valves and associated magnetic circuit are fully contained with the piston. These magnetically controlled valves regulated.

5. Model Of A Car Suspension System:

The model of a vehicle is represented with multiple degrees of freedom in a vibration system which is shown in Figure 5.1. A vehicle model consist of a two degrees of freedom, the vehicle mass with passenger is represented by the sprung mass (ms) and the mass of wheel and associated components are represented by an unsprung mass (mu). The suspension spring constant (Ks) and tire spring constant (Kt).

The vehicle dynamic characteristic of a car suspension system depends upon accelerating, braking and steering forces. These forces as it impacts the suspension of a car cause vibrations. When a car moves over a bump, the suspension spring is compressed producing a Jounce effect and as it returns over the neutral position carrying the return stroke energy it gets restored which is called as Rebound. These effects initiate's vibrations. The present study deals with the continuous damping of vibrations by shock absorbers with the use of MR fluid damper.


5.1 Experimental Setup:

An experiment has been carried out as on-road approach. The set up consists of a normal and MR fluid shock absorbers. The shock absorbers are fitted individually on the controller arm of the chasse frame. Accelerometer is mounted on the suspension frame which senses the vibration that occurs during the travel. S-type load cell is attached on the shock absorber which senses the load impact signal during travel. Displacement transducer is attached on the shock absorber which senses the deformation of the damper. GPS system is attached on the Maruti 800 car for evaluating the direction of road profile and travelling velocity. The total test arrangement is shown in Figure 5.2. The sensors are connected to a DAQ system which is used for signal conditioning (converting analog to digital). The signals are processed using Dewesoft software through a PC which is connected to the DAQ system. The instrumentation details are shown in Table 5.1. Tests were conducted by selecting the three road profiles. They are continuous speed braker, sand road and plain road. The dynamic characteristics have been studied for normal suspension and MR fluid suspension for those selected road profile. The output signals from the sensors have been recorded in the DAQ system.

A linear variable potentiometer was used to measure the displacement of the piston rod of the MR damper and a load cell with a range of 1000 kg was included in series with the damper to measure the output force. The data acquisition system employed consisted mainly of a PC and the Dewesoft software. Using this experimental setup, the response of the damper is be measured for a wide range of prescribed speeds. Data signals were acquired with the help of Dewesoft software. Test damping characteristics of a vehicle were tested at different road conditions like, continuous speed breaker, sand road and plane road at various ranges of speed conditions.





5.2 Controller Circuit for System Automation of MR Fluid Damper:

A controller circuit as shown in the Figure 5.3 and 5.4 is attached to the MR fluid damper to control the flow of current from a D.C battery source into the solenoid coil as shown in Figure. 2. This varies the viscosity of MR fluid according to Bingham's Plastic Theory depending upon shear rate of the fluid [14].



6. Results Of Mr Fluid Damper:

Figure 6.1 to 6.3 presents time responses of the MR suspension system for the continuous speed breaker excitation, sand road excitation and plain road excitation. It is generally known that the force, displacements, acceleration of sprung mass, velocity are used to evaluate ride comfort and road holding of the vehicle, respectively. It is seen that the vertical and pitch displacements, acceleration of sprung mass, and tire deflection are substantially reduced by employing the controlled current determined from the controller.




Figure 6.1 displays the system responses for the ride comfort criteria with vehicle speed of 20 km/hr over speed breaker input. From the Figure 6.1, in the controlled system, the displacement of the vehicle body is reduced. It shows that the reduced peek of overshoot than the passive damper. Unwanted vibrations induced by the speed breaker have been well reduced by implementing the MR damper.

For continuous speed breaker input, the transient responses for vehicle ride comfort performance criteria over the conventional passive is increased by controllable MR damper.

From the Figure 6.2, for sand road excitation, acceleration is found to be reduced for MR fluid damper. Its value ranges from -7.41g to 4.78g for MR fluid damper and -16.31g to 16.77g for normal damper. This is due to the viscous variation of MR fluid which damps the acceleration more effectively than passive damper. Displacement curves suggest that MR fluid damper attains a uniform stroke rate when compared to passive damper which varies drastically as the bounce and rebound effects are controlled by the shear rate of the flow fluid.

Output of the plain road excitations are portrayed in the Figure 6.3 Acceleration is reduced by 6% with respect to the time at a speed of 40 km/hr by using the MR damper suspension system. Alsoit clearly depicts the travel velocity which is having very less deviation among the dampers as the tests were taken on individual set ups at different time which is shown in the velocity graph.


A quarter car suspension systems with MR damper has been investigated and compared with passive system. For vehicle vibration control, a model-reference flow mode controller has been used as a system controller and a continuous control strategy has been designed to adjust the MR damper control signal. A mathematical model of MR damper is adopted. For vibration control of the car suspension system, relay circuit is used for system controller and the damper controller is used to adjust the appropriate input voltage to the MR damper. The characteristics of the car suspension system under three road excitations have been evaluated through experimental values. Based on results achieved, the following conclusions have been drawn.

The control results presented in Figure 6.1 to Figure 6.3 indicates that both ride comfort and steering stability of a vehicle system can be substantially improved by employing the proposed semi-active MR suspension.

For continuous speed breaker, the displacement of the vehicle body is reduced and the settling time is faster comparing to passive system (constant voltage input 0 V). For sand road excitation, the suspension system with controlled MR damper can significantly reduce both mean amplitude, acceleration and the displacement as compared to the passive damper (0V). Itis noted that the power consumption of the controlled MR damper is much less that of the passive system with constant voltage.

The results presented in this paper show the good efficiency of MR fluid vibration damping within the full range of excitation frequencies occurring while driving a Maruti 800 car.

Research and Development on MR fluid and their application based devices are increasing now days. Also MR fluid technology has moved out of the laboratory and into viable commercial applications for a diverse spectrum of products. MR fluid damper offers application in the field of Civil engineering for seismic result control and also offers advancements in medical engineering.


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[3.] De Vicente, J., Klingenberg Dj and R. Hidalgo-Alvarez, 2011. "Magneto rheological Fluids: A Review", Soft Matter, 7: 3701.

[4.] Changsheng Zhu, 2005. "A Disk-Type Magneto-Rheological Fluid Damper for Rotor System Vibration Control", Journal of Sound and Vibration, 283: 1051-1069.

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(1) K.G. Saravanan, (2) N. Mohanasundara Raju, (3) P. Kumaravel

(1) Asst. Professor, Dept of Mech Engg, Sona College of Technology, Salem, India.

(2) Principal, Mahendra Institute of Technology Namakkal, India.

(3) Asst. Professor, Dept of Mech Engg, Sona College of Technology, Salem, India.

Received 25 April 2016; Accepted 28 May 2016; Available 5 June 2016

Address For Correspondence:

K.G. Saravanan, Asst. Professor, Dept of Mech Engg, Sona College of Technology,

Salem, India.

Table 3.1: Properties of MR Fluid

Property                   Typical values

Initial Viscosity          0.2-0.5 [Pa s] (at 25 C)
Density                    3-4 [g/cm 3]
Magnetic Field Strength    150-250 [kA/m]
Yield Point                50-100 [kPa]
Reaction Time              15-25 ms
Work Temperature           50 to 150 C
Typical Supply Voltage     2-25 V

Table 5: 1 Instruments Used in this study

Sl.No.   Instruments Used                     Range
1        Opkon Linear Potentio Meter (ELPT)   0 to 300mm stroke
2        S-Type Load Cell                     0-1000 Kg
3        Dewetron DAQ System (DEWE-501)       100 Ks/s channel
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Author:Saravanan, K.G.; Raju, N. Mohanasundara; Kumaravel, P.
Publication:Advances in Natural and Applied Sciences
Date:May 30, 2016
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