The Dawn of Active Suspensions?

If you want to gauge the trickle down of technology from development to consumer availability, the automotive industry is a good test subject. Huge research budgets, extensive supply networks, cutthroat competition and big name partnerships means car companies maintain appeal by staying on the cutting edge of modern innovation and development.

And the auto industry is certainly one in upheaval. Staggering fuel mandates loom heavily. Aluminum alloys represent the future of automotive materials. Smaller engines are being super- and turbocharged to squeeze every engine rotation out of available fuel. Tesla doesn't plan on being a competitor, but rather a supplier, so other automakers can use their electric powertrains. Now one knows exactly when sensors and CPUs are going to drive our cars, but bets placed for sooner rather than later will surely pay off.

Yet many automotive designs have remained stagnant, sometimes for over a century. Take your average automobile or light truck suspension. With some exceptions, the vast majority of auto suspensions in the past 100 years have either been leaf springs or coil springs. These types of suspensions are known as passive suspensions, simply because they're reactive to different grade levels and road conditions. Passive suspensions represented a major improvement on the suspensions of the 1800s, which were primarily for carriages and low speed vehicles, and consisted of leather belts slung between mounts that insulated the cabin via oscillation. Of course, such designs were unacceptable for automobiles, so early automakers relied on leaf springs (and still do for heavy cars and trucks), the same suspension principle used on ancient Egyptian chariots. In this sense, passive springs are a much, much older suspension technology than what is represented in automobiles. Coil springs couldn't be accurately produced until industrialization, and still weren't implemented in significant numbers until post-World War II. Torsion bar suspensions are primarily used on B-segment European cars, where simplicity and space savings are a primary concern.

So where am I going with all this? Hopefully a new generation of active and semi-active auto suspensions will reinvigorate an exhausted product that is easily improved by modern technology. Automakers are learning how these suspensions can help them in other developments, such as improving gas mileage, and creating a more enjoyable ride experience as well.

Active suspensions have force actuators that can both add and dissipate energy from a vehicle axle, meaning that ride quality and excellent handling isn't a compromise like it is with a passive suspension. Vehicle heights can be adjusted according to speed, improving aerodynamics and therefore gas efficiency. Active suspensions can also eliminate the sway or pitch resulting from vehicle inertia when in a tight corner, braking, or accelerating, which significantly improves vehicle safety and also enhances tire lifespans. Pretty much you would never spill coffee on yourself because of sudden stops or turns during your morning commute.

Of course, just because they've been used sparingly doesn't mean active and semi-active suspensions have been ignored. Instead, their use has been limited for two reasons: additional cost has limited deployment of expensive vehicles, and standard hydraulic suspensions are slow in response but high in power consumption.

One of the more intriguing kinds of active suspensions is the electromagnetic recuperative suspension. By utilizing a normal passive spring, an electromagnetic actuator, control unit and batteries, it reportedly increases ride quality by 60 percent, and also improves safety by eliminating sway and pitch while cornering and braking. Even if electric power to the suspension fails, the passive spring can still handle dynamic loads. Furthermore, some of the power consumed by this can be regenerated by using the motors as generators. Its small package footprint means it can even be retrofitted for many cars, according to Bose. The company best known for stereo equipment has sunk over $100 million in research on an electromagnetic suspension, as a testament to its belief in the system. Bose has even demonstrated bunnyhops with the system.

Magnetorheological dampers are another active type of suspension, but have seen further implementation than electromagnetic recuperative types. In this instance, a shock absorber is filled with magnetorheological fluid and connected to an electromagnet. When the fluid is magnetized, metallic particles align according to field lines to make the fluid stiff. By controlling this stiffness with sensors and a PLC, shock and vibration is isolated from the vehicle chassis. It has been deemed the most advanced suspension control system in the world.

Perhaps the last active suspension worth mentioning is only applicable if some manufacturers implement in-wheel motors, as speculated. It would be Michelin's Active Wheel. Not only is the wheel itself powered by an electric motor, but a separate electric motor controls each wheel's torque distribution, traction and weight distribution. The Active Wheel is perfect for electric or hybrid drivetrains. This design hasn't been incorporated into a production vehicle yet, but some analysts believe an in-wheel motor realization is on the horizon.

Of course, all of this development means nothing if it can't be scaled to an affordable, middle-class targeted vehicle. Even with inflation accounted for, vehicles are getting more expensive due to additional creature comforts and tighter government regulations. Considering that active suspensions can improve MPG, safety, handling and ride quality, there may be a day where this burgeoning technology is an inevitable cost of vehicle ownership. For now though, many of us ride around on a spring that hasn't been improved in 3,000 years.