FEATURE TEST & MEASUREMENT WHY HYBRID VEHICLES BITE THE BULLET
Jeff Phillips, head of automotive marketing at National Instruments puts the hybrid powertrain/drivetrain of the latest electric vehicles under scrutiny
I
t was exciting news when car manufacturers first announced plans for
the electrification of their vehicles. This would mean no emission, longer range and great drivability with instant torque. However, under closer examination, these vehicles are mostly plug-in hybrid variants of existing vehicles and new full battery electric vehicles (BEVs or EVs) will largely exist at the high end of the market – e.g. the all-electric Jaguar I-PACE, 240-mile range advertised. On the other hand, plug- in hybrids will flood the mass market – e.g. the Volvo XC60 T8 Twin engine with a 28-mile all-electric range and the MINI Countryman PHEV with a 15-20-mile all- electric range. Hybrids can be considered a design
compromise and that’s why not everyone may be a huge fan of them. A hybrid powertrain includes both internal combustion and electric energy generation components, which substantially increases vehicle complexity. Additionally, there are many types of hybrid powertrain/drivetrain compositions being developed from mild hybrid to full hybrid to plug-in hybrids, each with multiple variants in terms of electric powertrain integration strategies.
Figure 1:
Spectrum of ‘electrified’ hybrid powertrain variants between an internal combustion engine and a battery electric vehicle
“During the verification and validation
process, test engineers will deal not only with the electric powertrain AND the ICE powertrain, but with the added complexity of tight integration and interactions between the two systems”
With a hybrid, engineers must still
incorporate all the internal combustion engine (ICE) components with their corresponding design constraints; thus, they cannot take full advantage of the design freedoms an all-electric powertrain design provides. A hybrid vehicle will additionally require more processing power and software control sophistication to manage the dynamic ICE and electric powertrain interfaces. During the verification and validation process, the test engineers will deal not only with the electric powertrain AND the ICE powertrain,
10 SEPTEMBER 2018 | ELECTRONICS Figure 2:
Powertrain and test complexity for powertrain designs
but with the added complexity of tight integration and interactions between the two systems. Consider how companies like Subaru tested their ECU to meet thorough test coverage needs for difficult-to- replicate test cases, such as motor runaway due to a loss of traction on icy roads. The design complexity of integrating two powertrain technologies in one vehicle results in increased testing needs and costs. When it comes to design complexity and testing, it’s the worst of both worlds. EVs have a much simpler powertrain with fewer moving components, less failure points, and lower maintenance costs. Eliminating the ICE components will reduce testing requirements and decrease overall complexity to a level lower than the ICE- only era. So why are automakers not jumping all-
in on full electric vehicles? The technology is superior – simpler powertrains with far fewer components. The environmental implications are obvious – zero emissions. Let’s not forget that instantaneously available full torque from the jump makes them more fun to drive! The answer – battery cost and charging infrastructure. Key attributes such as range and battery charge time, simply aren’t at a level where they are financially viable for the mass market segment. UBS research estimates that GM loses $7,400 on every mass market targeted Bolt sold (UBS Limited,
2017). The financial angle is why automakers with aspirations for all-electric vehicles will target the high end of the market. Conceptually, this will allow them to profitably drive innovation and development on their EV platforms, which will (hopefully) result in more efficient designs and drive the price of the technology down. Currently battery pack costs are estimated to be decreasing at 15% year over year (Holland, 2017). As we progress towards that time, governments around the world are implementing regulations for reduced or eliminated emissions, increased fuel economy, and even mandates for prohibiting ICE-only vehicles before full BEVs make mass market sense. These will bring increased fuel economy and efficiency, and lower fleet emissions. Unlike the current losses endured on Chevy Bolt and Tesla Model 3 sales, the financials work out on the positive side. And the technology seems like it’ll tick all the boxes on the “balanced vehicle design” attribute checklist. The promise of an ‘all-electric fleet’
really means releasing varying types of hybrid technology and working on a few high-end all-electric vehicles while waiting for the economics to improve. Between the intense competitiveness of the market, government mandates, and projections on cost effectiveness of mass market EV technology that delivers on key attributes, you can’t blame the automaker executives; And that’s why we will have to get through the hybrid era before seeing real EV mass market introduction. Once automakers make the move to full EVs, designers can get rid of all that ICE complexity like transmission, belts, the combustion engine. They can shift around the centre of gravity by putting the battery pack in the floor. They can evolve structural integrity and rigidity in new and interesting ways. They can benefit from the great characteristics of electric motor powertrains, such as regenerative braking and instant torque from standstill. Right now, design engineers must be looking forward to the death of the hybrid, and the test engineers probably can’t wait either.
National Instruments
www.ni.com T: 01635 523545
/ ELECTRONICS
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