Steering without limits

| Transport

OmniSteer removes limits on steering

Andy Pye looks at the highly-integrated lateral and transverse guidance systems being developed as part of the OmniSteer project to improve manoeuvrability.

The ability to manoeuvre automobiles is pushed to the limit by cramped inner city conditions. Those who need to park their vehicles frequently, such as delivery services and mobile care providers, lose a lot of working time searching for and then getting into parking spaces. New chassis types with wheels that can be steered individually and electric drives make it possible to increase manoeuvrability and therefore efficiency, particularly in flowing urban traffic. The OmniSteer project, expected to last three years, is funded by Germany’s Federal Ministry of Education and Research, and is aimed at researching suitable concepts and prototypes by 2018 and has a budget of €3.4 million.

The “Omni” prefix is an acronym for Orthogonal (manoeuvring at a right angle to the original direction of travel), Multi-directional (different travel paths are possible), and Non-linear (the position of the steering wheel is decoupled from the steering angle). The project partners are Schaeffler, Paravan and Hella, as well as researchers from the KIT and its Information Technology Research Centre.

“The increasing electrification and automation of vehicles makes it possible to offer users innovative driving functions,” explain project managers Marcel Mayer from Schaeffler and Michael Frey from the Institute of Vehicle Systems Engineering at the Karlsruhe Institute of Technology (KIT). “The added value offered by electric drives compared to internal combustion engines is significant, because we can directly integrate electric drives into each wheel.”

Together with innovative wheel suspension types that allow a wider range of steering motion on the front and rear axle, suitable distance and lane guidance systems (highly-integrated lateral and transverse guidance systems) are also being developed that will significantly increase manoeuvrability.

“It is possible to switch seamlessly between front-wheel, rear-wheel and all-wheel steering, depending on the situation,” says Mayer, who is in charge of Schaeffler’s Automated Driving work group and is carrying out research at the KIT as part of the SHARE (Schaeffler Hub for Automotive Research in E-Mobility) research collaboration.

Driving manoeuvres in restricted spaces – such as turning corners and changing lanes in a traffic jam or when approaching road works – will become more efficient with OmniSteer in terms of both time and energy, and this will improve the way in which lanes are utilised. Delivery services will also enjoy an enormous benefit, since it will even be possible to continuously pull into parking spaces at a right angle to the direction of the traffic, which in turn will make it possible for even the smallest parking spaces to be used and more rapidly allow traffic to continue moving.

“These driving functions therefore directly increase safety, comfort and energy efficiency, as well as also improving the utilisation of space and the flow of traffic in cities in the long term,” says Frey.

As part of the OmniSteer project, a scaled-down demonstration vehicle with a lateral and transverse guidance system capable of performing orthogonal, multi-directional, and non-linear driving and steering manoeuvres is being developed. These three features allow innovative driving functions and thus make it possible to utilise the full potential of automation in electrically-driven vehicles. The vehicle will use sensors to identify its surroundings, calculate the best possible path of travel and then independently perform the necessary complex manoeuvres. A specially-developed display and operating unit will allow the driver to select and keep track of the driving functions and to intervene if necessary. The FZI Research Centre for Information Technology is contributing manoeuvre and trajectory planning processes to the project, which select the best possible chassis configuration, based on the situation.

Volume production of electromechanical camshaft phasing unit

The use of electromechanical phasing units rather than the current standard hydraulic systems allows a camshaft to adjust more quickly and accurately to prevailing engine operating conditions. This reduces fuel consumption and harmful emissions, while simultaneously increasing driver comfort during stop/start operations.

The last few years have seen a boom in camshaft phasing systems, which control timing of the opening and closing of engine valves. This enables optimum phasing of the cylinder intake/exhaust cycle, with engine speed and torque demands. Previously used only in high performance engines, variable opening and closing of inlet valves is now standard technology in modern petrol engines. Camshaft phasing systems are now also being used more frequently on the outlet side too, including some of the latest diesel engines. Until now, almost all camshaft phasing units have used hydraulic systems.

Electromechanics makes it possible to phase the camshaft at speeds up to 600 crank angle degrees per second. Hydraulic systems operate between a half and a tenth as fast, irrespective of the engine speed and temperature. The increased dynamics of electromechanical phasing units enable very fast reaction times to changes in load, even at low engine speeds, including when the driver suddenly pushes down on the accelerator pedal while the engine is overrunning. Unlike hydraulic systems, the reaction speed to a change in load is not dependent on the oil supply. In some cases, it is no longer necessary to have a larger engine oil pump, which results in reduced fuel consumption.

Also, starting and stopping the engine is much smoother with electromechanical camshaft phasing units. This is important not only for stop/start operations but also for hybrid vehicles. It is possible to start an internal combustion engine without any noticeable ‘judder’ because, up to 200rpm, the engine runs with reduced compression because the camshaft can be positioned as required before the engine starts. During acceleration, valve control times are synchronised with fuel injection so that a soft onset of compression occurs; when compression and ignition are correctly adjusted, the result is smooth engine start up.

Now, Schaeffler will shortly commence volume production of its electromechanical camshaft phasing system for passenger cars for a series of Japanese engines. In design terms, this is a very compact design, consisting of a brushless DC motor and a high reduction ratio gear unit.  The gear unit is based on a flexible toothed belt with an oval rolling bearing. This transfers the engine speed at a ratio of approximately 70:1. “We therefore achieve a very good balance between the size of the electric motor and the phasing speed. Our gear units also operate completely silently,” explained Martin Scheidt, Engine Systems Development Manager at Schaeffler.

E-Clutch for manual transmissions cuts fuel consumption

Schaeffler has developed an intelligent, automatic clutch for previously purely mechanical or hydraulic clutch systems. Until now, this has been possible only in combination with automatic transmissions. The E-Clutch is therefore a significant step forward, as this type of transmission is far and away the most commonly used in many growing economies as well as in the lower and middle market segments in the European market. Today, approximately half of all vehicles have a manual transmission, even as global production continues to increase. The E-Clutch system from Schaeffler not only opens up new prospects for manual transmissions, but this configuration also provides a way into new markets and market segments for hybrid transmissions.

Depending on the level of automation required, Schaeffler has developed three stepped concepts for the E-Clutch for manual transmissions. Depending on the development stage, the new E-Clutch system either operates the clutch only under specific driving situations, or completely automates all clutch operations. This enables fuel saving driving strategies, from “sailing” to electrically supported driving, to be integrated into vehicles with manual transmissions.

“The E-Clutch from Schaeffler paves the way for hybridisation of manual transmissions, thereby opening up new markets and market segments,” said Uwe Wagner, Vice President Automotive R&D at Schaeffler.

Tests conducted using the up-and-coming WLTP consumption measurement cycle and realistic customer cycles have recorded reductions in fuel consumption from 2% (engine goes to idle) to 6% (engine switches off). Using a 1.2 litre petrol engine demonstration vehicle, Schaeffler has shown that it is possible to achieve savings of up to 8% in urban driving conditions. The function of “sailing” not only helps in the future consumption cycle, but can also be claimed today as an “eco-innovation” for the approval of reduced CO2 emissions.

Intelligent clutch pedal

In the clutch-by-wire concept, the mechanical or hydraulic connection between the pedal and the clutch release system is replaced completely. The opposing force on the pedal from the clutch release system, which is no longer required, is now generated by a new pedal force adjuster developed by Schaeffler. This contains an additional sensor that sends a signal on the pedal position to a clutch actuator. The driver is therefore not immediately aware of the automatic engagement but continues to drive as normal with a manual transmission. A recently developed, intelligent actuator undertakes the actual opening and closing of the clutch in all driving situations. This consists of a basic actuator that includes all the electronics, the e-motor, and a spindle drive. The connection to the clutch actuation is either mechanical or hydraulic depending on the application. The modular design means that it is universally applicable, which reduces the development time and overall system costs. This is an important factor in order to maintain the cost advantages of manual transmissions over automatic transmissions.

Clutch-by-wire is much more powerful than MTplus: the functionality of this clutch release system means that it can accommodate driving conditions with very high dynamic requirements, such as rapid gear shifting or emergency braking. The option of electrically tuning the transfer from pedal travel to clutch travel is considered particularly convenient. This makes it possible to have gear-related adaptation or a sport mode option, previously only reserved for automatic transmissions.

The performance of this technology can be clearly seen in the “Gasoline Technology Car” (GTC) co-developed by Schaeffler, Ford and Continental, where reductions in fuel consumption and CO2 emissions of 17 per cent were achieved with the automatic clutch making a significant contribution to this.

No pedal at all

Electronic Clutch Management (ECM) is technically based on the same system as clutch-by-wire, but without a clutch pedal. A sensor provides the signal for disengagement when the driver changes gear. Engagement follows automatically once the gear is selected. The high degree of automation in the ECM provides a good basis for integrating an electric motor into the drive train. By using a suitable battery in a 48V on-board electrical system, this system is used to drive the vehicle in all instances when the engine is running inefficiently, for example, when parking, in stop/start traffic or at low-speed urban driving conditions.

“ECM provides a technically elegant and economical step up to mild hybridisation, which could not be achieved with an automatic transmission,” explains Schaeffler.

Latest posts by Andy Pye (see all)

About Andy Pye

Andy Pye is a graduate of Cambridge University and has had a high profile career in the technical press as well as being a pioneer in web publishing.

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