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Longer-sighted lorries

23rd August 2012, Page 34
23rd August 2012
Page 34
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Page 34, 23rd August 2012 — Longer-sighted lorries
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Which of the following most accurately describes the problem?

The latest generation of cruise-control systems offers the kind of fuel economy savings previously only delivered by the most ‘far-sighted’ of professional truck drivers

Words: Brian Weatherley

It’s no secret that truck makers have long advocated the extended use of cruise control to save fuel. Unfortunately, cruise control can’t see the road ahead like a professional driver can, especially when driving uphill. In an attempt to maintain its pre-set speed, cruise control invariably applies full power unnecessarily right up to the summit – when it should be backing off the throttle and letting the truck’s kinetic energy take it over the top, saving fuel in the process. Making the most of a truck’s free energy is the first lesson of eco-driving, as well as reading the road ahead. Unfortunately, even the most conscientious drivers lose concentration sooner or later – and as their attention slips, so does their fuel economy. But what if their truck could ‘see’ the road ahead, adjusting power and changing gears automatically, based on its immediate location? Welcome to the world of predictive cruise control (PCC) – and if this all sounds like science fiction, PCC systems are already a reality offered by manufacturers such as Mercedes-Benz, Scania and Volvo.

Initial PCC bragging rights arguably go to Scania. Its Ecocruise enhanced cruise control (launched in 2006) used engine load and road speed to determine changes in terrain. All the driver had to do was set a minimum and maximum (up and downhill) speed limit – with a gap of at least 6km/h between the two to allow maximum use of the vehicle’s momentum – thereafter, Ecocruise, working in conjunction with Scania’s Opticruise auto-box and a retarder, did the rest automatically.

In practice, that meant applying full engine power at the first hint of a hill, then easing off the gas as the gradient reduced – unless the truck’s speed had dropped by more than 20km/h while climbing. On the downslope, Ecocruise used the truck’s kinetic energy to full effect, so in undulating terrain it approached the next hill at higher speed than with a traditional cruise control.

In trials, Ecocruise showed fuel savings of 5% or more and, interestingly, cut the spread between drivers in terms of fuel used from 35% to less than 20%. Although across a working day there was a slight loss in journey time (about 20 minutes) with Ecocruise, Scania declared: “In the minds of operators [it] was substantially compensated by the fuel saving.”

Working with GPS

Next, Daimler-Benz’s US Freightliner division took the logical step of adding GPS to cruise control to create its Run Smart predictive cruise control, launched in 2009. Using the GPS locator, Run Smart PCC effectively anticipates an approaching incline, building up the truck’s momentum, so it doesn’t lose any speed unnecessarily. And as the gradient reduces, Run Smart chops off the power, allowing the truck’s momentum to roll it down the reverse slope.

With GPS to pinpoint a vehicle’s position in relation to the approaching road, predictive cruise control systems are now proactive, and today GPS is an integral part of the latest cruise control systems from Scania and Mercedes. The former’s Active Prediction system, unveiled last December, uses GPS mapping data for western and central parts of Europe (if there is no mapping data, the system reverts to normal cruise control function) to detect the approaching road topography up to 3km ahead. Based on the terrain data, stored in Scania’s Communicator module, Active Prediction calculates the most fuel-efficient speed profile, in real-time, every second.

As with the earlier Ecocruise, the driver sets an upper and lower limit for cruise control; to provide sufficient leeway for the truck to gain speed before it starts to climb a hill. Scania recommends drivers set the downhill speed of the retarder at least 4km/h above the set cruising speed. To regulate the cruise control, the system continuously assesses several vehicleand topography-related factors, including the vehicle’s weight, cruising and downhill speeds set by the driver, its specification (engine-rating, gearbox and gearing), as well as the distance to the next hill and steepness of gradient.

Scania says its Active Prediction can provide fuel savings of up to 3% on highway or motorway driving, compared with normal cruise control. CM recently experienced it during our road test of the Euro-6-engined Scania G440 (CM 10 May) where our tester declared: “We firmly believe the Scania Active Prediction cruise control enhanced its fuel consumption.” For the record, it was a “very promising” 9.20mpg at 40 tonnes.

Integrating mapping software

Meanwhile, Mercedes’ Predictive Powertrain Control (PPC), available on the new Actros, operates on a similar GPS-based principle to Freightliner’s Run Smart – but with European mapping software and cruise control integrated with its PowerShift auto box, so all gear changing is done automatically. Mercedes promises fuel savings of up to 3% with PPC by being able to predict the approaching terrain. The PPC system costs about €1,700 (£1,367) for the mapping software, GPS antennae and control unit.

Like the Scania system, PPC drivers set an upper and lower speed range on either side of the normal top cruise-control limit (typically 85km/h on a motorway). This allows the truck to lose speed when cresting a hill, on the grounds that it knows it will quickly regain energy on the downslope – as ‘seen’ by the GPS mapping function. Mercedes says PPC provides coverage of approximately 95% of all motorways and major routes in Europe, including the LJK. As well as using data from the road profile ahead of the truck’s current GPS position, PPC also bases its automatic gear-shifting strategy on the vehicle’s gross weight, road speed and individual engine torque and power output.

CM has driven the PPC system in Germany and, combined with the downhill speed control function and a retarder (and the ease with which is puts the Powershift box into the eco-roll mode), it provides controlled foot-off driving, uphill and down dale – without a driver having to constantly view the road ahead and manually intervene with an auto box in hilly terrain, in order to achieve maximum fuel economy. Last but not least is Volvo’s I-See, which promises fuel savings of up to 5% and becomes fully available on FH and FH16 from 2013.

Technology that never gets tired

According to the Swedish manufacturer: “I-See imitates the driving style of good drivers who use the vehicle’s kinetic energy, accelerating in time and avoiding unnecessary gear changing. But unlike a driver, it never gets tired, it’s like an autopilot.” As with comparable systems, it’s designed to work best in undulating terrain, accelerating the truck uphill, remaining in a high gear for as long as possible before reducing the power and free-wheeling on descents to exploit the truck’s weight to save fuel. “When the truck rolls freely, virtually no fuel is used... many drivers who test I-See will see the driving style it adopts,” maintains Volvo.

I-See uses GPS mapping to tell the truck where it is, while tilt sensors on the I-Shift gearbox record the severity of a particular gradient the first time the truck ascends it. Thereafter, the data from that hill climb is stored in a data memory, with I-See capable of storing and recalling about 4,000 gradients, corresponding to a distance of 5,000km (3,100 miles). Volvo adds: “The fact that the system is not dependent on maps makes it more dependable since it always obtains the latest information.” I-See will be sold as an addition to existing I-Shift gearbox software options.

Given the need to find new ways to save fuel, the latest crop of predictive cruise controls deserve serious consideration – albeit with one major caveat. Far from de-skilling the professional driver, they allow him (or her) to concentrate on the things that matter most – steering, braking and observing. But to get the most from them, a proper vehicle handover and system indoctrination (including an on-road ‘show-me’ training session) is an absolute must. ■


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