ARL, Univ. of Maryland team for unconventional studies that could forever change vehicle suspension systems
November 28, 2012
- ARL is taking an unusual approach to incorporating suspension system technology.
- ARL is collaborating with the University of Maryland to incorporate fail-safe magnetorheological dampers onto military ground vehicles to help vehicles respond best to varying road conditions.
The U.S. Army Research Laboratory (ARL) is taking an unusual approach to incorporating suspension system technology, and if its researchers successfully transition their solution from testing to mass production, military vehicles could become less vulnerable to wear and repair from rough and rugged terrain, like potholes.
ARL is collaborating with the University of Maryland to incorporate fail-safe magnetorheological dampers onto military ground vehicles to help vehicles respond best to varying road conditions.
It's the same kind of technology used on modern, high-end consumer automobiles like the Buick Lucerne, luxury Cadillac coups and SUVs, and Chevrolet's Corvette and the Ferrari 458. Problem is: it's expensive.
Their study will uncover new ways to essentially retrofit these dampers on wheeled military vehicles to see if they can operate on rugged terrain with less power and wide range of controllability, said Dr. Muthuvel Murugan, acting team leader for ARL's Vehicle Dynamics team.
Other defense agencies such as the 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 to 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. Hence, Warfighters riding on these types of military vehicles are subjected to vehicle vibration-induced fatigue during missions. Also, the target aiming accuracy is impaired due to excessive vehicle vibration on rough terrain. In addition, the durability of the vehicle is affected increasing cost of maintenance and logistics for the Army," he said.
Murugan said conventional magnetorheological dampers stop working if a vehicle loses power. "All you get is the typical passive hydraulic shock absorber capability," which means Soldiers inside the vehicle would lose vibration isolation resulting in bottoming out of suspension components and likely loss of vehicle control.
With the fail-safe capability, he said vehicles won't lose suspension even in case of power failures; it has built-in capacity to continue for some distance to roll on course because embedded design features with permanent magnets in magnetorheological damper.
These high-end shock absorbers are semi-active devices that are adaptive, controllable and energy-efficient, which make them ideal energy-absorbing solutions for vehicle suspension systems. They can adapt to various road conditions. They're used to dissipate energy in vehicle systems in order to protect vehicle occupants and payloads from injurious vibration, repetitive shock, crash and blast loads, Murugan said.
"Semi-active shock and vibration isolation systems using magnetorheological dampers require minimization of the field-off damping force at high speed," said Dr. Jin Yoo, a research engineer supporting this team at ARL. He has more than ten years of research experience on smart materials, including magnetorheological fluid. Prior to joining ARL, Yoo was a research scientist at University of Maryland conducting DoD sponsored research projects.
"This is because the viscous damping force for high shaft speed becomes excessive for conventional MR dampers. This implies that the controllable dynamic force range is dramatically reduced for widely varying mobility conditions," Murugan said
The innovation of a bi-directional-controllable MR damper, "can produce large dynamic force and dynamic force range, as well as electrical fail-safe performance. The damping force of this MR damper device 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 MR 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 MR fluid, which realizes bi-directional control of this new device. The electrical fail-safe damping force in the event of power loss is provided by the permanent magnets," Murugan said.
Murugan has more than 20 years experience in automotive and rotorcraft vehicle research and engineering development. Before joining ARL, he worked at General Motors in automotive structural crash dynamics, vehicle dynamics, and crash safety restraints development for new vehicle development programs. He has extensive experience working with the National Highway Transport Safety Administration on advanced active safety restraints development projects for future automotive safety rule making initiatives by the U.S. Department of Transportation.