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The adaptation of high capacity vehicles (HCVs) into existing commercial vehicle fleets have been considered a potential solution for reducing emissions, operational costs and infrastructure damages. However, due to increased length and number of articulations, there are challenges associated with HCVs with regard to their manoeuvrability at low-speeds and stability at high-speeds. This paper presents a Virtual Rigid Axle Command Steering control strategy for dolly steering, due to which both low- and high-speed performance of HCVs may be improved significantly compared to their conventional version with non-steered dolly. To demonstrate this, two HCVs, namely, A-double (tractor-semitrailer-dolly-semitrailer) and LHV-D (truck-dolly-semitrailer) are considered in this work.

Met de komst van lecoraten zijn hogescholen zich ook gaan richten op ‘toegepast onderzoek’. Maar past dat wel in het hbo? En zo ja, hoe implementeer je dat? Dit artikel beschrijft hoe binnen de HAN de competentie ‘Onderzoek doen’ hogeschoolbreed is ingekaderd.

During the previous HVTT conference in Melbourne, results have been presented of a project FORWARD, including eleven different trailer manufacturers, involving testing and modeling activities to establish a practical basis for realistic fatigue assessment as a step towards an improved light-weight trailer design. The present paper describes the next step as part of the follow-up project LIFE (LIfetime Fatique Enhancement), starting with the model-based assessment of a realistic loading history for a semi-trailer. Representative loading conditions in this history, being derived from three weeks of field testing, are then used in Finite Element analyses to estimate fatigue life at a critical high loaded welded connection in the aluminum trailer chassis. Results are discussed with respect to the order of different loading cycles (Palmgren-Miner number, based on fatigue tests), 3D loading at the weld, the varying weld quality, and the impact of bonded connections in the trailer. These ‘lessons learned’ are interpreted, to result in improved general guidelines in light-weight trailer design.

The paper discusses the derivation of test data for three tractor-semitrailer combinations, to be used for strength and durability analysis of semi-trailers with the ultimate goal to reduce the semitrailer mass. Mathematical relationships have been used to transfer these data to representative loading data for the semi-trailer, in terms of forces and moments in all directions at the axles and king-pin, being used to optimize weight without compromising the vehicle resistance to fatigue. These activities have been the starting point of a follow-up project FORWARD (Fuel Optimised trailer Referring to Well Assessed Realistic Design loads) including now eleven different trailer manufacturers, and the Dutch Chassis and Body work association FOCWA. FORWARD will extend the previous approach with the objective to lower the trailer weight in order to improve the ratio of payload to fuel consumption. FORWARD consists of the following steps (1) a testing program, the larger part of which corresponds to normal use for a representative period, (2) to apply these data to validate a vehicle model allowing the derivation of representative loading data, and exploration of the effect of design changes on these loading data, (3) to apply these loading data for further FEM analysis of the global chassis and of local critical points.

One way to reduce the fuel consumption to payload ratio of heavy vehicle combinations is to reduce the empty trailer weight. This requires an understanding of the vehicle structure, assembly techniques and production process, and of special materials (e.g. high strength steel) with emphasis on strength and fatigue. But in all cases, one needs to have realistic design loads available. This paper describes an approach to determine these loads as a first step in the process. For this purpose, tractor-semitrailer combinations have been tested under normal operational conditions, for a longer period, under monitoring of a large number of measurement data. These data have been transferred into dynamic loading data in terms of forces at each separate wheel and at the king-pin in vertical, lateral and longitudinal direction. The experience with several trailers has resulted in a cost-effective testing procedure, which also allows the assessment of representative loading cycles.

Continuously Variable Transmissions are used to optimize engine efficiencyin automotive drivelines. The efficiency profit however, is lost due to inefficiencies inthe CVT itself. These losses occur mainly in the (hydraulic) actuation system andin the variator. The losses can be lowered by minimizing the clamping force of thepulleys on the belt. Lowering the clamping force too much also leads to heavy slippingbetween belt and pulley, causing damage to the system.By controlling the clamping force in such a way that a limited amount of slip isallowed, the clamping force can be minimized without risking damage to the system.A nonlinear control scheme is used to control slip in the variator. Results show thatsuch a control method is feasible and robust to torque peaks.

In order to reduce the power consumption of a transmission, maximum tracking accuracy should be achieved of both ratio and pressures in the variator. A control strategy is proposed to steer a variator, actuated with a newly developed hydraulic system, of a Continuously Variable Transmission (CVT). The controller is model-based and used to reduce the interaction in the system in order to obtain accurate tracking of both pressures and ratio of the variator. For this purpose a model of the variator and hydraulics is proposed. Experimental results show that addition of a model-based controller improves the tracking accuracy of both pressure and ratio.

The NWO research programme called "Impulse Drive" focusses on design methodologies for hybrid vehicles with significant reduction of fuel consumption (50% - 75%) and CO2 emissions on a representative drive cycle. Powertrain hybridization implies adding a secondary power source or Energy Exchange System (EES) to a primary power source in order to increase the driving functions of a vehicle. The EES can enhancethe fuel consumption, emissions, comfort, driving performance and safety. In this paper a "bottom-up design process" is discussed, which focusses on determining the generic design specifications of the EES independent of the applied component technology and topology. In this paper the influence of an EES onenergy exchange with vehicle load and engine will be investigated separately. The simulation results show that the vehicle energy recovery efficiency is strongly determined by the motor/generator efficiencies, sizes and vehicle mass. The fuel economy is improved due to avoiding lower efficiency operation of the engine by increase of generator and motor size of the EES.

Toyota Motor Corporation developed the Toyota Hybrid System with CVT (THS-C) for the Toyota Estimaminivan. The THS-C is based on Toyota’s Super CVT (K110), where the conventional torque converter is replaced by a torsional damper and a newly developed motor/generator. For smooth switching between the different driving modes it makes use of wet multiple disc clutches and a planetary gearset arrangement. The Toyota Estima is also equipped with a motor/generator which directly drives or brakes the rear wheels for optimal vehicle dynamics and fuel economy. This feature will also be installed in the new hybrid Lexus RX400h, which is driven by an up-scaled version of the Prius powertrain. The powertrains in the mentioned vehicles are in fact an E-Four full hybrids with separate electric motors on front and rear axles. The first goal of this paper is to model the E-four of the Estima in ADVANCE; a coupled vehicle dynamics and powertrain simulation program developed by TNO Automotive. The second goal is to perform simulations with this software and evaluate the results. The results will be used to validate the THS-C as a technology carrier for ongoing and new research on integrated powertrain control and pulley CVTs for hybrids.

Rollover of trucks is a major problem. In The Netherlands, it occurs about twice a week, and the number is increasing. A factor contributing to this might be the maximised speed of commercial vehicles, not stimulating the driver to reduce this speed in potentially critically conditions. Several causes can be identified, one of them is excessive yaw behaviour of truck or trailer posing major difficulties for the driver, and likely to occur at lateral accelerations far below the static tilting boundary. This paper first treats yaw-stability for a single heavy vehicle in a fundamental way. The analysis will be based on the full non-linear vehicle behaviour where critical (stationary) points are discussed within a phase plane representation. Local behaviour of trajectories around these points will be analysed yielding the type of (in-)stability, for all possible combinations of effective tyre behaviour (incorporating suspension characteristics). These effects will also be presented in terms of the handling-diagram representation, showing the lateral acceleration under stationary conditions in terms of steering angle and road curvature. The shape of this diagram can be interpreted in terms of steering sensitivity of the vehicle. The results will be extended to tractor-trailer combinations, where the previous results applied to each of the articulations together lead to an understanding of stability of the full vehicle combination. The different types of excessive yaw modes (jack-knifing, trailer swing) of the combination will be discussed as related to the steering characteristics of the separate parts, and with reference to various vehicle parameters.

Excessive behaviour of vehicles is often the subject of study, motivated by either the development of active safety systems uch as ESP, or the improvement of vehicle performance such as for racecars. In all of these cases, combined slip needs to be taken into account. In many cases however, the full set of tyre characteristics is not available. Consequently, one needs to work with inaccurate combined slip properties based on estimated slip stifnesses and friction levels. It would be a great advantage if combined slip characteristics could be estimated accurately, especially for truck tyres and racecar tyres, where facilities are rare and testing is very expensive. For passenger cars and light van tyres, about 60% of the testing effort is spent in combined slip. This means time and costs which could be saved by this accurate estimation. Moreover, apart from this reduction of the testing effort, the estimation could be a tool for assessment in testing tyres in combined slip leading to better quality tests results. Anyhow, it will permit to derive combined slip characteristics when no test-data are available. First, some fundamental aspects in tyre modelling are given with the MF-Tyre Model (Magic Formula) treated in detail. Combined slip as described by the MF-Tyre model is discussed with the characteristics derived and compared with different passenger car tyres. In parallel, combined slip is also studied from a more fundamental scope using the physical Brush Model, with special focus on the ratio between tyre forces under pure slip and combined slip conditions (the weighting functions). Various methods to derive these weighting functions based on pure slip characteristics without testing are treated. Among these, two methods lead to satisfactory results, the Slip Circle Sinusoidal Method (SCS) presented by Pottinger and especially the Practical Slip Similarity Method (PSS), derived and developed by the authors. Among others, these methods will be compared with the Magic Formula fits and the experimental results with observed deviations for the PSS-method in shear force with measurement results bounded by 5% for large tyre load and less than 8% for low tyre load. A comparision of the SCS-method and PSS-method with the MF-fits for large slip suggests improvements of the Magic Formula tyre model, Between the various estimations for the prediction of the combined slip based on pure slip characteristics, the Slip Circle Method and the Practical Slip Similarity Method, derived and developed by the authors will lead to a satisfactory prediction with respect to measurement data. In addition, estimated combined slip outside of the measurement range is discussed.

The major advantage of a motorcycle with respect to a passenger car is the possibility of the driver to tilt during cornering and thereby maintaining stability whereas a passenger car will suffer from the risk of capsizing at high speed. This observation has motivated recently various manufacturers to develop new concepts of narrow vehicles that are able to tilt like a motorcycle but offer the comfort of a passenger car, allowing further downsizing of vehicles enabling higher fuel efficiency. As a result, there seems to arise a whole new class of vehicles, which cannot be compared, to either passenger cars or motorcycles, with typical examples such as the Ford Gyron and the GM Lean Machine. More recent examples are the Daimler Benz Life Jet and the Carver of Brink Dynamics. This paper includes a mathematical treatment of the dynamic behaviour of such vehicles, denoted here as a Narrow Tilting Vehicle (NTV). The analysis is based on a vehicle concept consisting of three main rigid bodies, a front assembly (front fork), a mid-assembly (passenger cabin) and a two-wheeled rear-assembly (engine, rear part of chassis including rear suspension, wheels, etc.). Important criteria for the designer are a stable behaviour and, on the other hand, a smooth, responsive cornering performance. As it turns out, various eigenmodes related to yaw, steering and roll behaviour of the vehicle are working against each other in this respect. Obviously, many vehicle design parameters play an important role where which have a major impact on the vehicle behaviour. One might distinguish the overall dimensions, mass distribution, front-fork geometry, tyre characteristics, suspension layout, the tilting controller design, etc. Due to the large variety in parameter-combinations, sensitivity regarding one single parameter always depends on the selected reference case for the remaining parameters, and therefore cannot be extrapolated easily to reach its optimal value. In the paper, the design parameters having a major impact on the vehicle performance are identified. The impact of parameter modifications on the vehicle stability and handling performance is discussed on the basis of mathematical analysis, and interpreted in physical terms (supported by numerical analysis and experimental results). That means that, finally, tendencies in changes in vehicle performance can be and resulting in general guidelines for the design of this new class of vehicles the model equations - - - - - the tilting mechanism - - - - - stability behaviour - - - - - smooth cornering of the NTV

The major advantage of a motorcycle with respect to a passenger car is the possibility of the driver to tilt during cornering and thereby maintaining stability whereas a passenger car will suffer from the risk of capsizing at high speed. This observation has lead Brink Dynamics to create and develop a new concept of a man-wide vehicle that is able to tilt like a motorcycle but which offers the comfort of a passenger car, allowing further downsizing of vehicle enabling higher fuel efficiency. This resulted into a three-wheeled passenger car referred to as the MWV, with two seats in a row consisting of two bodies, a two-wheeled rear-assembly and a front assembly being the passenger compartment including the front-fork assembly, that tilts with respect to the rear assembly. Tilting is controlled by the driver through a steering bar. This paper includes a mathematical treatment of the behaviour of the MWV. The tilting mechanicsm is discussed and included in the model. The sensitivity of some further design characteristics will be discussed. In particular the MWV will be compared with a motor-cycle and a passenger car. Finally the dynamic performance of the vehicle will be examined based on the full dynamic equations for the MWV. within this paper, this analysis will be restricted to step-steer where the dynamic vehicle behaviour will be discussed with reference to its steady state performance.

Testing of steady state tire handling performance is nowadays common practice with slip angle sweeps and breaking being simulated in the laboratory with drum or flat belt, or on the road with a test trailer. In recent years, more emphasis is put on dynamic tire models, motivated by ride comfort analysis, durability analysis, the performance of active control devices and alike. Such models require new test procedures and test facilities. For this purpose, four different test facilities have been derived at the Delft University of Technology. The paper discusses these dynamic test benches as well as the test procedures being designed for them, with reference to model validation and paramter-assessment.

For a long time, vehicle technology has been a stimulating and flourishing activity at TNO and the Delft University of Technology. The tire is a key element, and its research into this, that has given both organisations their strong international profile

There is no doubt that tyres have a strong impact on vehicle behaviour and on the driver assessment of vehicle performance. This relates to handling, perceived safety and controllability, the amount of effect required to react, course following and straight line stability, etc. Several of these aspects are known to correlate to some extent with objective indicators such as gains, response times and alike, as obtained from open loop reference tests. But there is more, particularly in relation to the interface between steering system and driver control and perceived feed-back, where these phenomena are still not well understood. In fact, this was one of the motivations for the seminar 'Understanding human monitoring and assessment'. In the paper, several studies from the past are discussed focusing on the influence of the tyre design parameters on the driver assessment, where both open-loop and closed-loop results are considered. This results in an overview of the discriminating physical tyre parameters examined, the experimental approaches applied, and the outputparameters (subjective and objective identifiers) describing the vehicle behaviour.

The sensitivity of vehicle handling to combined slip tyre characteristics is investigated using two simulation models with different interaction between lateral and longitudinal tyre forces. The standard method for the braking in a turn test is simulated with both models, and differences in the outcome are related to tyre characteristics. The results indicate that an accurate description of the so-called combined slip (i.e. brake slip with side slip) situation in the contact region of the tyre is important. Furthermore, the suspension configuration of a vehicle determines to a large extent the outcome of the braking in a turn test. Accurate modelling of the suspension is necessary to obtain a good description of braking in a turn by simulation. Scaling factors of the tyre model (MF-Tyre) are used for easy modification of tyre characteristics. However, modification of tyre characteristics must be done with care and graphical feedback of resulting tyre characteristics is proven to be important.

This paper will discuss the DELFT-TYRE productline from the point of view of the engineer to optimize operationai cha¡acteristics of the tyre-vehicle system. Several examples are treated to illustrate the added value of sophisticated tyre modelling under combined slip conditions (braking in a turn) and the use of scaling factors in the underlying tyre model to analyze the effect of tyre-road friction on vehicie lane change behaviour.

This paper describes a Road Weather Warning System in use in Finland which employs variable message signs (VMS). The warning system is first described, followed by a discussion of the hypotheses and indicators, the experimental design, data collection, results of a roadside survey, effect of speed and headway, and possible future actions.