Engineering 101

In-Wheel Motors for Electric Vehicles Evolving Fast

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Electric motor drive is key to all electric vehicles (EV) and it is taking new forms. See IDTechEx report, ‘Electric Motors for Electric Vehicles Land, Water, Air 2019-2029’. In-wheel motors are successful in two-wheel EVs but they have rarely been seen in larger vehicles due to safety and cost concerns and a fear that unsprung weight gives a rougher ride. Near-wheel motors are a compromise.

However, eliminating transmission and freeing up space is attractive and, to good effect, BYD electric buses have two front motors in hubs with wheels fitted on top. Developed in-house, they are used in volume.

There is now a continuum of design options with in-wheel motor design leading to extra benefits as one progresses to self-sufficient wheels. These may incorporate their own motors, controllers, clutches and back-up brakes. In effect, the motor may act as several for redundancy with no single point of failure.

Promised benefits include vectored steering and scalability, there being six in-wheel motors on the planned Nikola fuel cell truck and four on the Lightyear solar family car both with deliveries in 2020. We now go beyond vectored traction but there is more.

Protean’s latest module combines powertrain, 360 degree steering and suspension technologies in a single component. Called Protean360+, it is the first of its kind for use in commercial vehicles, giving them unrestricted steering capability because each wheel can be steered 360 degrees around its own axis like castors on a trolley. A rotating interface is located above the main arm of the module.

This maneuverability is combined with innovative suspension and pneumatic height adjustment of the vehicle. The EV can be positioned sideways, frontally or with the rear directly on the kerb: Passengers can step to the sidewalk without gaps. Any EV can park in very confined spaces benefiting cities.

As soon as the vehicle has come to a standstill, the pneumatic height adjustment ensures that the vehicle is lowered to the kerb. The loading and unloading of heavy goods or the boarding and exiting of the vehicle for passengers with reduced mobility are rendered seamless.

“Transport services are on the rise in urban mobility and a new class of inner-city transport vehicles is needed,” explained KY Chan, CEO of Protean Electric. “Whether private or sharing, for passengers or goods, operated by humans or autonomous – these new transporters must be equipped with new technology to optimally fulfill their purpose.”

For robot shuttles and last-mile delivery EVs, the maneuverability improves radically. On the other hand, in-wheel motors in light aircraft may be key to Extremely Short Takeoff and Landing ESTOL.

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