Tuesday, September 28, 2004
Jim Hey, Ricardo
AWD System Selection Techniques
A rigorous process is described for the selection of AWD devices with specific illustration examples and case studies which address the following cascade:
- System Selection
- Attribute Definition for Vehicle Sector including requirements and relative weightings
- Modelling and Control for Traction and Yaw Dynamics using Simulink, IPG, ADAMS and ASCET-SD s/w tools.
- Multi-parameter Performance Assessment including Safety and Driver Workload Metrics
- Derivation of driveline loads and sizing by measurement and prediction of Duty Cycle
- Comparison with alternative active and passive Driveline and Chassis technologies and combinations
- Practical aspects of reaching a near "Production Intent" demonstrator are then reviewed:
- Application of previous "lessons learnt"
- Economic Prototyping
- Vehicle Installation
- Integration with Electrical system using CAN "cracking" tools to overcome multi-supplier integration issues.
- An experience-based insight relating to particular Emerging Technologies is then presented:
- Magneto-rheological variable coupling: pros, cons and novel improved designs
- Ricardo Demonstrator Program featuring "torque vectoring" using electrical actuation.
- Finally, a summary of the AWD market is then presented with a technology road map for saleable technology to 2015 with low incremental CO2.
Metin Esray, ZF
Switchable Stabilizer Bar Systems to Modify Safety, Comfort and Traction
The stabilizer fulfills an important task in the vehicle: It stabilizes the vehicle body during cornering by reducing its roll angle. On the one hand this increases the driving safety, but on the other hand, it affects the ride comfort during straightline driving. In case of unilateral irregularities only one single wheel vibrates at one axle. These single wheel movements are transmitted to the other wheel by the stabilizer and the stabilizer connection. The copying movement thus arising leads to unpleasant head accelerations of the passengers (head toss). This conflict is eliminated by means of a switchable stabilizer which is automatically coupled during cornering at a specified vehicle speed and decoupled during straight-line driving or at off-road low speeds. This presentation describes solutions for switchable stabilizers for passenger cars, off-road and sport utility vehicles (SUVs) or vans which increase the driving safety, ride comfort and off-road traction. Further advanced developments mentioned, which allows a continuous change of stabilizer bar stiffness.
Paolo Sacchettini, Toyoda-Koki Automotive, Torsen North America, Inc.
The New All Wheel Drive Torsen R differentials
The newly developed torque-splitting & torque-sensing differentials are widening both the range of vehicle dynamic behavior characterisation in terms of FWD or RWD orientation and the range of application possibilities to various types of transmissions. The packaging friendliness, torque capacity, and compactness are collateral attributes for making this new generation of torque-sensing differentials a particularly attractive alternative. Their various functional aspects will be described in theory, with particular focus on the effects induced to the vehicle's dynamic behavior, and will be illustrated by instrumented vehicle measured data."
Walter Sackl, MagnaSteyr
AWD Coupling System for the Rear Axle
In the great market of all wheel driven cars several AWD-solutions with different arrangements are available. This paper will show the direction of philosophy of the Active Torque Control Unit to obtain best driving performance and low weight of driveline components specially for cars with transversal mounted front engine layout. The systematics of relevant driving situations and the effect of comfort and road load date is shown to determined the layout of this new all wheel drive coupling system.
Anthony Pratt, J.D. Power
The Future market of All Wheel Drive
The content of the presentation will include:
- The current and future all wheel drive market with a forecast going out through 2011.
- Highlight market trends, which include vehicle segment penetration and consumer insight.
- The focus will be global, with an emphasis on the US market.
Vladimir V. Vantesevich, Lawrence Technological University
AWD Systems as a Tool for the Vehicle Performance Optimization
To control the components of the power balance equation of a vehicle in motion leads to control the vehicle performance that includes vehicle traction and acceleration/velocity properties and energy/fuel efficiency, ride stability and turnability, smoothness of ride, others. The presentation mathematically links vehicle performance criteria with power distribution to the drive wheels that is dependent on driveline systems characteristics. Hence, the developed foundations are the basis for designing any types of AWD systems, e.g. mechanical systems, mechatronics, hybrid systems, others.
Sam Ellis, Ford Werke A.G.
A comparison of the Dynamic Performance of Electronically-Controlled All Wheel Drive Systems
This study aims to provide an objective comparison of the effects on vehicle handling achieved by different electronically controlled All Wheel Drive (AWD) systems in a performance sports vehicle. These preliminary simulations do not take the dynamics of the actuators into account.
Using a full vehicle model of a current production Ford Focus scaled to boost engine output to 300PS /400Nm, dynamic manoeuvres were simulated using Vedyna. The model was modified to allow the comparison of the following drivetrain layouts:
- FWD with Limited Slip Differential
- Permanent (Full-Time) AWD with active centre and rear differential locks
- Hang-On (automatically engaging) AWD with a coupling in-line with the propellor shaft
- Hang-On (automatically engaging) AWD with a Torque Vectoring Differential (TVD)
The maneuvers were chosen to reflect driving situations in which understeer often occurs. The situations investigated in this report are: Throttle on in a curve; Handling track; Junction exit.
The results show that Active AWD provides better acceleration and generates greater yaw rates compared to FWD. Permanent AWD provides the best acceleration exiting corners while Torque Vectoring across the rear axle gives best handling and reduces driver steering effort.
John Peterson, BorgWarner
Pole Placement Design Strategy for Torque-Proportioning Vehicle Dynamics
Not available at the time of printing
Wednesday, September 29, 2004
Randal Golda, Kuzunobu Takeshita, GKN Driveline
Improved Mobility by Electronically Controlled Differentials
Improved Mobility by Electronically Controlled Differentials - Today's automotive applications of brake based traction control and dynamic stability control continue to penetrate the market as an approach to enhance vehicle traction and stability. However, there is also a growing trend in the use of electronically controlled couplings and differentials. This presentation will highlight a new electronically controlled axle differential technology, which has just launched in the market, including working principle, capabilities and operational strategies.
John Park, Dana Corporation
Benefits of Active Differential System on Handling and Mobility
Most of the passive limited-slip differential systems compromise the handling and mobility. Mobility requires aggressive limited slip action, while the handling needs a conservative intervention. Active differentials allow the vehicle to satisfy the two performance criteria. Therefore, an active differential should be teamed up with a versatile control strategy so that the system can properly function in various road conditions and maneuver scenarios. This presentation presents the modeling, control and simulation of a vehicle equipped with an active differential system.
Russell Osborn, Jaguar/Land Rover
Independent Control of All-Wheel Drive Torque Distribution
The sophistication of all wheel drive technology is approaching the point where the drive torque to each wheel can be independently controlled. This potentially offers vehicle handling enhancements similar to those provided by Dynamic Stability Control, but without the inevitable reduction in vehicle acceleration. Independent control of all wheel drive torque distribution would therefore be especially beneficial under acceleration close to the limit of stability.
A vehicle model of a typical sports sedan was developed in Simulink, with fully independent control of torque distribution. Box Behnken experimental design was employed to determine which torque distribution parameters have the greatest impact on the vehicle course and acceleration. A proportional integral control strategy was implemented, applying yaw rate feedback to vary the front rear torque distribution, and lateral acceleration feedback to adjust the left right distribution.
The resulting system shows a significant improvement over conventional driveline configurations under aggressive cornering acceleration on a high surface. The performance approaches the theoretical limit for these conditions. In the medium term such a system is only likely to be economically viable for premium vehicles. However, a future revolution of powertrain technology towards, for example, wheel mounted motors, could realize these handling benefits far more widely.
Michael Hoeck and Michael Auweiler, Getrag Driveline Systems GmbH
Modular Driveline Tested in its Active Yaw Mode
The control of driveline torque can be used to influence the vehicle dynamics behavior. To investigate the effects of an electronically controlled "AWD system" on vehicle dynamics a demonstrator vehicle was build up and instrumented. The paper will present the novel driveline design as well as the results of objective vehicle test maneuvers with the torque vectoring configuration. The test results will demonstrate the potential of a torque vectoring system compared to the same vehicle with a standard FWD driveline.
Per-Olof Davisson, Haldex Traction Corp.
Awd System with Combined Mechanical and Electronic Intelligence for Enhanced Safety On-Road.
The trend away from mechanical AWD systems in favour of electronically controlled AWD systems has given the OEMs the possibility to control the torque distribution in order to influence vehicle behaviour.
The increased availability of sensor and vehicle information on the communication bus system has significantly improved the possibility of advanced vehicle control by the AWD system. The dependency of in-signal quality and system bandwidth will, however, constitute a restriction when choosing control strategy.
There are some major advantages with a mechanical control circuit in the AWD system that stand out when safety on-road in combination with fuel economy and drivetrain load spectra is of importance:
- Self regulating beyond controller bandwidth
- Less dependency on in-signal quality
- Fail-safe mode with sustained AWD characteristics
An evaluation of common electronically controlled torque control system in comparison with a combined torque control and stiffness controlled system using typical drive situations show benefits in favour of a combined system.
One important criteria in evaluating the performance of all-wheel-drive systems is the vehicle dynamics influence in different driving situations. Sudden ice-patches on a dry road can startle the speediest electronics whereas a mechanical control circuit can cope with ease. To overcome this draw-back, torque controlling systems often uses control strategies resulting in a high portion of drive torque being transferred to the secondary axle. This strategy means in many cases increased fuel consumption and drivetrain stress.
Koji Matsuno, Subaru
Vehicle Dynamics Enhancement of AWD Vehicle and Future Prospects
This presentation introduces application examples of yaw control technologies for all wheel drive vehicle by fore/aft torque distribution control and limited slip differential function utilizing several sensors. The enhancement of vehicle stability and handling performance by the all wheel drive control was verified not only on snow-covered road but also on dry asphalt. The presentation also covers front and rear LSD optimal design and future direction of the above mentioned technologies.
Damian Harty, ProDrive
Guidelines and Principles for Driveline-based Stability Systems
Prodrive's extensive experience with prototype driveline-based stability systems is distilled into some clear lessons for designers, selecters and suppliers of such systems. With driveline systems, the emphasis is on continuous control as against the "triggered recovery" behavior of brake-based systems. The interaction between driveline-based systems and brake-based systems is discussed in terms of guiding principles and useful interactions. Road Edge Recovery behavior is specifically considered. The opportunities for driveline-based systems to influence vehicle character are outlined and the resulting requirements placed on driveline hardware are identified.