Royalty rode in elegant carriages, made comfortable with steel springs. As speeds increased carriage makers (and subsequently automobile manufacturers) added dampers, coil springs and anti sway bars to improve comfort and handling. Some innovative suspensions even incorporated load leveling devices. Underlying all these technologies, spring steel reigned supreme.
The pace of automotive innovation picked up with the introduction of electronics. Manufacturers introduced accelerometers and other sensors, tied them to the system's CAN bus, improved damper technology, and improved control algorithms regulating them. All these innovations were developed in support of spring steel, king of suspension technology.
Perhaps it's time to examine the limitations of that technology, reviewing possible suspension benefits only hinted at by unconventional suspensions in use by a fraction of manufacturers. Such a review may disclose suspension benefits such as enhanced roll over resistance, increased fuel economy, and improved ride and handling for all vehicles, and further benefits for specialized vehicles, such as reduced tire wear for Class 8 trucks, reduced cargo damage for freight trains, and reduced injuries and damage to military vehicles through IED blast attenuation. Still other benefits accrue to the infrastructure in reduced maintenance and repair of both highways and railways through reduced impact loading as vehicles pass over irregularities in their path. The following review hints of a method to achieve these benefits.
The suspension shown in Figure 2 reflects shows gas and oil contained in a double ended cylinder on opposite sides of a floating piston. Equal forces acting on each of the rods create equal pressures in the gas and oil. The floating piston remains centered under these static conditions.
If the floating piston is modified (bottom of Figure 2), it acts as a pressure-balancing valve in a suspension strut. The valve remains centered between reservoir and supply ports as long as the gas and oil pressures are equal on either side of the pressure-balancing valve. If there is a pressure imbalance between the gas and the oil, the pressure-balancing valve is offset toward the lesser pressure, either admitting or releasing oil and bringing the pressure of the oil back into balance with that of the gas. This design is the basis for development of a new suspension platform, and is currently the subject of a Phase II SBIR contract being funded by the Army.
Figure 3 shows the strut discharging or admitting fluid in bounce and rebound (respectively), while maintaining support equal to the weight of the sprung, despite any dynamic load variations caused by cornering or acceleration. The strut's operation is dictated by the relative pressures above and below the pressure-balancing valve at each moment. The strut can continuously compensate for compression or expansion of the gas in the upper section of the strut, effectively de-coupling the vehicle's ride rate from its roll rate.
The King is not likely to be dethroned anytime soon, but this new suspension may provide an heir to the throne, bringing a multitude of additional benefits to the kingdom. Long live the king!