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Suspension development could reduce military vehicle vibration-induced fatigue

18 December 2012

Recent work by the US Army Research Laboratory (ARL) could see military vehicles becoming less vulnerable to wear and repair from rough and rugged terrain, like potholes, thanks to magnetorheological damping.

ARL's suspension test rig. The advanced suspension unit is shown red in this diagram
ARL's suspension test rig. The advanced suspension unit is shown red in this diagram

ARL is collaborating with the University of Maryland to incorporate fail-safe magnetorheological dampers in military ground vehicles to help them respond best to varying road conditions. It's the same kind of technology used on modern, high-end consumer automobiles; the problem is, it's expensive.

Their study will uncover new ways to retrofit these dampers on wheeled military vehicles to see if they can operate on rugged terrain with less power and a wider range of controllability.

Other defence agencies such as the US Tank Automotive Research Development and Engineering Center are integrating conventional magnetorheological dampers in military vehicles for demonstration purposes.

But ARL's project will compare the fail-safe magnetorheological damper with the conventional damper and study its benefits.

Today's suspension systems are not adaptive and may not work well in reducing vibratory loads on all types of terrains, subjecting occupants to vehicle vibration-induced fatigue during missions. Moreover, target aiming accuracy is impaired due to excessive vehicle vibration on rough terrain.

Conventional magnetorheological dampers stop working if a vehicle loses power, reverting to a typical passive hydraulic shock absorber. This could lead to bottoming out of suspension components and likely loss of vehicle control.

With the fail-safe capability, vehicles won't lose suspension even in case of power failures, thanks to the use of permanent magnets.

The damping force is continuously controlled using a set of electromagnetic coils together with permanent magnets by tuning the current in the electromagnetic coils to vary the viscosity of the magnetorheological fluid.

Thus the damping force can be increased (or decreased) when applying positive (or negative) current to the electromagnetic coils to strengthen (or weaken) the magnetic field strength in the magnetic flux path of the fluid. The device therefore offers bi-directional control.

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