Is electromagnetic suspension the future? It’s almost here


My biggest disappointment—the technology I covered in a Technologist column I most fervently hoped would never happen—is the Bose electromagnetic suspension, first demonstrated on a bounding Lexus in 2004. Imagine my delight , so when I discovered a completely different kind of electromagnetic suspension, courtesy of Massachusetts-based Indigo Technologies. Instead of using God’s bell clapper to move the suspension, this one takes advantage of individual wheel hub-mounted electric traction motors to smooth out the ride.

Like Amar Bose’s baby, this drive/suspension design was born from the fertile mind and research team of an MIT professor, in this case Ian Hunter. Suspension savvy may run in Hunter’s blood, as he’s a nephew of legendary Kiwi F1 engineer/team owner/Grand Prix winner Bruce McLaren. Hunter devised a method of using an electric motor to simultaneously generate rotational energy and linear motion, each separately controllable.

Electric motors generally consist of a rotating “rotor” and a generally stationary “stator”. Electromagnetic fields generated in the stator winding induce rotation in a magnetized rotor. But what if, Hunter wondered, instead of a fixed stator, you split it in half, pinning each half to a mechanical device that translates the difference in rotation of the two halves into linear motion? Here’s how it works:

Let’s say you need 10 lb-ft of engine torque. The even distribution of electrical energy applied to each half of the stator, say 5 lb-ft to each, results in 10 lb-ft and no linear motion. But if instead you send 3 lb-ft to one and 7 lb-ft to the other, the rotor still gets 10 lb-ft, but the overpowered half of the stator wants to spin in the opposite direction of the rotor , while the underpowered one rotates with the rotor. This counter-rotating motion is what moves this linear actuator. Making it exert force requires more energy input, while the net difference from side to side continues to power the rotor.

Indigo has developed a steerable strut type wedge and an unsteered control arm wedge, each with a coil spring damper unit, disc brake and robotic wheel motor and linear actuator sized to handle itself. fit an 18 inch wheel. As shown, the concept features an axial flux motor with a disc-shaped rotor sandwiched between two stator discs. The motors can generate 30 hp/184 lb-ft of rotational force and over 500 pounds of linear force over the full 7.5-inch range of suspension travel. Energy can be harvested from both linear motion and rotational motion.

For now, the ride control is purely responsive, taking accelerometers into account at every turn, but it’s said to offer a magic carpet ride – quite a feat in a lightweight vehicle carrying so much unsprung weight. The robotic wheels can counteract 1g of body roll, but they won’t get the Indigo Flow electric van off the ground.

The Flow EV targets gig-economy drivers in the Uber, Lyft and Amazon Flex spaces. Small, lightweight robotic wheels packed into the corners free up maximum interior space: the Flow van offers 110 cubic feet, the longer and taller Flow Plus 130. Sizing them to accommodate three passengers or one to two shifts from Amazon Flex. package, they can be small and light enough (Indigo targets a curb weight of around 2,000 pounds and a payload capacity of around 800 pounds) to deliver 250 miles of range from a 40kWh battery . That’s over 200 mpg-e, or about 2 cents/mile in power costs. During the break between three-hour Amazon Flex delivery shifts, Level 2 charging provides enough power to complete another shift.

A central driver’s seat and a single large sliding door on each side allow the driver to safely exit tight spaces on any side that does not face traffic, and the spacious cargo area greatly simplifies access to Amazon Flex packages.

Indigo tells us that four Robotic Wheels should cost no more than the electric powertrain and suspension of an AWD electric vehicle. This, added to the small size of the van and battery, means Indigo is targeting a purchase price of $25,000, with production expected to start in early 2024. But the company is also working with fintech insurer OV Loop to develop a holistic insurance/rental plan that could make the Indigo Flow available to construction workers for 50 cents per mile with no down payment.

This would represent a giant leap for carkind, even if the car itself cannot jump.


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