Allison Transmission promotes automatic choice

Software that optimises transmission and shift schedules could help industry strike a balance between fuel efficiency and performance

The use of automatic transmissions in commercial and military vehicles has risen dramatically over the years. In North America, it commands the highest share of the commercial vehicle market outside the long-haul tractor segment. Closer to home, Europe has seen a notable increase in acceptance of automatic transmission in industrial sectors such as construction and distribution.

With rising fuel prices placing economy at the forefront of operators’ minds, and emissions regulations for non-road applications specifying NOx levels as low as 2.0g per kWh for 2011, transmission technology is being pushed more than ever to provide a better rate of fuel economy.

The challenge has led manufacturers to develop systems that they claim are more fuel-efficient and effective. However, an alternative has been proposed by Allison Transmission, a global manufacturer of hybrid propulsion systems and automatic transmissions, which claims that the use of software can go a long way in helping operators choose a set-up that improves economy, efficiency or retains essential performance.

Manlio Alvaro, European marketing manager at Allison Transmission, said: ’The software pack, known as Optimised Calibrations, has been developed to be flexible and powerful. We now have the ability to adjust a range of parameters to optimise a transmission to an engine, vehicle, vocational requirement, duty cycle, terrain or even the abuse from a poorly trained driver.’

The construction sector is an example of where striking a balance between economy and performance is crucial. ’Applications such as mining require material to be removed as quickly as possible,’ added Alvaro. ’Productivity is important but the rising fuel cost has led us to create a package for 2010 called Load Based Shifting Schedule [LBSS] that calculates real-time vehicle load and gradient to select the optimum shift schedule.’

The transmission Engine Control Unit (ECU) uses an algorithm to estimate, in real time, vehicle mass and topography. When the appropriate conditions are met, the ECU automatically switches to Economy or Performance mode. ’This ensures you get the necessary power by automatically switching to a Performance schedule only when essential, such as climbing an incline fully loaded’, said Alvaro. ’As the load is removed or as the terrain flattens out, the transmission swiftly and automatically changes to Economy mode. Testing has shown an articulated dump truck can function in Economy mode for 55-70 per cent of the time. In bus or distribution applications, the use of LBSS is equally valid and could improve economy by up to five per cent.’

To test its software in harsh environments, the group conducted a trial at Dmitrov proving ground in Russia on two LiAZ buses identical except for the transmission. Tyre pressure and wear condition were comparable, and each vehicle’s mileage was around 115,000km. Both buses ran simultaneously on a flat concrete ’dynamometric road’ for performance comparison, and then along a 39-stop hilly route to emulate a tough duty cycle. They were tested in several conditions but particular attention was paid to the city bus duty cycle provided by LiAZ Bus as a reference.
’To optimise fuel economy, the transmission should keep the engine within a narrow operating speed band,’ said Johan Verheij, Allison Transmission’s European application engineering director. ’However, the risk of shift cycling increases. Our new software has advanced logic to manage shift cycling, which allowed us to develop the economy calibration package.’

The tests showed the Allison-equipped bus achieved a 6.5 per cent fuel saving over the configuration with a competitive automatic transmission, indicating that automatic buses, properly configured, can be among the most fuel-efficient and still deliver acceptable performance. The use of prognostics in the software, according to the group, also prevents over-maintaining of the transmission.

It does this by monitoring transmission parameters such as operating time, output revolutions and shift density and fluid life and automatically adjusting them. The software then provides advanced warning of oil and filter life, as well as overall transmission health.

The life monitoring determines when oil and filter need to be changed, maximising life, reducing cost and unnecessary environmental disposal. Coupled with the use of approved synthetic oils, the group claims it is possible to achieve oil change intervals of 480,000km.

Design essentials

The key facts to take away from this article

» Allison Transmission has developed Optimised Calibrations software
» The software can adjust a range of parameters to optimise transmission
» LBSS calculates load and gradient to select the optimum shift schedule
» In tests, a bus equipped with the technology achieved fuel savings

What’s new
Drives, motors and gears

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