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Technical Paper

Motion Cueing Evaluation of Off-Road Heavy Vehicle Handling

2016-09-27
2016-01-8041
Motion cueing algorithms can improve the perceived realism of a driving simulator, however, data on the effects on driver performance and simulator sickness remain scarce. Two novel motion cueing algorithms varying in concept and complexity were developed for a limited maneuvering workspace, hexapod/Stuart type motion platform. The RideCue algorithm uses a simple swing motion concept while OverTilt Track algorithm uses optimal pre-positioning to account for maneuver characteristics for coordinating tilt adjustments. An experiment was conducted on the US Army Tank Automotive Research, Development and Engineering Center (TARDEC) Ride Motion Simulator (RMS) platform comparing the two novel motion cueing algorithms to a pre-existing algorithm and a no-motion condition.
Journal Article

Ultra Boost for Economy: Extending the Limits of Extreme Engine Downsizing

2014-04-01
2014-01-1185
The paper discusses the concept, design and final results from the ‘Ultra Boost for Economy’ collaborative project, which was part-funded by the Technology Strategy Board, the UK's innovation agency. The project comprised industry- and academia-wide expertise to demonstrate that it is possible to reduce engine capacity by 60% and still achieve the torque curve of a modern, large-capacity naturally-aspirated engine, while encompassing the attributes necessary to employ such a concept in premium vehicles. In addition to achieving the torque curve of the Jaguar Land Rover naturally-aspirated 5.0 litre V8 engine (which included generating 25 bar BMEP at 1000 rpm), the main project target was to show that such a downsized engine could, in itself, provide a major proportion of a route towards a 35% reduction in vehicle tailpipe CO2 on the New European Drive Cycle, together with some vehicle-based modifications and the assumption of stop-start technology being used instead of hybridization.
Journal Article

The Influence of Residual Gas NO Content on Knock Onset of Iso-Octane, PRF, TRF and ULG Mixtures in SI Engines

2013-12-20
2013-01-9046
Reported in the current paper is a study of the effects of Nitric Oxide (NO) within a simulated Exhaust Gas Residual (sEGR) on Spark Ignition (SI) engine end gas autoignition. A modified version of the single cylinder Leeds University Ported Optical Engine Version 2 (LUPOE-2) engine was designed to completely eliminate retained residual gas and so allow unambiguous definition of the composition of the in-cylinder charge. The engine was alternately operated on stoichiometric mixtures of iso-octane, two Primary Reference Fuels (PRF), a Toluene Reference Fuel (TRF), and a commercially available Unleaded Gasoline (ULG) and air. These mixtures were diluted with sEGR (products of the complete stoichiometric combustion of the given fuel/air mixture) in mass fractions ranging from 0-15%; with and without 5000ppm NO (0.52% by mass) within that sEGR.
Technical Paper

Piston Assembly Friction Losses: Comparison of Measured and Predicted Data

2006-04-03
2006-01-0426
The main objective of this research was to validate the friction prediction capability of Ricardo Software products PISDYN and RINGPAK by comparing predictions with measured piston assembly friction force. The measurements were made by the University of Leeds on a single cylinder Ricardo Hydra gasoline engine using an IMEP method developed by the University. This technique involves the use of advanced instrumentation to make accurate measurements of cylinder pressure, crankshaft angular velocity and connecting rod strain. These measured values are used to calculate the forces acting on the piston assembly including the friction force. PISDYN was used by Ricardo to calculate friction force at the interface between the piston skirt and cylinder liner. The model used includes the effects of secondary dynamics, partial lubrication and piston skirt profile. RINGPAK was used by Ricardo to calculate the friction force at each piston ring.
Technical Paper

Design of a Robust Tyre Force Estimator Using an Extended Kalman Filter

2005-04-11
2005-01-0402
This paper will present a method of estimating tyre friction force using an extended Kalman filter (EKF). A review of current and proposed methods for tyre force estimation from the literature will be given. The EKF developed will estimate vehicle motions and tyre forces as state estimates from a noisy measurement set. The tyre forces will be compared to those from a high order vehicle model with non-linear tyres, which is subjected to the same tests as the measured vehicle, in order to validate the estimated forces. The robustness of the estimator to noise and input errors will be tested. The ultimate aim of this work is to provide estimates of tyre forces to a controller such as ABS or TCS.
Technical Paper

Integration of Active Suspension and Active Driveline to Ensure Stability While Improving Vehicle Dynamics

2005-04-11
2005-01-0414
Most active control systems developed for passenger vehicles are developed as safety systems. These control systems usually focus on improving vehicle stability and safety while ignoring the effects on the vehicle driveability. While stability is the primary concern of these control systems the driveability of the vehicle is also an important consideration. An example of compromised driveability in a stability control system is brake based active yaw control. Brake based systems are very effective at stability control but can have a negative impact on the longitudinal dynamics of a vehicle. The objective of the vehicle control systems developed for the future will be to preserve vehicle driveability while ensuring the stability of the vehicle. In this work, active suspension and active drivelines are developed as stability control systems that have a minimal impact on the driveability of the vehicle.
Technical Paper

Integration of Active Suspension and Active Driveline to Improve Vehicle Dynamics

2004-11-30
2004-01-3544
Many active control systems are developed as safety systems for passenger vehicles. These control systems usually focus on improving vehicle stability and safety while ignoring the effects on the vehicle driveability. In the motorsport environment, increased stability is desirable but not if the driveability of the vehicle is heavily compromised. In this work, active suspension and active drivelines are examined to improve vehicle dynamics and enhance driveability while maintaining stability. The active control systems are developed as separate driveability and stability controls and tested individually then integrated to create a multi-objective control system to improve both driveability and stability. The controllers are tested with standard vehicle manoeuvres.
Technical Paper

The Influence of Simulated Residual and NO Concentrations on Knock Onset for PRFs and Gasolines

2004-10-25
2004-01-2998
Modern engine developments result in very different gas pressure-temperature histories to those in RON/MON determination tests and strain the usefulness of those knock scales and their applicability in SI engine knock and HCCI autoignition onset models. In practice, autoignition times are complex functions of fuel chemistry and burning velocity (which affects pressure-temperature history), residual gas concentration and content of species such as NO. As a result, autoignition expressions prove inadequate for engine conditions straying far from those under which they were derived. The currently reported study was designed to separate some of these effects. Experimental pressure crank-angle histories were derived for an engine operated in skip-fire mode to eliminate residuals. The unburned temperature history was derived for each cycle and was used with a number of autoignition/knock models.
Technical Paper

Integrated Active Steering and Variable Torque Distribution Control for Improving Vehicle Handling and Stability

2004-03-08
2004-01-1071
This paper proposes an advanced control strategy to improve vehicle handling and directional stability by integrating either Active Front Steering (AFS) or Active Rear Steering (ARS) with Variable Torque Distribution (VTD) control. Both AFS and ARS serve as the steerability controller and are designed to achieve the improved yaw rate tracking in low to mid-range lateral acceleration using Sliding Mode Control (SMC); while VTD is used as the stability controller and employs differential driving torque between left and right wheels on the same axle to produce a relatively large stabilizing yaw moment when the vehicle states (sideslip angle and its angular velocity) exceed the reference stable region defined in the phase plane. Based on these stand-alone subsystems, an integrated control scheme which coordinates the control actions of both AFS/ARS and VTD is proposed. The functional difference between AFS and ARS when integrated with VTD is explained physically.
Technical Paper

Drum Brake Contact Analysis and its Influence on Squeal Noise Prediction

2003-10-19
2003-01-3348
A non-linear contact analysis of a leading-trailing shoe drum brake, using the finite element method, is presented. The FE model accurately captures both the static and pseudo-dynamic behaviour at the friction interface. Flexible-to-flexible contact surfaces with elastic friction capabilities are used to determine the pressure distribution. Static contact conditions are established by initially pressing the shoes against the drum. This first load step is followed by a gradual increase of applied rotation to the drum in order to define the maximum reacted braking torque and pseudo-dynamic pressure distribution at the transition point between sticking and sliding motion. The method clearly illustrates the changes in contact force that take place as a function of the applied pressure, coefficient of friction and initial gap between lining and rotor. These changes in contact area are shown to influence the overall stability and therefore squeal propensity of the brake assembly.
Technical Paper

Improving Performance of a 6×6 Off-Road Vehicle Through Individual Wheel Control

2002-03-04
2002-01-0968
This paper presents a method of control for a 6×6 series-configured Hybrid Electric Off-road Vehicle (HEOV). The vehicle concerned is an eight-tonne logistics support vehicle which utilizes Hub Mounted Electric Drives (HMED) at each of its six wheel stations. This set-up allows Individual Wheel Control (IWC) to be implemented to improve vehicle handling and mobility. Direct Yaw-moment Control (DYC) is a method of regulating individual wheel torque to control vehicle yaw motion, providing greater stability in cornering. When combined with both a Traction Control System (TCS) and an Anti-lock Braking System (ABS) the tire/road interaction is fully controlled, leading to improved control over vehicle dynamics, whilst also improving vehicle safety.
Technical Paper

A Digital Electronic Solution to Piston Telemetry

2000-06-19
2000-01-2032
This paper describes the design, development and operation of a digital electronic piston telemetry system. A feature is the multiplicity of operating modes, including two-way communication. The system has been demonstrated to work with thermocouples and accelerometers embedded in the piston of a very small engine at speeds of over 2000rev/m. The piston-mounted components can be fitted to a piston as small as 80mm diameter, and the size is reduced with every modification as smaller more powerful electronic components become available. Typical results are quoted in the paper
Technical Paper

Development and Analysis of a Prototype Controllable Suspension

1997-08-06
972691
Persisting concerns regarding ride comfort, directional stability and more recently road damage have caused the manufacturers of commercial vehicles to consider controllable suspension systems. An electronically controllable adaptive suspension that comprises a variable spring rate system, switchable damping and load levelling is proposed as a cost-effective solution. This paper describes the aforementioned system and provides an outline of the design scheme for a prototype system; practical issues such as system configuration/detail, control system requirements, etc., are discussed. The system is evaluated analytically and both ride and handling modes are examined. In conclusion, performance capabilities are defined and cost-benefit issues addressed.
Technical Paper

Mechanical Performance of V-Ribbed Belt Drives (Experimental Investigation)

1997-02-24
970006
A non-contacting laser displacement meter has been used for dynamic measurements of the radial movement of a v-ribbed belt (type 3PK) around the arc of wrap running on a belt testing rig. Accurate and repeatable results are possible. Using this device, the belt radial movement and the beginning of rib bottom / groove tip contact around the arc of wrap have been determined experimentally for v-ribbed belts. Slip, torque loss, maximum torque capacity and efficiency have been measured during the tests.
Technical Paper

The Influence of Circumferential Waviness of the Journal on the Lubrication of Dynamically Loaded Journal Bearings

1997-02-24
970216
Current trends in automotive engine design are towards smaller, lighter components operating under higher specific loads. Consequently, engine bearings are expected to operate under highly stressed conditions, with minimum lubricant film thicknesses falling below 1μm. There is, however, insufficient understanding of acceptable tolerances on surface geometry of bearing shells and crankshaft pins. Measurement data suggest that some engine crankpins are machined with as many as 21 circumferential lobes. Some lobes have amplitudes in excess of 5 μm and are thought to be responsible for premature bearing damage. This study presents results from a theoretical analysis of dynamically loaded journal bearings with circumferential lobes on the journal. The Reynolds equation for a rigid journal bearing is solved for an incompressible, Newtonian, iso-viscous lubricant, with a flow conserving cavitation model accommodating oil film history.
Technical Paper

Vehicle Handling Analysis Using Linearisation Around Non-Linear Operating Conditions

1996-02-01
960482
A non-linear example vehicle model including four degrees of freedom (yaw, sideslip, roll and steering), non-linear kinematics and the Magic Formula tyre model has been developed. With the assumption of small perturbations around any steady-state working condition, the linearised equations are derived. A novel approach is used for the linearisation of external forces and moments from the tyres. They are linearised in terms of the state variables rather than the slip angle, camber angle and vertical load which are themselves functions of the state variables. The results of this process are expressed in terms of stability derivatives. In order to use the method, the steady-state solution of the non-linear equations is first obtained for a particular value of lateral acceleration, then after the calculation of the stability derivatives, a linear analysis can be performed for the linear equations in terms of perturbed variables.
Technical Paper

A Theoretical and Experimental Study of the Modes of End Gas Autoignition Leading to Knock in S. I. Engines

1994-10-01
942060
A 2-D simulation of fluid dynamic and chemistry interaction following end gas autoignition has demonstrated three distinct modes of reaction, dependent upon the temperature gradient about an exothermic centre. All three modes (deflagration, developing detonation and thermal explosion) can contribute to knock; the developing detonation case, associated with intermediate temperature gradient, has been identified as the more damaging. The simulation code (LUMAD) has been used in a systematic parametric study designed to separate the complex interacting events which can lead to mixed modes in real engines. A most significant finding related to the sequential autoignition of multiple exothermic centres.
Technical Paper

Spatial Structure in End-Gas Autoignition

1993-10-01
932758
Numerical investigations are reported on the location of sites at which autoignition first develops in the end-gas ahead of a spark-ignited flame in a combustion chamber following rapid compression of an alkane + air mixture to high pressures and temperatures. Attention is drawn to the part played by the reactions that give rise to a negative temperature coefficient of reaction rate in an inhomogeneous temperature field. A ‘reduced’ kinetic mechanism was employed to model the spontaneous oxidation of n-alkanes. Flame propagation was described in terms of the ‘eddy dissipation concept’ and coupled to the more detailed mechanism by means of a switching algorithm. The CFD calculations were performed by use of KIVA II.
Technical Paper

Gasoline Engine Cycle Simulation Using the Leeds Turbulent Burning Velocity Correlations

1993-10-01
932640
A 3-zone thermodynamic cycle model has been developed which incorporates the Leeds correlations of turbulent burning velocity. The correlations encompass both the beneficial effects of turbulence in flame wrinkling and the detrimental effects of flame strain, which can lead to partial or total flame quench. Allowance has been made for the effects of “developing turbulence”, as the initially laminar flame kernel grows and is progressively influenced by larger scales of turbulence. Available experimental cylinder pressure and flame propagation data were used to check the plausibility of the simulation code and to establish values for the various constants employed to characterize the turbulence. The program was then used to explore the effects of engine speed, mixture strength, induction pressure and turbulence levels on the development of the combustion event.
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