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Graphic element Research > Growth > Research projects > Previous projects > Transport > Full speed ahead for hands-off transmission
Graphic element Full speed ahead for hands-off transmission
Safe and efficient transport is essential for the development of an open and active economy. While global competition in the automotive sector remains hot, Europe is leading the way in certain high-tech areas. The Brite-Euram S-MATIC project has succeeded in developing a continuously variable transmission system. This treats the entire drive system from engine to wheels as an integrated unit, controlling it centrally without user intervention, providing exceptional driving comfort and freedom, continuous variable speed under all conditions, low emissions and superior overall efficiency. This innovative system represents a new generation of transmissions, which could prove particularly promising for heavy vehicles.

Most of us could not imagine driving a vehicle without either shifting gears or having them shifted for us automatically. Indeed, many of us enjoy the sense of power and control experienced while operating a manual gearbox. But some passengers may feel otherwise, having had to put up with abrupt and often unexpected speed changes in cars, taxis and buses. Putting aside the question of comfort, the inherent inefficiency involved in having to shift from one gear to another and the high potential for driver distraction and mistakes would seem reason enough to look for an alternative. Such concerns are especially relevant to large commercial vehicles, in particular farm tractors, loaders and other machinery where operators have a number of other tasks to carry out while driving.

Success is a team sport

Partners cite several factors which contributed to the project's success, including the complementary nature and verticality of the consortium. The team comprised two key users, MB-Unimog for trucks and Sisu-Valmet for tractors, Sauer-Sundstrand, a developer and supplier of hydrostatic components, VDO, a developer and supplier of electronic equipment, transmission developer SDP and research group AVL-LIST. All partners played an important role in targeting an existing product need, providing strong leadership and management and, finally, the highly strategic manner in which the project was undertaken.
S-MATIC aimed to develop a continuously variable transmission system, based on the principle of hydrostatic-mechanical power splitting. Engine power is divided into two components, one mechanical and the other hydrostatic, both linked to an advanced planetary gear set. Planetary gears, as their name suggests, are modelled on the solar system - a sun pinion is surrounded by planet pinions and a ring gear, all in a constant mesh. Planet pinions rotate around the sun gear inside the ring gear. Changing the power flow through the planetary gears alters speed and direction.
The new transmission includes advanced electronic systems, maintaining torque connection from zero to maximum speed and treating the entire drive system from engine to wheels as an integrated unit. It separates the driving strategies for speed and power take-off and controls the whole process centrally without the need for driver intervention. All of this means exceptional comfort and freedom for both driver and passengers with variable speed maintained continuously under all conditions.

Environmentally and economically sound

One of the most important advantages of the new system is a reduction in exhaust emissions, particularly under 'lean burn' conditions. In conventional multiple gear systems, the efficiency of fuel consumption varies as a driver runs through the range of speeds within a given gear. With the new transmission, rather than having to jump abruptly from one gear and one fuel burn condition to another, fuel consumption is optimised across the entire range of speeds. This, along with the complimentary mechanical and hydrostatic power sharing, allows for significant improvements in overall efficiency.
The leading project partner was ZF Steyr (previously Steyr-Daimler-Puch/Antriebstechnik, which was taken over by ZF Passau in May 2000), a supplier of transmissions for agricultural tractors and trucks. Located in the Austrian city of Steyr, in an area of particular EU interest because of its depressed industrial structure and high unemployment rate, the company has spent over 30 million euro on the new transmission system. S-MATIC is one of the largest and most complex projects ever undertaken by the company. The new system represents not only a new generation of transmissions, combining modular design with high performance and efficiency, but could play a vital role in job creation.
S-MATIC has been thoroughly tested, both in Europe and the United States, and has shown outstanding results in terms of performance, efficiency and durability. Production is set to begin, the partners' main objectives being to replace 4-step powershift and full powershift transmissions, as well as conventional automatic ones, by offering better technology and more features for a competitive price. ZF STEYR's project feasibility study cited a realistic volume estimate of 5,000-8,000 units per year, both in Europe and the US, representing an additional annual production volume of 20-30 million euro.

Just the job for heavy vehicles

Initially, the new system will be targeted at applications requiring high towing forces and thus a high power-to-rpm ratio: in particular tractors, off-road vehicles and construction machinery. Future applications could include public transport, as smooth and constant acceleration in traffic would improve both comfort and safety for bus passengers, while lower exhaust emissions would greatly benefit EU urban environments.
The system's ultimate success will depend on its ability to compete with similar emerging technologies and market conditions. Although most lorry and tractor manufacturers make their own transmissions, thereby putting them in direct competition with S-MATIC, the partners say that the heavy investments necessary for the development of new transmission systems may well persuade those manufacturers to opt for out-sourcing.

Cordis RCN: 31963
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