GKN Tests BEV With 2-Speed Transmission And Torque Vectoring

MAR 3 2019 BY MARK KANE 15

GKN traded simplicity over efficiency and torque vectoring

GKN Automotive has started trials of the world-first all-electric car equipped with two-speed transmission and torque vectoring between front wheels. Extensive winter testing are performed in Arjeplog, Sweden.

The technology demonstrator called GTD19 is based on a standard Jeep Renegade (originally all-wheel-drive ICE) and offers:

  • 120 kW of power
  • up to 3,500 Nm of torque on wheels (up to 2,000 Nm per wheel)
  • front-wheel drive

According to GKN, the two-speed transmission enables to achieve best combination of efficiency, acceleration and range, while torque vectoring on the front axle “provide more noticeable benefits than rear- or all-wheel drive configurations, due to the relative ease of breaking traction in a front-wheel drive car”.

“The GTD19 is equipped with an optimised two-speed ‘Seamless shift’ eTransmission and smart shifting strategy, which has the potential to extend vehicle range as well as provide greater torque, acceleration and a higher top speed. Efficiency is further enhanced by the GTD19’s eAxle’s coaxial format, while exceptional stability and dynamic performance is possible thanks to the torque vectoring capability of GKN’s eTwinster system.”

We are not aware about any production mainstream BEV with two-speed transmission, but maybe at some point in the future manufacturers will give it a try. GKN supplies drivetrains for various electrified cars and boast that order book for 2018 was worth £3 billion ($4 billion).

Hannes Prenn, COO of GKN ePowertrain commented:

“This new technology demonstrator showcases how we are evolving and improving integrated eDrive technologies to help OEMs further improve efficiency, safety and driving dynamics.

“Within the last year, we have seen a 40% increase in the value of our eDrive order book, rising from £2 billion at the end of 2017 to confirmed business now worth £3 billion. Our dedicated focus on production and development of electrified drivelines will enable us to support the rapid acceleration in demand for BEVs equipped with all-wheel drive systems in the coming years.”

GKN Trials World-First Battery Electric Vehicle With Two-Speed Transmission And Torque Vectoring

More about the GTD19 and GKN:

GTD19 technical demonstration vehicle

The GTD19 vehicle undergoing testing in Arjeplog integrates GKN’s two-speed ‘Seamless shift’ gearbox with two speeds and torque vectoring. The technology is related to the two-speed technology in last year’s ‘GTD18’ Mercedes-AMG GLA 45 test vehicle, which demonstrated the benefits of an eTwinster rear axle e-motor, two-speed eTransmission and torque vectoring by twin clutches; paired with a mechanical Twinster on the front axle.

The set-up in GTD19 provides pure electric power with two-speeds. The electric two-speed gearbox is configured to ensure the shifts are seamless, with minimal losses in power and torque and the potential for faster acceleration, improved efficiency and a higher top speed.

GKN’s award-winning Twinster torque vectoring technology delivers specific advantages for vehicle stability, agility and safety. Aiding modulation of the high initial torque of the electric motor, Twinster governs acceleration making it swift and smooth, while also providing greater lateral control and optimised front-wheel driving dynamics for both safety and driver satisfaction.

The advanced eDrive system in the GTD19 replaces the Jeep Renegade’s internal combustion engine with a 120kW GKN e-motor, delivering maximum torque of 3,500Nm and vectoring of up to 2,000Nm to either of the front wheels when required. Front-wheel drive applications of torque vectoring provide more noticeable benefits than rear- or all-wheel drive configurations, due to the relative ease of breaking traction in a front-wheel drive car. Not only can the Twinster system keep the front wheels in check during acceleration, it can correct an understeer yaw moment experienced by a driver entering a corner at speed. The system prioritises torque delivery to the outer wheel helping to correct the natural understeer characteristic typically associated with a front drive vehicle.

GKN Systems integration

Significantly smaller than systems with equivalent power outputs, the eTwinster two-speed coaxial system can be easily integrated into existing vehicle platforms. It is readily adaptable for use in front-wheel drive, rear-wheel drive or all-wheel drive applications extending from entry-level electric city cars to plug-in hybrid luxury SUVs and fully electric all-wheel drive hypercars.

For the GTD19, all the drivetrain technology was integrated with ease into the existing vehicle platform without major modification, including both a GKN-derived electric motor and GKN-developed inverter controls, supplementing the company’s advanced eAxle. All software is programmed by GKN to enable seamless shifting of the two-speed transmission and torque control on the front axle, with minimal power and torque loss during changes.

GKN has pioneered advanced eDrive technology since 2002, acquiring unrivalled systems integration and production experience to transfer the technology from niche vehicles to high-volume mass-market applications. It has already supplied complete eDrive systems to some of the most influential and successful plug-in hybrid programmes for OEMs including BMW, Mitsubishi, Porsche and Volvo.

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15 Comments on "GKN Tests BEV With 2-Speed Transmission And Torque Vectoring"

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“which has the potential to extend vehicle range”

The main question would be by how much?

Simplicity (single gear) has a benefit. Trading the simplicity for a more complex system should come with a substantial advantage. Otherwise, the trade will turn out to be a bad deal. Now, what would be a substantial advantage? How much would the increase in range have to be? Would an increase of 10% more range already be substantial? Or will it have to be more than 10%?

A 10% increase would be amazing.
Rimac already uses a 2 speed rear end.

@ John

I don’t think that 10% increase would be amazing. Reasonably good would be a better qualification, but that’s just my personal opinion.

I think @ least a 25% or better range increase could probably justify adding a two speed transmission , depending on the price and extra maintenance trade off .

I suspect this could be useful for autobahn driving cars and maybe heavy duty vehicles.

I believe I have read that the upcoming Tesla “roadster II” is going to have two speed transmissions (for multiple motors) in order to be able to combine SUPER ludicrous acceleration with a SUPER ludicrous top speed. I would bet that for most EVs the added complexity/cost of a two speed gearbox will not generally be worth it in terms of range/acceleration benefits but time will tell.

If it can be controlled thorough software so the driver doesn’t need to care about it and if it costs less than adding the equivalent additional battery, then it’s not relevant whether it’s a 10% improvement or 25%.

Another question to ask:
Does the use of a transmission allow the use of a less expensive motor without sacrificing performance, making the overall system less expensive?

The potential savings would have to come from not having to operate the electric motor at a very wide range of RPMs.

If this turns out to be true, the transmission should be a CVT.

I tried but failed to find what gear ratios that might be used. Does anyone know?

Most electric cars have a dive ratio of over 5:1 , Chevy Spark EV had something like 3.5:1, 2001 Prius had 3.2:1, a traditional transmission 4th gear is 1:1.

In traditional cars, there’s also final drive ratio that you must consider. SparkEV has about 1ft radius tire, 3.17 drive ratio on 2014. 60 MPH is about 90 ft/sec. 90/(2*pi)*60*3.17 = 2724 RPM at 60 MPH. If it a gas car has 1:1 ratio, it’d spin only 860 RPM at 60 MPH, even less with bigger tires, highly unlikely.

I found one site that mentioned a first gear ration of 17:1. That was for SUV applications where high torque (3000 Nm) is needed moving away from a stop (towing maybe?).

Many have speculated that the EV motors themselves will become variable where the magnets can shift, move, etc…GM already filed a patent: https://www.gminsidenews.com/articles/gm-patents-an-electric-motor-with-multiple-magnet-lengths/

This would kinda be the electric motor equivalent of a CVT gearbox. (but hopefully more reliable in the real-world)

(CVT = Continual variable transmission; if a normal gearbox is like a trumpet, then CVT is like a trombone. It’s an awesome idea that has never really taken off because it isn’t reliable. Note that Toyota’s hybrids are sometimes referred to as CVT, but in fact it’s a function of their hybrid drive system that gives them the same effect; they are not using a CVT gearbox)

Basically, you can also have a multi speed electric motor, with different winding and managing the connexion between them.
It could also be just a star delta two speed one tha would cover all its needed for ev’s.
However with today’s power electronics, it’s probably more efficient and reliable to take this path than a mechanical one.

Early Tesla Roadsters had a 2-speed (maybe 3-speed) gearbox.