We Will See

“Hub or wheel motors have been used in prototype electric cars and trucks, though none are yet in volume production. They are quite common in electrically assisted bicycles and other personal transportation vehicles.
Now, Michelin has taken the hub motor idea one step further with its Active Wheel. Besides the electric drive motor found in all hub motors, the Active Motor also includes the vehicle’s suspension and brake components.

Along with a small but powerful main drive motor, a second motor powers the active suspension system that’s fitted vertically across the diameter of the wheel. The suspension, which is now electrically controlled, can automatically and very rapidly correct for pitching and rolling. Response times of just 3/1000ths of a second are claimed. Finally, a ventilated brake disc is fitted inside the rim. Because it’s larger in diameter than a conventional brake disc, the disc depth is smaller, allowing more compact packaging.

According to Michelin, the Active Wheel greatly simplifies vehicle design because an engine gearbox, clutch, transmission shaft, differential, and shock absorbers are no longer needed. Besides being simpler, the vehicle can be substantially lighter and thus more energy efficient. Packaging propulsion and suspension components in the wheel frees up space at the front of the car, which could be used to improve the absorption of impact energy.

Other advantages include the potential for a flat floor and more efficient interior packaging.”

http://www.greencar.com/articles/michelin-hub-electric-drive.php

“*A stock 2007 Ford Focus was compared with an identical vehicle modified with 66 lb (30 kg) of ballast fitted to each wheel. The weight was distributed between rotating and nonrotating unsprung masses as to broadly replicate Protean Electric’s PD18 (18-in diameter) wheel-hub-motor unit. The project plan included three phases of analysis and testing.

Phase 1 focused on modeling of different modifications, including suspension spring, bushing, and damper rates, and different tires and pressures, and their effects on the IWM-equipped vehicle. It was determined that simply fitting a standard Focus ST suspension (an upgrade on the stock base car) would be a good practical solution.

In phase 2, the stock vehicle was modified with the Focus ST suspension. This setup included revisions to the front and rear spring rates, dampers, and the rear antiroll bar. In phase 3, the Focus with the modified ST suspension was retested. The process included a subjective vehicle assessment, objective ride and handling tests, on-road shake measurements, and two-post shaker rig measurements.

The studies concluded, and the presenters argue, that while the vehicle carrying the greater unsprung mass at each wheel did display perceptible differences compared with the stock vehicle, those differences were minor and can be mitigated using “normal engineering processes within a product development cycle.”

By fitting the upgraded ST-level suspension to the car replicating one equipped with Protean PD18 in-wheel motors, the vehicle’s handling and on-center tracking were improved back to reference. Overall, the effort conducted by Protean Electric, Lotus Engineering, and Dunamos may help convince skeptics that the addition of 30 kg of unsprung mass per corner will not adversely impact overall vehicle dynamics and can be addressed fairly easily with cost-effective countermeasures.”*

*http://ev.sae.org/article/9493/*

Furthermore, it seems to me if you’re using electric motor to control the vehicle height rather than liquid/air shocks then the unsprung weight wouldn’t matter. Feed a bit more power to the motor as the wheel travels downward in order to maintain the same amount of force between vehicle and wheel, capture that power back as the wheel comes back up.

You’d loose a bit of energy in the transaction but it’s like more than offset by eliminating drive train power loss and by overall weight reduction.

In-hub is very interesting to me. Should make it easy to market 4wd versions and with electronic suspensions should allow for vehicles to rise up on rough roads for clearance and then lower themselves on smooth roads for better mileage and handling.