DARPA - Servovalve active damper program
and
TACOM - Magnetorheological (MR) damper design

 

Although the Hummer (in military parlance, “HMMWV”) is a well-regarded and generally capable off-road vehicle, its performance and mobility is affected by the compromises that had to be made in the stock suspension system. By combining our off-road racing experience with a revolutionary suspension technology, MillenWorks was contracted by the U.S. Army Tank and Armaments Command (TACOM) to develop a robust, computer controlled suspension upgrade for the HMMWV. The long name is MagnetoRheological fluid Optimized Active Damper Suspension. We call it MROADS.

The system is designed around MagnetoRheological fluid, which is a water or oil-based fluid whose viscosity, or shear rate, can be changed by applying to it a magnetic field. When properly engineered, this allows the control of suspension performance in real time with a damper that is inherently less complicated than high performance passive dampers with bypass tubes, valve stacks, or inertial sensing devices.


The MROADS system consists of one MR Fluid computer controlled damper at each of the vehicle’s wheel positions. The active damper suspension is based on the idea of modulating the forces in a damper as a function of sensed variables, such as the vehicle speed, body movements, and position of a particular wheel. Our active damper suspension system is lighter, smaller, less expensive, and uses much less power than a fully active system while providing similar levels of performance.


The MROADS computer-controller damper system automatically optimizes the Hummer’s suspension performance based on vehicle loading and operating conditions, which yield many benefits:

  • Significant (up to 70% on certain terrain) reduction in driver absorbed power
  • Higher mobility speeds over a given terrain
  • Improved tire traction
  • Improved tire life
  • Reduced fatigue loading of vehicle structure and payload
  • Reduced driver, vehicle and payload damage from terrain impacts at speed
  • Improved vehicle stability and handling
  • Improved accuracy during surveillance, targeting, or weapons firing
  • Suspension system prognostics / diagnostics.

The system was designed to facilitate bolt-on retrofitting. Only minor modifications to the Hummer were required for mounting sensing and control hardware, and the original chassis and lower A-arm suspension mounting holes are used to accommodate the MR damper and spring assembly.

The system was tested and tuned in the California desert . With driving feedback from Rod Millen himself, MillenWorks engineers fine-tuned the control system while monitoring the performance improvements and system reliability.

In January of 2003, the MROADS equipped Hummer underwent a battery of tests at the Army’s Yuma Proving Grounds in Arizona, where it went head to head against a Stock Military HMMWV. The grueling tests underlined the performance advantages of the MROADS system , and demonstrated the high reliability of the system, which suffered no failures whatsoever.

Frequently Asked Questions:

1. What’s the difference between an active damper suspension and a fully active suspension?
A fully active system, like the old Lotus hydraulic based system,
requires lots of power and expensive valves or electromechanical actuators.
These systems also can become unstable which can damage the vehicle and hurt
the passengers. An active damper system, requires little power, only that
needed to adjust the dampers in real-time. MR fluid based active dampers
don’t need precision valves or other expensive components. Both systems,
active damper or fully active, can adjust the suspension forces in real-time
and can have similar performance benefits.

2. This system sounds great! Can I buy it for my personal Hummer or modified pickup truck?
Not currently. MROADS will most likely appear on military or government vehicles before it will be available to consumers.


3. Will the MROADS system work on other vehicles?
The MROADS technology and experienced gained from this project are adaptable to a wide range of vehicles. RMSV is working with the government to apply the system to a much larger military vehicle.


4. Isn’t GM already making this type of suspension system?
Through Delphi automotive, GM is marketing a road-going version of an MR suspension on vehicles such as the Corvette. While there are some similarities in how they both work, the RMSV system is designed to handle the much more extreme suspension forces and velocities experienced in off-road travel.


5. Does MillenWorks make the MR fluid?
No. The MR fluid is made by Lord Corporation.


6. What is “absorbed power”?
Absorbed Power is a measure of how vibration affects people. Since
people are sensitive to different types of vibration in different ways, as
compared to other animals or equipment, absorbed power quantifies how each
type of vibration hurts or fatigues people.

7. I have an application that I think would be great for an MR suspension? Can you guys build it?
Please contact us with some details and we’ll let you know.