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Journal of Critical Reviews

ISSN- 2394-5125 Vol 7, Issue 14, 2020

MODIFICATION AND SIMULATION OF DOUBLE WISHBONE FRONT SUSPENSION IN SAFARI SUV

P. Ashoka Varthanan1, N. Jayasuriya2, V.Gowtham3

1, 2 Mechanical Engineering Department, Sri Krishna College of Engineering and Technology, Coimbatore – 641008, India, Email: [email protected] 3 Global Cylinder Managers, Wilhelmsen Group, USA

Received: 08.04.2020 Revised: 10.05.2020 Accepted: 05.06.2020

Abstract Suspension is an indispensable element in automobile. Suspensions provide a safe and comfortable ride to the passengers. In this present work, a case study of existing double wishbone suspension and its application in sport utility (SUV) is done. The existing design of suspension in SUV produces more wear and decreases the life of the suspension parts. It also leads to reduction in the comfort of the passenger(s). A new design for the suspension mechanism is developed by altering the parameters of the existing safari dicor SUV’s double wishbone mechanism of suspension. Dynamic analysis was performed on the original SUV’s double wishbone suspension and the modified double swing mechanism of suspension. Roll angle at the centre of the and the vertical displacement of the wheels during cornering were calculated from the analysis. A comparison is made between the original design and modified design to validate the best design.

Keywords: Double wishbone suspension, double swing suspension, dynamic analysis, suspension system

© 2020 by Advance Scientific Research. This is an open-access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) DOI: http://dx.doi.org/10.31838/jcr.07.14.27

INTRODUCTION analysis using ADAMS software package. Stefano et al [7] The mechanism of suspension system connects the body designed and developed a double wishbone front suspension to the . The primary purpose of the suspension system system for vineyard-orchard tractor. Orlande and Chace [8] is to produce vertical deceleration of the car body and ensure evaluated speed, economy and accuracy of various computer ride comfort. Suspension is the term given to the system of software in determining load and displacement of the springs, shock absorbers and linkages that connects a vehicle suspension system of Chervrolet Malibu. Bael at al [9] to its wheels and allows relative motion between the two [1]. studied the influence of various hard points on the functional The automobile suspension takes up shocks and requirements like steer ability, vehicle handling by during the ride from the ride surface and provides the developing axiomatic design and performance analysis on passengers a comfortable travel. Suspension system different types of suspension. Jagirdar et al [10] executed prevents the being damaged due to bumps and multi body analysis using ADAMS software on double potholes in ride surface [2]. The suspension system also wishbone suspension made up of double coil with serves to keep the in contact with road by providing twin damper configuration for military . William and reactive force in all ride surfaces [3]. Vehicle suspension Douglas discussed the various aspects of the suspension system must provide good handing performance and good systems and for a race car[11]. control during manoeuvring. It should ensure correct response of the vehicle to the control forces during In this present work, an exhaustive case study of safari dicor braking and acceleration [4]. The different suspension SUV’s double wishbone suspension is done. The drawbacks systems used in commercial automobiles are Double of the double wish bone suspension are rectified by Wishbone, Macpherson , , Torsion Rod, Semi incorporating design changes to the existing double wish trailing arm, Swing . bone suspension. Dynamic analysis is performed on both the original double wishbone suspension and modified double A variety of high class vehicles such as BMW X5, Benz M- wishbone suspension (double swing suspension) to Class, and Audi Q7 make use of double wise- bone determine the roll characteristics on right and left wheel of suspension. Zhen Zhang and Junhui [4] stated that a double the vehicle during cornering. wishbone suspension consists of upper and lower arms, swivel pin, spring, damper and a wheel. The double DESIGN METHODOLOGY wishbone type suspension system is also used in commercial Mechanism SUV’s. One end of the arms of double wishbone suspension is The double swing mechanism works similar to parallel attached to the vehicle’s chassis and the other end of the two unequal double wishbone suspension. The upper and lower links is connected to wheels of the vehicle. These two links arms of suspension are of different length and are parallel to behaves as rocker arm which oscillates about the fixed point. each other. This mechanism has four links as shown in The force produced during the suspension movement is Figure 1. This mechanism has one fixed link and two links acted in the wheels of the vehicle which forms the fourth link connecting the fixed link. Both the connecting links acts as of the mechanism. The upper and lower arm are connected rocker arm, which oscillates about fixed point. The fourth to the wheel using and they are connected to the link is connected to the connecting links at the other end chassis of the vehicle by using screw and bolt joint. through which the force acts. Link BC shown in fig 1 is the fourth link which represents the of the vehicle through Hazem Ali Attia [5] performed dynamic analysis of the which forces act on the vehicle. Link CB is the connecting link double wishbone suspension by using point-joint coordinate which makes up the lower arm. Link AB is also a connecting formulation to produce an equivalent constrained system of link which makes up the upper arm. Link AD is the fixed link particles and used particle dynamics laws to obtain the laws and the chassis of the vehicle. of motion. XiaobinNing et al [6] determined the ride comfort on different vehicles by carrying out kinematic and dynamic

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MODIFICATION AND SIMULATION OF DOUBLE WISHBONE FRONT SUSPENSION IN SAFARI SUV

Fig. 1: Double Swing Mechanism in 2D sketch of the CATIA Software

The proper functioning of the double swing mechanism can mechanism only when the links undergo constrained motion. only be achieved if the lengths of the links are in the The links should not be a rigid structure instead it should following order provide a motion when forces act on the link. The Grubler’s BC

Fig. 2: Equivalent Kinematic diagram for double swing mechanism

Geometry The double swing mechanism of suspension system is a type same for the double swing suspension and the values are not of parallel unequal double wishbone suspension. The double changed from the double wishbone suspension. The double swing suspension has upper arm and lower arm of different wishbone suspension is changed to double swing suspension length and same inclination. Unlike the existing double by changing the inclinations and lengths of upper and lower wishbone suspension, double swing suspension has the arms of the suspension. The table 1 compares the modified upper and lower arms of almost same angles of inclination. dimensions of double swing suspension with the original The parameters such as Kingpin Inclination, angles, dimensions of the safari SUV double wishbone suspension. , and are kept as

Table 1Geometry modifications done on double wishbone suspension Double wishbone Double swing suspension suspension Upper arm inclination 23.5deg 12deg Lower arm inclination 9.2 deg 12.1deg

The major changes from original double wishbone design are from 23.5deg to 12deg i.e. in the case of height change it is the Lower Arm inclination which is changed from 9.2deg to 44.5mm lower than it was before. 12.1deg i.e. in the case of height change it is 19mm higher than it was before. Upper arm inclination which is changed

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MODIFICATION AND SIMULATION OF DOUBLE WISHBONE FRONT SUSPENSION IN SAFARI SUV

Roll centre turning moment. The roll centre of the existing safari SUV is The basic parameter in a suspension design is the roll centre below the ground. (RC). Roll centre of a vehicle is a precise and distinct imaginary point in the vehicle which is obtained from the The large distance between the centre of gravity (CG) and geometry of the suspension. The cornering forces of the roll centre of the vehicle gives rise to large turning moment suspension are reacted by the self-weight of the car at the during cornering. The suspension system is designed to have roll centre. The car rolls about the roll centre at the time of a high of the vehicle. Being a SUV, the distance cornering. The position of roll centre is very important in the between the CG and RC of safari is very large than the actual design of suspension system. Roll centre acts as a fulcrum difference. The values of CG and RC for the original and point about which a turning moment is produced by the modified suspension are given in table 2. The optimum RC cornering forces which act through the centre of gravity height should be 15- 30% of the CG height. during cornering. The vehicle experiences a roll due to the

Table 2 Parameters of double wishbone and double swing suspension Double wishbone Double swing

suspension (mm) suspension (mm) Centre of gravity (GC) 762(above ground) 762(above ground) 161.2(above Roll Centre (RC) 206 (below ground) ground)

The original vehicle with double wishbone mechanism of suspension system of double swing mechanism produces suspension system has roll centre below the ground because less turning forces during corning than double wishbone of the geometry of the upper arm and lower arm. The length suspension. of upper arm is unequal to the lower arm and both the arms inclination is different. The upper arm and lower arm of the MODELLING OF THE SUSPENSION double wishbone suspension are unparallel. Therefore, the The double wishbone type suspension and modified double difference in height between RC and CG is 127% of the CG in wishbone type suspension for the safari SUV are modelled double wishbone suspension system. The high difference of using a commercial suspension analysis software package height gives rise to large turning moment during cornering. ADAMS. The default template in the software is used to The vehicle using double swing mechanism has roll centre model the double wishbone suspension. The parameters like above the ground because of the geometry of the upper arm arm inclination, arm length and arm height are fed as input. and lower arm. The length of upper arm is lesser than the Other constant parameters like Kingpin inclination, Toe lower arm and both the arms inclination is nearly same. The angles, Camber angle, Caster angle and scrub radius are also upper arm and lower arm of the double swing suspension entered into the software. The hard points of the double are parallel. Therefore, the modified suspension with double wishbone suspension are also given as input to the software swing mechanism has a very low difference in height as shown in fig 3. The model of the front suspension is between RC and CG, which is 20% of CG height. The obtained as shown in the figs 4 and 5.

Fig. 3: The hard point values of the original safari double wishbone type suspension

Fig. 4: The Front view of the original SUV Suspension in ADAMS Software

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Fig. 5: The Isometric view of the original SUV Suspension in ADAMS Software

The default template in the software which is used to model inclination, Toe angles, Camber angle, Caster angle and scrub the double wishbone suspension is also used to model the radius are taken from the previous design. The hard points of double swing suspension. The parameters like arms the modified double swing suspension are fed as input to the inclination, arm length and arm height are changed to make software as shown in fig 6. The model of the front suspension the double wishbone suspension as double swing is also obtained as shown in the figs 7and 8. suspension. Other constant parameters like Kingpin

Fig. 6: The hard point values of the modified safari double swing type suspension

Fig. 7: The Front View of the modified SUV Suspension in ADAMS Software

Fig. 8: The Isometric View of the modified SUV Suspension in ADAMS Software

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SIMULATION calculated by assuming the centrifugal force, speed of the The double wishbone mechanism for the safari suspension is vehicle during turn, mass of the vehicle, radius of turn, assembled to form the complete front wheel assembly with cornering force, height of centre of gravity and width. steering arm and the hard points for the suspension Based on the assumptions, the load on left wheel during assembly are provided in the ADAMS software. The cornering is given by 1446* Cos (time). The load on right assembled front suspension is shown in Figs 9 and 10. The wheel during cornering is given by the equation 3375 *Sin dynamic analysis is performed on the front wheel assembly. (time). These loads are not exact values since some factors The dynamic analysis is performed for the duration of 4 like gyroscopic couple, type of tire, amount of slip in tires, seconds in an interactive mode of simulation. The total acceleration/ braking forces and road on which the vehicle is number of increments for the analysis is 200. The load on the travelling are not taken into account. left and right front wheel assembly during cornering is

Fig. 9: Front view of the original SUV Suspension Assembly in ADAMS Software

Fig. 10: Isometric view of the original SUV Suspension Assembly in ADAMS Software

The modified double wishbone mechanism for the safari 3. The same magnitude of force is acting on left and right suspension is assembled to form the complete front wheel wheel while using modified double wishbone suspension. assembly with steering arm by providing the hard points for The dynamic analysis is performed for the duration of 4 the suspension assembly in ADAMS software. The assembled seconds in an interactive mode of simulation. The total front suspension in the software is shown in Figs 11 and 12. number of increments for the analysis is 200. These loads are The dynamic analysis is performed on the front wheel not exact values since some factors like gyroscopic couple, assembly. The force on the left and right wheels during type of tire, amount of slip in tire, acceleration braking forces cornering are calculated using the same parameters which and road on which the vehicle is travelling are not taken into are used for double wishbone suspension as shown in table account.

Fig. 11: The Front view of the Modified SUV Suspension Assembly in ADAMS Software

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MODIFICATION AND SIMULATION OF DOUBLE WISHBONE FRONT SUSPENSION IN SAFARI SUV

Fig. 12: The Isometric view of the Modified SUV Suspension Assembly in ADAMS Software

DESIGN METHODOLOGY Original Safari suspension Dynamic analysis was performed on the wheel assembly cornering is taken as the response parameter. The dynamic developed using original safari suspension. The roll analysis performed on the ADAMS software is shown in fig experienced by the left and the right wheel during the 13.

Fig. 13: Suspension analysis of original safari’s double wishbone suspension

The roll angle measured at the centre of the wheels (as in fig suspension undergoes cyclic load due to cyclic change of roll 14) shows that the roll angle increases steadily from 0 deg to angle. Cyclic load increases the amount of stress and 1 deg and then at 1.5 sec there is a sudden drop in the roll increases fatigue condition. The original safari suspension angle. From 1.5 sec the roll angle decreases nonlinearly to - leads to a more increased wear and decreases the life time of 0.5 deg. The roll angle again starts to increase nonlinearly wheels and wheel assembly from 3.5 sec to 5.5 sec. The suspension with original safari

Fig. 14: Roll angle measured at the wheel centre

The vertical travel of the right wheel during cornering is displacement reaches a maximum value at 1.5 sec. Then the shown in the fig 15. The vertical displacement of the right curve starts to decrease and reaches a minimum value of - wheel increases in a nonlinear parabolic form. The vertical 10mm from the ground. The curve then again starts to

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increase from 3.5sec in a parabolic form. The original safari stress and increases fatigue condition. The original safari suspension undergoes cyclic load due to cyclic change of suspension leads to a more increased wear and decreases vertical displacement. Cyclic load increases the amount of the life time of wheels and wheel assembly

Fig. 15: Vertical travel of the right wheel

Modified Double wishbone suspension Dynamic analysis was performed on the wheel assembly cornering is taken as the response parameter. The dynamic developed using modified safari suspension. The roll analysis performed on the ADAMS software is shown in fig experienced by the left and the right wheel during the 16.

Fig. 16: Suspension analysis of modified SUV’s double wishbone suspension

The roll angle measured at the centre of the wheels (in fig roll angle. Unidirectional load produces less amount of stress 17) shows that the roll angle decreases steadily from -0.5 deg and lesser fatigue condition than cyclic load as in case of to -1.25 deg and then at 1.25 sec there is a gradual increase original safari suspension. The modified safari suspension in the roll angle. From 1.25 sec, the roll angle increases leads to a less wear and increases the life time of wheels and parabolically and reaches a maximum value of 0.5 deg. The wheel assembly when compared with the original double modified safari suspension undergoes unidirectional load wishbone suspension. and the range of unidirectional load is due to cyclic change of

Fig. 17: Roll angle measured at the wheel centre

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MODIFICATION AND SIMULATION OF DOUBLE WISHBONE FRONT SUSPENSION IN SAFARI SUV

The vertical distance travelled by the right wheel during undergoes unidirectional load and range of unidirectional cornering is measured and shown in fig 18. It shows that the load is due to cyclic change of roll angle. Unidirectional load vertical distance travelled decreases steadily from -15 mm to produces less amount of stress and lesser fatigue condition -45 mm and then at 1.75 sec there is a gradual increase in the than cyclic load as in case of original safari suspension. The vertical distance. From 1.75 sec the vertical displacement modified safari suspension leads to a less wear and increases increases parabolically and reaches a maximum value of - the life time of wheels and wheel assembly when compared 25mm. The suspension with modified safari suspension with the original double wishbone suspension.

Fig. 18: Vertical travel of the right wheel

CONCLUSION Michigan, Feb 28- Mar 4, 1977. The original safari suspension with double wishbone 9. Oliveri, F., Bonsignore, C., Musumeci, I., Murabito, P., mechanism has a large distance between roll centre and Scollo, S., La Rosa, V., Terminella, A., Cusumano, G., Sofia, centre of gravity. This distance is not suitable for a V., Astuto, M.Arteriovenous Malformation Pulmonary comfortable ride. It also gives rise to cyclic load of large (AVM) in a Post-Cesarean Woman: Intensive Care and magnitude, which decreases the life time of car parts by Urgent Surgery Operation(2018) European Journal of increasing the fatigue factors. The modified safari suspension Molecular and Clinical Medicine, 5 (1), pp. 46-50. DOI: with double swing mechanism has lesser distance between 10.5334/ejmcm.257 roll centre and centre of gravity, i.e., only 20% of CG. It gives 10. Jagirdar VV, Dadar MS, Sulakhe VP. Wishbone Structure rise to unidirectional load of less magnitude which increases for Front of a Military . the life time of car by decreasing the induced fatigue, Defence Science Journal 2010; 60: 178-183. relatively. Therefore, the double swing mechanism can be 11. William F. Milliken, Douglas L. Milliken. Race car Vehicle used for safari suspension instead of double wishbone dynamics. 1994, Chapter 4, SAE International. suspension.

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