Designing and engineering 360º steering capability for a production autonomous electric vehicle (EV) is no mean feat. But Protean Electric also combines this pirouetting capability with an in-wheel electric motor, an innovative suspension and pneumatic ride height control. Its wheel-at-each-corner module is called Protean360+ and has been designed initially for next generation urban mobility pods but could be applied to a wide variety of autonomous vehicles.
Development of the 360º capability began in early 2018 and is the latest element to be added to the company’s ProteanDrive in-wheel system, on which development began more than 10 years ago to fulfill emerging autonomous transport visions. Protean Electric is anticipating the need for moving people and goods in urban areas by allowing 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.
“We’re not aware of any other systems with the same capabilities, including unlimited steering and ride height control,” said Dr. Chris Hilton, the company’s CTO. “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 varied.”
Operational cost efficiencies
Although he was unable to give an indication of unit cost, Hilton said Protean Electric is convinced its adoption would result in economic advantages for operators and vehicle manufacturers. This via greater maneuverability, superior efficiency and a higher earning potential from the interior space gain. “Operational cost efficiencies can be realized, too,” Hilton explained. “Electronics are integrated into the electric motor enabling easy real-time monitoring of wear and tear on areas such as bearings and suspension, thus improving predictive maintenance.”
Packaging proved the most challenging development. “Novel solutions were required, for which we have patent applications,” Hilton said. “Firstly, for the steer-by-wire unit that supports unlimited rotation without stressing the cables and pipes that supply the Protean 360+ module; and secondly, 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 360º 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 the module. The system allows a vehicle to spin through 360º within its own footprint. 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 provides independent control at each corner of a vehicle.
Examples of the 360+ will start prototype vehicle trials next year, Hilton stated, with development work carried out at Protean Electric's R&D center in the UK, in partnership with specialist engineering development company Arcadlon in Graz, Austria. “Arcadlon has expertise in the rapid implementation of advanced concepts,” Hilton said. 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 used for the 360+ is designed for integration into an 18-in. wheel and develops 1,250 Nm (922 lb-ft) peak torque and 80 kW (107 hp) peak power. The permanent magnet synchronous motor is integrated with the inverter and a dedicated liquid cooling circuit, all packaged within the wheel rim. Positive or negative torque can be applied “within milliseconds”, aiding performance of traction-control systems and supporting shorter stopping distances.
The rotor of the electric motor connects to the hub, delivering torque directly to the wheel, reducing power-transfer losses. Hilton explained that the Protean360+ module, including the ProteanDrive motor at its core, is scalable to suit vehicles of different sizes with different power and torque requirements. Initial applications may be used in constrained environments such as campuses, with plans to put vehicles using Protean360+ on the road within five years.Continue reading »