Three displays at CES 2022 featured fresh ideas in the electric motor space worthy of further exploration. Massachusetts startup Indigo Technologies showed off an intriguing wheel-hub motor that manages to simultaneously develop linear actuation for active-suspension at each corner, promising to maximize cargo- and people-space in a tiny car that delivers big-vehicle ride quality. Meanwhile Israel-based delivery and shuttle-van rivals REE Automotive (its Leopard shuttle is pictured above) showed an update on its corner drive module that involves an ultra-compact, high-speed inboard motor concept. Finally, Exro, a Canadian supplier of electric motor controllers, showed a single super-motor in an electric Hummer H1 capable of outmuscling the multiple motors in a Chevy Silverado EV, GMC Hummer EV, Ford F-150 Lightning, Rivian R1T, and even the plaidest of future Tesla Cybertrucks.
Indigo Robotic Wheel
In a nutshell, Indigo’s Robotic Wheel is another drive-and-suspension all-in-one electrified corner concept optimized for electric delivery and shuttle vehicles. But the well-patented (105 and counting) intellectual property involved here is fascinating. It starts by dividing the usually stationary stator half of the electric motor into two halves. The rotating rotor part is still made from a single piece that, in this case, drives a wheel and tire directly. The stator halves are connected to each other and to the bodywork by a mechanism that translates relative rotational motion between the two stator segments into linear motion as they rotate in opposite directions. In the case of the Indigo Flow delivery van’s motors, that linear motion serves to either push the wheel down or pull it up in response to road surface irregularities.
Here’s how it works. Say you’re driving along on a smooth straight road that only requires 10 pound-feet of torque per wheel. The stator halves each get fed enough energy to produce 5 lb-ft, which sums to 10 lb-ft at the rotor. Now, say a wheel starts to drop into a pothole or roll over a bump. By varying the amount of power energizing each half of the stator, one will rotate slightly in the counterclockwise direction while the other rotates slightly in the opposite direction, causing the combining mechanism to generate a linear force in pounds pressing up or down on the body to smooth out the ride while ensuring the net power sent to the rotor remains unchanged at 10 lb-ft, so there’s no torque interruption.
The rotational difference can be induced under power or during regenerative braking, so it can also be used to combat squat and dive, as well as to resist roll—obviating the need for a mechanical (anti-roll bar) connection between corners. This is, to date, the most convincing concept we’ve seen to combat/compensate for the increased un-sprung mass of a wheel-hub motor.
For the Flow van concept, Indigo is employing axial “pancake” motors, with a disk-shaped rotor sandwiched between two stator disks, but the concept has been demonstrated on other motor types and has proven to be agnostic of motor technology. The current prototype has a linear range of motion of 7.5 inches, and we’re told that a motor rated for 192 lb-ft of wheel torque can exert 562 pounds of linear force on the body—at least 150 pounds more than Indigo says it would need to counter the roll forces of a 1g cornering maneuver in the Flow delivery van. (Sadly, that is NOT sufficient force to allow an Indigo Flow van to perform steeplechase jumps like that Lexus with the experimental Bose electromagnetic suspension did in 2005.)
For now, the active suspension system is technically envisioned as reactive, taking inputs from accelerometers on the suspension strut to order its body-stabilizing and ride-compensating forces, but as road-texture sensing technology matures, the Robotic Wheels could be programmed for fully active, predictive ride control.
REE Automotive/AAM 3-in1 Corner
We’ve reported on REE Automotive’s REEboard skateboard platform and REEcorner shuttle and delivery van concept in the past, which prioritized packaging of the entire motor, driveline, and suspension within the general envelope of the typical wheel well. At CES 2022, the company showed off a new corner aimed at slightly heavier-duty applications. Developed in conjunction with American Axle Manufacturing, this fifth-generation REEcorner features a three-in-one drive unit, meaning that in addition to the suspension and brakes, this new REEcorner integrates a motor, gear-reduction transaxle, and all power electronics needed to run the motor. As a result, the new drive unit sits more inboard than the typical wheel housing, but it’s very low profile, requiring only a slight bump in an otherwise flat load floor or slight increase in floor height.
The 6-inch-diameter stator establishes the size of the motor, and some clever engineering and packaging locates the MOSFETs (these silicon-carbide metal-oxide-semiconductor field-effect transistors control the motor’s speed and direction) radially on the end of the motor along with the other controlling electronics, all within that same 6-inch diameter. Scaling the motor up or down for more or less power is a simple matter of changing the number of stator and rotor plates and size of the winding to make the motor longer or shorter. This mini-motor is also designed to be able to spin up to 24,000 rpm—4,000 revs faster than the impressive motors powering the Lucid Air.
The drive unit also features innovation, in that a two-stage 6.77:1 gear reduction keeps four gears in constant mesh, reducing the stresses on any one set at a time. Each REEcorner gets its own lubrication system, complete with oil filter, but they can all share a common glycol cooling system. A central electronic control unit handles integration and arbitration amongst however many driving and steering REEcorners are used.
As displayed at CES each REEcorner drive unit produced 134 hp and 89 lb-ft—that’s 268 hp and 1,205 lb-ft of wheel torque (for comparison with similar hub-motor solutions) in a two-wheel-drive setup, or 536 hp and 2,410 lb-ft at the wheels with four motors. REE has two production customers identified in the Class 4 delivery truck market, with deliveries expected in 2024. REE will produce the REEcorners, while production partners will build the REEboard and bodies and manage final assembly.
Exro Coil Drive Motor Control System
How’d you like an electric Hummer H1 powered by a single 1,270-hp/3,170-lb-ft electric motor? That’d surely hold its own against the coming wave of electric pickups, eh? The H1 fitment is an attention grabber, but this jumbo motor is intended for commercial-vehicle applications. Still, even at 600 pounds, it’s roughly twice the combined weight of the motors in those other trucks, with roughly four-times the output. It caught our attention because it employs a technology reminiscent to one Chorus Mechcon proposed for use driving the nose gear of a Boeing 737 when we first covered it back in 2008. We’re not aware of another highway application of the concept.
Here, the magic is all in the motor controller, which Exro dubs Coil Drive. As with the above mentioned “mesh connected” motor concept, the stator winding gets divided up into more “phases” that can be turned on and off, combined or driven separately. This has the effect of changing the torque characteristics of the motor at different speeds, and so gets described as feeling like an internal virtual “transmission.” It does this by delivering both the low-end starting torque of a parallel-wound DC motor (stator winding in line with rotor winding), then switching to provide the high-end power of a parallel-wound setup. This can help broaden a motor’s overall torque curve by 60 percent while boosting power by up to 150 percent (mainly by sustaining torque to higher rpm).
The motor mounted in the electric Hummer is a production unit from Traktionssysteme Austria GmbH (with which Exro has an agreement to develop commercial motor drive applications). The Coil Drive system that boosts this motor’s potential output involves more silicon in the electronics, which drive up costs, but the technology helps offset these costs by enabling downsizing and/or eliminating a multi-speed transmission. And the extra silicon also pays off in allowing the motor controller to function as a bi-directional onboard charger, and company officials are working to establish it as an AC fast-charger unit as well.
Exro is working with Tier-1 supplier Linamar to get into the EV supply chain, with SEA Electric to integrate Coil Driver into that company’s electric commercial vehicle retrofits, and it’s working on partnerships in the electric motorcycle and side-by-side space as well.
Keyword: 3 Cool New Electric Motor Technologies From CES 2022