bachelor's thesis - diva portal1025348/fulltext02.pdf · 2016. 10. 4. · bachelor's thesis...

BACHELOR'S THESIS

Investigation of Semi-active SuspensionSystem for the BvS10

Martin Svensson2014

Bachelor of Science in Engineering TechnologyAutomotive Engineering

Luleå University of TechnologyDepartment of Engineering Sciences and Mathematics

Preface

This thesis work was performed at Luleå University of Technologyin collaboration with BAE Systems Hägglunds AB. During the lastsemester of my education to a B.Sc. degree in Automotive Engine-ering, I worked half-time with this thesis. After many late nightsand early mornings since January, it is finally done and presen-table. I want to thank my supervisors, Max Thorén and AndersSandin at BAE Systems for all support during this period. I wantto thank my suporvisor at the university, Magnus Karlberg, for hel-ping me through the process from the beginning to the end. JohanVingbäck at Luleå University of Technology and Robert Bergner atBAE Systems for helping me with the simulations and data analy-sis. I also want to thank the person who gave me a fully equippedworkstation my second week at the office. A special thanks goesto family and friends, who puts up with me even though I am aworkaholic and have strange ideas and goals.

Martin SvenssonSeptember, 2014Luleå, Sweden

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Sammanfattning

BvS10 är en bandvagn som utvecklas och produceras av BAE Syste-ms Hägglunds AB. Under de senaste åren så har uppdateringarnapå vagnen gjort den tyngre, vikten har gått från 10 till 16 ton. Kon-sekvensuppdateringar har då även gjorts på styrdonet, som kopplarde två vagnarna samman. Styrdonet består av fyra cylindrar och enrotationsled. Dessa gör att bandvagnen kan svänga, använda aktivtilt och tillåta stora vinkelskillnader mellan fram- och bakvagnen,vilket bidrar till framkomligheten hos produkten.

Sedan semi-aktiv dämpning sattes in i BAE Systems andra pro-dukt, stridsvagn CV90, så har intresset för att montera ett liknan-de system på BvS10 ökat. Syftet med arbetet är att analysera omen uppdimensionering av tilt cylindrarna är fördelaktigt för semi-aktivt styrning. Dessutom undersöks om en föreslagen hydraulventilfrån Öhlins Racing AB är lämplig att styra det semi-aktiva syste-met och var den kan placeras.

Analyser visar att ett större spann av dämpkraft vore fördelaktigtför BvS10. Det gör att en storleksökning av tilt cylindrarna är nöd-vändig, för att klara av krafterna från de tyngre vagnarna och ökalivslängden. Analyserad data och simuleringar visar att den före-slagna ventilen klarar både tryck och flöden som uppstår i systemet.Trycket ligger visserligen utanför det optimala området ventilen ar-betar i, men om det fortfarande uppfyller kravspecifikationen måsteundersökas vidare. Ventilen bör placeras i ventilblocket monterat påstyrdonet för bästa åtkomlighet och funktion.

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Abstract

The BvS10 is an armoured all-terrain vehicle produced and de-veloped by BAE Systems Hägglunds AB. During the last years,development of the product made it heavier increasing the weightfrom 10 to 16 tonnes. The steering device, coupling the two bod-ies together, have been updated to withstand the weight increase.The steering device consists of four hydraulic cylinders and a ro-tational joint. These can turn and tilt the vehicle and allows forlarge differences between the angle of the front and rear bodies,thus increasing the accessibility of the vehicle.

A semi-active suspension system was installed in BAE Systemsother product the CV90, a combat vehicle. Since then, installing asimilar system on the BvS10 has been in the interest of the com-pany. The aim of the project is to analyse if an increase in sizeof the tilt cylinders would benefit a semi-active control of the flowto and from the cylinders. A proposed solenoid valve from ÖhlinsRacing AB will also be investigated, whether it suits to control thesystem and where is should be placed.

Analysis show that a larger span of damping force would advanta-geous for the BvS10, therefore increasing the size of the tilt cylin-ders is necessary to withstand the forces and increase the life-span.The analysed data and simulations show that the proposed solenoidvalve is capable to handle both the flows and the pressure of thehydraulic system. However, the pressure is outside of the valve’soptimal performance range, which is why the valve has to be testedin the environment to ensure it passes the requirement specifica-tion. The solenoid valve should be placed in the valve block on thesteering device, providing the best accessibility and function.

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Contents

List of Abbreviations vii

List of Symbols vii

1 Introduction 11.1 Background . . . . . . . . . . . . . . . . . . . . . . 1

2 Theory 42.1 Comfort and Handling . . . . . . . . . . . . . . . . 42.2 Hydraulic Systems . . . . . . . . . . . . . . . . . . . 7

3 Method 103.1 Data Acquisition and Analysis . . . . . . . . . . . . 113.2 Tools for Data Analysis . . . . . . . . . . . . . . . . 12

4 The System 134.1 Concept Generation . . . . . . . . . . . . . . . . . . 154.2 Simulations and Data Acquiring . . . . . . . . . . . 16

5 Results 205.1 The Tilt Cylinders . . . . . . . . . . . . . . . . . . . 205.2 The Hydraulic Valves . . . . . . . . . . . . . . . . . 225.3 Installation . . . . . . . . . . . . . . . . . . . . . . . 235.4 Requirement Specification . . . . . . . . . . . . . . . 26

6 Discussion 28

7 Conclusion and Recommendations 30

Bibliography 31

List of Figures 35

I Tilt Cylinders

II Requirement Specification and Evaluation Matrix

IIISimulink Model

IV Solenoid Valve CES8700

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List of Abbreviations

ECTS European Credit Transfer System

DTL Dynamic Tyre Load

CAD Computer-Aided Design

APG Aberdeen Proving Ground

SAE Society of Automotive Engineers

RMS Root-Mean-Square

List of Symbols

x0 Initial displacement [m]

xt Displacement at time t [m]

ẋ0 The initial velocity [m/s]

ẋt The velocity at time t [m/s]

Kt The spring stiffness at time t [N/m]

Ct The damping coefficient at time t [Ns/m]

F Force [Nm]

P Pressure [Pa]

A Area [m2]

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Chapter 1

IntroductionThe introduction covers the background, the aim of the project,questions of importance, delimitations and disposition.

1.1 Background

The product development described in this thesis regard the BvS10from BAE Systems Hägglunds in Sweden. BAE Systems is oneof the biggest groups in defence, aerospace and security and hasits headquarters in the United Kingdom. BAE Systems Hägglundsis one of many subsidaries around the world, employing in total88,200 persons (BAE Systems, 2014). BAE Systems Hägglunds arecurrently producing two vehicles, the CV90 and the BvS10. TheCV90 is a combat vehicle and the BvS10 is an armoured all terrainvehicle, seen in Figure 1.1.

Figure 1.1: The armoured all terrain vehicle, BvS10

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The BvS10 uses tracks with propulsion on both bodies and thereforeall four tracks. The two bodies are connected with a steering device,Figure 1.2, which is bolted into the bodies.

Figure 1.2: The BvS10 with the steering device

The steering device is built to let the bodies move in four degrees offreedom relative to each other. The current setup uses two hydrauliccylinders for steering and two for the active tilt. This thesis adressthe tilt cylinders and their damping ability.

Today the two hydraulic tilt cylinders remain the same as when thevehicle first was designed for a total vehicle weight of 10 tonnes.However, the vehicles produced today weighs around 16 tonnes,which is a 60% increase. Driving on the road the vehicle can startto bump, causing discomfort for the passengers. It also happensthat the pistons of the tilt cylinders hits the end stops, causingfurther discomfort but also increased wear. This is mainly due tothe increase in mass, without increasing the damping in the vehicle.

BAE Systems Hägglunds has also recently introduced semi-activesuspension to the CV90, with satisfying results. Therefore, a semi-active suspension system are to be developed also for the BvS10.Due to the increased weight more damping effect is needed betweenthe bodies.

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The aim for this thesis is divided into three steps. The first part isrelated to the damping of the tilt cylinders and whether an increasein diameter would be beneficial for the system. The second partis to verify that suggested hydraulic valves from Öhlins works withthe system without breaking or damaging the system. The thirdpart is to evaluate the different possible placements of the valves.A requirement specification for the system will also be developedand used for further development.

To fulfill the aim of this thesis, the following questions will be eval-uated:

• Can the existing hydraulic tilt cylinders be redesigned to pro-vide more damping?

• Does the suggested hydraulic valves from Öhlins Racing ABwork with the system?

• Where can the valves be installed?

The limitations in the project lies in time and product limitations.The time available is 15 ECTS-credits, which is 400 hours of work.Due to the time frame, initial simulations and values of the vehiclewill be provided by BAE Systems Hägglunds.

The design space of the vehicle is fixed and consists of the spacebetween the two bodies (Figure 1.2). Minimal changes are prefer-able, as well as low weight and cost. Therefore, a solution that ismountable on already manufactured vehicles would be valuable tothe company.

To support the result from the simulations performed at BAE Sys-tems, fluid mechanic simulations had to be made. Due to the timeconstraint the simulations were made simple, using standard blocksin Simulink. An assumption was made that the default values, forReynolds critical number and geometrical factor among others, aregood enough to evaluate the different concepts.

The report will first go through theory and methodology introduc-ing relevant knowledge and describing the work process. Then therewill be a description of the system before presenting the results anddiscussing the validity. In the end there will be a conclusion of thework and a recommendation for the company.

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Chapter 2

TheoryIn this chapter relevant theory in vehicle dynamics and hydraulicsare described. Standard SAE vehicle dynamics coordinate systemare used through out the report (Figure 2.1).

Figure 2.1: SAE coordinate system

2.1 Comfort and Handling

Comfort is a complex term that can be difficult to measure. Thereare many definitions of comfort, but since comfort is decided by theexposed it is a subjective matter as described by Faris, BenLahcene,and Hasbullah (2012). However, there are research indicating thatsome behaviour of a vehicle are more discomforting than others.Starting from the definition of comfort used by Rajamani (2006),the vertical acceleration is the main reason for discomfort. Whenlooking at a wide range of researchers this is the case, although allaccelerations, jerk and vibration. Depending on direction, magni-

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tude and duration the acceleration and jerk are more or less dis-comforting. When it comes to vibrations it is depending on thefrequency, type of vibration and the duration.

Quanan and Huiyi (2004) have performed a thorough study onjerk. They write in their paper that jerk can be classified into twogroups, transient and durative jerk, referring to the physiologicalexperience. Jerk is the derivative of acceleration, the rate of changeof acceleration. Jerk can be experienced as a jolt or a sudden shock,where large and frequent exposure to jerk is uncomfortable andsometimes unhealthy for drivers and passengers.

However, it is important to take the whole system into considerationwhen applying any changes. Chen et al. (2011) showed the followingresults:

• Though soft seat can make ride comfort better, it does notimprove ride of sprung mass (i.e. the comfort of people’s feet).

• It should be mentioned especially that the rubber componentsas an important isolation element, plays a very importantrole in ride comfort. The possible reason is that the elasticcharacteristics of rubber components change whole suspen-sion stiffness.

This shows that ride comfort of the sprung mass is very important,since comfort cannot come from a soft seat alone. When designingthe suspension system, the awareness of that the spring stiffness isnot isolated only to the spring, is a tool to reach the target stiffness.This could also mean that the suspension system can be tuned bychanging the rubber components.

All vehicles need to have at least an essential level of handling tobe drivable. Either the car has to be manoeuvrable to be safe orso that it can go fast on a track, either way it has to have goodhandling and therefore traction.

Els et al. (2007) claims that when designing a vehicle suspensionsystem it is well-known that spring and damper characteristics re-quired for good handling on a vehicle are not the same as thoserequired for good ride comfort. The case studies that they per-form indicates that suitable spring and damper characteristics for

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handling and ride comfort are different. Handling requires a stiffspring and high damping mode while a soft spring and low dampingmode are required for ride comfort. The soft suspension systems,which generally provide a very good ride comfort at the expenseof handling, is the opposite problems of a typical sports car. In asports car the handling is often excellent, but the ride comfort canbe harsh.

The definition of handling used by Els et al. (2007), defined byHarty (2005), that says:

"Handling is the percentage of the available friction or the max-imum achievable lateral acceleration utilised by the vehicle-drivercombination."

Using this definition and a experiment by Uys, Els, and Thores-son (2006) where three vehicles were test driven by four drivers ontwo handling test tracks, the definition can be measured. The testresults strongly suggested that roll angle was a suitable metric tomeasure handling.

Yin et al. (2012) says that a soft suspension is desirable for ridecomfort and road-friendliness. However, this would deteriorate thehandling performance, directional stability and increase the suspen-sion design space. On the other hand, a relatively stiff suspension ispreferred for good handling performance and drive stability, whilethe ride comfort is penalised. Light damping is helpful for ride com-fort, but adequate damping is necessary to suppress the resonancevibration and provide better roll and directional stability, brakingperformance, suspension travel and road-friendliness as stated byAhmadian and C.A. (2000) and Cao (2008).

This is shown by Els et al. (2007) as in their result on a armouredvehicle indicate a damper force ratio between 0.2 and 0.5 and anatural frequency in the region of 0.6 Hz gives good ride comfort.For stability and handling the natural frequency should be around2 Hz and the damping force ratio a factor two of the baseline value.

Gonzalez Prada et al. (2011) states that semi-active and activesuspension systems offer a better trade-off between ride comfortand vehicle handling as they dynamically modify the damping ratio.However, this benefit is obtained at the expense of cost, complexity

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and for active suspension, power consumption. they evaluate theirtheoretic model with the following parameters:

• Vertical displacement of the sprung mass (heave). Used toevaluate the achieved body control.

• Vertical acceleration of the sprung mass (heave acceleration).Used as a measure of comfort and vibration levels.

• The DTL (dynamic tyre load) which is expressed by equation2.1, and is used as a measure of road holding levels and there-fore representative of the handling and traction performanceof the vehicle.

DTL = (x0 − xt)Kt + (ẋ0 − ẋt)Ct (2.1)

The roll angle is a good measure of the handling of a vehicle. Alower ride height results in reduced body roll and gives lower centreof gravity (Giliomee and Els, 1998). From the conclusion of theirwork on semi-active hydro-pneumatic springs in a armoured fightingvehicle, they say that the non-linear spring characteristics are veryuseful. Used in the right way it will eliminate the necessity for abump-stop when the spring setting is hard.

2.2 Hydraulic Systems

Hydraulic systems are widely used in different applications, mostlyheavy machinery. In terms of suspension, hydraulic dampers arevery common on vehicles and in vehicle systems. One reason is thatcompared to air suspension systems, the hydraulic fluid is far lesscompressible, about 3000 times at 7 bar pressure (Ingvast, 1990).The hydraulic damper is therefore very precise and useful for ac-tive and semi-active systems. A hydraulic system usually works athigh pressures, which for the BvS10 is 250 bar of working pressure.However, the amount of air in the hydraulic fluid has to be kepta minimum to make sure the system is as stiff as possible. If thefluid contains about 10% of air at atmosphere pressure leads to thefluid containing four times as high energy, than oil free from air.

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In the hydraulic system the hoses provide about ten times as highsuspension as the fluid itself. (Ingvast, 1990)

The force produced by a hydraulic system can be written as Equa-tion 2.2. (Hunt and Vaughan, 1996).

F = P × A (2.2)

A hydraulic cylinder is a linear actuator in a hydraulic system.There are different types of cylinders, for example single-acting,double-acting single ended and double-acting double-ended. TheBvS10 uses double-acting single ended cylinders, which has a pistonrod in one end and have a fluid port on each side of the piston, seeFigure 2.2.

Figure 2.2: A double-acting single ended hydraulic cylinder

Cushioning is necessary in hydraulic cylinders where speeds over0.1 m/s is common or where there are huge masses attached tothe cylinder. The cushions, also called bump stop, are designedto increase the pressure inside the cylinder as it is close to an end-point. This will reduce the speed and force on impact, and thereforeprolong the duration of the cylinder (Hunt and Vaughan, 1996)

To control the hydraulic system a valve can be used. A control valvecan either control the direction of the fluid, the pressure or the flow

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rate. There are a variety of different valves in these categories,where current driven solenoid operated valves are most common.Solenoid valves uses magnetic force to move the armature of thevalve and select different flow paths, which can limit the flow orpressure. (Doddannavar, Barnard, and Machay, 2005)

As mentioned the fluids compressibility depends on the amount ofair in the fluid. For dynamic purposes the bulk modulus, which isthe inverse of fluid compressibility and measured as the change inpressure to create a specific change in volume. A high bulk modulusrender the fluid almost incompressible, while a low will cause thefluid to act more as a spring. (Van de Ven, 2013)

Systems can either be passive, semi-active or active. A passive sys-tem has no control system and always has the same performance.A typical example is a common spring-damper system in the sus-pension of a car. Some cars have a semi-active suspension system,which means that there is a way to change the characteristics ofthe suspension system without additional forces. An active systemcan for example change the ride height of a vehicle with pneumaticsuspension depending on the load in the vehicle, thus adding energyto the system.

This technology in the size comparable to the actuators of theBvS10 is often used in skyscrapers to dampen the movement of thebuilding. These systems moves a huge mass to counter the windsaffecting the top of the skyscraper, and are active or semi-active(Chung-Huan et al., 2010).

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Chapter 3

MethodThis project follows the product development theory presented byUlrich and Eppinger (2003) shown in Figure 3.1.

MissionStatement

DevelopmentPlanIdentify

CustomerNeeds

EstablishTarget

Specifications

GenerateProduct

Concepts

SelectProduct

Concept(s)

TestProduct

Concept(s)

SetFinal

Specifications

Benchmark Competitive Products

Bulid and Test Models and Prototypes

Figure 3.1: The product development process by Ulrich and Ep-pinger (2003)

The first step in this process regards identification of the customerneeds, and translation of these to a requirement specification. Therequirement specification are evaluated and edited together withthe customers, in order to increase their satisfaction with the solu-tion. When the target specification is set, it is time to work withconcepts. In this specific thesis the concepts generated are relatedto the placement of the hydraulic valves. The next step is to testthe different placements of the hydraulic valves and evaluate thedifference. Last step is to revise the requirement specification tosee if any changes has to be made.

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3.1 Data Acquisition and Analysis

The bulk of data was collected from reports, target specificationsand descriptions of the vehicle and its’ parts from the company’sdatabase. Those were used to gather knowledge of the structure ofthe vehicle and the systems and components relevant to this thesis.Further data was gathered through unstructured interviews withemployees who works or worked with the BvS10 (Osvalder, Rose,and Karlsson, 2008). The interviews were used to get a set of differ-ent pictures of the problems associated with the tilt cylinders. Oneinterview was performed within the area of simulations, solid me-chanics, hydraulics, testing and project supervision. During the in-terview the employees explained the problems encountered and thework they had done during development of the vehicle. Comparingthe interviews to the reports of breakdown of the tilt cylinders anddocuments on the database, it was to construct the requirementspecification and the generation of concepts for the valve place-ment. As a method an interview is preferable if subjective anddetailed information is wanted. The interviewer has to take in toconsideration that the interviewee might be nervous, insecure dur-ing interviews or stressed from the time consumed from his or herswork (Osvalder, Rose, and Karlsson, 2008). For this thesis inter-views was useful as complement to the reports from the database,since not all problems and observations are to be found in any re-port.

During the time an other thesis work was performed on simulationof the BvS10 and the damping of the tilt cylinders (Vestman, 2014).From these simulations the results were imported for evaluationfrom the hydraulic perspective. The results and its’ validity and re-liability from the simulations were discussed with an employee whoperformed earlier simulations on the BvS10 and the thesis workerwho performed the simulations. The steady-state was compared toother simulations and found to have an offset. Therefore the resultsin this thesis will use the steady-state of the CAD model and theassumed steady-state from earlier simulations.

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3.2 Tools for Data Analysis

The softwares used was Catia V5 and Siemens NX, Simulink andMATLAB. Catia V5, which is the standard CAD-programme atBAE Systems, was mainly used to view, evaluate and export modelsfor Siemens NX. The models were imported into Siemens NX, werethe geometrical relationships were analysed. All data from the sim-ulations in ADAMS (Vestman, 2014) were processed in MATLABfor analysis and visualisation. During the simulations the volumeof the cylinders, maximum flow of hydraulic fluid and maximumvelocities and forces were monitored for comparison. Calculationsand cross-referencing drag and push forces were also performed andcompared to the data sheets, as a validation of the model and simu-lations. A model of the hydraulic system connected to the cylinderswas created in Simulink using standard blocks and variables for thedifferent components.

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Chapter 4

The SystemThe steering device of the BvS10 is the connection between thetwo bodies. It is designed to allow for movements of rotational de-grees of freedom between them, which makes the bodies somewhatindependent. The device consists of four hydraulic cylinders, forsteering and tilt, and a rotation connection. The steering device isfixed to the rear waggon with the connectors shown to the right inFigure 4.1, and can be disconnected from the front waggon. Thisis needed for transporting the vehicle with helicopters, where theweight of the whole vehicle is too heavy.

Figure 4.1: The steering device with all fittings

The movement of the steering device is showed in Figure 4.2. Thetranslations of the tilt cylinders are represented by straight greenarrows, while the rotation it yields are showed by the correspondingrotating arrows in green. When steering the vehicle the steeringcylinders, red straight arrows, cause a rotation around the centre ofthe steering device (red rotating arrow). The blue rotational arrowshows the roll angle between the two bodies. Those movements

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represent four degrees of freedom and allows for accessibility inrough terrain.

(a) Side view

(b) Top view

Figure 4.2: Showing translations and rotations of the steering de-vice

The scope of the work is associated with the tilt cylinders andhydraulic system connected to them. The cylinders have the di-mension specified in Table 4.1, and are used in most calculations.

Table 4.1: Dimensions of the tilt cylinders

Position Piston Diameter Stroke Rod DiameterFront Cylinder 80 mm 250 mm 32 mmRear Cylinder 80 mm 210 mm 32 mm

From the data sheet of the cylinders, Appendix I, all relevant pa-rameters are given. Previous work at BAE Systems have investi-

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gated and proposed a larger cylinder of 100 mm piston diameterfor the tilt cylinders. This would increase the possible forces thecylinders can produce and are therefore investigated in this thesis.

4.1 Concept Generation

The different concepts originates with the placement of the vari-able valves, used for controlling the damping of the tilt cylinders.Three different possibilities have been identified and will be evalu-ated based on the requirement specification (Appendix II).

Figure 4.3 shows different concepts, as to where it is possible tofit the semi-active valve. The first position is directly attached tothe cylinders, which the green rings shows. The second positionis in the valve block of the steering device (blue ring) and thirdpossibility is in the valve block in the front waggon (red ring).

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(a) Side view

(b) Top view

Figure 4.3: Showing different positions where the semi-active valvecould be placed

However, there is a possibility that the valves can be mounted tocontrol the flow to either one side of the cylinders or to both sides.Since the movement of the piston is controlled by the flow to andfrom the two chambers, controlling the flow to one side might beenough. Therefore, it has to be tested if one or both flows to eachcylinder needs variable valves, along with the three different posi-tions of the valves.

4.2 Simulations and Data Acquiring

This work is based on analysis of acquired data and simulations ofthe system using Simulink. The data was provided by BAE Sys-

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tems from simulations of the vehicle in ADAMS (Vestman, 2014).The data originated from simulations on APG and RMS tracks,see Figure 4.4, which cause different types of movement of the ve-hicle. The RMS track exposes the vehicle for vertical accelerations,and the root-mean-square value of vertical acceleration is used forevaluating ride comfort.

(a) The RMS-track used in ADAMS simulations

(b) The RMS-track used in ADAMS simulations

Figure 4.4: Tracks used for simulations

The RMS track exposes both sides for the same terrain, but vary inthe forward direction causing the bodies to pitch. The APG trackhave both aligned and unaligned obstacles of two different heights,which subjects the vehicle to pitch and roll motions. Obstacle Ahas a height of 100 mm and obstacle B of 150 mm. The data sentfrom these tests were time, displacements, velocities and forces ofboth tilt cylinders during all runs. Both tracks were tested multipletimes with varying velocity from 20 km/h to 60 km/h.

The analysis performed was an evaluation of the volume of the

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cylinders and the flow the movement caused. Looking at the volumeinside the cylinders were made to see whether the piston wouldhit bottom and to get an understanding of the movement of thecylinders. Large movements under a short duration would providelarge flows within the hydraulic system, while small movementswould do the opposite. Analysing the maximum flow from and tothe cylinders, assuming the fluid to be incompressible, were usedto evaluate the variable valves. If the fluid were incompressiblethe change in volume would equal the change in fluid within thecylinder. In reality there is always some compressibility, causingsome of the fluid to compress, thus a smaller volume will leave thecylinder. Due to the low movements of the cylinder and thereforesmall flows, a simulation model of the hydraulic system had to bemodelled.

The model created in Simulink consists of standard blocks fromSimscape and Simhydraulics. It is a simplified model of the hy-draulic system of the BvS10, with a front and a rear system (Ap-pendix III). Building the system as the original is complex, andthe simulations was needed to evaluate the concepts. Therefore, asimplified simulation had to be used.

Figure 4.5: Displacement of the rear cylinder

The model is based on the hydraulic system and one of the tilt

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cylinders, making it somewhat realistic. One problem with a simu-lation model like this one is that it has no masses or inertia, whichresults in a net force pushing the rod to the end position. This isdue to the area differences on the piston side and rod side of thecylinder. Having a bias force to balance the difference created an-other problem, that the flow resistance on both sides are not equal.Therefore, the displacement of the cylinder will have a slope shownin Figure 4.5. However, as long as the cylinder do not reach any ofthe end positions, there will be no effect on the flow to and fromthe cylinder ports. This is also the reason for using an ideal forcesource, to compensate for the difference.

In the simulation setup, seen in Appendix III, the flows are mea-sured on the piston side of the rear cylinder. There are two flowmeters, one is placed in the coupling of the front waggon and theother one in the valve block at the steering device. Positive flowis toward the cylinder from the front waggon. The oil used in thesimulations is a standard fluid, Oil SAE-50, which have similarproperties as the oil used in the BvS10.

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Chapter 5

ResultsThe results are covered in the different sub-chapters, which eachgives the results of a corresponding question of importance.

5.1 The Tilt Cylinders

The simulations performed in the parallel thesis work at BAE Sys-tems Hägglunds, (Vestman, 2014), shows that it would be an im-provement to be able to vary the damping of the tilt cylinders.During the simulations the highest damping force was set to 200kN, which is close to the designed breaking point. The breakingpoint of the attachments are designed to break at 224 kN. Increas-ing the size of the tilt cylinders would make them withstand greaterforces and increase the life-span, thus creating a more potent sys-tem. As investigated earlier by BAE Systems it would be possibleto increase the diameter of the cylinders, from 80 mm inner di-ameter to 100 mm. This would increase the maximum drag andpush force of the cylinder, at the maximum internal pressure of 250bar, to a maximum of approximately 196 kN or push force and 176kN of drag force (equation 2.2). This would allow the vehicle tohave a stronger active tilt of the vehicle, which is strong enough asit is today. However, used in an advance control system it couldminimise the wear of the steering device by active avoiding the endpoints. Though this would result in an active suspension system,not a semi-active as investigated here.

The forces can spike during driving and cause the cylinder attach-ment to break, since the pressure within the cylinders can go ashigh as 400 bar momentarily. With the increased size, the cylin-ders would hold for spikes when compressed. Exposed to a pull the

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designed breaking point in the attachment will break. As seen inthe requirement specification, the vehicle has to be drivable evenif the tilt cylinders break. If the cylinders are to be larger, cal-culations are necessary in order to make sure that the designedbreaking point will be the only thing to break. That will result ina controlled break of the attachment of the rear cylinder, withoutdamaging the steering device.

(a) Current damping (b) Highest damping

Figure 5.1: Front Cylinder volume change during RMS-track

Figure 5.1 shows the change in volumes in the front cylinder duringa simulation on a RMS-track in 20 km/h with the damping oftoday and with the highest damping possible with cylinders of 100mm diameter. Volume A is the piston volume and volume B is therod volume of the specified cylinder. The orange lines representthe minimum and maximum total volume of the cylinder, volumeA and volume B. The black line show the current volume in thecylinder, therefore showing the movement of the piston. If theblack line touches any of the orange lines, the piston has reachedan end point. Therefore, pitch of the vehicle can be interpretedas a change in volume of the tilt cylinders. It is seen in Figure5.1 that the higher damping reduces the change in volume, thusthe pitch movement. For a incompressible system the change involume shows the movement of the cylinders, as for a system withhigh amount of air it will show the compression and some flow ofthe fluid.

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Using the same analysis for the rear cylinder on a APG-track in 60km/h, and the result will be as shown in Figure 5.2

(a) Current damping (b) Highest damping

Figure 5.2: Rear Cylinder volume change during APG-track

5.2 The Hydraulic Valves

The hydraulic valves from Öhlins are the CES8700 hydraulic valve,specifications can be found in the data sheet (Appendix IV). Witha pressure of 14-16 bar the valve can handle flows up to 100 l/min.The maximum operational pressure for optimum performance is 200bar, which is less than the 250 bar of pressure used in the hydraulicsystem of the BvS10. However, the valve will operate up to 400 bar,but the behaviour has to be investigated. Two valves could be usedin series to reduce the pressure over them, either two of the proposedsolenoid valves or use an other restrictor. As for the flow the valveswill operate up to 100 l/min, which is within the simulations inSimulink shows. The maximum flow when subjected to a sinusforce of 10 kN is around 10 l/min. The original simulations showsthat the flow reaches peaks of about 60 l/min, assuming the fluidas incompressible. This is within the products specifications andthe hydraulic valve will be sufficient for the system.

22

5.3 Installation

Using the simulation in Simulink three different positions of thehydraulic valve was compared. The first position is connected di-rectly to the cylinder, the second is built-in the valve block of thesteering device and the third is connected in the rear of the frontwaggon. A sine force with an amplitude of 10 kN was used forthese simulations shown in Figure 5.3.

23

(a) Measured flow in the valve block of the steering device

(b) Measured flow in the valve block of the front waggon

Figure 5.3: Flow measured with different positions of the valve

This shows the flows measured at two positions, the valve block inthe steering device and in the front waggon. The positions of thevalve, as explained earlier, are plotted against each other, followingthe same pattern. The valve used for the simulation is a fixed orificeof 0.8 mm in diameter, smaller than the 1.7 mm in diameter orificein the valve block of the steering device. To show a difference inthe placements of the variable valve, the fixed orifice acting as the

24

solenoid in a specific setting, is chosen with a diameter smaller thanthe 1.7 mm orifice.

(a) 50 Hz sine

(b) 100 Hz sine

Figure 5.4: Rear Cylinder during sine input

The differences between the earlier mentioned measuring points,the valve in the steering device and the valve in the front waggon,can be seen in Figure 5.4. There will a phase shift at higher frequen-cies, which is expected of a spring-damper system. These figures

25

show a sine of 50 and 100 Hz using no solenoid valve. However,no difference in flow was found between using a solenoid on oneside of the cylinder or on both sides. The only difference foundin the model was that the slope of the displacement was smaller.Therefore, placing one valve on the piston side of the cylinder isdesirable, due to the larger volume.

5.4 Requirement Specification

Together with BAE System the requirement specification was formed,see Appendix II. Based on interviews with employees the customerneeds was analysed and then put together to measurable goals. Therequirement specification will be used as a evaluation matrix andcan later be used for further development of the system.

ImportanceConcept 1Concept 2Concept 3

5 - - -

5 25 25 25

5 25 25 25

5 25 25 25

5 25 25 25

5 25 25 25

5 25 25 25

5 25 25 25

5 25 25 25

5 25 25 25

Total 225 225 225

ImportanceConcept 1Concept 2Concept 3

5 25 25 25

3 15 15 15

4 12 12 12

2 2 10 6

2 2 10 6

5 0 25 25

3 - - -

2 10 10 10

4 - - -

2 - - -

5 25 25 25

3 - - -

Total 91 132 124

Good to have

Need to have

Minimises the acceleration and jerk at the drivers' seat.

Allows tilting the vehicle.

Preserves the steering characteristics of the vehicle.

Allows rotation between the two bodies.

Fits in the existing space between the bodies.

Is resistant to temperatures.

Is ready for semi-active control.

Is tightly sealed, preventing oil leakage.

Makes sure the vehicle is drivable even if the tilting cylinders are broken.

Has a controlled braking point in the rear tilt cylinder.

Reduces the forces in the steering device and the hull attachments.

Has low weight.

Will easily decouple the bodies.

Is cheap.

Can be easily accessed for maintenance in the field.

Allows easy replacement of worn parts.

Is mountable on already produced vehicles.

Reduces wear in the components between the bodies.

Can be maintained with readily availiable tools.

Has high robustness.

Increases mobility.

Has the ability to respond quickly to the semi-active system.

Figure 5.5: Evaluation Matrix

26

Based on the requirement specification, the evaluation matrix inFigure 5.5 was made. Since there is no data showing if this min-imises the acceleration and jerk in the need to have section, no of theconcepts have received a score. All concepts have the same resulton the other needs, which is why they have the same score in theneed to have section. In the good to have section all concepts havethe same score on four points, since they make the same difference.All have also been left without a score on four of the categories,since it is not possible to tell if there will be any changes due to theplacement of the variable valve. Highest score, due to easy replace-ment, easily accessed and mountable on already produced vehiclesis concept number two, placing the valve in the valve block of thesteering device.

The placement of the valve does affect the performance accordingto presented results. Comparing the three placements there is onewhich have an unpredictable behaviour, which is the position inthe front waggon. Position 1 and 2 are very similar, differing onlywith a small phase shift and shape. Designing a semi-active systempredictability is a good thing, receiving a sine as input and givingit back as output. Position 3 could possibly create spikes of flow inthe system, which is why it is not preferable. Therefore, togetherwith the evaluation matrix this result gives position 2 as the bestplacement of the valve. Position 2 is in the valve block in thesteering device. It is one of the few places where there still areenough space and it is close to both the cylinders and the supplyin the front waggon.

27

Chapter 6

DiscussionThe methodology used work well. However, due to the narrowdesign space only a few concepts could be generated. Since theproduct development process heavily relies on concept generation,a better suited methodology could possibly have been found.

The software used was very helpful. It is hard to evaluate the re-sults from the simulations, and the setup was not perfect. Sincethe pressure were the same on both sides of the piston, the cylindercontracted. It was therefore hard to do any test without a bias,were sine forces were helpful. To properly evaluate the response ofthe system, ramp and step input would have given valuable infor-mation. Even a simplified system becomes quite complex, whichmakes it difficult to evaluate with limited knowledge of hydraulicsand fluid mechanics. Due to the assumption that the default val-ues gives results good enough to evaluate the concepts, the fluidmechanic simulation has to be remade taking the variables intoaccount and validating the results.

The data from the simulation performed at BAE Systems in ADAMScan be questioned. For a proper evaluation of the system moremovement of the pistons are required. One problem was that thepistons sometimes would hit bottom, something which was neverclose during the eight simulations performed. A wider range of sim-ulations, some with lower damping, would be good for further de-velopment of the system. Looking at the vehicle dynamics chapterin the theory, low damping is preferred at low speeds for example inrough terrain, whereas high damping is good on even roads to pre-vent the vehicle from oscillating and keeping the front of the vehicledown. With the installation of the new solenoid valves from Öh-lins, it might be a good idea to increase the diameter of the currentchoke valve in the steering device valve block. Even though higher

28

damping is asked for, a larger span of available damping is advan-tageous for a semi-active or an active suspension system. Thereforechanging from the cylinders of today, to larger ones would increasethe potential of the system.

The requirement specification and evaluation matrix are designedto evaluate the steering device. Therefore, when deciding only onthe placements of the valve, most of them will be same for all al-ternatives. However, it was possible to get a varying scoring of theconcepts and the specification will be useful for further develop-ment.

The input for the control system should be as few points as possiblewith as much information as possible. Control points could be thetemperature of the oil, since the operating temperature has a rangefrom -46 to 100 degrees Celsius. Pressure sensors or accelerometersdifferent places on the vehicle could increase the preciseness of thesystem. Using brake input and the movements of the first supportwheel could predict the movement of the whole vehicle. Using theangle of the cylinders is a possible way to know the position of thepiston. In that way, a secondary bump stop can be created, as thehydraulic valve tightens as the piston is close to an end point. Avery simple but yet effective control would be from the velocity ofthe vehicle. It is seldom that the vehicle will have a high velocityin rough terrain, where low damping is required. In the same waywhere there will be a high velocity will the probability for an evenroad be very high, and higher damping is preferable.

29

Chapter 7

Conclusion andRecommendationsSince the reliability of the input data from ADAMS simulationscan be questioned, further simulations and testing need to be per-formed. However, the results shows that the hydraulic valves fromÖhlins Racing AB will work with the system and are dependent onwhere they are to be mounted. It also shows that increasing thediameter of the tilt cylinders will be advantageous for the system.

I recommend BAE Systems to perform further analysis of the move-ment of the tilt cylinders and the flow of the fluid it causes. In-vestigating not only higher damping, but also lower damping couldincrease the span of available damping, which could benefit thesemi-active system even more. A larger variety of full-vehicle simu-lations are needed, where both terrain, velocities and load cases arevaried more. I also recommend testing the solenoid valve to ensurethat the behaviour in pressures higher than 200 bar is satisfying.The fluid mechanics of the system also has to be further evaluated,using proper simulation models.

30

BibliographyAhmadian, M. and Pare C.A. (2000). “A quarter-car experimentalanalysis of alternative semi-active control methods.” In: J. Intell.Mater. Syst. 11, pp. 604–612.

BAE Systems (2014).How we work. url: http://www.baesystems.com/our-company-rgb/about-us/where-we-operate (visitedon 02/28/2014).

Cao, D.P. (2008). “Theoretical analysis of roll- and pitch-coupledhydro-pneumatic strut suspension.” In:

Chen, S., C-F. Zong, R-J Wu, and T-W. Zhang (2011). “Parame-ter Sensitivity Analysis of Automotive Ride Comfort.” In: Inter-national Conference on Consumer Electronics, Communicationsand Networks. Pp. 4256–4259.

Chung-Huan, S, G Cheer-Germ, S Ming-Hsiang, and S Wen-Pei(2010). “Validity of the displacement dependent semi-active hy-draulic damper used in a structure”. In: Journal of Vibration andControl 17.4, pp. 579–587.

Doddannavar, R, A Barnard, and S Machay (2005). Practical Hy-draulic Systems: Operation and Troubleshooting for Engineersand Technicians. Oxford, UK: Elsevier.

Els, P.S., N.J. Theron, P.E. Uys, and M.J. Thoresson (2007). “Theride comfort vs. handling compromise for off-road vehicles.” In:Journal of Terramechanics 44, pp. 303–317.

Faris, W.F., Z. BenLahcene, and F. Hasbullah (2012). “Ride qualityof passenger cars: an overview on the research trends.” In: Int. J.Vehicle Noise and Vibration 8, pp. 185–199.

31

http://www.baesystems.com/our-company-rgb/about-us/where-we-operatehttp://www.baesystems.com/our-company-rgb/about-us/where-we-operate

Giliomee, C.L. and P.S. Els (1998). “Semi-active hydropneumaticspring and damper system.” In: Journal of Terramechanics 35,pp. 109–117.

Gonzalez Prada, J., A. Alonso, J. Vinolas, X. Carrera, K. Rey-brouck, and J. Germán Giménez (2011). “Gas dampers: modeldevelopment and potential ride performance evaluation.” In: Ve-hicle System Dynamics 49, pp. 199–218.

Harty, D. (2005). “A review of dynamic intervention technologiesand a method to choose between them.” In: Vehicle dynamicsexpo, Open technology forum, May 31–June 2, Stuttgart Messe,Stuttgart, Germany.

Hunt, T and N Vaughan (1996). Hydraulic Handbook. 9th. Oxford,UK: Elsevier Advanced Technology.

Ingvast, Håkan (1990).Hydraulikens Grunder. 2nd. Östervåla: Tofterstryckeri ab.

Osvalder, A-L, L Rose, and S Karlsson (2008). In: Bohgard, M, SKarlsson, E Lovén, L-Å Mikaelsson, L Mårtensson, A-L Osvalder,L Rose, and P Ulfvengren. Arbete och Teknik på människansvillkor. 1st. Stockholm: Prevent. Chap. 9.

Quanan, H. and W. Huiyi (2004). “Fundamental study of jerk: Eval-uation of shift quality and ride comfort.” In: SAE Technical Paper2004-01-2065.

Rajamani, R. (2006). “Vehicle Dynamics and Control.” In: Springer,New York.

Ulrich, K.T. and S.D. Eppinger (2003). Product Design and Devel-opment. 3rd. New York: McGraw-Hill/Irwin.

Uys, P.E., P.S. Els, and M.J. Thoresson (2006). “Criteria for han-dling measurement.” In: Journal of Terramechanics 43, pp. 43–67.

Van de Ven, J.D. (2013). “On Fluid Compressibility in Switch-ModeHydraulic Circuits - Part I: Modeling and Analysis”. In: Journal

32

of Dynamic Systems, Measurement and Control, Transactions ofthe ASME 135.2.

Vestman, A (2014). “Analys av aktivt fjädringssystem för BVS10”.MA thesis. Luleå University of Technology.

Yin, Z., A. Khajepour, D. Cao, B. Ebrahimi, and K. Guo (2012).“A new pneumatic suspension system with independent stiffnessand ride height tuning capabilities.” In: Vehicle System Dynamics50.12, pp. 1735–1746.

33

List of Figures

1.1 The armoured all terrain vehicle, BvS10 . . . . . . . 1http://www.baesystems.com/image/BAES_021029/lemur-on-bvs10(visited on 02/28/2014)

1.2 The BvS10 with the steering device . . . . . . . . . . 2http://www.deagel.com/library1/medium/2010/m02010061500103.jpg(visited on 02/28/2014)

2.1 SAE coordinate system . . . . . . . . . . . . . . . . 4http://www.neweagle.net/support/wiki/images/0/01/ChassiControlsCar.png(visited on 03/09/2014)

2.2 A double-acting single ended hydraulic cylinder . . . 8Beater, P (2007).Pneumatic Drives: System Design, Modelling and Con-trolBerlin: Springer-Verlag, chap. 8.1

3.1 The product development process by Ulrich and Ep-pinger (2003) . . . . . . . . . . . . . . . . . . . . . 10Ulrich, K.T. and S.D. Eppinger (2003).Product Design and Develop-ment.3rd.New York: McGraw-Hill/Irwin, pp.54

4.1 The steering device with all fittings . . . . . . . . . . 134.2 Showing translations and rotations of the steering

device . . . . . . . . . . . . . . . . . . . . . . . . . 14a Side view . . . . . . . . . . . . . . . . . . . . 14b Top view . . . . . . . . . . . . . . . . . . . . 14

4.3 Showing different positions where the semi-active valvecould be placed . . . . . . . . . . . . . . . . . . . . . 16a Side view . . . . . . . . . . . . . . . . . . . . 16b Top view . . . . . . . . . . . . . . . . . . . . 16

4.4 Tracks used for simulations . . . . . . . . . . . . . . 17a The RMS-track used in ADAMS simulations 17b The RMS-track used in ADAMS simulations 17Vestman, A (2014).Analys av aktivt fjädringssystem för BVS10

35

http://www.baesystems.com/image/BAES_021029/lemur-on-bvs10http://www.deagel.com/library1/medium/2010/m02010061500103.jpghttp://www.neweagle.net/support/wiki/images/0/01/ChassiControlsCar.pnghttp://www.neweagle.net/support/wiki/images/0/01/ChassiControlsCar.png

4.5 Displacement of the rear cylinder . . . . . . . . . . 18

5.1 Front Cylinder volume change during RMS-track . . 21a Current damping . . . . . . . . . . . . . . . 21b Highest damping . . . . . . . . . . . . . . . . 21

5.2 Rear Cylinder volume change during APG-track . . 22a Current damping . . . . . . . . . . . . . . . 22b Highest damping . . . . . . . . . . . . . . . . 22

5.3 Flow measured with different positions of the valve . 24a Measured flow in the valve block of the steer-

ing device . . . . . . . . . . . . . . . . . . . 24b Measured flow in the valve block of the front

waggon . . . . . . . . . . . . . . . . . . . . . 245.4 Rear Cylinder during sine input . . . . . . . . . . . 25

a 50 Hz sine . . . . . . . . . . . . . . . . . . . 25b 100 Hz sine . . . . . . . . . . . . . . . . . . 25

5.5 Evaluation Matrix . . . . . . . . . . . . . . . . . . . 26

36

Appendix I

Tilt CylindersProvided by BAE System Hägglunds AB

3761838 Front Cylinder Data Sheet3714500 Rear Cylinder Data Sheet

Company Secrecy Level National Defence Secrecy Level

Export Control

Intern / Unclassified Ej försvarssekretess / Not Protectively Marked

Ej behandlad Ej begränsad / Not Restricted Hägglunds No: 47 7733, Rev: 1 (1)

i

Company Secrecy Level National Defence Secrecy Level

Export Control

Intern / Unclassified Ej försvarssekretess / Not Protectively Marked

Ej behandlad Ej begränsad / Not Restricted Hägglunds No: 47 7735, Rev: 1 (1)

ii

Appendix II

Requirement Specificationand Evaluation Matrix

Need to have

No

.

Imp

ort

ance

1Th

e im

pro

ved

ste

erin

g d

evic

e 5

2Th

e im

pro

ved

ste

erin

g d

evic

e 5

3Th

e im

pro

ved

ste

erin

g d

evic

e 5

4Th

e im

pro

ved

ste

erin

g d

evic

e 5

5Th

e im

pro

ved

ste

erin

g d

evic

e 5

6Th

e im

pro

ved

ste

erin

g d

evic

e 5

7Th

e im

pro

ved

ste

erin

g d

evic

e 5

8Th

e im

pro

ved

ste

erin

g d

evic

e 5

9Th

e im

pro

ved

ste

erin

g d

evic

e 5

10

The

imp

rove

d s

teer

ing

dev

ice

5

No

.M

etr

icU

nit

sM

argi

nal

Val

ue

Ide

al V

alu

e

1M

easu

re t

he

osc

illat

ion

, rm

s je

rk a

nd

acc

eler

atio

ns.

m/s

^3 &

m/s

^2?

?

2M

easu

re t

he

angl

e o

f th

e m

axim

um

tilt

.D

egre

es±3

0°

≤30

°, ≥

30

°

3M

easu

re t

he

angl

e o

f th

e m

axim

um

ste

erin

g o

utp

ut.

Deg

rees

±45

°≤4

5°,

≥4

5°

4M

easu

re t

he

angl

e o

f ro

tati

on

.D

egre

es±4

0°

≤40

°, ≥

40

°

5C

on

firm

atio

n t

hro

ugh

vir

tual

mo

del

Bin

ary

--

6C

om

po

nen

t te

stin

g in

th

e te

mp

erat

ure

ran

ge.

Deg

rees

Cel

siu

s-4

6 t

o +

10

0-4

6 t

o +

12

0

7C

on

firm

wit

h c

om

po

nen

ts r

ead

y fo

r se

mi-

acti

ve c

on

tro

ls.

Bin

ary

--

8Lo

ok

for

leak

ages

.B

inar

y-

-

9C

on

firm

atio

n t

hro

ugh

veh

icle

tes

tin

g.B

inar

y-

-

10

Hav

e a

fixe

d b

reak

ing

stre

ngt

h o

f th

e fa

sten

ing

of

the

pis

ton

.kN

22

42

24

No

.

Imp

ort

ance

11

The

imp

rove

d s

teer

ing

dev

ice

5

12

The

imp

rove

d s

teer

ing

dev

ice

3

13

The

imp

rove

d s

teer

ing

dev

ice

4

14

The

imp

rove

d s

teer

ing

dev

ice

2

15

The

imp

rove

d s

teer

ing

dev

ice

2

16

The

imp

rove

d s

teer

ing

dev

ice

5

17

The

imp

rove

d s

teer

ing

dev

ice

3

18

The

imp

rove

d s

teer

ing

dev

ice

2

19

The

imp

rove

d s

teer

ing

dev

ice

4

20

The

imp

rove

d s

teer

ing

dev

ice

2

21

The

imp

rove

d s

teer

ing

dev

ice

5

22

The

imp

rove

d s

teer

ing

dev

ice

3

No

.M

etr

icU

nit

sM

argi

nal

Val

ue

Ide

al V

alu

e

11

Tota

l wei

ght

of

the

stee

rin

g d

evic

e (w

ith

ou

t tu

bin

g an

d v

alve

pac

kage

).kg

20

%

21

Mea

sure

th

e re

spo

nse

tim

e.m

s≤5

00

≤10

0

22

Mea

sure

th

e fo

rces

an

d s

trai

ns,

or

the

oil

pre

ssu

res

in t

he

tilt

cyl

ind

ers.

kN, b

arSa

me

as t

od

ayLe

ss t

han

to

day

red

uce

s w

ear

in t

he

com

po

nen

ts b

etw

een

th

e b

od

ies.

can

be

mai

nta

ined

wit

h r

ead

ily a

vaili

able

to

ols

.

has

hig

h r

ob

ust

nes

s.

incr

ease

s m

ob

ility

.

has

th

e ab

ility

to

res

po

nd

qu

ickl

y to

th

e se

mi-

acti

ve s

yste

m.

red

uce

s th

e fo

rces

in t

he

stee

rin

g d

evic

e an

d t

he

hu

ll at

tach

men

ts.

has

low

wei

ght.

will

eas

ily d

eco

up

le t

he

bo

die

s.

is c

hea

p.

can

be

easi

ly a

cces

sed

fo

r m

ain

ten

ance

in t

he

fiel

d.

allo

ws

easy

rep

lace

men

t o

f w

orn

par

ts.

is m

ou

nta

ble

on

alr

ead

y p

rod

uce

d v

ehic

les.

is r

esis

tan

t to

tem

per

atu

res.

is r

ead

y fo

r se

mi-

acti

ve c

on

tro

l.

is t

igh

tly

seal

ed, p

reve

nti

ng

oil

leak

age.

mak

es s

ure

th

e ve

hic

le is

dri

vab

le e

ven

if t

he

tilt

ing

cylin

der

s ar

e b

roke

n.

has

a c

on

tro

lled

bra

kin

g p

oin

t in

th

e re

ar t

ilt c

ylin

der

.

Go

od

to

hav

e

Ne

ed

to

hav

e

min

imis

es t

he

acce

lera

tio

n a

nd

jerk

at

the

dri

vers

' sea

t.

allo

ws

tilt

ing

the

veh

icle

.

pre

serv

es t

he

stee

rin

g ch

arac

teri

stic

s o

f th

e ve

hic

le.

allo

ws

rota

tio

n b

etw

een

th

e tw

o b

od

ies.

fits

in t

he

exis

tin

g sp

ace

bet

wee

n t

he

bo

die

s.

i

Good to have

No

.

Imp

ort

ance

1Th

e im

pro

ved

ste

erin

g d

evic

e 5

2Th

e im

pro

ved

ste

erin

g d

evic

e 5

3Th

e im

pro

ved

ste

erin

g d

evic

e 5

4Th

e im

pro

ved

ste

erin

g d

evic

e 5

5Th

e im

pro

ved

ste

erin

g d

evic

e 5

6Th

e im

pro

ved

ste

erin

g d

evic

e 5

7Th

e im

pro

ved

ste

erin

g d

evic

e 5

8Th

e im

pro

ved

ste

erin

g d

evic

e 5

9Th

e im

pro

ved

ste

erin

g d

evic

e 5

10

The

imp

rove

d s

teer

ing

dev

ice

5

No

.M

etr

icU

nit

sM

argi

nal

Val

ue

Ide

al V

alu

e

1M

easu

re t

he

osc

illat

ion

, rm

s je

rk a

nd

acc

eler

atio

ns.

m/s

^3 &

m/s

^2?

?

2M

easu

re t

he

angl

e o

f th

e m

axim

um

tilt

.D

egre

es±3

0°

≤30

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re t

he

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rees

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≥4

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re t

he

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.D

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n t

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ary

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om

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Deg

rees

Cel

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6 t

o +

10

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6 t

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.B

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h o

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the

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24

No

.

Imp

ort

ance

11

The

imp

rove

d s

teer

ing

dev

ice

5

12

The

imp

rove

d s

teer

ing

dev

ice

3

13

The

imp

rove

d s

teer

ing

dev

ice

4

14

The

imp

rove

d s

teer

ing

dev

ice

2

15

The

imp

rove

d s

teer

ing

dev

ice

2

16

The

imp

rove

d s

teer

ing

dev

ice

5

17

The

imp

rove

d s

teer

ing

dev

ice

3

18

The

imp

rove

d s

teer

ing

dev

ice

2

19

The

imp

rove

d s

teer

ing

dev

ice

4

20

The

imp

rove

d s

teer

ing

dev

ice

2

21

The

imp

rove

d s

teer

ing

dev

ice

5

22

The

imp

rove

d s

teer

ing

dev

ice

3

No

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etr

icU

nit

sM

argi

nal

Val

ue

Ide

al V

alu

e

11

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l wei

ght

of

the

stee

rin

g d

evic

e (w

ith

ou

t tu

bin

g an

d v

alve

pac

kage

).kg

20

%

21

Mea

sure

th

e re

spo

nse

tim

e.m

s≤5

00

≤10

0

22

Mea

sure

th

e fo

rces

an

d s

trai

ns,

or

the

oil

pre

ssu

res

in t

he

tilt

cyl

ind

ers.

kN, b

arSa

me

as t

od

ayLe

ss t

han

to

day

red

uce

s w

ear

in t

he

com

po

nen

ts b

etw

een

th

e b

od

ies.

can

be

mai

nta

ined

wit

h r

ead

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vaili

able

to

ols

.

has

hig

h r

ob

ust

nes

s.

incr

ease

s m

ob

ility

.

has

th

e ab

ility

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res

po

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y to

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yste

m.

red

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s th

e fo

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in t

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g d

evic

e an

d t

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hu

ll at

tach

men

ts.

has

low

wei

ght.

will

eas

ily d

eco

up

le t

he

bo

die

s.

is c

hea

p.

can

be

easi

ly a

cces

sed

fo

r m

ain

ten

ance

in t

he

fiel

d.

allo

ws

easy

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lace

men

t o

f w

orn

par

ts.

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ou

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ble

on

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esis

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ead

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igh

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mak

es s

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hic

le is

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ven

if t

he

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ing

cylin

der

s ar

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roke

n.

has

a c

on

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lled

bra

kin

g p

oin

t in

th

e re

ar t

ilt c

ylin

der

.

Go

od

to

hav

e

Ne

ed

to

hav

e

min

imis

es t

he

acce

lera

tio

n a

nd

jerk

at

the

dri

vers

' sea

t.

allo

ws

tilt

ing

the

veh

icle

.

pre

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es t

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g ch

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s o

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hic

le.

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ws

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tio

n b

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e tw

o b

od

ies.

fits

in t

he

exis

tin

g sp

ace

bet

wee

n t

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bo

die

s.

ii

Evaluation Matrix

Imp

ort

ance

Co

nce

pt

1C

on

cep

t 2

Co

nce

pt

3

5-

--

52

52

52

5

52

52

52

5

52

52

52

5

52

52

52

5

52

52

52

5

52

52

52

5

52

52

52

5

52

52

52

5

52

52

52

5

Tota

l2

25

22

52

25

Imp

ort

ance

Co

nce

pt

1C

on

cep

t 2

Co

nce

pt

3

52

52

52

5

31

51

51

5

41

21

21

2

22

10

6

22

10

6

50

25

25

3-

--

21

01

01

0

4-

--

2-

--

52

52

52

5

3-

--

Tota

l9

11

32

12

4

Red

uce

s w

ear

in t

he

com

po

nen

ts b

etw

een

th

e b

od

ies.

Can

be

mai

nta

ined

wit

h r

ead

ily a

vaili

able

to

ols

.

Has

hig

h r

ob

ust

nes

s.

Incr

ease

s m

ob

ility

.

Has

th

e ab

ility

to

res

po

nd

qu

ickl

y to

th

e se

mi-

acti

ve s

yste

m.

Red

uce

s th

e fo

rces

in t

he

ste

erin

g d

evic

e an

d t

he

hu

ll at

tach

men

ts.

Has

low

we

igh

t.

Will

eas

ily d

eco

up

le t

he

bo

die

s.

Is c

hea

p.

Can

be

easi

ly a

cces

sed

fo

r m

ain

ten

ance

in t

he

fiel

d.

Allo

ws

easy

rep

lace

men

t o

f w

orn

par

ts.

Is m

ou

nta

ble

on

alr

ead

y p

rod

uce

d v

ehic

les.

Is r

esis

tan

t to

tem

per

atu

res.

Is r

ead

y fo

r se

mi-

acti

ve c

on

tro

l.

Is t

igh

tly

seal

ed, p

reve

nti

ng

oil

leak

age.

Mak

es s

ure

th

e ve

hic

le is

dri

vab

le e

ven

if t

he

tilt

ing

cylin

der

s ar

e b

roke

n.

Has

a c

on

tro

lled

bra

kin

g p

oin

t in

th

e re

ar t

ilt c

ylin

der

.

Go

od

to

hav

e

Nee

d t

o h

ave

Min

imis

es t

he

acce

lera

tio

n a

nd

jerk

at

the

dri

vers

' se

at.

Allo

ws

tilt

ing

the

veh

icle

.

Pre

serv

es t

he

ste

erin

g ch

arac

teri

stic

s o

f th

e ve

hic

le.

Allo

ws

rota

tio

n b

etw

een

th

e tw

o b

od

ies.

Fits

in t

he

exis

tin

g sp

ace

bet

we

en t

he

bo

die

s.

iii

Appendix III

Simulink Model

Rear Cylinder

i

Front Cylinder

ii

Appendix IV

Solenoid Valve CES8700Provided by Öhlins Racing AB

Product data sheetProduct Document version Replaces document version Page

CES8700 Hydraulic Valve 7 6 1(11)

Öhlins Racing CES Technologies

CES8700 HYDRAULIC VALVE

Contents

Introduction ......................................2Valve tuning .....................................3Hydraulic Characteristics .................4Mechanical Interface......................10Electrical Characteristics................10Temperature Range.......................11Packing and shipping.....................11

Features

Pilot controlled 2-stage pressure control valve External mounting on uniflow shock absorbers Öhlins patented soft opening main stage Robust failsafe functionality Integrated coil and connector

i



Öhlins Racing CES Technologies

Introduction

Overview

This document describes the general technical characteristics and interfaces for the CES8700 hydraulic valve. The document also includes a summary of the most important validation tests made on the different CES8700 valve versions. These tests are primarily developed to cover the use of CES-technology on passenger cars. The CES8700 valve can also be used for other applications. This document should be used as a guideline for valve selection in the shock absorber tuning process.

CES8700 Hydraulic Valve

The CES8700 hydraulic valve is built upon Öhlins patented CES technology (Continuously Controlled Electronic Suspension) that adapts the damping force in semi-active shock absorbers to the condition of the road and preferred settings by the driver for maximum car control and passenger comfort. The CES8700 hydraulic valve is a further development of the successful CES4600 hydraulic valve and offers a wider working range and more tuning possibilities. With the patented soft opening function and the new hybrid function, the good NVH performance has further improved. The CES8700 hydraulic valve has a compact design, is very suitable for skyhook control implementations and has pressure and flow range that cover most of passenger car applications.

ii



Öhlins Racing ABCES Technologieswww.ohlins.com

Valve tuningThe valves hydraulic characteristics are tuneable. The relation between control current and pressure levels depend on the chosen tuning parameters.

CES8700X5641D

Main spring rate:

Pilot Shim rate: 0 40N/mm 2 20N/mm4 5N/mm

Pilot Diameter:

Main Stage:

K 12N/mm A 27N/mmI 49N/mmD 75N/mm

4 3.4mm 5 3.5mm6 3.6mm7 3.7mm

0 Normal flow4 High pressure5 High flow

Generation

Ex. 5641D = High flow valve with Ø 3.6 mm pilot seat, 5 N/mm pilot shim spring and a 75 N/mm main spring.

Each valve is labeled with an id number, so traceability is secured.

Marking area

iii




Hydraulic Characteristics

General

The valve is of uniflow type which means that the direction of flow is the same for both compression and rebound mode of the damper. The valve is primarily designed for triple tube shock absorbers with internal blow-off valves working in rebound and compression stroke. The characteristics of the valve also make it suitable for other applications where a pressure drop is electronically controlled.

Pressure Drop Characteristics

The pressure drop characteristic of the valve is progressive relative to flow at all points. Differences in pressure levels between compression and rebound are generally determined by the shock absorbers geometry. In some applications two separate valves can be used to further improve the balance between compression and rebound and the behaviour of the damper. One valve for each direction.

Figure 1: Graph showing total working range at max. (green) and bias (blue) current for CES8700.

iv




Figure 2: Graph showing working range at max. (green) and bias (blue) current for valves with high flow main stage.

Figure 3: Graph showing working range at max. (green) and bias (blue) current for valves with normal flow main stage.

Flow (l/min)

v




Figure 4: Graph showing working range at max. (green) and bias (blue) current for valves with high pressure main stage.

Bias CurrentBias current is the lowest current level required for pressure control. Bias current is recommended to be 0.32A for high flow valves and 0.38A for normal flow and high pressure valves.

RestrictionRestriction in series with the valve is used for all tests. The restriction diameter is Ø3.5 mm for normal flow and high pressure valves and Ø6 mm for high flow valves. Recommended restriction is between Ø3.5 mm and Ø6 mm.

vi




FailsafeThe failsafe function keeps the valve operational in the event of power failure. The failsafe mode is a safety function that makes the damper act as a conventional passive shock absorber when no current is applied. This is not normal operating mode and should not be used for other than a “limp-home” solution.

Figure 5: Typical values for fail safe pressure level with different main stages.

vii




Transition current characteristics (Hybrid Function)The hybrid function of the CES8700 valve means that when applying lower currents, the valve shows a behavior like a bleed controlled valve while applying higher currents, the behavior is more like a pressure controlled valve. The current where the transition between characteristics occurs depends mainly on the stiffness of the pilot shim spring. The bleed characteristics at low flow and pressure give a high level of comfort due to low pressure levels at direction changes of the damping. At currents over the transition current, the valve shows a more linear behavior.

Transition current:

5N/mm 20N/mm 40N/mm0.4A 0.6A 0.8A

Figure 6: PI-graphs showing the transition characteristics from bleed to pressure control.

viii




Flow Range

The CES8700 valve flow range is 0-100 l/min. Check specific prototype specification for more information on limitations in flow due to pressure limit.

Maximum Pressure Levels

Max. operational pressure 20 MPaProof pressure 25 MPaMin burst pressure 40 MPa

ASR – Active Step Response

The step response is measured at constant flow. The response time is defined as the time from 10% of the total current step to 90% of the total pressure step when applying a step in control current. For more information see specific prototype specification.

Scatter

The scatter is statistically calculated based normal distribution and 3-sigma for each valve type. Scatter on nominal pressure drop in controlled working range up to 40l/min. For more information see specific prototype specification.

Oil

For all hydraulic specifications and validation Fuchs Titan SAF 5045 EU 137 (standard shock absorber oil) is used.

Chemical and physical properties

Property Data

Density 15ºC 843 kg/m3

Viscosity 20ºC 20.7 mm2/s

Viscosity 40ºC 12.3 mm2/s

Viscosity 100ºC 4.43 mm2/sViscosity -40ºC 491 mPasViscosity index 340

Preferred cleanliness see, Contamination guideline SPEC-1713.

Back Pressure

Recommended absolute static pressure in the shock absorber reserve volume is 20 bar. Recommended absolute dynamic pressure in the reserve volume of the shock absorber is 30 bar. The pressure drop over the valve is independent of back pressure created at the valve outlet.

ix




Mechanical InterfaceWeight - Approximately 200g for CES valve and coil

Mounting - The valve is mounted in the shock absorber cavity, thread M30x1.5, with a 15Nm torque.

Drawings

Dimensions and interface layout according to Öhlins drawing 20137-01.

Electrical Characteristics

Current

The solenoid is current driven. Working range is between 0.32/0.38 A to 1.6 A (max. current). The applied current can be PWM modulated (fmin 2000 Hz) and dithered and no instabilities will occur in the valve.

Maximum Continuous Current

Maximum current is 1.6A and the time for applied maximum current is dependant of the ambient temperature and the heat build-up in the shock. Max. allowed temperature in the winding is 180 ºC.

Maximum Peak Current

The maximum peak current is 2 A and can be applied for a very short time period (less than 1 sec).

Voltage

The CES valve is current controlled, the voltage becomes a function of resistance, current and temperature. Typical voltage at 1.0 A and 25 ºC is 4.7 V.

Resistance

4.6±0.5 Ω at 23±5°C (Measured on the connector pins)7.4±0.5 Ω at 180±5°C (Measured on the connector pins)

Resistance, dependency of temperature

Counted from values in table above = 0.35Ω / 20°C

x




Inductivity

Measured on the valve with stroke=0 (Anchor in outmost position = working position), the solenoid is to be mounted in the armature.

Function: Ls-Rs Level: 1.00 Volt

Range: Auto Bias: 0.00 Volt Integ: Long

Frequency Ls(mH) ±10% Rs(Ohm) ±10%20Hz 26.8 5.1100Hz 22.1 9.71000Hz 8.2 44.910000Hz 2.6 136100000Hz 1.5 505

Temperature RangeThe operating temperature range of the solenoid is -40 to 150 ºC.

Proper solenoid function is not guaranteed after being subjected to temperatures of 180 ºC or higher.

Packing and shippingPacking quantity: 120 pcs / 1 box (valves are packed in trays containing 15 valves. Trays are packed in boxes containing 8 trays). No more than 32 boxes are packed on each pallet when shipped.

Weight: 14.7 kg / 1 box

Packing info: Each box is labeled with an ODETTE label

Storing: Valves are to be stored in shipping trays placed standing with armature facing down in a dry and dust free location.

© All rights reserved

Öhlins Racing AB

Head office:

Instrumentvägen 8-10, Box 722, 194 27 Upplands VäsbyTel. +46 8-590 025 00, fax +46 8-590 025 80

CES Technologies:

Barrsätragatan 4D, 55626 JönköpingTel. +46 36-317 450 , fax +46 36 317 469

xi

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