Autonomy’s ‘Pirouetting’ Future

January 1, 2020

Stuart Birch

Designing and engineering a 360-degree steering capability for a production electric autonomous road vehicle’s four wheels is no mean achievement. But Protean Electric also combines this pirouetting capability with an in-wheel electric motor, “innovative” suspension and pneumatic ride height control into an all-in-one package. Its adroit wheel-at-each-corner module, called Protean360+, is designed initially for next-generation urban mobility pods. But it could also be applied to a wide variety of other autonomous vehicles.

Development of the 360-degree capability began in early 2018. It is the latest element to be added to the company’s ProteanDrive in-wheel system, on which work started more than a 10 years ago to specifically meet emerging needs for radical new urban vehicle technology combined with autonomous transport visions. These include autonomous passenger cars, light-duty commercial vehicles and other future mobility solutions.

Protean Electric particularly anticipated the need for moving people and goods in urban areas where parking and maneuvering regular vehicles could be increasingly challenging. Application of the deft Protean360+ allows for curbside precision in very tight spaces. Once parked, the module’s pneumatic ride control system allows a vehicle to “kneel”, lowering its entry point to curb height.

Interviewed by AVE, Dr. Chris Hilton, the company’s chief technology officer, said his team is “not aware of any other systems with the same capabilities, including unlimited steering and ride height control. Part of its attraction is that it allows creation of a very flexible, totally flat-floor vehicle platform that can be adapted for various uses including commuting and delivery of goods and services, so the range of vehicles supported will be very varied.”

Operation cost efficiencies

Cost of such radical solutions is invariably a question raised by OEMs. Although he was unable at present to give an indication of unit cost, Hilton said Protean Electric is convinced that its adoption in target vehicles, relative to traditional solutions, would result in economic advantages for operators and vehicle manufacturers via increased safety, greater maneuverability, superior efficiency and enhanced robustness, together with reduced cost of ownership and a higher earning potential from the interior space gain.

“Operational cost efficiencies can be realized, too,” he said. Electronics are integrated into the electric motor enabling real-time monitoring of wear on bearings and suspension, thus improving predictive maintenance.

Packaging proved the most challenging development. The 360-degree steering had to be compact and able to fully rotate without consuming excessive vehicle space. “Novel solutions were required, for which we have patent applications,” Hilton explained. “First, for the steer-by-wire unit that supports unlimited rotation without stressing the cables and pipes that supply the Protean 360+ module; and second, to a multi-link suspension system with an additional lower-wishbone pivot. This quad-pivot system keeps the suspension system within the required packaging envelope while allowing the desired suspension kinematic.”

The steering system includes a rotating interface above the module’s main arm. The top of the interface is fixed to the vehicle and a lower interface is fixed to the arm of of the module.

The system allows a vehicle to spin through 360 degrees within its own footprint. As the arm module rotates, the full component set rotates with it. The steer-by-wire unit is positioned above the interface enabling axis points at the bottom of the wheel. The module also incorporates a pneumatic ride height system that shares its reservoir and compressor with other systems in the vehicle. It provides independent control at each corner of a vehicle.

Prototype trials

Examples of the 360+ will start prototype vehicle trials this year, stated Hilton. Development work is being carried out at Protean Electric’s R&D center in the U.K. in partnership with Arcadlon, a specialist engineering company in Graz, Austria.

“Arcadlon has expertise in the rapid implementation of advanced concepts,” said Hilton. For the in-wheel motor system, Protean has been collaborating with several universities and “high-quality technology partners” for more than a decade.

The ProteanDrive Pd18 in-wheel motor system is used for the 360+. Designed for integration into an 18-in wheel, it develops peak outputs of 1,250 Nm (922 lb-ft) and 80 kW (107 hp). The permanent magnet synchronous motor is integrated with the inverter and dedicated liquid cooling circuit, all packaged within the wheel rim.

Positive or negative torque can be applied “within milliseconds,” aiding performance of ESC, ABS and traction control systems.

The design also supports shorter stopping distances – typically 7% less – according to an independent study (Satoshi Murata “Innovation by in-wheel motor drive unit,” International Journal of Vehicle Mechanics and Mobility, Vol. 50, issue 6, 2012).

The rotor of the electric motor connects to the hub, delivering torque directly to the wheel, reducing losses in power transfer. Hilton explained that the Protean360+ module including drive motor is scalable to suit a range of vehicle requirements.

Initial applications may be what he terms “constrained environments” such as campuses. Customer on-the-road use is expected “within five years.”

Adds KY Chan, CEO of Protean Electric: “Transport-as-a-service urban mobility is gaining momentum, and with it the need for a new class of urban transport vehicles. The Protean360+ corner module was born from our team’s innovative thinking about how to meet the requirements of these next generation urban vehicles.”

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