Suspension Geometry Research Articles

Car attitude control by series mechatronic suspension

This paper investigates the potential of the Series Active Variable Geometry Suspension (SAVGS) to control chassis roll and pitch motions during cornering and combined cornering and braking events. A cascaded control scheme that drives the four actuators (one per wheel) independently and respects all physical and design limitations is presented. The control system is thereafter applied to a specific SAVGS configuration and tested through nonlinear simulation of a full vehicle model of a generic high performance sports car. A wide set of simulation results corresponding to standard open loop maneuvers is shown, providing insight on the performance of the SAVGS, its requirements, operation, and influence on the directional response of the vehicle. These results suggest that the SAVGS is well suited to controlling chassis attitude motions in this class of vehicles.

이중너클을 이용한 후륜 토 및 캠버각 변화를 통한 조종안정성 개선

In this study, suspension geometry is controlled to improve vehicle handling performance. The toe and camber of the rear suspension is controlled independently by using a double knuckle structure designed to enhance the vehicle cornering stability. Camber and toe changes in the rear wheel during high speed turning maneuver are important factors that influence the vehicle stability. Toe in the rear outer wheel plays a dominant role in cornering. A control algorithm for the camber and the toe angle input is developed to carry out the control simulation of the vehicle such as single lane change, the steady state cornering, the double lane change and the step steering simulation. Effects of the camber and toe angle control are analyzed from the computer simulations. A double lane change simulation revealed that the suspension mechanism with variable camber angle and variable toe angle decreases the peak body slip angle and peak yaw rate, 50% and 10%, respectively.

An Analysis of the Relationship Between Suspension Geometry and Ride Characteristics

An Analysis of the Relationship Between Suspension Geometry and Ride Characteristics

Shear-induced sedimentation in yield stress fluids

Stability of coarse particles against gravity is an important issue in dense suspensions (fresh concrete, foodstuff, etc.). On the one hand, it is known that they are stable at rest when the interstitial paste has a high enough yield stress; on the other hand, it is not yet possible to predict if a given material will remain homogeneous during a flow. Using MRI techniques, we study the time evolution of the particle volume fraction during the flows in a Couette geometry of model density-mismatched suspensions of noncolloidal particles in yield stress fluids. We observe that shear induces sedimentation of the particles in all systems, which are stable at rest. The sedimentation velocity is observed to increase with increasing shear rate and particle diameter, and to decrease with increasing yield stress of the interstitial fluid. At low shear rate (’plastic regime’), we show that this phenomenon can be modelled by considering that the interstitial fluid behaves like a viscous fluid–of viscosity equal to the apparent viscosity of the sheared fluid–in the direction orthogonal to shear. The behavior at higher shear rates, when viscous effects start to be important, is also discussed. We finally study the dependence of the sedimentation velocity on the particle volume fraction, and show that its modelling requires estimating the local shear rate in the interstitial fluid.

Effects of camber angle control of front suspension on vehicle dynamic behaviors

This paper proposes a new electronic camber suspension mechanism in which the suspension geometry rather than brake and driving torques is controlled to improve the cornering performance. The new camber angle mechanism is made available in a double wishbone type suspension. The bicycle model is employed to establish the control strategy for the camber angle mechanism. The referenced yaw rate is derived to make the control input. To carry out the control simulation of the full car, ADAMS/Car and MATLAB/Simulink are used. The result of fishhook simulation indicates that the proposed mechanism reduces the camber angle generation and decreases the camber thrust. This makes the vehicle move straight forward easily. The single lane change simulation indicates that the change of camber angle is small and it contributes to the short cornering and fast straight forward ability.

Challenges and Possibilities in Variable Geometry Suspension Systems

The variable-geometry suspension system is in the focus of the paper. The advantages of the variable-geometry system are the simple structure, low energy consumption and low cost. During maneuvers the variable-geometry system modifies the camber angle of the front wheels in order to improve road stability. The system affects both the chassis roll angle and the half-track change. Moreover, the tracking error of the reference yaw rate can also be reduced. In the paper the challenges and possibilities of the variable geometry suspension system are analyzed.

Identification of Tire Model Parameters Through Full Vehicle Experimental Tests

Individual tire model parameters are traditionally derived from expensive component indoor laboratory tests as a result of an identification procedure minimizing the error with respect to force and slip measurements. These parameters are then transferred to vehicle models used at a design stage to simulate the vehicle handling behavior. A methodology aimed at identifying the Magic Formula-Tyre (MF-Tyre) model coefficients of each individual tire for pure cornering conditions based only on the measurements carried out on board vehicle (vehicle sideslip angle, yaw rate, lateral acceleration, speed and steer angle) during standard handling maneuvers (step-steers) is instead presented in this paper. The resulting tire model thus includes vertical load dependency and implicitly compensates for suspension geometry and compliance (i.e., scaling factors are included into the identified MF coefficients). The global number of tests (indoor and outdoor) needed for characterizing a tire for handling simulation purposes can thus be reduced. The proposed methodology is made in three subsequent steps. During the first phase, the average MF coefficients of the tires of an axle and the relaxation lengths are identified through an extended Kalman filter. Then the vertical loads and the slip angles at each tire are estimated. The results of these two steps are used as inputs to the last phase, where, the MF-Tyre model coefficients for each individual tire are identified through a constrained minimization approach. Results of the identification procedure have been compared with experimental data collected on a sport vehicle equipped with different tires for the front and the rear axles and instrumented with dynamometric hubs for tire contact forces measurement. Thus, a direct matching between the measured and the estimated contact forces could be performed, showing a successful tire model identification. As a further verification of the obtained results, the identified tire model has also been compared with laboratory tests on the same tire. A good agreement has been observed for the rear tire where suspension compliance is negligible, while front tire data are comparable only after including a suspension compliance compensation term into the identification procedure.

Design and analysis of an intelligent controller for active geometry suspension systems

An active geometry suspension (AGS) system is a device to optimise suspension-related factors such as toe angle and roll centre height by controlling vehicle's suspension geometry. The suspension geometry could be changed through control of suspension mounting point's position. In this paper, analysis and control of an AGS system is addressed. First, the effects of suspension geometry change on roll centre height and toe angle are studied. Then, based on an analytical approach, the improvement of the vehicle's stability and handling due to the control of suspension geometry is investigated. In the next section, an eight-degree-of-freedom handling model of a sport utility vehicle equipped with an AGS system is introduced. Finally, a self-tuning proportional–integral controller has been designed, using the fuzzy control theory, to control the actuator that changes the geometry of the suspension system. The simulation results show that an AGS system can improve the handling and stability of the vehicle.

Static and dynamic wheel alignment analysis of steering drift under straight braking

This paper aims to identify the steering drift of a small passenger vehicle under severe straight braking. Steering drift is analysed by gyro and wheel tracker measurements of dynamic wheel alignments, and when compliance is done by Kinematic and Compliance (KC subsequently, the toe angle becomes toe-out owing to the wheel bump stroke. To investigate the contribution of suspension parameters that may be difficult to control in field tests, bushing stiffness of the lower control arm, kingpin offset at the ground, caster angle, bump toe angle and wheel weight are simulated in a multi-body software environment. The results show that the dominant factors are the bump toe, caster and the wheel weight difference between the left and right wheels. This approach is useful in setting proper suspension geometry at the stage of conceptual chassis design.

Design of Automotive Metal and Composite Chassis Structures

This paper reviews recent patents covering automotive metal and composite chassis structures. Automotive chassis are very complex structures and the variety of different types is vast. This paper attempts to reveal modern chassis design looking at composite structures, bonding methods, front sub-frames, complete space-frames, uni-body, integral frame and monocoque structures. Automotive chassis designs have had considerable developments in recent years. This is attributed to recent legislation taking particular interest in after service disposal and more prominently crash, impact and occupant safety. Automotive manufacturers continue to develop new, innovative and novel approaches to achieving rigidity and stiffness in torsion and bending to achieve optimal suspension geometry, safety and occupant comfort. Recent patents in automotive chassis design refer mainly to stiffening support structures, composite structures, retractable roofs and by far the most common, front crash sub frames. Keywords: Chassis, metal chassis, composite chassis, bonded chassis, crash box, sub frames, spaceframe, monocoque, heat affected zone, epoxy resins, Cycom 977, honeycomb sandwich material, resin transfer moulding, RTM, Cabriolet space-frame, CNC bending, computer controlled welding, fibre-reinforced plastic sheets, multi utility vehicle, Audi spaceframe (ASF) chassis, resilient aluminium alloy, frontal collision, FRP COMPOSITES, torsion beam, Rear sub-frame, Shock absorbing crash element, Honeycomb core profile, noise and vehicle harshness

Identifying tyre models directly from vehicle test data using an extended Kalman filter

Individual tyre models are traditionally derived from component tests, with their parameters matched to force and slip measurements. They are imported into vehicle models which should, but do not always properly provide suspension geometry interaction. Recent advances in Global Positioning System (GPS)/inertia vehicle instrumentation now make full state measurement viable in test vehicles, so tyre slip behaviour is directly measurable. This paper uses an extended Kalman filter for system identification, to derive individual load-dependent tyre models directly from these test vehicle state measurements. The resulting model therefore implicitly compensates for suspension geometry and compliance. The paper looks at two variants of the tyre model, and also considers real-time adaptation of the model to road surface friction variations. Test vehicle results are used exclusively, and the results show successful tyre model identification, improved vehicle model state prediction – particularly in lateral velocity reproduction – and an effective real-time solution for road friction estimation.

Steering pull and drift considering road wheel alignment tolerance during high-speed driving

This paper describes an analytical vehicle model and a full-vehicle model that consider the effect of suspension geometry on steering pull and drift. Steering pull occurs when a driver applies steering wheel torque to keep a straight-line course, and steering drift means the tendency to deviate from the intended path with a free steering wheel. In designing a chassis system, it is crucial to establish a suspension insensitive to steering pull and drift regardless of manufacturing tolerances. Simulation results show that larger caster trail at the front wheel leads a less-sensitive vehicle towards steering pull and drift, since caster trail reduces the equilibrium slip angle difference between pull and drift by considerably changing the aligning moment diagram. These wheel alignment sensitivities are validated by experimental measurement of drift distance.

차량 쏠림 개선을 위한 전륜 현가시스템의 기하공차 최적화

This study is focused on simulation-based dimensional tolerance optimization process (DTOP) to minimize vehicle pulls by reduction of dimensional variation in front suspension system. In previous studies, the effect of tires and wheel alignment sensitivity have mainly been investigated to eliminate vehicle pulls in nominal design condition without allocating optimal tolerance level for selected components, among various factors regarding vehicle pulls such as vehicle design parameters, vehicle weight balance, tires, and environmental factors. Unfortunately, there are wide variations in the real vehicle, and these have impacted actual vehicle pulls, especially wheel alignment effects from suspension geometry variation has not been considered in the previous studies. In the tolerance design of suspension, tolerance variables with the uncertainty such as parts dimensional variation, assembly process, datum position and direction, and assembly tool tolerance has a great influence on the variation of the suspension dimensional performances. This study introduces total vehicle pull prediction model in considering major key factors for vehicle pull sensitivity. The Monte Carlo-based tolerance analysis model using Taguchi robust method is developed to optimize dimensional tolerance parameters, satisfying on the target variation level.

Vehicle steering returnability with maximum steering wheel angle at low speeds

In this paper, an analytical model with suitable vehicle parameters, together with a multi-body model is proposed to predict steering returnability in low-speed cornering with what is expected to be adequate precision as the steering wheel moves from lock to lock. This model shows how the steering response can be interpreted in terms of vertical force, lateral force with aligning moment, and longitudinal force. The simulation results show that vertical steering rack forces increase in the restoring direction according to steering rack displacement for both the inner and outer wheels. As lateral forces due to side-slip angle are directed toward the medial plane of the vehicle in both wheels, the outer wheel pushes the steering wheel in the returning direction while the inner wheel does not. In order to improve steering returnability, it is possible to increase the total steering rack force in both road wheels through adjustments to the kingpin axis and steering angle. This approach is useful for setting up a proper suspension geometry during conceptual chassis design.

A proposition for new vehicle dynamic performance index

Current vehicle dynamic performance indices seem to be insufficient to represent the fundamental of vehicle dynamic performance because they are easily influenced by tuning elements such as springs. In this paper, suspension geometry is discussed as the basis of vehicle ride and handling performance. To analyze the characteristics of the suspension geometry, the screw theory is introduced. The screw axes surface, which is generated by continuous vehicle body motion, is the pure geometric property of the suspensions, and the shape of the surface is not influenced by tuning elements. Therefore, the shape of the screw axes surface can be regarded as the “genome” of vehicle performance. The gradients of screw parameters with respect to body lateral acceleration are proposed for new vehicle dynamic performance, and their correlation to vehicle performance is validated by full vehicle dynamic analysis.

The Nonlinear History of Fibre Flow Research. Part 2: Continuation, Reflections and Suggestions

Abstract Technical fibre flows are normally flocky but have theoretically mainly been treated as individual fibre flows. The reason for this can only be understood through the subject’s historic development. In Part 1 of this investigation the origin of fibre flow research was traced to the beginning of the 19th century, and was followed through its formative years at the first half of the 20th century up to about WWII. This second and final part takes us up to about the 1960s when the present main theoretical research tradition had been firmly established. An example of an alternative approach is given. Finally, some suggestions for future work are advanced. In Appendix methods of characterising the inner geometry of technical fibre suspensions are discussed

Active geometry control suspension system for the enhancement of vehicle stability

The active control of suspension geometry has historically been a challenging perspective for chassis teams of worldwide automakers. Manufacturers and suppliers have offered different solutions, but few have succeeded in combining a marked improvement in handling performance, low-energy consumption, simplicity, and low cost. The new and revolutionary approach of an active geometry control suspension (AGCS) reinvents the possibilities of rear-suspension active toe control. This system employs the use of the complexity of a rear multi-link suspension, and a clever design layout to minimize the energy use. Additionally, because of an efficient control logic strategy, the vehicle-handling performance and stability are substantially improved. The system is the most successful in controlling vehicle transient situations initiated mainly by aggressive lane-change manoeuvres at medium to high speeds. This paper presents the most relevant actions of the development process of the AGCS. The use of different evaluation methods and accurate measurement equipment was crucial for optimization of the system. The methods presented combine subjective evaluations in different road conditions (icy, wet, and dry asphalt), suspension kinematics and elastokinematics characterization, and objective road measurements using dynamic wheel position measurement equipment. Finally, a comprehensive summary of the handling-test results are explained, which outline the efficiency of the system, and its influence on the active safety level of the vehicle.

A method for predicting dynamic behaviour characteristics of a vehicle using the screw theory — part 1

This paper presents the development of a prediction method for vehicle dynamic behaviour characteristics using screw axis theory. A vehicle model is developed for quasi-static analysis which is applied to vehicles of three different suspension configurations under cornering conditions in which a specific lateral force acts. A finite screw axis is determined using quasi-static analysis based on a rigid body displacement of the vehicle model with respect to the ground. The fixed screw axis surface formed by the migration of the finite screw axis is also determined. The shape of the fixed screw surface shows that the fundamental characteristics of vehicle roll behaviour is determined not by suspension tuning element but by suspension geometry. The gradients of screw parameters with respect to lateral force when the vehicle model behaves in an initial cornering state are proposed as prediction parameters of vehicle dynamic motion. The dynamic analysis result shows that vehicle dynamic motion characteristics can be successfully predicted by the proposed parameters.

2404 機構解析ソフトウェアを用いた競技車輌用サスペンションジオメトリの設計

2404 機構解析ソフトウェアを用いた競技車輌用サスペンションジオメトリの設計

0226 車両運動特性に与えるサスペンションジオメトリの影響(J17-2 交通機械のダイナミクス(2),J17 交通機械のダイナミクス)

0226 車両運動特性に与えるサスペンションジオメトリの影響(J17-2 交通機械のダイナミクス(2),J17 交通機械のダイナミクス)