General Background On Major Problems With Engineering Engineering Essay

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Introduction

1.1 General Background

It is well known that the problem of providing a smoother and softer ride has been a major and complex problem in automotive Engineering (Campbell, C., 1999). Irregularities in the road surface to the passengers were felt with great intensity ever since vehicles went much faster than a horse-drawn vehicle. In addition the invention of the internal combustion engine added some more discomfort in the form of vibration. To minimise the problems the use of independent springing was introduced and this contributed more to the comfort of the ride. Early suspension systems used dependent suspensions which was a solid axle for front and rear wheels. In this type of suspension if one of the wheels happen to hit a bump, this would affect the other wheel. The introduction of Independent suspension meant that each wheel could move up and down without affecting the wheel on the other side of the vehicle. The independent suspension provided a lot of advantages and some of them are listed below:

The use of lower rate springs produces a more comfortable ride.

It has less unsprung weight.

The wider spacing of the springs allows the vehicle to have a much better steering stability.

The engine is lower hence leaving more space in the body.

1.2 Project Definition

The aim of this project is to review three various automotive suspension systems and the use of ADAMS software and control methods to develop and assess the performance of these suspension systems. The three suspensions will include the Macpherson, double wishbone and the leaf spring suspension. To optimise the vehicle performance, this project will also include the changing and manipulation of different parameters of all three of the above named suspension systems

1.3 Research Aims and Objectives

The aim of this project is to review three various automotive suspension systems and the use of ADAMS software and control methods to develop and assess the performance of these suspension systems. The three suspensions will include the Macpherson, double wishbone and the leaf spring suspension system. To optimise the vehicle performance, this project will also include the changing and manipulation of different parameters of all three of the above named suspension systems. Furthermore, in order for the aim of the project to be obtained a few objectives must be met and these include:

To conduct a research on the identification of various suspension design aspects, analysis and control.

Analysis of simple vehicle's bounce, pitch and roll frequencies.

Modelling and analysis of a more realistic quarter suspension model.

Construct and analyse a half vehicle model

Develop a full vehicle simulation model using ADAMS and test various ride characteristics

Carry out sensitivity analysis to optimise vehicle behaviour from various road inputs.

To conclude the findings from the analysis and help provide useful information for further study.

1.4 Project Outline

The outline of the project is as follows:

The first chapter comprises of the introduction, definition, aims, objectives and the project outline.

The second chapter is about the literature review, the background of vehicle suspension, bounce, pitch, roll and the construction of quarter car, half car and full car on ADAMS A-view.

The third chapter deals with the construction of Double Wishbone suspension system using ADAMS CAR.

The fourth chapter deals with the construction of Macpherson suspension system using ADAMS CAR.

The fifth chapter deals with the construction of a leaf spring suspension system using ADAMS/chassis.

In chapter six the results and analysis of the three suspension systems are presented.

Chapter seven is all about the conclusion and the recommendations for further work.

Chapter Two

Literature Review

2.1 Introduction

This chapter comprises of the general suspension literature review to provide a better understanding of the suspension characteristics and the factors affecting its design.

The suspension system consists of the wheel connected to the body through various links; these play an important role as they allow an approximately vertical motion of the wheel relative to the body, hence controlled by the spring and damper.

(Dixon, P.,1996).

2.2 Vehicle Dynamics

This involves the analysis and study of forces and moments and the resulting position, velocity and acceleration of ground vehicles. These forces and moments' definition and causes are:

Vertical Forces: these are normal forces which are transmitted by the suspension and sub frame to the vehicle caused by the road input to the wheels.

Lateral Forces: they are forces acting on the vehicle while cornering.

Tractive Forces: these are forces acting at the tire footprint for the vehicle to maintain the velocity or change velocity.

Rolling Resistant Forces: these are forces that resist rolling of the wheel.

Road Load Forces: the forces at a given velocity that oppose the tractive forces.

Aerodynamic Forces: these are resultant forces exerted on the body.

(Hussain, K., 2010)

2.3 Ride and handling

Ride is the ability of the vehicle to smooth out irregular conditions. The ride comfort id the degree of protection offered to the vehicle occupants from irregular vehicle excitation. Handling is the study of the vehicle motion characteristics, while accelerating, decelerating and cornering (Gillespie, T., 1992). There are three aspects that best describe the vehicle handling and ride characteristics and these are:

Road Isolation: this is the ability of the vehicle to isolate or absorb its excitation due to road shocks.

Road Holding: the vehicle's ability to maintain road surface contact in different directional changes and in straight line motion.

Cornering: vehicle's capability to maintain a certain curved path.

2.5 Common Handling Problems

Under steer: The front wheels tend to crawl slightly or even slip and drift towards the outside of the turn. The driver can compensate by turning a little more tightly, but road-holding is reduced, this causes the vehicle's behavior to be less predictable and the tires are liable to wear more quickly.

Over steer: Is a phenomenon that can happen when the rear wheels do not track behind the front wheels but instead slide out toward the outside of the turn. This occurs to a vehicle while attempting to corner or while is already cornering.

Bump Steer: this is an effect of irregularity of a road surface on the angle or motion of a vehicle. It may be the result of the kinematic motion of the suspension rising or falling, causing toe-in or toe-out at the loaded wheel, hence affecting the vehicle's yaw angle. It may also be caused by defective or worn out suspension components. The bump steer mainly depends on suspension, steering linkage, unsprung weight, angular inertia, differential type, frame rigidity, tires and tire pressures.

Excessive load transfer: when the vehicle is cornering, the outside wheels are more heavily loaded than the inside this is due to the fact that its centre of gravity is above the ground. When the weight transfer equals half the vehicle's loaded weight, it will begin to roll over. (Ellis.,J.,R.,1994)

Body roll : this is when vehicle leans towards the outside of the curve. This affects the driver's control, due to the fact that he has to wait for the vehicle to conclude leaning before he fully judges the effect of his steering change. The body roll also adds to the delay before the vehicle moves in the desired direction

2.6 Suspension Geometry

Camber Angle: It is the lateral inclination of tire in the transverse vertical plane as measured from the ground. It is necessary to have a small amount of negative camber in a suspension for this helps to induce camber thrust. Changes in the camber should be minimized to reduce the loss of camber thrust.

Steering Axis Inclination: this is the lateral inclination of steering axis in the transverse vertical plane as measured from the ground.

Scrub Radius: It is the distance between the treads centre of pressure and the intersection of steering axis with the ground. It also acts as a moment arm which influences a torque about the steering axis during forward motion.

Caster Angle: It is the longitudinal inclination of the steering axis from vertical as measured from the ground. Positive caster induces a self correcting force which provides the straight line stability.

Toe Angle: It is the angle in the plane view which the tire makes with the longitudinal axis. Static toe should be set such that the tires do not become toe out during maximum bump and the roll.

Kingpin Inclination: this is the angle located in front elevation between the steer axis and the vertical axis.

Slip Angle: Slip angle of a tire is the angular deflection between the direction in which the tire is pointing and the direction in which the tire contact patch is travelling. The lateral force developed by the tire is the function of slip angle

2.7 Handling Load Control

The vehicle manoeuvring in the ground plane is shown below:

GRF

Figure 2.1: vehicle manoeuvring in the ground plane

This can be described fully by the pair of differential equations below

()

The equations above are referred to as a two degree-of- freedom (2DOF) model. The formulation sates that the yaw inertia of the vehicle, and that the lateral acceleration is the applied lateral forces divided by the mass of the vehicle. The role of the suspension is to control the vehicle and to transmit the loads (forces necessary to initiate the turn, to constrain the vehicle at the correct sideslip angel) to sprung mass. (Blundell, P., Harty, D., 2004 )

2.8 Transient Handling

In this particular analysis the vehicle handling model has freedom to move over the ground plane while being influenced by the external forces and moments. The model is represented by a single rigid body and also the speed is assumed to be constant. Although it only posses lateral motion and yawing motion it is a very helpful tool in the demonstration of general handling behaviour.

Forces and moments acting on the vehicle

In general these external forces and moments come in two categories namely: the aerodynamic forces of which are impossible to control directly and the tyre forces these are actually under the control of the driver.

a) Aerodynamic forces and moments:

The vehicle is subjected to the drag and lift forces including the pitch moments which arise from the aerodynamic effects caused by the vehicle moving in a straight line in still air.

The vehicle's trim condition is affected when it is subjected to steady side wind while moving in a straight line.

In some cases the vehicle tends to deviate from its course due to the unpredictable forces and moments caused by gusting wind. These disturbances vary in magnitude according to the weather conditions.

b) Tyre forces and moments:

The driver has to have control over the tyre force system to be able control the vehicle motion. the longitudinal forces are for accelerating and braking the vehicle while the lateral forces are responsible for cornering the vehicle and each tyre generates the self-aligning moment.

The Model Assumptions

The vehicle motion idealised using some assumptions in order to get a two degrees of freedom lateral and yaw rate:

The vehicle structure including the suspension is assumed to be rigid.

The road surface is flat.

The input is applied directly to the road wheels.

Aerodynamic forces are neglected

The equation of motion is linear.

Figure 2.1: Vehicle Yaw diagram

2.7 Suspension Types

This project will mainly concentrate on three main types of independent suspension systems, namely the Macpherson strut, the double wishbone and the spring leaf suspension.

2.7.1 Macpherson strut

This type of suspension system uses the axis of telescopic damper as the upper steering pivot. It was named after its designer Earl S. Macpherson and has the most stable body and wheel alignment. In addition it is devised as a more space and structurally-efficient.

2.7.2Double Wishbone Suspension

It is the most common type of independent suspension system and is usually considered to have superior dynamic characteristics, load handling capability and is still found on higher performance vehicles. In this type of suspension you can easily tune the kinematics of the suspension and optimize wheel motion, since it is fairly easy to work out the effect of moving each joint.

2.7.3 Spring leaf Suspension

This consists of a number of leaves clamped together. The leaf provides the location of the axle, and its construction provides the required properties of flexibility and storage of energy (Bastow, D., Howard, G., Whitehead, J., 2004) It has three rods and as a result it also has three degrees of freedom, hence its mechanism is under-constrained. This type of suspension cannot resist torques about the transverse axis for example traction or braking torques, these are reacted by the leaf springs, elastic wind-up of the axle being accepted. This is a suitable suspension for a commercial vehicle due to its ability to minimise the overall loading of joints.

Chapter Three

Mathematical Modelling of Suspension Systems

3.1 Introduction:

This chapter includes the mathematical analysis of a vehicle suspension in terms of its ride analysis. The use of simple vehicle ride models like the quarter car which has two degrees of freedom (2-DOF) can be helpful in the understanding of vehicle vibration and the general concepts of the suspension system. The modelling of a half vehicle with four degrees of freedom (4-DOF) is also analysed to obtain a better understanding of the vehicle pitch and bounce motions. The full vehicle model is then analysed to gather information about the vehicle pitch, bounce and roll

3.2 Quarter Car Model

The vehicle is treated as a body installed on its suspension system that is supported by the tires and axle in this ride dynamics analysis.

The body and suspension constitute the sprung mass.

The tires and axle constitute the unsprung mass

The ride dynamics will mainly focus on the relationship between the body response and the road excitation, and also the relation between the body responses to the vehicle excitation. In other words this is focusing on two major vibration sources which are inputs to the vehicle body and these are uneven road profile, exhaust engine and driveline. The spring supports the sprung mass and the damper dissipates the energy stored in the spring during movement from either compression or expansion. In this model the tyre acts as a secondary spring system acting on both the sprung and unsprung mass of the suspension. This is shown in the Quarter Car Model below:

Figure 3.1: A quarter Car Model

The application of Newton's second law can allow us to obtain the dynamics equations for the above quarter car model. Considering the quarter car model to be two degrees of freedom model with two masses, sprung mass and the unsprung mass

This can also be expressed in the matrix form:

3.3 Half vehicle Model

The half vehicle model in the case consists of four degrees-of-freedom (4DOF). It is also referred to as a bicycle model and its body is assumed to be a rigid bar. The bar has a mass which is half of the total body mass, and a lateral mass of inertia, which is half of the total body mass moment of inertia. In this type of analysis the vehicle includes body pitch, body bounce and independent road excitations as shown in the diagram below:

Figure 3.2: Half Vehicle Model

The equation of motion for the half car bicycle model can be obtained using Newton's equation of motion. By assuming the small pitch angle the equation of motion are as follows:

3.4 Full Vehicle Modelling

The full vehicle model consists of the bounce (), body roll (), body pitch (). In this analysis the vehicle is given the assumption that its body is a rigid slab. This has a total body mass (), also has a longitudinal mass moment of inertia ( and a lateral mass moment (). The model is also assumed to have only body mass moments of inertia; these are shown in the model below:

Figure 3.3:7DoF full Vehicle Model

The equations of motions of the seven degree of freedom model of a full vehicle in figure are given below:

) ( () ( ) = 0

)()

)()

)

)

)

)

Chapter four

Construction of vehicle models on ADAMS

4.1 Introduction

To understand the broad subject of vehicle dynamics, an understanding individual component of vehicle response is necessary. The vehicle dynamics is a very complex subject and a lot of work has been done in this area to help improve vehicle response to various inputs. The simple mass and spring model of a quarter, half, and full vehicle model was created to obtain a general vehicle vibration response. The chapter also compromises of the construction of suspension subsystems on Adams/car for them to be used in the handling and sensitivity Analysis

4.2 Vehicle Specifications from Ford:

This data will be used for ADAMS modelling and simulation, this data was obtained from the ford commercial vehicle specification and technical data:

Dimensions (mm)

 

SWB Low Roof Van

 

Front-Wheel Drive

Overall length (excluding step where fitted)

4863

Overall width (with/without mirrors)

2360/1974

Overall height

1989-2070

Front of vehicle to front wheel centre

933

Wheelbase

2933

Rear of vehicle to rear wheel centre

997

Side door entry width

1030

Rear door entry width

1540

Loadspace between wheel arches

1390

Rear door entry height

1370

Maximum loadspace width

1762

Side load door entry height

1352

Load floor to roof

1430

Maximum loadspace length

2582

Loading height

538-619

Loadspace 

6.55/5.62 (cu.m)

Table 4.1 vehicle dimensions

Weights and loads

 

Driveline

Gross payload (kg)Ø

Gross vehicle mass (kg)

Kerb mass (kg)

Front axle plated mass (kg)

Front axle kerb mass (kg)

Rear axle plated mass (kg)

Rear axle kerb mass (kg)

Axle ratioØØ

Max. GTM (kg) with quoted axle ratio

2.2 Duratorq TDCi Diesel

85 PS/110PS

FWD

1020

2600

1580

1450

985

1475

595

4.23

3500

Table 4.2 vehicle specification

The data in the table below were estimated from looking and various commercial vehicles's technical data:

Description

values

Pitch Inertia

3.45

Roll Inertia

0.45

Front Wheel Mass

45.0kg

Rear Wheel Mass

50.5kg

Front Tyre Stiffness

200

Rear Tyre Stiffness

200

Front suspension stiffness

20

Rear suspension stiffness

26

Front Damping coefficient

1.5

Rear Damping coefficient

1.5

4.3 vehicle technical data

4.3Construction of simple vehicle Models on Adams

The simple spring/mass vehicle were created using Adams/View for the understanding of general vehicle deformation in relation with force, velocity and acceleration.

4.3.1 Quarter car model View

4.4 Simple spring and mass model of a quarter car

4.5 Results of the deformation, velocity and force on the Spring

4.6 transitional results from the body centre of mass on the Y-axis

4.3.2 Half vehicle Model

4.7 Simple spring and mass model of a quarter car

The simulation for this model obtained the same valves as the quarter car model

4.3.3 Full Vehicle Analysis on ADAMS/A view

Full vehicle Model on Adams-View 4.8

The model was created using Adams-View and The vibration analysis of the model was then conducted

4.8 Transitional Displacement and Velocity on the Y-axis of Centre of Mass

The suspension was then analysed looking at the displacement, displacement velocity and the force on the suspension. The results of the analysis were then plotted on the graph below:

4.9 Results of the relation of deformation, velocity and force on the Suspension

4.4Construction of a double wishbone suspension on Adams/car

The main objective of this task is to analyse and modify an assembly of a front double wish bone suspension and a steering subsystem. For this to be obtained I first had to create a double -wishbone suspension and a steering system from the standard Adams/Car templates and subsystems. Intend to understand the suspension's kinematics by performing two type of analysis and these are:-

A baseline parallel wheel travel analysis that moves the assembly vertically through the suspension's rebound-bump travel.

A baseline pull analysis to measure the brake pull at the steering wheel.

Understanding the kinematics of the assembly will help me to decrease the scrub radius, which reduces the pull on the steering wheel. This is obtained by modification of the suspension subsystem's geometry. The reduction of the pull on the steering wheel is then confirmed by analysing the modified assembly again, using the same type of analysis and comparing the new results to the results yielded by the previous analysis.

4.4.1 Creating a Double Wishbone

The suspension was done using the Adams/car templates and then putting my vehicle values. The figure below shows the double wishbone suspension I created:

Figure 4.1: Double Wishbone Suspension system

4.4.2Creating a Suspension Assembly

A steering subsystem was then added to the suspension assembly as shown in the figure below:

Figure 4.2: Double Wishbone Subsystem

4.4.3Defining Vehicle Parameters

For the suspension analysis to be performed first I had to specify several parameters about the vehicle in which I intend to use the suspension and steering subsystems. Since my vehicle is a front wheel drive and its brake ratio will be 64% front hence 36% rear. Listed below are the other vehicle parameters:

Suspension Assembly: my_assembly

Tire Model: user defined

Tire Unloaded Radius:300mm

Tire Stiffness:200N/mm

Wheel Mass:45.0kg

Sprung Mass:2600kg

CG Height:300mm

Wheelbase: 2933mm

Drive Ratio:100 (all the drive force is applied to the front wheel)

Brake Ratio: 64

4.4.4 Performing a Baseline Parallel Wheel Travel Analysis

The parallel wheel travel analysis can be performed now that the vehicle parameters have been identified. The test rig applies force or displacement, or even both, to the assembly during the analysis, as defined in the load case file.

The parallel wheel travel analysis in this case moves the wheel centres from -100mm to +100mm relative to their input position, while holding the steering fixed. During the wheel motion, Adams/car will calculate many suspension characteristics, such as camber and toe angle, wheel rate and even the roll centre height.

When the results are nominated Adams/Car animates the motion of the suspension analysis. The suspension moves from the rebound (down), to bump (up), hence the steering wheel does not rotate.

4.4.5 Plotting the results

Several plots were created from the parallel wheel travel analysis results. I have provided the information Adams/Car needs to create the plots using the configuration file

Figure 4.3: Scrub radius against wheel rate

4.4.6 Performing a Baseline Pull Analysis

This analysis will help me study the steering wheel, I intend to use the results of this analysis as the baseline against which I'll compare the results of another pull analysis that I'll perform after modifying the location of the steering axis. The comparison of these results from the two analyses will help me to determine if the modification is successful.

4.5 Modelling of a Leaf Spring using Adams/chassis

The ride motion manoeuvre is a half-vehicle simulation used for an in phase vertical wheel displacement analysis. The important information gathered from this simulation are: camber, caster, and toe change for insight into the tire wear performance of the vehicle. Another key response is the wheel rate.

Figure 4.4: leaf Spring Suspension Subsystem

4.5.1 Simulation Specifics

When Adams/Chassis is called to build a ride motion simulation, the user must define several variables specific to this type of simulation. In the simulation I have used the Adams/Chassis requested variables with their default values as follows:

Ride motion simulation default

Spindle rise-to-curb

0.0mm

Jounce Travel

20.0mm

Rebound Travel

20.0mm

The above variables, allows Adams/Chassis to build a model that will allow Adams to calculate the toe, caster, and camber for the specified rise-to-curb, jounce, and rebound travel. At time zero the suspension is optionally aligned and will begin at the specified rise-to-curb position. The jounce and rebound travel is measured from design. The figure below shows the leaf spring modeled in Adams/chassis

4.6 Construction of a MacPherson Suspension

The development of a Macpherson suspension system using Adams/car template the hard points for the suspension will be similar to those used in the construction of the double wishbone subsystem.

Figure 4.4: McPherson Suspension Subsystem

Chapter Five

Vehicle Sensitivity Analysis

5.1 Introduction

The main objective of this chapter is to look at different factor that affect the vehicle handling.

5.2 Roll Analysis for a leaf Spring Suspension system

The rear suspension was analysed using the roll simulation parameter on Adams/Chassis

Figure 5.1 Rear Displacement Roll Motion of a Leaf Spring

The graphs below shows the vehicle response obtained during the roll analysis test.

Figure 5.2: Torque and Roll stiffness Against Roll Angel

5.2.1 Roll Analysis for a Double Wishbone Suspension system

Figure 5.3 Front Displacement Roll Motion of a Double Wishbone

Figure 5.4: Torque and Roll stiffness Against Roll Angel

5.3 Double Lane Change

The double lane-change test is designed to stimulate an emergency manoeuvre to determine vehicle handling. The test is important because the more controllable and secure a vehicle is when pushed to its handling limits the better chance the vehicle occupants will avoid an accident. In situations where an obstacle is in the way, due to the compromising nature of the vehicle in general, steering around it can cause the vehicle to go out of control and result in vehicle rollover. Double lane-change for commercial vehicle rollovers are more common than passenger cars because of the higher centre of gravity that makes the commercial vehicle more prone to rollover, especially if swerving abruptly.

The aspect of commercial vehicle safety has most often focused on risk of rollover. The research of National Traffic Safety Administration concluded that the rate of commercial vehicle rollover is two to three times greater than a passenger car.

The sudden cornering forces or double lane-change can cause the vehicle to tip onto two wheels and cause it to rollover.

Figure 5.4: Vehicle During double lane change

Figure 5.5: Results from the Double Lane Change Analysis

Figure 5.6: Roll angle results the Double Lane Change Analysis

5.4 Frequency Response

The frequency response analysis is one of the important aspects in vehicle handling for this contributes to the determination of the centre of gravity height and mass of the vehicle for roll control. The biggest problem in commercial vehicle handling analysis is the variation of the centre of gravity due to the vehicle's loading conditions. The graphs below were obtained from the frequency response analysis of the vehicle with the load included:

Figure 5.7: Frequency Response

./s

Figure 5.8: Frequency Response

Swept Steer

When performing a swept steer analysis, Adams/Chassis applies a steering wheel input to the model and stops when it reaches the specified lateral acceleration.

INITIAL CONDITIONS

Left Front Tire Load = 5102.39 N

Right Front Tire Load = 4928.98 N

Left Rear Tire Load = 4419.96 N

Right Rear Tire Load = 4352.37 N

Front Axle Load = 10031.37 N

Rear Axle Load = 8772.33 N

Total Vehicle Weight = 25480.01 N

Weight Distribution = 53.35 % Front

Initial Vehicle Velocity = 100.00 kph

LINEAR PERFORMANCE GAIN

Under steer Gradient = 3.173 (deg/g)

Slip Angle Under steer Gradient = 0.943 (deg/g)

Roll Gradient = 4.372 (deg/g)

Body-on-Chassis Roll Gradient = 2.548 (deg/g)

Sideslip Gradient = 3.638 (deg/g)

Steering Sensitivity = 1.055 (g/100 deg SWA)

Lateral Load Transfer Dist. = 53.513 (% Front)

Roll Couple Distribution = 1.170

HANDLING VARIABLES

STEER ANGLE

(deg)

Steering wheel torque

(N-mm)

Roll Angle

(deg)

Yaw rate

(deg/sec)

Side slip angle

(deg)

0.10 g =

10.78

3869.20

0.360

2.328

0.266

0.20 g =

20.07

7403.05

0.795

4.503

0.603

0.30 g =

29.63

11039.84

1.232

6.673

0.975

0.40 g =

39.54

14706.81

1.672

8.810

1.413

0.50 g =

50.17

18304.73

2.120

10.960

1.944

0.55 g =

55.80

19805.18

2.345

12.036

2.270

TIRE LOADS

ETS

Under steer

(deg/g)

Left Front

Tire load

(N)

Right front

Tire load

(N)

Left rear

Tire load

(N)

Right rear

Tire load

(N)

0.10 g =

3.088

4588.6

5442.1

3975.7

4797.8

0.20 g =

3.096

4075.6

5948.6

3534.0

5246.3

0.30 g =

3.334

3556.6

6454.9

3095.1

5698.2

0.40 g =

3.541

3028.8

6959.9

2659.9

6155.8

0.50 g =

3.891

2483.5

7471.1

2231.0

6619.2

0.55 g =

4.375

2204.6

7727.2

2017.2

6855.6

Dynamic Constant Radius

In this phenomenon an application of a general approach is done to determine the main parameters (lateral acceleration, roll angle, steering angle) which influence the handling of the vehicle, in function of operational factors of the system. The input data are, on the one hand, the tire and suspension specification, and on the other

Chapter Six

Results and Analysis

6.1 Introduction

This chapter mainly focus on the results obtained from the simulation that were carried out in chapter five .These simulations were carried out in the consideration of a commercial vehicle which consisted of the following:

Double wishbone suspension as the front suspension system.

Leaf spring suspension as the rear suspension system

A load was applied to the vehicle.

6.2 Roll Analysis for a leaf Spring Suspension system

The analysis produced the graph below

Figure 6.1: Torque and Roll stiffness Against Roll Angel

The graph above, show that torque of the suspension gradually increases as the roll angel increase. The roll angle is proportional both left and right of the vehicles axle when the roll stiffness is dramatically changing.

6.2 Double Lane Change

Figure 6.2: Roll angle results the Double Lane Change Analysis

The vehicle has go good a handling in this double lane change but it over steers when turning to the left with the increase in time.

6.3 Dynamic Constant Radius Test

Initial Conditions

Left Front Tire Load = 4996.31 N

Right Front Tire Load = 4804.58 N

Left Rear Tire Load = 5644.20 N

Right Rear Tire Load = 5577.33 N

Front Axle Load = 9800.89 N

Rear Axle Load = 11221.53 N

Total Vehicle Weight = 21022.42 N

Weight Distribution = 46.62 % Front

Initial Vehicle Velocity = 10.00 kph

Initial radius of turn = 3240.78 mm

*** LINEAR PERFORMANCE GAINS ***

Understeer Gradient = 2.277 deg/g

Slip Angle Understeer Gradient = -0.030 deg/g

Roll Gradient = 1.020 deg/g

Body-on-Chassis Roll Gradient = 0.000 deg/g

Sideslip Gradient = 4.595 deg/g

Steering Sensitivity = 2.593 g/100 deg SWA

Lateral Load Transfer Dist. = 74.142 % Front

Roll Couple Distribution = 1.049

Front Cornering Compliance = 0.001 deg/g

Rear Cornering Compliance = 0.000 deg/g

*** UNDERSTEER BUDGET ***

Front Weight and Tires = -8.54 deg/g

Rear Weight and Tires = 15.03 deg/g

Front Roll Steer = 0.04 deg/g

Rear Roll Steer = 0.00 deg/g

Front Suspension Compliance = -29.39 deg/g

Rear Suspension Compliance = 0.00 deg/g

Upstream Steering System = -2.39 deg/g

---------------------------

Front Subtotal = -40.27 deg/g

Rear Subtotal = 15.03 deg/g

Total Understeer = -25.24 deg/g

*** HANDLING VARIABLES ***

Steer Steering Wheel Roll Yaw Side Slip

Angle Torque Angle Rate Angle

(deg) (N-mm) (deg) (deg/sec) (deg)

-----------------------------------------------------------------

0.10 g = 54.29 4207.90 0.424 7.262 0.780

0.20 g = 57.58 7037.73 0.811 9.780 0.408

0.25 g = 0.00 0.00 0.000 0.000 0.000

*** COMPLIANCE AND TRANS LOADS ***

Frt Sideslip Rear Sideslip Frt Load Rear Load

Understeer Angle Angle Trans Trans

(deg/g) (deg) (deg) ( N ) ( N )

------------------------------------------------------------------

0.10 g = 2.379 -0.8 -0.4 1106.0 1020.7

0.20 g = 2.201 -1.3 -0.8 1970.4 1883.3

0.25 g = 0.000 0.0 0.0 0.0 0.0

Frequency Response

Initial conditions

Left Front Tire Load = 5102.39 N

Right Front Tire Load = 4928.98 N

Left Rear Tire Load = 4419.96 N

Right Rear Tire Load = 4352.37 N

Front Axle Load = 10031.37 N

Rear Axle Load = 8772.33 N

Total Vehicle Weight = 18803.70 N

Weight Distribution = 53.35 % Front

Initial Vehicle Velocity = 100.00 kph

Vehicle performance

Maximum Steering Wheel Angle = -0.6306 (deg)

Maximum Lateral Acceleration = -10380.8000 (g)

Lateral Acceleration Parameters

Lateral Acceleration Peak Magnitude = 4.3597 (g/100 deg SWA)

Lateral Acceleration Peak/SS Ratio = 81.8778

Lateral Acceleration SS Magnitude = 0.0532 (g/100 deg SWA)

Lateral Accel. 3 dB Down Frequency = 0.0120 (Hz)

Lateral Accel. 45 Degree Lag Time = 16.3849 (sec)

Roll Parameters

Roll Angle Natural Frequency = 2.7039 (Hz)

Roll Peak Magnitude = 2936598.6340 (deg/g)

Roll Steady State Gain = 23336.9874 (deg/g)

Roll Peak/Steady State Ratio = 125.8345

Yaw Rate to Lateral Acceleration = 7.1543 (sec)

Lead Time at 0.5 Hertz

Yaw Rate Parameters

Yaw Rate Peak Magnitude = 130.4573 (deg/s-100 deg SWA)

Yaw Rate Peak / Steady-State Ratio = 82.2773

Yaw Rate Peak Frequency = 0.0000 (Hz)

Yaw Rate Steady State Magnitude = 1.5856 (deg/s-100 deg SWA)

Yaw Rate 3 dB Down Frequency = 0.0120 (Hz)

Yaw Rate 45 Degree Lag Time = 16.3078 (sec)

Body-On-Chassis Roll Parameters

Chassis Roll Angle Natural Frequency = 2.1057 (Hz)

Chassis Roll Peak Magnitude = 39.6724 (deg/g)

Chassis Roll Steady State Gain = 14.9491 (deg/g)

Chassis Roll Peak/Steady State Ratio = 2.6538

Vehicle Sideslip Parameters

Sideslip Peak Magnitude = 6.4660 (deg/100 deg SWA

Sideslip Peak / Steady-State Ratio = 1.0714

Sideslip Peak Frequency = 1.9958 (Hz)

Sideslip Steady State Magnitude = 6.0349 (deg/100 deg SWA)

Sideslip 3 dB Down Frequency = 0.0000 (Hz)

Sideslip 45 Degree Lag Time = 0.0000 (sec)

Chapter Seven

Summary Conclusion and Recommendation for Further Work

7.1 Summary

The learning and understanding the vehicle ride and handling properties in the literature review helped me to provide the vast information needed in the vehicle handling analysis. The mathematical modelling clearly explained the pitch, bounce and roll on the vehicle , which are a huge contributation to the effect of vehicle handling

7.2 Conclusion

The vehicle analysis was very help full due to the fact that it helped understand the factors that affect commercial vehicle handling properties and this can help in the solving the complex problem in commercial vehicle. The project did look at the theoretical part of the analysis and the went on to the simple vibration of simple spring and mass models. This was the taken further to the realist simulation which were great to use and easy to adjust the vehicle variables hence allowing different types of results to be obtained at the sane time.

7.3 Recommendation For further Work

For the simple vehicle Model include the tyres and construct the suspension in Adams/View to get more understanding of the vehicle pitch, bounce and roll.

The uses of Adams flex to modify the suspension parameters indoor to improve the vehicle handling.

The use of road profiles in Adams truck.

Use of Matlab analysis and comparing then Adams results vehicle's response and comparing.

Construction of three vehicles on Adams with different suspension systems and the analysis the different in handling properties.

References

13th European ADAMS Users' Conference, 1998, 'Identification of Model Parameters with ADAMS/Design of Experiments (DOE) and ADAMS/Optimization',

Paris

Bastow, D., Howard, G., John P, W., 2004, "Car Suspension and Handling", Society of Automotive Engineers, Inc., Warrendale, PA. 4th Ed.

Blundell, M. & Harty, D. 2003, "Multibody systems approach to Vehicle dynamics",

Oxford, Butterworth-Heinemann.

Campbell, C., 1981, "Automobile Suspension", published by Chapman & Hall ltd.

Crouse, W., Anglin, D., 1993, "Automotive Mechanics", New York; London, etc.

McGraw-Hill

European MDI User Conference, 14-15 november 2001, Bertchetsgaden, Germany

ADAMS/Insight Application in Motorsports.

Gillespie, T., 1992, "Fundamentals of Vehicle Dynamics", Society of Automotive Engineers, Warrendale.

Griffin, M.J., 2003, "Handbook of Human Vibration", Academic Press, New York.

Hagiwara, T., Panfilov, S., Takahashi, K., Ulyanov, S., diamante, O., 2003.

"An application of a smart control suspension system for a passenger car based on soft computing", Yamaha Motor Co., Ltd. / Yamaha motor Europe N.V./ STMicroelectronics Srl.

ISO 17387:2008, Intelligent Trabsport Systems - Lane change decision and aid systems (LCDAS) - Performance requirements and test procedures.

International ADAMS User Conference, 2000, " A study of Suspension design Using Optimization technique and DOE" by Keiichi Motoyama, Ph.D and Takashi Yamanaka Mechanical dynamics japan K. K.

ISO 2631-1 (1997). "Mechanical vibration and shock - Evaluation of human exposure to whole-body vibration- part 1: General requirements". Geneva

Matschinsky, W., barker, A., 2000, "Road vehicle Suspension", Professional Engineering Publishing Ltd, London.

Meissonnier, J., Fauroux, J.C., Gogu, G., Montezin, C., 2007, « Geometric identification of a car suspension mechanism based on part displacement analysis », 12th IFToMM World Congress, Besancon (France), June 18-21 2007.

Mittal, D., Gulve, A., Weaver, J., 2006, "Characterization of the Key Vehicle Parameters Affcting Dynamic Rollover Propnsity using ADAMS Simulation and 1/10th Scale Model Testing", SAE Technival Papers: 2006-01-1951.

MSc.software VPD conference, 2006, California.

Orlandea, N., Chace, m., 1978, "Simulation of a Vehicle Suspension with the ADAMS Computer Program", SAE Technical Papers: 770053.

www.auto.howstuffworks.com

www.carbibles.com

www.honda.co.jp

www.redranger.com.au

www.tuev-sued.de

www.wikipedia.org

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