The Vehicle Dynamics Engineering Essay

This paper covers the basic constructs of suspension system and its frame design. The suspension subdivision addresses the basic design parametric quantities of the present specific suspension systems like Hydro-electric, Electro – magnetic suspension systems. The design subdivision gives a brief overview of the design and methodological analysis used in these suspensions. In this instance survey, demonstrated an understanding significance of the Suspension system types, design demands and its stuffs. The typical values for suspension features based on geometry and conformity to be discussed in relation to the interaction with the Surs and the kineticss of the complete vehicle.

In today ‘s universe, now understood by everyone the importance of Automobile. An car plays a critical function in our day-to-day life. One of the first things we are bound to detect is how the vehicle differs from other vehicle in this competitory car industry. If the vehicle rides swimmingly that can recognition a good suspension system. Following to the engine, the most of import portion of a auto is the suspension system. The suspension system maps to restrict the impact of a peculiar route status to the riders. The easiness by which we drive the auto, the rapid acceleration to sudden Michigans and tight cornering are all handled by a really efficient suspension system. ( Ref.1.R. Kayne )

A Suspension system consists of springs, daze absorbers and linkages that connect a vehicle to its wheels. Suspension systems serve the two double intents. It helps in maintaining vehicle residents comfy and moderately good associated from route noise, bumps and quivers. The design of forepart and rear suspensions of an automotive may be different for a vehicle. A typical Front wheel suspension system of the auto shown in Fig.1

Fig. 1 front wheel suspension system of the auto

The suspension of a auto is really portion of the human body, which comprises all of the of import systems located beneath the auto ‘s organic structure.

These systems include:

The frame – structural, load-carrying constituent that supports the auto ‘s engine and organic structure, which are in bend supported by the suspension

The suspension system – apparatus that supports weight, absorbs and dampens daze and helps keep tyre contact

The guidance system – mechanism that enables the driver to steer and direct the vehicle

The tyres and wheels – constituents that make vehicle gesture possible by manner of clasp and/or clash with the route

So the suspension is merely one of the major systems in any vehicle. The three cardinal constituents of any suspension: springs, dampers and anti-sway bars. Shown in fig2

Fig.2 anti-sway bars and springs

SUSPENSION SYSTEM FUNCTION

Suspension system maps are to supply perpendicular conformity so the wheels can follow an uneven road/terrain, therefore insulating the human body from induced forces and quiver. Suspension maintains the wheels in the proper tip and camber attitudes to the route surface. React to the control forces produced by the tires-longitudinal ( acceleration and braking ) forces, sidelong ( cornering ) forces, and braking and driving torsions. Resist axial rotation of the human body. Keep the tyres in contact with the route with minimum burden fluctuations. Achieving these functional aims may be attempted through geometric suspension Design and/or through active suspension methods. ( Ref.6.R.G. Longoria )

TYPES OF SUSPENSIONS

There are assorted types of suspension systems used in automotive industry. By and large all the suspension system autumn in to either of two groups dependent and independent suspensions. Both groups are functionally different and has categorization based on forepart and rear suspension. The design of suspension assorted harmonizing to the nature of vehicle thrust ( front and rear ) .

Types: Conventional, Independent, Air suspension, Hydro elastic, Electromagnetic suspension.

Here suspension parts are discussed and noted as springs and dampers parts plays a critical function in operation, so given elaborate description follows

Spring AND DAMPER THEORY

The suspension of a vehicle can be considered as a basic two mass, two spring systems the primary mass is the organic structure shell with all its mechanical constituents. It is supported by the primary spring ‘s medium which today is most frequently a set of coiling, changeless rate spiral spring. The secondary mass is all made of single multitudes of the unsprung constituents of the suspension, thrust, interrupting and maneuvering systems. They are isolated from the route surface by the Surs which act as secondary spring.

Spring ever considered with energy so given some typical values of parts

Typical energy capacities ( Nm/kg ) of spring parts

Leaf spring 50, Torsion saloon 200, Coil spring 200, Rubber cone 375, Hydrolastic gum elastic 750,

Gas spring 1500 ( Bibliography Ref.1 Geoffrey P.Howard )

Dampers:

In pattern muffling exists in three signifiers: clash syrupy and that due to the force per unit area of air. Ignoring the by and large little difference between inactive and dynamic clash. Clash in a suspension is harmful because until a distressing forces exceeds the inactive clash of the damper and no suspension motion occur and the forces is passed on to the sprung portion of the vehicle. This force is a consequence of an obstructor which deflects the Sur and for a given bump the Sur rate determines the magnitude of the force. ( Bib 1.page 55.donold bestow & A ; GH )

Apart from hydro-pneumatic and hydro elastic suspension, in which stop move the fluid, hydraulic dampers depend upon Piston working in cylinders for developing the force per unit areas necessary to supply the damping forces.

Research and Analysis on ACTIVE SUSPENSIONS like Hydro and electromagnetic suspension system

Analysis ON SUSPENSION SYSTEM

In my analysis, assorted suspension systems of the automotive have different characteristics and intents. So one have researched two major suspensions are HYDRAULIC and ELECTRO-MAGNETIC.my analysis follows brief description of both suspensions and difference between them. Electro-magnetic suspension is new one and it has alone characteristics and hydraulic suspensions utilizing assorted vehicles in autos are 2002 Nissan altima, 2006 Bmw Z4Si ( Ref.7.web )

HYDRAULIC SUSPENSION SYSTEM

Hydraulic Suspension or “ Fluid mechanicss ” for short is another signifier of suspension apparatus for modern twenty-four hours route vehicles. This suspension uses four independent dampers filled with Hydraulic fluid which are controlled by a chief control unit, usually found inside the vehicle. ( Shown Fig 3 ) . The four dampers in the Hydraulic System are separately controlled by a chief control unit which allows each damper to be pressurized and de-pressurised to let a sudden up and down motion at the flick of a switch.

Advantage of this suspension system is that when back left prance is to the full down the back right could be to the full up and the forepart two half up or half down. And

aˆ? Very high force denseness,

aˆ? easiness of control,

aˆ? easiness of design,

aˆ? Commercial handiness of the assorted parts,

aˆ? Reliability

Fig 3. Hydraulic suspension system

The chief disadvantages of the hydraulic system are:

aˆ? Considered inefficient due to the required continuously pressurized system,

aˆ? Relatively high system clip changeless ( force per unit area loss and flexible hosieries ) ,

aˆ? Environmental pollution due to hose leaks and ruptures, where hydraulic fluids are toxic,

aˆ? Mass and intractable infinite demands of the entire system including supply system albeit

That it chiefly contributes to the sprung mass.

Due to the high force denseness, easiness of design, adulthood of engineering and commercial handiness of the assorted parts in suspension, hydraulic systems are used in organic structure control systems.

ELECTROMAGNETIC SYSTEMS

An electromagnetic suspension system could meet the disadvantages of a hydraulic system due to the comparatively high bandwidth ( 10s of Hz ) , no demand for uninterrupted power, easiness of control and absence of fluids. Linear gesture can be achieved by an electric traffic circle motor

with a ball-screw or other transducer to transform the rotary gesture to linear interlingual rendition. However, the mechanism required to do this transition introduces important complications to the system. These complications include backlash and increased mass of the

traveling portion due to linking transducers or cogwheels that convert rotary gesture to linear gesture ( enabling active suspension ) . More of import that they besides introduce an infinite inactiveness and hence, a series suspension, e.g. where the electro-magnetic propulsion is represented by a rotary motor connected to a ball-screw bearing is preferred. These direct-drive electro-magnetic systems are more suitable to a parallel suspension, where the inactiveness of the actuator is minimized. FIGURE.4

( ELECTROMAGNETIC SUSPENSION SYSTEM )

Compared to hydraulic actuators, the chief advantages of electro-magnetic actuators are:

aˆ? Improved dynamic behavior,

aˆ? Stability betterment,

aˆ? Accurate force control and

aˆ? Dual operation of the actuator.

And the disadvantage is:

aˆ? Increased volume of the suspension, since the force denseness of the active portion of fluid mechanicss is higher than for electro-magnetic propulsion, i.e. system mass and volume could be less.

( Journal 2. A S S )

SUSPENSION GEOMETRY

Toe scene: This is an angle steps between longitudinal axis and auto. It can be measured at certain degree where both left and right wheel rims at centreline degree blow shown figure of theoretical account. Figure.5

toe.jpg

( TOE-IN AND TOE OUT )

Figure.5 Ref.http: //www.rockcrawler.com/techreports/glossary/index.asp

Caster angle and mechanical trail: A steered wheel is arranged to drag by a little angle and forward motion gives a stabilizing consequence. Figure.6

caster.jpg

( CASTER ANGLE )

Figure.6 Ref.http: //www.rockcrawler.com/techreports/glossary/index.asp

Camber angle: this is an angle between perpendicular and a plane of wheel. The mark positive when top of wheel learns out. Opposite for negative mark that is top tilts in Figure.7

camber.jpg

( CAMBER ANGLE )

Figure.7 Ref.http: //www.rockcrawler.com/techreports/glossary/index.asp

Wheel beginning: the sidelong distance between the points where the swivel axis of a steered wheel meets the land and Centre of the Sur footmark is known as the beginning. The axis base on ballss outside it is negative. If it coincides the systems is termed centre point. Figure.8

wheel-offset.jpg

( WHELL OFFSET )

( Figure.8 Ref.http: //www.bargaincarrims.com/wheel-offset.php )

Ackerman consequence: this is the grade by which the inner wheel in a bend is arranged to cover a tighter radius than the outer wheel. Figure.9

arc.jpg

( ACKERMAN EFFECT )

( Figure.8 Ref. hypertext transfer protocol: //www.smithees-racetech.com.au/ackerman.html )

Roll Centres and axial rotation axis: under sidelong cornering forces, the organic structure will turn over on its springs about Centres at both terminals of auto. The line fall ining these Centres is the axial rotation axis and its disposition to the horizontal plane plays an of import portion in the handling features.

Anti-dive and anti-squat: to defy front terminal dip under heavy braking, or rear terminal knee bend under acceleration, suspension pivots are normally angled to supply upward reaction automatically in response to high wheel torsion inputs. Figure.10

anti-squat.gif

( ANTI SQUAT OF REAR SUSPENSION )

( Figure.10 Ref. hypertext transfer protocol: //www.moddedmustangs.com/forums/autocross/184197-torque-arms-amazing.html )

Torque tip: with powerful front thrust autos, there can be an interaction of the thrust system on the suspension geometry which causes way influences on the guidance.

Ct=Cr-Cl=T ( tan I±/2-tan I?/2 )

Roll tip: there are several ways in which the effects of axial rotation can do either forepart or rise up wheel to maneuver the auto somewhat, and this characteristic may be used for all right tuning of a auto ‘s handling. ( Bib.2 page 16 )

Path Width

This is a distance between the forepart and rear wheel centrelines which is illustrated in below Figure. It is really of import for sing resists the turn overing minute due to the inactiveness force at the Centre of gravitation ( CG ) and the sidelong force at the tyres. When planing, path breadth is of import since it is one constituent that affects the sum of sidelong weight transportation. Understanding kinematic analysis of the suspension geometry is important.In instance of choosing the path breadth, the forepart and rear path breadths do non needfully hold to be the same. This design construct is used to increase rear grip during corner issue by cut downing the sum of organic structure axial rotation resisted by the rear tires comparative to the forepart tyres. Based on the corner velocities and horsepower-to-weight ratio of autos, this construct should be considered by the interior decorator. Figure.11

( TRACK WIDTH )

WHEEL BASE

The wheelbase besides needs to be determined. Wheelbase is defined as the distance between the forepart and rear axle centrelines. It besides influences weight transportation, but in the longitudinal way. Except for anti-dive and anti-squat features, the wheelbase relation to the CG location does non hold a big consequence on the kinematics of the suspension system. However, the wheelbase should be determined early in the design procedure since the wheelbase has a big influence on the packaging of constituents. For path breadth and wheelbase get downing points, the interior decorators should research the dimensions of the resistance.

TIRE AND WHEEL

After path breadth and wheelbase considerations have been addressed, the following measure in the design procedure is tire and wheel choice. Since the tyre is of import to the handling of the vehicle, the design squad should thoroughly look into the tyre sizes and compounds available. The tyre size is of import at this phase of the design since the tallness of the tyre must be known before the suspension geometry can be determined. For illustration, the tyre tallness for a given wheel diameter determines how close the lower ball articulation can be to the land if packaged inside the wheel. Tire Size – The interior decorators should be cognizant that the figure of tyre sizes offered for a given wheel diameter is limited. Therefore, sing the importance of the tyre to handling, the tyre choice procedure should be methodical. Since the sum of tyre on the land has a big influence on clasp, it is sometimes desirable to utilize broad tyres for increased grip.

Geometry

The interior decorator can now put some coveted parametric quantities for the suspension system. These normally include camber addition, axial rotation Centre arrangement, and scrub radius. The pick of these parametric quantities should be based on how the vehicle is expected to execute. By visualising the attitude of the auto in a corner, the suspension can be designed to maintain as much tyre on the land as possible. For illustration, the organic structure axial rotation and suspension travel on the skid tablet determines, to a certain extent, how much camber addition is required for optimal cornering. The sum of human body axial rotation can be determined from axial rotation stiffness while the sum of suspension travel is a map of weight transportation and wheel rates. Once a determination has been made about these basic parametric quantities, the suspension must be modelled to obtain the coveted effects. Before the modeling can get down, the ball joint locations, interior control arm pivot points, and path breadth must be known. The easiest manner to pattern the geometry is with a kinematics computing machine plan since the point locations can be easy modified for immediate review of their influence on the geometry. Should a dedicated kinematics computing machine plan non be available, so a CAD plan can be used merely by redrawing the suspension as the points are

Guidance GEOMENTRY

The guidance system transfers the sreering action from the cogwheel box to the maneuvering weaponries of the wheels which provides overall directional control of the vehicle. The maneuvering action is achieved by interlingual rendition of supplanting of the relay linkage in presence of arbitrary suspension gestures. There is obvious potency for maneuvering actions arise from suspension gestures, which are known as maneuvering geomerty mistakes. Figure.12

( STEERING GEOMETRY )

Where

E? is the tantamount tip angle

cubic decimeter is the wheel base

Roentgen is the radius of rotary motion

The tip angle is given by

fingerstall E? = fingerstall E?o + fingerstall E?/2

Radius of rotary motion is given by

BUMP ( ROLL ) STEER

As the suspension moves between bump/rebound, little sum of tip alteration may be introduced due to suspension geometry. When the auto is streed left it is understeered and normally it badly be frightening for normal people when they drive but immature people like top thrust like that.

It is desirable to add an understeer characterstics as follows.

Volt

+ve toe -ve toe

Inside renound outside bump

-ve toe +ve toe

Dotted lines are roll tip exaggerated. The above conventional representation is demoing that under tip charcterstics which are desirable to hold in vehicle. And the suspension curves are as follows.

Steer or Toe – – – – Front

Degrees Rare

0

Bounce 0 Bump

( SUSPENSION CURVE )

VEHICLE HANDLING

There are assorted factors impacting the vehicle handling. The suspension has major effects on cornering this happens due to the assorted maneuvering places like impersonal tip, under tip and over tip. Vehicle handling is used to mention the response of the vehicle to a high velocity cornering or sheering. Apart from that it is besides influenced by weight distribution, suspension, tyres and wheels, unsprung weight etc. The vehicle managing public presentation can be analysed and optimized utilizing Sequential Quadratic scheduling ( SQP ) method and Dynamic Q method.

NEUTRAL STEER

Neutral tip is a constant-radius bend where no alteration in tip angle will be at that place. Physically the impersonal tip instance corresponds to the balance on the vehicle such that the force of the sidelong acceleration at CG causes an indistinguishable addition in slip angle at both forepart and rear suspension.

UNDEER STEER

Under tip on a changeless radius bend, the tip angle will hold to increase with the velocity proportional to the sidelong acceleration. Thus it increases linearly with the sidelong acceleration and with the square of velocity. It is necessary to keep the radius of bend, so that forepart wheel must be steered to great angle. ( Bib.2 )

OVER STEER

Over tip on a changeless bend, the tip angle has to diminish with the addition in velocity. In this instance the sidelong acceleration will increase the faux pas angle on the rear wheel more than the forepart. The rear wheels impetuss more in this instance unless the tip angle is reduced to keep the bend.

VEHICLE DURABILITY TEST

Vehicle lastingness depends on the reinforced quality of the vehicle. The suspension system can act upon the built quality to a certain degree. Most of the lastingness jobs arise due to quivers moving on the vehicle organic structure. If the vehicle has a high public presentation suspension system, the quivers moving on the organic structure reduces and thereby reduces the wear and tear. Lastingness trials are done with and without the system constituents and the trials included destructive trials and other trials. The present twenty-four hours lastingness trials are done on paradigms and the consequences for each trial are used to better the design features. Figure.13

( Vehicle Durability Test Rig )

VIRTUAL TEST RIG

This is a modern physical trial method which provides an optimized path through the design and development procedure. Virtual trial rigs are turn outing land techniques used to obtain load instance information and the use of fatigue analysis method to foretell constituent lives. Though these techniques were developed ab initio for lastingness intent, their benefits are boundless. The practical trial rigs are used practically to play through high frequence informations and to measure noise and drive features.

It besides helps in making vehicle dynamic simulations like maneuvering boot back, as tyre patterning becomes more accurate, managing operation may besides be conducted. Engineers used one of the in house practical lastingness trial rigs in ADAMS/Car to bring forth component burden clip histories and to execute a fatigue life anticipation of the rear lower wishing bone and an tantamount physical lest carried on the hydraulic suspension rig for correlativity intents. This is shown in figure.14

( Multi-Axis Rig Test and Test Suspension )

KINEMATIC AND COMPLIANCE RIG TEST

K and C trial rig machines used to mensurate the quasi-static suspension features which are indispensable to understand the vehicle drive and handling. Kinematics has defined as survey of gesture without mention to the mass and force. Where, Compliance is defection ensuing from the application of force. K & A ; C rig has ability to use the sidelong and longitudinal forces at the tyre contact spot. Suspension parametric quantities such as toe and camber are measured at the wheel hub, while perpendicular, longitudinal and sidelong tyre tonss are measured at the tyre contact spot.

Analysis AND Testing OF SUSPENSION SYSTEM

Ultimately the quality of design will be judged on the public presentation of vehicle, for this an early analysis is required for suspension design as it is indispensable as an single unit. In order to quantify the public presentation of the suspension system a scope of features are identified through simulation of individual suspension system or one-fourth vehicle patterning. There are several types of analysis are used during the design and development of a vehicle. Kinematic, inactive, mobility, axial rotation Centre and dynamic force of analysis are used in simulation of individual suspension system. Computational analysis are used for one-fourth vehicle modeling.The theoretical account geometry has besides been analysed utilizing an tantamount MBS theoretical account in ADAMS package leting a comparing of consequences from theory and MBS and besides supplying readers with an penetration in to the computational procedure involved. ADAMS/car plans provide templets with pre-programmed constellations of suspension system widely used by automotive makers. This package used to analyze the suspension geometry is now good established. The end product from this type of analysis is chiefly geometric and allows consequences such as camber angle or axial rotation centre place to be plotted diagrammatically against perpendicular wheel motion. Figure 15

1.33193! adams.jpg

( ADAMS ANALYSING )

Figure.15 Ref.http: //www.ltu.se/tfm/fpd/research/tools/adams? l=en

Decision

In this instance survey, it will be helpful to understand the Suspension systems and the importance for vehicle kineticss. Here attempted to give a clear position on suspension systems. Concentrated on two major types of suspensions ( Hydraulic and Electro-mag ) .both compared with each other and believes that best suited suspension for a vehicle is electro-magnetic and the design phase itself and helps us to acquire an first-class drive comfort, route control, safety and vehicle lastingness. The design subdivision gives a brief overview of the design and methodological analysis used in these suspensions.Further surveies need to be carried out in this field so that will assist to develop much more efficient suspensions systems in the hereafter.

Mentions:

Web

1. Research on Automotive Suspension Systems for Ride, Handling and Durability

Introduction hypertext transfer protocol: //www.wisegeek.com/what-does-a-cars-suspension-system-do.htm written by R.Kayne

hypertext transfer protocol: //www.articlesbase.com/automotive-articles/the-importance-of-cars-883881.html # ixzz172cN2Xke

2. Image of typical Front wheel suspension system

hypertext transfer protocol: //www.flmidas.com/ss.php

3. Suspension system parts

hypertext transfer protocol: //auto.howstuffworks.com/car-suspension1.htm

hypertext transfer protocol: //www.arab-eng.org/vb/t167797.html

Springs

4. Hydraulic suspension system

hypertext transfer protocol: //www.streetrides.co.uk/tech_advice.php/suspension/hydraulic_suspension

5.http: //www.midas.com/AutoEducation/SteeringSuspensionAlignment/HowitWorks/tabid/99/Default.aspx

6. Vehicle Dynamics – Part 6Vehicle Suspension and Ride, R.G. Longoria, Department of Mechanical Engineering. The University of Texas at Austin.

7. Hydraulic autos in market

hypertext transfer protocol: //www.zercustoms.com/searchcategory.php? c=showcars

Diaries:

1. Journal on “ Introduction to Formula SAEa Suspension and Frame Design ” Edmund F. Gaffney III and Anthony R. Salinas

University of Missouri – Rolla

2. Active Electromagnetic Suspension System for Improved Vehicle Dynamics

Bart L.J. Gysen, Johannes J.H. Paulides, Jeroen L.G. Janssen, and Elena A. Lomonova

Eindhoven University of Technology, The Netherlands.