Follow-up report on the 14th International CTI Symposium
7-10 December 2015, Berlin, Germany
The next generation of hybrid transmissions
At previous CTI Symposia, it became increasingly clear that hybrid transmissions call for an integrated view of powertrains. As a logical consequence, DHTs (Dedicated Hybrid Transmissions) were defined and discussed in public for the first time in Berlin. DHTs are a new breed of hybrid transmissions, and more than just an add-on solution. Two other forward-looking topics were also in the spotlight in Berlin: the impact of autonomous driving on transmission and drive technology, and the question of what energy forms tomorrow’s mobility needs. There is still ample scope for development – not just for electric cars, but for fossil and regeneratively produced fuels too.
The central importance of automotive transmissions was reflected in the 16 Topic Sessions on offer for the 1300 visitors to the CTI Symposium in Berlin. At the start of Day One, Professor Ferit Küçükay summed up the conflicting priorities for today’s transmission and drive developers, noting that there is still plenty of room for improving the conversion efficiency of chemical energy, for instance in conventional fuels or battery technology. He pointed out the new opportunities that arise from processing driver, vehicle and vehicle environment data, for example when optimizing operation strategies. After all, powertrains are increasingly affected by automated systems that improve drive comfort, driving safety and efficiency.
Yes to electrification – as long as it is affordable
The first plenary speaker, Dr Eckhard Scholz, CEO Volkswagen Commercial Vehicles, reminded listeners that drive electrification will need to make sense financially, particularly for customers in the commercial sector. Whereas emotional aspects can play a role when choosing passenger car, SME fleet operators have to calculate the costs for the entire lifecycle on a strictly rational basis. Put simply, “How much will a kilometre cost me?“ Lower costs for energy and maintenance spoke in favour of electric vehicles, while their significantly higher purchase price and lower residual value were disadvantages. Dr Scholz thinks electrified drives will gain ground mainly in the urban transport sector, especially with CO2 emission ceilings getting lower all the time. However, he believes financial subsidies are needed to prompt commercial users to go electric.
Downsizing hybrid transmissions
Mihir Kotecha, CEO Getrag Corporate Group, focussed on powertrain scaling in his lecture, right up to today’s and tomorrow’s hybrid drives. He began by presenting current Getrag hybrid transmissions. Since the electric motor is coupled to one partial transmission within the DCT, they can be scaled from around 15 to 75 kW without affecting package. Kotecha then surprised listeners with an interesting mental exercise: he listed the qualities of various powertrains, then concluded that while they were improving all the time, they were still not universal enough in terms of usability and fuel efficiency. He ran through different examples of drive technology, from 1975 through 2015 to the upcoming scalable mild hybrids and plug-in hybrids. Looking ahead, he posed a provocative question: What if we set a maximum speed limit of 160 km/h? If so, almost every hybrid drive component could be made significantly smaller and more efficient. As an example, Kotecha said a 100 kW electric motor and 50 kW internal combustion engine would need just two or four gears respectively. The resulting drive would be equally suitable for all-electric, emissions-free urban driving and for longer hauls. Thanks to the highly dynamic nature of the electric motor, it could be used far more universally than previous drives.
Dedicated hybrid drives – a new drive category
Dr Robert Fischer, Executive Vice President Engineering and Technology Powertrain Systems AVL, introduced the new category of Dedicated Hybrid Transmissions (DHTs), which was given its own separate session at the CTI Symposium 2015. Unlike add-on solutions, he explained, DHTs are “hybrid transmissions where the electric motor performs functional transmission tasks“ and is thus non-optional. He cited the powersplit Toyota hybrid as a classic example of drive aggregates grouped around a planetary gearset. Robert Fischer also mentioned the GM Voltec and solutions from Renault, GKN and Professor Tenberge, Ruhr-University Bochum. These were presented later on in the dedicated DHT session, along with AVL’s approach. Fischer went on to say that while the dedicated approach is less compatible with conventional drives, it also means individual components can be specified more efficiently. At production volumes of 100,000 units or possibly even lower, Fischer thinks DHTs could break even and would then become cheaper than add-on solutions.
Dedicated hybrid drives need production volume
Gerald Killmann, Vice President R&D Toyota Motor Europe, explained how Toyota’s successful hybrid concept came about and evolved. He said not everyone knew that in the past, Toyota used other architectures besides the PSD hybrid. His examples included a serial hybrid drive for a city bus (Coaster) in 1997, and a parallel hybrid with electrified rear axle in a van (Estima) in 2001. In 2003, there was even a parallel diesel hybrid in a small truck. To date, Toyota has sold around eight million hybrid drives, of which 99 percent meet the definition for DHTs as powersplit hybrids with their planetary gearsets. This scale effect, Killmann says, is one of the critical success factors. Interestingly, alongside the powersplit device full hybrid, Toyota is now more in favour of fuel cells than of further plug-in hybrid development. Killmann says this is because of hydrogen’s very high energy density, which he sees as a big advantage over batteries for long distance driving.
Customer data for the 2nd generation Voltec
The third plenary speaker on the topic of DHTs was Larry Nitz, Executive Director Transmission and Electrification, GM, who presented the second-generation Voltec hybrid drive. During development, Nitz says, customer data transmitted automatically with vehicle owners’ consent played an important role. The data supplier was GM’s own in-car Onstar Communication System. The data yielded surprising insights, including the fact that people like to drive their Voltecs dynamically. Nitz puts this down to the drive’s ’liquid acceleration’, and to the fact that drivers could have fun driving with a clear conscience, since their vehicles emit no local emissions. He said differences between the new Voltec drive and its predecessor include electric motors with greater power density, and a higher all-electric range of 53 miles. One fundamental change was that there are now two planetary gearsets, not one. That permits more operating modes, including most efficient electric driving with one or two electric motors, and two eCVT modes that complement a serial mode.
Climate change calls for radical technological change
It is very hard to predict which drives will prevail in future in detail, as Wolfgang Müller-Pietralla, Head of Corporate Foresight at Volkswagen, demonstrated on Day Two of the symposium. He pointed out that the global climate will reach a ’tipping line’ if we do not progress quickly enough towards energy forms that are low in CO2 or CO2-neutral. By 2030, he expects half of all vehicles to be at least partially electrified, a forecast he concedes is volatile. He also believes inductive charging systems could boost the electric car sector, and that power-to-gas might be a way to produce methane CO2 neutrally, making natural gas hybrids an interesting proposition. Müller-Pietralla says our relationship to cars will change significantly. “Everything will be connected, predictive systems will become more important, and there will be convergence with non-automobile industries“. He does not believe companies like Google want to develop and make automobiles themselves, saying their interest lies more in “the time customers spend in their cars“.
A plea for electrofuels
Dr Rolf Leonhard, Chairman of the Advisory Board, Bosch Engineering GmbH, began by spelling out that global energy consumption makes a global warming cap of 2 °C untenable. He said China, for instance, would exceed the planned CO2 emissions figure by around 400 percent, and that there was a gap between vision and reality in the EU too. By 2040, the increase in traffic would, sadly, ’overcompensate’ for reductions in CO2 emissions. Leonhard says electrofuels produced with regenerative energy are an even more likely solution than all-electric mobility, particularly since long-distance traffic will grow disproportionally. Leonhard thinks the EU can reduce CO2 emissions by 85 percent in 50 years if we cut fuel consumption by 60 percent, and use battery electric, plug-in hybrid and electrofuels in equal measures. If electrofuels are produced using power-to-liquid, ’CO2 recycling’ would be possible providing the hydrogen used for synthesis was produced regeneratively.
How autonomous driving impacts on vehicle technology
Dr Peter Rieth, Systems & Technology head at Continental’s Chassis & Safety division until the end of 2014, addressed the outlook for autonomous driving. Functionally, he defined three phases – ’sense’, ’plan’ and ’act’. Put simply, these equate with sensors, control units and actuators in automobiles. Dr Rieth said that with automation, driver and passenger workloads change as they delegate more and more responsibility. In line with SAE J3016, he distinguished six progressive levels of automation (0 to 5), whereby Level 5 means full automation without driver input. Dr Rieth believes a very high degree of automation can be achieved by 2020, with fully automatic driving without driver input by 2025 at the earliest. In both cases, all automobile systems, right down to drives, would need to be redundant because naturally, autonomous driving is only possible if accidents and failures of all types are ruled out 100 percent.
Autonomous driving changes the DNS of transmissions
Guillaume Devauchelle, Vice President Innovation & Scientific Development, Valeo, explained the impacts of autonomous driving on transmissions. He too referred to the SAE J3016 definition. Accordingly, clutch-by-wire solutions plus two or three pedals are also possible for Levels 1 to 3, but fully automatic transmissions are required from Level 4 upwards. Which transmissions prevail will also depend on how much comfort drivers expect. Devauchelle thinks step transmissions such as DCTs will be better for active driving functionality on Levels 3 or 4, with stepless transmissions for cocoon driving on Level 5. However, he continued, the more powerful electric motors become, the more their superiority in launch and boosting would compensate for their lower comfort. Devauchelle says Level 3 and 4 autonomous driving can be achieved with a 48-volt on-board system, while Level 5 requires full hybridisation with 300 volts. Looking ahead, he foresees a ’Transmission 2.0’ that will combine the characteristics of different transmission types.
Mid term outlook
Michael Schöffmann, Head Transmission Development Audi, spanned an arc between future demands and the company’s current hybrid technology. He thinks it is crucial for all levels of electrification to preserve total cost of ownership, and predicts that by 2025, energy density will have risen from roughly 220 to around 800 Wh/l. That would significantly improve the ranges possible with acceptable battery sizes. His talk centred on the new seven-step Audi S Tronic DCT. This has a modular build, with options that include all-wheel and hybrid, and extend up to a plug-in hybrid with a 100 kW electric motor. Looking ahead, Schöffmann also sees the possibility of a two-ratio electric rear axle for internal combustion powertrains. This would simplify transmissions by reducing the number of ratios inside to around four.
Tetsuya Takahashi, Senior Vice President R&D, Jatco, focussed on drivers’ needs and how modern CVTs can help meet them. On one side stand rational requirements such as consumption, comfort and safety; on the other, emotional aspects such as a responsive, sporty driving experience. Takahashi says the latter will no longer play a role in tomorrow’s autonomous driving, but that today’s transmissions must cover both aspects. He described the stepped D-Step mode in Jatco CVTs, designed for dynamic driving, as a functional complement that can do both. The new Jatco CVT7 improves efficiency by 5 percent, and has an interesting 8.7 spread made possible by a secondary gearset and a new thrust belt. Takahashi added that the Jatco CVT8 Hybrid benefits from the use of a dry multi-plate clutch.
Drive train 2030 – podium discussion
The overarching questions at this year’s podium discussion were “What will powertrains look in 2030 – and will electric cars stay in a niche?“ Participants were Dr Wolfgang Ziebart, Michael Schöffmann, Prof. Friedrich Stockmar, Jörg Grotendorst, Prof. Peter Gutzmer, Prof. Friedrich Indra and presenters Ulrich Walter and Rolf Najork. As in previous years, the public were able to vote on multiple questions.
On the question of the future of electric drives, the great majority believed internal combustion engines would still be around for a long time, and that electrification would progress slowly. However, there was broad agreement that 48 V hybrids will quickly prevail. As Friedrich Indra noted, one reason is that unlike more highly electrified drives, they have an acceptable cost-benefit ratio. How will the range of electric automobiles develop? An astonishing number of visitors can imagine vehicle ranges of 1000 kilometres by as early as 2025 or 2030. While that is certainly feasible, Dr Ziebart questioned whether it made sense, since charging times would increase accordingly. Prof Gutzmer predicts lithium-air batteries by 2030, but likewise see little sense in such high ranges. For Jörg Grotendorst, the main thing is to create an infrastructure where people can recharge everywhere, making range issues less important.
How much electrification makes sense in the near future? Interestingly, most listeners and discussion participants backed mild and plug-in hybrids, not full hybrids. Michael Schöffmann sees mild hybrids as a standard solution, with plug-in hybrids for heavy vehicles to meet legal requirements. Looking ahead to 2030, most of the audience voted for DHTs (Dedicated Hybrid Drives) as a sensible form of electrified drive. Prof. Stockmar favours electrified DCTs due to their efficiency; Michael Schöffmann sees interesting competition between DCTs and DHTs, while Dr Ziebart and Prof. Gutzmer expect a considerable percentage of manual shift transmissions to remain. Gutzmer says e-clutches could then become more important, for example by enabling sailing functionality. However, will powertrains still be an important criterion at all for tomorrow’s drivers? Three in four listeners said ’yes’, though the podium was more sceptical. Prof. Stockmar sees a general drop in people’s desire to own automobiles, while Wolfgang Ziebart believes the average customer does not notice any difference. Finally, everyone agreed that we need to look closely at how tomorrow’s drivers will use technology. “For older drivers, it will be about more safety,“ said Professor Gutzmer. “For younger drivers, it will be more about connectivity“. He said powertrains would need to deliver accordingly.
Co-existence of drive concepts
As the 14th International CTI Symposium in Berlin made clear once again, automobile drives need to be electrified due to legal requirements driven by real-life CO2 issues. However, the challenges of low energy density in batteries, lack of infrastructure and high costs persist. The new DHT transmission category offers an interesting opportunity in this respect, since DHTs can be configured for particularly high efficiency in both all-electric and fuel-based modes. DHTs might even be more than just a transitional technology. The question of which transmission topology to prefer is a matter for further discussion, as is the choice of the right energy source. If obtained regeneratively, fuels like methane and hydrogen – and CO2-neutral substitute fuels for petrol and diesel – still have big advantages due to their high energy density and storage capacity. The question is not necessarily whether electric drives will replace conventional drives, but rather how to get regenerative energy into vehicles.
More information and images: www.transmission-symposium.com
Author: Gernot Goppelt
15th International CTI Symposium, Berlin, 5-8 December 2016