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In-wheel drive

Featuring CAN connectivity

The Orbit electric autonomous shuttle features Protean’s in-wheel drives, which maximizes interior space.

The Orbit electric autonomous shuttle implements two CAN-connected in-wheel drives by Protean (Photo: Fisker)

Designed by Fisker the Orbit enhances the passenger experience in urban environments, including smart city ecosystems. As a sample scenario, people will no longer have to wait at a bus stop, as Orbit shuttles will be connected – with their locations available to be viewed on a mobile application for set routes. The OEM has selected Protean’s in-wheel E-drive system. With the vehicle not featuring a steering wheel or pedals, the configuration enables the Orbit to carry passengers without the intrusion of traditional powertrain components.

Henrik Fisker explained: “The Fisker Orbit already encompasses breakthrough automotive technology, design innovation and exciting touches that will change the way urban populations think about short trip experiences. We selected Protean’s in-wheel powertrain technology to further deliver on those promises. The fastest path to fully autonomous vehicles – without a steering wheel – is through shuttles like the Orbit, and we’re excited to lead the charge into the future of mobility with such world-class, sustainable technology.” K.Y. Chan from Protean Electric added: “Fisker aims to set a new standard of excellence and performance in the electric vehicle industry and mobility services. We are delighted to be partnering with their team to further solidify that standard. Our technology provides a digitally smart, stand-alone eDrive solution with packaging advantages, new vehicle design opportunities, performance benefits and cost savings.”

The Orbit shuttle will be available in either two-wheel or four-wheel drive configurations. The company will begin testing prototypes of the vehicle – with integrated Protean powertrains – this year, while full deployments of the Orbit on a set route are scheduled for next year.

In-wheel electric motors deliver torque directly

Most road vehicles are powered by a single engine or motor generating torque at the wheel hubs. The wheels must be free to move at different speeds to one another to allow for cornering and variations in road surface. This is achieved with the differential, a mechanical device, which delivers equal torque to both wheels on an axle while allowing them to rotate at different speeds. Wheels can then rotate at their natural speeds as determined by the kinematics of the vehicle.

In case of the wheel-motors, the same torque demand is requested to each of the motors, so that the vehicle behaves as if there were an open differential. The traction control system can be used to control loss of traction, as in a conventional vehicle. On the other hand, enhanced vehicle ride and handling can be achieved by varying the torque distribution among the wheel motors dynamically.

The in-wheel motor system consists of two units installed on opposite sides of the vehicle, one in each front wheel or one in each rear wheel. Each unit comprises the electrical machine, inverter with micro-processor control and a friction brake. In the case of Protean’s products, these are integrated into a single package, which is housed entirely within the wheel rim.

Each in-vehicle drive communicates via CAN with the vehicle controller (Photo: Fisker)

The vehicle control unit (VCU) communicates with the motor system via CAN. It sends torque demands every few milliseconds. In response, the motor system develops the demanded torque at the wheel hub. By return the motor reports its state of health and the maximum available torque. It can also report its speed, which the VCU may use for advanced traction control functions. Note that the motor is not a speed-controlled device. The VCU cannot demand a speed from the motor system. As with a conventional drive-train, the wheel speeds are a consequence of the torque applied at the wheel hub, combined with the resistance to rotation which is dominated by the vehicle inertia.

hz



Publish date
2018-10-09
Company

Fisker
Protean

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